Structural, optical and electrical properties of nanocrystalline TiO2 -- HfO2 thin films
In the present work the properties of mixed HfxTi1-xO2 solid solution thin films in metal-oxide-semiconductor (MOS) configuration have been studied. Thin films, were grown on monocrystalline silicon substrates using the low pressure hot target reactive sputtering from the Ti:Hf mosaic target. From optical transmission measurements the 3.42 (eV) bandgap of the thin films has been estimated. Electrical characterization of the prepared MOS structures shows classical capacitance- and current-voltage behaviors indicating medium-k gate oxide properties with the low leakage current
Characterization of nanocrystalline TiO2–HfO2 thin films prepared by low pressure hot target reactive magnetron sputtering
Abstract Thin films of oxides were deposited by magnetron sputtering in reactive oxygen plasma from Ti–Hf mosaic target. The low pressure of reactive gas and appropriate power of plasma discharge during the deposition assumed pseudoepitaxial conditions of the layer growth. Thin films were characterized by means of X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and optical transmission. On the basis of obtained results it was stated that the fabricated thin films were composed of the stoichiometric HfTiO 4 single phase with average size of grains in the range of tenth of nanometers. Optical absorption spectra, derived in a conventional way from optical transmission measurements, yielded the optical band gap of about 3.42 eV. The grain size has changed after annealing in the range of 30 to 40 nm.
Influence of substrate temperature on atomic layer growth and properties of HfO2 thin films
Abstract Atomic layer growth of hafnium dioxide from HfCl4 and H2O has been studied at substrate temperatures ranging from 180–600°C. A quartz crystal microbalance was used for the real-time investigation of deposition kinetics and processes affecting the growth rate. It was shown that the layer-by-layer growth was self-limited at temperatures above 180°C. The data of ex situ measurements revealed that the structure, density and optical properties of the films depended on the growth temperature. The absorption coefficient of amorphous films grown at 225°C was below 40 mm−1 in the spectral range of 260–850 nm. The refractive index of the films grown at 225°C was 2.2 and 2.0 at 260 and 580 nm, respectively. The polycrystalline films with monoclinic structure grown at 500°C had about 5% higher refractive index but more than an order of magnitude higher optical losses caused by light absorption and/or scattering.