Hyun Jong Park

Pt-coated InN nanorods for selective detection of hydrogen at room temperature

Single crystal InN nanorods were successfully grown on c‐Al2O3 by hydride-metalorganic vapor phase epitaxy. The measured resistance of bare InN nanorods does not change upon exposure to hydrogen ambient. The addition of sputter-deposited clusters of Pt onto the surface of the InN nanorods, however, produced a significant change in the measured room temperature resistance. The measured resistance changed systematically by 0.5%–12% as the ambient hydrogen concentration in N2 was varied between 10 and 250 ppm after 15 min exposure time. Importantly, a relatively low power consumption of ∼0.3mW was measured under these conditions. There was no response at room temperature to O2, N2O, or NH3 exposures.

Controlled synthesis of single-crystalline InN nanorods

Single-crystalline InN nanorods were successfully grown on c-Al2O3 ,G aN, Si(111), and Si(100) substrates by non-catalytic, template-free hydride metal‐organic vapour phase epitaxy (H-MOVPE). It was evaluated thermodynamically and confirmed experimentally that the domain of nanorod growth lies in the vicinity of the growth‐etch transition. Stable gas phase oligomer formation is suggested as the nucleation mechanism for InN nanoparticle generation. Dislocation-free, high-quality InN nanorods with [00.1] growth axis were formed via an apparent solid‐vapour growth mechanism. The nanorod diameter, density, and orientation were controlled by growth temperature, substrate selection, and HCl/TMIn and N/In inlet molar ratios.

Prevention of In droplets formation by HCl addition during metal organic vapor phase epitaxy of InN

The low decomposition temperature of InN and relatively high thermal stability of NH3 necessitate the use of a high NH3∕TMIn ratio to prevent In droplet formation on the surface. This work shows that the addition of Cl in the form of HCl (Cl∕In molar ratio range of 0.3–1.4) to the growth chamber allows the growth of high quality InN films without the formation of a second In phase at a very low value of the N∕In molar inlet ratio (2500). Photoluminescence spectra in the temperature range of 144to4.5K showed a broad spectral band with a cutoff energy close to the reported minimum of the InN band gap energy (0.65eV).

Internetwork access control using public key certificates

Packet-level Access control Security Scheme* (PASS) is a policy enforcement scheme for controlling inter-domain packet traffic between interconnected administrative domains (ADs). As an indispensable part of the scheme, PASS includes an inter-domain authentication protocol which is based on ITU-T X.509 public key certificate directory service. This eliminates the need of a dedicated access control server in each AD and of sharing private keys between neighboring network entities. This paper addresses the design of PASS scheme and the inter-domain authentication protocol. An overhead analysis and comparison with other schemes are also provided.

Morphological study of InN films and nanorods grown by H-MOVPE

Hydride-Metalorganic Vapor Phase Epitaxy (H-MOVPE) was used to grow a series of films on c-Al 2 O 3 substrates. Depending on the growth temperature and HCl/TMIn molar ratio, InN deposited as a continuous film or a collection of micro or nanorods, or no InN growth was observed. A chemical equilibrium analysis of the In-N-H-Cl system predicts both InN growth and etching regimes with the nanorod growth observed near the growth-etching transition. All InN rod structures demonstrated well faceted hexagonal structure with a near random orientation of the rods, while the films were polycrystalline.

InN Nanorods and Epilayers: Similarities and Differences

Transmission electron microscopy was applied to study InN nanorods grown on the a-, c-and r-plane of Al{sub 2}O{sub 3}, and (111) Si substrates by non-catalytic, template-free hydride metal-organic vapor phase epitaxy (H-MOVPE). Single crystal nanorod growth was obtained on all substrates. However, the shape of the nanorods varied depending on the substrate used. For example, nanorods grown on r-plane sapphire and (111) Si have sharp tips. In contrast, growth on a- and c- planes of Al{sub 2}O{sub 3} results in flat tips with clear facets on their sides. The structural quality of these nanorods and their growth polarity are compared to crystalline quality, surface roughness, defects and growth polarity of InN layers grown by MBE on the same planes of Al{sub 2}O{sub 3}.