Novel Reference Electrode-Insulator-Nitride-Oxide-Semiconductor (RINOS) Structure with Sm<sub>2</sub>O<sub>3</sub> Sensing Membrane for pH-sensor Application

Titanium dioxide (TiO2) thin films were applied as the sensing membrane of an extended-gate field-effect transistor (EGFET) pH sensor. TiO2thin films were deposited by spin coating method and the influences of the spin speed and spin duration on the pH sensing behavior of TiO2thin films were investigated. The spin coated TiO2thin films were connected to commercial metal-oxide-semiconductor field-effect transistor (MOSFET) to form the extended gates and the MOSFET was integrated in a readout interfacing circuit to complete the EGFET pH sensor system. For the spin speed parameter investigation, the highest sensitivity was obtained for the sample spun at 3000 rpm at a fixed spinning time of 60 s, which was 60.3 mV/pH. The sensitivity was further improved to achieve 68 mV/pH with good linearity of 0.9943 when the spin time was 75 s at the speed of 3000 rpm.

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Sensitivity, Noise and Resolution in a BEOL-Modified Foundry-Made ISFET with Miniaturized Reference Electrode for Wearable Point-of-Care Applications

Sensors ◽

10.3390/s21051779 ◽

2021 ◽

Vol 21 (5) ◽

pp. 1779

Author(s):

Francesco Bellando ◽

Leandro Julian Mele ◽

Pierpaolo Palestri ◽

Junrui Zhang ◽

Adrian Mihai Ionescu ◽

...

Keyword(s):

Field Effect Transistors ◽

Point Of Care ◽

Ph Sensor ◽

Reference Electrode ◽

High Sensitivity ◽

Complementary Metal Oxide Semiconductor ◽

Drain Current ◽

Oxide Semiconductor ◽

Noise Characteristics ◽

Strong Inversion

Ion-sensitive field-effect transistors (ISFETs) form a high sensitivity and scalable class of sensors, compatible with advanced complementary metal-oxide semiconductor (CMOS) processes. Despite many previous demonstrations about their merits as low-power integrated sensors, very little is known about their noise characterization when being operated in a liquid gate configuration. The noise characteristics in various regimes of their operation are important to select the most suitable conditions for signal-to-noise ratio (SNR) and power consumption. This work reports systematic DC, transient, and noise characterizations and models of a back-end of line (BEOL)-modified foundry-made ISFET used as pH sensor. The aim is to determine the sensor sensitivity and resolution to pH changes and to calibrate numerical and lumped element models, capable of supporting the interpretation of the experimental findings. The experimental sensitivity is approximately 40 mV/pH with a normalized resolution of 5 mpH per µm2, in agreement with the literature state of the art. Differences in the drain current noise spectra between the ISFET and MOSFET configurations of the same device at low currents (weak inversion) suggest that the chemical noise produced by the random binding/unbinding of the H+ ions on the sensor surface is likely the dominant noise contribution in this regime. In contrast, at high currents (strong inversion), the two configurations provide similar drain noise levels suggesting that the noise originates in the underlying FET rather than in the sensing region.

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Influence of Ti content on sensing performance of LaTixOy sensing membrane based electrolyte-insulator-semiconductor pH sensor

Materials Chemistry and Physics ◽

10.1016/j.matchemphys.2021.124774 ◽

2021 ◽

pp. 124774

Author(s):

Tung-Ming Pan ◽

Prabir Garu ◽

Jim-Long Her

Keyword(s):

Ph Sensor ◽

Sensing Membrane ◽

Ti Content ◽

Sensing Performance

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Titanium Nitride Thin Film Based Low-Redox-Interference Potentiometric pH Sensing Electrodes

Sensors ◽

10.3390/s21010042 ◽

2020 ◽

Vol 21 (1) ◽

pp. 42

Author(s):

Shimrith Paul Shylendra ◽

Wade Lonsdale ◽

Magdalena Wajrak ◽

Mohammad Nur-E-Alam ◽

Kamal Alameh

Keyword(s):

Thin Film ◽

Titanium Nitride ◽

Orange Juice ◽

Ph Sensor ◽

Reference Electrode ◽

Cost Effective ◽

Ph Sensing ◽

Ph Sensors ◽

Potential Shift ◽

Double Junction

In this work, a solid-state potentiometric pH sensor is designed by incorporating a thin film of Radio Frequency Magnetron Sputtered (RFMS) Titanium Nitride (TiN) working electrode and a commercial Ag|AgCl|KCl double junction reference electrode. The sensor shows a linear pH slope of −59.1 mV/pH, R2 = 0.9997, a hysteresis as low as 1.2 mV, and drift below 3.9 mV/h. In addition, the redox interference performance of TiN electrodes is compared with that of Iridium Oxide (IrO2) counterparts. Experimental results show −32 mV potential shift (E0 value) in 1 mM ascorbic acid (reducing agent) for TiN electrodes, and this is significantly lower than the −114 mV potential shift of IrO2 electrodes with sub-Nernstian sensitivity. These results are most encouraging and pave the way towards the development of miniaturized, cost-effective, and robust pH sensors for difficult matrices, such as wine and fresh orange juice.

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Poly Silk Peptide Film PH Sensor Based on Zero Current Potentiometry

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.450-451.554 ◽

2012 ◽

Vol 450-451 ◽

pp. 554-556

Author(s):

Ming Ming Ma ◽

Zhi Tong ◽

Yong Wen

Keyword(s):

Graphite Electrode ◽

Ph Sensor ◽

Reference Electrode ◽

Pencil Graphite Electrode ◽

Solution Ph ◽

Counter Electrodes ◽

System A ◽

Zero Current ◽

In Series ◽

Silk Peptide

A poly silk peptide film pH sensor has been developed using zero current potentiometry system. A poly silk peptide film coated pencil graphite electrode is connected in series between the working and counter electrodes of a potentiostat, and immersed in solution together with a reference electrode. When the solution pH varies, the resulting zero current potentiometry is linear with the values of the solution pH in the range of 1.81 to 11.58. This pH sensor shows high stability, accuracy, selectivity and reproduction.

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