Real-time spectroscopic ellipsometry as a characterization tool for oxide molecular beam epitaxy

A real-time spectroscopic ellipsometer (RTSE) was designed and implemented on an oxide molecular beam epitaxy (MBE) system. The RTSE was designed as a complementary tool to the other existing in situ deposition monitors on the MBE. To quantify how the RTSE complemented the other tools (as well as to determine its limitations), the RTSE was used to characterize the deposition of (111)-oriented $Y2O3$ on (111) Si and (110)-oriented $Y2O3$ on (100) Si. Results from computer modeling of the RTSE data subsequent to deposition showed excellent agreement with atomic absorption flux measurements, quartz crystal monitor flux measurements, reflection high energy electron diffraction measurements, and Rutherford backscattering spectroscopy. From the RTSE measurements, growth rates and microstructures were determined and verified by ex situ techniques. In addition, the sticking coefficient of yttrium to $Y2O3$ was found to be 1.00±0.07. Also, the temperature dependent optical properties of the $Y2O3$ films were measured at 25 and at $730 °C.$ Nearly bulk values were found, indicating the high quality films deposited via this method.