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  1. Article ; Online: A Synchrotron Radiation Photoemission Study of SiGe(001)-2×1 Grown on Ge and Si Substrates

    Yi-Ting Cheng / Hsien-Wen Wan / Jueinai Kwo / Minghwei Hong / Tun-Wen Pi

    Nanomaterials, Vol 12, Iss 1309, p

    The Surface Electronic Structure for Various Ge Concentrations

    2022  Volume 1309

    Abstract: Beyond the macroscopic perspective, this study microscopically investigates Si 1−x Ge x (001)-2×1 samples that were grown on the epi Ge(001) and epi Si(001) substrates via molecular-beam epitaxy, using the high-resolution synchrotron radiation ... ...

    Abstract Beyond the macroscopic perspective, this study microscopically investigates Si 1−x Ge x (001)-2×1 samples that were grown on the epi Ge(001) and epi Si(001) substrates via molecular-beam epitaxy, using the high-resolution synchrotron radiation photoelectron spectroscopy (SRPES) as a probe. The low-energy electron diffraction equipped in the SRPES chamber showed 2×1 double-domain reconstruction. Analyses of the Ge 3d core-level spectra acquired using different photon energies and emission angles consistently reveal the ordered spots to be in a Ge–Ge tilted configuration, which is similar to that in epi Ge(001)-2×1. It was further found that the subsurface layer was actually dominated by Ge, which supported the buckled configuration. The Si atoms were first found in the third surface layer. These Si atoms were further divided into two parts, one underneath the Ge–Ge dimer and one between the dimer row. The distinct energy positions of the Si 2p core-level spectrum were caused by stresses, not by charge alternations.
    Keywords SiGe(001)-2×1 ; synchrotron radiation photoemission ; Si(001)-2×1 ; Ge(001)-2×1 ; low-energy electron diffraction ; Chemistry ; QD1-999
    Subject code 530
    Language English
    Publishing date 2022-04-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Microscopic Views of Atomic and Molecular Oxygen Bonding with epi Ge(001)-2 × 1 Studied by High-Resolution Synchrotron Radiation Photoemission

    Yi-Ting Cheng / Hsien-Wen Wan / Chiu-Ping Cheng / Jueinai Kwo / Minghwei Hong / Tun-Wen Pi

    Nanomaterials, Vol 9, Iss 4, p

    2019  Volume 554

    Abstract: In this paper, we investigate the embryonic stage of oxidation of an epi Ge(001)-2 × 1 by atomic oxygen and molecular O 2 via synchrotron radiation photoemission. The topmost buckled surface with the up- and down-dimer atoms, and the first subsurface ... ...

    Abstract In this paper, we investigate the embryonic stage of oxidation of an epi Ge(001)-2 × 1 by atomic oxygen and molecular O 2 via synchrotron radiation photoemission. The topmost buckled surface with the up- and down-dimer atoms, and the first subsurface layer behaves distinctly from the bulk by exhibiting surface core-level shifts in the Ge 3d core-level spectrum. The O 2 molecules become dissociated upon reaching the epi Ge(001)-2 × 1 surface. One of the O atoms removes the up-dimer atom and the other bonds with the underneath Ge atom in the subsurface layer. Atomic oxygen preferentially adsorbed on the epi Ge(001)-2 ×1 in between the up-dimer atoms and the underneath subsurface atoms, without affecting the down-dimer atoms. The electronic environment of the O-affiliated Ge up-dimer atoms becomes similar to that of the down-dimer atoms. They both exhibit an enrichment in charge, where the subsurface of the Ge layer is maintained in a charge-deficient state. The dipole moment that was originally generated in the buckled reconstruction no longer exists, thereby resulting in a decrease in the ionization potential. The down-dimer Ge atoms and the back-bonded subsurface atoms remain inert to atomic O and molecular O 2 , which might account for the low reliability in the Ge-related metal-oxide-semiconductor (MOS) devices.
    Keywords Ge(001)-2 × 1 ; oxidation ; synchrotron radiation photoemission ; Chemistry ; QD1-999
    Subject code 530
    Language English
    Publishing date 2019-04-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Epitaxy from a Periodic Y–O Monolayer

    Minghwei Hong / Chao-Kai Cheng / Yen-Hsun Lin / Lawrence Boyu Young / Ren-Fong Cai / Chia-Hung Hsu / Chien-Ting Wu / Jueinai Kwo

    Nanomaterials, Vol 10, Iss 1515, p

    Growth of Single-Crystal Hexagonal YAlO 3 Perovskite

    2020  Volume 1515

    Abstract: The role of an atomic-layer thick periodic Y–O array in inducing the epitaxial growth of single-crystal hexagonal YAlO 3 perovskite (H-YAP) films was studied using high-angle annular dark-field and annular bright-field scanning transmission electron ... ...

    Abstract The role of an atomic-layer thick periodic Y–O array in inducing the epitaxial growth of single-crystal hexagonal YAlO 3 perovskite (H-YAP) films was studied using high-angle annular dark-field and annular bright-field scanning transmission electron microscopy in conjunction with a spherical aberration-corrected probe and in situ reflection high-energy electron diffraction. We observed the Y–O array at the interface of amorphous atomic layer deposition (ALD) sub-nano-laminated (snl) Al 2 O 3 /Y 2 O 3 multilayers and GaAs(111)A, with the first film deposition being three cycles of ALD-Y 2 O 3 . This thin array was a seed layer for growing the H-YAP from the ALD snl multilayers with 900 °C rapid thermal annealing (RTA). The annealed film only contained H-YAP with an excellent crystallinity and an atomically sharp interface with the substrate. The initial Y–O array became the bottom layer of H-YAP, bonding with Ga, the top layer of GaAs. Using a similar ALD snl multilayer, but with the first film deposition of three ALD-Al 2 O 3 cycles, there was no observation of a periodic atomic array at the interface. RTA of the sample to 900 °C resulted in a non-uniform film, mixing amorphous regions and island-like H-YAP domains. The results indicate that the epitaxial H-YAP was induced from the atomic-layer thick periodic Y–O array, rather than from GaAs(111)A.
    Keywords interfacial monolayer-induced epitaxy ; atomic layer deposition ; laminated multilayers ; hexagonal perovskite YAlO 3 ; oxide/semiconductor hetero-structure ; gallium arsenide ; Chemistry ; QD1-999
    Subject code 669
    Language English
    Publishing date 2020-08-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Atomic Nature of the Growth Mechanism of Atomic Layer Deposited High‑κ Y2O3 on GaAs(001)‑4 × 6 Based on in Situ Synchrotron Radiation Photoelectron Spectroscopy

    Chiu-Ping Cheng / Wan-Sin Chen / Yi-Ting Cheng / Hsien-Wen Wan / Cheng-Yeh Yang / Tun-Wen Pi / Jueinai Kwo / Minghwei Hong

    ACS Omega, Vol 3, Iss 2, Pp 2111-

    2018  Volume 2118

    Keywords Chemistry ; QD1-999
    Language English
    Publishing date 2018-02-01T00:00:00Z
    Publisher American Chemical Society
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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    Inter-library loan at ZB MED

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