Growth of ZrO2 films on mesoporous silica sieve via atomic layer deposition

Abstract

The atomic layer deposition of ZrO2 thin films over the mesopores of a mesoporous silica sieve, SBA-15 (Santa Barbara Amorphous-15), using the tetrakis(dimethylamino)zirconium(IV) (TDMAZ) as ZrO2 precursor was tested and characterized using N2 adsorption-desorption isotherms, taking advantage of the well-defined shape and size distribution of the pores in the SBA-15. Three samples were prepared, using 2, 4, and 6 deposition cycles to control the thickness of the films. It was determined that, as the average size of the pores decreased (with the increasing number of cycles), their size distribution remained narrow, indicating a homogeneous distribution of the ZrO2 throughout the surfaces of the SBA-15 pores. This conclusion was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy. The deposition rate appears to slow down after 4 cycles, an observation that we explain by different chemisorption properties of TDMAZ molecules over SBA-15 and ZrO2 surface and by relating the kinetic diameter of TDMAZ with the pore diameter of SBA-15 after 4 deposition cycles: mass transport limitations have become significant at this point. They may be affected by complex factors like electronic effects caused by exposed ZrO2 surface and the multi-directional adsorption of precursor molecules in the pore walls.