Growth and properties of SnO2 thin films obtained by spray pyrolysis technique

SnO2 (Tin oxide) metal oxide is considered as one of the most investigated II-VI semiconductor in modern microelectronic technology. Several techniques have been used to deposit SnO2 thin films. Among them, spray pyrolysis has proved to be simple, inexpensive and allows the control of many films parameters. In this work, various parameters of the spray pyrolysis technique are optimized to obtain SnO2 thin films. The starting solution molarity M and the deposition temperature T-d are fixed at 0.075 M, 0.1 M and T-d=350 degrees C, 400 degrees C, respectively. To investigate the films properties, structural, morphological and optical characteristics using X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), Atomic Force Microscopy (AFM) and UV-Visible spectrophotometry are studied respectively. XRD measurements show that SnO2 thin deposited films are polycrystalline with a typical tetragonal structure, except the 350 degrees C-0.075 M film, which shows a beginning of crystallization. SEM and AFM micrographs reveal rough and porous films surfaces with an agglomeration effect of nanoparticles that do not exceed 20 nm. EDX analysis confirms the chemical composition of pure SnO2. Optical characterization shows that absorption peaks decrease strongly from near UV to visible wavelength while a slow decrease of absorption is observed in the visible-IR range. Moreover, a large band gap E-g for all deposited films is estimated.