Wafer-scale fabrication of conformal atomic-layered TiO_2 by atomic layer deposition using tetrakis (dimethylamino) titanium and H_2O precursors

摘要

The synthesis of ultra-thin atomic-layered oxides with precise thickness controllability and excellent uniformity remains a significant challenge in the fields of photovoltaics and opto-electronics. The wafer-scale synthesis and conformal growth of atomic-layered TiO2 film on Si/SiO2 substrate achieved by the atomic-layer deposition (ALD) using tetrakis (dimethylamino) titanium (TDMAT) precursor and H2O as an oxidation agent. Spectroscopic ellipsometry and atomic force microscopy (AFM) studies confirmed the conformal growth of TiO2 layer with the average thickness of similar to 037 +/- 0.04 nm over 4-inch Si/SiO2 wafer. Atomic-layered TiO2 films were obtained by the careful selection of the deposition temperature and the number of precursor's cycles, which were summarized into developed recipe. Fourier transform infrared (FTIR) spectroscopy revealed the vibration mode of Ti-O-Ti and Ti-O-Si on the deposited film confirming the development of structural bonding between ALD-developed TiO2 layer and Si/SiO2 substrate. In-situ X-ray diffraction (XRD) measurement showed the crystalline structure of developed film. It was confirmed that postdeposition annealing of TiO2 films improved their electrical conductivity. In particular, the atomic-layered TiO2 films annealed at 150 degrees C demonstrated that their bandgap has been widen to 3.37 eV compare to the previously reported values for bulk rutile (3.03 eV) and anatase (3.20 eV). (C) 2017 Elsevier Ltd. All rights reserved.