Sensors semiconductor-insulator-electrolyte

Branquinho, R., Veigas, B., Pinto, J.V., Martins, R., Fortunato, E., and Baptista, P.V. (2011) Real-time monitoring of PCR amplification of proto-oncogene c-MYC using a Ta205 electrolyte-insulator-semiconductor sensor. Biosens. Bioelectron., 28, 44-49. 

The concept of light addressable potentiometric sensors (LAPS) was introduced in 1988 [67], LAPS is a semiconductor-based sensor with either electrolyte-insulator-semiconductor (EIS) or metal-insulator-semiconductor (MIS) structure, respectively. Figure 4.13 illustrates a schematic representation of a typical LAPS with EIS structure. A semiconductor substrate (silicone) is covered with an insulator (Si02). A sensing ion-selective layer, for instance, pH-sensitive S3N4, is deposited on top of the insulator. The whole assembly is placed in contact with the sample solution. 

Another example of an Si-based pH sensing device is an electrolyte-insulator-semiconductor (EIS) structure. In a typical EIS sensor, a voltage applied to the semiconductor back gate (Vgate) attracts ions in the electrolyte to the oxide surface. The... 

Design and fabrication of ISFET was described in Ref. [88] The interest in ISFET arises chiefly from their application as pH and ion sensors. A graphical procedure to find PZC from capacitance-voltage characteristics of electrolyte-insulator-semiconductor and metal-insulator-semiconductor structures was discussed [89]. Due to the choice of electrolyte (2 mol dm Na2S04) the PZC values reported in this study (2.5 for Si02, 2.8 for Ta20s and 3-3.4 for Si3N4) are not likely to be the pristine values due to specific adsorption of anions. 

Electrolyte-insulator-semiconductors are the basis for silicon field-effect chemical sensors and include ISFETs/ChemFETs, light-addressable potentiometric sensors (LAPSs) and capacitive sensors. The first ISFET was invented in 1970. ... 

Vlasov YG, Tarantov YA, Bobrov PV (2003) Analytical characteristics and sensitivity mechanisms of electrolyte-insulator-semiconductor system-based chemical sensors - a critical review. Anal Bioanal Chem 376 788-796... 

Also the polysiloxane gel functionalized by sensitive macromolecules a-CD and p CD have been synthesized and used as a receptor for Ion-Sensitive Field Transistors (ISFET) and Electrolyte Insulator Semiconductor (EIS) ions sensors [25]. The samples were characterized by electrochemical measurements in several ionic concentrations in aqueous solution. The role of interfering ions and sensor stability was investigated. The sensor performance sensitivity increases by incorporating of CD receptor in the gel structure. The responses of a-CD-PS/EIS and a-CD-PS/ISFET to Cd ion are similar. These results indicate that sensitivity... 

A constant bias potential is applied across the sensor in order to form a depletion layer at the insulator-semiconductor interface. The depth and capacitance of the depletion layer changes with the surface potential, which is a function of the ion concentration in the electrolytic solution. The variation of the capacitance is read out when the semiconductor substrate is illuminated with a modulated light and the generated photocurrent is measured by means of an external circuit. 

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