A study of microstructural and optical properties of nanocrystalline ceria thin films prepared by pulsed laser deposition

Abstract

Thin films of cerium oxide (CeO 2) have been deposited on (100) Si substrates using pulsed laser deposition technique at various substrate temperatures from room temperature (RT) to 973 K at an optimized oxygen partial pressure of 3 Pa. Structural, morphological and optical properties have been carried out using X-ray diffraction (XRD), Raman, ellipsometry and atomic force microscopy techniques. XRD results showed that the deposited films are polycrystalline with cubic structure. At room temperature, the film showed preferred orientation along (111) plane, while at higher temperatures, it exhibited preferred orientation along (200). The crystallite sizes were calculated and were found to be in the range 17–52 nm. The texture coefficient for (200) reflection increased until 573 K, and then decreased in the temperature range 673–973 K. The Raman peak appeared at 463 cm − 1 due to the F 2g active mode also confirmed the formation of CeO 2 with a cubic structure. There was a systematic variation in the Raman peak intensity, frequency shift and line broadening with the increase of temperature. The ellipsometry studies showed that the refractive index and band gap increased from 2.2 to 2.6 and 3.4 to 3.6 eV, respectively with increasing substrate temperature from RT to 973 K.