The development of embryonic stem cells (ESCs) from large animal species has become an important model for therapeutic cloning using ESCs derived by somatic cell nuclear transfer (SCNT). However, poor embryo quality and blastocyst formation have been major limitations for derivation of cloned ESCs (ntESCs). In this study, we have tried to overcome these problems by treating these cells with histone deacetylase inhibitors (HDACi) and aggregating porcine embryos. First, cloned embryos were treated with Scriptaid to confirm the effect of HDACi on cloned embryo quality. The Scriptaid-treated blastocysts showed significantly higher total cell numbers (29.50 ± 2.10) than non-treated blastocysts (22.29 ± 1.50, P < 0.05). Next, cloned embryo quality and blastocyst formation were analyzed in aggregates. Three zona-free, reconstructed, four-cell-stage SCNT embryos were injected into the empty zona of hatched parthenogenetic (PA) blastocysts. Blastocyst formation and total cell number of cloned blastocysts increased significantly for all aggregates (76.4% and 83.18 ± 8.33) compared with non-aggregates (25.5% and 27.11 ± 1.67, P < 0.05). Finally, aggregated blastocysts were cultured on a feeder layer to examine the efficiency of porcine ES-like cell derivation. Aggregated blastocysts showed a higher primary colony formation rate than non-aggregated cloned blastocysts (17.6 ± 12.3% vs. 2.2 ± 1.35%, respectively, P < 0.05). In addition, derived ES-like cells showed typical characters of ESCs. In conclusion, the aggregation of porcine SCNT embryos at the four-cell stage could be a useful technique for improving the development rate and quality of porcine-cloned blastocysts and the derivation efficiency of porcine ntESCs.

The growth of high-quality indium (In)-rich InXGa1−XN alloys is technologically important for applications to attain highly efficient green light-emitting diodes and solar cells. However, phase separation and composition modulation in In-rich InXGa1−XN alloys are inevitable phenomena that degrade the crystal quality of In-rich InXGa1−XN layers. Composition modulations were observed in the In-rich InXGa1−XN layers with various In compositions. The In composition modulation in the InXGa1−XN alloys formed in samples with In compositions exceeding 47%. The misfit strain between the InGaN layer and the GaN buffer retarded the composition modulation, which resulted in the formation of modulated regions 100 nm above the In0.67Ga0.33N/GaN interface. The composition modulations were formed on the specific crystallographic planes of both the {0001} and {0114} planes of InGaN.

The crystallization of amorphous silicon thin films by electron beam exposure was studied. Amorphous silicon and silicon dioxide layers were deposited on glass substrate by PECVD at 360 °C. The optimization to crystallize 300 nm thick amorphous silicon film was carried out at a RF power of 300 W, DC voltage of 1500 V, Argon gas flow rate of 3 sccm and a distance between electron beam mesh and sample of 40 mm. High quality nano-crystalline silicon films with an activation energy of 0.47 eV from conductivity, a grain size of 15–45 nm from SEM and Raman crystalline volume fraction of 93.1% were fabricated. We expect that e-beam exposure will be applied to crystallization of amorphous silicon films.

We have fabricated a new magnetic field enhanced solid phase crystallization (FESPC) polycrystalline silicon (poly-Si) thin film transistors (TFTs), which shows the excellent electrical characteristics and superior stability compared with hydrogenated amorphous silicon (a-Si:H) TFTs. The mobility (μ) and threshold voltage (VTH) of p-type TFTs of which the channel width and length are 5 μm and 7 μm, respectively are 31.98 cm2/Vs and -6.14 V, at VDS=-0.1 V. In the FESPC TFTs, the characteristics caused by grain boundary are remarkable due to large number of grain boundaries in the channel compared with poly-Si TFTs. The VTH of the TFT which have 5 μm channel length is smaller than that of 18 μm channel length by 1.36 V, which is considerably large value. It is due to the large number of grain boundaries in the channel and the high lateral electric field. The grain boundary potential barrier height is decreased, when the large lateral electric field is applied (which is called DIGBL effect). As a result of increased mobility, the drain current is increased, and VTH can be decreased. The activation energy (Ea) is strongly depended on the drain bias and the number of grain boundaries. is decreased, caused by the large drain bias and/or smaller number of grain boundaries. This decreased Ea can be reduced VTH due to increased the drain current. VTH of p-type poly-Si TFT employing FESPC on the glass substrate is affected by channel length and VDS due to energy barrier lowering effect at the grain boundary by increased lateral electrical field.

The hydrophobicity of poly Si is reported to introduce different polishing behavior with careful control of post CMP cleaning process. The purpose of this study was to investigate the effect of poly Si wettability on its CMP behavior. The adhesion force of polymeric particle on the poly Si wafer surfaces was measured in the KOH solution (pH 11) as a function of solution A concentration. Adhesion force decreased and saturated as a function of concentration of solution A. The change of surface wettability affects not only the polishing rates but also the level of contamination on wafer because the interactions between particles and substrates are dependent on the wettability of the surface. Also, hydrophobic poly Si surfaces attracted much more pad particles with water marks than hydrophilic

A bistable effects of Au nano-crystals embedded in poly(N-vinylcarbazole) (PVK) were observed. Subsequently we investigated dependency of the nonvolatile memory behavior on curing temperature for the Au nano-crystals embedded in the PVK. For the study, in the devices of different curing temperatures we measured current-voltage characteristics for the devices and investigated the formation of the Au nano-crystals using cross sectional transmission electron microscopy (TEM). The nonvolatile memory behavior depends on the curing temperature, which is attributed to the suitable formation of the Au nano-crystal.

Various Cu films were fabricated using sputtering and electroplating with and without additive, and their surface damages after annealing were investigated. After annealing at 435°C, the difference between damage morphologies of the films was observed. In some films stressinduced grooves along the grain boundaries were observed, while in the others voids at the grain boundary triple junctions were observed. It was also observed that the stress-induced groove was formed along the high energy grain boundaries. To explain the morphological difference of surface damages, a simple parameter considering the contributions of grain structures and grain boundary characteristics to surface and grain boundary diffusions is suggested. The effective grain boundary area, which is a function of grain size, film thickness and the fraction of high energy grain boundaries, played a key role in the morphological difference.

We report a new Ni/Pt/Au (20/30/80 nm) metallization scheme to achieve a low ohmic contacts to p-type GaN with a carrier concentration of 9.4 × 1016 cm-3. A Mg-doped GaN layer (0.5 μm) was grown on (0001) sapphire substrate by metalorganic chemical vapor deposition (MOCVD). All metal thin films were deposited on the p-GaN layer in an electron-beam evaporation system. Samples were annealed by a rapid thermal annealing (RTA) process at a range of temperatures from 300 °C to 850 °C under a flowing Ar atmosphere. A circulartransmission line model (c-TLM) was employed to calculate the specific contact resistance, and current-voltage (I-V) data were measured with HP4155A. The Ni/Pt/Au contacts without the annealing process showed nearly rectifying characteristics. The ohmic contacts were formed on the samples annealed at 500 °C for 30 sec and the I-V data showed a linear behavior. The specific contact resistance was 2.1 × 10-2 Ωcm2. However with increasing the annealing temperature above 600 °C, ohmic contacts were again degraded. Auger electron spectroscopy (AES) depth profiles were used to investigate the interfacial reactions between the trilayer and GaN. AES results suggested that Pt plays a significant role in forming ohmic contact as an acceptor at the interface. Atomic force microscope (AFM) also showed that the samples with good ohmic contact have very smooth surface.

A surface of thin square PTFE samples (1×1×0.2 cm3) was irradiated with Ar+ ion at 1 keV with varying ion dose from 5 x 1014 to 1 x 1017 ions/cm2 with and without oxygen environment. The chemical structure of the surface was examined by XPS. The high resolution XPS spectra showed decreased intensity of the Fls peak and formation of the Ol s peak when irradiated with O2 environment. The Ols peak reached the maximum height at the ion dose of 1 x l015 ions/cm2. The increase of the Ols peak may be attributed to the reaction of oxygen atoms and the free radicals created by Ar+ bombardment. Adhesion tests were conducted on 2000 Å thick Al or Cu film which was evaporated on the irradiated and unirradiated PTFE samples with and without O2 environment. Full detachment of the metal films was observed when PTFE samples were not modified. With regard to the Al film, partial detachment of the film occurred when PTFE was irradiated without O2 environment, regardless of ion dose. No detachment of the film occurred when PTFE was irradiated with O2 environment with the ion dose exceeding 1 x 1016 ions/cm2. As to the Cu film, partial detachment was observed with or without O2 environment when the ion dose was 5 x 1014 ions/cm2. No detachment occurred with or without O2 environment when the ion dose was 1 x 1015 ions/cm2 or greater. The adhesion of an adhesive (Crystal Bond) to the irradiated PTFE samples was found to increase significantly with increasing ion dose up to 1 x 1016 ions/cm2 in tensile tests. It appears that three separate mechanisms are at work in improving adhesion of Cu/PTFE and Al/PTFE system. The first is the surface roughness of PTFE caused by Ar+ bombardment, the second is the chemical changes on the PTFE surface, and the third is a change of the interface between the metal and PTFE. The wettability of the PTFE surface was also determined by dropping water droplets on the modified surfaces. The contact angle between water droplets and the irradiated surface of PTFE samples decreased with ion dose up to 1 x 1015ions/cm2, increased at higher dose, and finally increased to the extent that no wetting was possible at 1 x 1017 ions/cm2. The PTFE samples irradiated with Ar+ without O2 gas environment had lower contact angle than those with O2, even though the samples with O2 developed hydrophilic groups on the irradiated surface. This result on wettability is not consistent with our earlier results on PMMA and PC and is due to the unusually high level of surface roughness of PTFE caused by Ar+ bombardment.

We have studied the structural properties of hydrogenated carbon films deposited by plasma enhanced chemical vapor deposition (PECVD). The substrate holder in reaction chamber could be biased and be heated. The Raman peak intensity at 1350 cm−1 was increased by reducing CH4 flow rate. The film structure changed from soft a-C:H to hard carbon with decreasing CH4 flow rate, resulted from increased self-bias. The 1520 cm−1 peak shifts to higher frequency by reducing the CH4flow rate, probably resulted from the increased internal stress.

We have studied the growth of microcrystalline silicon (μc-Si) and amorphous silicon (a-Si:H) by layer by layer deposition technique, where the deposition and the radical exposure are done alternatively. He or hydrogen plasma exposure gives rise to the etching effect of both μc-Si and a-Si:H even though the etch rate by He plasma is much smaller. The long exposure of hydrogen radical on a-Si:H gives rise to the formation of μc-Si at low substrate temperature (Ts), whereas the hydrogen content decreases at high Ts. The growth mechanism of the crystallite is proposed on the basis of experimental results.

We have studied the depositions of amorphous silicon, silicon carbon alloy, doped microcrystalline silicon in order to apply these films as the component materials for the p-i-n and double stacked solar cells. We have obtained low band gap a-Si:H by decreasing the deposition rate under the proper preparation conditions and highly conductive, thin microcrystalline Si and SiC layers. We have developed a stable a-Si/a-Si double stacked solar cell with a conversion efficiency of ∼ % using narrow band gap a-Si:H as a i-layer of bottom cell.The performance of this cell does not degrade until 100 hrs illumination under 350 mW/cm2.

We have studied the effect of RF power on the properties of Si thin films prepared by a conventional plasma and remote plasma(RP)- CVD. The structure of the Si film changes from amorphous to crystalline with increasing RF power in RP-CVD. However, the structure of Si film deposited by P-CVD remains amorphous with increasing RF power. The relaxation of Si atoms by means of chemical annealing of He metastable atoms gives rise to the formation of macrocrystalline structure at the high RF powers.

We studied the growth of polycrystalline silicon by using remote plasma chemical vapour deposition technique. The effects of RF power and the substrate temperature on the structural properties have been investigated. With increasing the RF power, the crystalline volume fraction and the grain size increase up to 100W, but decrease for the further increase in power level. We obtained the poly-Si with the crystalline volume fraction of about 74 at.% at the substrate temperature of 330°C.

We studied the layer by layer deposition technique of a-Si:H film, where the hydrogen radicals are exposed between the deposition of each layer. The effects of each layer thickness and hydrogen radical exposure time on the electrical and optical properties were studied. With the decrease of the each layer thickness, more hydrogen is involved in the network if the structure is still amorphous, but the hydrogen content is very small for microcrystal Si formed by long exposure to hydrogen radicals in between the depositions of thin layers.