Jia Hua Min

Characterization of Ag doped P-type ZnO thin films prepared by electrostatic-enhanced ultrasonic spray pyrolysis

In this paper, the structure, electrical and optical properties and stabilities of Ag doped p-type ZnO thin films, prepared by electrostatic-enhanced ultrasonic spray pyrolysis were investigated. XRD and Hall data analyses indicated that the resistivity of 4at. % Ag doped p-type ZnO was low, without Ag2O phase separation. The optical transmission spectra illustrated that optical band gaps decreases with the gradual increase of Ag dopant. Moreover, ZnO: Ag films placed for 10 days still showed p-type, but the optical transmittance decreased, suggesting that AgZn in the ZnO: Ag thin films captured electrons to generate Agi, which reunited to be Ag nano-particles and decreased the optical transmittance of ZnO: Ag.

Sensitivity to NO2 of ZnO Film Prepared by Electrostatic-Enhanced Ultrasonic Spray Pyrolysis

The NO2-sensing properties of the ZnO films prepared by EUSP were investigated. Effect of substrate temperature on the NO2-sensing properties of ZnO films showed that the powder-like ZnO film deposited at 550°C was more sensitive to NO2, and the film illustrated good response-restoration property. Besides, the influence of doping amount on the NO2-sensing properties of the ZnO films at 260°C showed that the ZnO:Al film with the Al content of 0.4mol% presented the best sensitivity, and the ZnO: 3mol % Ag exhibited the highest NO2 sensitivity. The dynamic response tests indicated that the ZnO: Al film was of the highest sensitivity to NO2, and the sensitivity of ZnO: Ag film was lowest.

The Optical Properties and the Structure of CuInS2 Thin Films Deposited by Oblique Angle Deposition Technique

The oblique angle deposition (OAD) technique was used to deposit copper indium disulfide (CuInS2) films onto glass substrates by a vacuum thermal evaporation method. The powder source used in this work was obtained from the crushed CuInS2 polycrystalline ingot grown by Vertical Bridgeman method. In order to study the influences of depositing angle on the optical property and the structure of the CuInS2 films, the depositing angle θ was varied from 10° to 70° with a 30° gradient. These films were characterized by SEM, XRD and UV-Vis spectrophotometer. The results showed that the optical property and the structure of the films were closely related to the depositing angle θ. When the depositing angle θ increased, the band gap increased and the intensity of (112) characteristic peak of the CuInS2 films decreased.

Te Inclusions in CdMnTe Crystal Grown by the Traveling Heater Method and their Effects on the Electrical Properties

The concentration and size distribution of Te inclusions in CdMnTe (CMT) are key factors in nuclear devices performance. High-concentration and large-size Te inclusions degrade the performance drastically, especially for electrical properties. In this paper, the Te inclusions along the axial and radial directions in CMT crystal grown by the Traveling Heater Method (THM) were revealed by Infrared Microscopic System. The size of Te inclusions is 5-17 μm and the concentration is (2.5-4.6) ×105 cm-3. The Current-Voltage measurements were performed and the resistivity of the CdMnTe crystal with excess Te was in the range of 108-109 Ωcm, and the correlation between the Te inclusions and resistivity was investigated. The large size (>17 μm) and high concentration (4.5 of ×105 cm-3) Te inclusion decrease the resistivity of the CMT crystal seriously.

The Preparation and Optical Properties of Ag/ZnO Composite Materials

A simple, two-step fabrication technique was presented to prepare the Ag/ZnO hybrid nanostructures using silver nitrate and zinc nitrate. Silver particles were synthesized by chemical reduction method and the ZnO layer was coated on the surface of silver using wet chemical method. The microstructure, the composition and the optical properties of the obtained materials were further characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence (FL) spectroscopy. The results showed that the silver and zinc oxide composite had been successful prepared. The intensity of fluorescence showed an enhancement of R6G (dye) indicate that ZnO shell had an improvement on the silver metal enhance fluorescence.

Microstructure and Electrical Characterization of In-Doped Cd0.9Mn0.1Te Crystal Grown by the Vertical Bridgman Method

CdMnTe is one of the key materials for room temperature X-ray and gamma-ray detectors on Environmental Analysis and Monitoring. In this paper, the homogeneous Cd1-xMnxTe (x = 0.1) single crystal ingot was grown by the vertical Bridgman method. The compositional analysis was carried out by SEM/EDS. The Te inclusions were revealed by the IR transmission spectra. In dopant distribution was determined by ICP-AES measurement. The resistivity of CdMnTe was cha-racterized by I-V method. It was found that the segregation coefficient of Mn was 0.97. In dopant contents within 3 to 21 ppm of the ingot were found. The Te inclusions were mainly 8.2-28.3m in size and 1×105-1.5×107cm-3in concentration. I–V measurement reveals that sputtered Au film can form good ohmic contact and all the slices have the resistivity within 107 to 109Ωcm.

Growth and Characterization of CdZnTe Bulk Crystals Grown by Temperature Gradient Solution Growth

CdZnTe bulk crystals were grown by temperature gradient solution growth (TGSG) method with the lower starting growth temperature of 1223K, temperature gradient of 20-30 K/cm and a crucible dropping rate varied from 1 to 0.6 mm/h. Optical microscope, IR microscope, I-V characteristics and FTIR transmission spectroscopy were employed to analyze the growth interfaces, Te inclusions, resistivity and IR transmittance respectively. The results indicate that a smooth and uniform growth interface has been achieved. The density of Te inclusions is about 7.9-9.5×103 cm-2, while the resistivity is higher than 6.87×109 Ωcm and the IR transmittance is about 55-60%.

Characterization of Indium-Doped CdZnTe Crystal Grown under Te-Rich Conditions

CdZnTe (CZT) crystals with a diameter of 52 mm was grown using low pressure Bridgman method and were indium-doped under Te-rich conditions. Results showed the Te concentration was almost the same in different part of the as-grown ingot. Through IR transmission, Te inclusion with regular triangular or circular shapes could be observed, and the size of Te inclusion was around 7 µm and the concentration was 1.5  105 cm-3 for the CZT in the middle part of the ingot. I-V characteristic showed a good linear behavior with a resistivity of ~1010 Ω•cm.

Photoluminescence and Raman Scattering of Cu-N Codoped ZnO Thin Films

Polycrystalline ZnO thin films codoped with Cu and N have been obtained by chemical bath deposition. The effect of N incorporation and Cu-N incorporation on microstructure and optical properties of ZnO films has been investigated. X-ray diffraction patterns of the films indicated N incorporation deteriorated the crystalline quality while Cu-N incorporation improved the crystalline quality. The PL spectra showed that the relative intensity between the ultraviolet luminescence and the deep level-center luminescence of ZnO thin films was clearly correlated with the crystalline quality. Furthermore, the Raman spectra revealed the intensity of E2 (high) increase with Cu-N incorporation.

Interface Properties of Au/CdZnTe Formed by Different Method

In this paper, the effects of different metal contact treatments were systemically investigated. The interfacial properties between Au and CdZnTe (CZT) made by different methods including the electroless deposition, thermal evaporation and sputtering process were investigated by the Auger depth profiles, the adhesion force measurement, and the accelerated aging tests. The current-voltage (I-V) characteristics and the detector response to gamma-rays from 241Am for different Au contact treatments were also identified.