Preparation and characterization of ZrO 2 thin film on sulfonated self-assembled monolayer of 3-mercaptopropyl trimethoxysilane

Abstract

Silane coupling reagent (3-mercaptopropyl trimethoxysilane (MPTS)) was prepared on single-crystal Si substrate to form two-dimensional self-assembled monolayer (SAM) and the terminal SH group in the film was in situ oxidized to SO 3H group to endow the film with good chemisorption ability. Thus, ZrO 2 thin film were deposited on the oxidized MPTS-SAM, by enhanced hydrolysis of zirconium sulfate (Zr(SO 4) 2·4H 2O) solution in the presence of HCl at 70 °C, making use of the chemisorption ability of the SO 3H group. The thickness of the films was determined with an ellipsometer, while the chemical feature, phase composition, thermal stability, and morphology of the films were analyzed by means of Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, and atomic force microscopy. As the results, the as-deposited ZrO 2 film was composed of nanocrystalline tetragonal ZrO 2 (t-ZrO 2) and an amorphous basic zirconium sulfate. The annealing of the films at 500 °C led to crystallization to t-ZrO 2, while further heating to 800 °C eliminated S in the film, and the ZrO 2 film consisted of nanocrystalline tetragonal ZrO 2 and monoclinic ZrO 2 in this case. The as-deposited ZrO 2 thin films were compact and crack-free, showing quadratically-looking features which were not observed previously, while the thickness of the ZrO 2 films decreased with increasing annealing temperature. Since the ZrO 2 film was well adhered to the MPTS-SAM, it might find promising application in the surface-modification of single-crystal Si and SiC in microelectromechanical systems (MEMS).