Jooyoung Suh

Growth of ZnTe:O Thin Films by Oxygen-Plasma-Assisted Pulsed Laser Deposition

We studied oxygen incorporation into ZnTe thin films with oxygen ambient and oxygen plasma during pulsed laser deposition (PLD). The ZnTe layers deposited by oxygen-plasma-assisted PLD under oxygen partial pressures showed the enhancement of visible absorption due to TeOx formation by oxygen incorporation, which was confirmed by X-ray photoelectron spectroscopy measurement. The ZnTe:O thin films grown under oxygen ambient and plasma produced an energy band structure at about 0.5–0.8 eV below the ZnTe band edge, indicating strong radiative properties. The ZnTe:O samples showed the formation of intermediate bands and p-type semiconducting characteristics, which will be useful for intermediate/defect band solar cells.

Structural and Magnetic Properties of Fe-Diluted Si Alloy Films by Pulsed-Laser Deposition

Fe-diluted Si alloys grown on p-type Si (100) substrates by pulsed-laser deposition method were studied for tructural, electrical, and magnetic properties. The X-ray diffraction patterns for these alloy samples showed a few of peaks with cubic structures such as FeSi, Fe3Si, and Fe4Si. The Fe-composition in alloys are confirmed as Fe atomic percent about 1.25∼6.49 % from energy dispersive spectroscopy measurement. The resistivity as a function of the reciprocal temperature was indicated an exponential increase with two activation energies of 5.21 and 7.79 meV. The maximum value of the magnetization at 10 K was about 100 emu/cc, and the ferromagnetism was also observed until 350 K from total magnetization as a function of temperature with applied magnetic field of 3,000 Oe.

Influence of Growth Parameters on Structural Anisotropy of Epitaxial a‐plane GaN Films

We investigated the structural anisotropy of a‐plane GaN films grown by using multi‐buffer layer technique on (1‐102) r‐plane sapphire substrates. For high quality a‐plane GaN films, multi‐buffer layers with various growth conditions were grown by metal‐organic chemical vapor deposition, and analyzed by using several measurement systems such as optical microscopy, scanning electron microscopy, high resolution x‐ray diffraction. The experimental results showed that the nucleation‐layer thickness and the growth temperature of three‐dimensional (3D) growth layer affect significantly the crystal quality of subsequently grown a‐plane GaN films. When the nucleation‐layer thickness was 150 nm, nuclei were fully coalesced. From the x‐ray diffraction results, it appeared that the growth temperature during 3D islands growth affects the full‐width at half maximum (FWHM) values of x‐ray rocking curves along c‐ or m‐directions. At optimized growth conditions, the omega FWHM values of (11–20) x‐ray rocking curve along ...

Ohmic Contact of Ti/Au Metals on n-type ZnO Thin Film

The Ohmic contact of Ti/Au metals on n-type ZnO thin film deposited on c-plane sapphire substrates by pulsed laser deposition was investigated by TLM (transfer length method) patterns. The Ti/Au metal films with thickness of 35 nm and 90 nm were deposited by electron-beam evaporator and thermal evaporator, respectively. By using the photo-lithography method, the TLM patterns with gaps were formed. To improve the electrical properties as well as to decrease an interface states and stress between metal and semiconductor, the post-annelaing process was done in oxygen ambient by rapid thermal annealing system at temperature of for 1 min. In this study, it appeared that the minimum specific contact resistivity shows about in annealed sample, which may be originated from formation of oxygen vacancies of ZnO during an oxidation of Ti metal at the interface of Ohmic contacts.

High magnetoresistance of InSb with an embedded Au core

This study explores the possible scalability of the device by investigating the magnetoresistance (MR) of small sized devices around 100 mum in diameter. Polycrystalline InSb film (1 mum thick) is thermally evaporated onto the insulating Si substrate. InSb van der Pauw disk (100 mum size) was fabricated by standard microfabrication techniques. Subsequently, the core and contact pads are covered by a Ti/Au, with Au being the dominant component. The MR of prepared devices with different embedded Au size is systematically investigated to find out the optimum embedded Au size and the origin of geometrical MR.