Zhuxi Fu

Green luminescent center in undoped zinc oxide films deposited on silicon substrates

The photoluminescence (PL) spectra of the undoped ZnO films deposited on Si substrates by dc reactive sputtering have been studied. There are two emission peaks, centered at 3.18 eV (UV) and 2.38 eV (green). The variation of these peak intensities and that of the I–V properties of the ZnO/Si heterojunctions were investigated at different annealing temperatures and atmospheres. The defect levels in ZnO films were also calculated using the method of full-potential linear muffin-tin orbital. It is concluded that the green emission corresponds to the local level composed by oxide antisite defect OZn rather than oxygen vacancy VO, zinc vacancy VZn, interstitial zinc Zni, and interstitial oxygen Oi.

The effect of Zn buffer layer on growth and luminescence of ZnO films deposited on Si substrates

The highly c-axis oriented ZnO films were deposited on Si substrates with Zn buffer layers. The intense cathodoluminescence, including UV, blue, and green emissions, was observed in these films at room temperature. According to X-ray diffraction analysis and cathodoluminescence spectra, it is found that the Zn buffer layer plays an important role for improving crystal quality of films and for getting intense cathodoluminescence.

Enhancement of ultraviolet emissions from ZnO films by Ag doping

The Ag-doped ZnO films were deposited on Si substrates by dc reactive sputtering. Obvious enhancement of ultraviolet (UV) emission of the samples was observed due to Ag2O nanoclusters formatted during Ag doping. The UV emission consisted of two peaks. The 348nm peak was attributed to Ag2O nanoclusters, and the 382nm one was attributed to ZnO. The strongest UV emission of a certain ZnO–Ag2O film was over ten times stronger than that of a pure ZnO film, which was an exciting result. The enhancement of UV emission was caused by excitons formed at the interface between Ag2O nanoclusters and ZnO grains.

Defect Photoluminescence of Undoping ZnO Films and Its Dependence on Annealing Conditions

The undoping ZnO emitting films were deposited on Si substrates by dc reactive sputtering. There are two peaks of photoluminescence (PL), centered at 3.18 eV (ultraviolet), and at 2.38 eV (green), to be observed in the samples. We investigated the dependence of PL spectra on annealing temperature and annealing atmosphere. According to the calculation of defect levels and the relationship between PL spectra and annealing conditions, we supposed that the green emission of ZnO films corresponds to the local level composed of the antisite defect O Zn .

Temperature-dependent photoluminescence of nanocrystalline ZnO thin films grown on Si (100) substrates by the sol–gel process

Temperature-dependent photoluminescence (PL) of nanocrystalline ZnO thin films grown on Si (100) substrates using a sol–gel method has been investigated. From the PL spectra measured in 83–293K, the excitonic emissions and their multiple-phonon replicas have been observed in ultraviolet region, and their origins have been identified. Moreover, it has been found that the temperature dependence of the free exciton peak position can be described by standard expression, and the thermal activation energy extracted from the temperature dependence of the free exciton peak intensity is about 101meV.

Cathodoluminescence of ZnO Films

The cathodoluminescence of ZnO films deposited on Si substrates by reactive dc sputtering is investigated. Apart from the characteristic green emission band (522 nm) of ZnO, an ultraviolet (392 nm) band and a blue (430-460 nm) band have been observed. The x-ray diffraction and cathodoluminescent spectra reveal the dependences of the luminescence on the preparation conditions and crystallinity of the ZnO films.

Photoluminescence and structure of ZnO films deposited on si substrates by metal-organic chemical vapor deposition

Abstract The structure and photoluminescence (PL) at room temperature of ZnO films deposited on Si(111) substrates by metal-organic chemical vapor deposition (MO-CVD) using diethylzinc (DEZ) and CO 2 was investigated. It was found that these properties strongly depend on growth temperature and pressure. ZnO films can be deposited only at low pressure and in the temperature region of 500–650°C. The samples grown at certain conditions can generate stronger luminescence of ZnO. When the growth temperature increased to 650°C, the ZnO 2 phase was observed in X-ray diffraction (XRD) patterns of the samples. This characteristic became evident after the samples annealed. Appearance of a ZnO 2 phase results in production of a new emission band centered at 575 nm in the PL spectrum at room temperature, and the green emitting band also disappears.

Fractal processing of AFM images of rough ZnO films

Fractal image processing has been applied to characterize the surface roughness of ZnO films as measured by atomic force microscopy. The simple fractal analysis suggests that the fractal dimension D can be used to describe the change of the whole grain morphology along the growth direction. Multifractal analysis shows that the scaling range is close to three orders of magnitude, which is larger than that of a simple fractal and most empirical fractals. The width of the multifractal spectrum can be used to characterize the roughness of the film surface quantitatively and the shape of multifractal spectrum can describe the ratio between the number of the lowest valleys and the highest peaks statistically.

Multifractal analysis and scaling range of ZnO AFM images

The surface topographies of as-sputtered and annealed ZnO films were measured by atomic force microscope (AFM). Multifractal behavior of AFM images has been analyzed by box-counting method. It is found that the scaling range can be extended from the image size to the smallest pixel (about 3 decades) by selecting an appropriate method for determining height probability and neglecting smallest probabilities (totally <0.2%) in several boxes. Multifractal spectra can be used to characterize the rough surface of thin film quantitatively.

UV LUMINESCENCE AND SPECTRAL PROPERTIES OF ZNO FILMS DEPOSITED ON SI SUBSTRATES

Abstract Cathodoluminescence and photoluminescence properties of ZnO films deposited on Si substrates are presented. The electronic states of the ZnO film are assigned by means of the reflection spectra and photoelectron spectra in UV–VUV region. The luminescence spectrum consists of two main emission bands peaking at 392 nm (UV) and 523 nm (green). Intensity of the UV band superlinearly increases with rising density of the electron beam, while intensity of the green band increases sublinearly.