Nor Diyana Sin

Effects of annealing environments on the solution-grown, aligned aluminium-doped zinc oxide nanorod-array-based ultraviolet photoconductive sensor

We have fabricated metal-semiconductor-metal- (MSM-) type ultraviolet (UV) photoconductive sensors using aluminium- (Al-) doped zinc oxide (ZnO) nanorod arrays that were annealed in different environments: air, oxygen, or a vacuum. The Al-doped ZnO nanorods had an average diameter of 60 nm with a thickness of approximately 600nm that included the seed layer (with thickness ∼200 nm). Our results show that the vacuum-annealed nanorod-array-based UV photoconductive sensor has the highest photocurrent value of 2.43 × 10-4 A. The high photocurrent is due to the high concentration of zinc (Zn) interstitials in the vacuum-annealed nanorod arrays. In contrast, the oxygen-annealing process applied to the Al-doped ZnO nanorod arrays produced highly sensitive UV photoconductive sensors, in which the sensitivity reached 55.6, due to the surface properties of the oxygen-annealed nanorods, which have a higher affinity for oxygen adsorption than the other samples and were thereby capable of reducing the sensors dark current. In addition, the sensor fabricated using the oxygen-annealed nanorod arrays had the lowest rise and decay time constants. Our result shows that the annealing environment greatly affects the surface condition and properties of the Al-doped ZnO nanorod arrays, which influences the performance of the UV photoconductive sensors.

Effect of R.F Power to the Properties of ZnO Thin Films Deposited by Magnetron Sputtering

The effect of radio frequency (R.F) power to the properties of zinc oxide (ZnO) thin films deposited by magnetron sputtering is presented. This project has been focused on electrical, optical and structural properties of ZnO thin films. The effect of variation R.F power at 100 watt ~ 400 watt on the ZnO thin films has been investigated. The thin films were examined using current-voltage (I-V) measurement, UV-Vis-NIR spectrophotometer, x-ray diffraction (XRD) and atomic force microscope (AFM). ZnO thin films were prepared at room temperature in pure argon atmosphere by a R.F magnetron sputtering using ZnO target. I-V measurement indicates that at 300 watt R.F power show the highest conductivity. All films have showed high UV absorption properties using UV-VIS spectrophotometer (JASCO 670). Highly oriented ZnO thin films [002] direction was obtained by using Rigaku Ultima IV. The root means square (rms) roughness for ZnO thin film were about (<2nm) was measured using AFM (Park System XE-100). Keywords-ZnO thin films, R.F power, electrical properties, optical properties, structural properties

Thickness-Dependent Characteristics of Aluminium-Doped Zinc Oxide Nanorod-Array-Based, Ultraviolet Photoconductive Sensors

Aluminium (Al)-doped zinc oxide (ZnO) nanorod arrays were prepared on a seed-layer-coated glass substrate by a sonicated sol–gel immersion method. We have shown, for the first time, that the thickness of the nanorod arrays can be increased incrementally without greatly affecting the diameter of the nanorods, by increasing the number of immersions. The field-emission scanning electron micrographs and thickness measurements revealed that the nanorods had diameters within the range from 40 to 150 nm and thicknesses from 629 to 834 nm with immersion times ranging from 1 to 5 h. The photoluminescence (PL) spectra revealed that the ZnO nanorod quality was enhanced with long immersion times as shown by an improvement in the ratio of the UV peak intensity to the visible emission peak intensity, or IUV/Ivis. The thickness-dependent characteristic of Al-doped ZnO nanorod-array-based, UV photoconductive sensors was studied; minimising the thickness of the nanorod arrays was found to provide high responsivity and good performance. Our experiments showed that a decrease in the thickness of the nanorod arrays improved the responsivity and response time of the UV sensors, with a maximum responsivity of 2.13 A/W observed for a 629-nm-thick nanorod film.

Influence of Cubic Structured-ZnSnO3 Immersion Time to the Performance of Humidity Sensor

ZnSnO3 thin film was deposited at different deposition time (0.5 h, 2 h, 4 h and 6 h) using sol-gel immersion method and the electrical, optical and structural properties of this film was investigated. This research involved the preparation of nanostructured ZnO thin film by using RF magnetron sputtering, preparation of ZnSnO3 sol-gel solution, metal contact deposition and characterization of humidity sensor. The thin film was characterized using current-voltage (I-V) measurement (Keithley 2400) and field emission scanning electron microscopy (FESEM) (JEOL JSM 6701F) for electrical and structural properties respectively. The sensor was characterized using I-V measurement in a humidity chamber (ESPEC SH-261) and the chamber has been set at room temperature with varied relative humidity (% RH), in the range of 40-90% RH. The film prepared with a deposition time of 2 h shows better sensitivity for humidity sensor. The FESEM investigation shows that crystal size increases with the increasing deposition time.

Effects of Sn Dopant on Structural and Optical Properties of ZnO Thin Film Prepared by Sol-Gel Route

Tin doped zinc oxide (Sn:ZnO) thin films were prepared on glass substrates via sol-gel dip-coating technique starting from zinc acetate dehydrate, (CH3CO2)2Zn⋅2H2O and tin chloride, SnCl2. The consequences of various Sn doping on the behavior of the film was investigated. The atomic percentages of dopant in ZnO-based solution were [Sn4+]/[Zn2+] which is between 0% and 4%. The thin films were characterized using Field Emission Scanning Electron Microscope (FESEM) and UV-Vis-NIR spectrophotometer.

Humidity sensor-based zno/sno2 nanocomposite synthesised by sol-gel immersion method

ZnO/SnO2 nanocomposite was successfully prepared using sol-gel immersion method. The structural properties of ZnO/SnO2 nanocomposite were characterised using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. The optical properties was analysed by photoluminescence (PL). The sensing properties were measured using two point probe current-voltage (I-V) measurement. The sensor characteristics depend on the composition and surface morphology of the thin film. The sensor with ZnO/SnO2 nanocomposite performed the high sensitivity with 69 times from ratio of R40RH% to R90RH% at 25°C. The response and recovery times of ZnO/SnO2 nanocomposite was 290 s and 15 s respectively. The ZnO/SnO2 nanocomposite found to be good repeatability and reproducibility. The humidity sensing mechanism was summarised.

Effect of RF Power on the Formation and Morphology Evolution of ZnO Nanostructured Thin Films

The effect of RF power on the formation and morphology evolution of ZnO nanostructured thin films deposited by magnetron sputtering are presented. This project focused on electrical, optical and structural properties of ZnO thin films. The effect of variation of RF power at 50 watt-250 watt at 200 °C on glass substrate of the ZnO thin films was investigated. The thin films were examined for electrical properties and optical properties using two point probe current-voltage (I-V) measurement (Keithley 2400) and UV-Vis-NIR spectrophotometer (JASCO 670) respectively. The structural properties were characterized using field emission scanning electron microscope (FESEM) (JEOL JSM 7600F) and atomic force microscope (AFM) (Park System XE-100). The IV measurement indicated that at RF power 200 watt the conductivity of ZnO thin film show the highest. All films show high UV absorption properties using UV-VIS spectrophotometer (JASCO 670). The root means square (rms) roughness for ZnO thin film were about 4 nm measured using AFM. The image form FESEM observed that transformation of structure size started to change as the RF power increase.

Optimization of Nano-Process Deposition Parameters Based on Gravitational Search Algorithm

This research is focusing on the radio frequency (RF) magnetron sputtering process, a physical vapor deposition technique which is widely used in thin film production. This process requires the optimized combination of deposition parameters in order to obtain the desirable thin film. The conventional method in the optimization of the deposition parameters had been reported to be costly and time consuming due to its trial and error nature. Thus, gravitational search algorithm (GSA) technique had been proposed to solve this nano-process parameters optimization problem. In this research, the optimized parameter combination was expected to produce the desirable electrical and optical properties of the thin film. The performance of GSA in this research was compared with that of Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Artificial Immune System (AIS) and Ant Colony Optimization (ACO). Based on the overall results, the GSA optimized parameter combination had generated the best electrical and an acceptable optical properties of thin film compared to the others. This computational experiment is expected to overcome the problem of having to conduct repetitive laboratory experiments in obtaining the most optimized parameter combination. Based on this initial experiment, the adaptation of GSA into this problem could offer a more efficient and productive way of depositing quality thin film in the fabrication process.

Sensing Characteristics of PVA-ZnO/SnO2 Nanocube Humidity Sensor Prepared by Sol-Gel Immersion Technique

The effects of polyvinyl alcohol (PVA) loading in ZnO/SnO2 sol-gel immersion method were investigated. The sensor characteristic of in ZnO/SnO2 nanocube was also been tested. The images of sample were carrying out by field emission scanning electron microscopy (FESEM) (JEOL JSM 6700F). The optical properties were characterized using photoluminescent (PL). The thin films were characterized using two point current-voltage (I-V) measurement (Keithley 2400) for electrical properties. The sensor was characterized using I-V measurement in a humidity chamber (ESPEC SH-261) and the chamber has been set at room temperature at 25°C relative humidity (RH %) is varied in the range of 40% to 90 %RH. The FESEM indicate the agglomeration and porous increase as the insertion of PVA into in ZnO/SnO2 nanocube (PVA-ZnO/SnO2 nanocube) compare with the as prepared in ZnO/SnO2 nanocube. PL measurement of PVA-ZnO/SnO2 nanocube describe blue shift behaviour after mixed the PVA. The sensitivity of the sensor of PVA-ZnO/SnO2 nanocube and ZnO/SnO2 nanocube were ratio of current 3.24 times and 12.7 times. While the response and recovery times of PVA-ZnO/SnO2 nanocube higher response and recovery times as compare with ZnO/SnO2 nanocube.

Prediction of Nanostructured ZnO Thin Film Properties Based on Neural Network

An approach in the prediction of zinc oxide (ZnO) thin films properties based on neural network is presented in this paper. The research had been focused on the electrical properties of ZnO. The sputtering power, substrate temperature, deposition time and oxygen ratio were selected as the input variables while the resistivity and conductivity were selected as the output. The numerical results obtained through the neural network model were compared with the experimental results. The result obtained from the system model of the proposed procedure was reasonably good and promising. Therefore, the prediction based on neural network model is a reliable approach compared to the traditional method of trial-and-error process.