The effective nonlinear susceptibility X( 3 ) for a composite that consists of a dilute suspension of structured nanoparticles that utilizes the surface mediated plasmon resonance can be enhanced by orders of magnitude compared to the intrinsic X(3) for a film of the same neat material. Here we report calculations for various multilayer spherical nanoparticle models in a host dielectric: i) polymeric core and metallic shell, ii) semiconductor core and metallic shell, iii) metallic core, polymeric shell and metallic second shell, and iv) metallic core, semiconductor shell and metallic second shell. The polymer is polydiacetylene, FDA, the semiconductor is Si, the metal is Ag, and the host is water, a GaAs2 glass or Si. Enhancements as great as 104 can be obtained in both x(3) and the figure of merit with no degradation in the intrinsic speed of the nonlinearity. The choice of geometrical parameters and of component materials permit tailoring of the wavelength dependence and bandwidth characteristics of the nonlinear response. However, fabrication of these structured nanoparticle suspensions remians the key challenge.

We study coated, nanometer-size, ellipsoidal particles that have a semiconductor or polymer core surrounded by a metal coating. We predict that composite materials containing these particles will have much larger enhancement of the nonlinear optical response than had previously been found by using semiconductor colloid suspensions or semiconductor - doped glasses. The enhancement is due to the surface plasmon resonance from the metal dielectric constant that increases the local field in the core material. The frequency of the resonance and the enhancement depend upon the particle shape and the coating thickness, as well as on the specific materials.

Also, we predict intrinsic optical bistability in these new materials and show that the threshold intensity for optical bistability can be greatly reduced by using the coated particles. We predict a switching intensity of silver coated GaAs particles below 100W/cm2

A review is given of the electrical and optical properties of hydrogenated microcrystalline silicon carbide (μc-SiC:H) films prepared by ECR (Electron Cyclotron Resonance) plasma chemical vapor deposition. The material produced with the ECR plasma technology has a very wide energy gap from 2 to 2.8 eV with good valency electron controllability, e.g., a dark conductivity as high as 10 Scmg− which is more than seven orders of magnitude larger than that of amorphous SiC:H.

Employing this material as a wide gap heterojunction window, 15.4% and 12.0% conversion efficiencies have been achieved with the structures of ITO/p type μc-SiC:H/n type poly-Si and p type vc-SiC:H/i type a-Si:H/n type Pc-Si:H heterojunction solar cells, respectively. The successful development of a visible light thin film light emitting diode show the promise of microcrystalline materials for optoelectronic applications.

Amorphous SiC:H thin films have been deposited on different substrates using metal-organic polymer solutions. The structure of the amorphous phase has been proposed as the rings of Si and C atoms with various sizes. Microcrystalline phase can be produced when fired at temperatures higher than 1000°C. 13C MAS-NMR shows the evidence of the C=C-double bonds. ESR results show the major defects in this material are C-dangling bonds. As predict, defects can be decreased by heat treatment in H2 atmosphere.

Thin films of diamond-like amorphous carbon were prepared by dc magnetron sputtering. A systematic variation in the physical properties of the films (mass density and electrical resistivity) was found as a function of sputtering power density. Chemical bonding and microstructure of the carbon thin films were investigated using electron energy loss spectroscopy (EELS) and Raman spectroscopy. Films grown at a lower power density were found to have more sp3 -bonded atomic sites and larger graphite microcrystals than films produced at higher sputtering power densities.

The transport properties of intrinsic micro-crystalline and amorphous SiGe films are investigated. In the amorphous system it is found that the electron lifetime is relatively independent of band gag while the electron mobility of a-Ge:H is a factor of ten less than that of a-Si:H. Micro-crystalline silicon films have greater excess photo-conductivity as compared to a-Si:H predominantly due to longer effective lifetimes. Films containing micro-crystalline silicon in a matrix of a-SiGe:H have been prepared and are found to have comparatively poor transport.

Crystallization of amorphous Sil−x.Bx alloy films by annealing is studied. Amorphous Sil−xBx. alloy films with composition of boron x ranging from 0.01 to 0.5 are deposited on Si substrates at a temperature of 480° in a low pressure chemical vapor deposition (LPCVD) system. Three films with the boron contents, 1%, 7% and 45%, are used in this study. The films are annealed in a nitrogen ambient for 30 minutes at temperatures between 600°C and 900°C. Raman spectra of the silicon vibrational mode serve as a indicator for the microstructure of the Sil−xBx, alloy films. Quantitative estimates of the volume fraction of the crystalline silicon component in respect to the amorphous silicon component in the films are calculated based on the silicon TO mode. The results show that while for the film with the boron content of 1% crystallization occurs at the annealing temperature of 500°C, the annealing temperature of 7000C is required to observe crystallization in the films with the boron contents of 7% and 45%. As the annealing temperature increases, the volume fraction of the crystalline component increases. For a given annealing temperature, the rate of crystallization depends inversely on the boron content in the films.

We have achieved the highest total area conversion efficiency for an integrated type 10cm × 10cm a-Si solar cell at 10.2%. This value is the world record for a 10cm × 10cm a-Si solar cell. For further improvement of conversion efficiency in a-Si solar cells, it is necessary to develop materials with high-photosensitivity in the long wavelength region and materials with high conductivity. We have developed a Solid Phase Crystallization (SPC) method of growing a Si crystal at temperatures as low as 600°C. Using this method, thin-film polycrystalline silicon (poly-Si) with higP-photosensitivity in the long wavelength region and Hall mobility of 70cm2/V sec was obtained and quantum efficiency in the range of 800,∼ lO00nm was achieved up to 80% in the n-type poly-Si with grain size of about 2μm. We also succeeded in preparing a device-quality p-type microcrystalline silicon (μc-Si) using the SPC method at 620°C for 3 hours from the conventional plasma-CVD p-type amorphous silicon (a-5i) withoul using any post-doping process. Obtained properties of μd=2 × 103 (.cm) and a high optical transmittance in the 2.0 ∼ 3.0 eV range are better as a window material than the conventional p-type μc-Si:H. Therefore, it was concluded that the SPC method is better as a new technique to prepare high-quality solar cell materials.

To improve the thermal stability of the Si heterojunction bipolar transistors (HBTs), we studied the effect of carbon and fluorine doping on μc-Si:H characteristics. We found that carbon doping suppresses crystalline growth and increases the hydrogen concentration in the film, and that fluorine atoms are more thermally stable than hydrogen atoms. We confirmed that carbon or fluorine doping is promising for use with the μc-Si:H HBT.

The dopant segregation at the polycrystalline silicon grain boundaries in device fabrication processes has been studied with a new approach using spreading resistance(SR) measurement, SIMS and cross-sectional TEM(XTEM). Phosphorus implanted LPCVD poly-Si films were annealed at 900°C-1000°C in N2 for 30min. Electrically active dopant concentrations obtained from SR measurements are constant in depth within the poly-Si films. On the other hand, the phosphorus concentration measured by SIMS is found to increase with increasing depth and to have linear relationships to reciprocal grain sizes observed by XTEM for all poly-Si films. The linear relationship indicates that the number of segregated phosphorus atoms per unit grain surface area at the grain boundaries is uniform throughout poly-Si films. Both phosphorus concentrations in the grains and at the grain boundaries are evaluated. The heat of segregation of 1.7eV is obtained from the annealing temperature dependence of the segregation ratio. Our results indicate that carrier concentration in the poly-Si film is more sensitive to annealing temperature in device fabrication processes. The carries concentration is determined by kinetics rather than by equilibrium segregation of dopants.

Films of in-situ phosphorus-doped hydrogenated microcrystalline silicon (n--μc-Si:H) were deposited by plasma enhanced chemical vapor deposition (PECVD) on Si(100) and fused quartz substrates over a range of substrate temperatures (100 - 500°C) and reactant gas dilutions (I - 100% of 1% PH3/SiH4 in H2) while maintaining a constant RF power density (0.1 W-cm−2) and total gas pressure (1 Torr). Some of the films were subjected to a rapid thermal anneal (RTA) at temperatures between 600- 1000°C for a duration of 10 seconds. The μ-Mc-Si:H films were characterized, before and after RTA, in terms of their microstructure, optical band-gap, electrical conductivity, and hydrogen and phosphorus content. The deposition rate was determined to be insensitive to substrate temperature and to decrease with increasing H2 gas dilution indicating that deposition kinetics are dominated by plasma chemistry and are not thermally activated. For pre-annealed films, cross-sectional TEM confirmed the presence of a mixed phase material at all deposition temperatures with gas dilutions ≤10%. The surfaces of thick films (>0.15 μm) were rough, giving them a hazy appearance, while thin μic-Si:H films (<0.15 μm) were smooth and mirror-like. The rough surfaces were correlated with voids and microcracks in the μuc-Si:H films observed by TEM. The optical band-gap of all pre-annealed films was 11.8eV and the electrical conductivity varied between 1 and 20 (Δ-cm)−l. The H content was found to be independent of gas dilution but decreased with increasing substrate temperature; the P content depended on both the gas dilution and substrate temperature, decreasing at high deposition temperatures. RTA was observed to significantly alter film morphology and microstructure, increase electrical conductivity, and decrease the optical band-gap.

μc-Si:H:F can be deposited by if plasma-CVD of fluorinated gas sources like SiF4 and SiH2F2, mixed with H2 and/or SiH4. However, this growth process is usually not selective: the layers are deposited on SiO2 as well as on Si substrates. In this paper, selective growth from SiF4 + SiH4 is reported. N+ Si layers were deposited on <100> Si and poly-Si with a conductivity up to 300 resp. 100 S/cm. The selective growth process was applied for Source and Drain regions of poly-Si thin film transistors on insulating substrate.

Selective growth of Si crystals over amorphous substrates, seeded by agglomerated single domained Si crystals is demonstrated. In this method, Si crystal seeds are periodically placed and selectively overgrown until impingement upon adjacent crystals, resulting in a matrix of large Si islands with controlled grain boundary locations. Si seeds are formed over amorphous SiO2 by the solid-state agglomeration phenomenon, and grown selectively up to 100 μm by CVD selective epitaxial growth technique. The grown crystals are classified in three crystalline forms of single crystals, primary twins, and multiple twins. However, most are single crystals with a specific orientation of (110) normal to the substrate surface.

The relation between the seed pitch and defect density of the laserrecrystallized SOI film was investigated. It was found that the defect density of the SOI increases as the seed pitch increases. The dependences of the laser scan speed and laser power on rotation angle of the SOI film were experimentally and numerically investigated. The crystal-axisrotation of the SOI film was considered to be due to the difference of the temperature between the top and bottom surface of the SOI film near the liquid-solid interface. A polysilicon heat sink structure with high thermal conductivity was newly proposed and was found to reduce the rotation in a small angle.

A set of analytical equations that accurately model the large-signal current-voltage and charge-storage characteristics of the poly-silicon thin film transistor (TFT) have been developed. The model is based on theories of conduction in materials with a bulkdistribution of gap states[l]. The equations are suitable for incorporation into a circuit simulator capable of transient-analysis of circuits, such as SPICE.

Transport and trapping effects on undoped and phosphorus-doped SIPOS films on n-type and p-type Si have been characterized by C-V-ω, I-V, DLTS and photo-induced microwave reflection techniques. Our C-V and DLTS data on undoped SIPOS indicate that interface traps with a density of 2 × 1012cm−2 eV−1 and a response time between 1 and 10 μsec exist near the midgap of the SIPOS. Photo-induced microwave reflection transient-waveforms show an order of magnitude increase in photoconductivity decay time with doped SIPOS films. Our data shows that trapping effects exist in doped SIPOS and that these traps could reduce the cutoff frequency of SIPOS emitter transistors.

In order to improve the efficiency of the amorphous silicon stacked solar cells, we have developed the preparation method of highly conductive very thin microcrystalline silicon n-layers. We have found that the addition of a small amount of Ar gas to deposition gases is effective to make microcrystallite size small. The obtained thin films were characterized by conductivity measurement, R-HEED observation and TEM observation.

This newly developed thin microcrystalline n-layers have been applied to the stacked solar cells. Increase of Jsc by 5-6% has been achieved because of the reduction of light absorption loss in n-layer without decrease of Voc and FF.