Ching-Hung Hsiao

Catalyst-free growth of indium nitride nanorods by chemical-beam epitaxy

We demonstrate the growth of indium nitride (InN) nanorods on sapphire by chemical-beam epitaxy without a catalyst. The nanorods are synthesized nearly unidirectionally along the ⟨001⟩ direction and the diameters varied in the range of 20–40nm with In∕N flow ratio. Single-crystalline wurtzite structure is verified by x-ray diffraction and transmission electron microscopy. Raman measurements show that these wurtzite InN nanorods have sharp peaks E2 (high) at 491cm−1 and A1 (LO) at 593cm−1.

Plasma-Assisted Synthesis of High-Mobility Atomically Layered Violet Phosphorus

Two-dimensional layered materials such as graphene, transition metal dichalcogenides, and black phosphorus have demonstrated outstanding properties due to electron confinement as the thickness is reduced to atomic scale. Among the phosphorus allotropes, black phosphorus, and violet phosphorus possess layer structure with the potential to be scaled down to atomically thin film. For the first time, the plasma-assisted synthesis of atomically layered violet phosphorus has been achieved. Material characterization supports the formation of violet phosphorus/InN over InP substrate where the layer structure of violet phosphorus is clearly observed. The identification of the crystal structure and lattice constant ratifies the formation of violet phosphorus indeed. The critical concept of this synthesis method is the selective reaction induced by different variations of Gibbs free energy (ΔG) of reactions. Besides, the Hall mobility of the violet phosphorus on the InP substrate greatly increases over the theoretical values of InP bulk material without much reduction in the carrier concentration, suggesting that the mobility enhancement results from the violet phosphorus layers. Furthermore, this study demonstrates a low-cost technique with high compatibility to synthesize the high-mobility atomically layered violet phosphorus and open the space for the study of the fundamental properties of this intriguing material as a new member of the fast growing family of 2D crystals.

Growth of gallium nitride nanorods by metalorganic molecular beam epitaxy

Without a catalyst or template layer, high-quality GaN nanorods have been grown by rf radical source metalorganic molecular beam epitaxy on c-sapphire substrates. Scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX), and x-ray diffraction were employed to characterize the GaN nanorods. These nanorods have an average diameter of 50nm, and the rod areal density can reach 1×1010cm−2 depending on the growth parameters. High-resolution TEM results indicate that the well-aligned GaN nanorods have a single-crystal hexagonal wurtzite structure with preferential [0001] orientation, and no droplet was observed at the end of the nanorods. Meanwhile, EDX analysis revealed gallium and nitrogen as the only detectable elements. These high-quality and high-density GaN nanorods might be useful for practical applications in nanoscale optoelectronic and electronic devices.

Fabrication of Multilayer Borophene on Insulator Structure

The X-ray photoelectron spectroscopy spectra indicate the peak of BB bonds, implying that the elemental boron structure might be formed after the process. The multilayer β-borophene is directly observed by transmission electron microscopy (TEM) and the lattice parameters are valid. The middle SiNx layer also can be identified in TEM image. Furthermore, the 1.61 eV bandgap of the multilayer β-borophene is announced in this study.

Vertical Al2Se3/MoSe2 heterojunction on sapphire synthesized using ion beam

The vertical Al2Se3/MoSe2 heterojunction on sapphire was first fabricated via an ion beam-assisted process. The MoSe2 was formed via Mo selenization, while Al2Se3 was formed via Se substitution for O in sapphire. The applications of this heterojunction will be developed in the future.

Catalyst-free GaN nanorods grown by metalorganic molecular beam epitaxy

Without a catalyst or template layer, GaN nanorods were successfully grown on c-sapphire substrates by RF-radical source metalorganic molecular beam epitaxy (RF-MOMBE). XRD, SEM, TEM, EDX and micro-PL were employed to characterize the structural and optical properties of GaN nanorods. The growth of GaN nanorods was uniformly observed across the substrate surface. These nanorods have an average diameter of 50 nm. and the rod number density can reach 1/spl times/10/sup 10/ cm/sup -2/ depending on the growth parameters. The clear lattice fringes in HRTEM image revealed the growth of high quality hexagonal single-crystal GaN nanorods and no droplet was observed at the end of the nanorods. Meanwhile, EDX analysis revealed that gallium and nitrogen as the only detectable elements. Room-temperature photoluminescence of GaN nonorods showed a band-edge-emission at the energy position of /spl sim/3.4 eV. The catalyst-free growth mechanism of GaN nanorods was discussed on the basis of experimental results in this work. These high-quality and high-density GaN nanorods might be useful for practical applications in nanoscale optoelectronic and electronic devices.

Temperature-induced Morphological Evolution of Indium Nitride

1 Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan Phone: +886-3-2118800 ext :3351 E-mail: sykuo@mail.cgu.edu.tw 2 Instrument Technology Research Center, National Applied Research Laboratories, 20 R&D Road VI, Hsinchu Science Park, Hsinchu 300, Taiwan 3 Department of Electrical Engineering, Yuan-Ze University, 135, Far-East Rd., Chung-Li, Taoyuan, Taiwan, ROC, Tao-Yuan, 320, Taiwan