Studies Of Microstructures And Photoelectric Characteristics Of Silicon-Based ZnO Films Prepared By Sol-Gel Method

In this paper, ZnO film has been deposited on the surfaces of p(100) Si substrate by the sol-gel method using a spinning coating technique, and the n-ZnO/p-Si heterojunction has been formed between the surfaces of n-ZnO and p-Si. The electrodes are baked by using silver paster in order to obtain good ohmic contact. The influence of the cleaning method of the silicon chips and the preparation procedures of the ZnO films on the quality of the films has been studied. The photoelectric characteristics and the variation of microstructure of the ZnO film with the annealing temperatures and the addition of Na, K, Mg into the ZnO films have been investiged. The experimental results are as follows:(1) SEM results indicate that the surface of ZnO film is uniform and the quality of the film is perfect.(2) The C-axis orientation and grain size of ZnO films are affected by the annealing temperature and time:with the annealing temperature increasing, grain size of ZnO increase and the C-axis orientation of the ZnO grain getting stronger.(3) XRD pattern of the Na-doped ZnO films show that the grain sizes of ZnO in the film doped with Na are bigger than that in the undoped film; with the content of Na increasing, the C-axis orientation of the ZnO grain getting stronger. The results of the measurements of positon lifetime and coincident Doppler broadening spectra show that the open volume of defect in the ZnO film doped with Na is larger than that in the undoped film.(4) XRD pattern of the K-doped ZnO films show that the unkonw phase occurring in the film when the content of K reaches2.0at%. The grain size of ZnO in the film doped with K is bigger than that in the undoped film. The grain size of ZnO in the film doped with2.0at%K is the smallest, while the grain size of ZnO in the film doped with7.4at%K is the biggest. The C-axis orientation of the ZnO grain getting the worst in the film doped with3.7at%K, while it getting the best in the film doped with7.4at%K. The results of the measurements of positon lifetime and coincident Doppler broadening spectra show that the open volume of defect in the ZnO film doped with K is larger than that in the undoped film.(5) XRD pattern of the Mg-doped ZnO films show that the grain size of ZnO in the film doped with1.0at%Mg is the smallest, while the grain size of ZnO in the film doped with2.0at%Mg is the biggest. The C-axis orientation of the ZnO grain of the film doped with Mg getting worse in comparison with that of the undoped film. The results of the measurements of positon lifetime and coincident Doppler broadening spectra show that the open volume of defect in the ZnO film doped with Mg is larger than that in the undoped film. (6) The PL spectrum of ZnO indicates that ZnO film not only emit an ultraviolet peak of384.2nm with a FWHM of20.3nm but also emit a strong red peak of649.2nm with a FWHM of214nm, the ratio of the heights of the two peaks is0.934.(7) A remarkable photovoltaic effect has been found in the ZnO film deposited on p-Si substrate under the illumination of a red light with a wave length of632.8nm from a He-Ne laser. The photovoltaic property and the Ⅰ-Ⅴ characteristics curves of the n-ZnO/p-Si heterojunction, which measured under the dark field or under light illumination with the same intensity by an incandescent lamp and He-Ne laser, respectively, are very similar with that of a diode.(8) As the thickness of the ZnO film increasing, the n-ZnO/p-Si heterojunction exhibits a relatively stonger effect of the photovoltaic and the Ⅰ-Ⅴ characteristics.