The Function of the Harbormaster for the Security and Safety of Shipping

Shipping safety is very important and is the center of all aspects of the shipping world. The harbormaster as the government at the port has the responsibility to ensure the safety and security of shipping. This research is a normative-legal research using a statute, comparative and conceptual approaches. The results show that the implementation of the safety and security functions of shipping by the harbormaster is carried out in accordance with international law and national law in shipping. Optimizing the harbormaster in carrying out the safety and security functions of shipping as well as carrying out supervision of the maritime affairs of the ship will realize the achievement of safety, security and order in shipping activities.

Introduction
of 2015 and many other laws and regulations that regulate all matters relating to sea traffic, transportation of goods and / or people by sea, navigation and shipping activities as a means of sea transportation, including aspects of security and law enforcement. In carrying out the functions and duties of ship safety and security, the government in this case is the harbormaster given the functions and duties as regulated in Article 208 of Law No. 17 of 2008 that: The harbormaster has the duty to carry out safety and security functions as referred to in Article 207 paragraph (1), namely: Pay attention to shipworthiness, safety, security and order at the port; Attention to orderly ship travel in port waters and shipping traffic; Paying attention to transboundary activities in port waters; Pay attention to salvage activities and underwater work; Pay attention to ship alert activities; Pay attention to scouting; Pay attention to the ups and downs of dangerous goods and hazardous and toxic waste; Pay attention to ship refueling; Pay attention to the orderliness of the embarkation and debarkation of passengers; Pay attention to island dredging and reclamation; Pay attention to the activities of building port facilities for ships; Carry out assistance to search and rescue ship accidents; Leading the pollution control and fire fighting team at the port; and Pay attention to the implementation of marine environmental protection; The inherent aspects of shipping safety include the characteristics of attitudes, values and activities related to the importance of meeting safety and security requirements related to transportation in waters and at ports. Neglecting shipping safety generally results in higher economic and environmental costs, such as reduced production, incurring medical costs, pollution and inefficient energy consumption.
Shipping is a high regulated sector where there are clear regulations regarding the role of each related party in shipping. 1 The existence of marine safety regulations that prioritize third party regulations is a result of the many shipping accidents caused by human errors. At the operational level, the harbormaster, ship owner and skipper are the trident of shipping safety. The three of them have roles and responsibilities as defined in the maritime affairs of the ship, which is explicitly regulated in article 1 paragraph (33) of Law No. 17 of 2008 which explains that shipworthiness is a condition of a ship that meets the requirements of ship security, crew members, cargo, health and welfare of crew and passengers as well as legal status of ships, security management and prevention of ship pollution, management of ship security to navigate certain waters. 2 Shipping is not only about sea transportation, but more generally includes existing facilities and infrastructure, as well as guarantees of safety, security and protection in Indonesia's maritime environment. 3 This is what creates a variety of marine support, routine supervision and maintenance and the need for marine and ship safety guarantees as a guarantee of safety, security and protection in the maritime environment. 1 Sea transportation requires many facilities, such as marine warehouses, sea guides, cargo equipment, tugs and support ships. 2 In addition, the facilities that must be provided for securing port channels, ship lighting, port access points and patrol boats are also not yet available for pioneer ships to guide ships to port docks. 3 The enactment of Law No. 17 of 2008 relating to shipping has undergone many improvements that will improve the function of the porters and safety and security issues on shipping are the main responsibility at the port because the main problem in shipping accidents on shipping is a matter of a person's ability and expertise in carrying out port duties.
The duties of the harbormaster in the field of shipping security and safety according to Indonesian law are as law enforcers in the field of Indonesian shipping safety and security, as head of government at ports or as coordinators of all activities in ports, as supervisors and are responsible for shipping security and safety in Indonesia, and as a shipping document issuer. The responsibility of the harbormaster in shipping security and safety according to Indonesian law is to ensure that the ship is fit for sailing and the risk of sea accidents due to ship unworthiness, overcoming marine pollution, making efforts to prevent and minimize marine pollution and participating in search and rescue of victims in the event of a ship accident when there is a disturbance in shipping. 4 The importance of safety and security issues, as well as all marine transportation activities is the responsibility of the port because one of the main problems in shipping accidents during shipping is the problem of a person's ability and expertise to carry out his duties both in carrying out all duties at the port and in the performance of cooperation or relations with agencies other businesses assigned to supervise shipping and shipping itself. This study aims to analyze the implementation of the harbormaster function in the effort of shipping safety and security.

Methods of Research
This research is a normative-legal research using a statute, comparative and conceptual approaches. 5 Its data will be provided from primary and secondary legal materials. The primary legal materials resulted from some relevant laws and legislation. Those legal material collected are analysed descriptively related to the problems and prescriptively.

Results and Discussion
Major works related to the law of the sea can be traced back to the 1600s. Mare Liberum by Hugo Grotius in 1609 is one of the earliest academic writings on the subject. The book applies the terms 'safety' and 'safe' several times in describing the imagined situation at sea. 6 First, Grotius highlighted how the King of Spain told the Counselor and Viceroy of India to organize a fleet suitable for a particular mission in a certain part of the sea, as well as to select the appropriate command and head for it. 7 In this historic article, conformity is a factor related to safety. Grotius also underlined further that maritime trade between Spain and India is very important to the safety of Spain and therefore cannot be maintained without weapons. 8 The thinking of Grotius led discussions in other major works of international maritime law such as William Welwood with his work, "De Dominio Maris," in 1615 and John Selden with "Mare Clausum Seu de Dominio Maris" in 1635. Overall, this publication suggests that some of the important factors related to maritime safety in the 17th century consisted of at least two sets of factors: the technical element (ship type) and the human element (crew capacity). These works also show that maritime safety is an integral part of nations' strategic thinking, as they compete and try to win wars by ensuring the safety of sea lanes.
Maritime security is implicitly discussed in The Influence of Sea Power upon History 1660-1783, published in 1890 by Alfred Thayer Mahan. Amid an extraordinary recipe for how a country can become a leading maritime nation, the book highlights the need for maritime security to achieve that vision. 9 Interestingly, Mahan distinguished the concept between controllable aspects of maritime safety (such as maritime traffic safety, port safety, safety points in all international waters to ensure shipping operations, naval efficiency, and property safety on board) and those aspects that uncontrolled (such as natural harbor and coastal landscapes, and the potential for monsoons). Mahan's work is one of the leading works of a time when a social science perspective was still dominant in discussions of safety at sea. The way of studying maritime safety changed with the extraordinary technological advances of the early 20th century. The sinking of the unprecedented large-scale passenger ship RMS Titanic in the North Atlantic Ocean in 1912 sparked a more scientific analysis. The main cause of the Titanic accident was the dynamics of pressure on the sea level that brought icebergs to the Titanic's shipping lanes, accompanied by the absence of regulations regarding shipbuilding technology. 1 The initial international response then was the formulation of the first Convention on the Safety of Life at Sea (SOLAS) in the following two years. More than half of the provisions in SOLAS 1914 deal with technical components of shipbuilding, including but not limited to construction, radiotelegraphy, life-saving equipment and fire protection. This marked the start of a science-led paradigm on maritime safety, which was further emphasized by the establishment of the Maritime Safety Committee by the International Maritime Consultative Organization (IMCO, now called IMO) in 1959. At its first session, the committee was mandated to cover four thematic areas, Safety of Life at Sea, International Code of Signals, Measurement of Tonnage, and the Prevention of Pollution by Oil. 2 There are several important international conventions at this time, including: Safety Of Life At Sea (SOLAS 1974) which has also been ratified by Indonesia. The convention has been amended by the 1978 Protocol, in particular concerning safety requirements for tankers. Indonesia has also ratified the convention even though the legislation regarding shipping safety that is still formally valid is the Shipping Regulations and Ordinances based on the 1929 SOLAS Convention. Another important convention is the Convention on the International Regulations for Preventing Collisions at Sea, 1972(COLREG Convention 1972, International Convention on Load Lines, 1966(LOAD LINES Convention 1966 and International Convention on Tonnage Measurement of Ships, 1969(TONNAGE Convention 1969 which have also been ratified by Indonesia. In the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers, 1978(STCW Convention 1978 has recently come into effect. This Convention is seen as a milestone for action to improve safety at sea and prevention of marine pollution and prevention of marine pollution through international standardization of standards and procedures for training, certification and safeguards for seafarers of all categories and levels. The Indonesian government is currently considering ratifying the convention. This is actually something that is urgent so that Indonesian ships visiting other countries implementing the convention do not experience difficulties. Several other conventions include the International Convention for Safe Containers, 1972(CSC Convention 1972 Finding an explicit definition of maritime safety from the available academic literature can be challenging. One of the difficulties is the fact that maritime safety has in many cases and research been taken to be underestimated, as something that is generally understood. Much of the literature considers the concept of maritime safety to be self-explanatory and suggests that further efforts to decipher the concept are unnecessary. Yet in providing a conceptual basis, several works are noteworthy: Spiro and Parfitt discuss the application of cost-benefit analysis to marine safety measures; 3 Hetherington, Flin, and Mears highlight the human element of shipping safety; 4 Panayides noted the importance of maritime policy and research to the maritime industry; 5 and Fenstad, Dahl, and Kongsvik closely examined how ship safety is affected by external actors -ship owners and regulatory authorities. 6 All users of sea transportation in Indonesia in particular and the world in general always prioritize safety and security issues, which are then followed by aspects of affordable costs, speed and timeliness, and aspects of comfort. Preventing marine accidents such as drowning, burning, etc. is a matter related to the safety and security of marine transportation. For the implementation of the improvement of sailing safety, the Directorate General of Sea Transportation has issued policies to prevent shipping accidents, such as making shipping announcements regarding increased safety supervision of passenger ships, announcements about weather conditions in Indonesian waters, such as telegrams regarding readiness for bad weather at sea. 7 Shipping which is part of sea transportation as mandated by Law No. 17 of 2008 is a very strategic part from the perspective of the Indonesian nation, as well as an important means of supporting the goals of the unity and 1 Linkin, M. E. (2007). Icebergs Ahead!: How Weather Doomed The Titanic. Weatherwise, 60 (5), 20-25. 2 Simmonds, K. R. (1963). The Constitution of the Maritime Safety Committee of IMCO. Int'l & Comp. LQ, 12, 56. 3 Spiro, E., & Parfitt, A. (1995). Applying cost-benefit analysis to marine safety measures. Maritime Policy and Management,22(3), 215-223. 4 Hetherington, C., Flin, R., & Mearns, K. (2006). Safety in shipping: The human element. Journal of safety research, 37 (4), 401-411. 5 Panayides, P. M. (2006). Maritime policy, management and research: role and potential. Maritime Policy & Management,33(2), 95-105. 6 (5), 552-568. 7 Kadarisman, M. (2017). Kebijakan keselamatan dan keamanan maritim dalam menunjang sistem transportasi laut. Jurnal Manajemen Transportasi & Logistik,4(2), [177][178][179][180][181][182][183][184][185][186][187][188][189][190][191][192] integrity of the Republic of Indonesia as a maritime country. Shipping or sea transportation, which is a part of transportation that cannot be separated from other parts of transportation means that are able to face future changes, has certain characteristics because it is able to carry out mass transportation that can connect and reach regions through waters so that it has a strong development potential and role , both nationally and internationally, as well as being able to encourage and support national development to improve people's welfare in accordance with the mandate of the Pancasila and the Constitution of 1945. 1 The shipping safety and security system is thus an important factor that must be considered and as a basis and benchmarks for decision making in determining the feasibility of a voyage, both in terms of ship facilities and infrastructure such as navigation systems and the personnel involved. involved in this. The following maritime safety and security are the main policies that must be prioritized in shipping in supporting smooth sea transportation in Indonesia as an archipelagic country. 2 Control over the sea means that the government is obliged to carry out governance in the field of law enforcement at sea, both against the threat of violations, the use of waters and the maintenance and creation of optimal shipping safety. Based on Law No.17 of 1985 for Indonesia by the UN convention, it means that Indonesia has been recognized as an archipelago by the international community.
Indonesia's geographic location, which is located between the continents of Asia and Australia and between the Indian and Pacific Oceans, has placed Indonesia in a strategic position in the economic, political, socio-cultural, and defense and security sectors. In addition, the location and marine resources also make Indonesia very important for countries from various regions. However, this strategic position is not only an opportunity, but also an obstacle for the nation. Indonesia in realizing the ideals of the nation), because besides having a beneficial impact at the same time it can threaten Indonesia's interests, it creates complex problems in the fields of security, justice, economy and national defense.
Sea transportation as one of the transportation capital is regulated in one integrated national transportation unit to realize the provision of transportation services in accordance with the needs and availability of safe, comfortable, orderly and efficient transportation services. To achieve this, the government naturally has an important role to play in supporting the smooth running of shipping, namely by enforcing the law at sea.
One of the efforts in the field of legal supervision at sea is the supervision of ships sailing in Indonesian waters. Ships that meet the seaworthy requirements that can sail in the Indonesian sea. In Article 1 number 33 Law no. 17 of 2008, shipworthiness is a condition of a ship that meets the requirements of ship safety, prevention of water pollution from ships, crew members, cargo lines, cargo, crew welfare and passenger health, legal status of ships, management of security and prevention of ship pollution, and management of security. vessels for navigation in certain waters.
The importance of a sailing approval letter is specifically regulated in Law No. 17 of 2008. Although there are regulations for sailing approval letters, it is not uncommon to find various sea transportation accidents caused by negligence in issuing shipping permits. Safety and security issues as well as shipping activities are the responsibility of the port. One of the main problems in maritime shipping accidents is the problem of a person's ability and expertise in carrying out his or her fatherly duties in issuing shipping certificates, navigation permits, shipping safety and security, as well as all marine transportation activities in Indonesian waters.
The duties and powers of the harbormaster based on the Umdang Law No. 17 of 2008, namely carrying out the functions of shipping safety and security, including implementation, supervision and law enforcement in the field of transportation in waters and ports. and protection of the maritime environment in ports.
Ship safety is the condition of a ship that meets the requirements for material, construction, building, machinery and electricity, stability, construction and auxiliary equipment and radio, ship electronics, which is proven by a certificate after inspection and testing. In accordance with the provisions of laws and regulations relating to Indonesian shipping, the port skipper has the task of carrying out safety and security functions, namely: 1) Overseeing the maritime affairs of the ship, safety, security and order at the port; 2) Overseeing orderly ship traffic in waters, ports and shipping lanes; 3) Overseeing the activity of towing ships; 4) Overseeing the orderliness of the embarkation and debarkation of passengers; 5) Supervise the loading and unloading of dangerous goods and hazardous and toxic waste. Security and safety is the most important thing in transportation, not only in the national scope, but also in the international sphere. In this effort, the government in the maritime sector continues to improve the development of marine navigation and marine transportation. The sea is not only limited to natural resources, but also as a means of communication, meaning that the use of the sea for inter-island, land and intercontinental shipping, both for passenger and goods transportation, must be guaranteed for the security and safety of local and international shipping supported by ship security facilities. such as Shipping Navigation Assistance Facilities (SBNP), ship telecommunications, national navigation vessels which are the responsibility of local governments to implement them. In addition, shipping activities with a wide sea and coastal surface area and increasingly extreme climatic conditions also tend to cause accidents, this is a problem or challenge in the field of shipping safety. All parties involved in shipping safety must anticipate and be prepared for climate change and prepare adequate facilities and infrastructure.
Maritime safety and security, including the safety and security of transportation in waters and ports, as well as protection of the maritime environment, must be carried out carefully by the relevant agencies as stakeholders, 1 in this case it is specifically regulated as the elaboration of the shipping law through the Regulation of the Minister of Manpower, Office of the Harbormaster and Port Authority.
Foreign ships that will enter Indonesian territorial waters are required to follow ship inspection procedures to continue their previous voyages. Port state control is carried out by the Harbormaster Section. The results of the above foreign vessel inspection are divided into: (a) seaworthy; (b) substandart; and (c) unsafe. 2 The follow-up or decision from Seaworthy is to issue a clearance out permit (Permit to leave the port); In substandard circumstances, clarification is required with the ship operator; and unsafe conditions require corrective action and even prevent ships from going to sea. Ships that have been declared seaworthy can sail with their destination or to a special port provided by the government, namely a special port for ocean shipping. If a ship is declared unsafe or unsuitable for shipment, the ship must repair the ship's systems or equipment which have been declared damaged or not seaworthy to perform safety and security functions during the voyage.
According to Article 1 number 33 Law no. 17 of 2008, shipworthiness is a condition of a ship that meets the requirements of ship safety, prevention of water pollution from ships, crew members, cargo lines, loading, crew welfare and passenger health, legal status of ships, management of safety and prevention of pollution from ships, and management safety of ships to sail in certain waters. The feasibility of a ship in accordance with its operational area includes: ship safety, prevention of ship pollution, ship manning, ship loading and unloading routes, crew welfare and health of passengers, legal status of ships, security management and pollution prevention from ships, ship security management. The feasibility of the ship is proven by completing administrative and technical requirements.
Administrative requirements in the form of security certificates such as citizenship certificates, measurement documents, security certificates, shipyards, marine equipment security certificates, radio certificates and certificates held, as well as technical requirements such as supporting equipment for security devices at sea must first be fulfilled so that the ship has a seaworthy status. Maritimeity of ships is closely related to shipping safety. 3 Marine if not assisted by marine safety equipment, the risk of shipping accidents will increase. Ships that are seaworthy are proven by having a Marine Ship Certificate. The Ship Marine Feasibility Certificate issued by the port captain is based on the results of class test data from the Indonesian Classification Bureau (BKI).
The importance of the role of the harbormaster in supervising the maritime nature of the ship is reflected in the Indonesian shipping law related to ship safety. Some things that require the attention of the harbormaster in his supervision are ship material, shipbuilding, shipyard, ship engineering and electricity, ship stability, staging and equipment including auxiliary equipment and radio, and ship electronics. Users of sea transportation services using ships that are not seaworthy can cause losses to the goods being transported so that passengers and crew lose their lives.
To prevent this, the harbormaster performs checks in the form of: a) Annual Inspection, checked every 12 months while floating on the shipyard. b) Major examination, which is carried out every 4 years at the same time as the annual doc. c) Inspection or repair of damage is carried out if someone is damaged which affects the perfection of the ship. d) Additional checks, are carried out if a waiver is required, for example the transportation of passengers, transportation of dangerous cargo and others. Seaworthy conditions must always be maintained, among others by maintaining the in-house crew, marine engine, safety equipment and other aids so that everything is in good condition and ready to use when needed. Article 207 paragraph (2) of Law No. 17 of 2008, states that the harbormaster participates in the search or rescue of sea transportation if the sea transport experiences an accident or disruption during shipping activities. 4 The role of the harbormaster in the field of supervision is very important, this can be seen in the Indonesian shipping law regarding ship safety standards, there are several things that need attention from the harbormaster in his supervision, namely: 1) Ship material 2) Ship building 3) Ship machinery and electricity 4) Stability of the ship 5) Arrangement and equipment including auxiliary equipment and radio 6) Ship electronics The harbormaster is the government at the port appointed by the Minister and has the highest authority to implement and monitor compliance with the provisions of laws and regulations to ensure the safety and security of shipping, as well as coordination of government activities at the port. To ensure the safety of shipping in supporting the smooth movement of ships at sea, competent, capable and competent crew members are required, so that every ship that will sail must be manned with sufficient and suitable crew to carry out its duties. board a ship based on its position by taking into account the size of the ship, ship arrangement and shipping area.
Article 1 point 33 of Law No. 17 of 2008 states that shipworthiness is the condition of the ship that meets the requirements of ship safety, prevention of water pollution from ships, manning, loading lines, cargo, crew welfare and passenger health, legal status of ships, safety management and prevention of pollution from ships, and management safety of ships to sail in certain waters.
Sea transportation is a mode that plays an important role in the Indonesian transportation system. 1 Sea transportation plays a role as a means of realizing an understanding of the archipelago, especially in the context of advancing the unity of the national economy which is considered an inseparable part of the national transportation system. This is because sea transportation is used as a transportation service, both local (Interrinsulair) and overseas (Ocean Going). 2 In addition, sea transportation is considered to have high economic value because it is more effective and efficient than transportation by air. This is because ships have a larger and cheaper transport capacity.
In order for the activities referred to above to be carried out properly, it is necessary to have a good supervisory role for passengers. This is of course a concern for the harbormaster, considering that they are the authorities at the port who must play an active role in maximizing their authority, especially in monitoring activities of passengers at the port. However, the reality found in the field is that there are still people who do not fully feel comfortable when they want to travel by boat. The reason that is often cited by passengers is because of the inaccuracy of the supervision activities carried out by the harbormaster officer.
The enactment of Law No. 17 of 2008 has undergone many improvements that have led to an increase in the portability function. The issue of safety, security and order in shipping is the main responsibility, because one of the problems with the number of victims of sea transportation users is the lack of competence and understanding of a person in carrying out his harbormaster duties. Therefore, anyone who carries out the task of patience must fully understand every task that must be carried out.
According to Law No. 17 of 2008 Article 207 paragraph (1), states that the harbormaster carries out the safety and security functions of shipping which include implementation, supervision and law enforcement in the field of transportation in waters, ports, and protection of the maritime environment at ports.
In order to support the achievement of national development goals, shipping is a very decisive element in the smooth running of sea transportation, as regulated in Law No. 17 of 2008. Incompatibility in handling sea transportation systems and problems, as well as an imbalance of attention to shipping safety issues, can hamper the provision of transportation services throughout Indonesia.

Conclusion
The implementation of the safety and security function of shipping by the harbormaster is carried out in accordance with international law and national law in shipping. Optimizing the harbormaster in carrying out the safety and security functions of shipping as well as carrying out supervision of the ship's maritime affairs will realize the achievement of safety, security and order in shipping activities.


extfieldsofstudy:
Computer Science
Medicine

text:
Comprehensive Analytical Modelling of an Absolute pH Sensor

In this work, we present a comprehensive analytical model and results for an absolute pH sensor. Our work aims to address critical scientific issues such as: (1) the impact of the oxide degradation (sensing interface deterioration) on the sensor’s performance and (2) how to achieve a measurement of the absolute ion activity. The methods described here are based on analytical equations which we have derived and implemented in MATLAB code to execute the numerical experiments. The main results of our work show that the depletion width of the sensors is strongly influenced by the pH and the variations of the same depletion width as a function of the pH is significantly smaller for hafnium dioxide in comparison to silicon dioxide. We propose a method to determine the absolute pH using a dual capacitance system, which can be mapped to unequivocally determine the acidity. We compare the impact of degradation in two materials: SiO2 and HfO2, and we illustrate the acidity determination with the functioning of a dual device with SiO2.

Introduction
Ion-Sensitive Field Effect Transistors (ISFETs) [1][2][3] are devices that measure acidity, which offer the best accuracy and miniaturisation. They employ semiconductor fabrication techniques that lower the cost per sensor while providing a high level of sophistication by the integration of the sensors with metal-oxide-semiconductor (MOS) circuits and microfluidics [4,5]. ISFETs transduce the ion activity in the solvent by a capacitance effect that measures the associate charge. Ions are adsorbed from the electrolyte depending on the bulk concentration and the affinity of the material interface. The final signal is formed with the contribution of the charged particles in solution that react forming the double layer capacitance [6][7][8]. There are numerous applications of ISFETs described in the literature ranging from sweat biomarker sensors, physiological measurements, to monitoring the enzymatic activity of polymerase to assist DNA sequencing [9][10][11][12].
Regardless of the impressive progress, these devices have triggered a serious limitation known to anyone using ISFETs, which is that they require continuous re-calibration. ISFETs show an instability that can be manifested in the drift of the threshold voltage or the output current used to transduce the acidity/basicity [13][14][15]. This effect limits the applications that require accurate monitoring of the pH during periods lasting hours as well as the miniaturisation of highly multiplexed devices. As a result of the drift, ISFETs require compensation strategies based on calculations or using reference devices that require extra resources.
At the origin of the drift, there is an irreversible chemical degradation of the dielectric barrier responsible for the change in capacitance. There are several explanations pro-posed for this effect that involve the migration of charges into the oxide materials [16][17][18][19] that decreases the dielectric constant of the affected region [20]. When possible, the re-calibrations are achieved using external reference buffers with known acidity. More sophisticated systems make use of an internal generation of acid that performs a titration curve [21,22]. Finally, there are models that propose to predict the degradation of the capacitance [18,20,23,24]. However, all of the above methods require experiment interruptions or can be sensitive to drastic changes in the ambient conditions. Most of the ongoing work focuses on the stability and material properties of different oxides to enhance the IS-FET performance but the operation of a FET device may be affected due to several process parameters that may make the results less reliable. Here, we present a detailed methodology to enhance the sensor reliability by aiming to get accurate values irrespective of the interacting oxide or FET operation.
In this paper, we propose a system for the absolute measurement of pH by simultaneously using two devices exposed to the same conditions and configured in a way that makes it possible to parameterize a synchronized response. We provide an analytical framework equivalent to an experimental mapping of the simultaneous current of two sensors that are used to describe the system and the methods that can determine the absolute pH irrespective of the experimental conditions. Our system improves the state-of-the-art by reducing the need of continuous calibrations and solving the problem of drift. The derivation of our analytical model is applied to protons, but it can be extended to correct the detection of any other ions that are selectively adsorbed and which suffer from the drift in the current.
The structure of this paper is as follows: the model to include the degradation region in the oxide capacitance is described in Section 2.1 followed by the equations to compute the depletion width. To describe experimental conditions, we applied the system to a high aspect ratio FinFET which enhances the sensitivity and reliability by a 3D gating while increasing the total surface area (Section 2.2). Section 3 outlines the main results and their discussion, including a meticulous analysis of the impact of degradation region on the depletion width and current as a function of the pH for ideal biosensors with two different oxides (Section 3.1) and non-ideal biosensors with SiO 2 (Section 3.3). Finally, conclusions are drawn in Section 4.

Oxide Capacitance
The migration of ions from the electrolyte into the dielectric is observed experimentally as a decrease of the capacitance resulting from the irreversible chemical transformation of a layer of the original material. The ions diffuse down to an effective depth that in some cases can be calculated for given experimental conditions [20,25]. The degraded material experiences a decrease of the dielectric constant which in some materials like Al 2 O 3 reaches values of 20% of the original one [20]. The typical penetration depths of ions account for several nanometers in the span of hours depending on experimental conditions that include the pH of the electrolyte, the temperature and the ionic strength. In steady-state conditions, the degradation often leads to a fast transition and a complete failure of the device when leakage currents appear between the electrolyte and the semiconductor channel.
To simulate the degradation, both the effective dielectric constant and penetration depth can be adjusted phenomenologically to match the capacitance with several combinations that can provide a successful description of the sensor behaviour before the avalanche of leakage currents makes the device fail. In our model, we have modelled the degradation with a reduction to an arbitrary dielectric constant with a value 20% of the original one. The degraded region is associated with a corresponding effective penetration depth of the ions of x that is used to parameterize the degradation. To determine the absolute pH, we will consider two ISFET devices with different thickness t ox1 and t ox2 of the dielectric barrier, subjected to the same experimental conditions and thus, with the same penetration of the effective degradation x on both of devices. Figure 1a shows sections of the interface between the electrolyte and the silicon channel using our model for two cases corresponding to device couples of SiO 2 and HfO 2 , respectively. The dielectric barrier in each device can be considered to be made of two materials in series. The first material in contact with the electrolyte accounts for the degraded region with the adopted effective dielectric constant 20% of the original material and the total effective thickness x corresponding to the penetration of the degradation. The second material has the dielectric properties of the original material (SiO 2 or HfO 2 ) with a total thickness of (t ox1 − x) or (t ox2 − x) for the first and the second device or each sensor couple that will be used to determine the pH. Underlying the non-degraded dielectric in each device, there is the silicon channel as shown in gray in the schemes of Figure 1. Each sensor of absolute pH could consist of more than two of these devices which would be redundant but could help in improving precision. However, for simplicity in this work, we have considered only the use of two devices to determine the absolute pH. We also consider that all the devices with SiO 2 or HfO 2 dielectric barriers will have the same configurations (silicon dimensions, doping, length, etc.) except for the oxide thickness (t ox1 = 5 nm and t ox2 = 10 nm). For practical reasons, in the simulations of this work, we have considered a maximum penetration of ions degrading the oxide of 3 nm. We have also considered in our configuration a common reference electrode for both devices. (a) Schematic representation that shows how the oxide capacitance is modelled considering a degraded region. Two different couple of devices are described in the diagrams including the combinations for two different oxide materials in the dielectric region. For each device couple, we have considered two oxide thicknesses: (blue) t ox1 = 5 nm and SiO 2 , (green) t ox2 = 10 nm and SiO 2 , (red) t ox1 = 5 nm and HfO 2 , and (magenta) t ox2 = 10 nm and HfO 2 . This color notation to identify each device has been kept the same throughout the whole paper. (b) Total capacitance vs. degradation using the penetration depth of the degrading charges as a parameter of the degradation. (c) Schematic of the energy band alignment along one interface in a generic ISFET sensor.
For each device, the total oxide capacitance (C ox ) is calculated as two capacitances in series including a capacitance without any degradation (C 1 ox ) and another one with the degradation (C 2 ox ): where ε 1 r is the relative dielectric constant of the original material, ε 2 r is the relative dielectric constant of the degraded region material and ε 0 is the vacuum dielectric constant.
Accordingly, the total oxide capacitance for each sensor has been calculated from Equation (1): where the index i has been added to the total capacitance to determine ox 1 or ox 2 referring to the devices with the original dielectric of 5 nm or 10 nm, respectively. Figure 1b shows the oxide capacitance calculated using Equation (2) as a function of the degraded region x, for the sensor interfaces with both thicknesses and materials. The observed behaviour corresponds to the decrease of the capacitance with increasing degradation depth x, which is equivalent to what observed in other works [25]. Regarding the total change in the oxide capacitance in the degradation range studied, it is much more pronounced for HfO 2 than for SiO 2 . This is due to the higher dielectric constant ε r of HfO 2 in comparison to the one of SiO 2 (23.4 and 3.9, respectively [26]). Comparing the devices within the same material, as expected, the total variation of the capacitance is more pronounced for the configurations with 5 nm oxide thickness with respect to the thicker oxides of 10 nm, as the degraded region represents a larger part of the total dielectric thickness. Overall, it can be concluded that the HfO 2 capacitance shows larger susceptibility to the degradation and the variations in the thickness due to the diffusion process when it is compared to the SiO 2 .

Calculation of the Field Effect in the Semiconductor Channel
To calculate the effect of the adsorbed charges on the device's current, we consider the energy band diagram in the direction perpendicular to the surface of the oxide shown in Figure 1c. The model does not take into account the possible differences in the chemical potential between the semiconductor and the electrolyte; charges accumulated on the interface between the silicon and the dielectric barrier or phenomenon like the degradation of the reference electrode. When the semiconductor and the electrolyte are connected through a reference electrode and a gate voltage is applied between the two, it is possible to set the relation between the different potentials: where Ψ 0 is the oxide-electrolyte interface potential, Ψ S is the oxide-silicon interface potential, V ox is the potential drop across the oxide and V G is the external bias at the backgate. The adsorption of protons in the oxide builds the potential Ψ 0 , which is zero at the pH of point of zero charge (pH pzc ) where the adsorption and desorption processes are in equilibrium and which can be calculated from their proton affinities pK a and pK b (pH pzc = pK a +pK b 2 ). This potential has a Nerstian response which has been well described in literature [6]: where k B , T, and q are the Boltzmann constant, the temperature, and the electron charge, respectively. The sensitivity parameter α depends on the chemical buffering capacity of the dielectric surface in contact with the electrolyte and the response of the ions in solution that will create the double layer capacitance. Often α is considered only in the linear range of the sensor, and in the ideal case it can be approximated by 1, showing the theoretical maximum variation (slope) of the surface potential with respect to the pH ( ∂Ψ 0 ∂pH = −2.3 k B T q ). To consider the chemical response of the biosensor (non-ideal sensor), α can be calculated making use of an iterative method with Ψ 0 making use of the dissociation model and Gouy-Chapman-Stern theory [6,7]. This more realistic assumption has been taken into account in our analytic model in Section 3.3. In this method, the sensitive parameter is calculated making use of the diffusion capacitance (C di f f ), which depends on the electrolyte properties (considering the double layer and the Stern capacitances), and the intrinsic buffering capacitance of the dielectric (β di f f ), which depends on the number of binding sites on the sensing surface N s and their corresponding proton affinities pK a and pK b : Ψ 0 in Equation (4) changes relative to the pH at pH pzc , i.e. the acidity in the electrolyte at which the equilibrium of protonated and deprotonated species in the surface accounts for neutrality. The conduction band-bending at this pH pzc depends only on the chemical equilibrium at the interface between the dielectric and the semiconductor interface, which is accounted by the flat band potential (V f b ). It is always possible normalization of the device current at pH pzc to account for the band bending due to V f b . At pH = pH pzc , Ψ 0 will be equilibrated in the semiconductor channel by the mobile charge carriers that will migrate and generate a potential within the semiconductor (Ψ S ).
The term V ox in Equation (3) accounts for the energy accumulated across the dielectric barrier. It can be expressed using the charge in the semiconductor side and considering a planar condenser: where C ox is the area capacitance of the dielectric barrier (typically a metal oxide) described in Section 2.1, q is the elementary charge, N A is the density of dopants in the semiconductor and W D is the region in the semiconductor channel depleted from carriers shown in Figure 1c in darker grey color. W D can be derived solving the Poisson equation for Ψ S with a planar configuration: where ε s is relative dielectric constant of the semiconductor. We have replaced ε s ε 0 =ε Si as p-type doped Silicon is used as a semiconductor channel for this work. Note that W D changes the region populated with carriers and thus can modulate the conductivity of the FET channel. Combining Equations (3), (6) and (7), we have the following dependence: In Equation (8), W D changes with respect to the pH through the dependence of Ψ 0 with the acidity expressed in Equation (4) and so it is possible to get a final expression for W D as a function of the pH: A drift in the current will be observed due to the dependence of W D with the degradation of the different parameters. In particular, the parameters from Equation (9) which can be responsible for the drift are: (i) the changes in the dielectric material and thus in C ox due to the possible penetration of ions or modifications of the dielectric (Section 2.1); and (ii) the changes in the sensitivity (α) of the material, mainly due to the modifications in β di f f because of the degradation of the surface with absorbed molecules that change the number of sites (N S ) for the binding of protons. In this work, the sensitivity has been calculated assuming the ideal sensor (in order to equally compare the oxides) and making use of an iterative method with respect to Ψ 0 to consider the real sensor. Accordingly, we have focused on studying the impact of different penetration of ions in C ox .

Impact of the Dielectric Degradation on the Depletion Width of Different Materials
Based on the analytical model described above, we have simulated the four devices detailed in Section 2.1 grouped in couples having two thicknesses (5 nm and 10 nm) for each material (SiO 2 or HfO 2 ). We have calculated the effect of the degradation in W D as a function of the pH. As a first step, to simplify the study of the drift from other effects like the combination of the chemical affinity with the changes in the electrolyte, we have considered the case with ideal sensitivity (α = 1).
We used Equation (9) to calculate the parameters of the semiconductor channel, considering a desirable dynamic range from 2 to 12. Thus, considering a p-doped semiconductor channel that is going to be depleted in acidic conditions, we calculated a bias external voltage V G necessary to have full conductivity (W D = 0 nm) at pH = 12, and calculated the value for both oxide materials. N A was chosen to have a depletion region of W D = 100 nm at pH = pH pzc considering the devices with t ox1 = 5 nm. Figure 2 shows W D vs. pH for the interfaces described in figure 1 using the designated colour codes. A tone scale convention from darker to a lighter colour for increasing x has been added and will be maintained hereafter. As expected, W D decreases with pH in all the devices as a result of the effect of the adsorbed protons. Comparing SiO 2 and HfO 2 , the latter has a larger variation across the pH dynamic range due to the higher dielectric constant. The impact of the drift caused by the degradation on the pH determination by each of the devices is clearly observed in these graphics, as for a single depletion width, there are a broad number of possible pH values corresponding to different states of degradation in the material. For instance, if the constant W D = 60 nm is considered (solid orange line in Figure 2), the pH uncertainty between the cases of no degradation (x = 0 nm) and the maximum degradation considered (x = 3 nm) are ∆pH = 3.15 and ∆pH = 3.30 for the SiO 2 dielectric with t ox1 = 5 nm and t ox2 = 10 nm, respectively; whereas the uncertainty is dramatically reduced to ∆pH = 0.30 and ∆pH = 0.31 for the HfO 2 dielectric with t ox1 = 5 nm and t ox2 = 10 nm, respectively. In both cases, ∆pH is slightly higher for the device with t ox1 = 10 nm.
On the other side, as considering Figure 1b, HfO 2 devices can offer a better pH resolution as the current range of pH values possible relative to the total current variation in the dynamic range, is much more restricted than for SiO 2 . In addition, even if it is not taken into account by these simulations, the chemical stability of HfO 2 largely exceeds the one of SiO 2 , and thus is less prone to ion penetration which makes that the degradation occurs in longer time periods. Elseways, SiO 2 has proportionally a larger variation of W D as the degradation increases. In order to resolve the absolute pH, we intend to determine the degradation considering the current from a dual device composed of the two sensors with one of the two materials that we had calculated. In this sense, SiO 2 may have the advantage to determine an absolute pH as it provides proportionally larger current contrasts within a given pH range.

Determination of Absolute pH from Current Acquisition in FET Sensors
To illustrate the determination of pH in a case scenario, we used our model to calculate the response of a pair of sensors with the geometry of a high aspect ratio FinFET shown in Figure 3a. This ISFET geometry has been recently proposed by us as a robust and advanced design for a biosensor [27]. Similarly to single Silicon-Nanowire (SiNW), this geometry offers a three-dimensional direct gating which is advantageous with respect to typical planar devices or extended gates. Respect to the nanowires (NWs), the high aspect ratio FinFETs can also improve: (i) the reproducibility of the sensitivity for ion sensing (pH), (ii) the total signal, and (iii) the linearity of the current response. Moreover, high aspect ratio FinFETs have better linearity and a smaller footprint if compared to NW arrays. Due to the planar configuration of the conduction channel, the influence of small defects in pH sensing is localised and negligible for the sensor signal if compared to their influence in nanoscale SiNWs. For our work, we have chosen the device dimensions similar to the one shown in Figure 3a, where the width W was 200 nm, the height h was 2 µm and the length L was 10 µm. For a given FinFET, W D can be related to the measured current depending on the geometry of the sensor considering that the size of the channel is diminished across the cross-sectional area by W D in all the directions perpendicular to the surfaces in contact with the electrolyte, and then the total current (I SD ) can be calculated as: where σ, A, and L are the conductivity (material property), the cross-section, and the length of the silicon channel , respectively. At the point of zero charge, A coincides with the geometrical dimensions of the FinFET channel (A = W × h) as pH increases In this way, W D is connected to the experimental data using the original geometrical cross-section and the actual resistance of the channel (ρ = 1/σ). Given the large aspect ratio, we have considered h >> W D and thus we have approximated as A = (W − 2W D ) × (h). This possibility to neglect the depletion width in one direction, is indeed the origin of the higher linearity of the high aspect ratio FinFET respect to NWs described in our works [27,28]. Figure 3a shows two SEM pictures from different perspectives of a typical high aspect ratio FinFETs in which we have included schematics showing the electrical connections and the geometrical parameters W, h and L. Figure 3b shows I SD vs. pH for the pair of devices with silica dielectric at three different degradation points (x = 0.5 nm, x = 1.5 nm and x = 2.5 nm shown in darker to lighter colours and using solid blue lines for the thinner sensor and green dashed lines for the thicker sensor). We illustrate that at an arbitrary pH, the acidity can be unequivocally determined using the current values that intersect for example the orange lines in Figure 3b-d that mark a constant pH for values 3 and 10. For each of these pH values and for each state of degradation (x), Figure 3b provides a pair of current values that will be observed on the pair of sensors at the intersection with the indicated orange lines with each of the curves respective to each degradation x. For each sensor alone, there are several combinations of pH vs. degradation x that provide such currents values, but only at one point, a pair of currents converge with the same pH and degradation x. Figure 3d shows the equivalent situation for pH 10.
Both Figures 2 and 3 show that at more basic pH values, the differences in signal between devices of the same material becomes smaller, and thus discriminating the value of the currents for each state of degradation becomes more difficult depending on the values of the noise signal. By this effect, the determination of pH is also more affected by the noise signal at a more basic pH as the acidity has not acted on the surface potential that builds the depletion width W D . This becomes also apparent comparing the range of pH variation for a given current in Figure 3c,d. The range of pH in the degradation span of our studies for each current is nearly three times larger for the pair of current values acquired at pH 3 ( Figure 3c) than for the ones at pH 10 ( Figure 3d), showing that the degradation can depend less in the measuring error in the first case. It is to be noted, that the current map calculations shown in Figure 3 using our simultaneous of current vs. pH, are equivalent to an experimental-mapping in a pair of devices with the same fabrication parameters except for oxide thickness, and where the simultaneous current response would be mapped during the degradation of the oxide. In such a case, we would bet a current map equivalent to Figure 3b. Given the broader response of SiO 2 to the degradation, it would require less precision on the determination of the current to obtain a match in the current response to a single pH compared to materials with less change with degradation, as for example the case of HfO 2 . However, the lifetime and the variability of the sensor over time would still be beneficial for the material with higher chemical stability and dielectric constant.

Implementation of the Proton Affinity on the Sensor Response for Non-Linear Sensitivities
The simplification of ideal sensitivity α = 1 predicts an excessive sensitivity and fails to describe the effect of saturation of proton adsorption that occurs at acidic concentrations. Materials like SiO 2 decrease in α due to the saturation of the silanol groups accepting protons. In this section, we are presenting results calculating the chemical response of the sensor to describe the best way to operate these devices. To include the chemical sensitivity of the materials and the effects of the electrolyte, it is necessary to include the values of β di f f and C di f f . The buffering capacitance is calculated from the site-binding model: where a H s is the surface proton activity that depends on the bulk pH and on the surface potential. C di f f can be estimated with the Gouy-Chapman-Stern approximation. It is calculated as the Stern capacitance (C Stern ) in series with the double layer capacitance (C DL ). C Stern = 0.8 F m 2 has been considered in this work in order to consider a realistic behaviour of an ISFET [6]. C DL is calculated by: where ε W is the electrolyte permittivity, I 0 is the ion concentration in mol/L, and N avo is the Avogadro constant.
As β di f f and C di f f depend on the surface potential α and Ψ 0 are computed in a self-consistent loop described above. Figure 4 shows the relationship between α, Ψ 0 and pH. The model is able to reproduce the saturation of the surface potential observed in our previous experiments [27][28][29]. At pH = 2, which is the point of zero charge for SiO 2 , α has its minimum value. The origin of the surface potential Ψ 0 is also set equal to 0 at pH 2. Figure 4 shows that with increasing of the pH, the value of α becomes close to 1.0 (α must have value between 0 and 1) and the surface potential Ψ 0 increases to a higher negative value. As the acidity is increased, the decrease in α results in the saturation of change in Ψ 0 . It is also to be noted, that contrary to what is assumed in most cases, the behaviour of Ψ 0 is not linear through the pH range, and that has singularities due to the interplay of proton affinities with the double-layer capacitance.  Figure 5 shows I SD vs. pH for a device couple of SiO 2 with corrected α. As in the case of the ideal sensitivity, the current values in both devices converge to the maximum at basic conditions due to the vanishing W D . Contrary, when the pH is very acidic (pH = 2 or 3), there is a larger drift of the current values with x. The effect of the drift is even larger for the device with t ox1 in comparison to the t ox2 . This is expected due to the larger proportion of degraded material in the device with oxide thickness equals to 5 nm. Another interesting point is that both devices have almost identical current profile for all pH values at maximum degradation of 3 nm (I SD vs. pH curves with lighter colours). Hence, it seems that once the degraded region of the oxide dominates the contribution of the capacitance. The effects of the saturation of the sensitivity α are also observed in the acidic range for both currents simulated in Figure 5 as the variation of I SD vs. pH decreases as the pH becomes more acidic. This loss of sensitivity affects also the determination of pH, as for a given noise signal, more pH values will fall within the range of error. However, this is a property of the material observed in the saturation of the surface potential in Figure 4 which cannot be resolved with a different operation mode.
The lines of constant I SD at 20% of the total conductance (I SD = 0.2 µA) are indicated as horizontal orange lines in Figure 5. It can be noticed, that the pH uncertainty associated to that measurement is much greater for the device with thinner oxide.

Optimisation of pH Determination Using a I SD Follower in One of the Sensors
The current response obtained in Figure 5a,b can be used to reproduce the plan of action described at the end of Section 3.2 to obtain the absolute pH. However, using a constant gate voltage is detrimental to the accuracy at more basic pH values due to the similar values between currents at different x because of the small values of W D . The traditional method to measure the acidity follows the surface potential Ψ 0 by compensating with a voltage bias applied between the channel and the reference electrode to maintain a constant current, usually closed to one obtained with the threshold voltage of the transistor (maximum W D ), but not too low as to increase the signal to noise ratio. Figure 6a,b show the calculation of the gate voltage correction to maintain a current of 0.2 µA (equivalent to a W D of 80 % of the width of the sensor) as a function of pH and for all the states of degradation within the range of our study for the devices with thinner and thicker dielectrics, respectively. The different curves of V G vs. pH for each state of degradation are parallel to each other, showing an opposite behaviour to Ψ 0 (shown in Figure 4) to compensate the charge accumulated due to the pH.
In order to use Figure 6a,b as a map of values to determine the pH, we have to take into consideration that there is only a common reference electrode in the system. Consequently, only one of the devices can be kept at a constant current I DS . Here, we have arbitrarily chosen to maintain constant the device with the smaller oxide thickness, and use the map in Figure 6a corresponding to a particular pH and state of degradation, while using the obtained values of V G and parameter of degradation x to calculate the current that corresponds in the second device. Figure 6c,d show the possible values of pH vs. degradation that could be obtained at the values mapped for pH 3 and 10, respectively, for both sensors shown in blue and green for the 5 nm and 10 nm sensors, respectively. We have extracted the values of V G and current of the second sensor obtained at the levels of degradation of 0.5 nm, 1.5 nm and 2.5 nm. It can be observed that equally to the method of the current, for each pair of devices, there is a single point that determines the pH and the parameter of degradation. Comparing the slopes obtained in the pH determination using the current output Figure 3c,d with the ones obtained with the mapping of V G and the current of the second sensor in Figure 6c,d, we can notice that the later have a steeper slope. This signals also the better determination as determine range of degradation corresponds to a shorter range of pH with the best precision acquired in Figure 6c of the determination only with the current. Thus, using current as the mapping parameter for an unknown variable "oxide degradation" and controlled variable "operating bias", we were able to accurately determine the pH value with the help of two similar devices with different oxide thickness. and two different non-ideal biosensors which main difference is the oxide thickness (t ox1 = 5 nm and t ox2 = 10 nm). The V G has been calculated using Equation (3) considering the W D given by Equation (9) with three degraded regions in the oxide (x = 0.5 nm, x = 1.5 nm, and x = 2.5 nm) and an initial (c) pH = 3 and (d) pH = 10. The solid orange line represents the constant V G in which the curves for both devices cross. In all the figures (a-d), α is self-consistently computed using the iterative method as shown in Figure 4.

Conclusions
In this paper, we have developed an analytical model to calculate the surface potential and the current response of ISFETs to pH. We have implemented the effect of the degradation at the dielectric barrier that induces the current drift. The derived model used a capacitance representing the degraded region which is adjusted with a phenomenological effective dielectric constant and depth connected in series with the capacitance of the rest of non-degraded material with the original properties. We calculated the response of the degradation of the capacitance for two materials, SiO 2 and HfO 2 as examples of low and high dielectric constants, respectively. The relative effect of the degradation is higher for materials with lower dielectric strength. Further, without any correction, the materials with a higher dielectric constant have less uncertainty of the measured pH.
Using the modification of the capacitance with degradation, we propose a method to determine the absolute pH using a mapping of dual sensor response. In our paper, we have used a mapping with calculations equivalent to a mapping that would be produced experimentally with reproducible devices. To simulate the effects of the chemical response of the materials, we have implemented the site-binding model interacting with stern and double layer capacitances. This model does not take into account the modification of binding sites at the interface of the dielectric and the electrolyte. We have shown that using a common reference electrode at constant voltage, the current values are less accurate to determine the pH at basic pH where there is less action of the acid and less depleted region in the semiconductor. This effect can be partially corrected using the voltage of the reference electrode as a current follower for one of the devices. However, in the case of materials like SiO 2 , the effect of site-binding saturation at acidic pH also causes a decrease in the sensitivity, which affects also the possibility to determine the absolute pH.
In summary, we have shown a method to determine the absolute pH using dual measurements from two sensors, which can be a breakthrough for the applications of ISFET in physiological monitoring, or quantification of ion activity.