Ph.D. Student, Universiti Sains Malaysia/ School of Physics
The research is about synthesis CuS thin film by SPD and implement it as EGFET pH sensor
The research area is physics and biosensor, it is about how to prepare thin films with nanostructure and to applied it as a biosensor.
Abstract: Abstract Several studies have been performed on the use of ITO as an extended gate of field effect transistor. Studies have also been done on the effects of using ITO as a substrate to improve the sensitivity of SnO2 membrane. In this research, the ITO was used as a substrate for the synthesis of CuS thin films to determine its potential to improve sensitivity and any possible application as pH sensors. The CuS thin film was prepared from copper chloride and sodium thiosulfate via spray pyrolysis deposition using de-ionized water as a solvent. The sensitivity of the CuS/ITO membrane was measured and comparatively analyzed against that of CuS membrane. Structural and morphological properties were investigated for both as-deposit thin films. The membranes were then deployed as pH sensors and their sensitivities measured. The results confirmed that CuS/ITO membrane had much better sensitivity (37 µA/pH and 37 mV/pH) compared to CuS membrane (8 µA/pH and 7.5 mV/pH).AbstractSeveral studies have been performed on the use of ITO as an extended gate of field effect transistor. Studies have also been done on the effects of using ITO as a substrate to improve the sensitivity of SnO2 membrane. In this research, the ITO was used as a substrate for the synthesis of CuS thin films to determine its potential to improve sensitivity and any possible application as pH sensors. The CuS thin film was prepared from copper chloride and sodium thiosulfate via spray pyrolysis deposition using de-ionized water as a solvent. The sensitivity of the CuS/ITO membrane was measured and comparatively analyzed against that of CuS membrane. Structural and morphological properties were investigated for both as-deposit thin films. The membranes were then deployed as pH sensors and their sensitivities measured. The results confirmed that CuS/ITO membrane had much better sensitivity (37 µA/pH and 37 mV/pH) compared to CuS membrane (8 µA/pH and 7.5 mV/pH).2
Pub.: 22 Aug '16, Pinned: 28 Jul '17
Abstract: Copper sulphide (CuS) thin films were grown upon Ti, indium tin oxide (ITO), and glass substrates by using spray pyrolysis deposition at 200°C. The films exhibited good adhesion compared to chemical bath deposition. CuCl2·2H2O and Na2S2O3·5H2O precursors were used as Cu2+ and S2− sources, respectively. Two concentrations (i.e., 0.2 M and 0.4 M) were selected in this study. X-ray diffraction analysis reveals that the films with 0.2 M showed only the formation of a covellite CuS phase having a hexagonal crystal structure with diffraction peaks of low intensity. For 0.4 M concentration, in addition to the covellite CuS phase, chalcocite Cu2S phase having a hexagonal crystal structure also appeared with relatively higher intensity peaks for all thin films. Field-emission scanning electron microscopy observations showed the formation of small grains for 0.2 M, whereas a mixture of grains with square-like shape and nanoplates were formed for 0.4 M. Depending on the 0.2 M and 0.4 M thin films thicknesses (3.2 μm and 4 μm, respectively), the band gap energy was obtained from optical measurements to be approximately 2.64 eV for 0.2 M (pure CuS phase), which slightly decreased up to 2.56 eV for 0.4 M concentration. Hall effect measurements showed that all grown films are p-type. The 0.2 M film exhibited much lower sheet resistance (Rsh = 33.96 Ω/Sq–55.70 Ω/Sq) compared to 0.4 M film (Rsh = 104.33 Ω/Sq–466.6 Ω/Sq). Moreover, for both concentrations, the films deposited onto ITO substrate showed the lowest sheet resistance (Rsh = 33.96 Ω/Sq–104.33 Ω/Sq).
Pub.: 12 Sep '16, Pinned: 28 Jul '17
Abstract: In this study, CuS thin films with p-type behaviour were prepared using two solvent types: deionized water (S1) and deionized water mixed with ethanol (S2). The thin films were deposited onto substrates comprising glass slide, multilayer of ZnO/Cu/ZnO, ZnO nanorods and Poly(methyl methacrylate) (PMMA). XRD analysis revealed the presence of covellite-CuS phase and chalcocite-Cu2S phase with average crystallite sizes of 14.1 nm and 15.4 nm, respectively in S1 sample while only covellite-CuS phase with an average crystallite size of 11.6 nm was identified for S2. Morphological observations (SEM) showed smaller sized nanoplates in S1 compared to S2. The results from implementation of the two devices as hydrogen gas sensors revealed S1 exhibits better sensitivity (98.9% at 1000 ppm) and shorter response and recovery times (16 s and 34 s at 800 ppm, respectively) compared to S2 (sensitivity of 78.4% at 1000 ppm; response and recovery times of 35 s and 24.4 s at 1000 ppm, respectively). The sensitivity was found to increase with increasing gas concentration for both samples. It was inferred from the results that CuS thin film prepared with only deionized water (S1) has a higher H2 gas detection potential.
Pub.: 28 Aug '16, Pinned: 28 Jul '17
Abstract: Many studies have been conducted on membranes implemented as pH sensors for measuring pH sensitivity; nevertheless, the effect of metal oxide semiconductor field effect transistors was not taken into account. Hence, this study was conducted to measure the sensitivity of the CuS membrane with and without a field effect transistor. The CuS membrane was deposited onto a glass substrate using the spray pyrolysis technique. The sensitivity and linearity in the absence of the field effect transistor were measured to be 22.86 mV/pH and 95.62%, whereas the presence of the field effect showed slightly higher sensitivity and linearity of 24 mV/pH and 98.18%, respectively. The CuS membrane synthesized in the presence of the field effect transistor also showed higher stability because the metal oxide semiconductor was not immersed in a buffer solution. Furthermore, the hysteresis of the CuS membrane, measured for 5 min, yielded a value of 12.8 mV. The structural characteristics of the membrane confirmed the formation of a single, pure CuS phase, whereas the morphological characteristics showed porous agglomerations of square nanocrystals.
Pub.: 01 Nov '16, Pinned: 28 Jul '17
Abstract: Several studies have deposited copper sulphide (CuS) thin films via spray pyrolysis using a heater. In this study, the spray pyrolysis deposition of CuS thin films was carried out using two processes; the first process called pyrolytic process to deposit CuS thin film on glass, ITO, Si and tungsten substrates using CW CO2 laser beam (10.6 μm, 40 W) as the heat source rather than a heater, while the second process called photolytic process to deposit CuS thin film on glass substrate by apply the laser directly on the droplet after leaving the nozzle. Copper chloride and sodium thiosulfate were used as precursor materials for the preparation of CuS. Deionized water was used to dissolve 0.4 M concentration of copper chloride and sodium thiosulfate, separately. In pyrolytic process, the glass, ITO, Si and tungsten substrates were placed on a rotator fan to provide large surface area coating, and to ensure uniform distribution of laser beam heat and the sprayed solution through deposition. Hence, homogenous films of CuS nanocrystallites with covellite phase with good structural and morphological characteristics were obtained. In photolytic process, the glass substrate was placed on the heater and the laser was guided toward the droplet exactly after leaving the nozzle, to achieve resonant absorption of the laser by aerosols. The structure of this film was differ from the previous films, it contains S element in addition to the pure CuS covellite phase. The membrane surface parameters (number of ions, crystallite size, surface-to-volume ratio of these crystallites and contact angle) were investigated to determine the pH sensor applicability of the CuS membranes deposited by CO2 laser beam. The CuS membrane deposited onto glass substrate showed the optimum pH sensing performance: 31.7 mV/pH with linearity of 99.56% & hysteresis 1.65 mV (pyrolytic process), and 40 mV/pH with 97.78% & hysteresis 0.53 mV (photolytic process), respectively.
Pub.: 06 Mar '17, Pinned: 28 Jul '17