Investigation of the transition of amorphous Ti-thiolate prepared by hybrid atomic layer deposition/molecular layer deposition into titanium disulfide ultrathin film

Abstract

Amorphous organic-inorganic hybrid thin films (Ti-thiolate) deposited on thermal SiO2 substrate by atomic layer deposition/molecular layer deposition are converted into textured titanium disulfide (TiS2) ultrathin films, of thickness down to 5.5 nm, upon annealing under Ar/H2 (5%) atmosphere at mild temperature (300°C). Two annealing strategies were investigated by in situ synchrotron x-ray fluorescence, allowing us to master the mineralization of the amorphous Ti-thiolate into titanium disulfide. Stoichiometry and crystallinity of the thin films were characterized by x-ray photoelectron spectroscopies, Raman scattering, and x-ray absorption at the S K-edge. Lamellar structure parallel to the substrate surface was observed by transmission electron microscopy.

Quantitative in situ synchrotron X-ray analysis of the ALD/MLD growth of transition metal dichalcogenide TiS2 ultrathin films

“…The ratio was calibrated using X-ray photoelectron spectroscopy (XPS/HAXPES) data of the reference stoichiometric TiS 2 sample. 65 The absence of Ti–S coordination peaks during the very first cycles in the Ti K-edge Fourier transform EXAFS spectra can be understood through Fig. 2c, where the ratios of the initial 10 cycles are shown, while the ratios of the full growth up to 40 cycles are presented in ESI Fig.…”

“…A similar S/Ti ratio has been previously reported for the growth of 60 cycles of ALD/MLD. 65 The small S/Ti ratio for the initial few cycles indicates a very small number of sulfur back scatterers; therefore, the Ti–S bonds are below the detection limit of the technique at the Ti K-edge.…”

“…Similar behavior was also reported for 80 ALD/MLD cycles in our previous report, where the loss of S was also observed using diffuse reflectance infrared Fourier transform spectroscopy through chemical modeling on silica beads during the annealing treatment of a 2-cycle ALD/MLD Ti thiolate. 65…”