Graphene Channel Liquid Container Field Effect Transistor as pH Sensor

Graphene channel liquid container field effect transistor pH sensor with interdigital microtrench for liquid ion testing is presented. Growth morphology and pH sensing property of continuous few-layer graphene (FLG) and quasi-continuous monolayer graphene (MG) channels are compared. The experiment results show that the source-to-drain current of the graphene channel FET has a significant and fast response after adsorption of the measured molecule and ion at the room temperature; at the same time, the FLG response time is less than 4 s. The resolution of MG (0.01) on pH value is one order of magnitude higher than that of FLG (0.1). The reason is that with fewer defects, the MG is more likely to adsorb measured molecule and ion, and the molecules and ions can make the transport property change. The output sensitivities of MG are from 34.5% to 57.4% when the pH value is between 7 and 8, while sensitivity of FLG is 4.75% when thepH=7. The sensor fabrication combines traditional silicon technique and flexible electronic technology and provides an easy way to develop graphene-based electrolyte gas sensor or even biological sensors.

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Spin Speed and Duration Dependence of TiO2Thin Films pH Sensing Behavior

Journal of Sensors ◽

10.1155/2016/9746156 ◽

2016 ◽

Vol 2016 ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Muhammad AlHadi Zulkefle ◽

Rohanieza Abdul Rahman ◽

Khairul Aimi Yusof ◽

Wan Fazlida Hanim Abdullah ◽

Mohamad Rusop ◽

...

Keyword(s):

Thin Films ◽

Field Effect ◽

Field Effect Transistor ◽

Ph Sensor ◽

Oxide Semiconductor ◽

Ph Sensing ◽

Spin Speed ◽

Coating Method ◽

Effect Transistor ◽

Sensing Membrane

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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Design and Implementation of a pH Sensor for Micro Solution Based on Nanostructured Ion-Sensitive Field-Effect Transistor

Sensors ◽

10.3390/s20236921 ◽

2020 ◽

Vol 20 (23) ◽

pp. 6921

Author(s):

Yiqing Wang ◽

Min Yang ◽

Chuanjian Wu

Keyword(s):

Field Effect ◽

Field Effect Transistor ◽

Gate Dielectric ◽

Dielectric Material ◽

Ph Sensor ◽

High Sensitivity ◽

Fast Response ◽

Channel Thickness ◽

Effect Transistor ◽

Simulation Results

pH sensors based on a nanostructured ion-sensitive field-effect transistor have characteristics such as fast response, high sensitivity and miniaturization, and they have been widely used in biomedicine, food detection and disease monitoring. However, their performance is affected by many factors, such as gate dielectric material, channel material and channel thickness. In order to obtain a pH sensor with high sensitivity and fast response, it is necessary to determine the appropriate equipment parameters, which have high processing cost and long production time. In this study, a nanostructured ion-sensitive field-effect transistor was developed based on the SILVACO technology computer-aided design (TCAD) simulator. Through experiments, we analyzed the effects of the gate dielectric material, channel material and channel thickness on the electrical characteristics of the nanostructured field-effect transistor. Based on simulation results, silicon nitride was selected as the gate dielectric layer, while indium oxide was chosen as the channel layer. The structure and parameters of the dual channel ion-sensitive field-effect transistor were determined and discussed in detail. Finally, according to the simulation results, a pH sensor based on the nanostructured ion-sensitive field-effect transistor was fabricated. The accuracy of simulation results was verified by measuring the output, transfer and pH characteristics of the device. The fabricated pH sensor had a subthreshold swing as low as 143.19 mV/dec and obtained an actual sensitivity of 88.125 mV/pH. In addition, we also tested the oxidation reaction of hydrogen peroxide catalyzed by horseradish peroxidase, and the sensitivity was up to 144.26 pA mol−1 L−1, verifying that the ion-sensitive field-effect transistor (ISFET) can be used to detect the pH of micro solution, and then combine the enzyme-linked assay to detect the concentration of protein, DNA, biochemical substances, biomarkers, etc.

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Electrical Characteristics and pH Response of a Parylene-H Sensing Membrane in a Si-Nanonet Ion-Sensitive Field-Effect Transistor

Sensors ◽

10.3390/s18113892 ◽

2018 ◽

Vol 18 (11) ◽

pp. 3892 ◽

Cited By ~ 3

Author(s):

Bo Jin ◽

Ga-Yeon Lee ◽

ChanOh Park ◽

Donghoon Kim ◽

Wonyeong Choi ◽

...

Keyword(s):

Field Effect ◽

Field Effect Transistor ◽

Ph Value ◽

Signal To Noise Ratio ◽

Low Frequency ◽

Frequency Noise ◽

Electrical Characteristics ◽

Ph Sensing ◽

Effect Transistor ◽

Sensing Membrane

We report the electrical characteristics and pH responses of a Si-nanonet ion-sensitive field-effect transistor with ultra-thin parylene-H as a gate sensing membrane. The fabricated device shows excellent DC characteristics: a low subthreshold swing of 85 mV/dec, a high current on/off ratio of ~107 and a low gate leakage current of ~10−10 A. The low interface trap density of 1.04 × 1012 cm−2 and high field-effect mobility of 510 cm2V−1s−1 were obtained. The pH responses of the devices were evaluated in various pH buffer solutions. A high pH sensitivity of 48.1 ± 0.5 mV/pH with a device-to-device variation of ~6.1% was achieved. From the low-frequency noise characterization, the signal-to-noise ratio was extracted as high as ~3400 A/A with the lowest noise equivalent pH value of ~0.002 pH. These excellent intrinsic electrical and pH sensing performances suggest that parylene-H can be promising as a sensing membrane in an ISFET-based biosensor platform.

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