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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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The MSM diamond device for direct and indirect X-ray detection
(2015-07-01)
Cheirsirikul, S.
;
Jesen, S.
;
Hruanun, C.
Development synthesizing diamond film on silicon substrate was processed by Hot Filament Chemical Vapor Deposition (HFCVD). The gas processes using of H<inf>2</inf> and CH<inf>4</inf> to produce intrinsic diamond and MSM device constructed on the diaphragm of diamond film. Schottky junctions on the top and the lower diaphragm were produced by aluminum metal. After that, the result of detecting a direct and indirect X-ray of MSM diamond was satisfactory because it could respond along with increasing of X-ray intensity. The X-ray expose time of indirect expose by BaF<inf>2</inf> scintillator faster more than direct expose.
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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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The vertical MSM diamond X-ray detector
(2012-06-01)
Cheirsirikul, S.
;
Jesen, S.
;
Hruanun, C.
Development synthesizing diamond film on (100) silicon substrate was processed by HFCVD (Hot Filament Chemical Vapor Deposition). The processes consisted of using methane (CH <inf>4</inf>) to produce intrinsic diamond and built MSM device on the diamond film. The top and the bottom of diamond is Schottky junctions were produced by aluminum which caused the carriers were able to move in the vertical direction to reduce the effect of grain boundaries. After that, the result of detecting an X-ray of MSM diamond was satisfactory because it could respond along with increasing of intensity of an X-ray and X-ray expose time. © 2012 IEEE.
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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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MSM diamond UV detector
(2011-10-04)
Cheirsirikul, S.
;
Jesen, S.
;
Hruanun, C.
Development Synthesizing Diamond film on (100) silicon substrate was processed by HFCVD (Hot Filament Chemical Vapor Deposition). The processes consisted of using methane (CH4) to produce intrinsic diamond and then constructing MSM device on the diaphragm of diamond film. Schotthy junctions on the top and the lower of the diaphragm were produced by aluminum which caused the carriers were able to move in the vertical direction to reduce the effect of grain boundaries. Then, the spectral response was investigated for the light wavelength in the range of 190 nm to 800 nm. The results showed that the device had good response to UV light and very low response to visible light. After that the device was sintered at 450OC in different times in order to find the decreased leakage current and proper response time. © 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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Chemical characterization and electrical properties of indium oxynitride grown by reactive gas-timing RF magnetron sputtering
(2010-02-05)
Sungthong, A.
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Khomdet, P.
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Porntheeraphat, S.
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Hruanun, C.
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Poyai, A.
This work investigates changes in the chemical composition of InON thin films, grown by reactive gas-timing rf magnetron sputtering with different O<inf>2</inf>:N<inf>2</inf> timing ratio characterized by Auger Electron Microscope (AES), Raman Spectroscopy which are well correlated with the electrical properties of films. The existence of nitrogen and oxygen in the deposited InON thin films was revealed by AES. Two Raman active optical phonons have been clearly observed and assigned to InN E<inf>1</inf>(TO) at ∼470 cm-1 and E<inf>1</inf>(LO) at ∼570 cm-1 and also shifted with different O<inf>2</inf>:N<inf>2</inf> timing ratio. The carrier mobility of InON thin films was decreased when the ratio of O<inf>2</inf>:N <inf>2</inf> timing is increased. © (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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