Optical properties of solution-processed LaAlOx/Si films using spectroscopic ellipsometry

Abstract

The dielectric functions, ε, of amorphous LaAlOx (LAO) films grown by the sol–gel process are investigated using spectroscopic ellipsometry. The LAO precursor sols are prepared at a molar ratio of La:Al = 1:1 with different mole concentrations to control the film thickness. The films are deposited on p-type Si substrates treated with dilute HF, and the sols are sintered at 400 °C for 2 h in an ambient atmosphere. Room-temperature pseudodielectric function spectra, ⟨ε⟩, are obtained from 0.7 to 8.6 eV, and best fits of the data are obtained with the Tauc–Lorentz (TL) model. The authors observe an increase in both the real and imaginary parts of ε, a decrease in the TL threshold energy Eg, and an increase in film thickness with increasing mole concentration of the precursor solution.