SnO2 extended gate field-effect transistor as pH sensor (original) (raw)
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Jurnal Teknologi, 2016
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 200⁰ C up to 700⁰ C. 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 400⁰ C produced highest sensitivity among other bilayer film, which is 66.8 mV/pH.
A novel SnO2/Al discrete gate ISFET pH sensor with CMOS standard process
Sensors and Actuators B: Chemical, 2001
In this paper, we present a method allowing industrial production of integrated ion sensitive ®eld effect transistor (ISFET) sensor. An ASIC CMOS standard process is used to integrate the sensor and signal processing circuit; then the sensor is plated with the sensing membrane (SnO 2) by sputtering. The structure of the ISFET is novel SnO 2 /Al discrete gate. The discrete gate ISFET and the readout circuit were fabricated with a conventional standard CMOS IC process where no extra mask was required. The experimental data show that the SnO 2 /Al discrete gate ISFET sensors have a high linearity of 58 mV/pH in a concentration ranging from pH 2 to 10. The low offset and low power readout circuit for the discrete gate ISFETs pH sensor was designed and evaluated for monolithic in this study.
IOP Conference Series: Materials Science and Engineering
Zinc Oxide (ZnO) nanostructures were deposited using chemical bath deposition (CBD) technique in water bath at 95 °C for 4 h. Post-deposition heat treatment in air ambient at various temperature ranging from 200-600 °C for 30 min was applied in order to enhance the electrical properties of ZnO nanostructures as the sensing membrane of extended-gate field effect transistor (EGFET) pH sensor. The as-deposited sample was prepared for comparison. The samples were characterized in terms of physical and sensing properties. FESEM images showed that scattered ZnO nanorods were formed for the as-deposited sample, and the morphology of the ZnO nanorods changed to ZnO nanoflowers when the heat treatment was applied from 200-600 °C. For sensing properties, the samples heated at 300 °C showed the higher sensitivity which was 39.9 mV/pH with the linearity of 0.9792. The sensing properties was increased with the increasing annealing treatment temperature up to 300 °C before decreased drastically.
The influence of isothermal annealing on tin oxide thin film for pH-ISFET sensor
Sensors and Actuators B: Chemical, 2000
The aim of this paper is to investigate pH sensitivity of tin oxide thin films prepared by thermal evaporation, and the influences of Ž. isothermal annealing on its characteristics. A series of capacitance-voltage C-V curves of SnO rSiO rSi electrolyte insulator 2 2 Ž. Ž semiconductor EIS diodes are used to evaluate pH sensitivity of tin oxide thin films. The results show that tin oxide thin films as. grown have linear pH sensitivities of approximately 58 mVrpH in a concentration range between pH 2 and pH 10. However, pH sensitivity decreases after the isothermal annealing processes at 3008C, 4008C, and 5008C in N ambiance for 1 h; and pH sensitivity goes 2 further down to only 33 mVrpH, after annealing in N ambiance for 15 h. This phenomenon influences the structure of tin oxide thin 2 films, which will undergo phase transition from amorphous to polycrystal after the isothermal annealing process. Ž .Ž. Moreover, the characteristics of the tin oxide gate ion-sensitive field-effect transistor ISFET SnO rSiO gate ISFET , where the tin 2 2 oxide is formed under optimum condition, is also presented in this paper.
Journal of Electroanalytical Chemistry, 2015
In this work, we developed thick film pH sensors based on the nanostructured RuO 2-SnO 2 system and analyzed their sensing mechanism using the potentiometric and electrochemical impedance spectroscopic (EIS) methods. The crystal structure and morphology of the sensitive films were investigated by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. The potentiometric sensor exhibits Nernstian behavior (56.5 mV/pH) in the pH range of 2-12. It shows very fast response (5 s and 9 s, for acidic to basic and basic to acidic solutions), long lifetime, small hysteresis effect, and good reproducibility. Selectivity test proved that the presence of Li + , Na + , and K + ions in a solution had no significant influence on the sensor performance. Conductance, capacitance and impedance of the conductimetric pH sensor with the interdigitated electrode were found to vary with changing pH and as a function of the applied frequency in the range of 10 Hz-2 MHz. The EIS analysis of the complex impedance data by using Nyquist and Bode plots revealed the information about the underlying processes, like adsorption, diffusion and charge transfer, occurring at the metal oxide-solution interface. The proposed thick film pH sensors were intended to be used for water pollution monitoring.
Indium tin oxide synthesized by a low cost route as SEGFET pH sensor
Materials Research, 2013
Polycrystalline ITO films with good optoelectronics characteristics and homogeneous surface has been obtained upon annealing at 550 °C in N 2 atmosphere using a low-cost chemical vapor deposition (CVD) system. The films were evaluated as pH sensors in separative extended gate field-effect transistor (SEGFET) apparatus, exhibiting a sensitivity of 53 mV/pH, close to the expected Nernstian theoretical value for ion sensitive materials. The use of CVD process to synthesize ITO, as described here, may represent an alternative for fabrication of SEGFET pH sensors at low cost to be used in disposable biosensors since H + ions are the product of several oxireductase enzymes.
Solid-State Electronics, 2018
Sensing properties of various high-k sensing membrane, such as SnO 2 , HfO 2 , ZrO 2 , and Ta 2 O 5 , in dual gate extended-gate field-effect transistor (EGFET) were investigated. By adapting the dual-gate structure, high sensitivity exceeding the conventional Nernstian limit on sensitivity (59.15 mV/pH at 25°C) was realized due to capacitive coupling effect. As a results, it was confirmed that dual-gate EGFET with Ta 2 O 5 sensing membrane which has high permittivity shows the highest sensitivity of 478.0 mV/pH as well as excellent hysteresis voltage and drift rate characteristics.
2019
Zinc Oxide (ZnO) nanostructures deposited using simple chemical bath deposition (CBD) at different deposition time ranging from 1 to 4 hours on indium tin oxide (ITO) substrates are proposed as sensing membrane of extended-gate field effect transistor (EGFET) pH sensor. The ZnO nanostructures were grown without any seed or catalyst layer. The deposited samples were characterized on their physical properties in order to investigate the correlation between physical properties and pH sensing behavior based on the influence of various deposition time to the physical properties. It is evident from the FESEM result that the nanostructures growth density is directly proportional to the growth time. Same goes on crystallinity quality of the samples that shows the same pattern as growth density. The physical properties of the ZnO nanostructures can be related to the immersion time and in turn influence the pH sensor performance. All deposited samples showed the ability to be applied as the s...
Gels
A highly selective and sensitive EGFET-pH sensor based on composite TiO2–PANI had been developed in this work. A sol-gel titanium dioxide (TiO2) and the composite of TiO2 with semiconducting polyaniline (PANI) were deposited using a simple spin-coating method on an indium tin oxide (ITO) substrate. The films have been explored as a sensing electrode (SE) of extended gate field-effect transistor (EGFET) for pH applications in the range of pH 2 to 12. The pH sensitivities between TiO2, TiO2–PANI bilayer composite, and TiO2–PANI composite thin films were discussed. Among these, the TiO2–PANI composite thin film showed a super-Nernstian behavior with high sensitivity of 66.1 mV/pH and linearity of 0.9931; good repeatability with a standard deviation of 0.49%; a low hysteresis value of 3 mV; and drift rates of 4.96, 5.54, and 3.32 mV/h in pH 4, 7, and 10, respectively, for 6 h. Upon applying the TiO2–PANI composite as the SE for nitrate measurement, low sensitivity of 12.9 mV/dec was obt...
Journal of Electrical, Electronic, Information, and Communication Technology
We fabricated a ZnO nanostructures based TFT on plastic substrate by solution method under low temperature. ZnO nanostructures were prepared by zinc nitrate hexahydrate, and hexamethylenetetramine. The device shows hard saturation characteristics and exhibits a high off-resistance. The output characteristics devices also shows current saturation and pinch off behavior, in which the high of current saturation obtained 266 mA at VGS = 40 V and VDS = 42.5 V. The pH response on the electrical properties was also studied. It was found that the threshold voltage shifted from 10.21 V to 13 V as pH solution gradually increased. The Ion/Ioff for as grown TFTs and TFTs with pH response of 10.21 shifted from 1.86 x 105 to 7.03 x 106 at VDS = 20 V. The obtained sensitivity of devices was 1.05 V/pH.