Lin-Lung Wei

2H-silicon carbide epitaxial growth on c-plane sapphire substrate using an AlN buffer layer and effects of surface pre-treatments

The effects of surface pre-treatments and the role of an AlN buffer layer for 2H-SiC growth on c-plane sapphire substrates by thermal CVD are investigated. While the crystallinity of SiC directly grown on sapphire substrate always degrades with a hydrogen pre-treatment but improves by optimizing carbonization, the crystallinity of SiC grown on sapphire substrate using an AlN buffer grown by MOCVD improves with sufficient time of exposure to the H pre-treatment but always deteriorates with carbonization. Detailed microstructural analysis by phi-scan x-ray diffraction reveals that SiC film grown on sapphire substrate consists of crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60°. A highly oriented hexagonal 2H-SiC film is obtained on low-cost c-plane sapphire substrate by using an AlN buffer. 2H-SiC is unambiguously determined not only by phi-scan x-ray diffraction but also by high-resolution transmission electron microscopy. The growth relationship between 2HSiC and 2H-AlN are coherent due to the favorable bonding of C and Al between SiC and AlN.

Wafer size MOS 2 with few monolayer synthesized by H 2 S sulfurization

Wafer sized, high quality continuous films would be a key demand for MoS<inf>2</inf> implemented in circuit application. In this study, the growth of few monolayer Mo<inf>S2</inf> on 4 inches SiO<inf>2</inf>/Si substrate were demonstrated. The MoS<inf>2</inf> thin films were synthesized by sulfurized in a furnace from the ultra-thin MoO<inf>3</inf> starting materials by using H<inf>2</inf>S. The obtained MoS<inf>2</inf> thin film examined by Raman analysis and Photoluminescence (PL), shows the semiconductor nature with direct transition peaks of 1.86 eV and 1.99 eV. The 4∼5 monolayer of MoS<inf>2</inf> with thickness around 2.6 nm is confirmed by cross-sectional view of transmission electron microscopy (TEM). Additionally, the DC characteristics of MoS<inf>2</inf> MOSFETs exhibit at least 2 order in on/off current ratio, demonstrating the feasibility for circuit application.

Post sulfurization effect on the MoS2 grown by pulsed laser deposition

Two inches size with high quality layered growth of MoS₂ was achieved by PLD on c-plane sapphire substrate. 2~3 monolayer MoS₂ was obtained within 2 inches wafer estimated from Raman analysis and confirmed by cross-sectional view of TEM. Additionally, the oxide states of Mo 3d core level spectra of MoS₂, analyzed by XPS, can be effectively reduced by adopting a post sulfurization process in H₂S. The post process also improve the photoluminescence (PL) of MoS₂ as well as the electrical characteristic of MoS₂ FET due to elimination the Mo oxide in the grown film.

Orientations of ZnO grown on GaN(10 1̄1): Orientations of ZnO grown on GaN(10 1̄1)

On semipolar epitaxial ZnO grown by chemical vapor deposition consists of two distinct orientations as evidenced by transmission electron microscopy and X-ray diffraction. The initially grown ZnO on GaN follows the GaN lattice with the epitaxial relationship of // and The other oriented ZnO domains then grow on faceted with and with good coherency with the -oriented grains. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Orientations of ZnO grown on GaN(10(1)over-bar1)

On semipolar epitaxial ZnO grown by chemical vapor deposition consists of two distinct orientations as evidenced by transmission electron microscopy and X-ray diffraction. The initially grown ZnO on GaN follows the GaN lattice with the epitaxial relationship of // and The other oriented ZnO domains then grow on faceted with and with good coherency with the -oriented grains. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Orientations of ZnO grown on GaN

On semipolar epitaxial ZnO grown by chemical vapor deposition consists of two distinct orientations as evidenced by transmission electron microscopy and X-ray diffraction. The initially grown ZnO on GaN follows the GaN lattice with the epitaxial relationship of // and The other oriented ZnO domains then grow on faceted with and with good coherency with the -oriented grains. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Orientations of ZnO grown on GaN(10 1̄1)

On semipolar epitaxial ZnO grown by chemical vapor deposition consists of two distinct orientations as evidenced by transmission electron microscopy and X-ray diffraction. The initially grown ZnO on GaN follows the GaN lattice with the epitaxial relationship of // and The other oriented ZnO domains then grow on faceted with and with good coherency with the -oriented grains. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)