Comparative studies of sol-gel SiO 2 thin films prepared by spin-coating and dip-coating techniques

Silicon dioxide (SiO₂) film is an important material for semiconductor industry as the gate dielectric material, and optical industry as antireflective coatings, and so on. The sol-gel method has been widely used for the deposition of oxide thin films due to several advantages such as simple and low-cost equipment, normal atmospheric conditions, and ease control of the precursor composition doping. In this work, SiO₂ thin film was deposited on BK7 glass substrate by spin-coating and dip-coating techniques, respectively. Three precursor concentrations were investigated, i.e., tetraethylorthosilicate (TEOS): ethanol: water= 1:7:7, 1:10:10 and 1:15:15 (molar ratio). X-Ray Diffraction spectrometry (XRD), scanning electron microscopy (SEM), and UV-VIS-NIR scanning spectrophotometry were used to characterize the crystallinity, morphological and optical properties of deposited SiO₂ thin films. Results show that all the SiO₂ thin films deposited by the spin-coating and dip-coating are amorphous. SEM analysis confirms that the deposited SiO₂ thin films have high surface quality and tight adherence with the substrate. The transmittance measurements indicate that dip-coated SiO₂ thin film from gel of low precursor concentration represents better transmittance than that from high concentrations at the range of 600-1200nm. SiO₂ thin film spin-coated from gel of high precursor concentration has better transmittance than that by dip-coating, but of opposite results for the films deposited from gels of low precursor concentrations.