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Although little is known about the reaction mechanism between cyclopentasilane (CPS: cyclic Si5H10) and borane (BH3), the reaction product is known to be a liquid precursor for p-type semiconducting Si. Therefore, investigation of the reaction mechanism enables more functional material design and contributes to the realization of printable Si semiconductors. Here, we investigated the interaction between CPS and BH3 using density functional theory (DFT) calculations. The calculations showed the occurrence of a dehydrogenative condensation reaction with an energy barrier less than 10 kcal mol−1. CPS and BH3 act as Lewis bases and acids, respectively, and form somewhat stable reactant complexes with monobridged hydrogen bonds through electrostatic interactions between the positively charged Si atoms and negatively charged B atoms. The monobridged hydrogen bonds initiate dehydrogenation because they abstract other hydrogen atoms in the compound. Eventually, liquid-phase hydrosilanes with Si–B bonds remain as the reaction product. This reaction model and reaction products were also evaluated experimentally using nuclear magnetic resonance spectroscopy, gas chromatography, and gel permeation chromatography. Characterization of the printed Si film also showed that the reaction product can be used as an effective liquid precursor for p-type semiconducting Si.

The three-dimensional (3D) distribution of nanosized silicon (Si) crystallites within a hydrogenated nanocrystalline Si (nc-Si:H) material is examined by laser-assisted atom probe tomography (APT). The amorphous and crystalline phases in nc-Si:H are distinguished by obtaining the 3D density distribution of H atoms, because the former contains a high H density. The H content in the amorphous phase is estimated to be approximately 15 at% by APT, which is consistent with that obtained by infrared spectroscopy. Thus, the 3D analysis of H distribution via APT is a powerful method to visualize the real shape of nanosized crystallites within nc-Si:H materials.

Laser-assisted atom probe tomography was used to identify the impurity distribution in Si heterojunction (SHJ) solar cells composed of thin doped/intrinsic amorphous Si layers on the textured surface of a crystalline Si wafer. A site-specific lift-out technique involving a focused ion beam enabled the selection of a ∼2 × 2 μm2 area on an arbitrary pyramidal surface. The distributions of B, P and C in the amorphous Si layers introduced by p-type (trimethyl-borane or diborane) or n-type (phosphine) dopant gases were investigated. Standard guidelines for the assessment of the H content in amorphous Si of SHJ solar cells were provided.

Power conversion efficiency of thin-film microcrystalline silicon solar cells has been remarkably improved recently: from 10.1% to 11.8%. Front transparent conductive oxide (TCO) films have played an important role in this efficiency improvement. In this study, the impact of the front TCO films was investigated by comparing microcrystalline silicon solar cells with In2O3:Sn films grown by sputtering and ZnO:B films grown by metal-organic chemical vapor deposition (MOCVD). Improvement mechanisms in open-circuit voltages and fill factors in solar cells are investigated and discussed.

A localized plasma confinement chemical vapor deposition (LPC-CVD) method with special cathode structures was proposed to solve problems of stability and uniformity of plasma under high pressure (>;1000 Pa). The initial conversion efficiency achieved by LPC-CVD for an a-Si/μc-Si tandem solar cell was 10.4% (1 cm2) for a 550 × 650 mm2 substrate at the deposition rate of 2.2 nm/s. Since then, we have been developing high-rate deposition technology for 1100 × 1400 mm2 substrates (Generation 5.5 (G5.5) size). A-Si/ μc-Si tandem solar modules have been achieved with an efficiency of 11.1% (initial) and 10.0% (stable) and a deposition rate of 2.4 nm/s on a G5.5-size substrate.

We have fabricated high-efficiency a-Si/µc-Si tandem solar cells and modules with a very high µc-Si deposition rate using Localized Plasma Confinement CVD to give very high-rate deposition (>2.0 nm/s) of device-grade µc-Si layers. For further progress in productive plasma-CVD techniques, we have studied plasma phenomena by combining newly developed plasma simulation and plasma diagnosis techniques that reveal the importance of non-emissive atomic hydrogen. We also have proposed a model of defective µc-Si formation on highly textured substrates in which the atomic H in plasma is assumed to play an important role. We are also developing a non-vacuum deposition technique that we term “Liquid Si Printing.” A new record conversion efficiency for HIT solar cells of 24.7% has been achieved using a very thin c-Si wafer (Thickness: 98 µm, Area: 102 cm2).

We successfully achieved the poly-crystallized coatings of bio-active hydroxyapatite on titanium plates. We used several ceramic HAp targets sintered at a temperature of 500°C, 700°C, 900°C and 1100°C, and irradiation by KrF excimer laser at a fluence of about 4J/cm2. The depositions were performed under 1Torr H2O atmosphere at room temperature. In this condition, a poly-crystallized HAp layer was formed only using a target sintered at 900°C. We estimated the charged fragments from these targets by a simple ion-probe collection and found that the energy distribution of charged fragments depended on the densities of the targets.

チタン（Ti）あるいはTi合金で作製されたインプラント材へのハイドロキシアパタイト（HAp）被膜形成は，インプラント材の生体親和性を高める技術の一つである．HAp被膜は，生体中でその性質を維持するためには高い結晶性を必要とする．この被膜の成膜法の一つとして，レーザーを用いたパルスレーザー堆積（PLD）法がある．PLD法によるHAp被膜形成では，被膜を結晶化するために成膜中，基板を高温（500～800℃）で加熱する．しかしながら，一般的なHAp被膜形成の場合，水雰囲気中で成膜するため基板上に酸化層が生成される．この酸化層は，HAp被膜とTi基板との間の密着強度を弱める．我々は，PLD法を改良したレーザーアシスト・レーザーアブレーション（LALA）法を開発した．本研究ではLALA法で作製したHAp被膜の密着性の原因について調べた．その結果，LALA法はTi基板に酸化層を形成しないことがわかった．さらに，基板表面を粗面化することがわかった．これらから，LALA法は，HAp被膜の密着強度を高める優れた方法として期待できる．

In the recent 3 years, power conversion efficiencies in thin-film microcrystalline silicon solar cells were remarkably improved from 10.1% to 11.8%. Front transparent conductive oxide films play an important role in this efficiency improvement. In this study, the impact of the front transparent conductive oxide films were investigated by comparing microcrystalline silicon solar cells with In2O3:Sn films grown by sputtering and ZnO:B films grown by metal-organic chemical vapor deposition. The origins of the improvement in open circuit voltages and fill factor in solar cells were investigated and discussed.

In order to create the implant material which has high biocompatibility, a new hydroxyapatite (HAp) coating method, the laser-assisted laser ablation (LALA) method, has been developed. In this method, control of assist laser irradiation timing (delay time after an ablation laser irradiation) is very important for the quality of a HAp coating layer. We studied the influence of the timing on adhesion strength , crystallinity and Ca/P value of the HAp coating. Quality of the HAp coating layer obtained at a delay time of a few microseconds was extremely high. On the other hand, the layer obtained over 10 microseconds had more amorphous component and contained other calcium phosphate compounds from HAp. Using the present method, we succeeded in fabricating thin film (≦1 μm) of HAp with high crystallinity.

Hydrogen (H) atom kinetics has been investigated in capacitively coupled very high frequency (VHF) discharges at powers of 16–780 mW cm–2 and H2 gas pressures of 0.1–2 Torr. The H atom density has been measured using vacuum ultra violet absorption spectroscopy (VUVAS) with a micro-discharge hollow cathode lamp as a VUV light source. The measurements have been performed in two different electrode configurations of discharges: conventional parallel-plate diode and triode with an intermediate mesh electrode. We find that in the triode configuration, the H atom density is strongly reduced across the mesh electrode. The H atom density varies from ~1012 cm−3 to ~1010 cm−3 by crossing the mesh with 0.2 mm in thickness and 36% in aperture ratio. The fluid model simulations for VHF discharge plasmas have been performed to study the H atom generation, diffusion and recombination kinetics. The simulations suggest that H atoms are generated in the bulk plasma, by the electron impact dissociation (e + H2 e + 2H) and the ion–molecule reaction (H2 + + H2 + H). The diffusion of H atoms is strongly limited by a mesh electrode, and thus the mesh geometry influences the spatial distribution of the H atoms. The loss of H atoms is dominated by the surface recombination.

Photovoltaic Power Generation Technology Research Association (PVTEC) has organized the consortium of one national research institute and five private companies, which has been supported technically by three universities. It has developed thin film Si PV technologies of improving conversion efficiency and developing a high-productivity Si deposition apparatus. For improving the conversion efficiency, the stabilized efficiency of 10.1% for an a-Si:H cell, 11.0% for a μc-Si cell, and 12.2% with light induced degradation ratio of less than 3% have been achieved, respectively. We have also successfully developed a plasma-enhanced chemical vapor deposition (PECVD) machine, which can deposit high-quality μc-Si films uniformly on a large-scale substrate with high deposition-rate by using very high frequency (VHF) plasma.

The technology to make high-quality, high-reliability solar modules with a high deposition rate for μc-Si thin-film is a problem for the industrialization of low-cost, high-conversion-efficiency a-Si/μc-Si tandem structure solar modules. Sanyo has solved this problem by developing an original CVD technique called Localized Plasma Confinement CVD and a new evaluation method for μc-Si thin film. A stabilized conversion efficiency of 10.0% was achieved for an a-Si/μc-Si tandem structure solar module, and a deposition rate of 2.4 nm/s for μc-Si thin-film was attained on a Gen. 5.5 full-size glass substrate. To obtain a higher conversion-efficiency a-Si/μc-Si tandem structure solar module, fundamental studies of μc-Si thin-film have been performed, and a stabilized conversion efficiency of 10.5% (Initial solar module conversion efficiency: 12.0%) has been achieved on a large-area glass substrate. Furthermore, in the study of this development, the highest stabilized conversion efficiency of 12.0% (Initial conversion-efficiency: 13.5%) was attained. Module reliability tests confirmed by IEC 61646 Ed. 2 revealed that the performance of the module is adapted. These high-performance a-Si/μc-Si tandem structure solar modules were prepared by using the knowledge of our thin-film and module technologies.

We have been developing original technologies for Localized Plasma Confinement (LPC) CVD method. LPC-CVD method achieves both a high deposition rate and a high conversion efficiency. From the results of IR analysis and Raman spectroscopy for µc-Si i-layer thin films, it was suggested that the combination of high stretching mode fractions in IR spectra and Raman crystallinity may have a correlation with the conversion efficiency of a-Si/µc-Si tandem cells. An R&D line for processing a-Si/µc-Si solar modules on G5.5 size glass substrates (1100 × 1400 mm2) has been constructed. Module efficiency of 11.1% (Initial) and 10.0% (Stable) has been achieved with a film deposition rate for the µc-Si i-layer of 2.4 nm/s on a G5.5 size substrate.

Hydroxyapatite (HAp) is a biological and bioactive material, which has promise as a coating material for orthopedic and dental implants. Some HAp coating methods have been investigated and the pulsed laser deposition (PLD) method is one of the most candidate. Previous PLD researchers deposited the HAp coatings on heated Ti and Ti-alloy substrates in order to crystallize the coatings. However, the deposition condition, high substrate temperature and water atmosphere, should promote the oxidation of the substrate surface prior to the growth of the HAp layer, which degrades the adhesion of the coating to the substrate. Therefore, HAp coatings should be deposited at lower temperature to avoid extensive oxidation of the substrates.

The potential of high-rate growth of high-quality microcrystalline silicon (µc-Si:H) films for solar cell applications is investigated by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) under a high-pressure SiH4 depletion condition. It is found that the morphology of textured substrates plays an important role in not only light trapping but also µc-Si:H film growth. A high conversion efficiency of 11.1% is attained in a substrate-type µc-Si:H cell on a substrate with honeycomb textures, which has rounded concaves in a honeycomb arrangement with an appropriate period. It is also clarified that ZnO:B films grown by metal organic chemical vapor deposition (MOCVD) are beneficial in terms of carrier collection compared with the standard In2O3:Sn (ITO) film grown by sputtering. On the basis of these findings, a new world-record µc-Si:H cell with a certified conversion efficiency of 11.8% is developed with a relatively high deposition rate of 1 nm/s.

We report a high-efficiency triple-junction thin-film silicon solar cell fabricated with the so-called substrate configuration. It was verified whether the design criteria for developing single-junction microcrystalline silicon (μc-Si:H) solar cells are applicable to multijunction solar cells. Furthermore, a notably high short-circuit current density of 32.9 mA/cm2 was achieved in a single-junction μc-Si:H cell fabricated on a periodically textured substrate with a high-mobility front transparent contacting layer. These technologies were also combined into a-Si:H/μc-Si:H/μc-Si:H triple-junction cells, and a world record stabilized efficiency of 13.6% was achieved.

Bio-active hydroxyapatite (HAp) coatings were deposited by the pulsed laser deposition method using a KrF excimer laser. We changed the sintered temperature of HAp ceramics target and successfully deposited the poly-crystalline HAp coating layer at room temperature.