Two-Channel Graphene pH Sensor Using Semi-Ionic Fluorinated Graphene Reference Electrode

A reference electrode is necessary for the working of ion-sensitive field-effect transistor (ISFET)-type sensors in electrolyte solutions. The Ag/AgCl electrode is normally used as a reference electrode. However, the Ag/AgCl reference electrode limits the advantages of the ISFET sensor. In this work, we fabricated a two-channel graphene solution gate field-effect transistor (G-SGFET) to detect pH without an Ag/AgCl reference electrode in the electrolyte solution. One channel is the sensing channel for detecting the pH and the other channel is the reference channel that serves as the reference electrode. The sensing channel was oxygenated, and the reference channel was fluorinated partially. Both the channels were directly exposed to the electrolyte solution without sensing membranes or passivation layers. The transfer characteristics of the two-channel G-SGFET showed ambipolar field-effect transistor (FET) behavior (p-channel and n-channel), which is a typical characteristic curve for the graphene ISFET, and the value of VDirac was shifted by 18.2 mV/pH in the positive direction over the range of pH values from 4 to 10. The leakage current of the reference channel was 16.48 nA. We detected the real-time pH value for the two-channel G-SGFET, which operated stably for 60 min in the buffer solution.

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Effects of Buffer Concentration on the Sensitivity of Silicon Nanobelt Field-Effect Transistor Sensors

Sensors ◽

10.3390/s21144904 ◽

2021 ◽

Vol 21 (14) ◽

pp. 4904

Author(s):

Chi-Chang Wu ◽

Min-Rong Wang

Keyword(s):

Field Effect ◽

Field Effect Transistor ◽

Crystalline Silicon ◽

Ph Value ◽

Buffer Concentration ◽

Buffer Solution ◽

Solution Ph ◽

Effect Transistor ◽

Response Current ◽

Biomolecule Sensing

In this work, a single-crystalline silicon nanobelt field-effect transistor (SiNB FET) device was developed and applied to pH and biomolecule sensing. The nanobelt was formed using a local oxidation of silicon technique, which is a self-aligned, self-shrinking process that reduces the cost of production. We demonstrated the effect of buffer concentration on the sensitivity and stability of the SiNB FET sensor by varying the buffer concentrations to detect solution pH and alpha fetoprotein (AFP). The SiNB FET sensor was used to detect a solution pH ranging from 6.4 to 7.4; the response current decreased stepwise as the pH value increased. The stability of the sensor was examined through cyclical detection under solutions with different pH; the results were stable and reliable. A buffer solution of varying concentrations was employed to inspect the sensing capability of the SiNB FET sensor device, with the results indicating that the sensitivity of the sensor was negatively dependent on the buffer concentration. For biomolecule sensing, AFP was sensed to test the sensitivity of the SiNB FET sensor. The effectiveness of surface functionalization affected the AFP sensing result, and the current shift was strongly dependent on the buffer concentration. The obtained results demonstrated that buffer concentration plays a crucial role in terms of the sensitivity and stability of the SiNB FET device in chemical and biomolecular sensing.

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Analysis on Band Layer Design and J-V characteristics of Zinc Oxide Based Junction Field Effect Transistor

Journal La Multiapp ◽

10.37899/journallamultiapp.v1i2.108 ◽

2020 ◽

Vol 1 (2) ◽

pp. 14-21

Author(s):

Chaw Su Nandar Hlaing Chaw ◽

Thiri Nwe

Keyword(s):

Zinc Oxide ◽

Field Effect ◽

High Performance ◽

Field Effect Transistor ◽

Field Effect Transistors ◽

Characteristic Curve ◽

Vital Role ◽

Semiconductor Material ◽

Mathematical Equations ◽

Effect Transistor

This paper presents the band gap design and J-V characteristic curve of Zinc Oxide (ZnO) based on Junction Field Effect Transistor (JFET). The physical properties for analysis of semiconductor field effect transistor play a vital role in semiconductor measurements to obtain the high-performance devices. The main objective of this research is to design and analyse the band diagram design of semiconductor materials which are used for high performance junction field effect transistor. In this paper, the fundamental theory of semiconductors, the electrical properties analysis and bandgap design of materials for junction field effect transistor are described. Firstly, the energy bandgaps are performed based on the existing mathematical equations and the required parameters depending on the specified semiconductor material. Secondly, the J-V characteristic curves of semiconductor material are discussed in this paper. In order to achieve the current-voltage characteristic for specific junction field effect transistor, numerical values of each parameter which are included in analysis are defined and then these resultant values are predicted for the performance of junction field effect transistors. The computerized analyses have also mentioned in this paper.

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Graphene Channel Liquid Container Field Effect Transistor as pH Sensor

Journal of Nanomaterials ◽

10.1155/2014/547139 ◽

2014 ◽

Vol 2014 ◽

pp. 1-6 ◽

Cited By ~ 29

Author(s):

Xin Li ◽

Junjie Shi ◽

Junchao Pang ◽

Weihua Liu ◽

Hongzhong Liu ◽

...

Keyword(s):

Field Effect ◽

Field Effect Transistor ◽

Ph Value ◽

Ph Sensor ◽

Drain Current ◽

Fast Response ◽

Monolayer Graphene ◽

Ph Sensing ◽

Order Of Magnitude ◽

Effect Transistor

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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