Integrating RHEED-TRAXS and molecular beam epitaxy for real-time compositional control of functional oxide deposition processes

Abstract

Real-time chemical analysis during film growth by Molecular Beam Epitaxy (MBE) has been unattainable because traditional Ultra High Vacuum (UHV) tools such as X-ray Photoelectron Spectroscopy (XPS) or Auger electron spectroscopy (AES) cannot be used at pressures above 10-8 Torr, and MBE growth pressure are typically 10-6 to 10-5 Torr. Real-time chemical analysis and stoichiometry control is important, however, because stoichiometry changes of less than one percent in materials such as functional oxides can cause measurable changes in their physical properties. Indirect measurements of stoichiometry, such as surface Reflection High Energy Electron Diffraction (RHEED) pattern, are often misleading. RHEED - Total Reflection Angle X-ray Spectroscopy (RHEED-TRAXS) has been shown in this work to be a viable real-time relative stoichiometry analysis tool for MBE deposition processes. Despite the limitations in detecting low atomic number elements (Z12O19). While progress has been made through this work to qualify relative atomic ratio, real-time quantitative stoichiometry measurement still faces challenges.