新船 幸二

Three different salt crystals (K2SO4, KCl, and Na2SO4·10H2O) were produced via batch cooling and continuous crystallization using a bench-scale crystallization device, in order to elucidate the mechanism of inclusion of the mother liquor as a function of crystal size. The inclusion ratio of the mother liquor was higher at small sizes and decreased with crystal growth. All results were represented by the previously proposed model of core-aggregation and shell-growth processes for the three different salt crystals. Crystals with small Vickers hardness aggregated with each other, and the inclusion ratio of the mother liquor of aggregated grown crystals was high for all three salt crystals tested herein.

The interface properties of strongly correlated electron system/band semiconductor junctions were investigated in the La_1−xSr_xVO₃/p-Si(100) structure. Spectroscopic observations show that the electronic structure of the interface is typical of insulator/semiconductor junctions for x ≤ 0.2 and Schottky junctions for x ≥ 0.25. For the forward current density–bias voltage (J–V) characteristics, energy barriers that were otherwise unexplainable by spectroscopy were estimated from the thermionic emission model fitting of the J–V characteristics, indicating that the injected carriers from Si to La_1−xSr_xVO₃ can also feel the correlation force of Coulomb repulsion at the interface.

Continuous crystallization via indirect cooling of potassium aluminum sulfate dodecahydrate (KAl(SO4)(2)center dot 12H(2)O) was carried out using a draft tube-type crystallizer with a circulation flow path. The crystallizer was equipped with a newly designed system to monitor the degree of supersaturation in the circulation channel. The average degree of supercooling and growth rate were measured. The crystal growth rates calculated by the population balance model and the supersaturation monitor were different but close. The average supersaturation calculated from the supercooling degree and the solubility data in the literature was 0.19 g per 100 g H2O. This system is also expected to be applied to industrial crystallization where impurities are present.

To understand the inclusion of mother liquor in crystals at different sizes, the continuous crystallization of potassium sulfate was investigated. A bench-scale crystallizer of the draft-tube type was employed for both batch cooling and continuous crystallizations. A standard solution of potassium sulfate was employed as the saturated solution at 323 K. The batch cooling crystallization was first performed at 283 K at a rate of 5 K/h, after which the continuous crystallization was performed at 283 K at two different residence times. The crystal size distribution (CSD) of potassium sulfate crystals and the inclusion ratio of mother liquor in the crystals at different sizes were measured. The average size of the crystals was approximately 400-500 mu m, and the inclusion ratio was less than 1% for all sizes; however, the small and large crystals contained a considerable amount of mother liquor, and the specific crystals that exhibited the lowest inclusion ratios were investigated. Moreover, an impurity distribution model for the suspension crystals was proposed based on coreaggregation and shell-growth processes.

A new method for determining the liquidus and solidus pressures of mixtures of C18's unsaturated fatty acids at constant temperatures was proposed, and three binary isothermal SLE data under high-pressure were systematically measured in this study. The liquidus and solidus temperatures of oleic acid, linoleic acid and alpha-linolenic acid commonly rise above their normal melting temperatures when pressure is increased. This new high-pressure experimental system can closely track pressure in real time during pressure swinging changes, making it simple to measure liquidus and solidus pressures using this dynamic measurement method due to fast responsiveness of pressure. In this study, the liquidus pressures of pure oleic acid, linoleic acid, alpha-linolenic acid and three binary mixtures consisted of oleic acid, linoleic acid alpha-linolenic acid at constant temperature were determined. The isothermal SLE were first correlated based on a simple thermodynamic model. (C) 2021 Elsevier Ltd.

The separation of the binary unsaturated fatty acids C18:1 + C18:2 system was examined by high-pressure crystallization at 298 K (25 °C). The binary fatty acid mixture containing 0.8 mol fraction of C18:1 was packed in the glass cell with a free piston, and then pressurized by an aqueous ethanol solution around the glass cell up to 200 MPa. The complete solid mixture was obtained after cooling at 253 K (- 20 °C) as a depressurized binary solid. The solid was divided into four parts, and the composition of C18:1 was analyzed at each part of the solid using a refractometer, which revealed there was a composition distribution throughout the solid with C18:1 crystallized one-directionally from the top to the bottom of the cell. High-pressure crystallization could be effective for the separation of binary fatty acids.

In this study, batch crystallization via indirect cooling and continuous crystallization via direct and indirect cooling of phosphoric acid hemihydrate (H3PO4.1/2H2O) from the mixed acid solution of phosphoric acid and acetic acid are performed. In batch crystallization, needle-shaped crystals are obtained, and the impurity concentration of acetic acid in the crystals is 4.2 wt%. Primary nucleation occurred under a high degree of supersaturation, and the metastable zone width for secondary nuclei is narrow. In contrast, in continuous crystallization via indirect cooling, scaly crystals are obtained, and the acetic acid impurity concentration therein is 2.0 wt%. Additionally, continuous crystallization via direct contact cooling is performed, the crystal shape and impurity concentration under direct cooling are similar to those under indirect cooling, suggesting the possibility to downsize the apparatus. Through utilization of the equipment and approach elaborated herein, the correlation between the operating conditions and crystal quality can be assessed.

The biodiesel fuel ethyl oleate (fatty acid ethyl ester, FAEE) was produced using Novozym® 435 (immobilized lipase) by transesterification of a mixture of ethanol and triolein in a fixed-bed reactor operated in circulating batch mode. The miscibility of the mixtures during transesterification was predicted thermodynamically and the conversion ratio of triolein was studied as a function of reaction time. The yield of ethyl oleate increased when the feed molar composition of ethanol was increased. The glycerin by-product could be removed from the enzyme particles by the circulating feed mixture. The inactivation of Novozym® 435 by glycerin was also examined in the circulating batch mode experiments, and an effective reaction model was proposed to describe the inactivation of Novozym® 435 and ethanol effect during the transesterification reaction by using the modified Michaelis-Menten equation.

As a method for efficiently recovering marine organisms, which is expected as a resource for next generation biofuels, crystallizing concentration which can be considered as application of melt crystallization was studied. An operation of forming an ice phase from the outer wall surface to the central portion in the crystallizer was carried out by a cooling jacket with circulating solution. As the operation conditions, the stirring rotation number, the cooling temperature, and the freezing rate were varied to clarify the influence on the concentration ratio of Chaetoceros gracilis in the solution, the dilution ratio of Chaetoceros gracilis in ice, and the solid-liquid distribution coefficient of Chaetoceros gracilis measured experimentally in this study. Furthermore, it is suggested that the solid-liquid distribution coefficients are correlated by two kinds of solid-liquid distribution coefficients models, and concentration by high-speed freezing is also efficient as a result of comparison of the two models.

The present study evaluates the lipase (Novozym 435)-catalyzed transesterification of triolein and methanol mixtures to generate fatty acid methyl esters (FAMEs) using dimethyl ether (DME) in a batch reactor and a continuous pipe reactor. The addition of DME facilitated the preparation of homogeneous mixtures of triolein and methanol. The effect of the Novozym 435 and DME contents in the feed mixtures on the time-course of FAME production was analyzed. With increasing contents of Novozym 435 and DME in the feed mixtures, the FAME concentration increased more rapidly in the batch reactor than in the continuous reactor. The feed flow rate and DME content were varied, and the FAME concentration at the outlet of the pipe reactor was measured with variation of the residence time and DME content. Increasing the DME content in the feed mixtures and the residence time led to a more rapid increase in the FAME concentration for the batch reactor than that in the continuous pipe reactor.

We studied the effective net charge density (Q(eff)) of strontium silicate (SrxSiOx+2, x = 1, 2, 3) films grown on silicon (Si) (100) substrates. The SrxSiOx+2 layers were deposited from a Sr2SiO4 polycrystalline target by pulsed laser deposition, and then annealed at 400-600 degrees C in an oxygen atmosphere with a tube furnace. The Qeff values of the SrxSiOx+2/Si (100) samples were obtained from the shift in the voltage of the flat band state in their capacitance-voltage curves. The SrxSiOx+2/Si (100) samples with a thickness of 15 nm annealed at 400 degrees C showed the maximum Q(eff)/q value of 1.03 X 10(13) cm(-2), where q is the elementary charge. With increasing annealing temperature, the SrxSiOx+2 layer penetrated into the Si (100) substrate. This penetration may degrade the interfacial properties and decrease the Qeff value of the layers. For all the samples, the charges concentrated near the SrxSiOx+2/Si (100) interface. Our results suggest that anion and cation migration plays an important role in charge generation at the SrxSiOx+2/Si (100) interface, consistent with the findings of a previously reported molecular dynamics calculation. Published by AIP Publishing.

The authors studied the correlation between the chemical bonding (CB) states and fixed charge (FC) states of Sr-silicate films grown on Si(100) substrates [Sr-silicate/Si(100)]. The Sr-silicate/Si(100) samples were synthesized by silicate reaction of SrO layers on the Si substrates through the diffusion of Si atoms from the substrates by thermal annealing in oxygen atmosphere. The CB states and the FC states of the Sr-silicate/Si(100) samples were obtained from their O 1s core-level x-ray photoemission spectra and the shift in voltage from the flat band state in their capacitance-voltage curves, respectively. Peak fittings of the O 1s core-level spectra for each sample were carried out with the three components of Si-O, Si-O-Sr, and Sr-O bonds to determine the CB state. The thin Sr-silicate layers were mainly constructed of the Si-O-Sr component. With increasing thickness, the amount of Si-O-Sr component decreased while that of Sr-O increased. The thickness dependency of the FC density showed a good agreement with that of the Si-O-Sr component, revealing a clear correlation between FC and Sr-O-Si bonding. Our results suggest that silicate bonding plays an important role in FC generation in Sr-silicate systems. (C) 2016 American Vacuum Society.

We investigated the room temperature growth of HfO2 layers on Si substrates by pulsed laser deposition under ultra-high vacuum conditions. The laser fluence (LF) during HfO2 layer growth was varied as a growth parameter in the experiments. X-ray photoemission spectroscopy (XPS) was used to observe the interface chemical states of the HfO2/Si samples produced by various LFs. The XPS results indicated that an interface Hf-silicate layer formed, even at room temperature, and that the thickness of this layer increased with increasing pulsed LF. Additionally, Hf-Si bonds were increasingly formed at the interface when the LF was more than 2 J/cm(2). This bond formation process was related to decomposition of HfO2 to its atomic states of Hf and O by multiphoton photochemical processes for bandgap excitation of the HfO2 polycrystalline target. However, the Hf-Si bond content of the interface Hf-silicate layer is controllable under high LF conditions. The results presented here represent a practical contribution to the development of room temperature processing of Hf-compound based devices. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

We fabricated a Y2O3-ZrO2 film (YZO) on Al2O3 to achieve the field effect passivation with high negative fixed charge densities on p-type Si. The surface recombination velocity was improved down to 30cm/s after annealing at 400 degrees C. This improvement can be attributed to the effective fixed charge enhancement while the interface state densities were kept almost constant. A high thermal tolerance of over 600 degrees C upon inserting a 2-nm-thick ZrO2 layer between the YZO and Al2O3 interface was confirmed. This result showed that the ZrO2 layer acts as a protective barrier to prevent Al and Y interdiffusions. Annealing at a higher temperature of 800 degrees C resulted in interface degradation and YZO crystallization, which led to the deterioration of the passivation properties. (C) 2016 The Japan Society of Applied Physics

The present study investigates the charge-discharge processes of a Plante lead-acid battery performed under atmospheric pressure and 10 MPa. The ampere-hour efficiency of the lead electrodes was substantially increased by the secondary formation of the Plante electrode, and the ampere-hour efficiency under 10 MPa was slightly higher than that under atmospheric pressure. The active PbSO4 crystals on both electrodes were observed by SEM at different currents, and the morphology and crystal size distribution (CSD) were obtained. Active PbSO4 crystals nucleated and grew during discharging; whereas, they disappeared during charging. This is similar to the crystal behavior during continuous crystallization in a battery. Therefore, a simple population balance model was used to express the CSD of PbSO4 crystals on both electrodes. The CSD of both electrodes were similar at 10 MPa, but the CSD of the positive electrode was different from the CSD of the negative electrode. The current density on both electrodes was balanced under 10 MPa.

Anti-solvent crystallization from a ternary mixture was examined by an NpT ensemble molecular dynamics simulation. The co-solvent and anti-solvent effects were represented by the Lennard-Jones interaction energy parameter, epsilon(ij). The homogeneous binary solution of the solute and solvent was achieved at a constant temperature and pressure. Anti-solvent crystallization was introduced by changing some co-solvent molecules to anti-solvent molecules, immediately. The configuration of solute molecules was investigated by using the radial distribution function, g(r), and the local composition, X-L. The value of epsilon(ij) affected the configuration of the solute molecules significantly; the decrease in epsilon(ij) provided the localization and crystallization of the solute molecules. The composition of the anti-solvent molecules in the solution also affected the configuration of the solute molecules; the increase in the anti-solvent composition produced the crystal structure of the solute molecules more rapidly. These qualitative results corresponded well to anti-solvent crystallization. The radial distribution function represented the crystal structure for solute molecules, and the local composition of the solute was increased from the bulk composition as the effect of the anti-solvent increased. We proposed that the time variation of the local composition of the solute represents the temporal development of the crystal structure and the time to crystallization well. (c) 2015 Elsevier B.V. All rights reserved.

The passivation properties and band structures in aluminum oxide (AlOx) deposited by ozone-based atomic layer deposition (ALD) at room temperature on p-type crystalline silicon were investigated by X-ray photoelectron spectroscopy (XPS). The effective carrier lifetime depends on the thickness of AlOx films, since the field effects induced in the films by fixed charges depend on film thickness. The fixed charges are different by two orders of magnitude between films with thicknesses of 10 and 30 nm. At the 30-nm-thick AlOx/Si interface, the completely accumulated band bending of the Si surface was observed. On the other hand, a thin depletion layer was formed at the 10-nm-thick AlOx/Si interface. From the time-dependent XPS measurements, a hole trap was observed toward AlOx, in which trapping centers existed. (C) 2015 The Japan Society of Applied Physics

Aluminum oxide (AlOx) films were deposited by mist chemical vapor deposition (MCVD) in air for p-type crystalline silicon, and the effects of the deposition temperature (T-dep) and AlOx film thickness on the maximum surface recombination velocities (S-max) were evaluated. It was found that S-max was improved with increasing T-dep. The AlOx film deposited at 400 degrees C exhibited the best S-max value of 2.8cm/s, and the passivation quality was comparable to that of AlOx deposited by other vacuum-based techniques. S-max was also improved with increasing film thickness. When the film thickness was above 10 nm, S-max was approximately 10 cm/s. From the Fourier transform infrared spectra, it was found that the AlOx films deposited by MCVD consisted of an AlOx layer and a Si-diffused AlOx layer. In addition, it is important for the layers to be thick enough to obtain high-quality passivation. (C) 2015 The Japan Society of Applied Physics

Recently, excellent surface passivation has been achieved for both p- and n-type silicon solar cells using AlOx/SiNx:H stacks deposited by atomic layer deposition and plasma-enhanced chemical vapor deposition. However, alternative materials and deposition methods could provide practical options for large-scale manufacturing of commercial solar cells. In this study we demonstrate that AlOx/AlNx stacks fabricated by reactive radio-frequency magnetron sputtering can provide fairly good surface passivation (S-max of similar to 30 cm/s) regardless of AlOx thickness, which is found to be due to the high negative fixed charge density (Q(eff) of -2.8 x 10(12) cm(-2)) and moderately low interface trap density (D-it of 2.0 x 10(11) eV(-1).cm(-2)). The stacks also show fairly good antireflection performance in the visible and near-infrared spectral region. The demonstrated surface passivation and antireflection performance of in situ reactively sputtered AlOx/AlNx stacks make them a promising candidate for a surface-passivating antireflection coating on silicon solar cells. (C) 2015 The Japan Society of Applied Physics

We fabricated Y2O3-ZrO2 composition film (YZO) on Al2O3 for the field effect passivation with high negative fixed charge densities on p-type Si. The surface recombination velocity was improved down to 30 cm/s after annealing at 400 degrees C. High thermal tolerance was confirmed over 600 degrees C by inserting 2-nm-thick ZrO2 layer between YZO and Al2O3 interface. This result showed ZrO2 layer work as protecting barrier of Al and Y interdiffusions.

The photoluminescence properties of small-angle grain boundaries (SA-GBs) with various misorientation angles were evaluated before and after Fe contamination. Comparison of SA-GBs with the same misohentation angle showed that the D-a1 band at 0.78 eV remain the same before and after the Fe contamination. At the SA-GBs with the misorientation angle of 5 degrees, a strong emission existed at 0.87 eV, which has been reported as an oxygen-precipitation-related peak. The emission of this high-energy region became weaker and shifted toward lower energy for a smaller misorientation angle. The high-energy emission became weak after the Fe contamination. It is considered that the Fe contamination affected the PL spectra originating from oxygen precipitates. (C) 2014 The Japan Society of Applied Physics

© 2014 IEEE. We investigated stacking double layer structure, the Y2O3-ZrO2composite film (YZO) on AlOx, for the field effect passivation with high negative fixed charge densities on p-type Si. The composition spread YZO films were deposited at room temperature by using combinatorial sputtering technique. The fixed charge densities were extracted from the flat band voltage shift in the capacitance-voltage characteristics. The as-deposited ZrO2film incorporated with 15% Y2O3stacking on the ALD AlOxstructure showed the highest negative fixed charge of -1.9 × 1012cm-2. The field effect passivation can be controlled by the negative fixed charges in the YZO film depending on the composition and dipole uniformly formed at AlOx/Si interface. After annealing in the oxygen atmosphere, passivation properties deteriorated caused by the Al diffusion at the YZO/AlOxinterface.

To study the impact of annealing on the nickel distribution and recombination activity at Sigma 3(n) coincident site lattice grain boundaries (CSL-GBs) in multicrystalline silicon, synchrotron-based X-ray analysis and the electron beam induced current method were performed before and after annealing. For low Sigma boundaries, the interfacial symmetry at GBs strongly affects the recombination activity and nickel segregation. High Sigma(>= 81) boundaries are always recombination-active even without nickel segregation. Therefore, nickel is not a dominant factor of recombination activity at GBs. The behaviors of GBs in relation to nickel segregation before and after annealing are found to be affected by other neighboring GBs, triple junctions, or intragrain strain defects. (C) 2014 The Japan Society of Applied Physics

The effects of interface properties such as a negative fixed charge density and an interface trap density on the surface passivation of crystalline Si by O-3-based batch ALD AlOx were studied. High-quality surface passivation with S-max of similar to 10cm/s was obtained from the AlOx samples deposited at 200 degrees C after annealing. This feature is attributed to the excellent field effect passivation by the high negative fixed charge density of similar to-5 x 10(12)cm(-2) and chemical passivation, which reduces the interface trap density to similar to 1 x 10(11)eV(-1)cm(-2). The annealed AlOx samples deposited at 200 degrees C also show high thermal stability during firing at 850 degrees C. Additionally, we found that the formation of a thin SiOx interlayer is essential for the formation of a high negative fixed charge density that induces strong field effect passivation, and that defect passivation at the Si/SiOx interface by diffused hydrogen from AlOx layers is the origin of chemical passivation. (C) 2014 The Japan Society of Applied Physics

We studied the structure of ozone-based atomic layer deposited aluminium oxide (AIO(x)) films as a passivation layer for p-type crystalline silicon (c-Si) solar cells and focused on the differences in the structure by the production conditions of AIO(x) films. Carbon (C)-related groups such as methyl, hydroxyl, and carboxyl groups which originate from the aluminium source, trimethylaluminium, were only found in the AIO(x) film deposited at room temperature (AT-sample). By post-deposition thermal annealing (PDA), the C-related groups were desorbed from the film and a part of their space remained as voids. The C-related groups were not found in the films deposited at 200 or 300 degrees C (heated-samples) since they were desorbed during the deposition. Even though C-related groups did not exist in the both RT- and heated-samples after PDA, the structure of the AIO(x) film of the RT-sample was different from that of the heated-sample. (C) 2013 The Japan Society of Applied Physics

To investigate the effect of initial oxidized layer condition on passivation quality of AlOx films deposited at room temperature by means of ozone-based atomic layer deposition technique, crystalline silicon substrates were exposed to ozone before deposition. This ozone exposure pre-treatment increased the thickness of over-layer as compared with standard samples, and deteriorate interface quality of as-deposited samples. For 10nm-thick samples, the ozone exposure pre-treatment is effective for generation of negative fixed charges. The effective lifetime of the sample with ozone exposure and post-deposition wannealing is 1.8 msec at the injection level of 10(15) cm(-3). For 30nm-thick samples, ozone exposure pre-treatment improves the effective lifetime.

Recombination properties at small-angle grain boundaries (SA-GBs) in multicrystalline silicon were evaluated. After Fe contamination, the electron-beam-induced current (EBIC) contrast at most SA-GBs became stronger, especially at >1.5 degrees. After Al gettering, EBIC contrast of most <1.5 degrees SA-GBs became as weak as before contamination. Then, some EBIC contrast of >1.5 degrees SA-GBs showed comparable contrast before gettering. In addition, there were SA-GBs which have different recombination properties even with the same misorientation angle. Between these SA-GBs, there were differences in the rotation axis, boundary direction, and existence of defects. The associativity of metals might be affected by the existence of defects caused by these differences. (C) 2012 The Japan Society of Applied Physics

We have investigated the effects of deposition temperature and post-annealing on the passivation performance of AlOx films deposited by O-3-based atomic layer deposition for crystalline Si. We found that the dramatic enhancement in the passivation performance of room-temperature deposited AlOx films by post-annealing is due to the phase transformation of aluminum silicate to mullite in an AlOx interlayer and the resulting self-aligned AlOx/SiOx interface. This result is interesting for the fabrication of high-performance silicon solar cells with AlOx passivation layers. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3701280]

Although crystalline silicon is widely used as substrate material for solar cell, many defects occur during crystal growth. In this study, the generation of crystalline defects in silicon substrates was evaluated. The distributions of small-angle grain boundaries were observed in substrates sliced parallel to the growth direction. Many precipitates consisting of light elemental impurities and small-angle grain boundaries were confirmed to propagate. The precipitates mainly consisted of Si, C, and N atoms. The small-angle grain boundaries were distributed after the precipitation density increased. Then, precipitates appeared at the small-angle grain boundaries. We consider that the origin of the small-angle grain boundaries was lattice mismatch and/or strain caused by the high-density precipitation. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3700250]

We investigated behaviors of Fe and Ni at crystalline defects in multi-crystalline silicon by intentional contamination and phosphorus (P) gettering processes. After contaminations, EBIC contrasts became stronger at Sigma 27 and Random grain boundaries (GBs), and at small-grain boundaries (SA-GBs) with > 1 degrees misorientation angles. After P gettering processes, EBIC contrasts recovered as low as those before metal contamination at most GBs and SA-GBs. However, some Sigma 27, Random GBs and SA-GBs with > 1 degrees misorientation angle remain high contrast. Defect properties such as boundary orientations or tilt and twist components consisting misorientation angles might affect on the minority carrier recombination.

For the purpose of this work, several types of waste coolants from fixed-abrasive wire sawing (FAS) were filtrated, and the characteristics of the coolants and the retrieved solid materials were investigated. The all coolants consisted of water and glycol series with the boiling temperature of around 200 degrees C. However, the viscosity of each coolant were different due to the difference in the ratio of coolant components. Experimental results of pressurized filtration can be explained by a rate equation which we proposed. The concentration of diamond in the retrieved solid materials was less than 0.2wt%. Metal contents in the retrieved Si were measured by an inductively coupled plasma mass spectrometry (ICP-MS). The result indicated that quality of the retrieved Si is sufficient for the use as feedstock. The shaped Si was easily melted in a resistance heating furnace. We concluded that the Si powders in waste coolants from F AS can be used as feedstock.

We investigated the correlation between C incorporation and defect generation in quasi-single crystalline silicon ingots. The substitutional carbon concentration and etch pit density in the ingot fabricated with atmosphere control to suppress C incorporation were much lower than those in the ingot fabricated without controll. In addition, the precipitates consisted of C, N and Si were confirmed in the ingot fabricated without control. After the precipitation, small-angle grain boundaries (SA-GBs) were generated. We consider that the precipitation were the origin of SA-GBs, therefore the crystalline defect density can be decreased by reducing the incorporation of C impurities during crystal growth.

Interactions between intra-grain defects and metal impurities in multicrystalline silicon (mc-Si) were evaluated. After metal contaminations, EBIC contrasts at > 1.5 degrees SA-GBs were more enhanced than those at < 1.5 degrees SA-GBs, and the order was Fe/1000 degrees C > Ni/1000 > Ni/600 degrees C. These results might attribute to Fe atoms form deeper energy levels of recombination centers than Ni atoms and the gettering abilities at SA-GBs depend on the misorientation angles. Many dark spots were observed in EBIC images in the Ni/600 degrees C. Since the dark spots corresponded to the etch pits, the dark spots might be dislocations decorated with Ni. The gettering abilities of SA-GBs depended on the misorientaion angles, and the recombination properties at SA-GBs and dark spots, such as small defects after metal contamination were different by annealing temperatures and the types of metal impurities.

We evaluated the properties of crystalline defects in silicon substrate, and clarified the origin of small-angle grain boundaries. In order to eliminate the effects of grain boundaries, the ingot was fabricated by unidirectional solidification technique with seed crystal. In single-crystalline region, Sigma 3 twin boundaries and SiC precipitates were observed near the seed crystal. No obvious correlation between twin boundaries and precipitates was observed. These defects decreased once and the precipitations appeared again. The density of precipitates increased through the crystal growth procedure. These precipitates were consisted of Si, C, and N. After the precipitation density increased, the small-angle grain boundaries appeared and some precipitates were observed at the boundaries. We considered the precipitation consisted of light element impurities such as C and N was one of the major origins of the small-angle grain boundary generation.

We investigated the new materials applicable for the field effect passivation layer in crystalline Si solar cells, ZrO2-Al2O3 and ZrO2-Y2O3 binary systems, by using combinatorial synthesis method. As-deposited samples indicated hysteresis curves and flat band-voltage (V-FB) shifts at capacitance-voltage (C-V) measurements. After oxygen gas annealing (OGA) at 700 degrees C for 5min, an improvement of the hysteresis and a positive shift of V-FB were observed. OGA process influenced defects density related to decreasing oxygen vacancy. OGA processed ZrO2 incorporated with 20% Al2O3 and 15% Y2O3 structures showed the maximized negative fixed charge of-5.8 X 10(12) cm(-2) and -7.8 X 10(12) cm(-2) in each system, respectively, suggesting that the ZrO2 based alloy systems were revealed to be the promising material for the passivation in the solar cell application.

The correlation between recombination properties and detailed misorientation angles at small angle grain boundaries SA-GBs in multicrystalline silicon (mc-Si) after metal contamination were evaluated. After metal contamination, EBIC contrast enhancements at > 1.5° SA-GBs were on the order of Fe/1000°C > Ni/1000 °C > Ni/600 °C, while at < 1.5° SA-GBs they were seldom different from any contamination. These results might be attributed to Fe and Ni atoms forming different energy levels in recombination centers and the getting abilities of SA-GBs depending on misorientation angles, i.e., dislocation density at SA-GBs. Many dark spots were observed after Ni/600°C. After Secco etching, we confirmed that the dark spots corresponded to etch pits. Denuded zones at vicinity of SA-GBs were observed after only Fe/1000°C. The gettering ability of SA-GBs depends on dislocation density and the difference in recombination properties after metal contamination was affected by the types of metal impurities. ©The Electrochemical Society.

A scanning capacitance microscopy (SCM) has been applied to the electrical characterization of passivation films for crystalline Si solar cells. An Y 2O3-Al2O3 system, which is a binary composition spread oxide film, was used as a fixed-charge-controlled passivation film. The flat-band voltages of the Y2O3-Al 2O3 system were determined from microscopic C-V curves measured by the SCM. The result was in agreement with that of a conventional C-V method. Additionally, the dV/dC images measured by the SCM were investigated for visualizing the spatial distribution of interface trap density. © 2011 IEEE.

We evaluated the stress distribution in a multi-crystalline silicon substrate. Two substrates grown by casting method were used. Raman spectroscopy showed that stress was concentrated at grain boundaries. In addition, after annealing, the stress concentration at the grain boundaries disappeared. The difference in the structure of grain boundaries before and after the stress disappeared was analyzed by transmission electron microscopy (TEM) observation. The structure of grain boundaries after annealing was simpler than that without annealing. This might be caused by atomic rearrangement during the annealing process. After annealing process, it was also obtained the changes of distribution of impurities. The stress distribution, annealing process, and the existence of impurities were interacted at grain boundaries. ©The Electrochemical Society.

In order to measure strain distribution in multi-crystalline silicon substrates, we have developed a synchrotron radiation white x-ray based Laue pattern mapping (LPM) method. The samples were a single-crystalline and a multi-crystalline silicon substrates. The experiments were carried out at the beamline BL28B2 at the SPring-8 third-generation synchrotron facility. In order to obtain local characteristics, the incident beam size was set to be 0.05mm square. The position of sample can be controlled by stepping motors and the sample was scanned two-dimensionally perpendicular to the direction of x-ray. The transparent Laue pattern was obtained by a x-ray imaging sensor at each measurement point. For comparison, x-ray topography (XRT) images were also measured. The results of LPM agreed with those of XRT images. It is indicated that the LPM is useful to measure strain distribution, especially for multi-crystalline silicon substrates

Sigma 9 grain boundaries (Sigma 9 GBs) in the multicrystalline silicon substrates with and without annealing process were characterized by micro X-ray fluorescence, transmission electron microscopy (TEM) observation, and UV-Raman spectroscopy mapping. The Ni aggregations appeared at some Sigma 9 GBs only after annealing. The differences in the characteristics of GBs with and without annealing were evaluated. Clear structure changes were observed by TEM evaluation for the corresponding Sigma 9 GBs after annealing. At the same Sigma 9 GBs, the stress concentration was observed without an annealing process and disappeared with one. We consider that the Ni aggregation was enhanced by stress accumulation and silicide accelerated the atomic rearrangement at the Sigma 9 GBs. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3423445] All rights reserved.