Junggeun Jhin

Copper thin films on PET prepared at ambient temperature by ECR-CVD

Metallized polymers were prepared at ambient temperature by an electron-cyclotron-resonance (ECR) chemical vapor deposition system equipped with (-) DC bias from the Cu (hfac)/sub 2/-Ar-H/sub 2/ system. X-ray difraction (XRD) results showed that the Cu (111) peaks were clearly observed when H/sub 2/ was introduced to the plasma. The surface morphology showed that larger Cu grains were formed in the metal-organic composite films with the introduction of H/sub 2/ to the plasma. AES depth profiles showed that H/sub 2/ gas introduction to the plasma led to the formation of copper-rich films with a homogeneous composition. Also, the sheet resistance was strongly dependent on the H/sub 2/ content of the plasma. This means that hydrogen may lead to both the formation of stable volatile organic compounds and the reduction of copper, which influences both the crystallographic structure and the composition of films. As a result, crystalline copper films with a sheet resistance of 2-3/spl Omega//sup 2/ can be prepared on poly ethylene terephthalate with the addition of H/sub 2/ to the plasma.

Implantation of N ions on sapphire substrate for improvement of GaN epilayer

In an effort to improve the initial nucleation and crystal quality of the GaN epilayer, N-ion implantation on the sapphire (0001) substrate has been attempted. As a result of implantation with 55 keV nitrogen ions (N+), to a dose ranging from 1×1015 to 1×1017 cm-2, prior to GaN epilayer growth, the formation of a thin and disordered AlN phase was observed. The presence of the N-ion-implanted surface decreased internal free energies in the growth of the GaN epilayer, and the misfit strain was relieved to allow the formation of the AlN phase on the N-ion-implanted sapphire substrate. Through the estimation of the lattice strain value for GaN epilayers, it was confirmed that the reduction of strain was achieved with the N-ion-implanted surface with the ion dose of 1×1016 cm-2. The present results show that N-ion implantation of the sapphire (0001) surface can improve the properties of GaN epilayers grown by metalorganic chemical vapor deposition (MOCVD).

Influence of the Density of Crack-Initiating Defects on Crack Spacing for GaN Films on Si(111) Substrate

This study examines the cracking of GaN films grown on Si(111) substrates, with particular focus on the effect of the density of crack-initiating defects (CIDs) on the crack spacing. The relationship between the CID density and crack spacing was examined by comparing specimens of the same thickness and under the same stress but with different CID density. The CID density in the GaN layer was changed by varying the ion-implanted area using patterning prior to metal–organic chemical vapor deposition (MOCVD) growth. The crack spacing decreased with increasing CID density, but this effect could not be explained by the previous model. Therefore, a CID-density related factor, nd, was newly introduced to explain the crack spacing and film stress relationship.

Effect of Patterned Ion-Implanted Sapphire on Ultraviolet Light-Emitting Diodes

Ultraviolet (UV) light-emitting diodes (LEDs) were fabricated on patterned-ion-implanted sapphire (PIIS) substrates using metalorganic chemical vapor deposition. The crystal qualities of the n-GaN epilayer grown on the patterned-N+-ion-implanted sapphire substrate were improved compared with that of the n-GaN epilayer grown on a conventional sapphire substrate. The optical properties of the undoped GaN and n-GaN epilayers grown on the PIIS substrate were improved. The light intensity of the UV LED at 100 mA on the PIIS chip was 78% higher than that of the conventional LED. This increase in light intensity is due to the relaxation of the misfit strain at high temperature and the contribution of the internal free energies to the enhancement in structural and optical properties.

Reduction of Defects in GaN on Reactive Ion Beam Treated Sapphire by Annealing

Previous studies showed that reactive ion beam (RIB) pretreatment of sapphire prior to GaN deposition results in the reduction of dislocation density in the GaN film. It was also found that an amorphous phase remained at the interface region after the GaN deposition at high temperature. Annealing was performed to obtain the structural change due to the recrystallization of the remaining amorphous phase, and the effect on the electrical properties of the GaN thin film on RIB treated sapphire (0001) substrate. DCXRD spectra and Hall mobility of the specimen were studied as a function of the annealing time at 1000°C in N 2 atmosphere. For the annealed specimen, FWHM of DCXRD decreased and the mobility increased. The annealed specimen was compared with a not annealed sample by TEM. A decrease of lattice strain and a reduction of the dislocation density about 56-59% was observed. The present results clearly show that the combination of RIB pretreatment and proper post annealing conditions improve the properties of GaN films grown by MOCVD.

Surface‐treatment effects of a sapphire substrate by He+‐, Ar+‐, and Xe+‐ion implantations for GaN epitaxial layers

— The structural, electrical, and optical properties of GaN epilayers grown on various ion-implanted sapphire(0001) substrates by MOCVD were investigated. GaN or AlN buffer layers and pre-treatment were indispensably introduced before GaN-epilayer growth. The ion-implanted substrates surface had decreased internal free energies during the growth of the ion-implanted sapphire(0001) substrates. The crystal and optical properties of the GaN epilayers grown in ion-implanted sapphire(0001) substrates were improved. Also, an excessively roughened and modified surface caused by ions degraded the GaN epilayers. Not only the ionic radius but also the chemical species of implanted sapphire(0001) substrates improved the properties of the GaN epilayers grown by MOCVD. It is obvious that the ion-implanted pre-treatment of sapphire(0001) substrates can be an alternative pre-treatment procedure for GaN deposition and has the potential to improve the properties of the GaN epilayers on sapphire(0001) substrates.

Effect of plasma pretreatment of soda-lime glass on the preferred orientation of TiO/sub 2/ prepared by PECVD

Summary form only given, as follows. TiO/sub 2/ has environmental application due to its unique photoinduced properties such as antibacterial and superhydrophilic functions. It is reported that crystalline structure and orientation of TiO/sub 2/ thin film affect photocatalytic efficiency. And our previous study showed that -preferred orientation TiO/sub 2/ film resulted in the better photocatalytic efficiency. -oriented TiO/sub 2/ thin films were fabricated on soda-lime glass substrate using PECVD methods. This study was the effort to find the correlation between pretreatment with plasma and -preferred orientation of TiO/sub 2/ thin films. The PECVD methods were used at the relatively low substrate temperature of the range from 250/spl deg/ to 412/spl deg/ in order to avoid Na/sup +/ diffusion from the soda-lime glass substrate into TiO/sub 2/ layer during deposition.

Characteristics of Cu thin film on PET by ECR-PECVD

Summary form only given, as follows. Metallized polymers were prepared at an ambient temperature by an electron-cyclotron-resonance (ECR) plasma enhanced chemical vapor deposition (PECVD) system equipped with (-)DC bias from the Cu(hfac)/sub 2/-Ar-H/sub 2/ system. Metallized polymers, and especially poly ethylene terephthalate (PET), are currently being studied and employed for microelectronic packaging, magnetic tapes, EMI shielding, etc. Copper is an attractive material for metallization thanks to its intrinsic electromigration resistance and low resistivity.

Dielectric Properties of Ta 2 O 5 Films Annealed at Various Temperature by MOCVD and MOD

To explore the annealing temperature dependence of dielectric properties thin films were prepared by MOCVD(metal-organic chemical vapor deposition) and MOD(metal-organic decomposition). The thin films fabricated MOCVD and MOD were annealed in at temperature between 600 and 90. The measured dielectric constant of both films at 100 KHz was the highest value at and decreased with increasing annealing temperature above . Plane-view SEM image showed that the boundary seems to be crack broke out with increasing annealing temperature. It was confirmed that outbreak of boundary influenced a decrease of dielectric constant with increasing annealing temperature. The leakage current density increased with increasing annealing temperature.

The Characteristics of 〈112〉-preferred Orientation for Photocatalytic TiO 2 Fabricated by CVD

The characteristics of orientation were studied for the thin films, which were prepared on the glass by CVD (chemical vapor deposition) at various substrate temperatures. It was confirmed that films exhibited -preferred orientation in a specific temperature range. Although polycrystalline film grown deposited at relatively low temperature showed the growth of random directions, the -preferred orientation was gradually developed with increasing deposition temperature. According to exhibit higher degree of -preferred orientation, thin film showed porous surface morphology, well-developed columnar structure, and deeper voids resulted from non-aggregation of columns were observed. In addition, transmittance was enhanced. Therefore, the growth of with -preferred orientation is suitable for glass coating because of predominance of photocatalytic efficiency and transmittance.