In Situ X-ray Fluorescence Measurements During Atomic Layer Deposition: Nucleation and Growth of TiO2 on Planar Substrates and in Nanoporous Films

Abstract

Synchrotron-based X-ray fluorescence (XRF) is introduced as a promising in situ technique to monitor atomic layer deposition cycle-per-cycle. It is shown that the technique is greatly suitable to study initial nucleation on planar substrates. The initial growth of TiO2 from tetrakis(dimethylamino)titanium (TDMAT) and H2O is found to be linear on thermally grown SiO2, substrate-inhibited on H-terminated Si and substrateenhanced on atomic layer deposited Al2O3. Furthermore, in situ XRF is employed to monitor the Ti uptake during deposition of TiO2 in nanoporous silica films. In mesoporous films, the Ti content varied quadratically with the number of cycles, a behavior that is attributed to a decreasing surface area with progressing deposition. In microporous films, the XRF data suggest that 1−3 ALD cycles shrunk the pore diameters below the kinetic diameter of the TDMAT molecule.