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We combine state-of-the-art oxide epitaxial growth by hybrid molecular beam epitaxy with transport, x-ray photoemission, and surface diffraction, along with classical and first-principles quantum mechanical modeling to investigate the nuances of insulating layer formation in otherwise high-mobility homoepitaxial n-SrTiO 3 (001) films. Our analysis points to charge immobilization at the buried n-SrTiO 3 /undoped SrTiO 3 (001) interface as well as within the surface contamination layer resulting from air exposure as the drivers of electronic dead-layer formation. As Fermi level equilibration occurs at the surface and the buried interface, charge trapping reduces the sheet carrier density ( n 2 D ) and renders the n-STO film insulating if n 2 D falls below the critical value for the metal-to-insulator transition. 

The ability to synthesize new materials with unique functionalities has provided the foundation for modern electronics and for new discoveries. Oxide molecular beam epitaxy (MBE) has played a vital role in this endeavor. In this chapter, key fundamental concepts discussing the physics of complex oxides, followed by the important role of oxide MBE, are presented. Recent technical advances, current and potential challenges, and advantages of an oxide MBE are reviewed. Important factors responsible for electronic-quality oxide films – including of those metals that are difficult to oxidize – are discussed, with particular emphasis on new developments with radical-based MBE approaches. Taking analogy from III–V MBE, the current status and future prospects of oxide MBE are discussed in developing oxide electronics operating at room temperature.