Effect of Substrate Texture on Orientations of rf‐Sputtered Ba ₂ Si ₂ TiO ₈ Thin Films

Abstract

Radio‐frequency‐sputtered barium silicon titanate, Ba 2 Si 2 TiO 8 (BST), thin films were grown on various substrates at substrate temperatures ranging from 750° to 955°C. The asdeposited films were characterized using X‐ray diffraction, optical microscopy, and scanning electron microscopy (SEM). The results of the morphology analysis and X‐ray diffraction analysis show no crystalline structure for films deposited on the fused quartz and unetched Si (100) substrates at temperatures lower than 865°C. At a substrate temperature of 900°C, tiny tetragon‐like grains were observed for the film grown on the fused quartz, and the grains grew at a rate of 0.18 μm/min in the initial deposition stage. Optical and SEM micrographs reveal (001)‐oriented, tetragon‐like grains grown on HF‐etched Si (100) wafers in the initial deposition stage and in later stages at substrate temperatures from 822° to 865°C. The results of X‐ray diffraction analysis show a high (001) orientation for the thicker films, which corresponds to the tetragon‐like configuration of the grains in the initial stage. Triangle‐like grains were observed on the films deposited on etched Si (111) substrates in a temperature range from 822° to 899°C, but the grain configuration changed from the initial triangle shape to a tetragon shape as the films grew thick. The X‐ray diffraction spectra show a high (001) orientation for the thicker films, which indicates an orientation transformation during the deposition due to a very low interfacial energy between the (001)‐oriented BST overgrowth and the BST substrates in the later stage of deposition. Both the tetragon‐like and the triangle‐like grains have quasi‐two‐dimensional polygon shapes and have nonliquid‐like characteristics in coalescence, which suggests a strong interaction between the BST deposits and the Si substrates.