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The epitaxial crystallization of β-Ga2O3 thin films on NiO-buffered α-Al2O3(0001) substrates via the solid-phase crystallization of amorphous Ga2O3 thin films by KrF excimer laser annealing at room temperature (RT) was examined. The results of X-ray and reflection high-energy electron diffraction measurements indicated that the epitaxial β-Ga2O3 thin films were fabricated by RT laser annealing. The optical bandgap of the thin films was estimated to be 4.9 eV from the results of UV/vis transmittance measurements. In the cathodoluminescence spectrum, UV–green luminescence was observed for the thin films. These optical properties are similar to those of bulk β-Ga2O3.

Influence of the atomic-scale surface morphology of sapphire substrates on the epitaxial growth and crystallinity of Al 2 O 3 thin films was investigated by pulsed laser deposition (PLD) toward sapphire substrate engineering. Homoepitaxial growth of ¡-Al 2 O 3 thin films on R-plane sapphire (01 12) substrates with 0.35-nm-high atomic steps and approximately 20-nm-wide terraces was achieved at room-temperature (approximately 20°C) by PLD. Epitaxial growth of the ¡-Al 2 O 3 thin films was confirmed by in situ reflection high-energy electron diffraction (RHEED). The obtained epitaxial film surface was atomically stepped similar to the sapphire substrate before deposition.

Epitaxial growth of oxide films at lower temperatures is favored to obtain sharp interfaces and flat surfaces which are of advantage to construct high-quality electronic devices, and also is expected to result in novel development of unequilibrium structure and new electronic functionalization. Pulsed laser deposition (PLD) technique using laser ablation of a solid target is known to reduce the temperature drastically for epitaxial growth because of the highly energetic film precursors ablated from the target. In this article we briefly review the main achievements of our research group on room-temperature (RT, 20°C) synthesis of epitaxial oxide thin films by way of laser MBE process, i.e. PLD in ultrahigh vacuum. RT-epitaxial film growth by laser MBE and its electronic application were presented for some functional oxide thin films such as ZnO, Sn-doped In 2 O 3 (ITO), sapphire (¡-Al 2 O 3 ), (Li,Ni)O, or (Mg,Ni)O, and also magnetic functionalization via selective post-depositional reduction of complex oxide films was demonstrated.