摘要
Single-crystal metastable hexagonal perovskite YAlO 3 (H-YAP) films were epitaxially grown on GaAs(111)A by utilizing sub-nanolaminated (snl) and nanolaminated (nl) atomic layer deposited (ALD) Y 2 O 3 /Al 2 O 3 multilayers in situ on freshly prepared pristine molecular beam epitaxy (MBE) GaAs. We have studied and compared the structures of H-YAP between the snl-ALD and nl-ALD samples using synchrotron radiation X-ray diffraction (SR-XRD) and scanning transmission electron microscopy (STEM). The evolution of SR-XRD data under different annealing conditions suggested the lowest temperature of 900 °C for forming H-YAP. The observation of pronounced Pendellösung fringes indicated an excellent crystallinity of H-YAP and sharp H-YAP/GaAs interface despite an ∼8.4% large lattice mismatch between H-YAP and GaAs. Narrow full width at half-maximum (fwhm) ≈ 0.019° of H-YAP(0004) θ-rocking scan of the snl-ALD sample is close to that of substrate GaAs(111) ≈ 0.013° and 1 order of magnitude smaller than that of H-YAP(0004) of the nl-ALD sample ≈ 0.280°, indicating a better crystallinity of the former than that of the latter. STEM images revealed the formation of H-YAP starting from the GaAs surface instead of inside the multilayers. The oxide/GaAs interface remained very sharp after 900 °C annealing.