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Molecular beam epitaxy (MBE) invented for the growth of compound semiconductors in the 70’s has been successfully extended to the advanced growth of metals, oxides, oxide/semiconductor interfaces and emergent topological materials by our endeavor in the past three and half decades. In the 80’s, Kwo et al. have invented metal MBE and oxide MBE methods in pioneering spintronics and high-temperature superconducting oxide films. In driving compound semiconductors for optoelectronics, Hong et al. have produced distributed Bragg reflectors with a continuously graded composition between each constituent without shutter operation, and greatly reduced the electrical resistance; this simple method has made easy manufacture of vertical-cavity surface-emitting lasers. In the 90’s, combining (In)GaAs and oxide MBE chambers via ultra-high vacuum, Hong et al. were the first to unpin the Fermi level in oxide/GaAs, which led to the first demonstration of inversion-channel (In)GaAs metal-oxide-semiconductor (MOS) field-effect transistors (MOSFETs). Integrating MBE, atomic layer deposition (ALD), and many other functions in ultra-high vacuum, advances have been made in pushing ultimate complementary MOS (CMOS) of record-high device performances and beyond in growing emergent topological materials for spintronics. Our novel method in preserving as-grown (In)GaAs surfaces and interfaces with high-κ oxides and metals enables employing in-situ synchrotron radiation photoemission to study electronic structures in an atomic scale.

Single crystals of YBa2Cu3O6 + δ, completely separated from flux, measuring up to 5–6 mm2 and 0.25–0.5 mm thick, were grown reproducibly from BaCuO2 solutions containing 0.8 wt% Ta2O5, by the top seeded solution growth technique. Addition of Ta increases the crystal size due to reduced nucleation. The crystals exhibit a broad superconducting transition at 80 K when annealed in air (a narrow transition at 86 K on oxygen annealing), attributed to the incorporation of stoichiometric excess of oxygen in the presence of Ta, as supported by the EDX, thermogravimetry and oxygen titration analysis.