Surface Studies of SrTiO₃ Films Grown by Hybrid MBE

Hybrid oxide molecular beam epitaxy (hMBE), where transition metal cations are delivered using a metal-organic precursor, has emerged as the state-of-the-art approach to the synthesis of electronic-grade complex oxide films. However, numerous questions remain regarding the mechanism of the growth process and the surface properties of the resulting films. To examine these properties, thin film SrTiO₃ (STO) was prepared by hMBE using a titanium tetraisopropoxide precursor for Ti delivery and an elemental Sr source on STO and (LaAlO₃)_0.3(Sr₂AlTaO₆)_0.7 substrates with varying Sr:Ti flux ratios. The grown samples are transferred to an appended x-ray photoelectron spectroscopy (XPS) system to the MBE under ultra high vacuum to analyse the surface properties. Ion scattering spectroscopy measurements were also performed in the same system to correlate the XPS data with the surface termination. To compare the results with previously reported bulk measurements, samples were also examined using Rutherford backscattering and x-ray diffraction. These studies help to explain the mechanisms of hMBE growth and the resulting surface structure of films grown within the MBE growth window.