The offset of the underlying TiW is introduced in the island of Si, SiO2 and TiW on glass. During the dual-beam excimer-irradiation to the Si and the TiW, the offset in TiW acts as an extra heat source, which melts completely the Si film near the edge, whereas the Si inside is partially melted. The laterally columnar Si grains with a length of 3.2 μm were grown from the inside of the island towards the edge. By changing the shape of the edge, the direction of the solidification of the grain was successfully controlled in such a way that the all grain-boundaries are directed towards the edge and a single grain expands. The grain-boundary-free area as large as 4 μm × 3 μm was obtained at a predetermined position of glass.

We have investigated sequential lateral solidification (SLS) of amorphous Si films that have been prepared via PECVD and sputter deposition methods. The focus of the work was on identifying and analyzing the energy density and per-pulse translation distance parameter space that permits SLS of these films. Experimental details include the use of a two-axisprojection irradiation system to image a straight-slit beamlet pattern onto the sample, and analyzing the resulting microstructures by SEM and optical microscopy of Secco-etched samples. High-temperature-deposited LPCVD films were also examined to enable further comparative analysis. We conclude from these results that there are no major differences in both the SLS process characteristics and the resulting microstructure among the investigated films (provided that the films are dehydrogenated in the case of PECVD a-Si). Based on the controlled super-lateral growth (C-SLG) model of the SLS process, we attribute these findings to the fact that the SLS method involves—as one of its essential features—complete melting of the Si film at fluences that are sufficient to thoroughly melt crystalline Si films, during which all pre-irradiation phase and microstructural details are erased.

Very low threshold field emission from undoped microcrystalline diamond films grown by the hot filament chemical vapour deposition process (HFCVD) is reported. The effect of crystal size, methane concentration and the temperature has been studied. The microcrystalline diamond films grown using 3% methane (CH4) / hydrogen (H2) gas mixture ratio under varying deposition temperatures exhibit very low emission threshold fields. The threshold fields varied from 0.4 V/ [.proportional]m to 1 V/[.proportional]m for an emission current density of 1 [.proportional]A/cm2. A correlation between the emission characteristics and the material properties is presented. These films exhibit an emission site density of ∼ 104−105/cm2 at an applied field of 3 V/[.proportional]m.

Undoped and Zn doped InGaN microcrystals were synthesized by a two-step method. The InGaN microcrystals have a wurtzite structure and brownish body color. The InGaN samples prepared at 900°C did not contain a metal In phase. The InGaN:Zn microcrystals showed blue photoluminescence (PL) at 77K different from that of GaN:Zn. Reflectivity and photoluminescence excitation (PLE) measurement showed that the fundamental absorption edge of the InGaN:Zn phosphors is 3.47 eV, which implies that the In content in the InGaN:Zn phosphors is less than 0.2%. GaN:Zn and InGaN:Zn showed a Zn related PLE peak at 3.34 eV. InGaN and InGaN:Zn showed an In related PLE peak at 3.14 eV. When the InGaN:Zn samples were selectively excited at 3.15 eV, an In-related emission band centered at 2.2 eV emerged. The InGaN:Zn phosphors mounted on vacuum fluorescent displays (VFDs) showed room-temperature blue cathodoluminescence (CL) and the CL peak shifted slightly toward the low energy compared to that of the GaN:Zn phosphors because of the superimposed In related band. The InGaN:Zn phosphors had a luminance of 50 cd/m2 and a luminance efficiency of 0.03 lm/W at an anode voltage of 50 V.

Fabrication and characterization of carbon nanotubes deposited on microstructured Ni substrate are presented. The highly active surface-area of the microstructured Ni substrate provides highdensity nucleation sites for carbon nanotubes. Coated fine Ni powder also serves as a catalyst for the nanotube growth. Hydrocarbon mixtures were used as the carbon source for the chemical vapor deposition process. Carbon nanotubes deposited on the microstructured Ni substrate were examined by SEM. An ultra high vacuum chamber was used to characterize the field emission properties of carbon nanotube coatings.

We crystallize amorphous silicon films with a frequency doubled Nd:YVO4 laser operating at a repetition frequency of up to 50 kHz. A sequential lateral solidification process yields polycrystalline silicon with grains longer than 100 μm and a width between 0.27 and 1.7 μm depending on film thickness and laser repetition frequency. The average grain size is constant over the whole crystallized area of 25 cm2. Thin film transistors with n- type and p-type channels fabricated from the polycrystalline films have average field effect mobilities of μn = 467 cm2/Vs and μp = 217 cm2/Vs respectively. As a result of the homogeneous grain size distribution, the standard deviation of the mobility is only 5%.

Several materials are promising candidates for electron sources. For diamond, a tunneling interface at the back contact limits injecting charge into the conduction band, but a purely geometric model of internal field emission is inadequate to explain experimental data. The presence of a defect, modeled by a coulomb charge, within the tunneling barrier region significantly enhances transmission and, in concert with a geometrical model, may better account for observed current levels. Charge has been suggested to play a similar role in the SiO2 covering on a single tip silicon field emitter to explain experimental data. The tunneling theory in both cases is similar. In the present work, a general method for estimating electron transport and energy distributions through potential profiles, which describe both semiconductor interfaces and field emission potential barriers when a charged particle modifies the tunneling barrier, is developed. While the model is intended for treating a metal-semiconductor interface, it is cast here in terms of in a thin SiO2 coating over a silicon field emitter tip to enable qualitative comparisons with experimental data. Tunneling probabilities are found by numerically solving Schrödinger's Equation for a piece-wise linear potential using an Airy Function approach. A qualitative comparison to experimental energy distribution findings is possible by utilizing an analytical model of the field emitter tip from which current-voltage relations may be found.

We investigated the optical properties of Fabry-Perot microcavity with a tris(8- hydroxyquinoline)aluminum (Alq3) organic film by measuring the photoluminescence (PL) and transmittance. An Alq3 layer as an active layer was sandwiched between two mirrors, which were metal or (TiO2|SiO2) dielectric multilayer reflectors. An Alq3 layer on glass, [air|Alq3|glass], showed a PL peak around 513 nm and its full width half maximum (FWHM) was about 80 nm. Three types of microcavity, such as Type A [air|metal|Alq3|metal|glass], Type B [air|dielectric|Alq3|dielectric|glass], and Type C [air|metal|Alq3|dielectric|glass], were fabricated. The result shows that the FWHMs of three Fabry-Perot microcavities were reduced to 15∼27.5, 7∼10.5 and 16∼16.6 nm, respectively, and the microcavity structure is expected to improve the efficiency and tunability of emission spectrum in display.

Spectroscopic ellipsometry was used to evaluate the density and surface roughness of MgO films. The density of a film affects the dispersion of the film's refractive index, and the refractive index can be evaluated by spectroscopic ellipsometry. Among the various fitting models applied to all of the deposited films, the two-layered model gave the best results. For the two-layered model, we found that the thickness of the upper layer was strongly correlated with surface roughness. Thus, spectroscopic ellipsometry can be used to evaluate density and roughness.

Hydrogenated nanocrystalline silicon carbide (nc-SiC:H) films were deposited in an electron cyclotron resonance chemical vapor deposition (ECR-CVD) system using silane (SiH4) and methane (CH4) as source gases. It was discovered that under the deposition conditions of strong hydrogen dilution and high microwave power, nanocrystalline grains embedded in an amorphous matrix can be obtained, as confirmed by TEM study. Steady state and time-resolved photoluminescence (PL) from these films were investigated. The films exhibit intense visible PL at room temperature under laser excitation. The PL emission peaks at 2.64 eV, which is higher in energy compared to the bandgap of cubic SiC. Temporal evolution of the emission peak exhibits a double-exponential decay. Two distinct decay times of 179 ps and 2.88 ns were identified, which are at least 2 orders of magnitude faster than that of bound excition transitions in bulk 3C- SiC at low temperature. It was found that upon ultraviolet irradiation using an Ar+ laser (351nm) the PL intensity of the films was enhanced. After 20 minutes irradiation, the PL intensity increased by about three times. This result suggests that the UV light may lead to modification of nonradiative recombination centers in the films. These nc-SiC:H films are promising for application in large area flat panel displays and in optoelectronic storage technology.

We investigated the Layer-by-Layer method to obtain thin μc-Si films. Good quality μc-Si films can be obtained at a thickness of 600 Å Ion-doping of phosphor to i-type μc-Si was investigated to realize the top-gate, self-aligned μc-Si TFT. High conductivity, more than 1 ohm-cm, can be obtained. Using the combination of Layer-by-Layer deposition method and ion-doping method, we fabricated top gate self-aligned μc-Si TFTs. The mobility of TFTs with 600Å-thick μc-Si channel layer is 1.5 cm2/Vs, which is about three times that of a-Si TFT's mobility. The top gate self-aligned μc-Si TFT is very promising technology for large LCD with high mobility.

An excimer-laser-induced large-grain growth method has been proposed which utilizes non-uniform heat diffusion along the Si thin-film and also along the underlayer. A single-shot of KrF excimer-laser light pulse with uniform intensity could crystallize a circularly pre-patterned Si thin-film of 20νm in diameter, much larger than TFT feature size in present AM-LCD panels.

In order to clarify the relationship between excimer laser fluence gradient and the length of lateral grain growth, the laser fluence is modulated by a beam mask. The fluence distribution is measured by using a negative UV photoresist. The lateral growth length and the grain directionality are improved with increasing fluence gradient. Lateral growth length of about 1.5 [.proportional]m is achieved by using a single laser pulse without substrate heating on a 50 nm-thick a-Si film by enforcing high fluence gradient. Electrical conductance measurement is used to probe the solidification dynamics. The lateral solidification velocity is found to be about 7 m/s.

We report energy distributions of silicon Field Emitter Arrays coated with 50A of ZnO. The distributions reflect changes in the ZnO conductivity induced by annealing in vacuum, temperature, and annealing in hydrogen. An additional coating of titanium performed in-situ produced large additional changes. Emission from the ZnO at energies near the Fermi level increased with gate voltage only after hydrogen annealing, when hot, and after Ti coating. In those same cases the emission distribution contained a tail at energies above EF. The highenergy emission tail is due to a many-body or Auger process whereby holes injected below EF create hot electrons. Although emission from ZnO occurred at energies up to 8eV below EF, no high-energy tail was observed in the normal case. Thus emission appears to occur from isolated electrons in ZnO gap states in cases where the distribution lacks a high-energy tail. Conversely, emission above EF suggests that emission occurred from a metallic state such as an accumulated conduction band.

The durability of the tris(8-quinolinolato) aluminum based light-emitting diode (LED) is related to the thermal stability of the hole transport layer. Several linear linkage triphenylamine oligomers were used for the hole transport layer. The thermal stability was clearly seen to depend on a glass transition temperature (Tg) of the hole transporting material, and a linear relationship between the Tg and the thermal stability was found. A lowering of “turn-on voltage” for light emission and an increase of luminous efficiency with increasing temperature was also observed. Excellent durability of the organic LED with a tetramer of triphenylamine was achieved at a high temperature of 120°C. Our results indicate that the linear linkage of triphenylamine leads to a high Tg and high device performance at high temperatures.