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Non-enzymatic urea sensor using molecularly imprinted polymers surface modified based-on ion-sensitive field effect transistor (ISFET)
(2016-11-25)
Rayanasukha, Y.
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Pratontep, S.
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Porntheeraphat, S.
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Bunjongpru, W.
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Nukeaw, J.
A novel molecularly imprinted electrochemical sensor based on ISFET device has been developed for urea detection sensor. The molecularly imprinted polymers (MIPs) were prepared by photopolymerization on the surface of ISFET device using PMMA and urea as the functional polymer and molecular template, respectively. The fabricated sensors were characterized by potentiometry and UV-Vis spectroscopy. The preparation conditions were optimized for performance of the sensors, i.e. drop-cast volume and incubation time. The MIP modified ISFET sensors has linear range response from 1.0 × 10− 4 to 1.0 × 10− 1 M with the limit of detection of 1.0 × 10− 4 M (S/N = 3). The MIP modified ISFET sensors also exhibit excellent reproducibility, repeatability and stability, as well as high selectivity to urea.
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Durable nitrate sensor by surface modification
(2016-11-25)
Chaisriratanakul, W.
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Bunjongpru, W.
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Jeamsaksiri, W.
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Srisuwan, A.
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Porntheeraphat, S.
This work presents the development of nitrate sensor based on Ion Sensitive Field Effect Transistor (ISFET) technology to achieve longer device's lifetime. This lifetime depended on the adhesion of PVC ion-selective membrane on the Si<inf>3</inf>N<inf>4</inf> sensing membrane of ISFET. The adhesion level directly affected the leaching of plasticizer. Such improvement utilized surface modification techniques by immersing the sensing membrane in the solution of 5% 3-mercaptopropyl-trimethoxysilane (MPTMS)/methanol. The modified surface was detected through the change of hydrophobicity and thickness of MPTMS using the contact angle measurement and ellipsometry techniques. The appropriate time for immersion was 18 h. The modified surface achieved the optimal hydrophobicity with contact angle of 100.32°. The presence of MPTMS film was confirmed by detecting the thiol-group using Fourier Transform Infrared (FTIR) spectrophotometry and Auger Electron Spectroscopy (AES). The PVC ion-selective membrane was then immobilized on the surface to create nitrate sensors with the following characteristics. The Nitrate-Nitrogen detection limit = 2.44 ppm with linear range from 5 to 60 ppm at sensitivity of 56 mV/dec. (R2 = 1). The response time was 90 s. Finally, this nitrate sensor could extend the total utilization lifetime from 8 to 17 weeks.
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Tantalum oxide bio-photonics thin film grown by gas-timing innovation technique
(2013-09-18)
Khemasiri, N.
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Porntheeraphat, S.
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Horprathum, M.
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Chananonnawathorn, C.
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Bunjongpru, W.
Tantalum oxide (TaxOy) as high refractive index material has been grown on p-type silicon and quartz substrates by R.F. magnetron sputtering with our innovative technique called "reactive-gas timing". The reactive gas timing technique is an on-off time period sequence between argon (Ar) and oxygen (O2) plasma during sputtering process. The technique of gas-timing plays the effect on the properties of TaxOy thin film. The bombarded Ar-plasma was varied at 2, 5 and 8 sec, while the period of reactive O2-plasma was kept at 5 sec in this experiment. The physical and optical properties were investigated by using X-ray diffraction (XRD), Atomic Force Microscope (AMF), UV-Visible spectrometer and Spectroscopic Ellipsometer, respectively. The XRD spectra and AFM photographs show all films are amorphous phase with smooth feature. Meanwhile the transmittance of sputtered thin film decreases with 10% and the absorption edge shifts to lower energy with the increasing of the argon period from 2 sec to 8 sec. The refractive index as showed by ellipsometry slightly increases from 2.08 to 2.17 at wavelength 550 nm with the increasing of argon period from 2 sec to 8 sec. The increasing of the refractive index might dues to tantalum (Ta) rich which consists in thin films. The Ar-plasma period in the deposited film plays an important role on the properties of the TaxOy thin films especially as optical refractive index material. © 2013 SPIE.
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Very low drift and high sensitivity of nanocrystal-TiO 2 sensing membrane on pH-ISFET fabricated by CMOS compatible process
(2013-02-15)
Bunjongpru, W.
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Sungthong, A.
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Porntheeraphat, S.
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Rayanasukha, Y.
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Pankiew, A.
High sensitivity and very low drift rate pH sensors are successfully prepared by using nanocrystal-TiO <inf>2</inf> as sensing membrane of ion sensitive field effect transistor (ISFET) device fabricated via CMOS process. This paper describes the physical properties and sensing characteristics of the TiO <inf>2</inf> membrane prepared by annealing Ti and TiN thin films that deposited on SiO <inf>2</inf> /p-Si substrates through reactive DC magnetron sputtering system. The X-ray diffraction, scanning electron microscopy and Auger electron spectroscopy were used to investigate the structural and morphological features of deposited films after they had been subjected to annealing at various temperatures. The experimental results are interpreted in terms of the effects of amorphous-to-crystalline phase transition and subsequent oxidation of the annealed films. The electrolyte-insulator-semiconductor (EIS) device incorporating TiON membrane that had been obtained by annealing of TiN thin film at 850 °C exhibited a higher sensitivity (57 mV/pH), a higher linearity (1), a lower hysteresis voltage (1 mV in the pH cycle of 7 → 4 → 7 → 10 → 7), and a smaller drift rate (0.246 mV/h) than did those devices prepared at the other annealing temperatures. Furthermore, this pH-sensing device fabrication process is fully compatible with CMOS fabrication process technology. © 2012 Elsevier B.V. All rights reserved.
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UV-enhanced photodetector with nanocrystalline-TiO 2 thin film via CMOS compatible process
(2011-12-01)
Bunjongpru, W.
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Panprom, P.
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Porntheeraphat, S.
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Meananeatra, R.
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Jeamsaksiri, W.
This research presents nanocrystal titaniumdioxide (nanocrystal-TiO <inf>2</inf>) film deposition technique with CMOS compatible process [1] to extend the optical response bandwidth of silicon based photodetecting devices toward ultraviolet range [2]. The thin films were initially deposited as Titanium Nitride (TiN) using DC magnetron reactive sputtering system. It was then annealed under nitrogen atmosphere at 800°C. After analyzing crystal structures and surface morphology with X-ray diffraction and FE-SEM systems, it was found that the deposited thin films showed the crystal phase of TiO <inf>2</inf> oriented along (200) plane of Rutile crystal structure with 50 nm grain size and increasing with film thickness. Using electroreflectance (ER) spectroscopy measurement [3], the bandgap of nanocrystal-TiO <inf>2</inf> was revealed to be 3.16 eV. PN-heterojunction photodiodes were fabricated with Nanocrystal-TiO <inf>2</inf>/SiO <inf>2</inf>/p-Si structures. Interdigitated aluminum structures were used as electrodes. By varying the thickness of nanocrystal-TiO <inf>2</inf> film, i.e. 30, 60, and 90 nm, the devices could response further into the UV range. The absorption edge wavelength investigated by photoresponse measurement was at 275 nm and shifting to the shorter wavelength as a function of the nanocrystal-TiO <inf>2</inf> grain size due to quantum confinement phenomenon [4]. The nanocrystal-TiO <inf>2</inf>/SiO <inf>2</inf>/p-Si photodetector had dark current = 5.31nA (2V), photocurrent = 0.9 uA, rise time = 58 us, fall time = 47 us at 30 nm thickness of TiO <inf>2</inf>. © 2011 IEEE.
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Oxygen gas-timing control for variety properties of sputtered-ZnO
(2010-02-05)
Limwichean, K.
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Porntheeraphat, S.
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Bunjongpru, W.
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Panprom, P.
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Pankiew, A.
In this report, we present sputtered zinc oxide (ZnO) thin films grown with different argon (Ar) and oxygen (O<inf>2</inf>) gas-timing sequence. Metallic zinc (Zn) with 5N-purity was used as a sputtering target, while Ar and O <inf>2</inf> of 6N-purity were used as the bombard and reactive gases, respectively. The crystalline orientation, surface morphology, chemical composition, optical and electrical properties of deposited ZnO thin films were determined by XRD,AFM and UV-VIS measurement, respectively. The XRD result implied that deposition ZnO thin films at different O<inf>2</inf> gas-timing control corresponded to the (002) plane of hexagonal ZnO structure at 2θ = 34.4°. Furthermore, when the reactive time of O<inf>2</inf> was increased, the transmittance of ZnO thin films exhibited the energy gap increase from ∼2.95 to ∼3.18 eV, whereas the surface roughness was found to decrease. Finally, ZnO thin films were oxidized after the deposition. © (2010) Trans Tech Publications.
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Nanocrystal-ZnO thin film deposition by a novel reactive gas-timing RF magnetron sputtering provided for UV photodetectors
(2010-02-05)
Panprom, P.
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Porntheeraphat, S.
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Bunjongpru, W.
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Tiwawong, T.
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Yamwong, W.
The fabrication and characterizations of nanocrystal-ZnO thin film used as active layer of MSM-photodetector structure are reported. The ZnO thin film were successfully sputtered on SiO<inf>2</inf>/Si substrates without heating or annealing processes by using a novel reactive gas-timing technique. In our experiment, the ZnO thin film properties with different gas-timing ratio of Ar/O<inf>2</inf> were investigated. For fabricating of UV detector, the Al interdigitate electrode was deposited on SiO<inf>2</inf>/Si substrate by DC sputtering process and ZnO thin film was deposited as active layer. The response wavelength peak occurs at around 380 nm corresponding to ZnO energy bandgap of 3.2 eV .The I-V measurements indicates the Schottky behavior of ZnO on Al contact. © (2010) Trans Tech Publications.
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Application of double gate ion sensitive field effect transistor for detection of fluid flow rate in micro-channel
(2010-02-05)
Jiemsakul, T.
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Trithaveesak, O.
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Bunjongpru, W.
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Hruanun, C.
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Poyai, A.
In this work a micro flow sensor, using a double gate Ion Sensitive Field Effect Transistor (ISFET) and two metal electrodes, for fluid flow rate measurement in micro-channels were fabricated and demonstrated. By the channel fabrication the molds were patterned reversely on a silicon wafer using Deep Reactive Ion Etcher (DRIE). The double gate ISFET and two metal electrodes were placed on the mold in the distance 15 millimeters. The channels were formed using polydimethylsiloxane (PDMS) from the mold with the width 1000 and 2000 micrometer and the depth of 250 micrometer. After removing PDMS from the mold the channel was bonded with glass substrate by RF plasma technique. By the verification of flow sensors working range water and one mole of sodium nitrate solution were alternated in flow channel. The fluid flow rate were compared with the flow rate from weighing. It found from the comparison that the high deviation was found at low flow rate. Furthermore, the deviation depends also on the dimension of the flow channel. © (2010) Trans Tech Publications.
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On-chip platinum micro-heater with platinum temperature sensor for a fully integrated disposable PCR module
(2010-02-05)
Sripumkhai, W.
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Lekwichai, A.
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Bunjongpru, W.
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Porntheeraphat, S.
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Tunhoo, B.
The on-chip platinum micro-heater prototypes for thermal cycling equipped with platinum temperature sensor are fabricated. The device has been designed, fabricated and characterized to explore the feasibility of the micro-heater for a fully integrated disposable lab-on-a-chip with the PCR module. The on-chip micro-heater demonstrates that the temperature transitions are shorter by comparison with the conventional PCR temperature routines. © (2010) Trans Tech Publications.
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The optimization of TiN film deposited by DC magnetron sputtering provided for Al diffusion barrier
(2010-02-05)
Pankiew, A.
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Bunjongpru, W.
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Somwang, N.
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Porntheeraphat, S.
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Pratontep, S.
Titanium nitride (TiN) film has been widely used as a diffusion barrier layer for VLSI contact metallization because TiN is an excellent barrier against inter-diffusion between Al and Si substrate or silicide. In this work, we studied the properties of TiN films deposited by DC magnetron sputtering with varying N<inf>2</inf>:Ar flow rate ratio in order to optimize growth conditions and film properties provided for Al diffusion barrier purpose. The TiN films were deposited at the constant pressure level and sputtering time. The crystalline orientation, composition and electrical properties of deposited TiN films were characterized by XRD, AES-depth profile and Four Point Probe measurement, respectively. The XRD results show that the deposited TiN film has two preferred orientations of TiN(111) and TiN(200) planes. The highest intensity of the TiN(111) plane was obtained when the N<inf>2</inf>:Ar flow rate ratio was 3:1. The electrical resistivity was increased when the N <inf>2</inf>:Ar flow rate ratio was decreased. The minimum electrical resistivity is 127.8 μΩ-cm when the N<inf>2</inf>:Ar flow rate ratio is 3:1. © (2010) Trans Tech Publications.

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