Yong Sun Won

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.

Homogeneous decomposition mechanisms of diethylzinc by Raman spectroscopy and quantum chemical calculations.

The gas-phase decomposition pathways of diethylzinc (DEZn), a common precursor for deposition of Zn-VI compounds, were investigated in detail. The homogeneous thermal decomposition of DEZn in N2 carrier was followed in an impinging-jet, up-flow reactor by Raman scattering. Density Functional Theory calculations were performed to describe the bond dissociation behavior using the model chemistry B3LYP/6-311G(d) to estimate optimal geometries and Raman active vibrational frequencies of DEZn, as well as anticipated intermediates and products. Comparison of the measured DEZn decomposition profile to that predicted by a 2-D hydrodynamic simulation revealed that simple bond dissociation between zinc and carbon atoms is the dominant homogeneous thermal decomposition pathway. The calculations suggest several reactions involving intermediates and Raman scattering experiments confirming the formation of the dimer (ZnC2H5)2. In a different set of experiments, photolysis of DEZn gave evidence for decomposition by beta-hydride elimination. The results suggest that beta-hydride elimination is a minor pathway for the gas-phase homogeneous pyrolysis of diethylzinc. A reasonable transition state during beta-hydride elimination was identified, and the calculated energies and thermodynamic properties support the likelihood of these reaction steps.

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).