Fabrication And Properties Of CeO₂ Thin Film On Si Substrate By Pulsed Laser Deposition

Cerium oxide has a face-centered cubic fluorite crystal structure and is the ideal SOI insulation materials due to its high chemical stability, good thermal conductivity. In addition, films of CeO2 also have potential applications as high-k materials and optical films. In this paper, CeO2 films have been grown on Si(100) and Si(111) substrates. The main contents of the work are as follow:1) CeO2 films have been grown on Si(100) by PLD using Ce target and CeO2 ceramic target. The structural characteristics of CeO2 thin films have been characterized by X-ray Diffraction (XRD), Reflection High-energy Electron Diffraction (RHEED). Strong preference for CeO2(111)orientation thin films with perfect crystallinity and smooth surface was achieved. Crystallinity of the films was improved as the substrate temperature increased. Keithley4200 was used to analyze the electrical characteristics of the films, and the direct relationship between electrical characteristics and crystallinity was certificated. Based on the AFM analysis, all the RMS of the films deposited at different temperatures were about 0.3nm (using CeO2 ceramic target),0.6nm (using Ce target) and almost independent with substrate temperature. Using Ce target, the orientation of the films was more sensitive to oxygen partial pressure. The optical properties of films were studied by the spectroscopic ellipsometry(SE) technique.The results show that refractive index of the films are about 2.4 (single crystal, n=2.40～2.56). High quality CeO2 films can be prepared by PLD and their optical properties are less sensitive to targets and deposition conditions.2) CeO2 films have been grown on Si(111) by PLD using CeO2 ceramic target. Strong preference for CeO2(111)orientation thin films with perfect crystallinity and smooth surface was achieved. High resolution transmission electron microscopy(HRTEM) results illustrate that the predominant orientation of the cubic phase CeO2 film grown at 600℃is (111)CeO2//(111)Si, the presence of twin in the film was indicate by FFT image. Electrical properties of the films which were grown on Si(111) are better than films that were grown on Si(100) with same deposition condition.Based on the experimental results, it can be concluded that targets, substrates and the condition of deposition all have great influence on the properties of CeO2 films.