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

Sensors ◽  
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.

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

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4184
Author(s):  
Dae Hoon Kim ◽  
Woo Hwan Park ◽  
Hong Gi Oh ◽  
Dong Cheol Jeon ◽  
Joon Mook Lim ◽  
...  
Keyword(s):  
Electrolyte Solution ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Ph Value ◽  
Characteristic Curve ◽  
Reference Electrode ◽  
Reference Channel ◽  
Buffer Solution ◽  
Positive Direction ◽  
Effect Transistor

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.

scholarly journals Graphene Channel Liquid Container Field Effect Transistor as pH Sensor

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
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.

scholarly journals Fabrication of Silicon Nitride Ion Sensitive Field-Effect Transistor for pH Measurement and DNA Immobilization/Hybridization

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
U. Hashim ◽  
Soon Weng Chong ◽  
Wei-Wen Liu
Keyword(s):  
Silicon Nitride ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Drain Current ◽  
Biologically Active ◽  
Ph Measurement ◽  
Dna Immobilization ◽  
Buffer Solution ◽  
Effect Transistor ◽  
Sensing Membrane

The fabrication of ion sensitive field-effect transistor (ISFET) using silicon nitride (Si3N4) as the sensing membrane for pH measurement and DNA is reported. For the pH measurement, the Ag/AgCl electrode was used as the reference electrode, and different pH values of buffer solution were used in the ISFET analysis. The ISFET device was tested with pH buffer solutions of pH2, pH3, pH7, pH8, and pH9. The results show that the IV characteristic of ISFET devices is directly proportional and the device’s sensitivity was 43.13 mV/pH. The ISFET is modified chemically to allow the integration with biological element to form a biologically active field-effect transistor (BIOFET). It was found that the DNA immobilization activities which occurred on the sensing membrane caused the drain current to drop due to the negatively charged backbones of the DNA probes repelled electrons from accumulating at the conducting channel. The drain current was further decreased when the DNA hybridization took place.

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

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3892 ◽  
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.

CHARACTERIZATION OF ZNO/TIO2 BILAYER FILM FOR EXTENDED GATE FIELD-EFFECT TRANSISTOR (EGFET) BASED PH SENSOR

2016 ◽  
Vol 78 (5-8) ◽  
Author(s):  
Rohanieza Abdul Rahman ◽  
Muhammad AlHadi Zulkefle ◽  
Khairul Aimi Yusof ◽  
Wan Fazlida Hanim Abdullah ◽  
Mohamad Rusop Mahmood ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Sol Gel ◽  
Ph Sensor ◽  
Deposition Process ◽  
Bilayer Film ◽  
Buffer Solution ◽  
Effect Transistor ◽  
Ph Buffer

An extended gate field-effect transistor (EGFET) of ZnO/TiO2 bilayer film as pH sensor was demonstrated in this paper. The sol-gel zinc oxide (ZnO) and titanium dioxide (TiO2) were prepared and spin coated onto indium tin oxide (ITO) coated glass substrate. After deposition process, this bilayer film then was annealed from 200⁰C up to 700⁰C. EGFET measurement employed to obtain the sensitivity of the bilayer thin film towards pH buffer solution, which is pH4, pH7 and pH10. According to the measurement process, we obtained that bilayer film annealed at 400⁰C produced highest sensitivity among other bilayer film, which is 66.8 mV/pH.    

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