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Sample records for czochralski silicon crystals

  1. Future application of Czochralski crystal pulling for silicon

    NASA Technical Reports Server (NTRS)

    Matlcok, J. H.

    1985-01-01

    Czochralski (Cz) crystal pulling has been the predominant method used for preparing silicon single crystal for the past twenty years. The fundamental technology used has changed little. However, great strides have been made in learning how to make the crystals bigger and of better quality at ever increasing productivity rates. Currently charge sizes of 50 kg of polycrystal silicon are being used for production and crystals up to ten inches in diameter have been grown without major difficulty. The largest material actually being processed in silicon wafer form is 150 mm (6 inches) in diameter. Growing of crystals in a magnetic field has proved to be particularly useful for microscopic impurity control. Major developments in past years on equipment for Cz crystal pulling have included the automatic growth control of the diameter as well as the starting core of the crystal, the use of magnetic fields and around the crystal puller to supress convection, various recharging schemes for dopant control and the use of continuous liquid feed in the crystal puller. The latter, while far from being a reliable production process, is ideal in concept for major improvement in Cz crystal pulling. The Czochralski process will maintain its dominance of silicon crystal production for many years.

  2. Mutiple Czochralski growth of silicon crystals from a single crucible

    NASA Technical Reports Server (NTRS)

    Lane, R. L.; Kachare, A. H.

    1980-01-01

    An apparatus for the Czochralski growth of silicon crystals is presented which is capable of producing multiple ingots from a single crucible. The growth chamber features a refillable crucible with a water-cooled, vacuum-tight isolation valve located between the pull chamber and the growth furnace tank which allows the melt crucible to always be at vacuum or low argon pressure when retrieving crystal or introducing recharge polysilicon feed stock. The grower can thus be recharged to obtain 100 kg of silicon crystal ingots from one crucible, and may accommodate crucibles up to 35 cm in diameter. Evaluation of the impurity contents and I-V characteristics of solar cells fabricated from seven ingots grown from two crucibles reveals a small but consistent decrease in cell efficiency from 10.4% to 9.6% from the first to the fourth ingot made in a single run, which is explained by impurity build-up in the residual melt. The crystal grower thus may offer economic benefits through the extension of crucible lifetime and the reduction of furnace downtime.

  3. Mutiple Czochralski growth of silicon crystals from a single crucible

    NASA Technical Reports Server (NTRS)

    Lane, R. L.; Kachare, A. H.

    1980-01-01

    An apparatus for the Czochralski growth of silicon crystals is presented which is capable of producing multiple ingots from a single crucible. The growth chamber features a refillable crucible with a water-cooled, vacuum-tight isolation valve located between the pull chamber and the growth furnace tank which allows the melt crucible to always be at vacuum or low argon pressure when retrieving crystal or introducing recharge polysilicon feed stock. The grower can thus be recharged to obtain 100 kg of silicon crystal ingots from one crucible, and may accommodate crucibles up to 35 cm in diameter. Evaluation of the impurity contents and I-V characteristics of solar cells fabricated from seven ingots grown from two crucibles reveals a small but consistent decrease in cell efficiency from 10.4% to 9.6% from the first to the fourth ingot made in a single run, which is explained by impurity build-up in the residual melt. The crystal grower thus may offer economic benefits through the extension of crucible lifetime and the reduction of furnace downtime.

  4. Properties of doped silicon single crystals grown by the Czochralski method and by the method of rigidly attached communicating vessels

    SciTech Connect

    Dashevskii, M.Ya.; Petrov, V.V.; Mikhnenko, V.M.

    1987-08-01

    Phosphorus-doped dislocation-free silicon single crystals, grown by the method of rigidly attached communicating vessels and the Czochralski method have been studied. The phosphorus, optically active oxygen, and microdefects have been found to be more undistributed in MRACV-grown single crystals than in Czochralski-grown single crystals.

  5. Large area Czochralski silicon for solar cells

    NASA Technical Reports Server (NTRS)

    Rea, S. N.; Wakefield, G. F.

    1976-01-01

    A detailed model of a typical Czochralski silicon crystal puller is utilized to predict maximum crystal growth rate as a function of various furnace parameters. Results of this analysis, when combined with multiblade slurry sawing, indicate that the Czochralski process is highly attractive for achieving near-term cost reduction of solar cell silicon.

  6. Large area Czochralski silicon for solar cells

    NASA Technical Reports Server (NTRS)

    Rea, S. N.; Wakefield, G. F.

    1976-01-01

    A detailed model of a typical Czochralski silicon crystal puller is utilized to predict maximum crystal growth rate as a function of various furnace parameters. Results of this analysis, when combined with multiblade slurry sawing, indicate that the Czochralski process is highly attractive for achieving near-term cost reduction of solar cell silicon.

  7. Maximum length of large diameter Czochralski silicon single crystals at fracture stress limit of seed

    NASA Astrophysics Data System (ADS)

    Kim, K. M.; Smetana, P.

    1990-03-01

    Growth of large diameter Czochralski (CZ) silicon crystals require complete elimination of dislocations by means of Dash technique, where the seed diameter is reduced to a small size typically 3 mm in conjunction with increase in the pull rate. The maximum length of the large CZ silicon is estimated at the fracture stress limit of the seed neck diameter ( d). The maximum lengths for 200 and 300 mm CZ crystals amount to 197 and 87 cm, respectively, with d = 0.3 cm; the estimated maximum weight is 144 kg.

  8. Large area Czochralski silicon

    NASA Technical Reports Server (NTRS)

    Rea, S. N.; Gleim, P. S.

    1977-01-01

    The overall cost effectiveness of the Czochralski process for producing large-area silicon was determined. The feasibility of growing several 12 cm diameter crystals sequentially at 12 cm/h during a furnace run and the subsequent slicing of the ingot using a multiblade slurry saw were investigated. The goal of the wafering process was a slice thickness of 0.25 mm with minimal kerf. A slice + kerf of 0.56 mm was achieved on 12 cm crystal using both 400 grit B4C and SiC abrasive slurries. Crystal growth experiments were performed at 12 cm diameter in a commercially available puller with both 10 and 12 kg melts. Several modifications to the puller hoz zone were required to achieve stable crystal growth over the entire crystal length and to prevent crystallinity loss a few centimeters down the crystal. The maximum practical growth rate for 12 cm crystal in this puller design was 10 cm/h, with 12 to 14 cm/h being the absolute maximum range at which melt freeze occurred.

  9. Numerical simulation of thermal history for Czochralski growth of silicon single crystals

    SciTech Connect

    Fujioka, Kazumasa . Mechanical Engineering Research Lab.); Nakayama, Wataru . Dept. of Mechanical Engineering of Production); Sugino, Yuji . Kofu Works)

    1994-03-01

    A numerical analysis was conducted to study the thermal history of Czochralski growth of large silicon single crystals. The computations were performed for various crystal diameters and emissivities of the crucible inner wall. The analysis predicts the change of temperature distributions in the crystal and the shape of the solid-melt interface. The computed results show the importance of the effects of radiation from the crucible inner wall and the melt-free surface on crystal growth. Also, increasing the crystal diameter decreases the pull speed and increases the concavity of the solid-melt interface into the crystal. The result of this analysis is in good agreement with measurement of the pull rate on production apparatus, and the shape of the crystal-melt interface showed a tendency to agree qualitatively with the observations of X-ray diffraction.

  10. Crystal-originated particles in germanium-doped Czochralski silicon crystal

    NASA Astrophysics Data System (ADS)

    Chen, Jiahe; Yang, Deren; Li, Hong; Ma, Xiangyang; Tian, Daxi; Li, Liben; Que, Duainlin

    2007-08-01

    Grown-in distribution and annealing behavior of crystal-originated particles (COPs) in Czochralski silicon (Cz-Si) wafer with germanium doping have been investigated. It was found that COPs with high density but small sizes were inclined to generate in germanium-doped Cz-Si (GCz-Si) wafer. The increase of boron atoms in Cz-Si crystal with the germanium doping could benefit the formation of COPs while the oxygen interstitials in GCz-Si wafer could enhance the generation of COPs with small sizes. Meanwhile, it was suggested that the germanium doping in Cz-Si would result in the poor thermal stability of COPs. It is proposed that the combination between germanium atom and vacancy could reduce the free vacancy concentration and the onset temperature for void generation, thus forming denser but smaller void. While the stress compensation induced by boron and germanium atoms could increase the vacancy fluxes in heavy-boron doped GCz-Si crystal, the presence of oxygen atom in GCz-Si would incline to benefit the formation of inner oxide walls of void, especially with small sizes. Furthermore, thinner oxide walls within void for GCz-Si crystal are considered to be charged for the easy annihilation by the germanium doping.

  11. The effect of growth rate, diameter and impurity concentration on structure in Czochralski silicon crystal growth

    NASA Technical Reports Server (NTRS)

    Digges, T. G., Jr.; Shima, R.

    1980-01-01

    It is demonstrated that maximum growth rates of up to 80% of the theoretical limit can be attained in Czochralski-grown silicon crystals while maintaining single crystal structure. Attaining the other 20% increase is dependent on design changes in the grower, to reduce the temperature gradient in the liquid while increasing the gradient in the solid. The conclusions of Hopkins et al. (1977) on the effect of diameter on the breakdown of structure at fast growth rates are substantiated. Copper was utilized as the test impurity. At large diameters (greater than 7.5 cm), concentrations of greater than 1 ppm copper were attained in the solid (45,000 ppm in the liquid) without breakdown at maximum growth speeds. For smaller diameter crystals, the sensitivity of impurities is much more apparent. For solar cell applications, impurities will limit cell performance before they cause crystal breakdown for fast growth rates of large diameter crystals.

  12. The effect of growth rate, diameter and impurity concentration on structure in Czochralski silicon crystal growth

    NASA Technical Reports Server (NTRS)

    Digges, T. G., Jr.; Shima, R.

    1980-01-01

    It is demonstrated that maximum growth rates of up to 80% of the theoretical limit can be attained in Czochralski-grown silicon crystals while maintaining single crystal structure. Attaining the other 20% increase is dependent on design changes in the grower, to reduce the temperature gradient in the liquid while increasing the gradient in the solid. The conclusions of Hopkins et al. (1977) on the effect of diameter on the breakdown of structure at fast growth rates are substantiated. Copper was utilized as the test impurity. At large diameters (greater than 7.5 cm), concentrations of greater than 1 ppm copper were attained in the solid (45,000 ppm in the liquid) without breakdown at maximum growth speeds. For smaller diameter crystals, the sensitivity of impurities is much more apparent. For solar cell applications, impurities will limit cell performance before they cause crystal breakdown for fast growth rates of large diameter crystals.

  13. Enhancement of heat transfer in Czochralski growth of silicon crystals with a chemical cooling technique

    NASA Astrophysics Data System (ADS)

    Ding, Junling; Liu, Lijun; Zhao, Wenhan

    2017-06-01

    The cost of producing single-crystalline silicon with the Czochralski method can be reduced by promoting the crystal size and/or crystal pulling rate. However, more latent heat of solidification needs to be released from the melt-crystal (m-c) interface during the crystal growth process. In this study, the C-CO2 chemical endothermic reaction is proposed as a novel and efficient cooling technique to solve this problem. Compared with the conventional gas cooling method, C-CO2 endothermic reaction method can significantly enhance the heat transfer in the crystal at the m-c interface. It was found that the heat transfer is more enhanced with a chemical reaction of smaller activation energy, and the m-c interface becomes flatter. The influence of the carbon concentration in the chemical reactive gas flow on the heat removal in the crystal at the m-c interface is also investigated. The cooling effect is significantly increased with the increase in the carbon concentration when it is small. However, when the carbon concentration in the reactive gas is high, the cooling effect just increases slightly. The research demonstrates that the proposed chemical endothermic reaction is a promising cooling technique to be applied in CZ-Si crystal growth with large size/high pulling rate.

  14. Reduction of carbon contamination during the melting process of Czochralski silicon crystal growth

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Gao, Bing; Nakano, Satoshi; Kakimoto, Koichi

    2017-09-01

    Generation, incorporation, and accumulation of carbon (C) were investigated by transient global simulations of heat and mass transport during the melting process of Czochralski silicon (CZ-Si) crystal growth. Contact reaction between the quartz crucible and graphite susceptor was introduced as an extra origin of C contamination. The contribution of the contact reaction on C accumulation is affected by the back diffusion of C monoxide (CO) from the gap between the gas-guide and the crucible. The effect of the gas-guide coating on C reduction was elucidated by taking the reaction between the silicon carbide (SiC) coating and gaseous Si monoxide (SiO) into account. Application of the SiC coating on the gas-guide could effectively reduce the C contamination because of its higher thermochemical stability relative to that of graphite. Gas flow control on the back diffusion of the generated CO was examined by the parametric study of argon gas flow rate. Generation and back diffusion of CO were both effectively suppressed by the increase in the gas flow rate because of the high Péclet number of species transport. Strategies for C content reduction were discussed by analyzing the mechanisms of C accumulation process. According to the elucidated mechanisms of C accumulation, the final C content depends on the growth duration and contamination flux at the gas/melt interface.

  15. Oxygen-induced recombination centers in as-grown Czochralski silicon crystals

    NASA Technical Reports Server (NTRS)

    Nauka, K.; Gatos, H. C.; Lagowski, J.

    1983-01-01

    Simultaneous quantitative microprofiles of the interstitial oxygen concentration and of the excess carrier lifetime are obtained in Czochralski-grown Si crystals employing double laser absorption scanning. It is found that oxygen concentration maxima and minima along the crystal growth direction coincide with lifetime minima and maxima, respectively. Another finding is that the magnitude of oxygen-induced lifetime changes increases dramatically in going from the center to the periphery of the crystal. The findings discussed imply that 'as-grown' oxygen precipitates figure in lifetime-limiting processes.

  16. Oxygen-induced recombination centers in as-grown Czochralski silicon crystals

    NASA Technical Reports Server (NTRS)

    Nauka, K.; Gatos, H. C.; Lagowski, J.

    1983-01-01

    Simultaneous quantitative microprofiles of the interstitial oxygen concentration and of the excess carrier lifetime are obtained in Czochralski-grown Si crystals employing double laser absorption scanning. It is found that oxygen concentration maxima and minima along the crystal growth direction coincide with lifetime minima and maxima, respectively. Another finding is that the magnitude of oxygen-induced lifetime changes increases dramatically in going from the center to the periphery of the crystal. The findings discussed imply that 'as-grown' oxygen precipitates figure in lifetime-limiting processes.

  17. Effect of the packing structure of silicon chunks on the melting process and carbon reduction in Czochralski silicon crystal growth

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Nakano, Satoshi; Kakimoto, Koichi

    2017-06-01

    Carbon (C) contamination in Czochralski silicon (CZ-Si) crystal growth mainly originates from carbon monoxide (CO) generation on the graphite components, which reaches a maximum during the melting stage. Loading a crucible with poly-Si feedstock includes many technical details for optimization of the melting and growth processes. To investigate the effect of the packing structure of Si chunks on C accumulation in CZ-Si crystal growth, transient global simulations of heat and mass transport were performed for the melting process with different packing structures of poly-Si. The heat transport modeling took into account the effective thermal conductivity (ETC) of the Si feedstock, which is affected by the packing structure. The effect of the chunk size on the melting process and C accumulation were investigated by parametric studies of different packing structures. The heat transport and melting process in the crucible were affected by the ETC and the emissivity of the Si feedstock. It was found that smaller Si chunks packed in the upper part could speed up the melting process and smooth the power profile. Decreasing the duration of the melting process is favorable for reduction of C contamination in the Si feedstock. Parametric studies indicated that optimization of the melting process by the packing structure is possible and essential for C reduction in CZ-Si crystal growth.

  18. Control of heat transfer in continuous-feeding Czochralski-silicon crystal growth with a water-cooled jacket

    NASA Astrophysics Data System (ADS)

    Zhao, Wenhan; Liu, Lijun

    2017-01-01

    The continuous-feeding Czochralski method is an effective method to reduce the cost of single crystal silicon. By promoting the crystal growth rate, the cost can be reduced further. However, more latent heat will be released at the melt-crystal interface under a high crystal growth rate. In this study, a water-cooled jacket was applied to enhance the heat transfer at the melt-crystal interface. Quasi-steady-state numerical calculation was employed to investigate the impact of the water-cooled jacket on the heat transfer at the melt-crystal interface. Latent heat released during the crystal growth process at the melt-crystal interface and absorbed during feedstock melting at the feeding zone was modeled in the simulations. The results show that, by using the water-cooled jacket, heat transfer in the growing crystal is enhanced significantly. Melt-crystal interface deflection and thermal stress increase simultaneously due to the increase of radial temperature at the melt-crystal interface. With a modified heat shield design, heat transfer at the melt-crystal interface is well controlled. The crystal growth rate can be increased by 20%.

  19. Silicon solar cells from transition metal doped Czochralski and web crystals

    NASA Technical Reports Server (NTRS)

    Davis, J. R.; Rai-Choudhury, P.; Blais, P. D.; Hopkins, R. H.; Mccormick, J. R.

    1976-01-01

    The influence of metallic impurities on solar cell characteristics has been examined to establish the cost sensitive purity versus performance trade-offs. Solar cells were fabricated on 2 to 4 ohm-cm p-type substrates obtained by Czochralski and dendritic web growth processes. Controlled amounts of metallic impurities were introduced into the melt during growth and included Fe, Cr, Mn, Ni, Cu, Ti, V, Zr, Mg, Zn, and Al. Impurity concentrations in the crystals were determined using emission and mass spectrographic techniques and in some cases by neutron activation analysis. The solar cells were characterized by means of a computer program to curve-fit measured voltage-current data. The principal effect of the added impurities is a degradation of lifetime and diffusion length.

  20. Silicon solar cells from transition metal doped Czochralski and web crystals

    NASA Technical Reports Server (NTRS)

    Davis, J. R.; Rai-Choudhury, P.; Blais, P. D.; Hopkins, R. H.; Mccormick, J. R.

    1976-01-01

    The influence of metallic impurities on solar cell characteristics has been examined to establish the cost sensitive purity versus performance trade-offs. Solar cells were fabricated on 2 to 4 ohm-cm p-type substrates obtained by Czochralski and dendritic web growth processes. Controlled amounts of metallic impurities were introduced into the melt during growth and included Fe, Cr, Mn, Ni, Cu, Ti, V, Zr, Mg, Zn, and Al. Impurity concentrations in the crystals were determined using emission and mass spectrographic techniques and in some cases by neutron activation analysis. The solar cells were characterized by means of a computer program to curve-fit measured voltage-current data. The principal effect of the added impurities is a degradation of lifetime and diffusion length.

  1. Czochralski crystal growth: Modeling study

    NASA Technical Reports Server (NTRS)

    Dudukovic, M. P.; Ramachandran, P. A.; Srivastava, R. K.; Dorsey, D.

    1986-01-01

    The modeling study of Czochralski (Cz) crystal growth is reported. The approach was to relate in a quantitative manner, using models based on first priniciples, crystal quality to operating conditions and geometric variables. The finite element method is used for all calculations.

  2. Analysis of the effect of symmetric/asymmetric CUSP magnetic fields on melt/crystal interface during Czochralski silicon growth

    NASA Astrophysics Data System (ADS)

    Daggolu, Parthiv; Ryu, Jae Woo; Galyukov, Alex; Kondratyev, Alexey

    2016-10-01

    With the use of 300 mm silicon wafers for industrial semiconductor device manufacturing, the Czochralski (Cz) crystal growth process has to be optimized to achieve higher quality and productivity. Numerical studies based on 2D global thermal models combined with 3D simulation of melt convection are widely used today to save time and money in the process development. Melt convection in large scale Cz Si growth is controlled by a CUSP or transversal magnetic field (MF) to suppress the melt turbulence. MF can be optimized to meet necessary characteristics of the growing crystal, in terms of point defects, as MF affects the melt/crystal interface geometry and allows adjustment of the pulling rate. Among the different knobs associated with the CUSP magnetic field, the nature of its configuration, going from symmetric to asymmetric, is also reported to be an important tool for the control of crystallization front. Using a 3D unsteady model of the CGSim software, we have studied these effects and compared with several experimental results. In addition, physical mechanisms behind these observations are explored through a detailed modeling analysis of the effect of an asymmetric CUSP MF on convection features governing the heat transport in the silicon melt.

  3. Phase field modelling on the growth dynamics of double voids of different sizes during czochralski silicon crystal growth

    NASA Astrophysics Data System (ADS)

    Guan, X. J.; Wang, J.

    2017-02-01

    To investigate their dynamics and interaction mechanisms, the growth process of the two voids with different sizes during Czochralski silicon crystal growth were simulated by use of an established phase field model and its corresponding program code. On the basis of the several phase field numerical simulation cases, the evolution laws of the double voids were acquired as follows: the phase field model is capable to simulate the growth process of double voids with different sizes; there are two modes of their growth, that is, either mutual integration or competitive growth; the exact moment of their fusion can be also captured, and it is τ of 7.078 (simulation time step of 14156) for the initial vacancy concentration of 0.02 and the initial space between two void centers of 44Δx.

  4. LSA Large Area Silicon Sheet Task Continuous Czochralski Process Development

    NASA Technical Reports Server (NTRS)

    Rea, S. N.

    1979-01-01

    A commercial Czochralski crystal growing furnace was converted to a continuous growth facility by installation of a small, in-situ premelter with attendant silicon storage and transport mechanisms. Using a vertical, cylindrical graphite heater containing a small fused quartz test tube linear from which the molten silicon flowed out the bottom, approximately 83 cm of nominal 5 cm diamter crystal was grown with continuous melt addition furnished by the test tube premelter. High perfection crystal was not obtained, however, due primarily to particulate contamination of the melt. A major contributor to the particulate problem was severe silicon oxide buildup on the premelter which would ultimately drop into the primary melt. Elimination of this oxide buildup will require extensive study and experimentation and the ultimate success of continuous Czochralski depends on a successful solution to this problem. Economically, the continuous Czochralski meets near-term cost goals for silicon sheet material.

  5. Growing Organic Crystals By The Czochralski Method

    NASA Technical Reports Server (NTRS)

    Shields, Angela; Frazier, Donald O.; Penn, Benjamin G.; Aggarwal, M. D.; Wang, W. S.

    1994-01-01

    Apparatus grows high-quality single crystals of organic compounds by Czochralski method. In Czochralski process, growing crystal lifted from middle of molten material without touching walls. Because of low melting temperatures of organic crystals, glass vessels usable. Traditional method for inorganic semiconductors adapted to optically nonlinear organic materials.

  6. Growing Organic Crystals By The Czochralski Method

    NASA Technical Reports Server (NTRS)

    Shields, Angela; Frazier, Donald O.; Penn, Benjamin G.; Aggarwal, M. D.; Wang, W. S.

    1994-01-01

    Apparatus grows high-quality single crystals of organic compounds by Czochralski method. In Czochralski process, growing crystal lifted from middle of molten material without touching walls. Because of low melting temperatures of organic crystals, glass vessels usable. Traditional method for inorganic semiconductors adapted to optically nonlinear organic materials.

  7. LSSA large area silicon sheet task continuous Czochralski process development

    NASA Technical Reports Server (NTRS)

    Rea, S. N.

    1978-01-01

    A Czochralski crystal growing furnace was converted to a continuous growth facility by installation of a premelter to provide molten silicon flow into the primary crucible. The basic furnace is operational and several trial crystals were grown in the batch mode. Numerous premelter configurations were tested both in laboratory-scale equipment as well as in the actual furnace. The best arrangement tested to date is a vertical, cylindrical graphite heater containing small fused silicon test tube liner in which the incoming silicon is melted and flows into the primary crucible. Economic modeling of the continuous Czochralski process indicates that for 10 cm diameter crystal, 100 kg furnace runs of four or five crystals each are near-optimal. Costs tend to asymptote at the 100 kg level so little additional cost improvement occurs at larger runs. For these conditions, crystal cost in equivalent wafer area of around $20/sq m exclusive of polysilicon and slicing was obtained.

  8. Three-dimensional evaluation of gettering ability for oxygen atoms at small-angle tilt boundaries in Czochralski-grown silicon crystals

    SciTech Connect

    Ohno, Yutaka Inoue, Kaihei; Fujiwara, Kozo; Deura, Momoko; Kutsukake, Kentaro; Yonenaga, Ichiro; Shimizu, Yasuo; Inoue, Koji; Ebisawa, Naoki; Nagai, Yasuyoshi

    2015-06-22

    Three-dimensional distribution of oxygen atoms at small-angle tilt boundaries (SATBs) in Czochralski-grown p-type silicon ingots was investigated by atom probe tomography combined with transmission electron microscopy. Oxygen gettering along edge dislocations composing SATBs, post crystal growth, was observed. The gettering ability of SATBs would depend both on the dislocation strain and on the dislocation density. Oxygen atoms would agglomerate in the atomic sites under the tensile hydrostatic stress larger than about 2.0 GPa induced by the dislocations. It was suggested that the density of the atomic sites, depending on the tilt angle of SATBs, determined the gettering ability of SATBs.

  9. Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth. II - Processing strategies

    NASA Technical Reports Server (NTRS)

    Derby, J. J.; Brown, R. A.

    1986-01-01

    The pseudosteady-state heat transfer model developed in a previous paper is augmented with constraints for constant crystal radius and melt/solid interface deflection. Combinations of growth rate, and crucible and bottom-heater temperatures are tested as processing parameters for satisfying the constrained thermal-capillary problem over a range of melt volumes corresponding to the sequence occuring during the batchwise Czochralski growth of a small-diameter silicon crystal. The applicability of each processing strategy is judged by the range of existence of the solution, in terms of melt volume and the values of the axial and radial temperature gradients in the crystal.

  10. Numerical simulation of the oxygen concentration distribution in silicon melt for different crystal lengths during Czochralski growth with a transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Chen, Jyh-Chen; Chiang, Pei-Yi; Nguyen, Thi Hoai Thu; Hu, Chieh; Chen, Chun-Hung; Liu, Chien-Cheng

    2016-10-01

    A three-dimensional simulation model is used to study the oxygen concentration distribution in silicon crystal during the Czochralski growth process under a transverse uniform magnetic field. The flow, temperature, and oxygen concentration distributions inside the furnace are calculated for different crystal lengths. There is significant variation in the flow structure in the melt with the growth length. The results show that in the initial stages, there is a decrease in the oxygen concentration at the crystal-melt interface as the length of the growing crystal increases. As the crystal lengthens further, a minimum value is reached after which the oxygen concentration increases continuously. This trend is consistent with that shown in the experimental results. The variation of the oxygen concentration with the growth length is strongly related to the depth of the melt in the crucible and the flow structure inside the melt. Better uniformity of the axial oxygen concentration can be achieved by proper adjustment of the crucible rotation rate during the growth process.

  11. Effective segregation coefficient of boron in silicon ingots grown by the Czochralski and Bridgman techniques

    SciTech Connect

    Ravishankar, P.S.; Francis, R.W.; Hunt, L.P.

    1983-05-01

    Hall measurements and four-point-probe resistivity measurements are used to determine the concentration profile of boron in doped semiconductor silicon ingots grown by Czochralski and Bridgman techniques. The concentration profiles are fitted to the normal segregation equation and the effective segregation coefficient, k /SUB eff/, is calculated. The average value of k /SUB eff/ for boron is 0.786 in Czochralski single crystals and 0.803 in Bridgman polycrystals.

  12. Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth

    NASA Technical Reports Server (NTRS)

    Derby, J. J.; Brown, R. A.

    1986-01-01

    Results are presented from finite element analysis of the Czochralski (CZ) and Liquid Encapsulated Czochralski (LEC) crystal growth processes based on a thermal-capillary model which governs the heat transfer in the system simultaneously with setting the shapes of the melt/solid interface, the melt and encapsulant menisci, and the radius of a steadily growing crystal. Calculations are performed for the small-scale growth of silicon (CZ) and gallium arsenide (LEC). The effects of melt volume and crucible position relative to the heater on the radius of the crystal and the shape of the melt/solid interface are predicted for the CZ system, and the importance of including an accurate representation of the melt meniscus for modeling the process is demonstrated. The additional effect of an encapsulant layer on heat transfer is treated for the LEC method for the cases of totally transparent and opaque encapsulant. The responses of these LEC prototype systems are examined for changes in pull rate and encapsulant volume.

  13. Czochralski crystal growth for laser cooling

    NASA Astrophysics Data System (ADS)

    Cittadino, Giovanni; Volpi, Azzurra; Di Lieto, Alberto; Tonelli, Mauro

    2017-01-01

    In laser cooling of crystals in solid-state physics, it is really important to obtain crystals with a large size at a relatively fast growth rate and high-optical quality that is defect-free. To get that, one of the methods to grow crystals is the Czochralski technique. The Czochralski technique will be presented and, in particular, the furnaces in New Materials for Laser Applications Laboratories of Pisa for this application will be discussed. Afterward the parameters for the growth of crystal fluorides are depicted and it is shown how these parameters lead to build samples suitable for optical cooling. All processes that are necessary to avoid contamination inside crystals like OH- ion and how to avoid reduction of Yb to Yb will be given. Spectroscopy of all samples will be treated in order to obtain the cooling parameters λf and αb for each sample. Afterward, an efficiency model will be discussed and the data efficiency of cooling obtained by a sample's own crystals will be shown.

  14. Effective distribution coefficient of silicon dopants during magnetic Czochralski growth

    NASA Astrophysics Data System (ADS)

    Series, R. W.; Hurle, D. T. J.; Barraclough, K. G.

    1985-09-01

    Silicon crystals have been grown under axial magnetic fields of up to 0.2 T. At 0.05 T the field starts to interact with the melt and dopant incorporation becomes erratic. As the field is increased to 0.2 T the interaction becomes more controlled and it is seen that the effective distribution coefficient (keff) moves towards unity. A theory based on the analysis by Burton, Prim and Slichter of the dependence of the effective distribution coefficient (keff) on growth and crystal rotation rates in Czochralski growth is extended to include the effect of an imposed steady axial magnetic field. The flow fields incorporated into the theory are based on the analysis of the hydromagnetic flow at a rotating disc due to Kakutani (1962). It is shown that keff approaches unity as the field increases.

  15. Behavior of volatile dopants (P, Sb) in Czochralski silicon growth

    NASA Astrophysics Data System (ADS)

    Porrini, M.; Scala, R.; Voronkov, V. V.

    2017-02-01

    The evaporation from the silicon melt, during Czochralski process, is an important effect for Phosphorus and Antimony dopants. The evaporation rate γ was deduced from the measured axial profile of the resistivity converted into the concentration. For the heavily doped crystals, the value of γ is very similar for both P and Sb: in the order of 5.5×10-5 cm/s (which is significantly lower than the previously reported evaporation rates). It was concluded that the rate-limiting step for the evaporation process is neither the evaporation reaction itself nor the impurity transport through the flowing gas, but rather the transport through the melt that strongly depends on the melt convection. For low Phosphorus concentration, the transport through the gas is severely slowed-down - due to a change in the dominant gaseous species, from P2 to P1 - and becomes a limiting step. The evaporation rate is decreased and, in fact, becomes negligible.

  16. A multiple p-n junction structure obtained from as-grown Czochralski silicon crystals by heat treatment - Application to solar cells

    NASA Technical Reports Server (NTRS)

    Chi, J. Y.; Gatos, H. C.; Mao, B. Y.

    1980-01-01

    Multiple p-n junctions have been prepared in as-grown Czochralski p-type silicon through overcompensation near the oxygen periodic concentration maxima by oxygen thermal donors generated during heat treatment at 450 C. Application of the multiple p-n-junction configuration to photovoltaic energy conversion has been investigated. A new solar-cell structure based on multiple p-n-junctions was developed. Theoretical analysis showed that a significant increase in collection efficiency over the conventional solar cells can be achieved.

  17. A multiple p-n junction structure obtained from as-grown Czochralski silicon crystals by heat treatment - Application to solar cells

    NASA Technical Reports Server (NTRS)

    Chi, J. Y.; Gatos, H. C.; Mao, B. Y.

    1980-01-01

    Multiple p-n junctions have been prepared in as-grown Czochralski p-type silicon through overcompensation near the oxygen periodic concentration maxima by oxygen thermal donors generated during heat treatment at 450 C. Application of the multiple p-n-junction configuration to photovoltaic energy conversion has been investigated. A new solar-cell structure based on multiple p-n-junctions was developed. Theoretical analysis showed that a significant increase in collection efficiency over the conventional solar cells can be achieved.

  18. Potential productivity benefits of float-zone versus Czochralski crystal growth

    NASA Technical Reports Server (NTRS)

    Abe, T.

    1985-01-01

    Efficient mass production of single-crystal silicon is necessary for the efficient silicon solar arrays needed in the coming decade. However, it is anticipated that there will be difficulty growing such volumes of crystals using conventional Czochralski (Cz) methods. While the productivity of single crystals might increase with a crystal diameter increase, there are two obstacles to the mass production of large diameter Czochralski crystals, the long production cycle due to slow growth rate and the high heat requirements of the furnaces. Also counterproductive would be the large resistivity gradient along the growth direction of the crystals due to impurity concentration. Comparison between Float zone (FZ) and Cz crystal growth on the basis of a crystal 150 mm in diameter is on an order of two to four times in favor of the FZ method. This advantage results from high growth rates and steady-state growth while maintaining a dislocation-free condition and impurity segregation.

  19. LSA Large Area Silicon Sheet Task. Continuous Liquid Feed Czochralski Growth. [for solar cell fabrication

    NASA Technical Reports Server (NTRS)

    Fiegl, G.

    1979-01-01

    The design and development of equipment and processes to demonstrate continuous growth of crystals by the Czochralski method suitable for producing single silicon crystals for use in solar cells is presented. The growth of at least 150 kg of mono silicon crystal, 150 mm in diameter is continuous from one growth container. A furnace with continuous liquid replenishment of the growth crucible, accomplished by a meltdown system with a continuous solid silicon feed mechanism and a liquid transfer system, with associated automatic feedback controls is discussed. Due to the silicon monoxide build up in the furnace and its retarding effect on crystal growth the furnace conversion for operation in the low pressure range is described. Development of systems for continuous solid recharging of the meltdown chamber for various forms of poly silicon is described.

  20. Evaluation of nucleic acid duplex formation on gold over layers in biosensor fabricated using Czochralski-grown single-crystal silicon substrate.

    PubMed

    Gopinath, Subash C B; Kumaresan, Ramanujam; Awazu, Koichi; Fujimaki, Makoto; Mizuhata, Minoru; Tominaga, Junji; Kumar, Penmetcha K R

    2010-09-01

    With a view to developing an economical and elegant biosensor chip, we compared the efficiencies of biosensors that use gold-coated single-crystal silicon and amorphous glass substrates. The reflectivity of light over a wide range of wavelengths was higher from gold layer coated single-crystal silicon substrates than from glass substrates. Furthermore, the efficiency of reflection from gold layers of two different thicknesses was examined. The thicker gold layer (100 nm) on the single-crystal silicon showed a higher reflectivity than the thinner gold film (10 nm). The formation of a nucleic acid duplex and aptamer-ligand interactions were evaluated on these gold layers, and a crystalline silicon substrate coated with the 100-nm-thick gold layer is proposed as an alternative substrate for studies of interactions of biomolecules.

  1. Simulation of jet cooling effects on Czochralski crystal growth

    NASA Technical Reports Server (NTRS)

    Srivastava, R. K.; Ramachandran, P. A.; Dudukovic, M. P.

    1986-01-01

    The effects of cooling the crystal side surface by blowing a jet of an inert gas are examined in detail for Czochralski crystal growth. A combined model of the crystal + melt, which incorporates the detailed radiation calculations, the shape of the melt-gas meniscus, predicts the growth rate and the crystal-melt interface shape, is used for this study. The convective heat transfer coefficient for the jet is estimated from the correlation available in the literature. The effect of the jet cooling on the interface shape and the pulling rate is significant. The crystal diameter as well as the interface shape tend to be more stable in the environment of the rapid cooling of the crystal by the jet. The crystal diameter or the interface shape can be easily controlled by adjusting the gas flow rate through the jet. This gives the Czochralski pulling an additional degree of freedom facilitating the control of crystal diameter and interface shape.

  2. Simulation of jet cooling effects on Czochralski crystal growth

    NASA Technical Reports Server (NTRS)

    Srivastava, R. K.; Ramachandran, P. A.; Dudukovic, M. P.

    1986-01-01

    The effects of cooling the crystal side surface by blowing a jet of an inert gas are examined in detail for Czochralski crystal growth. A combined model of the crystal + melt, which incorporates the detailed radiation calculations, the shape of the melt-gas meniscus, predicts the growth rate and the crystal-melt interface shape, is used for this study. The convective heat transfer coefficient for the jet is estimated from the correlation available in the literature. The effect of the jet cooling on the interface shape and the pulling rate is significant. The crystal diameter as well as the interface shape tend to be more stable in the environment of the rapid cooling of the crystal by the jet. The crystal diameter or the interface shape can be easily controlled by adjusting the gas flow rate through the jet. This gives the Czochralski pulling an additional degree of freedom facilitating the control of crystal diameter and interface shape.

  3. New electron trap in p-type Czochralski silicon

    NASA Technical Reports Server (NTRS)

    Mao, B.-Y.; Lagowski, J.; Gatos, H. C.

    1984-01-01

    A new electron trap (acceptor level) was discovered in p-type Czochralski (CZ) silicon by current transient spectroscopy. The behavior of this trap was found to be similar to that of the oxygen thermal donors; thus, 450 C annealing increases the trap concentration while high-temperature annealing (1100-1200 C) leads to the virtual elimination of the trap. The new trap is not observed in either float-zone or n-type CZ silicon. Its energy level depends on the group III doping element in the sample. These findings suggest that the trap is related to oxygen, and probably to the acceptor impurity as well.

  4. New electron trap in p-type Czochralski silicon

    NASA Technical Reports Server (NTRS)

    Mao, B.-Y.; Lagowski, J.; Gatos, H. C.

    1984-01-01

    A new electron trap (acceptor level) was discovered in p-type Czochralski (CZ) silicon by current transient spectroscopy. The behavior of this trap was found to be similar to that of the oxygen thermal donors; thus, 450 C annealing increases the trap concentration while high-temperature annealing (1100-1200 C) leads to the virtual elimination of the trap. The new trap is not observed in either float-zone or n-type CZ silicon. Its energy level depends on the group III doping element in the sample. These findings suggest that the trap is related to oxygen, and probably to the acceptor impurity as well.

  5. Silicon crystal growth in vacuum

    NASA Technical Reports Server (NTRS)

    Khattak, C. P.; Schmid, F.

    1982-01-01

    The most developed process for silicon crystal growth is the Czochralski (CZ) method which was in production for over two decades. In an effort to reduce cost of single crystal silicon for photovoltaic applications, a directional solidification technique, Heat Exchanger Method (HEM), was adapted. Materials used in HEM and CZ furnaces are quite similar (heaters, crucibles, insulation, etc.). To eliminate the cost of high purity argon, it was intended to use vacuum operation in HEM. Two of the major problems encountered in vacuum processing of silicon are crucible decomposition and silicon carbide formation in the melt.

  6. Shallow melt apparatus for semicontinuous czochralski crystal growth

    DOEpatents

    Wang, Tihu; Ciszek, Theodore F.

    2006-01-10

    In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt crucible (20) to eliminate the necessity supplying a large quantity of feed stock materials that had to be preloaded in a deep crucible to grow a large ingot, comprising a gas tight container a crucible with a deepened periphery (25) to prevent snapping of a shallow melt and reduce turbulent melt convection; source supply means for adding source material to the semiconductor melt; a double barrier (23) to minimize heat transfer between the deepened periphery (25) and the shallow melt in the growth compartment; offset holes (24) in the double barrier (23) to increase melt travel length between the deepened periphery (25) and the shallow growth compartment; and the interface heater/heat sink (22) to control the interface shape and crystal growth rate.

  7. Thermal donor formation in electron-irradiated Czochralski silicon

    SciTech Connect

    Svensson, J.; Svensson, B.G.; Lindstroem, J.L.

    1986-11-24

    Isothermal heat treatment of Czochralski silicon samples has been performed at 450 /sup 0/C. Prior to this treatment some samples were irradiated by high-energy electrons (2.0 MeV) and subsequently annealed at 311 /sup 0/C. As a result, a high concentration of vacancy-dioxygen pairs was obtained. By a comparison of the thermal donor formation kinetics observed in the pretreated samples with that in as-grown samples, the vacancy-dioxygen pair can be ruled out as a ''core'' for thermal donors. A vacancy-trioxygen pair, which occurs as a result of the annealing of the vacancy-dioxygen pair, is also discussed.

  8. Crystal Growth of Mixed Optical Materials With the Automatic Czochralski Puller

    NASA Technical Reports Server (NTRS)

    Loutts, George B.

    1998-01-01

    Most of optical and semiconductor single crystalline materials produced in the electronic industry is grown with the Czochralski technique. This is the only technique capable of producing large high quality single crystals in a reasonable amount of time. The technique originated, and took its name, from pioneering work by Polish engineer J. Czochralski in 1917, who pulled single crystal wires (fibers) of low melting point metals from the melt in order to determine the maximum speeds at which they could be crystallized. The technique has been modified and its application has been extended first to the growth of silicon and later to a very wide range of compound semiconductors, metals, oxides and halides. It is now the dominant technique for the wide range of materials in the electronic industries. Czochralski growth is initiated by dipping a seed crystal of a chosen crystallographic orientation onto the surface of a melt contained in the heated crucible. The seed is then slowly withdrawn, solidifying the adherent column of the melt in steady state at an average rate given by the sum of the pulling rate and the rate of lowering the solid-liquid interface due to the depletion of the melt in the crucible. The control of the desired crystal diameter is achieved by closely controlling the heat balance at the solid-liquid interface.

  9. Crystal Growth of Mixed Optical Materials With the Automatic Czochralski Puller

    NASA Technical Reports Server (NTRS)

    Loutts, George B.

    1998-01-01

    Most of optical and semiconductor single crystalline materials produced in the electronic industry is grown with the Czochralski technique. This is the only technique capable of producing large high quality single crystals in a reasonable amount of time. The technique originated, and took its name, from pioneering work by Polish engineer J. Czochralski in 1917, who pulled single crystal wires (fibers) of low melting point metals from the melt in order to determine the maximum speeds at which they could be crystallized. The technique has been modified and its application has been extended first to the growth of silicon and later to a very wide range of compound semiconductors, metals, oxides and halides. It is now the dominant technique for the wide range of materials in the electronic industries. Czochralski growth is initiated by dipping a seed crystal of a chosen crystallographic orientation onto the surface of a melt contained in the heated crucible. The seed is then slowly withdrawn, solidifying the adherent column of the melt in steady state at an average rate given by the sum of the pulling rate and the rate of lowering the solid-liquid interface due to the depletion of the melt in the crucible. The control of the desired crystal diameter is achieved by closely controlling the heat balance at the solid-liquid interface.

  10. LSA Large Area Silicon Sheet Task Continuous Liquid Feed Czochralski Growth

    NASA Technical Reports Server (NTRS)

    Fiegl, G.

    1979-01-01

    A process for the continuous growth of crystals by the Czochralski method, suitable for producing single silicon crystals for use in solar cells was studied. Continuous growth is the growth of 100 Kg of single silicon crystals, 10 cm in diameter, from one container. A furnace with continuous liquid replenishment of the growth crucible, accomplished by a melt-down system and a liquid transfer mechanism, with associated automatic feedback controls was developed. Elements of the transfer system were further developed and tested during actual transfer runs. Considerable simplification of the heating element of the transfer tube was achieved. Accuracy and reliability of the temperature sensor, which is part of the power input control system for the transfer tube, was improved. Electrical and thermal effectiveness were increased while assembly of the transfer tube system was further simplified.

  11. Fully three dimensional numerical analysis of industrial scale silicon Czochralski growth with a transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Yokoyama, R.; Nakamura, T.; Fujiwara, T.; Hamaogi, K.; Takatani, K.

    2017-06-01

    Fully three dimensional (3D) numerical simulation model of the heat and mass transfer in the silicon (Si) Czochralski growth with a transverse magnetic field (MCZ) was developed. Time transient calculation of heat and mass transfer in the industrial scale crystal growth of 300 mm diameter was performed under the quasi steady state assumption. The model predicts the completely asymmetrically 3D melt flow and off-centered temperature distributions, different from the previous works. The temperature distribution measured experimentally by thermocouples, beneath the melt surface along the azimuthal direction, was almost the same as the model prediction, providing a strong support for the 3D simulation model.

  12. Czochralski growth and laser performance of alexandrite crystals

    NASA Astrophysics Data System (ADS)

    Guo, Xing-an; Zhang, Bang-xing; Wu, Lu-sheng; Chen, Mei-Ling

    1986-08-01

    Alexandrite (BeAl2O4:Cr3+) crystals have been growing by the Czochralski technique and continually tunable laser output with energy of 304 mJ and slope efficiency of 0.46% in the wavelength range from 735 to 786 nm has been obtained using c-axis rods. Tunable Q-switch pulse output and LiIO3 double-frequency have been also obtained.

  13. Czochralski growth and laser performance of alexandrite crystals

    SciTech Connect

    Guo, X.; Zhang, B.; Wu, L.; Chen, M.

    1986-08-15

    Alexandrite (BeAl/sub 2/O/sub 4/:Cr/sup 3 +/) crystals have been growing by the Czochralski technique and continually tunable laser output with energy of 304 mJ and slope efficiency of 0.46% in the wavelength range from 735 to 786 nm has been obtained using c-axis rods. Tunable Q-switch pulse output and LiIO/sub 3/ double-frequency have been also obtained.

  14. Two-Crucible Czochralski Process

    NASA Technical Reports Server (NTRS)

    Fiegl, G.; Torbet, W.

    1985-01-01

    Scheme for continuous melt replenishment increases capacity of Czochralski crystal-growing furnace. Replenishing and drawing crucibles of improved Czochralski apparatus connected by heated quartz siphon. When doped silicon added to replenishing crucible, liquid silicon flows into drawing crucible, equalizing two melt levels. Addition of new material automatically controlled in response to optically sensed melt level. Results of this semicontinuous operation higher production speed, lower cost, and good control of crystal quality.

  15. Experimental and theoretical evidence for vacancy-clustering-induced large voids in Czochralski-grown germanium crystals

    NASA Astrophysics Data System (ADS)

    Hens, S.; Vanhellemont, J.; Poelman, D.; Clauws, P.; Romandic, I.; Theuwis, A.; Holsteyns, F.; Van Steenbergen, J.

    2005-08-01

    Optical inspection of polished Czochralski-grown Ge wafers typically reveals the presence of surface pits similar to the Crystal Originated Particles (COP's) observed in silicon but in a wider variety of sizes and shapes. Computer simulation of vacancy clustering during the Cz germanium crystal growth suggests that the surface pits originate from large voids formed by the diffusion-limited clustering of an excess of vacancies.

  16. Titanium distribution in Ti-sapphire single crystals grown by Czochralski and Verneuil technique

    NASA Astrophysics Data System (ADS)

    Alombert-Goget, G.; Li, H.; Faria, J.; Labor, S.; Guignier, D.; Lebbou, K.

    2016-01-01

    The distributions of Ti3+ and Ti4+ ions were evaluated by photoluminescence measurement in the wafers cut from different positions of the ingots grown by Czochralski and Verneuil techniques. Particular radial distributions of Ti4+ as function of the position in the ingot were observed in the crystals grown by Verneuil technique different than the crystals grown by Czochralski method.

  17. Physical modelling of Czochralski crystal growth in horizontal magnetic field

    NASA Astrophysics Data System (ADS)

    Grants, Ilmārs; Pal, Josef; Gerbeth, Gunter

    2017-07-01

    This study addresses experimentally the heat transfer, the temperature azimuthal non-uniformity and the onset of oscillations in a low temperature physical model of a medium-sized Czochralski crystal growth process with a strong horizontal magnetic field (HMF). It is observed that under certain conditions the integral heat flux may decrease with increasing magnetic field strength at the same time as the flow velocity increases. The azimuthal non-uniformity of the temperature field in the melt near the crystal model rim is only little influenced by its rotation rate outside of a narrow range where the centrifugal force balances the buoyant one. The flow oscillation onset has been observed for two values of the HMF strength. Conditions of this onset are little influenced by the crystal rotation. The critical temperature difference of the oscillation onset considerably exceeds that of the Rayleigh-Bénard (RB) cell in a strong HMF.

  18. Growth of LGSO: Ce crystals by the Czochralski method

    SciTech Connect

    Sidletskiy, O. Ts.; Bondar, V. G. Grynyov, B. V.; Kurtsev, D. A.; Baumer, V. N.; Belikov, K. N.; Shtitelman, Z. V.; Tkachenko, S. A.; Zelenskaya, O. V.; Starzhinsky, N. G.; Tarasov, V. A.

    2009-12-15

    Single crystals of Lu{sub 2x}Gd{sub 2-2x}SiO{sub 5}: Ce (0 < x < 1) compounds with different atomic ratios Lu/(Lu + Gd) have been grown by the Czochralski method. It has been shown that a change in the spatial symmetry from P2{sub 1}/c to C2/c in the course of substitution of lutetium for gadolinium occurs at the ratio Lu/(Lu + Gd) = 0.1. The lattice thus formed with symmetry C2/c in the structure of Lu{sub 2x}Gd{sub 2-2x}SiO{sub 5}: Ce crystals favors the maximum possible incorporation of Ce{sup 3+} ions into the sevenfold-coordinated position with respect to oxygen. This explains the substantial improvement of the scintillation characteristics of the grown crystals.

  19. Shallow Melt Apparatus for Semicontinuous Czochralski Crystal Growth

    DOEpatents

    Wang, T.; Ciszek, T. F.

    2006-01-10

    In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt crucible (20) to eliminate the necessity supplying a large quantity of feed stock materials that had to be preloaded in a deep crucible to grow a large ingot, comprising a gas tight container a crucible with a deepened periphery (25) to prevent snapping of a shallow melt and reduce turbulent melt convection; source supply means for adding source material to the semiconductor melt; a double barrier (23) to minimize heat transfer between the deepened periphery (25) and the shallow melt in the growth compartment; offset holes (24) in the double barrier (23) to increase melt travel length between the deepened periphery (25) and the shallow growth compartment; and the interface heater/heat sink (22) to control the interface shape and crystal growth rate.

  20. Czochralski growth of gallium indium antimonide alloy crystals

    SciTech Connect

    Tsaur, S.C.

    1998-02-01

    Attempts were made to grow alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb by the conventional Czochralski process. A transparent furnace was used, with hydrogen purging through the chamber during crystal growth. Single crystal seeds up to about 2 to 5 mole% InSb were grown from seeds of 1 to 2 mole% InSb, which were grown from essentially pure GaSb seeds of the [111] direction. Single crystals were grown with InSb rising from about 2 to 6 mole% at the seed ends to about 14 to 23 mole% InSb at the finish ends. A floating-crucible technique that had been effective in reducing segregation in doped crystals, was used to reduce segregation in Czochralski growth of alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb. Crystals close to the targeted composition of 1 mole% InSb were grown. However, difficulties were encountered in reaching higher targeted InSb concentrations. Crystals about 2 mole% were grown when 4 mole% was targeted. It was observed that mixing occurred between the melts rendering the compositions of the melts; and, hence, the resultant crystal unpredictable. The higher density of the growth melt than that of the replenishing melt could have triggered thermosolutal convection to cause such mixing. It was also observed that the floating crucible stuck to the outer crucible when the liquidus temperature of the replenishing melt was significantly higher than that of the growth melt. The homogeneous Ga{sub 1{minus}x}In{sub x}Sb single crystals were grown successfully by a pressure-differential technique. By separating a quartz tube into an upper chamber for crystal growth and a lower chamber for replenishing. The melts were connected by a capillary tube to suppress mixing between them. A constant pressure differential was maintained between the chambers to keep the growth melt up in the growth chamber. The method was first tested with a low temperature alloy Bi{sub 1{minus}x}Sb{sub x}. Single crystals of Ga{sub 1{minus}x}In{sub x}Sb were grown with uniform

  1. Nano-Scale Analysis of Precipitates in Nitrogen-Doped Czochralski SIlicon

    SciTech Connect

    Rozgonyi, G. A.; Karoui, A.; Kvit, A.; Duscher, Gerd J M

    2003-01-01

    Nitrogen-doped Czochralski (CZ) silicon wafers were heat treated with Lo-Hi annealing in argon. Nanoscale defects were then examined by high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) in the Z-contrast mode, and electron energy loss spectroscopy (EELS) analyses using a field emission JEOL 2010 with a resolution below 2 {angstrom}. The structures of precipitates, stacking faults and interstitial aggregates were found to depend on their location relative to the wafer surface. Precipitate composition, strain at the interface and interface roughness were obtained and are discussed in connection with the point defects generated during crystal growth and modified during wafer annealing. An excellent correlation was found between Z-contrast line scans across the precipitates and the N to O concentration ratio determined with EELS. In the precipitate central region that ratio is between 1 and 6%, whereas at precipitate boundaries it reaches 17%.

  2. The growth of Ho:YAG single crystals by Czochralski method and investigating the formed cores

    SciTech Connect

    Hasani Barbaran, J. Ghani Aragi, M. R.; Javaheri, I.; Baharvand, B.; Tabasi, M.; Layegh Ahan, R.; Jangjo, E.

    2015-12-15

    Ho:YAG single crystals were grown by Czochralski technique, and investigated by the X-ray diffraction (XRD) and optical methods. The crystals were cut and polished in order to observe and analyze their cores. It was found that the deviation of the cores formed in the Czochralski grown Ho:YAG single crystals are resulted from non-symmetrical status of thermal insulation around the Iridium crucible.

  3. Development of advanced Czochralski growth process to produce low cost 150 kg silicon ingots from a single crucible for technology readiness. [crystal growth

    NASA Technical Reports Server (NTRS)

    Lane, R. L.

    1981-01-01

    Six growth runs used the Kayex-Hameo Automatic Games Logic (AGILE) computer based system for growth from larger melts in the Mod CG2000. The implementation of the melt pyrometer sensor allowed for dip temperature monitoring and usage by the operator/AGILE system. Use of AGILE during recharge operations was successfully evaluated. The tendency of crystals to lose cylindrical shape (spiraling) continued to be a problem. The hygrometer was added to the Furnace Gas Analysis System and used on several growth runs. The gas chromatograph, including the integrator, was also used for more accurate carbon monoxide concentration measurements. Efforts continued for completing the automation of the total Gas Analysis System. An economic analysis, based on revised achievable straight growth rate, is presented.

  4. A preliminary review of organic materials single crystal growth by the Czochralski technique

    NASA Technical Reports Server (NTRS)

    Penn, B. G.; Shields, A. W.; Frazier, D. O.

    1988-01-01

    The growth of single crystals of organic compounds by the Czochralski method is reviewed. From the literature it is found that single crystals of benzil, a nonlinear optical material with a d sub 11 value of 11.2 + or - 1.5 x d sub 11 value of alpha quartz, has fewer dislocations than generally contained in Bridgman crystals. More perfect crystals were grown by repeated Czochralski growth. This consists of etching away the defect-containing portion of a Czochralski grown crystal and using it as a seed for further growth. Other compounds used to grow single crystals are benzophenone, 12-tricosanone (laurone), and salol. The physical properties, growth apparatus, and processing conditions presented in the literature are discussed. Moreover, some of the possible advantages of growing single crystals of organic compounds in microgravity to obtain more perfect crystals than on Earth are reviewed.

  5. Analysis of Phase Separation in Czochralski Grown Single Crystal Ilmenite

    NASA Technical Reports Server (NTRS)

    Wilkins, R.; Powell, Kirk St. A.; Loregnard, Kieron R.; Lin, Sy-Chyi; Muthusami, Jayakumar; Zhou, Feng; Pandey, R. K.; Brown, Geoff; Hawley, M. E.

    1998-01-01

    Ilmenite (FeTiOs) is a wide bandgap semiconductor with an energy gap of 2.58 eV. Ilmenite has properties suited for radiation tolerant applications, as well as a variety of other electronic applications. Single crystal ilmenite has been grown from the melt using the Czochralski method. Growth conditions have a profound effect on the microstructure of the samples. Here we present data from a variety of analytical techniques which indicate that some grown crystals exhibit distinct phase separation during growth. This phase separation is apparent for both post-growth annealed and unannealed samples. Under optical microscopy, there appear two distinct areas forming a matrix with an array of dots on order of 5 pm diameter. While appearing bright in the optical micrograph, atomic force microscope (AFM) shows the dots to be shallow pits on the surface. Magnetic force microscope (MFM) shows the dots to be magnetic. Phase identification via electron microprobe analysis (EMPA) indicates two major phases in the unannealed samples and four in the annealed samples, where the dots appear to be almost pure iron. This is consistent with micrographs taken with a scanning probe microscope used in the magnetic force mode. Samples that do not exhibit the phase separation have little or no discernible magnetic structure detectable by the MFM.

  6. Analysis of Phase Separation in Czochralski Grown Single Crystal Ilmenite

    NASA Technical Reports Server (NTRS)

    Wilkins, R.; Powell, Kirk St. A.; Loregnard, Kieron R.; Lin, Sy-Chyi; Muthusami, Jayakumar; Zhou, Feng; Pandey, R. K.; Brown, Geoff; Hawley, M. E.

    1998-01-01

    Ilmenite (FeTiOs) is a wide bandgap semiconductor with an energy gap of 2.58 eV. Ilmenite has properties suited for radiation tolerant applications, as well as a variety of other electronic applications. Single crystal ilmenite has been grown from the melt using the Czochralski method. Growth conditions have a profound effect on the microstructure of the samples. Here we present data from a variety of analytical techniques which indicate that some grown crystals exhibit distinct phase separation during growth. This phase separation is apparent for both post-growth annealed and unannealed samples. Under optical microscopy, there appear two distinct areas forming a matrix with an array of dots on order of 5 pm diameter. While appearing bright in the optical micrograph, atomic force microscope (AFM) shows the dots to be shallow pits on the surface. Magnetic force microscope (MFM) shows the dots to be magnetic. Phase identification via electron microprobe analysis (EMPA) indicates two major phases in the unannealed samples and four in the annealed samples, where the dots appear to be almost pure iron. This is consistent with micrographs taken with a scanning probe microscope used in the magnetic force mode. Samples that do not exhibit the phase separation have little or no discernible magnetic structure detectable by the MFM.

  7. Characterization of the loss of the dislocation-free growth during Czochralski silicon pulling

    NASA Astrophysics Data System (ADS)

    Lanterne, Adeline; Gaspar, Guilherme; Hu, Yu; Øvrelid, Eivind; Di Sabatino, Marisa

    2017-01-01

    The loss of the dislocation-free growth (structure loss) during Czochralski (Cz) silicon pulling can have a strong negative impact on the production yield of the Cz photovoltaic industry. As almost no publication has been dedicated to this phenomenon in the past, this paper aims at investigate in detail the loss of the dislocation-free growth and its origin by characterizing an industrial-scale n-type Cz silicon ingot exhibiting such issue. After the occurrence of a perturbation, generation and propagation of slip dislocations in the already grown crystal have been observed. These dislocations, generated over the whole ingot cross-section, propagate with the solidification front during further growth. Additional small perturbations seem then to be responsible for their multiplication together with the transition to a multicrystalline structure. Investigations were conducted to find the perturbation causing the structure loss in the ingot. A pinhole, small gas bubble of 0.5 mm diameter, was identified as the main cause for the generation of dislocations.

  8. Hydrogen-accelerated thermal donor formation in Czochralski silicon

    SciTech Connect

    Stein, H.J. ); Hahn, S.K. )

    1990-01-01

    Acceleration of thermal donor formation at 400 {degree}C in Czochralski Si by a hydrogen plasma has been observed using low-temperature infrared absorption and spreading resistance probe measurements. The accelerated formation in as-grown Si is attributed to hydrogen diffusion and catalyzed conversion of electrically inactive nuclei to thermal donors. When the nuclei concentration is small such as in rapid thermal annealed Si, hydrogen interaction at SiO bonds is suggested as the rate-limiting step in thermal donor formation.

  9. Suppression of boron-oxygen defects in Czochralski silicon by carbon co-doping

    SciTech Connect

    Wu, Yichao; Yu, Xuegong He, Hang; Chen, Peng; Yang, Deren

    2015-03-09

    We have investigated the influence of carbon co-doping on the formation of boron-oxygen defects in Czochralski silicon. It is found that carbon can effectively suppress the formation of boron-oxygen defects. Based on our experiments and first-principle theoretical calculations, it is believed that this effect is attributed to the formation of more energetically favorable carbon-oxygen complexes. Moreover, the diffusion of oxygen dimers in carbon co-doped silicon also becomes more difficult. All these phenomena should be associated with the tensile stress field induced by carbon doping in silicon.

  10. Cold crucible Czochralski for solar cells

    NASA Technical Reports Server (NTRS)

    Trumble, T. M.

    1982-01-01

    The efficiency and radiation resistance of present silicon solar cells are a function of the oxygen and carbon impurities and the boron doping used to provide the proper resistivity material. The standard Czochralski process used grow single crystal silicon contaminates the silicon stock material due to the use of a quartz crucible and graphite components. The use of a process which replaces these elements with a water cooled copper to crucible has provided a major step in providing gallium doped (100) crystal orientation, low oxygen, low carbon, silicon. A discussion of the Cold Crucible Czochralski process and recent float Zone developments is provided.

  11. Charge collection measurements with p-type Magnetic Czochralski silicon single pad detectors

    NASA Astrophysics Data System (ADS)

    Tosi, C.; Bruzzi, M.; Macchiolo, A.; Scaringella, M.; Petterson, M. K.; Sadrozinski, H. F.-W.; Betancourt, C.; Manna, N.; Creanza, D.; Boscardin, M.; Piemonte, C.; Zorzi, N.; Borrello, L.; Messineo, A.

    2007-09-01

    The charge collected from beta source particles in single pad detectors produced on p-type Magnetic Czochralski (MCz) silicon wafers has been measured before and after irradiation with 26 MeV protons. After a 1 MeV neutron equivalent fluence of 1×1015 cm-2 the collected charge is reduced to 77% at bias voltages below 900 V. This result is compared with previous results from charge collection measurements.

  12. Rapid thermal processing of Czochralski silicon substrates: Defects, denuded zones, and minority carrier lifetime

    NASA Technical Reports Server (NTRS)

    Rozgonyi, G. S.; Yang, D. K.; Cao, Y. H.; Radzimski, Z.

    1986-01-01

    Rapid thermal processing (RTP) of Czochralski (Cz) silicon substrates is discussed with its attendant effects on defects, denuded zones, and minority carrier lifetime. Preferential chemical etching and X-ray topography was used to delineate defects which were subsequently correlated with minority carrier lifetime; determined by a pulse metallo-organic decompositon (MOD) test device. The X-ray delineation of grown-in defects was enhanced by a lithium decoration procedure. Results, thus far, show excellent correlation between process-induced defects.

  13. Advanced Czochralski silicon growth technology for photovoltaic modules

    NASA Technical Reports Server (NTRS)

    Daud, T.; Kachare, A. H.

    1982-01-01

    Several economic analyses had indicated that large-diameter, multiple ingot growth using a single crucible with melt replenishment would be required for Cz growth to be economically viable. Based on the results of these analyses, two liquid and two solid feed melt replenishment approaches were initiated. The sequential solid feed melt replenishment approach, which demonstrated elements of technical feasibility is described in detail in this paper. Growth results of multiple ingots (10-cm-diameter, totaling 100 kg; and 15-cm-diameter, totaling 150 kg weight per crucible) are presented. Solar cells were fabricated and analyzed to evaluate the effects of structure and chemical purities as a result of multiple growth. The results indicate that, with semiconductor-grade silicon, feedstock impurity build-up does not seem to degrade cell performance. For polycrystalline cells, the average efficiencies are 15 to 25% lower than those of single crystalline cells. Concerns regarding single crystal yields, crucible quality and growth speed are indicated, and present status and future research thrusts are also discussed.

  14. Microhardness of carbon-doped (111) p-type Czochralski silicon

    NASA Technical Reports Server (NTRS)

    Danyluk, S.; Lim, D. S.; Kalejs, J.

    1985-01-01

    The effect of carbon on (111) p-type Czochralski silicon is examined. The preparation of the silicon and microhardness test procedures are described, and the equation used to determine microhardness from indentations in the silicon wafers is presented. The results indicate that as the carbon concentration in the silicon increases the microhardness increases. The linear increase in microhardness is the result of carbon hindering dislocation motion, and the effect of temperature on silicon deformation and dislocation mobility is explained. The measured microhardness was compared with an analysis which is based on dislocation pinning by carbon; a good correlation was observed. The Labusch model for the effect of pinning sites on dislocation motion is given.

  15. Microhardness of carbon-doped (111) p-type Czochralski silicon

    NASA Technical Reports Server (NTRS)

    Danyluk, S.; Lim, D. S.; Kalejs, J.

    1985-01-01

    The effect of carbon on (111) p-type Czochralski silicon is examined. The preparation of the silicon and microhardness test procedures are described, and the equation used to determine microhardness from indentations in the silicon wafers is presented. The results indicate that as the carbon concentration in the silicon increases the microhardness increases. The linear increase in microhardness is the result of carbon hindering dislocation motion, and the effect of temperature on silicon deformation and dislocation mobility is explained. The measured microhardness was compared with an analysis which is based on dislocation pinning by carbon; a good correlation was observed. The Labusch model for the effect of pinning sites on dislocation motion is given.

  16. A DLTS study of hydrogen doped czochralski-grown silicon

    NASA Astrophysics Data System (ADS)

    Jelinek, M.; Laven, J. G.; Kirnstoetter, S.; Schustereder, W.; Schulze, H.-J.; Rommel, M.; Frey, L.

    2015-12-01

    In this study we examine proton implanted and subsequently annealed commercially available CZ wafers with the DLTS method. Depth-resolved spreading resistance measurements are shown, indicating an additional peak in the induced doping profile, not seen in the impurity-lean FZ reference samples. The additional peak lies about 10-15 μm deeper than the main peak near the projected range of the protons. A DLTS characterization in the depth of the additional peak indicates that it is most likely not caused by classical hydrogen-related donors known also from FZ silicon but by an additional donor complex whose formation is assisted by the presence of silicon self-interstitials.

  17. A versatile low-cost Czochralski crystal growth system for nonlinear optical organic materials

    NASA Technical Reports Server (NTRS)

    Aggarwal, M. D.; Wang, W. S.; Shields, Angela W.; Penn, Benjamin G.; Frazier, Donald O.

    1992-01-01

    A versatile low-cost Czochralski system for pulling crystals from melt has been described. It is designed for low melting, transparent, and nonlinear optical materials. One of the most important novel feature of this crystal growth system is that the entire growth process including the solid-liquid interface can be viewed from any direction. Another is the use of an after-heater to reduce excess heat loss from the surface of the melt.

  18. A versatile low-cost Czochralski crystal growth system for nonlinear optical organic materials

    NASA Technical Reports Server (NTRS)

    Aggarwal, M. D.; Wang, W. S.; Shields, Angela W.; Penn, Benjamin G.; Frazier, Donald O.

    1992-01-01

    A versatile low-cost Czochralski system for pulling crystals from melt has been described. It is designed for low melting, transparent, and nonlinear optical materials. One of the most important novel feature of this crystal growth system is that the entire growth process including the solid-liquid interface can be viewed from any direction. Another is the use of an after-heater to reduce excess heat loss from the surface of the melt.

  19. Further evidence for the C-line pseudodonor model in irradiated Czochralski-grown silicon

    SciTech Connect

    Kleverman, M.; Fornell, J.; Olajos, J.; Grimmeiss, H.G.; Lindstroem, J.L.

    1988-06-15

    Photocurrent spectroscopy and photothermal ionization spectroscopy have been performed on electron-irradiated Czochralski-grown silicon. Two series of lines are observed, one starting with the C line at 790 meV, and another starting at about 30 meV higher energy. The lines are shown to belong to the same continuum, indicating that they are all associated with the same center. A continuum is also observed, and in this part of the spectrum Fano resonances are seen. The analysis of these resonances implies that the free-carrier states couple with an f TO phonon, and this confirms the view that the center is donorlike.

  20. Further evidence for the C-line pseudodonor model in irradiated Czochralski-grown silicon

    NASA Astrophysics Data System (ADS)

    Kleverman, M.; Fornell, J.-O.; Olajos, J.; Grimmeiss, H. G.; Lindström, J. L.

    1988-06-01

    Photocurrent spectroscopy and photothermal ionization spectroscopy have been performed on electron-irradiated Czochralski-grown silicon. Two series of lines are observed, one starting with the C line at 790 meV, and another starting at about 30 meV higher energy. The lines are shown to belong to the same continuum, indicating that they are all associated with the same center. A continuum is also observed, and in this part of the spectrum Fano resonances are seen. The analysis of these resonances implies that the free-carrier states couple with an f TO phonon, and this confirms the view that the center is donorlike.

  1. Charge collection and capacitance voltage analysis in irradiated n-type magnetic Czochralski silicon detectors

    NASA Astrophysics Data System (ADS)

    Petterson, M. K.; Sadrozinski, H. F.-W.; Betancourt, C.; Bruzzi, M.; Scaringella, M.; Tosi, C.; Macchiolo, A.; Manna, N.; Creanza, D.; Boscardin, M.; Piemonte, C.; Zorzi, N.; Borrello, L.; Messineo, A.; Dalla Betta, G. F.

    2007-12-01

    The depletion depth of irradiated n-type silicon microstrip detectors can be inferred from both the reciprocal capacitance and from the amount of collected charge. Capacitance voltage ( C- V) measurements at different frequencies and temperatures are being compared with the bias voltage dependence of the charge collection on an irradiated n-type magnetic Czochralski silicon detector. Good agreement between the reciprocal capacitance and the median collected charge is found when the frequency of the C- V measurement is selected such that it scales with the temperature dependence of the leakage current. Measuring C- V characteristics at prescribed combinations of temperature and frequency allows then a realistic estimate of the depletion characteristics of irradiated silicon strip detectors based on C- V data alone.

  2. Hydrogen diffusion at moderate temperatures in p-type Czochralski silicon

    SciTech Connect

    Huang, Y.L.; Ma, Y.; Job, R.; Ulyashin, A.G.

    2004-12-15

    In plasma-hydrogenated p-type Czochralski silicon, rapid thermal donor (TD) formation is achieved, resulting from the catalytic support of hydrogen. The n-type counter doping by TD leads to a p-n junction formation. A simple method for the indirect determination of the diffusivity of hydrogen via applying the spreading resistance probe measurements is presented. Hydrogen diffusion in silicon during both plasma hydrogenation and post-hydrogenation annealing is investigated. The impact of the hydrogenation duration, annealing temperature, and resistivity of the silicon wafers on the hydrogen diffusion is discussed. Diffusivities of hydrogen are determined in the temperature range 270-450 deg. C. The activation energy for the hydrogen diffusion is deduced to be 1.23 eV. The diffusion of hydrogen is interpreted within the framework of a trap-limited diffusion mechanism. Oxygen and hydrogen are found to be the main traps.

  3. Process research of non-Czochralski silicon material

    NASA Technical Reports Server (NTRS)

    Campbell, R. B.

    1986-01-01

    Simultaneous diffusion of liquid precursors containing phosphorus and boron into dendritic web silicon to form solar cell structures was investigated. A simultaneous junction formation techniques was developed. It was determined that to produce high quality cells, an annealing cycle (nominal 800 C for 30 min) should follow the diffusion process to anneal quenched-in defects. Two ohm-cm n-base cells were fabricated with efficiencies greater than 15%. A cost analysis indicated that the simultansous diffusion process costs can be as low as 65% of the costs of the sequential diffusion process.

  4. KNbO3 single crystal growth by the radio frequency heating Czochralski method

    NASA Technical Reports Server (NTRS)

    Wang, W.; Zou, Q.; Geng, Z.

    1985-01-01

    A radio frequency heating Czochralski technique to obtain single crystal KNbO3 is first presented. The technological parameters of KNbO3 crystal growth by the Czochralski technique and its pulling conditions were studied in detail. The experiments on second harmonic generation using 1.06 micrometer Nd:YAG laser in KNbO3 have been conducted. The second harmonic efficiency for upconversion of KNbO3 is found to be as high as that of NaBa2Nb5O15. An automatic scanning measurement for the optical homogeneity of KNbO crystal is also described. KNbO3 is revealed to be a potentially useful nonlinear material for optical device applications.

  5. The Czochralski Growth and Characterization of SrLaGa3O7:Ho(3+) Single Crystals

    DTIC Science & Technology

    2001-01-01

    1.5 and 2 at % of Ho3’, respectively were grown by the Czochralski method with use of iridium crucible and afterheater. According to EPMA measurements...The following dopant concentrations were introduced into the charge 0.3, 1.5 and 2 at. %. Single crystals were grown by the Czochralski method with...SrLaGa 30 7 in dependence on temperature. 5. CONCLUSIONS Single crystals of SrLaGa 30 7 doped with holmium were obtained by the Czochralski method . Optical

  6. Crystal-melt interface shape of Czochralski-grown large diameter germanium crystals

    NASA Technical Reports Server (NTRS)

    Roth, M.; Azoulay, M.; Gafni, G.; Mizrachi, M.

    1990-01-01

    Crystal-melt interface shapes of 100 to 200 mm diameter 111-line Ge grown by the Czochralski technique have been examined using the method of fast withdrawal from the melt. Initially, the interface shape is convex, then transforms gradually into a sigmoidal shape, becomes nearly planar at about one third of the final crystal length, and finally assumes a concave profile with progressively increasing curvature. The nearly planar interface has a double-facet structure, with an annular facet at the edge of the crystal in addition to the central (111) facet. Formation of the annular facet is accompanied by a giant oscillation of the pull rate when the maximum average pull rate is exceeded. Such oscillation is detrimental to crystal quality, since it introduces a region of high dislocation density. An average pull rate maximum of 2 cm/h has been found to allow for a smooth growth of 200 mm diameter crystals. The origin of the pull rate perturbation is discussed in terms of an instantaneous change in the equilibrium shape of the meniscus.

  7. Crystal-melt interface shape of Czochralski-grown large diameter germanium crystals

    NASA Technical Reports Server (NTRS)

    Roth, M.; Azoulay, M.; Gafni, G.; Mizrachi, M.

    1990-01-01

    Crystal-melt interface shapes of 100 to 200 mm diameter 111-line Ge grown by the Czochralski technique have been examined using the method of fast withdrawal from the melt. Initially, the interface shape is convex, then transforms gradually into a sigmoidal shape, becomes nearly planar at about one third of the final crystal length, and finally assumes a concave profile with progressively increasing curvature. The nearly planar interface has a double-facet structure, with an annular facet at the edge of the crystal in addition to the central (111) facet. Formation of the annular facet is accompanied by a giant oscillation of the pull rate when the maximum average pull rate is exceeded. Such oscillation is detrimental to crystal quality, since it introduces a region of high dislocation density. An average pull rate maximum of 2 cm/h has been found to allow for a smooth growth of 200 mm diameter crystals. The origin of the pull rate perturbation is discussed in terms of an instantaneous change in the equilibrium shape of the meniscus.

  8. Scale up aspects of directional solidification and Czochralski silicon growth processes in traveling magnetic fields

    NASA Astrophysics Data System (ADS)

    Dropka, Natasha; Ervik, Torunn; Czupalla, Matthias; Kiessling, Frank M.

    2016-10-01

    We performed 3D simulations of directional solidification (DS) and Czochralski (Cz) silicon growth processes in traveling magnetic fields (TMFs) and verified them with the experimental data that were available. Particularly, we studied silicon DS growth in real G1, G2 and G5 size setups and Cz growth in 6″ and 24″ crucibles in furnaces provided with KRISTMAG® heater magnet modules (HMMs). TMFs were used for a solid/liquid interface shaping and for a melt stirring. Based on our simulation findings, we discussed scale up challenges and proposed a method for safe upscaling. The method related all present driving forces using dimensionless numbers: Grashof (Gr), Stephan (Ste), Reynolds (Re), Shielding (S) and magnetic forcing number (F).

  9. In-situ detection of growth striations by crystallization electromotive force measurement during Czochralski crystal growth

    NASA Astrophysics Data System (ADS)

    Zhu, Yunzhong; Ma, Decai; Long, Siwei; Tang, Feng; Lin, Shaopeng; Wang, Biao

    2017-10-01

    Growth striations, as macrodefects of crystalline materials, are mainly caused by convection and temperature fluctuations in growth interface. For decades, striations have been widely regarded as an inherent problem. Even in the well-developed Czochralski method, the striation formation process is difficult to inspect in situ. In view of this long-standing issue, after systematically studying the temperature, weight, and output power during crystal growth and numerically modeling the growth process, we found that the regularity of the growth interface electromotive force (GEMF) is related to the distribution of striations. Furthermore, the GEMF quantifies interface fluctuations (711.2 s, 16.6 μm) and thermal hysteresis (107 s), presenting finer details than those provided by a thermocouple and a load cell. In this paper, GEMF is found to be an outstanding choice for monitoring the crystal growth status in real time. As an additional feedback, a new automatic control method could be developed for reducing growth striations and promoting crystal quality.

  10. Crystal growth of MCZ silicon with ultralow carbon concentration

    NASA Astrophysics Data System (ADS)

    Nagai, Y.; Nakagawa, S.; Kashima, K.

    2014-09-01

    In this study, we investigated the evaporation of carbon monoxide (CO) from silicon melt during crystal growth by evaluating the carbon concentrations in the crystals using photoluminescence (PL) spectroscopy. In order to achieve greater carrier lifetimes in magnetic-field-induced Czochralski (MCZ) silicon for high-power insulated-gate bipolar transistor (IGBT) devices, we focused on the reduction of carbon impurities in MCZ silicon, that act as heterogeneous nucleation sites for oxygen precipitates. To obtain MCZ silicon with a carbon concentration lower than that of floating-zone (FZ) silicon, it is necessary to prevent the back-diffusion of CO from the hot graphite components into the melt and promote CO evaporation from the melt. By promoting CO evaporation, we managed to grow 6-in. CZ silicon crystals with a carbon concentration lower than 1.0×1014 atoms/cm3 at a solidified fraction of 80%.

  11. Modelling of melt motion in a Czochralski crystal puller with an axial magnetic field

    NASA Astrophysics Data System (ADS)

    Hjellming, L. N.; Walker, J. S.

    1986-12-01

    The use of matched asymptotic expansions provide analytical solutions for the bulk flow in a Czochralski crystal puller in a strong axial magnetic field. Treating the crystal as a slight electrical conductor alters the radial and axial flows driven by centrifugal pumping. The motion due to buoyancy and thermocapillarity are found by considering the temperature as a known function and solving the non-linear heat equation numerically for different magnetic field strengths and melt depths. This note presents a summary of the analysis and results that are detailed in two papers.

  12. Misfit strain of oxygen precipitates in Czochralski silicon studied with energy-dispersive X-ray diffraction

    SciTech Connect

    Gröschel, A. Will, J.; Bergmann, C.; Magerl, A.

    2014-06-21

    Annealed Czochralski Silicon wafers containing SiO{sub x} precipitates have been studied by high energy X-ray diffraction in a defocused Laue setup using a laboratory tungsten tube. The energy dispersive evaluation of the diffracted Bragg intensity of the 220 reflection within the framework of the statistical dynamical theory yields the static Debye-Waller factor E of the crystal, which gives access to the strain induced by the SiO{sub x} precipitates. The results are correlated with precipitate densities and sizes determined from transmission electron microscopy measurements of equivalent wafers. This allows for the determination of the constrained linear misfit ε between precipitate and crystal lattice. For samples with octahedral precipitates the values ranging from ε = 0.39 (+0.28/−0.12) to ε = 0.48 (+0.34/−0.16) indicate that self-interstitials emitted into the matrix during precipitate growth contribute to the lattice strain. In this case, the expected value calculated from literature values is ε = 0.26 ± 0.05. Further, the precise evaluation of Pendellösung oscillations in the diffracted Bragg intensity of as-grown wafers reveals a thermal Debye-Waller parameter for the 220 reflection B{sup 220}(293 K) of 0.5582 ± 0.0039 Å{sup 2} for a structure factor based on spherically symmetric scattering contributions.

  13. TCT and test beam results of irradiated magnetic Czochralski silicon (MCz-Si) detectors

    SciTech Connect

    Luukka, P.; Harkonen, J.; Maenpaa, T.; Betchart, B.; Czellar, S.; Demina, R.; Furgeri, A.; Gotra, Y.; Frey, M.; Hartmann, F.; Korjenevski, S.; /Rochester U. /Helsinki Inst. of Phys. /Karlsruhe U., EKP /Louvain U. /Karlsruhe U., EKP

    2009-01-01

    Pad and strip detectors processed on high resistivity n-type magnetic Czochralski silicon (MCz-Si) were irradiated to several different fluences with protons. The pad detectors were characterized with the transient current technique (TCT) and the full-size strip detectors with a reference beam telescope and a 225 GeV muon beam. The TCT measurements indicate a double junction structure and space charge sign inversion in MCz-Si detectors after 6x1014 1 MeV neq/cm2 fluence. In the beam test a signal-to-noise (S/N) ratio of 50 was measured for a non-irradiated MCz-Si sensor, and a S/N ratio of 20 for the sensors irradiated to the fluences of 1x1014 1 and 5x1014 1 MeV neq/cm2.

  14. Low temperature iron gettering by grown-in defects in p-type Czochralski silicon

    NASA Astrophysics Data System (ADS)

    Zhu, Haiyan; Yu, Xuegong; Zhu, Xiaodong; Wu, Yichao; He, Jian; Vanhellemont, Jan; Yang, Deren

    2016-11-01

    Low temperature iron gettering in as-grown boron doped Czochralski silicon (Cz-Si) at temperatures between 220 and 500 °C is studied using microwave-photoconductive decay based minority carrier lifetime measurements. Scanning infrared microscopy technique is used to study the defect density/size distribution in the samples before and after anneal. It is found that the decrease of interstitial iron (Fei) concentration shows a double exponential dependence on annealing time at all temperatures. This suggests the existence of two sinks for Fei. Meanwhile, the observed bulk defect densities and sizes in contaminated and as-grown samples are nearly the same, implying that the grown-in defects could be the gettering centers in this process. The results are important for understanding and controlling low temperature Fei gettering during processing of Cz-Si based devices.

  15. Experimental and numerical modeling of Czochralski crystal growth under axial vibrational control of the melt

    NASA Astrophysics Data System (ADS)

    Avetissov, I. Ch.; Sukhanova, E. A.; Sadovskii, A. P.; Kostikov, V. A.; Zharikov, E. V.

    2010-04-01

    A novel scheme of application of axial vibration control (AVC) technique for Czochralski crystal growth has been realized by means of oscillating baffle submerged under the growing crystal. Modeling of heat-mass transfer in the growth system has been produced by both physical experiments with water-glycerol mixture and computer simulations using FLUENT software. The laminar vibrational flows, which suppressed thermoconvectional flows, have been arranged in the proposed AVC configuration. The vibrational flows were stable and well controlled in the viscosity range 1-400 cPz, whenever the crystal-melt interface was under or over the melt surface. The direction of the vibrational flows was favorable for crystal growth. Simulations demonstrated that the shape of the crystal-melt interface is strongly dependent on vibrational parameters.

  16. Carbon effect on the survival of vacancies in Czochralski silicon during rapid thermal anneal

    NASA Astrophysics Data System (ADS)

    Zhao, Jian; Dong, Peng; Yuan, Kang; Qiu, Xiaodong; Zhou, Junwei; Zhao, Jianjiang; Yu, Xuegong; Ma, Xiangyang; Yang, Deren

    2017-07-01

    Rapid thermal anneal (RTA) at high temperatures can be employed to introduce vacancies to control oxygen precipitation (OP) behavior in Czochralski (CZ) silicon. Such excessive vacancies survive from the recombination of silicon-interstitials and vacancies (V-I recombination) during the RTA. In this work, we aim to elucidate the carbon effect on the survival of vacancies in CZ silicon during the high temperature RTA by means of gold diffusion in combination with deep-level transient spectroscopy. It is revealed that the existence of ˜1017 cm-3 carbon atoms significantly increases the amount of survival vacancies in the form of vacancy-oxygen (VOm, m ≥ 2) complexes in CZ silicon when subjected to the 1250 °C/60 s RTA. Moreover, such an increase in the number of vacancies becomes more significant with the increase in the cooling rate of RTA. The density functional theory calculations suggest that the V-I recombination is to some extent unfavorable as a carbon atom is close to the silicon-interstitial. Alternatively, it is believed that the substitutional carbon (Cs) atoms tend to trap the silicon-interstitials, thus forming Ci complexes (Cs + I → Ci) in CZ silicon during the RTA. In this context, the V-I recombination is suppressed in a manner, leading to the survival of more vacancies, thus generating more VOm complexes. Furthermore, after the 1250 °C/60 s RTA, the oxide precipitate nucleation based on the VOm complexes is more significant in carbon-rich CZ (CCZ) silicon than in the conventional CZ counterpart. Hence, when subjected to the same OP anneal consisting of the nucleation anneal at 650 or 800 °C for 4 h and the subsequent growth anneal at 1000 °C for 16 h, CCZ silicon possesses a higher density of bulk microdefects and therefore stronger internal gettering capability than CZ silicon. However, the nucleation temperature for OP should be carefully selected as 650 °C for CCZ silicon in order to form an oxide precipitate-free denuded zone.

  17. Light-induced degradation in compensated p- and n-type Czochralski silicon wafers

    NASA Astrophysics Data System (ADS)

    Geilker, Juliane; Kwapil, Wolfram; Rein, Stefan

    2011-03-01

    Light-induced degradation (LID) due to boron-oxygen complex formation seriously diminishes the minority carrier lifetime of p-type Czochralski-grown (Cz) wafers. Depending linearly on the boron concentration NA in uncompensated silicon, the boron-oxygen defect density was suggested to depend on the net doping concentration p0 = NA - ND in compensated p-type samples, containing similar amounts of boron and phosphorus [D. Macdonald, F. Rougieux, A. Cuevas, et al., Journal of Applied Physics 105, 093704 (2009)]. However, this dependency contradicts observations of LID in compensated n-type silicon wafers [T. Schutz-Kuchly, J. Veirman, S. Dubois, et al., Applied Physics Letters 96, 1 (2010)], which are confirmed in this study by investigating the boron-oxygen complex formation on a large variety of compensated p- and n-type samples. In spite of their high boron content, compensated n-type samples may show a less pronounced LID than p-type samples containing less boron. Our experiments indicate that in compensated silicon, the defect concentration is only a function of the compensation ratio RC = (NA + ND)/(NA - ND).

  18. Optical Properties of LiNbO3 Single Crystal Grown by Czochralski Method

    NASA Astrophysics Data System (ADS)

    Sahar, M. R.; Naim, N. M.; Hamzah, K.

    2011-03-01

    Pure LiNbO3 single crystal was grown by Czochralski method using Automatic Diameter Control—Crystal Growth System (ADC-CGS). The transmission spectrum was determined by using Infrared Spectroscopy while the refractive index was determined using UV-Vis spectroscopy via the Sellmeier equation. The density was also measured using the Archimedes principle. It was found that the peak for the absorption vibrational spectrum for LiNbO3 crystal occurs at 801 cm-1, 672 cm-1, 639 cm-1 and 435 cm-1. The refractive index, ne was found to be 2.480 and the crystal density was around 4.64 g/cm3.

  19. Czochralski growth of crystals - Simple models for growth rate and interface shape

    NASA Technical Reports Server (NTRS)

    Srivastava, R. K.; Ramachandran, P. A.; Dudukovic, M. P.

    1986-01-01

    A simple model for the crystal growth by the Czochralski (CZ) process has been proposed based on semiquantitative arguments. The model provides empirical relationships for the dependence of the pulling rate and the interface shape on the important process variables such as crystal radius, crucible temperature, height of the melt level, and the height of the exposed portion of the crucible wall. The parameters of the model can be evaluated by matching the results obtained from a detailed mathematical model of the CZ process or from extensive experimental data. The model has, therefore, the potential application for determining the best process conditions and for on-line control and optimization of the crystal puller to grow crystals with constant diameter and nearly planar interface.

  20. Simulation of the temperature distribution in crystals grown by Czochralski method

    NASA Technical Reports Server (NTRS)

    Dudokovic, M. P.; Ramachandran, P. A.

    1985-01-01

    Production of perfect crystals, free of residual strain and dislocations and with prescribed dopant concentration, by the Czochralski method is possible only if the complex, interacting phenomena that affect crystal growth in a Cz-puller are fully understood and quantified. Natural and forced convection in the melt, thermocapillary effect and heat transfer in and around the crystal affect its growth rate, the shape of the crystal-melt interface and the temperature gradients in the crystal. The heat transfer problem in the crystal and between the crystal and all other surfaces present in the crystal pulling apparatus are discussed at length. A simulation and computer algorithm are used, based on the following assumptions: (1) only conduction occurs in the crystal (experimentally determined conductivity as a function of temperature is used), (2) melt temperature and the melt-crystal heat transfer coefficient are available (either as constant values or functions of radial position), (3) pseudo-steady state is achieved with respect to temperature gradients, (4) crystal radius is fixed, and (5) both direct and reflected radiation exchange occurs among all surfaces at various temperatures in the crystal puller enclosure.

  1. Growth of CaLnA10/sub 4/ crystals by the Czochralski method

    SciTech Connect

    Appen, Z.S.; Korovkin, A.M.; Romanov, A.Y.; Udalov, Y.P.; Valtere, A.Y.

    1986-05-01

    The authors grew crystals of CaLnA10/sub 4/ by the Czochralski method at oxygen partial pressures of 10-/sup 5/ to 10-/sup 2/ Pa. The effect of oxygen partial pressure is due to the incongruent volatilization of oxides from CaLnA10/sub 4/ melts, with formation of defects dependent on the excess or deficiency of oxygen in the lattice. Cleavage, observed along the (100) plane, is associated with the cellular growth of CaLnA10/sub 4/ with concentrational supercooling.

  2. Dislocation structure of Ge crystals grown by low thermal gradient Czochralski technique

    NASA Astrophysics Data System (ADS)

    Trukhanov, E. M.; Fritzler, K. B.; Vasilenko, A. P.; Kolesnikov, A. V.; Kasimkin, P. V.; Moskovskih, V. A.

    2017-06-01

    Dislocation structure of the Ge single crystals grown by Czochralski method with low thermal gradient has been studied. The selective etching technique and the X-Ray transmission and reflection topography were used. Clearly defined non-uniform dislocation distribution over the crystal cross - section is revealed. Helical dislocations and sets of prismatic dislocation loops are registered. Helical dislocations perpendicular to the ingot axis are situated near the boundary between the regions with low and high dislocation densities (102 and 103 cm-2, respectively). Their length can be as much as several millimeters. Dislocation formations lying at a 35.3° to the crystal axis along <110> directions are also observed. These formations have the shape of prism confined by {111} planes.

  3. β-barium borate single crystal grown by a direct Czochralski method

    NASA Astrophysics Data System (ADS)

    Itoh, K.; Marumo, F.; Kuwano, Y.

    1990-12-01

    High purity single-crystal of β-BaB 2O 4 has been successfully grown from a BaB 2O 4 melt with the direct Czochralski method. The obtained crystal was confirmed to be that of the low-temperature β-phase by powder X-ray diffraction and the second harmonics generation. The growth rate was 0.6 mm/h, which is more than ten times as targe as that in the flux method. The growth direction was [001]. The present method requires to satisfy several important factors, such as choice of the starting material and temperature gradient at the growing point. The reason why a crystal of the low-temperature form is grown directly from a melt of the compound can be explained by the Ostwald step rule.

  4. Single crystal growth of Ga3Ni2 by the Czochralski method

    NASA Astrophysics Data System (ADS)

    Wencka, Magdalena; Pillaca, Mirtha; Gille, Peter

    2016-09-01

    Intermetallic compounds have proved to be interesting alternatives to heterogeneous catalysts prepared from pure noble metals or their alloys. As to study their intrinsic properties, to determine the crystalline structures of specific surfaces and finally to understand elementary processes of heterogeneous catalysis, single crystals of these intermetallics are needed. Inspired by the recent discovery of Ga-Ni catalysts for carbon dioxide reduction to methanol, we have grown for the first time cm3-size single crystals of trigonal Ga3Ni2. We report in detail on the synthesis and Czochralski growth from high-temperature solution using Ga as native solvent. Inclusion formation of Ga-rich fluid proved to be the most severe problem that was minimized by using an extremely low pulling rate down to 25 μm/h.

  5. Performance of silicon solar cells fabricated from multiple Czochralski ingots grown by using a single crucible

    NASA Technical Reports Server (NTRS)

    Kachare, A. H.; Uno, F. M.; Miyahira, T.; Lane, R. L.

    1980-01-01

    Results on the performance of solar cells fabricated on wafers from multiple silicon ingots of large diameter, grown by using a single crucible and a sequential melt replenishment Czochralski (CZO) technique are presented. Samples were analyzed for resistivity, dislocation density and impurity content. Solar cells were fabricated from the seed, center and tang end of each ingot to evaluate the growth reproducibility and material quality. The cell efficiency within a given wafer varies by no more than plus or minus 5% of the average value. A small but consistent decrease in the cell efficiency is observed from the first to the fourth ingot grown from a single crucible. This decrease may be related to an increase in impurity content or dislocation density or a combination of both. The efficiency of the cells fabricated from the tang end of the fourth ingot is about 10% lower than that of the control cell. An impurity effects model is employed to correlate this decrease in efficiency with the impurity build-up in the residual melt.

  6. Effect of tin doping on oxygen- and carbon-related defects in Czochralski silicon

    SciTech Connect

    Chroneos, A.; Londos, C. A.; Sgourou, E. N.

    2011-11-01

    Experimental and theoretical techniques are used to investigate the impact of tin doping on the formation and the thermal stability of oxygen- and carbon-related defects in electron-irradiated Czochralski silicon. The results verify previous reports that Sn doping reduces the formation of the VO defect and suppresses its conversion to the VO{sub 2} defect. Within experimental accuracy, a small delay in the growth of the VO{sub 2} defect is observed. Regarding carbon-related defects, it is determined that Sn doping leads to a reduction in the formation of the C{sub i}O{sub i}, C{sub i}C{sub s}, and C{sub i}O{sub i}(Si{sub I}) defects although an increase in their thermal stability is observed. The impact of strain induced in the lattice by the larger tin substitutional atoms, as well as their association with intrinsic defects and carbon impurities, can be considered as an explanation to account for the above observations. The density functional theory calculations are used to study the interaction of tin with lattice vacancies and oxygen- and carbon-related clusters. Both experimental and theoretical results demonstrate that tin co-doping is an efficient defect engineering strategy to suppress detrimental effects because of the presence of oxygen- and carbon-related defect clusters in devices.

  7. Continuous Czochralski Growth. Silicon Sheet Growth Development of the Large Area Silicon Sheet Task of the Low Cost Silicon Solar Array Project

    NASA Technical Reports Server (NTRS)

    Merz, F.

    1978-01-01

    The JPL Continuous Czochralski Growth Facility is now essentially complete and is functional. In this reporting period, a silicon lump recharging device was designed, and a prototype was built which performed well in simulated recharge tests. The large chamber (designed to accommodate a 14-inch hot zone) was put into operation initially with the standard hot zone in order to compare performance with previous experience. Some modifications were made to the hot zones in the larger chamber due to considerably larger radiative heat losses. Several short (one-ingot) runs were performed and four continuous runs were attempted. The largest continuous run lasted 64 hours and produced 57 kilograms of ingot.

  8. Crystal front shape control by use of an additional heater in a Czochralski sapphire single crystal growth system

    NASA Astrophysics Data System (ADS)

    Hur, Min-Jae; Han, Xue-Feng; Choi, Ho-Gil; Yi, Kyung-Woo

    2017-09-01

    The quality of sapphire single crystals used as substrates for LED production is largely influenced by two defects: dislocation density and bubbles trapped in the crystal. In particular, the dislocation density has a higher value in sapphire grown by the Czochralski (CZ) method than by other methods. In the present study, we predict a decreased value for the convexity and thermal gradient at the crystal front (CF) through the use of an additional heater in an induction-heated CZ system. In addition, we develop a solute concentration model by which the location of bubble formation in CZ growth is calculated, and the results are compared with experimental results. We further calculate the location of bubble entrapment corresponding with the use of an additional heater. We find that sapphire crystal growth with an additional heater yields a decreased thermal gradient at the CF, together with decreased CF convexity, improved energy efficiency, and improvements in terms of bubble formation location.

  9. Coupled melt flow and thermal stress predictions for Czochralski crystal growth

    SciTech Connect

    Zou, Y.F.; Zhang, H.; Prasad, V.

    1995-12-31

    A coupled finite volume-finite element algorithm is developed to simulate the melt flows and predict the temperature distributions and thermal stresses in the Czochralski grown crystals. The computer model employs a multizone adaptive grid generation scheme together with curvilinear finite column discretization (MASTRAPP) to predict the transport phenomena associated with the crystal growth processes as well as the nonplanar melt/crystal interface shape and its dynamics (Zhang and Prasad, 1995a). The MASTRAPP has proven to be a robust and efficient scheme for the problems involving moving interfaces and free surfaces. Thermal stresses in the crystal are obtained by using a commercial finite element code, ALGOR, that uses the curvilinear mesh generated by the MASTRAPP. The numerical results show that the melt flows have a strong influence on thermal stresses in the crystal near the melt/crystal interface, and hence, melt convection must be included in the computer model for accurate stress predictions. The predicted stress phenomena agrees qualitatively with the report results.

  10. Interface shape in Czochralski grown crystals - Effect of conduction and radiation

    NASA Technical Reports Server (NTRS)

    Srivastava, R. K.; Ramachandran, P. A.; Dudukovic, M. P.

    1985-01-01

    A sequential modular computational scheme has been proposed for the calculation of temperature profiles in the melt and crystal including the melt-crystal interface shape and the crystal pulling rate for a fixed crystal radius. The heat transfer in the melt is assumed to occur by conduction only. The shape of melt-gas meniscus, described by Laplace-Young equation, is incorporated in the model and its effects on interface shape and pulling rate are examined. Further, the model incorporates the detailed radiation interaction among the various surfaces in the puller using the Gebhart enclosure theory which accounts for both direct and reflected radiation. The effects of various process parameters on the interface shape and the pulling rate have been investigated. The results of this study indicate that the shape of the melt-gas meniscus has a significant effect on the pulling rate and the interface shape in conformity with earlier studies. Further, it is shown that a simple radiation model (Stefan's model) is inadequate to model the radiation heat exchange in the Czochralski puller apparatus and the detailed Gebhart analysis is necessary for accurate calculation of both the temperature profile in the crystal as well as the interface shape.

  11. Interface shape in Czochralski grown crystals - Effect of conduction and radiation

    NASA Technical Reports Server (NTRS)

    Srivastava, R. K.; Ramachandran, P. A.; Dudukovic, M. P.

    1985-01-01

    A sequential modular computational scheme has been proposed for the calculation of temperature profiles in the melt and crystal including the melt-crystal interface shape and the crystal pulling rate for a fixed crystal radius. The heat transfer in the melt is assumed to occur by conduction only. The shape of melt-gas meniscus, described by Laplace-Young equation, is incorporated in the model and its effects on interface shape and pulling rate are examined. Further, the model incorporates the detailed radiation interaction among the various surfaces in the puller using the Gebhart enclosure theory which accounts for both direct and reflected radiation. The effects of various process parameters on the interface shape and the pulling rate have been investigated. The results of this study indicate that the shape of the melt-gas meniscus has a significant effect on the pulling rate and the interface shape in conformity with earlier studies. Further, it is shown that a simple radiation model (Stefan's model) is inadequate to model the radiation heat exchange in the Czochralski puller apparatus and the detailed Gebhart analysis is necessary for accurate calculation of both the temperature profile in the crystal as well as the interface shape.

  12. Radiative heat transfer in curved specular surfaces in Czochralski crystal growth furnace

    SciTech Connect

    Guo, Z.; Maruyama, Shigenao; Tsukada, Takao

    1997-11-07

    A numerical investigation of radiative heat transfer constructed by curved surfaces with specular and diffuse reflection components is carried out. The ray tracing method is adopted for the calculation of view factors, in which a new ray emission model is proposed. The second-degree radiation ring elements are introduced, which are of engineering importance and numerical efficiency. The accuracy of the method is analyzed and verified using a simple configuration. The present computation using the proposed ray emission model is in good agreement with the analytical solution. As a numerical example and engineering application, the effects of the specular reflection and the meniscus of the melt surface in Czochralski (CZ) crystal growth are investigated. A marked temperature decrease in the melt surface is found by introducing specular reflection and the meniscus. The combined effects of the specular reflection and the meniscus should be considered in precision heat transfer control of a CZ apparatus.

  13. Instability of the bouyancy driven convection in Si melts during Czochralski crystal growth

    NASA Astrophysics Data System (ADS)

    Mihelci, M.; Wingerath, K.

    1989-09-01

    In this paper we study conditions under which the bouyancy driven convection in Czochralski systems will be unstable. The variable parameters are: the crucible radius Rc, the crystal radius RD, the melt depth H, and the temperature difference between the crucible wall and the solid-liquid interface λ T, respectively. In order to initiate the instability of the flow we impose a small temperature disturbance over the axisymmetric temperature distribution at the crucible wall. 36 cases are simulated numerically in order to get enough material to make some inferences about this instability. It is shown that (1) the buoyancy driven flow is highly unstable for all nearly real growing conditions, (2) the instability of the flow depends on all varied parameters, but stronger on the melt depth than on the other parameters, and (3) the characteristics length L in the Grashof number (Gr) must be a function of the crystal radius ( RD), the crucible radius ( Rc), and the melt depth H. So far as we know, it is for the first time that such a numerical study has been done for a Czochralski system. Nevertheless, the similar problem relating to the large-scale circulations in the atmosphere exists in the meteorology. The laboratory counterpart of this problem is known as the "sloping" convection in a rotating fluid, which deals with the dependence of the type of the flow on rotation rate Ω in an annulus filled with a water-glycerol solution and subjected to a horizontal temperature gradient [see R. Hide and P.J. Mason, Advan. Phys. 24 (1975)].

  14. In-situ observation of impurity diffusion boundary layer in silicon Czochralski growth

    NASA Astrophysics Data System (ADS)

    Kakimoto, Koichi; Eguchi, Minoru; Watanabe, Hisao; Hibiya, Taketoshi

    1990-01-01

    In-situ observation of the impurity diffusion boundary layer during single crystal growth of indium-doped silicon was carried out by X-ray radiography. The difference in the transmitted X-ray image compared with molten silicon just beneath the crystal-melt interface was attributed to the concentration of indium impurities having a larger absorption coefficient. The intensity profile of the transmitted X-ray can be reproduced by a transmittance calculation that considers the meniscus shape and impurity distribution. The impurity distribution profile near the crystal-melt interface was estimated using the Burton-Prim-Slichter (BPS) equation. The observed impurity diffusion boundary layer thickness was about 0.5 mm. It was found that the boundary layer thickness was not constant in the radial direction, which cannot be explained by the BPS theory, since it is based on a one-dimensional calculation.

  15. Crystallization of Silicon Ribbons

    NASA Technical Reports Server (NTRS)

    Leipold, M. H.

    1984-01-01

    Purity constraints for reasonable solar-cell efficiency require that silicon-ribbon growth for photovoltaics occur in a regime in which constitutional supercooling or other compositional effects on the crystallization front are not important. A major consideration in the fundamentals of crystallization is the removal of the latent heat of fusion. The direction of removal, compared with the growth direction, has a major influence on the crystallization rate and the development of localized stresses. The detailed shape of the crystallization front appears to have two forms: that required for dendritic-web growth, and that occurring in all others. After the removal of the latent heat of fusion, the thermal-mechanical behavior of all ribbons appears similar within the constraints of the exothermal gradient. The technological constraints in achieving the required thermal and mechanical conditions vary widely among the growth processes.

  16. Investigation of stoichiometry of oxygen precipitates in Czochralski silicon wafers by means of EDX, EELS and FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kot, D.; Kissinger, G.; Schubert, M. A.; Klingsporn, M.; Huber, A.; Sattler, A.

    2016-11-01

    In this work, we used EDX, EELS and FTIR spectroscopy to investigate the stoichiometry of oxygen precipitates in Czochralski silicon wafers. The EDX analysis of a plate-like precipitate demonstrated that the composition of the precipitate is SiO1.93. This result was confirmed by EELS where the characteristic plasmon peak of SiO2 was observed. Additionally, the absorption band of plate-like precipitates at 1223 cm-1 was found in the FTIR spectrum measured at liquid helium temperature. It was demonstrated that this band can only be simulated by the dielectric constants of amorphous SiO2.

  17. Modeling the effect of crystal and crucible rotation on the interface shape in Czochralski growth of piezoelectric langatate crystals

    NASA Astrophysics Data System (ADS)

    Stelian, C.; Nehari, A.; Lasloudji, I.; Lebbou, K.; Dumortier, M.; Cabane, H.; Duffar, T.

    2017-10-01

    Single La3Ga5.5Ta0.5O14 (LGT) crystals have been grown by using the Czochralski technique with inductive heating. Some ingots exhibit imperfections such as cracks, dislocations and striations. Numerical modeling is applied to investigate the factors affecting the shape of the crystal-melt interface during the crystallization of ingots having 3 cm in diameter. It was found that the conical shape of the interface depends essentially on the internal radiative exchanges in the semi-transparent LGT crystal. Numerical results are compared to experimental visualization of the growth interface, showing a good agreement. The effect of the forced convection produced by the crystal and crucible rotation is numerically investigated at various rotation rates. Increasing the crystal rotation rate up to 50 rpm has a significant flattening effect on the interface shape. Applying only crucible rotation enhances the downward flow underneath the crystal, leading to an increased interface curvature. Counter rotation between the crystal and the crucible results in a distorted shape of the interface.

  18. Measurement of flow phenomena using the ultrasonic velocity profile method in a simulated Czochralski crystal puller

    NASA Astrophysics Data System (ADS)

    Tokuhiro, Akira; Takeda, Yasushi

    1993-06-01

    An experimental investigation of flow phenomena in a simulated Czochralski (CZ) crystal puller was conducted using an ultrasound velocity profile (UVP) probe to measure fluid velocities. To isolate the various forces that influence the fluid motion, only the crystal was rotated and a water-glycerol mixture was used as the test fluid in this experiment. Measurements of the velocity components, V z and V r, under the initial transient from zero rotation to a set rotation rate as well as under steady-state conditions were made. The corresponding Reynolds number based on the crystal radius and rotation varied from Re Ω, x ≈ 660-5000 (Ω x ≈ 110-2000 rpm). The measured velocity profiles, V z and V r, were processed using a simple color image scheme based on the magnitude and direction of flow with respect to the probe. These profiles were studied to postulate flow patterns in the simulated CZ device. The measurements revealed three major regions of flow: (1) one beneath the crystal, (2) one near the free surface and crucible wall and (3) one beneath the crystal and occupying the extent of the crucible. In the initial transient, spatially symmetric outward flow beneath the crystal developed until the recirculating flow from below disturbed this pattern. At this point the apparent shear between the flow beneath the crystal and that circulating upwards from the bottom of the crucible induced flow instabilities and a non-axisymmetric flow pattern. The non-axisymmety was verified by the color-coded velocity profiles and a power spectrum analysis. The analysis revealed the critical Reynolds number for the onset of the primary instability to be Re Ωcrit ≈ 669. The linear variation in the power of the primary peak with the Reynolds number indicates that the onset of the axisymmetry-breaking instability is due to Hopf bifurcation.

  19. Dependence of nickel gettering on crystalline nature in as-grown Czochralski silicon wafer

    NASA Astrophysics Data System (ADS)

    Lee, In-Ji; Paik, Ungyu; Park, Jea-Gun

    2013-02-01

    The efficiency of nickel gettering in vacancy- and interstitial-silicon-dominant crystalline nature was studied using wafers cut along the axial direction of a CZ-grown silicon ingot grown with a variable v/G ratio. Six crystalline areas (V-rich, P-band, PV, PI, B-band, and I-rich) were present within one wafer. Nickel gettering efficiency was estimated before and after a typical NAND-flash-memory heat-treatment. With as-grown CZ silicon wafers, nickel gettering depends on the crystalline nature, i.e., nickel atoms are mainly gathered at oxygen precipitates in bulk at vacancy-dominant crystalline regions and at the surface of pure silicon in the interstitial-silicon-dominant crystal region (PI). Rapid thermal annealing of a CZ silicon wafer at 1175 °C for 10 s in Ar/NH3 mixture ambient completely erased the dependency of nickel gettering on the crystalline nature and demonstrated an excellent getting ability for nickel contamination via the relaxation gettering of oxygen precipitates.

  20. Three dimensional simulation of melt flow in Czochralski crystal growth with steady magnetic fields

    NASA Astrophysics Data System (ADS)

    Cen, Xianrong; Li, Y. S.; Zhan, Jiemin

    2012-02-01

    Three-dimensional transient numerical simulations were carried out to investigate the melt convection and temperature fluctuations within an industrial Czochralski crucible. To study the magnetic damping effects on the growth process, a vertical magnetic field and a cusp magnetic field were considered. Due to our special interest in the melt convection, only local simulation was conducted. The melt flow was calculated by large-eddy simulation (LES) and the magnetic forces were implemented in the CFD code by solving a set of user-defined scalar (UDS) functions. In the absence of magnetic fields, the numerical results show that the buoyant plumes rise from the crucible to the free surface and the crystal-melt interface, which indicates that the heat and mass transfer phenomena in Si melt can be characterized by the turbulent flow patterns. In the presence of a vertical magnetic field, the temperature fluctuations in the melt are significantly damped, with the buoyant plumes forming regular cylindrical geometries. The cusp magnetic field could also markedly reduce the temperature fluctuations, but the buoyant plumes would break into smaller vortical structures, which gather around the crystal as well as in the center of the crucible bottom. With the present crucible configurations, it is found that the vertical magnetic field with an intensity of 128 mT can damp the temperature fluctuations more effectively than the 40 mT cusp magnetic field, especially in the region near the growing crystal.

  1. Czochralski growth and characterization of MgAl2O4 single crystals

    NASA Astrophysics Data System (ADS)

    Bajor, Andrzej L.; Chmielewski, Marcin; Diduszko, Ryszard; Kisielewski, Jaroslaw; Lukasiewicz, Tadeusz; Orlinski, Krzysztof; Romaniec, Magdalena; Szyrski, Wlodzimierz

    2014-09-01

    MgAl2O4 (MALO) single crystals were pulled by the Czochralski method in [111] direction. The crystals were doped with Co (0.06-0.6 at% (charge compositions)), because Co2+ ions in tetrahedral positions exhibit non-linear optical properties, and, currently, Co:MALO seems to be the best saturable absorber in the eye-safe region (ca. 1.5 μm). By XRD powder technique a stoichiometric MALO was evidenced without admixtures of higher order spinels (MgAl4O7 and MgAl6O10). Also no excessive residual stresses have been discovered by different optical methods, and irrespective of the doping level we did not face any problem of cracking when cutting the crystals into wafers and other structures. In this work we have concentrated our efforts on investigation of thermal properties of MALO. Due to the 2nd order phase transition ca. 650 °C they seem to be of crucial importance in future thermal bonding of this material to the lasing host (Yb,Er-glass) expected just about this temperature.

  2. Reversible phase transition and relaxor behavior in Te2V2O9 single crystals grown by Czochralski technique

    NASA Astrophysics Data System (ADS)

    Shet, Tukaram; Varma, K. B. R.

    2016-09-01

    Te2V2O9 single crystals were grown along the polar c-axis via the Czochralski crystal growth technique. Dielectric studies carried out along the polar axis in a wide temperature range at different frequencies confirmed the relaxor nature of the Te2V2O9 single crystals. Temperature dependent polarized light optical microscopy along a-axis established a reversible phase transition around 614 K. Relaxor nature of Te2V2O9 was attributed to the compositional heterogeneity at micro/nano scale within the grown crystal as vanadium was observed to be present in different oxidation states by X-ray photoelectron spectroscopic studies.

  3. Maximization of Growth Rates During Czochralski Pulling

    NASA Technical Reports Server (NTRS)

    Wargo, M. J.

    1984-01-01

    It was suggested from theory(1-4) that silicon can be grown from the melt at rates far exceeding the current state of the art. Previous theoretical and experimental investigations which predict maximum rates of pulling during Czochralski growth are reviewed. Several experimental methods are proposed to modify the temperature distribution in a growing crystal to achieve higher rates of pulling. A physical model of a Czochralski crystal of germanium in contact with its melt was used to quantitatively determine, by direct measurement of the axial temperature distribution in the solid, the increase in axial temperature gradients effected by an inverted conical heat reflector located above the melt and coaxially about the physical model. Preliminary results indicate that this is an effective method of increasing the thermal resistance between the hot melt and crucible wall and a growing crystal. Under these conditions the enhancement of the interfacial temperature gradients permit a commensurate increase in the rate of crystal pulling.

  4. Maximization of growth rates during Czochralski pulling

    SciTech Connect

    Wargo, M.J.

    1984-04-01

    It was suggested from theory that silicon can be grown from the melt at rates far exceeding the current state of the art. Previous theoretical and experimental investigations which predict maximum rates of pulling during Czochralski growth are reviewed. Several experimental methods are proposed to modify the temperature distribution in a growing crystal to achieve higher rates of pulling. A physical model of a Czochralski crystal of germanium in contact with its melt was used to quantitatively determine, by direct measurement of the axial temperature distribution in the solid, the increase in axial temperature gradients effected by an inverted conical heat reflector located above the melt and coaxially about the physical model. Preliminary results indicate that this is an effective method of increasing the thermal resistance between the hot melt and crucible wall and a growing crystal. Under these conditions the enhancement of the interfacial temperature gradients permit a commensurate increase in the rate of crystal pulling.

  5. Photovoltaic Czochralski silicon manufacturing technology improvements. Annual subcontract report, 1 April 1993--31 March 1994

    SciTech Connect

    Jester, T.

    1995-03-01

    This report describes work performed under a 3-year, 3-phase, cost-share contract to demonstrate significant cost reductions and improvements in manufacturing technology. The objective of the program is to reduce costs in photovoltaic manufacturing by approximately 10% per year. The work was focused in three main areas: (1) silicon crystal growth and thin wafer technology; (2) silicon cell processing; and (3) silicon module fabrication and environmental, safety, and health issues. During this reporting period, several significant improvements were achieved. The crystal growing operation improved significantly with an increase in growth capacity due to larger crucibles, higher polysilicon packing density, and high pull speeds. Wafer processing with wire saws progressed rapidly, and the operation is completely converted to wire saw wafer processing. The wire saws yield almost 50% more wafers per inch in production, thus improving manufacturing volume by 50% without any additional expense in crystal growth. Cell processing improvements focused on better understanding the contact paste and firing processes. Module designs for lower material and labor costs began with the focus on a new junction box, larger modules with larger cells, and a less costly framing technique. In addition, chlorofluorocarbon (CFC) usage was completely eliminated in the Siemens manufacturing facility during this period, resulting in significant reductions in the cost of caustic waste treatment.

  6. Czochralski growth of tunable laser crystal BeAl(sub)2O(sub)4:Cr(sup)3+

    NASA Astrophysics Data System (ADS)

    Ma, X.; Hou, Y.; Wang, S.; Shen, Y.; Jin, Z.

    1986-03-01

    Optically homogeneous alexandrite blanks, 100 mm in length and 20 mm in diameter, were grown by Czochralski technique using RF heating. These blanks were fabricated into 90 mm long 5 mm diameter c-axis laser rods. Tunable laser output was obtained experimentally. Spectroscopic characteristics of the crystal were presented. Problems such as prevention of BeO contamination, chrysoberyl formation kinetics and melt aging are also discussed.

  7. Solar cells on low-resistivity boron-doped Czochralski-grown silicon with stabilized efficiencies of 20%

    NASA Astrophysics Data System (ADS)

    Lim, Bianca; Hermann, Sonja; Bothe, Karsten; Schmidt, Jan; Brendel, Rolf

    2008-10-01

    Recently, it was shown that the boron-oxygen complex responsible for the light-induced lifetime degradation in oxygen-rich boron-doped silicon can be permanently deactivated by illumination at elevated temperatures. Since the degradation is particularly harmful in low-resistivity Czochralski silicon (Cz-Si), we apply the deactivation procedure to a high-efficiency rear interdigitated single evaporation emitter wrap-through solar cell made on 1.4Ωcm B-doped Cz-Si. The energy conversion efficiency is thereby increased by more than 1% absolute compared to the degraded state to 20.3% on a designated area of 92cm2 and is furthermore shown to be stable under illumination at room temperature.

  8. Processing experiments on non-Czochralski silicon sheet (MEPSDU support contract). Quarterly technical report No. 1, 14 October 1980-31 December 1980

    SciTech Connect

    Pryor, R.

    1980-01-01

    A program of six months duration has been initiated to support and promote the further development of processing techniques which may be successfully and cost-effectively applied to low-cost non-Czochralski silicon sheet for solar cell fabrication. Work is proceeding and results are reported in the areas of process technology, cell design, cell metallization, and production cost simulation.

  9. Development of advanced Czochralski Growth Process to produce low cost 150 KG silicon ingots from a single crucible for technology readiness

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The goals in this program for advanced czochralski growth process to produce low cost 150 kg silicon ingots from a single crucible for technology readiness are outlined. To provide a modified CG2000 crystal power capable of pulling a minimum of five crystals, each of approximately 30 kg in weight, 150 mm diameter from a single crucible with periodic melt replenishment. Crystals to have: resistivity of 1 to 3 ohm cm, p-type; dislocation density below 1- to the 6th power per cm; orientation (100); after growth yield of greater than 90%. Growth throughput of greater than 2.5 kg per hour of machine operation using a radiation shield. Prototype equipment suitable for use as a production facility. The overall cost goal is $.70 per peak watt by 1986. To accomplish these goals, the modified CG2000 grower and development program includes: (1) increased automation with a microprocessor based control system; (2) sensors development which will increase the capability of the automatic controls system, and provide technology transfer of the developed systems.

  10. Capillary stability of vapor-liquid-solid crystallization processes and their comparison to Czochralski and Stepanov growth methods

    NASA Astrophysics Data System (ADS)

    Nebol'sin, Valery A.; Suyatin, Dmitry B.; Dunaev, Alexander I.; Tatarenkov, Alexander F.

    2017-04-01

    Epitaxial semiconductor nanowires grown with vapor-liquid-solid crystallization processes are very attractive nanoscale objects for many different applications. Despite extensive studies of the growth mechanism, there is still a lack of understanding of the growth process; in particular, the stability of the vapor-liquid-solid crystallization process has not previously been studied. Here we examine the capillary stability of the vapor-liquid-solid growth of nanowires and filamentary crystals with different diameters and demonstrate that the growth is stable for small Bond numbers when the meniscus height is linearly dependent on catalyst diameter. The capillary stability of vapor-liquid-solid growth is also compared with capillary stability in the Stepanov and Czochralski crystal growth methods; it is shown that capillary stability is not possible in the Czochralski method, although it is possible in the Stepanov growth method when the ratio of crystal diameter to shaper diameter is >1/2. These findings are important for better understanding and improved control of the growth of nanowires and filamentary crystals and indicate, for example, that large diameter filamentary crystals can be grown via a vapor-liquid-solid mechanism if the influence of gravity forces on the liquid catalytic particle shape can be reduced.

  11. Continuous replenishment of molten semiconductor in a Czochralski-process, single-crystal-growing furnace

    NASA Technical Reports Server (NTRS)

    Fiegl, George (Inventor); Torbet, Walter (Inventor)

    1981-01-01

    A replenishment crucible is mounted adjacent the usual drawing crucible, from which a monocrystalline boule is drawn according to the Czochralski method. A siphon tube for molten semiconductor transfer extends from the replenishment crucible to the drawing crucible. Each crucible is enclosed within its own hermetic shell and is provided with its own heater. The siphon tube is initially filled with molten semiconductor by raising the inert atmospheric pressure in the shell surrounding the replenishment crucible above that surrounding the drawing crucible. Thereafter, adjustment of the level of molten semiconductor in the drawing crucible may be achieved by adjusting the level in either crucible, since the siphon tube will establish the same level in both crucibles. For continuous processing, solid semiconductor may be added to and melted in the replenishment crucible during the process of drawing crystals from the drawing crucible. A constant liquid level of melted semiconductor is maintained in the system by an optical monitoring device and any of several electromechanical controls of the rate of replenishment or crucible height.

  12. The growth of ZnWO{sub 4} and CdWO{sub 4} single crystals from melt by the low thermal gradient Czochralski technique

    SciTech Connect

    Galashov, E. N.; Gusev, V. A.; Shlegel, V. N.; Vasiliev, Ya. V.

    2009-07-15

    The features of growth of single crystals of cadmium and zinc tungstates by the low thermal gradient Czochralski technique have been investigated. The effect of change in the growth conditions on the crystal morphology and the capture of macroinclusions is studied. Crystals 45 mm in diameter and up to 150 mm long (cylindrical part) are obtained. Their optical and scintillation characteristics are measured.

  13. Specific features of the formation of dislocation structure in gallium arsenide single crystals obtained by the Czochralski method

    NASA Astrophysics Data System (ADS)

    Parfenteva, I. B.; Pugachev, B. V.; Pavlov, V. F.; Kozlova, Yu. P.; Knyazev, C. N.; Yugova, T. G.

    2017-03-01

    The influence of the deviation of seed orientation from the [100] direction on the formation of a dislocation structure of gallium arsenide single crystals grown by the Czochralski method has been revealed. The intensive multiplication of dislocations and formation of a block structure occur at deviation by an angle of more than 3° in the region that is radially shifted to one of crystal sides. The linear density of dislocations in the walls changes from 1 × 104 cm-1 in low-angle boundaries to 6 × 104 cm-1 in subboundaries.

  14. X-ray topographic observations of magnetic domains in Czochralski-grown nickel single crystals in anomalous transmission geometry

    NASA Technical Reports Server (NTRS)

    Kuriyama, M.; Boettinger, W. J.; Burdette, H. E.

    1976-01-01

    The anomalous transmission effect has been observed in nickel single crystals grown by the Czochralski technique. Sample crystals prepared for X-ray topography are 1.5 to 2.5 cm in diameter and thicker than 0.4 mm; the product of the ordinary linear absorption coefficient and thickness ranges from 17 to 45 for Cu K-alpha radiation. Topographs taken with an asymmetric-crystal-topographic (ACT) camera have revealed extremely straight line images and rectangular arrangements of short line-segment images, along with the images of crystal imperfections. The line images change their arrangement upon application of magnetic fields. These images are attributed to magnetic domains in the interior of crystals. The formation of domain walls near the crystal surface is also observed and distinguished clearly from magnetic domains in the bulk with the use of the ACT camera.

  15. Growth of single crystal with a gradient of concentration of impurities by the Czochralski method using additional liquid charging

    NASA Astrophysics Data System (ADS)

    Galutskiy, V. V.; Vatlina, M. I.; Stroganova, E. V.

    2009-02-01

    Er- and Yb-doped congruent LiNbO 3 (CLN) single crystals and Cr 3+- and Mg 2+-doped stoichiometric LiNbO 3 (SLN) single crystals were grown by the Czochralski method using additional liquid charging. Changes in the absorption spectra of the transitions 2F 7/2→ 2F 5/2 in Yb 3+ ions and 4I 15/2→ 2H 11/2 in Er 3+ ions along the length of a single-crystal plate correlate with a specific gradient of concentration of Yb 3+ and Er 3+ ions in the crystal. The correlation of the absorption spectra of the optical centers of Cr 3+ ions in stoichiometric LiNbO 3 single crystals with the content of magnesium along the length of the crystal is reported.

  16. X-ray topographic observations of magnetic domains in Czochralski-grown nickel single crystals in anomalous transmission geometry

    NASA Technical Reports Server (NTRS)

    Kuriyama, M.; Boettinger, W. J.; Burdette, H. E.

    1976-01-01

    The anomalous transmission effect has been observed in nickel single crystals grown by the Czochralski technique. Sample crystals prepared for X-ray topography are 1.5 to 2.5 cm in diameter and thicker than 0.4 mm; the product of the ordinary linear absorption coefficient and thickness ranges from 17 to 45 for Cu K-alpha radiation. Topographs taken with an asymmetric-crystal-topographic (ACT) camera have revealed extremely straight line images and rectangular arrangements of short line-segment images, along with the images of crystal imperfections. The line images change their arrangement upon application of magnetic fields. These images are attributed to magnetic domains in the interior of crystals. The formation of domain walls near the crystal surface is also observed and distinguished clearly from magnetic domains in the bulk with the use of the ACT camera.

  17. Electromigration process for the purification of molten silicon during crystal growth

    DOEpatents

    Lovelace, Alan M. Administrator of the National Aeronautics and Space; Shlichta, Paul J.

    1982-01-01

    A process for the purification of molten materials during crystal growth by electromigration of impurities to localized dirty zones. The process has particular applications for silicon crystal growth according to Czochralski techniques and edge-defined film-fed growth (EFG) conditions. In the Czochralski crystal growing process, the impurities are electromigrated away from the crystallization interface by applying a direct electrical current to the molten silicon for electromigrating the charged impurities away from the crystal growth interface. In the EFG crystal growth process, a direct electrical current is applied between the two faces which are used in forming the molten silicon into a ribbon. The impurities are thereby migrated to one side only of the crystal ribbon. The impurities may be removed or left in place. If left in place, they will not adversely affect the ribbon when used in solar collectors. The migration of the impurity to one side only of the silicon ribbon is especially suitable for use with asymmetric dies which preferentially crystallize uncharged impurities along one side or face of the ribbon.

  18. Europium and potassium co-doped strontium metaborate single crystals grown by the Czochralski method

    NASA Astrophysics Data System (ADS)

    Głowacki, Michał; Solarz, Piotr; Ryba-Romanowski, Witold; Martín, Inocencio R.; Diduszko, Ryszard; Berkowski, Marek

    2017-01-01

    Strontium metaborate (SrB2O4) is a suitable material for use as a matrix for luminescent dopant ions. Similarity of ionic radii of strontium and divalent europium makes it an excellent host for Eu dopant. This paper reports on the Czochralski growth and spectroscopic study of SrB2O4 single crystals doped with europium and co-doped with europium and potassium. Based on recorded luminescence spectra it was found that both Eu3+ and Eu2+ ions occur in this host. Trivalent europium ions give rise to a narrow-band long-lived red luminescence that is not affected by incorporation of potassium ions. Divalent europium ions emit a UV-blue luminescence, consisting of a large spectral band centered at ca 430 nm. In the absence of potassium ions the decay of this luminescence deviates slightly from a single exponential time dependence with a mean lifetime value of 2.0 ns. In potassium-co-doped sample a strong deviation from a single exponential decay was observed for longer stages of decay, beginning at ca 2.5 ns. This phenomenon was attributed to dissimilarity of relaxation rates of a fraction of europium ions distributed in different lattice sites that are distorted by the presence of big potassium ions. By co-doping the host with alkali ions one can influence the oxidation state of europium ions thereby enhancing the emission of trivalent europium ions. It was concluded that the material under study is a promising phosphor for visible light emission applications.

  19. Continuous Czochralski growth: Silicon sheet growth development of the large area sheet task of the low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Johnson, C. M.

    1980-01-01

    The growth of 100 kg of silicon single crystal material, ten cm in diameter or greater, and 150 kg of silicon single crystal material 15 cm or greater utilizing one common silicon container material (one crucible) is investigated. A crystal grower that is recharged with a new supply of polysilicon material while still under vacuum and at temperatures above the melting point of silicon is developed. It accepts large polysilicon charges up to 30 kg, grows large crystal ingots (to 15 cm diameter and 25 kg in weight), and holds polysilicon material for recharging (rod or lump) while, at the same time, growing crystal ingots. Special equipment is designed to recharge polysilicon rods, recharge polysilicon lumps, and handle and store large, hot silicon crystal ingots. Many continuous crystal growth runs were performed lasting as long as 109 hours and producing as many as ten crystal ingots, 15 cm with weights progressing to 27 kg.

  20. Development of advanced Czochralski growth process to produce low cost 150 kg silicon ingots from a single crucible for technology readiness

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The design and development of an advanced Czochralski crystal grower are described. Several exhaust gas analysis system equipment specifications studied are discussed. Process control requirements were defined and design work began on the melt temperature, melt level, and continuous diameter control. Sensor development included assembly and testing of a bench prototype of a diameter scanner system.

  1. Continuous Czochralski growth: Silicon sheet growth development of the large area silicon sheet task of the Low Cost Silicon Solar Array project

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The primary objective of this contract is to develop equipment and methods for the economic production of single crystal ingot material by the continuous Czochralski (CZ) process. Continuous CZ is defined for the purpose of this work as the growth of at least 100 kilograms of ingot from only one melt container. During the reporting period (October, 1977 - September, 1978), a modified grower was made fully functional and several recharge runs were performed. The largest run lasted 44 hours and over 42 kg of ingot was produced. Little, if any, degradation in efficiency was observed as a result of pulling multiple crystals from one crucible. Solar efficiencies observed were between 9.3 and 10.4% AMO (13.0 and 14.6% AMI) compared to 10.5% (14.7% AMI) for optimum CZ material control samples. Using the SAMICS/IPEG format, economic analysis of continuous CZ suggests that 1986 DoE cost goals can only be met by the growth of large diameter, large mass crystals.

  2. Temperature and flow visualization in a simulation of the Czochralski process using temperature-sensitive liquid crystals.

    PubMed

    Aleksic, Jelena; Zielke, Paul; Szymczyk, Janusz A

    2002-10-01

    There is no doubt today that thermal and thermocapillary convection play a dominant role in momentum, heat, and mass transfer in the Czochralski crystal growth method. Because of the complexity of the problems, measurements in one point of the volume are not sufficient to illuminate the flow topography or to compare the experimental results with real or numerically simulated data. Therefore, it is of great interest to measure the temperatures and velocities in the whole field in order to qualitatively analyze thermally driven convection. The new experimental particle image thermometry method, based on computer-aided color analysis of the TLCs reported here, enables the simultaneous determination of the temperature and velocity fields.

  3. Semiempirical Model Would Control Czochralski Process

    NASA Technical Reports Server (NTRS)

    Dudukovic, M. P.; Ramachandran, P. A.; Srivastava, R. K.

    1989-01-01

    Semiempirical mathematical model proposed for control of growth of single crystals of silicon by Czochralski process. Expresses dependence of pulling rate and shape of liquid/solid interface upon important process variables; radius of growing crystal, temperature of crucible, level of melt, and height of exposed portion of crucible wall. Necessary to control shape of interface in manner consistent with other variables, to maintain radially uniform concentration of dopant, and reduce thermally induced stresses in vicinity of interface. Used to simulate complete growth cycles without requiring excessive computer time consumed by rigorous finite-element modeling.

  4. Crystal growth by Bridgman and Czochralski method of the ferromagnetic quantum critical material YbNi4P2

    NASA Astrophysics Data System (ADS)

    Kliemt, K.; Krellner, C.

    2016-09-01

    The tetragonal YbNi4P2 is one of the rare examples of compounds that allow the investigation of a ferromagnetic quantum critical point. We report in detail on two different methods which have been used to grow YbNi4P2 single crystals from a self-flux. The first, a modified Bridgman method, using a closed crucible system yields needle-shaped single crystals oriented along the [001]-direction. The second method, the Czochralski growth from a levitating melt, yields large single crystals which can be cut in any desired orientation. With this crucible-free method, samples without flux inclusions and a resistivity ratio at 1.8 K of RR1.8K = 17 have been grown.

  5. Oxygen-related vibrational modes produced in Czochralski silicon by hydrogen plasma exposure

    SciTech Connect

    Stein, H.J.; Medernach, J.W.

    1996-03-01

    Plasma hydrogenation of Czochralski Si has been performed to investigate the introduction of Si{endash}O stretch modes and their correlation with thermal donor formation. Plasma hydrogenation at 275{degree}C introduces a well-resolved vibrational absorption band at 1005 cm{sup {minus}1}, while absorption due to electronic excitations for thermal donors remains weak. We attribute this band to a Si{endash}O precursor center for thermal donor formation, and suggest it is the oxygen dimer center discussed in other studies of oxygen in Si. Vibrational modes introduced at 990 and 1000 cm{sup {minus}1} during post-hydrogenation furnace annealing at 400{degree}C correlate with thermal donors TD2 and TD3, respectively. Stretch frequencies for Si{endash}O in thermal donor centers are compared to those for oxygen aggregates in oxygen-implanted and electron-irradiated Si.

  6. Real time thermal imaging for analysis and control of crystal growth by the Czochralski technique

    NASA Technical Reports Server (NTRS)

    Wargo, M. J.; Witt, A. F.

    1992-01-01

    A real time thermal imaging system with temperature resolution better than +/- 0.5 C and spatial resolution of better than 0.5 mm has been developed. It has been applied to the analysis of melt surface thermal field distributions in both Czochralski and liquid encapsulated Czochralski growth configurations. The sensor can provide single/multiple point thermal information; a multi-pixel averaging algorithm has been developed which permits localized, low noise sensing and display of optical intensity variations at any location in the hot zone as a function of time. Temperature distributions are measured by extraction of data along a user selectable linear pixel array and are simultaneously displayed, as a graphic overlay, on the thermal image.

  7. Real time thermal imaging for analysis and control of crystal growth by the Czochralski technique

    NASA Technical Reports Server (NTRS)

    Wargo, M. J.; Witt, A. F.

    1992-01-01

    A real time thermal imaging system with temperature resolution better than +/- 0.5 C and spatial resolution of better than 0.5 mm has been developed. It has been applied to the analysis of melt surface thermal field distributions in both Czochralski and liquid encapsulated Czochralski growth configurations. The sensor can provide single/multiple point thermal information; a multi-pixel averaging algorithm has been developed which permits localized, low noise sensing and display of optical intensity variations at any location in the hot zone as a function of time. Temperature distributions are measured by extraction of data along a user selectable linear pixel array and are simultaneously displayed, as a graphic overlay, on the thermal image.

  8. Electrically active light-element complexes in silicon crystals grown by cast method

    NASA Astrophysics Data System (ADS)

    Sato, Kuniyuki; Ogura, Atsushi; Ono, Haruhiko

    2016-09-01

    Electrically active light-element complexes called thermal donors and shallow thermal donors in silicon crystals grown by the cast method were studied by low-temperature far-infrared absorption spectroscopy. The relationship between these complexes and either crystal defects or light-element impurities was investigated by comparing different types of silicon crystals, that is, conventional cast-grown multicrystalline Si, seed-cast monolike-Si, and Czochralski-grown Si. The dependence of thermal and the shallow thermal donors on the light-element impurity concentration and their annealing behaviors were examined to compare the crystals. It was found that crystal defects such as dislocations and grain boundaries did not affect the formation of thermal or shallow thermal donors. The formation of these complexes was dominantly affected by the concentration of light-element impurities, O and C, independent of the existence of crystal defects.

  9. Investigating the effect of carbon on oxygen behavior in n-type Czochralski silicon for PV application

    NASA Astrophysics Data System (ADS)

    Zhang, Song; Juel, Mari; Øvrelid, Eivind Johannes; Tranell, Gabriella

    2015-02-01

    The objective of the current work was to understand the effect of carbon as an impurity in silicon in terms of the formation of as-grown oxygen defects and the subsequent behavior of these defects in n-type Czochralski (Cz) silicon during heat treatment. Three n-type Cz ingots with different carbon levels were used in the investigation. Copper decoration was used to quantify the number of as-grown defects, while a two-step oxidation process (4 h at 750 °C and 16h at 1050 °C) was used to study the evolution of as-grown defects, that is, the formation and morphology of oxygen precipitates (stacking faults and smaller precipitates) in the silicon during heat treatment. Carrier Density Imaging (CDI) revealed the defect distribution and distinguished their states. Results from the study show that substitutional carbon enhances the etch pit density on the copper decorated samples; indicating an enhanced concentration of defects when the carbon level in the material increases. The higher number density but smaller size as-grown oxygen defects is concluded to be induced by the presence of substitutional carbon, given the oxygen precipitate formation pattern and morphology. Vacancies introduced by carbon did not, however, affect the density of voids significantly and we hence conclude that vacancies were largely consumed by the formation of oxygen complexes, as illustrated by the presence of a higher number density of as-grown oxygen defects in samples with a high carbon concentration. The highest effective minority carrier lifetime of as-grown wafers after amorphous-Si (a-Si) passivation was found on the sample with the highest carbon concentration, and the lifetime in the all samples showed stronger dependence on the oxygen concentration than on the carbon content.

  10. Czochralski growth of LaPd2Al2 single crystals

    NASA Astrophysics Data System (ADS)

    Doležal, P.; Rudajevová, A.; Vlášková, K.; Kriegner, D.; Václavová, K.; Prchal, J.; Javorský, P.

    2017-10-01

    The present study is focused on the preparation of single crystalline LaPd2Al2 by the Czochralski method. Differential scanning calorimetry (DSC) and energy dispersive X-ray spectroscopy (EDX) analyses reveal that LaPd2Al2 is an incongruently melting phase which causes difficulties for the preparation of single crystalline LaPd2Al2 by the Czochralski method. Therefore several non-stoichiometric polycrystalline samples were studied for its preparation. Finally the successful growth of LaPd2Al2 without foreign phases has been achieved by using a non-stoichiometric precursor with atomic composition 22:39:39 (La:Pd:Al). X-ray powder diffraction, EDX analysis and DSC were used for the characterisation. A single crystalline sample was separated from the ingot prepared by the Czochralski method using the non-stoichiometric precursor. The presented procedure for the preparation of pure single phase LaPd2Al2 could be modified for other incongruently melting phases.

  11. LGT (La3Ga5.5Ta0.5O14) langatate bulk crystal grown from the melt by Czochralski technique and characterization

    NASA Astrophysics Data System (ADS)

    Boutahraoui, B.; Nehari, A.; Boy, J.; Vacheret, X.; Allani, M.; Cabane, H.; Dumortier, M.; Derbal, M.; Lebbou, K.

    2017-03-01

    La3Ga5,5Ta0,5O14 (LGT) langatate crystals were grown along Z-axis by Czochralski technique in argon and mixed argon with 0.1%O2 atmosphere. The coloration and the performance of langatate crystals were strongly connected to the starting chemical composition, the gas atmosphere and the growth parameters. Any deviation from the optimal LGT generate macroscopic defects such cracks and grains boundary causing a deterioration of the crystals performance.

  12. Internal Stress Distribution Estimation in Liquid-Encapsulated Czochralski Grown GaAs Single Crystals Using Measured Temperature on Dummy Crystals

    NASA Astrophysics Data System (ADS)

    Nishio, Johji; Yasunaga, Toshio; Nakata, Yuhji

    1993-02-01

    The surface temperature on BN dummy crystals was measured under the same conditions as those for the actual liquid-encapsulated Czochralski (LEC) growth of GaAs single crystal. The solid-liquid interface shapes in the computation models were determined by the striations in the GaAs single crystal. Temperature and stress distributions inside the crystals were analyzed by the finite element method (FEM) using these data as the boundary conditions. By comparing the temperature distribution and the stress distribution, we have concluded that the reason for the high dislocation density in the crystal periphery is different from that in the center region, i.e., a kink in the axial temperature gradient versus the nature of the radial temperature gradient (solid-liquid interface shape is not flat), respectively.

  13. Oxide Control for Silicon Crystal Growth

    NASA Technical Reports Server (NTRS)

    Wehrli, H. A. I.

    1982-01-01

    Web dendrite growth process pulls sheet of newly crystallized silicon from molten silicon. Jets of argon pull outside gas into melt cavity, preventing silicon oxide from passing through heat-shield hold and depositing on it. Generated by aspirators, reversed flow is used in web dendrite process, which produces sheets of single-crystal silicon for low-cost solar cells.

  14. Transformation of divacancies to divacancy-oxygen pairs in p-type Czochralski-silicon; mechanism of divacancy diffusion

    SciTech Connect

    Ganagona, N. Vines, L.; Monakhov, E. V.; Svensson, B. G.

    2014-01-21

    In this work, a comprehensive study on the transition of divacancy (V{sub 2}) to divacancy-oxygen (V{sub 2}O) pairs in p-type silicon has been performed with deep level transient spectroscopy (DLTS). Czochralski grown, boron doped p-type, silicon samples, with a doping concentration of 2 × 10{sup 15} cm{sup −3} and oxygen content of 7.0 ± 1.5 × 10{sup 17} cm{sup −3}, have been irradiated with 1.8 MeV protons. Isothermal annealing at temperatures in the range of 200 °C–300 °C shows a close to one-to-one correlation between the loss in the donor state of V{sub 2} and the formation of the donor state of V{sub 2}O, located at 0.23 eV above the valence band edge. A concurrent transition takes place between the single acceptor states of V{sub 2} and V{sub 2}O, as unveiled by injection of electrons through optical excitation during the trap filling sequence of the DLTS measurements. Applying the theory for diffusion limited reactions, the diffusivity of V{sub 2} in the studied p-type samples is determined to be (1.5 ± 0.7) × 10{sup −3}exp[−(1.31 ± 0.03) eV/kT] cm{sup 2}/s, and this represents the neutral charge state of V{sub 2}. Further, the data seem to favor a two-stage diffusion mechanism involving partial dissociation of V{sub 2}, although a one-stage process cannot be fully excluded.

  15. Effective distribution coefficient in magnetic Czochralski growth

    NASA Astrophysics Data System (ADS)

    Hurle, D. T. J.; Series, R. W.

    1985-10-01

    The analysis by Burton, Prim and Slichter (1953) of the dependence of the effective distribution coefficient (keff) on the growth and crystal rotation rates in Czochralski growth is extended to include the effect of an imposed steady axial magnetic field. The theory is based on the analysis of the hydromagnetic flow at a rotating disk due to Kakutani (1962). It is shown that keff approaches unity as the field increases. The likely effects of this on the growth of silicon and gallium arsenide are discussed.

  16. Effect of crucible and crystal rotations on the convexity and the thermal stress in large size sapphire crystals during Czochralski growth

    NASA Astrophysics Data System (ADS)

    Nguyen, Tran Phu; Hsieh, Yao-Te; Chen, Jyh-Chen; Hu, Chieh; Nguyen, Huy Bich

    2017-06-01

    In this study, the effect of the temperature and flow fields generated by the rotation of the crucible and the crystal on the convexity of a c-axis, large-diameter sapphire crystal during the Czochralski growth process is investigated numerically. The thermal stress distributions in different sizes of crystal are also considered. The computational results show that the convexity and the thermal stress of the crystal are strongly dependent on the crucible and crystal rotation rates. The counter rotation between the crucible and the crystal results in a flatter crystal-melt interface, compared to the case of no crucible rotation or crystal rotation. Maximum thermal stress occurs at the highest curvature of the crystal-melt interface which appears near the center of the growing crystal, and the value is directly proportional to the crystal's size. Moreover, there is a significant decrease in the von Mises stress for the crystal-melt interface with lower convexity due to a reduction in the temperature gradient in the radial direction along the interface. As the crystal length gets larger, the maximum von Mises stress rapidly reduces.

  17. Development of advanced methods for continuous Czochralski growth. Silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Wolfson, R. G.; Sibley, C. B.

    1978-01-01

    The three components required to modify the furnace for batch and continuous recharging with granular silicon were designed. The feasibility of extended growth cycles up to 40 hours long was demonstrated by a recharge simulation experiment; a 6 inch diameter crystal was pulled from a 20 kg charge, remelted, and pulled again for a total of four growth cycles, 59-1/8 inch of body length, and approximately 65 kg of calculated mass.

  18. Convective effects in float-zone and Czochralski melts

    NASA Technical Reports Server (NTRS)

    Neitzel, G. P.

    1986-01-01

    The hydrodynamics of crystal-growth melts is a relatively new research area. Numerical modeling of these processes is necessary. The work discussed herein is in two parts: numerical simulations of the flow in a Czochralski melt, and also of that in a float zone. In addition, for the float-zone case, energy stability theory will be used to determine stability bounds for the onset of oscillatory thermo-capillary flow. Convective effects in crystal-growth melts arise from a variety of mechanisms. Temperature gradients both in the direction of gravity and normal to it give rise to convection due to buoyancy effects. Rotation of the crucible and/or crystal causes a forced convection which may augment or oppose the buoyancy-driven flow. Finally, thermo-capillary forces (due to the variation of surface tension with temperature) drive surface motions which in turn generate convection in the bulk fluid. All of these mechanisms are present in either Czochralski or float-zone growth. The objective of the Czochralski modeling is to develop an accurate numerical simulation of the flow in a Czochralski silicon melt and to investigate the effects of various parameters on the flow properties. Like some earlier investigations, the intent is to simulate the effects of buoyancy, forced and thermo-capillary convection, including unsteady effects. Unlike earlier work, the aim is to include the effects of a variable free surface and freezing interface and, possibly incorporate nonaxisymmetric effects.

  19. Recent progress in oxide scintillation crystals development by low-thermal gradient Czochralski technique for particle physics experiments

    NASA Astrophysics Data System (ADS)

    Shlegel, V. N.; Borovlev, Yu. A.; Grigoriev, D. N.; Grigorieva, V. D.; Danevich, F. A.; Ivannikova, N. V.; Postupaeva, A. G.; Vasiliev, Ya. V.

    2017-08-01

    Modern particle physics experiments call for high performance scintillation detectors with unique properties: radiation-resistant in high energy and astrophysics, highly radiopure, containing certain elements or enriched isotopes in astroparticle physics. The low-thermal gradient Czochralski (LTG CZ) crystal growth technique provides excellent quality large volume radiopure crystal scintillators. Absence of thermoelastic stress in the crystal and overheating of the melt in the LTG CZ method is particularly significant in production of crystalline materials with strong thermal anisotropic properties and low mechanical strength, with a very high yield of crystalline boules and low losses of initial charge, crucially important in production of crystal scintillators from enriched isotopes for double beta decay experiments. Here we discuss progress in development of the well known scintillators (Bi4Ge3O12 (BGO), CdWO4, ZnWO4, CaMoO4, PbMoO4), as well as R&D of new materials (ZnMoO4, Li2MoO4, Na2Mo2O7) for the next generation experiments in particle physics.

  20. Correlation between steady-oscillatory flow transition and the interface inversion process during the Czochralski growth of semitransparent oxide crystal

    NASA Astrophysics Data System (ADS)

    Faiez, Reza; Rezaei, Yazdan

    2016-12-01

    In this paper, steady-oscillatory transition of the convective flow in a Czochralski (Cz) growth system was numerically studied. In this configuration, rapid variations in density across narrow region of the flow in the vicinity of the crystallization front leads to an unstable stratification of the flow in this region. Time-dependent, finite volume method calculation of the momentum and heat transport equations shows that an instability mechanism, giving rise to the formation of cold plumes beneath the phase boundary, might be associated with an irreversible change in the convexity of the front. Dynamics of the crystallization front was found to be correlated with the periodic oscillation of the flow. It was shown that the interface inversion process occurs at a critical Reynolds number significantly (˜25%) lower than that predicted by the steady-state Cz-oxide model analysis. Consistently, the time-averaged maximum value of stream function was found to be larger than its corresponding steady-state value. This indicates that the mechanism behind the oscillatory transition of the flow has a positive feedback on the intensity of forced convection flow. These numerical results were attributed to the baroclinic instability mechanism characterized by oscillations of a cold plume appearing at the crystal periphery and descending along the symmetry axis. The time period of oscillations was found to be considerably (30-40%) decreases and, simultaneously, the inclination angle of isopycnals increases (˜48%) at a critical rotation rate of the crystal for which the interface inversion occurs.

  1. Numerical simulation of convection and heat transfer in Czochralski crystal growth by multiple-relaxation-time LBM

    NASA Astrophysics Data System (ADS)

    Liu, Ding; Huang, Weichao; Zhang, Ni

    2017-07-01

    A two-dimensional axisymmetric swirling model based on the lattice Boltzmann method (LBM) in a pseudo Cartesian coordinate system is posited to simulate Czochralski (Cz) crystal growth in this paper. Specifically, the multiple-relaxation-time LBM (MRT-LBM) combined with the finite difference method (FDM) is used to analyze the melt convection and heat transfer in the process of Cz crystal growth. An incompressible axisymmetric swirling MRT-LB D2Q9 model is applied to solve for the axial and radial velocities by inserting thermal buoyancy and rotational inertial force into the two-dimensional lattice Boltzmann equation. In addition, the melt temperature and the azimuthal velocity are solved by MRT-LB D2Q5 models, and the crystal temperature is solved by FDM. The comparison results of stream functions values of different methods demonstrate that our hybrid model can be used to simulate the fluid-thermal coupling in the axisymmetric swirling model correctly and effectively. Furthermore, numerical simulations of melt convection and heat transfer are conducted under the conditions of high Grashof (Gr) numbers, within the range of 105 ˜ 107, and different high Reynolds (Re) numbers. The experimental results show our hybrid model can obtain the exact solution of complex crystal-growth models and analyze the fluid-thermal coupling effectively under the combined action of natural convection and forced convection.

  2. Competitive gettering of copper in Czochralski silicon by implantation-induced cavities and internal gettering sites

    SciTech Connect

    McHugo, S.A.; Weber, E.R.; Myers, S.M.; Petersen, G.A.

    1996-11-01

    The effectiveness of copper gettering by implantation-induced cavities in competition with internal gettering sites in silicon was demonstrated. The cavities were formed in the near surface region by He implantation and annealing while the internal gettering sites were created in the material{close_quote}s bulk by a ramped hi{endash}lo{endash}hi oxygen precipitation heat treatment. Ion implantation was used to controllably introduce the copper. The quantity of implanted copper was below that corresponding to saturation of solution throughout the wafer at the gettering temperatures of 700 and 800{degree}C. The cavities were found to be an effective gettering site in the presence of internal gettering sites with only a small amount of copper being gettered at the internal gettering sites. These results have important implications for optimal gettering of metallic impurities from integrated circuit device regions. {copyright} {ital 1996 American Institute of Physics.}

  3. Sensitivity enhanced FTIR investigation of defects introduced by RTA pre-treatment in Czochralski silicon wafers

    NASA Astrophysics Data System (ADS)

    Kot, Dawid; Kissinger, Gudrun; Sattler, Andreas

    2017-10-01

    The investigation of vacancy oxygen complexes in silicon wafers by FTIR is not easy because their concentration is close to the detection limit. In order to enhance the sensitivity of the FTIR measurement we investigated stacked samples of about 1 cm thickness at temperature close to liquid helium temperature. This method was applied to study the absorption bands of defects in as-grown silicon wafers, rapid thermal annealing (RTA) pre-treated wafers, and in RTA pre-treated wafers with subsequent anneals at 800 °C for short periods. We found that the RTA pre-treatment at 1250 °C could not fully annihilate the thermal double donors which were present in the as-grown wafer. By RTA at 1100 °C annihilation was possible. In the wafer pre-treated by RTA at 1250 °C we found the absorption bands of VO4 at 985 cm‑1 and 991 cm‑1 in the measurements carried out at room temperature and at 6 K, respectively. In this wafer we also detected an unknown band at 1030 cm‑1. The VO4 band and the unknown band at 1030 cm‑1 disappeared immediately after annealing at 800 °C for 10 min. Instead, the bands at 1096 and 1099 cm‑1, both assigned to VO5,6, appeared. These bands are already present in the as-grown sample but their absorption coefficient decreases during RTA at 1100 °C. In samples annealed at 800 °C for 30 min or longer a new absorption band at 1053 cm‑1 appears which can be also assigned to VO5,6 complexes.

  4. Czochralski growth of Gd3(Al5-xGax)O12 (GAGG) single crystals and their scintillation properties

    NASA Astrophysics Data System (ADS)

    Kurosawa, Shunsuke; Shoji, Yasuhiro; Yokota, Yuui; Kamada, Kei; Chani, Valery I.; Yoshikawa, Akira

    2014-05-01

    Ce:Gd3(AlxGa1-x)5O12 (x=2.5/5 and 3/5, Ce:GAGG-2.5 and Ce:GAGG-3) crystals were grown by the Czochralski process in order to reduce cost of the starting materials as compared with conventional Ce:Gd3Al2Ga3O12 (Ce:GAGG-2) crystal which have high light output. Although perovskite phase was detected in Ce:GAGG-3, Ce:GAGG-2.5 had single-phase garnet structure. Solidification fraction for the Ce:GAGG-2.5 growth was 0.52. Optical properties including transmittance, emission, and excitation spectra of 30 samples cut from the Ce:GAGG-2.5 bulk ingot did not depend on their original position along the growth axis. These samples had light outputs of approximately 58,000±3000 photons/MeV. However, scintillation decay times varied from 140 to 200 ns and depended on the position clearly.

  5. Formation kinetics and mechanism of metastable vacancy-dioxygen complex in neutron irradiated Czochralski silicon

    NASA Astrophysics Data System (ADS)

    Dong, Peng; Wang, Rong; Yu, Xuegong; Chen, Lin; Ma, Xiangyang; Yang, Deren

    2017-07-01

    We have quantitatively investigated the formation kinetics of metastable vacancy-dioxygen (VO2) complex in a structure of [VO + Oi], where a VO complex is trapped in a next-neighbor position to an interstitial oxygen atom (Oi). It is found that the VO annihilation is accompanied by the generation of metastable [VO + Oi] complex during annealing in the temperature range of 220-250 °C. The activation energy for [VO + Oi] generation appears at around 0.48 eV, which is much lower than the counterpart of stable VO2 complex. This indicates that the formation of [VO + Oi] complex originates from the reaction between VO and Oi. The ab initio calculations show that the formation energy of [VO + Oi] complex is larger than that of VO2 complex, which means that [VO + Oi] complex is thermodynamically unfavorable as compared to VO2 complex. However, the binding energy of [VO + Oi] complex is positive, indicating that [VO + Oi] complex is stable against decomposition of VO and Oi in silicon. It is believed that [VO + Oi] complex serves as the intermediate for VO to VO2 conversion.

  6. Economic analysis of low cost silicon sheet produced from Czochralski grown material

    NASA Technical Reports Server (NTRS)

    Koliwad, K. M.; Leipold, M. H.; Cumming, G. D.; Digges, T. G., Jr.

    1976-01-01

    This study shows that the lower limits for manufacturing add-on costs to convert polysilicon to wafers is in the range of $22 to $26/sq m with the cost about equally divided between the crystal growth and wafering processes. However, the $22 to $26/sq m cost limit should be viewed as an asymptote since it is based on multicharge or continuous growth configurations, solidification rates in excess of 2 Kg/hr, multiblade wafering and a slice plus kerf of .045 cm. It should also be emphasized that the results of this study are based on as-sawn wafers, 100% yields (growth and slicing) and no profit. To the first approximation, the limiting cost factors are crucible material and furnace parts for growth and blade material and slurry for slicing.

  7. Characterization of YbNi4(P1-xAsx)2, x = 0, 0.2 single crystals grown by Czochralski method

    NASA Astrophysics Data System (ADS)

    Kliemt, K.; Krellner, C.

    2017-04-01

    We have investigated large single crystals of YbNi4P2 that were grown from a levitating melt by the Czochralski method. The new samples facilitate the determination of the absolute values of the electrical resistivity. Phase pure polycrystalline samples of the non-magnetic reference LuNi4P2 were prepared and the electrical resistivity was measured. Furthermore we have grown a single crystal of the As substituted compound YbNi4(P1-xAsx)2, x = 0.2 and investigated the homogenity of the As distribution.

  8. Low Thermal Gradient Czochralski growth of large CdWO4 crystals and electronic properties of (010) cleaved surface

    NASA Astrophysics Data System (ADS)

    Atuchin, V. V.; Galashov, E. N.; Khyzhun, O. Y.; Bekenev, V. L.; Pokrovsky, L. D.; Borovlev, Yu. A.; Zhdankov, V. N.

    2016-04-01

    The crystal growth of large high-quality inclusion-free CdWO4 crystals, 110 mm in diameter and mass up to 20 kg, has been carried out by the Low Thermal Gradient Czochralski (LTG Cz) technique. The high-purity CdWO4(010) surface has been prepared by cleavage and high structural quality of the surface has been verified by RHEED, revealing a system of Kikuchi lines. The chemical state and electronic structure of the surface have been studied using X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). The total and partial densities of states of the CdWO4 tungstate were calculated employing the first-principles full potential linearized augmented plane wave (FP-LAPW) method. The results indicate that the principal contributors to the valence band of CdWO4 are the Cd 4d, W 5d and O 2p states which contribute mainly at the bottom, in the central portion and at the top of the valence band, respectively, with also significant contributions of the mentioned states throughout the whole CdWO4 valence-band region. With respect to the occupation of the O 2p states, the results of the FP-LAPW calculations are confirmed by comparison on a common energy scale of the XPS valence-band spectrum and the XES band representing the energy distribution of the O 2p states in this compound. Additionally, the FP-LAPW data allow us to conclude that the CdWO4 tungstate is a non-direct semiconductor.

  9. Solar silicon via the Dow Corning process

    NASA Technical Reports Server (NTRS)

    Hunt, L. P.; Dosaj, V. D.

    1979-01-01

    Technical feasibility for high volume production of solar cell-grade silicon is investigated. The process consists of producing silicon from pure raw materials via the carbothermic reduction of quartz. This silicon was then purified to solar grade by impurity segregation during Czochralski crystal growth. Commercially available raw materials were used to produce 100 kg quantities of silicon during 60 hour periods in a direct arc reactor. This silicon produced single crystalline ingot, during a second Czochralski pull, that was fabricated into solar cells having efficiencies ranging from 8.2 percent to greater than 14 percent. An energy analysis of the entire process indicated a 5 month payback time.

  10. Precipitation of Cu and Ni in n- and p-type Czochralski-grown silicon characterized by photoluminescence imaging

    NASA Astrophysics Data System (ADS)

    Sun, Chang; Nguyen, Hieu T.; Rougieux, Fiacre E.; Macdonald, Daniel

    2017-02-01

    Photoluminescence (PL) images and micro-PL maps were taken on Cu- or Ni-doped monocrystalline silicon wafers, to investigate the distribution of the metal precipitates. Several n-type and p-type wafers were used in which Cu or Ni were introduced in the starting melt of the ingots and precipitated during the ingot cooling (as opposed to surface contamination). The micro-PL mapping allowed investigation of the metal precipitates with a higher spatial resolution. Markedly different precipitation patterns were observed in n- and p-type samples: in both Cu- and Ni-doped n-type samples, circular central regions and edge regions were observed. In these regions, particles were distributed randomly and homogeneously. In the p-type Cu-doped and Ni-doped samples, by contrast, the precipitates occurred in lines along <110> orientations. The difference in the precipitation behaviour in n- and p-type samples is conjectured to be caused by different concentrations of self-interstitials and vacancies remaining in the crystal during the ingot cooling: there are more vacancies in the n-type ingots but more interstitials in the p-type ingots. The dopant effects on the intrinsic point defect concentrations in silicon crystals and possible precipitation mechanisms are discussed based on the findings in this work and the literature.

  11. Continuous Czochralski growth. Development of advanced Czochralski growth process to produce low cost 150 kg silicon ingots from a single crucible for technology readiness

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The improvement of growth rates using radiation shielding and investigation of the crucible melt interaction for improved yields were emphasized. Growth runs were performed from both 15 and 16 inch diameter crucibles, producing 30 and 37 kg ingots respectively. Efforts to increase the growth rate of 150 mm diameter ingots were limited by temperature instabilities believed to be caused by undesirable thermal convections in the larger melts. The radiation shield improved the growth rate somewhat, but the thermal instability was still evident, leading to nonround ingots and loss of dislocation-free structure. A 38 kg crystal was grown to demonstrate the feasibility of producing 150 kg with four growth cycles. After the grower construction phase, the Hamco microprocessor control system was interfaced to the growth facility, including the sensor for automatic control of seeding temperature, and the sensor for automatic shouldering. Efforts focused upon optimization of the seeding, necking, and shoulder growth automation programs.

  12. Single-crystal silicon optical fiber by direct laser crystallization

    SciTech Connect

    Ji, Xiaoyu; Lei, Shiming; Yu, Shih -Ying; Cheng, Hiu Yan; Liu, Wenjun; Poilvert, Nicolas; Xiong, Yihuang; Dabo, Ismaila; Mohney, Suzanne E.; Badding, John V.; Gopalan, Venkatraman

    2016-12-05

    Semiconductor core optical fibers with a silica cladding are of great interest in nonlinear photonics and optoelectronics applications. Laser crystallization has been recently demonstrated for crystallizing amorphous silicon fibers into crystalline form. Here we explore the underlying mechanism by which long single-crystal silicon fibers, which are novel platforms for silicon photonics, can be achieved by this process. Using finite element modeling, we construct a laser processing diagram that reveals a parameter space within which single crystals can be grown. Utilizing this diagram, we illustrate the creation of single-crystal silicon core fibers by laser crystallizing amorphous silicon deposited inside silica capillary fibers by high-pressure chemical vapor deposition. The single-crystal fibers, up to 5.1 mm long, have a very welldefined core/cladding interface and a chemically pure silicon core that leads to very low optical losses down to ~0.47-1dB/cm at the standard telecommunication wavelength (1550 nm). Furthermore, tt also exhibits a photosensitivity that is comparable to bulk silicon. Creating such laser processing diagrams can provide a general framework for developing single-crystal fibers in other materials of technological importance.

  13. Single-crystal silicon optical fiber by direct laser crystallization

    DOE PAGES

    Ji, Xiaoyu; Lei, Shiming; Yu, Shih -Ying; ...

    2016-12-05

    Semiconductor core optical fibers with a silica cladding are of great interest in nonlinear photonics and optoelectronics applications. Laser crystallization has been recently demonstrated for crystallizing amorphous silicon fibers into crystalline form. Here we explore the underlying mechanism by which long single-crystal silicon fibers, which are novel platforms for silicon photonics, can be achieved by this process. Using finite element modeling, we construct a laser processing diagram that reveals a parameter space within which single crystals can be grown. Utilizing this diagram, we illustrate the creation of single-crystal silicon core fibers by laser crystallizing amorphous silicon deposited inside silica capillarymore » fibers by high-pressure chemical vapor deposition. The single-crystal fibers, up to 5.1 mm long, have a very welldefined core/cladding interface and a chemically pure silicon core that leads to very low optical losses down to ~0.47-1dB/cm at the standard telecommunication wavelength (1550 nm). Furthermore, tt also exhibits a photosensitivity that is comparable to bulk silicon. Creating such laser processing diagrams can provide a general framework for developing single-crystal fibers in other materials of technological importance.« less

  14. Low Thermal Gradient Czochralski growth of large CdWO{sub 4} crystals and electronic properties of (010) cleaved surface

    SciTech Connect

    Atuchin, V.V.; Galashov, E.N.; Khyzhun, O.Y.; Bekenev, V.L.; Pokrovsky, L.D.; Borovlev, Yu.A.; Zhdankov, V.N.

    2016-04-15

    The crystal growth of large high-quality inclusion-free CdWO4 crystals, 110 mm in diameter and mass up to 20 kg, has been carried out by the Low Thermal Gradient Czochralski (LTG Cz) technique. The high-purity CdWO{sub 4}(010) surface has been prepared by cleavage and high structural quality of the surface has been verified by RHEED, revealing a system of Kikuchi lines. The chemical state and electronic structure of the surface have been studied using X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). The total and partial densities of states of the CdWO{sub 4} tungstate were calculated employing the first-principles full potential linearized augmented plane wave (FP-LAPW) method. The results indicate that the principal contributors to the valence band of CdWO{sub 4} are the Cd 4d, W 5d and O 2p states which contribute mainly at the bottom, in the central portion and at the top of the valence band, respectively, with also significant contributions of the mentioned states throughout the whole CdWO{sub 4} valence-band region. With respect to the occupation of the O 2p states, the results of the FP-LAPW calculations are confirmed by comparison on a common energy scale of the XPS valence-band spectrum and the XES band representing the energy distribution of the O 2p states in this compound. Additionally, the FP-LAPW data allow us to conclude that the CdWO{sub 4} tungstate is a non-direct semiconductor. - Highlights: • Large high-quality CdWO{sub 4} crystals, up to 115 mm in diameter and mass up to 20 kg, have been grown. • The high-purity cleaved CdWO{sub 4}(010) surface has been studied by the XPS and XES methods. • The principal contributors to the CdWO{sub 4} valence band are the Cd 4d, W 5d and O 2p states.

  15. Numerical simulation of melt convection in Czochralski growth

    SciTech Connect

    Rajaram, S.

    1987-01-01

    The temperature distribution and fluid flow in the crucible for growth of silicon crystals by the Czochralski process are obtained by simultaneously solving the Navier-Stokes equations and the energy equation numerically using finite differences. Probable flows are outlined for combinations of forced convection due to crystal rotation and natural convection due to imposed temperature gradients. Crystal rotation appears to be effective in isolating the crystal growth interface from the deleterious effects of buoyant convective flow. Crucible rotation counter to crystal rotation suppresses forced convection due to crystal rotation and imparts rotational velocity to a large portion of the melt. An increase in the aspect ratio of the melt (ratio of melt depth to crucible radius ) reduces thermal convection while thermal radiation losses from the free surface of the melt enhances it.

  16. Processing of n+/p-/p+ strip detectors with atomic layer deposition (ALD) grown Al2O3 field insulator on magnetic Czochralski silicon (MCz-si) substrates

    NASA Astrophysics Data System (ADS)

    Härkönen, J.; Tuovinen, E.; Luukka, P.; Gädda, A.; Mäenpää, T.; Tuominen, E.; Arsenovich, T.; Junkes, A.; Wu, X.; Li, Z.

    2016-08-01

    Detectors manufactured on p-type silicon material are known to have significant advantages in very harsh radiation environment over n-type detectors, traditionally used in High Energy Physics experiments for particle tracking. In p-type (n+ segmentation on p substrate) position-sensitive strip detectors, however, the fixed oxide charge in the silicon dioxide is positive and, thus, causes electron accumulation at the Si/SiO2 interface. As a result, unless appropriate interstrip isolation is applied, the n-type strips are short-circuited. Widely adopted methods to terminate surface electron accumulation are segmented p-stop or p-spray field implantations. A different approach to overcome the near-surface electron accumulation at the interface of silicon dioxide and p-type silicon is to deposit a thin film field insulator with negative oxide charge. We have processed silicon strip detectors on p-type Magnetic Czochralski silicon (MCz-Si) substrates with aluminum oxide (Al2O3) thin film insulator, grown with Atomic Layer Deposition (ALD) method. The electrical characterization by current-voltage and capacitance-voltage measurement shows reliable performance of the aluminum oxide. The final proof of concept was obtained at the test beam with 200 GeV/c muons. For the non-irradiated detector the charge collection efficiency (CCE) was nearly 100% with a signal-to-noise ratio (S/N) of about 40, whereas for the 2×1015 neq/cm2 proton irradiated detector the CCE was 35%, when the sensor was biased at 500 V. These results are comparable with the results from p-type detectors with the p-spray and p-stop interstrip isolation techniques. In addition, interestingly, when the aluminum oxide was irradiated with Co-60 gamma-rays, an accumulation of negative fixed oxide charge in the oxide was observed.

  17. Model-predictive control of the Czochralski crystallization process. Part II. Reduced-order convection model

    NASA Astrophysics Data System (ADS)

    Irizarry-Rivera, Roberto; Seider, Warren D.

    1997-07-01

    A new reduced-order model (ROM) is proposed for the bulk-controller presented in Part I. This model considers convection in the melt based upon the assumption of an idealized flow geometry consisting of horizontal donuts and vertical tubes with radial and axial dispersion, respectively. Boundary and bulk layers are assumed to separate the core fluid from the crystal and crucible. Scale analysis and integral boundary-layer theory are utilized to estimate the boundary-layer thicknesses and the maximum stream function in the core fluid. A strategy is presented for adjusting the imperfect model online to reduce the process/model mismatch during MPC.

  18. Raman scattering study of Czochralski-grown yttrium flouride single crystals

    SciTech Connect

    Rotereau, K.; Gesland, J.Y.; Daniel, P.; Bulou, A. . Equipe de Physique de l'Etat Condense)

    1993-08-01

    Single crystals of yttrium fluoride YF[sub 3] have been grown by the Czokralski method and studied by Raman scattering in the temperature range 20 K - 730 K. The results are consistent with the prediction of the group theory analysis in the framework of the space group Pnma although two lines B2g are missing. There is no evidence for any structural phase transition in this temperature range. The structural relationship between the phase investigated and the high temperature phase (out of the temperature range studied) is discussed.

  19. Czochralski's creative mistake: a milestone on the way to the Gigabit Era.

    PubMed

    Evers, Jürgen; Klüfers, Peter; Staudigl, Rudolf; Stallhofer, Peter

    2003-12-01

    Much of the rapid change in industry, science, and society is brought about by the meteoric development of the microelectronics industry. Daily life is affected by this development; one has only to think of mobile telephones and the chips on modern credit cards. The raw material for microelectronics is the single crystal of silicon, with very high purity and almost perfect crystal structure. About 95% of the world's current production of silicon single crystals is achieved using the process that Jan Czochralski discovered in 1916. Today, single crystals of silicon can be grown that are up to 2 m long, 300 mm in diameter, and weigh up to 265 kg. The use of magnetic fields has led to significant advances in crystal-drawing technology. Intensive research and development reveals that in addition to the technology, which provides crystals of ever-increasing diameter, defect engineering, and the control of the numerous temperature-dependent reactions of crystal defects, are of paramount importance.

  20. Growth of silicon carbide crystals on a seed while pulling silicon crystals from a melt

    NASA Technical Reports Server (NTRS)

    Ciszek, T. F.; Schwuttke, G. H. (Inventor)

    1979-01-01

    A saturated solution of silicon and an element such as carbon having a segregation coefficient less than unity is formed by placing a solid piece of carbon in a body of molten silicon having a temperature differential decreasing toward the surface. A silicon carbide seed crystal is disposed on a holder beneath the surface of the molten silicon. As a rod or ribbon of silicon is slowly pulled from the melt, a supersaturated solution of carbon in silicon is formed in the vicinity of the seed crystal. Excess carbon is emitted from the solution in the form of silicon carbide which crystallizes on the seed crystal held in the cool region of the melt.

  1. High efficient 1.56 microm laser operation of Czochralski grown Er:Yb:Sr3Y2(BO3)4 crystal.

    PubMed

    Huang, Jianhua; Chen, Yujin; Lin, Yanfu; Gong, Xinghong; Luo, Zundu; Huang, Yidong

    2008-10-27

    An Er:Yb:Sr(3)Y(2)(BO(3))(4) crystal doped with 0.9 at.% Er(3+) and 18.6 at.% Yb(3+) ions was grown by the Czochralski method. End-pumped by diode laser at 970 nm in a hemispherical cavity, 1.3 W quasi-cw laser output around 1.56 microm was achieved in a 1.1-mm-thick Z-cut Er:Yb:Sr(3)Y(2)(BO(3))(4) crystal when the transmission of output coupler is 1.5%. The absorbed pump threshold and slop efficiency of the laser are 4.26 W and 20%, respectively. This crystal has flat and broad gain curve peaked around 1.56 microm, which shows that it is also a potential gain medium for tunable and short pulse lasers.

  2. Growth and characterization of indium doped silicon single crystals at industrial scale

    NASA Astrophysics Data System (ADS)

    Haringer, Stephan; Giannattasio, Armando; Alt, Hans Christian; Scala, Roberto

    2016-03-01

    Indium is becoming one of the most important dopant species for silicon crystals used in photovoltaics. In this work we have investigated the behavior of indium in silicon crystals grown by the Czochralski pulling process. The experiments were performed by growing 200 mm crystals, which is a standard diameter for large volume production, thus the data reported here are of technological interest for the large scale production of indium doped p-type silicon. The indium segregation coefficient and the evaporation rate from the silicon melt have been calculated to be 5 × 10-4 ± 3% and 1.6 × 10-4 cm·s-1, respectively. In contrast to previous works the indium was introduced in liquid phase and the efficiency was compared with that deduced by other authors, using different methods. In addition, the percentage of electrically active indium at different dopant concentrations is calculated and compared with the carrier concentration at room temperature, measured by four-point bulk method.

  3. Striations in CZ silicon crystals grown under various axial magnetic field strengths

    NASA Astrophysics Data System (ADS)

    Kim, K. M.; Smetana, P.

    1985-10-01

    Inhibition of fluid flow instabilities in the melt by the axial magnetic field in Czochralski silicon crystal growth (AMCZ) is investigated precisely by a high-sensitivity striation etch in conjunction with temperature measurements. The magnetic field strength (B) was varied up to 4.0 kG, incremented mostly in 0.5-kG/2.5-cm crystal length. The convection flow was substantially suppressed at B greater than or equal to 1.0 kG. A low oxygen level of 2-3 ppm and a high resistivity of 400 ohm-cm is achieved in the AMCZ silicon crystals at B greater than or equal to 1.0 kG. Random striations at B = O, characteristic of turbulent convection, assumed progressively a periodicity, indicative of oscillatory convection at B from 0.35-4.0 kG. The striation contrast or 'intensity' decreased steadily with the increase in B. At B = 4 kG, most of the crystal was free of striations, although some weak, localized periodic striations persisted near the crystal periphery. Spreading-resistance measurement shows, however, a uniform dopant distribution in all crystal sections grown at B from 0.35-4.0 kG within a few percent.

  4. X-ray topography of piezoelectric La(3)Ta(14)Ga(5.5)O(14) crystal grown by Czochralski Method.

    PubMed

    Yoneda, Y; Mizuki, J; Takeda, H; Shiosaki, T

    2008-05-01

    We performed synchrotron X-ray topography on a La(3)Ta0(0.5)Ga (5.5)O(14) (LTG) crystal grown by the Czochralski method. Since a synchrotron X-ray source can provide high-energy X-rays, one can detect bulk structures by X-ray topography. LTG is one of the most attractive piezoelectric crystals along with La(3)Ga(5)SiO(14) (LGS) because of its excellent acoustic properties (temperature compensation of acoustic losses). Since LTG single crystals can be grown from a stoichiometric melt, it was expected that single crystals with better quality than the LGS crystal, which cannot be grown from a stoichiometric system but only from a congruent melt, can be obtained. However, 60 keV X-ray topography revealed that the LTG crystal quality was not as high as the LGS crystal quality. The crystal quality of the central region was lower than that of the surrounding region.

  5. The Czochralski Growth of Large Diameter La3Ga5.5Ta0.5O14 Crystals Along Different Orientations

    SciTech Connect

    Luo,J.; Shah, D.; Klemenz, C.; Dudley, M.; Chen, H.

    2006-01-01

    La3Ga5SiO14, La3Ga5.5Ta0.5O14 and La3Ga5.5Nb0.5O14 crystals exhibit outstanding piezoelectric properties. They are of considerable interest for high-precision resonators. Although the synthesis of these crystals has been actively pursued over the past years, there are still some setbacks slowing down industrial applications. We report on the growth of La3Ga5.5Ta0.5O14 (LGT) crystals by the Czochralski growth along left angle bracket0 0 1right-pointing angle bracket, left angle bracket1 0 0right-pointing angle bracket and left angle bracket1 2 0right-pointing angle bracket. These crystals were characterized by different techniques, including X-ray synchrotron topography. LGT crystals show a facet structure which determines the overall 3D distribution of other defects and strain. The relationship between faceting and crystal imperfections such as striations, dislocations, and inclusions will be discussed. After optimization of growth conditions, inclusions-free, colorless transparent single crystals with a diameter of 2' were obtained. These crystals were processed into Y-cut plano-convex resonators, and the Qf product measured from fundamental to ninth overtone. Values exceeding the limit of AT- and SC-cut quartz were obtained.

  6. Optical quality and structural perfection in La/sub 3/Ga/sub 5/SiO/sub 14/ single crystals grown by Czochralski's method

    SciTech Connect

    Dubovik, M.F.; Ivanova, G.M.; Lebedev, S.A.; Nazarenko, B.P.; Tkachenko, V.F.

    1988-08-01

    Single crystals of La/sub 3/Ga/sub 5/SiO/sub 14/ (LGS, langasite) can act as laser media and are also highly effective piezoelectrics having zero temperature coefficient of frequency. We have grown large langasite single crystals, diameter up to 50 mm and mass up to 600 g, by a modified form of Czochralski's method with automatic control, where we found that the main inhomogeneities are bulk defects, which are localized in the axial section no matter what the orientation for the seed, and inclusions, which include bubbles and microcracks, transverse growth banding, and block structure. These inhomogeneities are related to the growth conditions and make themselves felt in different ways. The optical quality was evaluated from the anomalous birefringence.

  7. Photonic Crystal Sensors Based on Porous Silicon

    PubMed Central

    Pacholski, Claudia

    2013-01-01

    Porous silicon has been established as an excellent sensing platform for the optical detection of hazardous chemicals and biomolecular interactions such as DNA hybridization, antigen/antibody binding, and enzymatic reactions. Its porous nature provides a high surface area within a small volume, which can be easily controlled by changing the pore sizes. As the porosity and consequently the refractive index of an etched porous silicon layer depends on the electrochemial etching conditions photonic crystals composed of multilayered porous silicon films with well-resolved and narrow optical reflectivity features can easily be obtained. The prominent optical response of the photonic crystal decreases the detection limit and therefore increases the sensitivity of porous silicon sensors in comparison to sensors utilizing Fabry-Pérot based optical transduction. Development of porous silicon photonic crystal sensors which allow for the detection of analytes by the naked eye using a simple color change or the fabrication of stacked porous silicon photonic crystals showing two distinct optical features which can be utilized for the discrimination of analytes emphasize its high application potential. PMID:23571671

  8. Photonic crystal sensors based on porous silicon.

    PubMed

    Pacholski, Claudia

    2013-04-09

    Porous silicon has been established as an excellent sensing platform for the optical detection of hazardous chemicals and biomolecular interactions such as DNA hybridization, antigen/antibody binding, and enzymatic reactions. Its porous nature provides a high surface area within a small volume, which can be easily controlled by changing the pore sizes. As the porosity and consequently the refractive index of an etched porous silicon layer depends on the electrochemial etching conditions photonic crystals composed of multilayered porous silicon films with well-resolved and narrow optical reflectivity features can easily be obtained. The prominent optical response of the photonic crystal decreases the detection limit and therefore increases the sensitivity of porous silicon sensors in comparison to sensors utilizing Fabry-Pérot based optical transduction. Development of porous silicon photonic crystal sensors which allow for the detection of analytes by the naked eye using a simple color change or the fabrication of stacked porous silicon photonic crystals showing two distinct optical features which can be utilized for the discrimination of analytes emphasize its high application potential.

  9. Czochralski growth of 2 in. Ca3Ta(Ga,Al)3Si2O14 single crystals for piezoelectric applications

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Akira; Shoji, Yasuhiro; Ohashi, Yuji; Yokota, Yuui; Chani, Valery I.; Kitahara, Masanori; Kudo, Tetsuo; Kamada, Kei; Kurosawa, Shunsuke; Medvedev, Andrey; Kochurikhin, Vladimir

    2016-10-01

    Growth of 2-in. diameter Al-substituted Ca3TaGa3Si2O14 crystals by Czochralski method is reported. The crystals were grown from the melt of Ca3TaGa1.5Al1.5Si2O14 composition and had langasite structure. No inclusions of secondary phases were detected in these crystals. The Ca3Ta(Ga,Al)3Si2O14 mixed crystals produced using non-substituted Ca3TaGa3Si2O14 seeds were defective. They had cracks and/or poly-crystalline structure. However, those grown on the seed of approximately Ca3TaGa1.5Al1.5Si2O14 composition were defect-free. Phase diagram of the Ca3TaGa3Si2O14-Ca3TaAl3Si2O14 pseudo-binary system and segregation phenomenon are discussed in some details. Homogeneity of the crystals was evaluated by measuring 2D-mapping of leaky surface acoustic wave (LSAW) velocities for Y-cut Ca3TaGa1.5Al1.5Si2O14 substrate. Although some inhomogeneities were observed due to slight variations in chemical composition, the crystal had acceptable homogeneity for applications in acoustic wave devices exhibiting the LSAW velocity variation within ±0.048%.

  10. Ca10Li(VO4)7:Nd3+, a promising laser material: growth, structure and spectral characteristics of a Czochralski-grown single crystal

    NASA Astrophysics Data System (ADS)

    Kosmyna, M. B.; Nazarenko, B. P.; Puzikov, V. M.; Shekhovtsov, A. N.; Paszkowicz, W.; Behrooz, A.; Romanowski, P.; Yasukevich, A. S.; Kuleshov, N. V.; Demesh, M. P.; Wierzchowski, W.; Wieteska, K.; Paulmann, C.

    2016-07-01

    Pure and Nd-doped Ca10Li(VO4)7 single crystals were grown by the Czochralski method. The structure of Ca10Li(VO4)7 single crystal was refined starting from a model of Ca10K(VO4)7 using the powder diffraction data collected at a laboratory high-resolution diffractometer. The defect structure of the single crystal was studied with the use of both, high-resolution diffraction using a laboratory instrument and X-ray topographic techniques employing synchrotron radiation at the Hasylab laboratory (Hamburg). Polarized absorption and luminescence spectra of Nd-doped Ca10Li(VO4)7 crystal were investigated in details. The laser oscillation was obtained under flash lamp pumping and the slope efficiency of 0.87% was achieved in the free-running mode. Preliminary examination of lasing properties points that Ca10Li(VO4)7:Nd crystal can be a highly efficient solid state laser medium. Crystals of this kind are expected to be suitable for application as efficient non-linear optics materials.

  11. Intravitreal properties of porous silicon photonic crystals

    PubMed Central

    Cheng, L; Anglin, E; Cunin, F; Kim, D; Sailor, M J; Falkenstein, I; Tammewar, A; Freeman, W R

    2009-01-01

    Aim To determine the suitability of porous silicon photonic crystals for intraocular drug-delivery. Methods A rugate structure was electrochemically etched into a highly doped p-type silicon substrate to create a porous silicon film that was subsequently removed and ultrasonically fractured into particles. To stabilise the particles in aqueous media, the silicon particles were modified by surface alkylation (using thermal hydrosilylation) or by thermal oxidation. Unmodified particles, hydrosilylated particles and oxidised particles were injected into rabbit vitreous. The stability and toxicity of each type of particle were studied by indirect ophthalmoscopy, biomicroscopy, tonometry, electroretinography (ERG) and histology. Results No toxicity was observed with any type of the particles during a period of >4 months. Surface alkylation led to dramatically increased intravitreal stability and slow degradation. The estimated vitreous half-life increased from 1 week (fresh particles) to 5 weeks (oxidised particles) and to 16 weeks (hydrosilylated particles). Conclusion The porous silicon photonic crystals showed good biocompatibility and may be used as an intraocular drug-delivery system. The intravitreal injectable porous silicon photonic crystals may be engineered to host a variety of therapeutics and achieve controlled drug release over long periods of time to treat chronic vitreoretinal diseases. PMID:18441177

  12. Light-induced degradation and metastable-state recovery with reaction kinetics modeling in boron-doped Czochralski silicon solar cells

    SciTech Connect

    Kim, Soo Min; Chun, Seungju; Bae, Suhyun; Park, Seungeun; Lee, Hae-seok Kim, Donghwan; Kang, Min Gu; Song, Hee-eun; Kang, Yoonmook

    2014-08-25

    Solar cells fabricated from boron-doped p-type Czochralski silicon suffer from light-induced degradation that can lower the conversion efficiency by up to 10% relative. When solar cells are exposed to temperatures between 100 °C and 200 °C under illumination, regeneration, in which the minority carrier lifetime is gradually recovered, occurs after the initial light-induced degradation. We studied the light-induced degradation and regeneration process using carrier injection within a design chamber and observed open-circuit voltage trends at various sample temperatures. We proposed a cyclic reaction kinetics model to more precisely analyze the degradation and recovery phenomenon. Our model incorporated the reaction paths that were not counted in the original model between the three states (annealed, degradation, and regeneration). We calculated a rate constant for each reaction path based on the proposed model, extracted an activation energy for each reaction using these rate constants at various temperatures, and calculated activation energies of redegradation and the stabilization reaction.

  13. Modulating the extent of fast and slow boron-oxygen related degradation in Czochralski silicon by thermal annealing: Evidence of a single defect

    NASA Astrophysics Data System (ADS)

    Kim, Moonyong; Abbott, Malcolm; Nampalli, Nitin; Wenham, Stuart; Stefani, Bruno; Hallam, Brett

    2017-02-01

    The fast and slow boron-oxygen related degradation in p-type Czochralski silicon is often attributed to two separate defects due to the different time constants and the determination of different capture cross section ratios (k). However, a recent study using high lifetime samples demonstrated identical recombination properties for the fast and slow degradation and proposed an alternative hypothesis that these were in fact due to a single defect. The study presented in this article provides further experimental evidence to support the single defect hypothesis. Thermal annealing after light soaking is used to investigate the behaviour of subsequent boron-oxygen related degradation. Modifying the temperature and duration of dark annealing on pre-degraded samples is observed to alter the fraction of fast and slow degradation during subsequent illumination. Dark annealing at 173 °C for 60 s is shown to result in almost all degradation occurring during the fast time-scale, whereas annealing at 155 °C for 7 h causes all degradation to occur during the slow time-scale. This modulation occurs without changing the total extent of degradation or changing the capture cross-section ratio. The results are consistent with the fast decay being caused by defect formation from immediately available defect precursors after dark annealing, whereas the slow degradation is caused by the slow transformation of another species into the defect precursor species before the more rapid reaction of defect formation can proceed.

  14. Effect of Rapid Thermal Processing on Light-Induced Degradation of Carrier Lifetime in Czochralski p-Type Silicon Bare Wafers

    NASA Astrophysics Data System (ADS)

    Kouhlane, Y.; Bouhafs, D.; Khelifati, N.; Belhousse, S.; Menari, H.; Guenda, A.; Khelfane, A.

    2016-11-01

    The electrical properties of Czochralski silicon (Cz-Si) p-type boron-doped bare wafers have been investigated after rapid thermal processing (RTP) with different peak temperatures. Treated wafers were exposed to light for various illumination times, and the effective carrier lifetime ( τ eff) measured using the quasi-steady-state photoconductance (QSSPC) technique. τ eff values dropped after prolonged illumination exposure due to light-induced degradation (LID) related to electrical activation of boron-oxygen (BO) complexes, except in the sample treated with peak temperature of 785°C, for which the τ eff degradation was less pronounced. Also, a reduction was observed when using the 830°C peak temperature, an effect that was enhanced by alteration of the wafer morphology (roughness). Furthermore, the electrical resistivity presented good stability under light exposure as a function of temperature compared with reference wafers. Additionally, the optical absorption edge shifted to higher wavelength, leading to increased free-carrier absorption by treated wafers. Moreover, a theoretical model is used to understand the lifetime degradation and regeneration behavior as a function of illumination time. We conclude that RTP plays an important role in carrier lifetime regeneration for Cz-Si wafers via modification of optoelectronic and structural properties. The balance between an optimized RTP cycle and the rest of the solar cell elaboration process can overcome the negative effect of LID and contribute to achievement of higher solar cell efficiency and module performance.

  15. The mechanism of twinning in zincblende structure crystals: New insights on polarity effects from a study of magnetic liquid encapsulated Czochralski grown InP single crystals

    SciTech Connect

    Dudley, M.; Raghothamachar, B.; Guo, Y.

    1998-12-31

    Synchrotron White Beam X-ray Topography (SWBXT) and synchrotron X-ray anomalous scattering have been employed to determine the polarity of {l_brace}111{r_brace} edge facets, anchored to the three phase boundary (TPB) on which twinning is observed to nucleate in Magnetic Liquid Encapsulated Czochralski (MLEC) grown sulfur doped, <001> InP single crystals. Analysis of the results indicates that both the formation of edge facets and the nucleation of twins occur preferentially on {l_brace}{bar 1}{bar 1}{bar 1}{r_brace}{sub P} faces. Of the four possible sets of edge facets, belonging to the {l_brace}{bar 1}{bar 1}{bar 1}{r_brace}{sub P} form, which are oriented so as to be thermodynamically favored to be anchored to the TPB, two can give rise to a {l_brace}115{r_brace} to {l_brace}{bar 1}{bar 1}{bar 1}{r_brace}{sub P} external should facet conversion upon twinning, while the other two can give rise to a {l_brace}114{r_brace} to {l_brace}110{r_brace} conversion. For these cases, twinning is only observed when the {l_brace}{bar 1}{bar 1}{bar 1}{r_brace}{sub P} edge facets are anchored to the TPB in a region where the shoulder angle is close to 74.21{degree} or 70.53{degree}, facilitating the production of the {l_brace}115{r_brace} and {l_brace}114{r_brace} external should facets, respectively, prior to twinning. These observations are discussed in light of calculated surface energies of the various internal and external facets.

  16. Silicon carbide - Progress in crystal growth

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony

    1987-01-01

    Recent progress in the development of two processes for producing large-area high-quality single crystals of SiC is described: (1) a modified Lely process for the growth of the alpha polytypes (e.g., 6H SiC) initially developed by Tairov and Tsvetkov (1978, 1981) and Ziegler et al. (1983), and (2) a process for the epitaxial growth of the beta polytype on single-crystal silicon or other substrates. Growth of large-area cubic SiC on Si is described together with growth of defect-free beta-SiC films on alpha-6H SiC crystals and TiC lattice. Semiconducting qualities of silicon carbide crystals grown by various techniques are discussed.

  17. Silicon carbide - Progress in crystal growth

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony

    1987-01-01

    Recent progress in the development of two processes for producing large-area high-quality single crystals of SiC is described: (1) a modified Lely process for the growth of the alpha polytypes (e.g., 6H SiC) initially developed by Tairov and Tsvetkov (1978, 1981) and Ziegler et al. (1983), and (2) a process for the epitaxial growth of the beta polytype on single-crystal silicon or other substrates. Growth of large-area cubic SiC on Si is described together with growth of defect-free beta-SiC films on alpha-6H SiC crystals and TiC lattice. Semiconducting qualities of silicon carbide crystals grown by various techniques are discussed.

  18. Configurable silicon photonic crystal waveguides

    SciTech Connect

    Prorok, Stefan; Petrov, Alexander; Eich, Manfred; Luo, Jingdong; Jen, Alex K.-Y.

    2013-12-23

    In this Letter, we demonstrate that the mode cut off of a photonic crystal waveguide can be trimmed with high accuracy by electron beam bleaching of a chromophore doped polymer cladding. Using this method, configurable waveguides are realized, which allow for spatially resolved changes of the photonic crystal's effective lattice constant as small as 7.6 pm. We show three different examples how to take advantage of configurable photonic crystal waveguides: Shifting of the complete transmission spectrum, definition of cavities with high quality factor, and tuning of existing cavities.

  19. National solar technology roadmap: Wafer-silicon PV

    SciTech Connect

    Sopori, Bhushan

    2007-06-01

    This report applies to all bulk-silicon-based PV technologies, including those based on Czochralski, multicrystalline, float-zone wafers, and melt-grown crystals that are 100 μm or thicker, such as ribbons, sheet, or spheral silicon.

  20. Devices made on single crystal silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Ying

    The interchip delay and performance mismatch at the chip level degrades the system performance. Further increases in system performance will require one to move from integrated circuits assembled on a board to true integrated systems. All the devices that perform different functions are put on a single substrate. Using this method, the interconnect distance decreases from centimeters to micrometers, thus dramatically decreasing the delay. Also, much of the chip level mismatch is eliminated. The single crystal silicon nanoparticle is a good candidate for one of the primary building blocks of such an integrated system. The devices made on silicon are stable; carrier mobility in single crystal silicon is reasonably high; modern silicon manufacturing infrastructure can be used to make silicon nanoparticle devices easily; and there exists a technology to localize the particles. In addition, the particle is a 3-D structure, making it possible to build a compact 3-D integrated system. In this thesis, a vacuum system was built to generate single crystal silicon nanoparticles. The particles were generated in a silane plasma, focused by aerodynamic lens and annealed in flight using a high temperature furnace. Single crystal silicon nanoparticles as large as 100 nm have been obtained. MSM (Metal-Silicon-Metal) structure was made on the silicon particles and the current-voltage (I-V) relationship through the particles was obtained. Thermionic theory and space charge limited current theory were used to explain the operation of the device. Schottky barrier height and trap density were obtained. SBFETs (Schottky Barrier Field Effect Transistors) were also built. Devices show PMOS characteristics and asymmetric characteristics to the zero drain voltage. Numerical simulation was performed on the MSM structure and SBFET to help understand the mechanism of device performance. I-V relationship generally shows good agreement with the measured result. Contours of band structure and

  1. Flexible single-crystal silicon nanomembrane photonic crystal cavity.

    PubMed

    Xu, Xiaochuan; Subbaraman, Harish; Chakravarty, Swapnajit; Hosseini, Amir; Covey, John; Yu, Yalin; Kwong, David; Zhang, Yang; Lai, Wei-Cheng; Zou, Yi; Lu, Nanshu; Chen, Ray T

    2014-12-23

    Flexible inorganic electronic devices promise numerous applications, especially in fields that could not be covered satisfactorily by conventional rigid devices. Benefits on a similar scale are also foreseeable for silicon photonic components. However, the difficulty in transferring intricate silicon photonic devices has deterred widespread development. In this paper, we demonstrate a flexible single-crystal silicon nanomembrane photonic crystal microcavity through a bonding and substrate removal approach. The transferred cavity shows a quality factor of 2.2×10(4) and could be bent to a curvature of 5 mm radius without deteriorating the performance compared to its counterparts on rigid substrates. A thorough characterization of the device reveals that the resonant wavelength is a linear function of the bending-induced strain. The device also shows a curvature-independent sensitivity to the ambient index variation.

  2. Trapping and diffusion kinetic of hydrogen in carbon-cluster ion-implantation projected range in Czochralski silicon wafers

    NASA Astrophysics Data System (ADS)

    Okuyama, Ryosuke; Masada, Ayumi; Kadono, Takeshi; Hirose, Ryo; Koga, Yoshihiro; Okuda, Hidehiko; Kurita, Kazunari

    2017-02-01

    We investigated the diffusion behavior of hydrogen in a silicon wafer made by a carbon-cluster ion-implantation technique after heat treatment and silicon epitaxial growth. A hydrogen peak was observed after high-temperature heat treatment (>1000 °C) and silicon epitaxial growth by secondary ion mass spectrometry analysis. We also confirmed that the hydrogen peak concentration decreased after epitaxial growth upon additional heat treatment. Such a hydrogen diffusion behavior has not been reported. Thus, we derived the activation energy from the projected range of a carbon cluster, assuming only a dissociation reaction, and obtained an activation energy of 0.76 ± 0.04 eV. This value is extremely close to that for the diffusion of hydrogen molecules located at the tetrahedral interstitial site and hydrogen molecules dissociated from multivacancies. Therefore, we assume that the hydrogen in the carbon-cluster projected range diffuses in the molecular state, and hydrogen remaining in the projected range forms complexes of carbon, oxygen, and vacancies.

  3. Solar cell structure incorporating a novel single crystal silicon material

    DOEpatents

    Pankove, Jacques I.; Wu, Chung P.

    1983-01-01

    A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

  4. The historical trend in float zone crystal diameters and power requirements for float zoned silicon crystals

    NASA Technical Reports Server (NTRS)

    Kramer, H. G.

    1981-01-01

    The power needed to zone silicon crystals by radio frequency heating was analyzed. The heat loss mechanisms are examined. Curves are presented for power as a function of crystal diameter for commercial silicon zoning.

  5. The historical trend in float zone crystal diameters and power requirements for float zoned silicon crystals

    NASA Technical Reports Server (NTRS)

    Kramer, H. G.

    1981-01-01

    The power needed to zone silicon crystals by radio frequency heating was analyzed. The heat loss mechanisms are examined. Curves are presented for power as a function of crystal diameter for commercial silicon zoning.

  6. Estimated effects of silicone glue on protein crystal growth

    NASA Astrophysics Data System (ADS)

    Maruyama, Mihoko; Shimizu, Noriko; Sugiyama, Shigeru; Takahashi, Yoshinori; Adachi, Hiroaki; Takano, Kazufumi; Murakami, Satoshi; Inoue, Tsuyoshi; Matsumura, Hiroyoshi; Mori, Yusuke

    2010-09-01

    Silicone glue (modified silicone polymer) is widely used for both experiments involving inorganic crystal growth and those involving organic materials like proteins. This material is very useful for building a hand-made experiment setup or for fixing protein crystals to specific locations. Though silicone glue is regarded as harmful to proteins, no systematic verification was performed to investigate its impurity effects on protein crystal growth. We focused on and estimated the impurity effects of silicone glue on protein crystal growth. Hen egg white lysozyme (HEWL) was used as a model protein. Surface morphology and step velocity of tetragonal lysozyme crystals in the presence and absence of silicone glue were investigated by laser confocal interference contrast microscopy (LCM-DIM). The surface morphology of a tetragonal lysozyme crystal in the presence of silicone glue corresponded to that grown in a lysozyme solution without silicone glue. The dependency of step velocities on supersaturation in the presence of silicone glue also exhibited the same tendency as that of a glue-free system. These two phenomena indicate that the silicone glue did not act as an impurity on lysozyme crystals. Therefore, we conclude that silicone glue is an effective material for various unique experiments involving protein crystals or for applying new methods to create large, high-quality protein crystals.

  7. Photocarrier Radiometry Investigation of Light-Induced Degradation of Boron-Doped Czochralski-Grown Silicon Without Surface Passivation

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Li, Bincheng

    2016-04-01

    Light-induced degradation (LID) effects of boron-doped Cz silicon wafers without surface passivation are investigated in details by photocarrier radiometry (PCR). The resistivity of all samples is in the range of 0.006 Ω {\\cdot } {cm} to 38 Ω {\\cdot } {cm}. It is found that light-induced changes in surface state occupation have a great effect on LID under illumination. With the increasing contribution of light-induced changes in surface state occupation, the generation rate of the defect decreases. The light-induced changes in surface state occupation and light-induced degradation dominate the temporal behaviors of the excess carrier density of high- and low-resistivity Si wafers, respectively. Moreover, the temporal behaviors of PCR signals of these samples under laser illumination with different powers, energy of photons, and multiple illuminations were also analyzed to understand the light-induced change of material properties. Based on the nonlinear dependence of PCR signal on the excitation power, a theoretical model taking into account both light-induced changes in surface state occupation and LID processes was proposed to explain those temporal behaviors.

  8. Theoretical study of the impact of stress and interstitial oxygen on the behavior of intrinsic point defects in growing Czochralski Si crystals

    NASA Astrophysics Data System (ADS)

    Sueoka, K.; Nakamura, K.; Vanhellemont, J.

    2017-09-01

    For the development of crystal pulling processes for 450 mm-diameter defect-free Si crystals, it is important to evaluate the impact of thermal stress on intrinsic point defect behavior during crystal growth. In a crystal growing from a melt, the melt/solid interface can be considered as being stress-free. Due to that the thermal stress in the growing substrate near the interface is internal plane stress. Previously, we evaluated the impact of (001) planar-isotropic stress on the formation enthalpy (Hf) of the vacancy (V) and the self-interstitial (I) using density functional theory (DFT) calculations, and explained quantitatively the published experimental values of the so-called ;Voronkov criterion;. The thermal stress in a growing crystal is indeed planar but is not isotropic in the plane except for the central region of the crystal. The purpose of the present study is to estimate the impact of planar-anisotropic stress on the formation enthalpy Hf of V and I. It is found that the three stress dependencies of σx: σy=1: 1 (planar-isotropic), 2: 1, 5: 1 (planar-anisotropic) are close to each other, independent of the assumption of isotropic or anisotropic planar stress. This is the reason why the experimental results obtained over the whole radial direction of the crystal are well reproduced by the calculated results assuming planar-isotropic stress. A uniaxial stress dependence which is a good assumption for the crystal peripheral region, leads also to results that are close to those for the planar stress dependence. Also the mechanisms behind the experimentally observed impact of interstitial oxygen (Oi), introduced during Czochralski Si growth, on V and I concentrations are clarified. DFT calculations are performed to obtain the formation energies (Ef) of V and I at all sites within a sphere with 5 Å radius around the Oi atom. Formation (vibration) entropy (Sf) calculations for V and I are also performed. It is found that both EfV and SfV of V in the zigzag

  9. Effect of internal radiation on the diameter instability observed during the Czochralski growth of Cr4+, Nd3+: YAG crystal

    NASA Astrophysics Data System (ADS)

    Faiez, Reza; Rezaei, Yazdan

    2016-12-01

    In this paper, the growth process and the absorption spectra properties of the Cr4+, Nd3+:YAG crystal are reported. The crystal diameter instability, which occurred just beneath the shoulder, is associated with a nearly sharp change in the crystal color. The effect is described in terms of the internal radiative heat transport through the semitransparent garnet crystal which is highly sensitive to the optical properties of the dopant ions. The color gradient along the crystal is assigned to the charge compensation mechanism almost failed at around the shoulder stage of the process, and the instability is mainly attributed to a significant decrease in the radiative heat transfer within the crystal. The effect of radiative heat transfer, within the crystal and the melt, on the crystallization front shape is numerically investigated to simulate the observed instability. Due to the large segregation coefficient of chromium ions, increasing in the optical thickness of the crystal corresponds to a decrease in that of the melt. It is shown that, both of these variations of optical properties result in a significant decrease in the convexity of the crystal-melt interface. The effect of impurity deposition on the crystal surface was found to lower the critical Reynolds number at which the interface inversion occurs.

  10. Cutting fluid study for single crystal silicon

    SciTech Connect

    Chargin, D.

    1998-05-05

    An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions showed promise for further research, as they yielded the best combination of reduced tool wear and good surface finish in the ductile regime. Negative rake tools were verified to improve the surface finish, but the negative rake tools used in the experiments also showed much higher wear than conventional 0{degree} rake tools. Effects of crystallographic orientation on SPDT, such as star patterns of fracture damage forming near the center of the samples, were observed to decrease with lower feedrates. Silicon chips were observed and photographed, indicative of a ductile materials removal process.

  11. Excimer laser crystallization of hydrogenated amorphous silicon

    SciTech Connect

    Dai Yongbing; Xu Zhongyang; Wang Changan; Zhang Shaoqiang; An Chengwu; Li Xingjiao; Wan Xinheng; Ding Hui

    1996-12-31

    Hydrogenated amorphous silicon (a-Si:H) films have been crystallized by the irradiations of XeCl excimer laser. The crystallized films have been examined by scanning electron microscopy (SEM), x-ray diffraction (XRD) and conductivity measurements to clarify their morphologies, structure and electrical properties. The results show that a high conductive super thin layer is formed by a single pulse laser irradiation with the energy density of 75mJ/cm{sup 2}. The conductivity increases quickly at laser energy density threshold which decreases when the hydrogen in a-Si:H films is removed by pre-annealing. During crystallization process, oxygen atoms from the air ambient have been introduced into the films and such an introducing process is hindered by the hydrogen eruption. When the oxygen content is high enough, the carrier-transport mechanism includes thermionic emission (TE) and thermionic field emission (TFE) in the vicinity of room temperature, which is similar to semi-insulating polycrystalline silicon (SIPOS).

  12. A virtual crystallization furnace for solar silicon

    SciTech Connect

    Steinbach, I.; Franke, D.; Krumbe, W.; Liebermann, J.

    1994-12-31

    Blocks of silicon for photovoltaic applications are economically crystallized in large casting furnaces. The quality of the material is determined by the velocity of the crystallization front, the flatness of the liquid-solid interface and the thermal gradients in the solid during cooling. The process cycle time, which is determined by the rate of crystallization and cooling, has a large effect on the process economic viability. Traditionally trial and error was used to determine the process control parameters, the success of which depended on the operator`s experience and intuition. This paper presents a numerical model, which when completed by a fitted data set, constitutes a virtual model of a real crystallization furnace, the Virtual Crystallization Furnace (VCF). The time-temperature distribution during the process cycle is the main output, which includes a display of actual liquid-solid front position. Moreover, solidification velocity, temperature gradients and thermal stresses can be deduced from this output. The time needed to run a simulation on a modern work-station is approximately 1/6 of real process time, thereby allowing the user to make many process variations at very reasonable costs. Therefore the VCF is a powerful tool for optimizing the process in order to reduce cycle time and to increase product quality.

  13. Intrinsic point defect behavior in silicon crystals during growth from the melt: A model derived from experimental results

    NASA Astrophysics Data System (ADS)

    Abe, Takao; Takahashi, Toru

    2011-11-01

    During the growth of float-zoning (FZ) and Czochralski (CZ) Si crystals, the temperature distributions from the growth interface were measured using a two-color infrared thermometer for the FZ crystal surfaces and three thermocouples within the CZ bulk crystals. The results showed that the thermal gradient is a decreasing function of the growth rate, which forms the basis of this work. In a comparison of the shape variations in the growth interfaces observed in both FZ and CZ crystals of three different diameters, all of the results were in agreement with the above premise. In consideration of Stefan's condition the premise above is discussed. One of the most important observations is that the region of increasing thermal gradient extends not only to the region grown before but also to the region afterward by stopping the pulling in FZ crystals or lowering the growth rate in CZ crystals. This phenomenon is termed the “BA (before and after) effect”. The growing CZ crystals are detached from the melt and rapidly cooled so that the point defects are frozen. Using the anomalous oxygen precipitation (AOP) phenomenon obtained by the above detaching, which demonstrates the existence of vacancies in the crystal, we found that the growth interface is always filled with vacancies. By increasing the thermal gradient, which can be controlled by lowering the growth rate, the vacancy (AOP) region is reduced, due to the generation of a silicon interstitial-rich region. The ratio of vacancies from the growth interface and silicon interstitials generated by the thermal gradient ultimately determines the nature of the bulk silicon crystal grown from the melt, i.e., with voids, defect-free or with dislocation loops.

  14. Optical and scintillation properties of ce-doped (Gd2Y1)Ga2.7Al2.3O12 single crystal grown by Czochralski method

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Wu, Yuntao; Ding, Dongzhou; Li, Huanying; Chen, Xiaofeng; Shi, Jian; Ren, Guohao

    2016-06-01

    Multicomponent garnets, due to their excellent light yield and energy resolution, become one of the most promising scintillators used for homeland security and nuclear non-proliferation applications. This work focuses on the optimization of Ce-doped (Gd,Y)3(Ga,Al)5O12 scintillators using a combination strategy of pre-screening and scale-up. Ce-doped GdxY1-xGayAl5-yO12 (x=1, 2 and y=2, 2.2, 2.5, 2.7, 3) polycrystalline powders were prepared by high-temperature solid state reaction method. The desired garnet phase in all the samples was confirmed using X-ray diffraction measurement. By comparing the radioluminescence intensity, the highest scintillation efficiency was achieved at a component of Gd2Y1Ga2.7Al2.3O12:Ce powders. A (Gd2Y1)Ga2.7Al2.3O12 doped with 1% Ce single crystal with dimensions of Ø35×40 mm was grown by Czochralski method using a <111> oriented seed. Luminescence and scintillation properties were measured. An optical transmittance of 84% was achieved in the concerned wavelength from 500 to 800 nm. Its 5d-4f emission of Ce3+ is at 530 nm. The light yield of a Ce1%: Gd2Y1Ga2.7Al2.3O12 single crystal slab at a size of 5×5×1 mm3 can reach about 65,000±3000 Ph/MeV along with two decay components of 94 and 615 ns under 137Cs source irradiation.

  15. Silicon heterojunction solar cell and crystallization of amorphous silicon

    NASA Astrophysics Data System (ADS)

    Lu, Meijun

    The rapid growth of photovoltaics in the past decade brings on the soaring price and demand for crystalline silicon. Hence it becomes necessary and also profitable to develop solar cells with over 20% efficiency, using thin (˜100mum) silicon wafers. In this respect, diffused junction cells are not the best choice, since the inescapable heating in the diffusion process not only makes it hard to handle thin wafers, but also reduces carriers' bulk lifetime and impairs the crystal quality of the substrate, which could lower cell efficiency. An alternative is the heterojunction cells, such as amorphous silicon/crystalline silicon heterojunction (SHJ) solar cell, where the emitter layer can be grown at low temperature (<200°C). In first part of this dissertation, I will introduce our work on front-junction SHJ solar cell, including the importance of intrinsic buffer layer; the discussion on the often observed anomalous "S"-shaped J-V curve (low fill factor) by using band diagram analysis; the surface passivation quality of intrinsic buffer and its relationship to the performance of front-junction SHJ cells. Although the a-Si:H is found to help to achieve high efficiency in c-Si heterojuntion solar cells, it also absorbs short wavelength (<600 nm) light, leading to non-ideal blue response and lower short circuit currents (JSC) in the front-junction SHJ cells. Considering this, heterojunction with both a-Si:H emitter and base contact on the back side in an interdigitated pattern, i.e. interdigitated back contact silicon heterojunction (IBC-SHJ) solar cell, is developed. This dissertation will show our progress in developing IBC-SHJ solar cells, including the structure design; device fabrication and characterization; two dimensional simulation by using simulator Sentaurus Device; some special features of IBC-SHJ solar cells; and performance of IBC-SHJ cells without and with back surface buffer layers. Another trend for solar cell industry is thin film solar cells, since

  16. Analysis of local lattice strain around oxygen precipitates in silicon crystals using CBED technique

    NASA Astrophysics Data System (ADS)

    Yonemura, Mitsuharu; Sueoka, Koji; Kamei, Kazuhito

    1998-06-01

    Oxygen precipitates (SiO x) in Czochralski-grown silicon single crystals (CZ-Si) have been used for the `getter' sink for impurities introduced during the LSI wafer manufacturing process. In order to understand the `gettering' phenomena, lattice strain fields around the precipitates have been measured quantitatively using convergent beam electron diffraction (CBED). The local lattice strain can be measured from higher order Laue zone (HOLZ) patterns since the HOLZ pattern in the bright field disk is sensitive to the lattice displacement. As a result, a tetragonal distortion of silicon lattices was found in the vicinity of a platelet of an oxygen precipitate. That is, the strain due to the displacement of (001) Si planes is compressive along the direction normal to [001] Si and is tensile along the direction parallel to [001] Si. The normal strain is estimated to be about 0.3% near the flat plane of the platelet and 0.1% near the edge of the platelet whose edge length is about 500 nm. The results are discussed and compared to those from the finite element method (FEM) simulation.

  17. Tribological properties of sintered polycrystalline and single crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.; Srinivasan, M.

    1982-01-01

    Tribological studies and X-ray photoelectron spectroscopy analyses were conducted with sintered polycrystalline and single crystal silicon carbide surfaces in sliding contact with iron at various temperatures to 1500 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on both the friction properties and the surface chemistry of silicon carbide. The main contaminants on the as received sintered polycrystalline silicon carbide surfaces are adsorbed carbon, oxygen, graphite, and silicon dioxide. The surface revealed a low coefficient of friction. This is due to the presence of the graphite on the surface. At temperatures of 400 to 600 C graphite and copious amount of silicon dioxide were observed on the polycrystalline silicon carbide surface in addition to silicon carbide. At 800 C, the amount of the silicon dioxide decreased rapidly and the silicon carbide type silicon and carbon peaks were at a maximum intensity in the XPS spectra. The coefficients of friction were high in the temperature range 400 to 800 C. Small amounts of carbon and oxygen contaminants were observed on the as received single crystal silicon carbide surface below 250 C. Silicon carbide type silicon and carbon peaks were seen on the silicon carbide in addition to very small amount of graphite and silicon dioxide at temperatures of 450 to 800 C.

  18. Czochralski growth of NaNO3-LiNO3 solid solution single crystals using axial vibrational control technique

    NASA Astrophysics Data System (ADS)

    Avetissov, Igor; Sadovskiy, Andrei; Belov, Stanislav; Kong Khan, Chan; Mozhevitina, Elena; Sukhanova, Ekaterina; Zharikov, Eugeniy

    2014-09-01

    T-x diagram of LiNO3-NaNO3 quasi-binary system has been improved using an original technique based on Raman measurements of condense phase. (LiNO3)x(NaNO3)1-x solid solution single crystal has been grown at different regimes of axial vibrational control (AVC) technique. Significant difference in segregation coefficient behavior between AVC-CZ and conventional CZ grown crystals has appeared: with AVC intensity increase the segregation coefficient (SC) raises for light molecular weight elements, SC reduces for medium molecular weight elements, and SC remains practically unchangeable for heavy molecular weight elements. Effect of vibrational intensity on vibron and optical characteristics, microhardness of AVC-CZ (LiNO3)x(NaNO3)1-x solid solution single crystals has been studied. For the AVC-CZ crystals has been observed increases in microhardness as well as in optical transmission up to 10 rel% compare to conventional CZ grown crystals.

  19. Structural and electrical properties of oxygen complexes in Cz and FZ silicon crystals implanted with carbon ions

    NASA Astrophysics Data System (ADS)

    Romanyuk, Boris; Melnik, Victor; Popov, Valentin; Babich, Vilik; Kladko, Vasyl; Gudymenko, Olexandr; Ilchenko, Volodimir; Vasyliev, Iegor; Goriachko, Andrii

    2014-12-01

    We present a comparative study of thermal donor (TD) center formation mechanisms as a result of carbon ion implantation into float zone (FZ-Si) and Czochralski (Cz-Si) silicon crystals. The kinetics of the TD center formation and transformation of their structure during annealing have been investigated. Also, the TD center formation takes place after additional oxygen implantation into FZ/Cz-Si, and an important role of recoil oxygen atoms (from the screen oxide) has been demonstrated for the FZ-Si case. Their concentration in the Si surface layer depends on the implantation dose and the screen oxide thickness, reaching up to values 1018 to 1019 cm-3, which is comparable with the oxygen concentration in Cz-Si. These oxygen atoms can lead to additional thermal donor centers generation, especially in the FZ-Si.

  20. Ultrahigh-quality silicon carbide single crystals.

    PubMed

    Nakamura, Daisuke; Gunjishima, Itaru; Yamaguchi, Satoshi; Ito, Tadashi; Okamoto, Atsuto; Kondo, Hiroyuki; Onda, Shoichi; Takatori, Kazumasa

    2004-08-26

    Silicon carbide (SiC) has a range of useful physical, mechanical and electronic properties that make it a promising material for next-generation electronic devices. Careful consideration of the thermal conditions in which SiC [0001] is grown has resulted in improvements in crystal diameter and quality: the quantity of macroscopic defects such as hollow core dislocations (micropipes), inclusions, small-angle boundaries and long-range lattice warp has been reduced. But some macroscopic defects (about 1-10 cm(-2)) and a large density of elementary dislocations (approximately 10(4) cm(-2)), such as edge, basal plane and screw dislocations, remain within the crystal, and have so far prevented the realization of high-efficiency, reliable electronic devices in SiC (refs 12-16). Here we report a method, inspired by the dislocation structure of SiC grown perpendicular to the c-axis (a-face growth), to reduce the number of dislocations in SiC single crystals by two to three orders of magnitude, rendering them virtually dislocation-free. These substrates will promote the development of high-power SiC devices and reduce energy losses of the resulting electrical systems.

  1. Interface and facet control during Czochralski growth of (111) InSb crystals for cost reduction and yield improvement of IR focal plane array substrates

    NASA Astrophysics Data System (ADS)

    Gray, Nathan W.; Perez-Rubio, Victor; Bolke, Joseph G.; Alexander, W. B.

    2014-10-01

    Focal plane arrays (FPAs) made on InSb wafers are the key cost-driving component in IR imaging systems. The electronic and crystallographic properties of the wafer directly determine the imaging device performance. The "facet effect" describes the non-uniform electronic properties of crystals resulting from anisotropic dopant segregation during bulk growth. When the segregation coefficient of dopant impurities changes notably across the melt/solid interface of a growing crystal the result is non-uniform electronic properties across wafers made from these crystals. The effect is more pronounced in InSb crystals grown on the (111) axis compared with other orientations and crystal systems. FPA devices made on these wafers suffer costly yield hits due to inconsistent device response and performance. Historically, InSb crystal growers have grown approximately 9-19 degree off-axis from the (111) to avoid the facet effect and produced wafers with improved uniformity of electronic properties. It has been shown by researchers in the 1960s that control of the facet effect can produce uniform small diameter crystals. In this paper, we share results employing a process that controls the facet effect when growing large diameter crystals from which 4, 5, and 6" wafers can be manufactured. The process change resulted in an increase in wafers yielded per crystal by several times, all with high crystal quality and uniform electronic properties. Since the crystals are grown on the (111) axis, manufacturing (111) oriented wafers is straightforward with standard semiconductor equipment and processes common to the high-volume silicon wafer industry. These benefits result in significant manufacturing cost savings and increased value to our customers.

  2. Growth of InP single crystals by liquid encapsulated Czochralski (LEC) using glassy-carbon crucibles

    SciTech Connect

    Oliveira, C.E.M. de; Miskys, C.R.; Carvalho, M.M.G. de

    1996-12-31

    Using a high pressure puller and Glassy-Carbon crucibles, undoped InP single crystals weighing 100g and with 25 mm diameter were grown in the <100> direction. The residual carrier concentration of samples, measure by the Van der Pauw method at 300K, was about 5 {times} 10{sup 15}cm{sup {minus}3}, result as good as those obtained with Quartz crucibles with the advantage that Glassy-Carbon crucibles are fully reusable.

  3. Gas-Jet Cooling Would Improve Czochralski Process

    NASA Technical Reports Server (NTRS)

    Dudukovic, M. P.; Ramachandran, P. A.; Srivastava, R. K.

    1989-01-01

    Controlled cooling by jets of gas improves growth of single crystals of silocon by Czochralski process, according to study. Rate of cooling by jets joins temperature of crucible and pulling rate as input variable of process adjusted to achieve required diameter of crystal and shape of crystal/melt interface. Critical parameters of growing crystal, output variables of Czochralski process controlled via two or all three of input variables. One input variable, usually speed, held constant while other two adjusted to achieve required diameter and interface.

  4. Effect of gettering operations on the slip of electrically active impurities in Si grown by the Czochralsky method

    SciTech Connect

    Gulidov, E.N.; Edidel'man, B.L.; Kalinushkin, V.P.; Murin, D.I.; Ploppa, M.G.; Prokhorov, A.M.; Shvedenko, M.V.

    1985-11-01

    This article studies the coarse-scale impurity accumulations in crystals of large-diameter standard industrial Si, grown by the Czochralski method and doped with boron using smallangle scattering of light, and the effect on them from operations of abrasive and internal gettering. Experiments are also shown on the effect of increased sample temperatures on the scattering of light. The results show that silicon grown by the Czochralski method and doped with boron contains coarsescale accumulations of impurities which are ionized at 300 degrees K. Abrasive gettering leads to a substantial lowering of the concentration of the impurities in these accumulations and to a corresponding decrease of their electrical activity according to the authors. The study of the effect of internal gettering is inhibited by factors discussed.

  5. Investigation of the variations in the crystallization front shape during growth of gadolinium gallium and terbium gallium crystals by the Czochralski method

    SciTech Connect

    Budenkova, O. N. Vasiliev, M. G.; Yuferev, V. S.; Ivanov, I. A.; Bul'kanov, A. M.; Kalaev, V. V.

    2008-12-15

    Numerical investigation of the variations in the crystallization front shape during growth of gadolinium gallium and terbium gallium garnet crystals in the same thermal zone and comparison of the obtained results with the experimental data have been performed. It is shown that the difference in the behavior of the crystallization front during growth of the crystals is related to their different transparency in the IR region. In gadolinium gallium garnet crystals, which are transparent to thermal radiation, a crystallization front, strongly convex toward the melt, is formed in the growth stage, which extremely rapidly melts under forced convection. Numerical analysis of this process has been performed within the quasistationary and nonstationary models. At the same time, in terbium gallium garnet crystals, which are characterized by strong absorption of thermal radiation, the phase boundary shape changes fairly smoothly and with a small amplitude. In this case, as the crystal is pulled, the crystallization front tends to become convex toward the crystal bulk.

  6. X-ray diffraction investigation of structural distortion in crystals with a disturbed surface layer

    SciTech Connect

    Nikolaev, V.V.; Khrupa, V.I.; Krasulya, S.M.

    1994-09-01

    An experimental method allowing the testing of defects in the bulk of single crystals with a surface layer damaged by mechanical treatment is described. The subject of the investigation were silicon crystals, grown by the crucibleless zone melting and Czochralski methods.

  7. Liquid crystal claddings for passive temperature stabilization of silicon photonics

    NASA Astrophysics Data System (ADS)

    Ptasinski, Joanna N.; Khoo, Iam-Choon; Fainman, Yeshaiahu

    2014-10-01

    Silicon photonics allows for high density component integration on a single chip and it brings promise for low-loss, high-bandwidth data processing in modern computing systems. Owing to silicon's high positive thermo-optic coefficient, temperature fluctuations tend to degrade the device performance. This work explores passive thermal stabilization of silicon photonic devices using nematic liquid crystal (NLC) claddings, as they possess large negative thermo-optic coefficients in addition to low absorption at the telecommunication wavelengths.

  8. Mechanism of the emergence of the photo-EMF upon silicon liquid crystal-single crystal contact

    NASA Astrophysics Data System (ADS)

    Budagov, K. M.; Guseinov, A. G.; Pashaev, B. G.

    2017-03-01

    The effect light has on a silicon liquid crystal-single crystal contact at different temperatures of the surface doping of silicon, and when BaTiO3 nanoparticles are added to the composition of a liquid crystal, is studied. The mechanism of the emergence of the photo-EMF in the liquid crystal-silicon structure is explained.

  9. Studying post-etching silicon crystal defects on 300mm wafer by automatic defect review AFM

    NASA Astrophysics Data System (ADS)

    Zandiatashbar, Ardavan; Taylor, Patrick A.; Kim, Byong; Yoo, Young-kook; Lee, Keibock; Jo, Ahjin; Lee, Ju Suk; Cho, Sang-Joon; Park, Sang-il

    2016-03-01

    Single crystal silicon wafers are the fundamental elements of semiconductor manufacturing industry. The wafers produced by Czochralski (CZ) process are very high quality single crystalline materials with known defects that are formed during the crystal growth or modified by further processing. While defects can be unfavorable for yield for some manufactured electrical devices, a group of defects like oxide precipitates can have both positive and negative impacts on the final device. The spatial distribution of these defects may be found by scattering techniques. However, due to limitations of scattering (i.e. light wavelength), many crystal defects are either poorly classified or not detected. Therefore a high throughput and accurate characterization of their shape and dimension is essential for reviewing the defects and proper classification. While scanning electron microscopy (SEM) can provide high resolution twodimensional images, atomic force microscopy (AFM) is essential for obtaining three-dimensional information of the defects of interest (DOI) as it is known to provide the highest vertical resolution among all techniques [1]. However AFM's low throughput, limited tip life, and laborious efforts for locating the DOI have been the limitations of this technique for defect review for 300 mm wafers. To address these limitations of AFM, automatic defect review AFM has been introduced recently [2], and is utilized in this work for studying DOI on 300 mm silicon wafer. In this work, we carefully etched a 300 mm silicon wafer with a gaseous acid in a reducing atmosphere at a temperature and for a sufficient duration to decorate and grow the crystal defects to a size capable of being detected as light scattering defects [3]. The etched defects form a shallow structure and their distribution and relative size are inspected by laser light scattering (LLS). However, several groups of defects couldn't be properly sized by the LLS due to the very shallow depth and low

  10. Raman cooling in silicon photonic crystals

    NASA Astrophysics Data System (ADS)

    Chen, Yin-Chung; Bahl, Gaurav

    2016-03-01

    Laser cooling of solids can be achieved through various photon up-conversion processes including anti-Stokes photoluminescence and anti-Stokes light scattering. While it has been shown that cooling using photoluminescence-based methods can achieve efficiency comparable to that of thermoelectric cooling, the reliance on specific transitions of the rare-earth dopants limits material choice. Light scattering, on the other hand, occurs in all materials, and has the potential to enable cooling in most materials. We show that by engineering the photonic density of states of a material, one can suppress the Stokes process, and enhance the anti-Stokes radiation. We employ the well-known diamond-structured photonic crystal patterned in crystalline silicon to demonstrate theoretically that when operating within a high transparency regime, the net energy removal rate from phonon annihilation can overcome the optical absorption. The engineered photonic density of states can thus enable simultaneous cooling of all Raman-active phonon modes and the net cooling of the solid.

  11. Oxygen precipitation behavior in heavily arsenic doped silicon crystals

    NASA Astrophysics Data System (ADS)

    Haringer, Stephan; Gambaro, Daniela; Porrini, Maria

    2017-01-01

    Silicon crystals containing different levels of arsenic concentration and oxygen content were grown, and samples were taken at various positions along the crystal, to study the influence of three main factors, i.e. the initial oxygen content, the dopant concentration and the thermal history, on the nucleation of oxygen precipitates during crystal growth and cooling in the puller. The crystal thermal history was reconstructed by means of computer modeling, simulating the temperature distribution in the crystal at several growth stages. The oxygen precipitation was characterized after a thermal cycle of 4 h at 800 °C for nuclei stabilization +16 h at 1000 °C for nuclei growth. Oxygen precipitates were counted under microscope on the cleaved sample surface after preferential etching. Lightly doped silicon samples were also included, as reference. Our results show that even in heavily arsenic doped silicon the oxygen precipitation is a strong function of the initial oxygen concentration, similar to what has been observed for lightly doped silicon. In addition, a precipitation retardation effect is observed in the arsenic doped samples when the dopant concentration is higher than 1.7×1019 cm-3 compared to lightly doped samples with the same initial oxygen content and crystal thermal history. Finally, a long permanence time of the crystal in the temperature range between 450 °C and 750 °C enhances the oxygen precipitation, showing that this is an effective temperature range for oxygen precipitation nucleation in heavily arsenic doped silicon.

  12. Controlling silicon crystallization in aluminum-induced crystallization via substrate plasma treatment

    NASA Astrophysics Data System (ADS)

    Hainey, Mel F.; Innocent-Dolor, Jon-L.; Choudhury, Tanushree H.; Redwing, Joan M.

    2017-03-01

    The effect of reactive ion etching using chlorine or fluorine-based plasmas on aluminum-induced crystallization (AIC) of silicon on fused silica glass substrates was investigated with the goal of chemically modifying the substrate surface and thereby influencing the crystallization behavior. Chlorine etching of the glass prior to AIC resulted in six times faster silicon crystallization times and smaller grain sizes than films formed on untreated substrates while fluorine etching resulted in crystallization times double than those on untreated surfaces. The differences in crystallization behavior were attributed to changes in surface chemistry and surface energy of the glass as a result of the plasma treatment as supported by X-ray photoelectron spectroscopy and contact angle measurements. The different surface treatments were then combined with optical lithography to control the location of crystallization on the substrate surface to realize the production of patterned polycrystalline silicon films from initially continuous aluminum and silicon.

  13. Crystallized Silicon Nanostructures - Experimental Characterization and Atomistic Simulations

    SciTech Connect

    Agbo, Solomon; Sutta, Pavol; Calta, Pavel; Biswas, Rana; Pan, Bicai

    2014-07-01

    We have synthesized silicon nanocrystalline structures from thermal annealing of thin film amorphous silicon-based multilayers. The annealing procedure that was carried out in vacuum at temperatures up to 1100 °C is integrated in a X-ray diffraction (XRD) setup for real-time monitoring of the formation phases of the nanostructures. The microstructure of the crystallized films is investigated through experimental measurements combined with atomistic simulations of realistic nanocrystalline silicon (nc-Si) models. The multilayers consisting of uniformly alternating thicknesses of hydrogenated amorphous silicon and silicon oxide (SiO2) were deposited by plasma enhanced chemical vapor deposition on crystalline silicon and Corning glass substrates. The crystallized structure consisting of nc-Si structures embedded in an amorphous matrix were further characterized through XRD, Raman spectroscopy, and Fourier transform infrared measurements. We are able to show the different stages of nanostructure formation and how the sizes and the crystallized mass fraction can be controlled in our experimental synthesis. The crystallized silicon structures with large crystalline filling fractions exceeding 50% have been simulated with a robust classical molecular dynamics technique. The crystalline filling fractions and structural order of nc-Si obtained from this simulation are compared with our Raman and XRD measurements.

  14. Study of the crystal structure of silicon nanoislands on sapphire

    SciTech Connect

    Krivulin, N. O. Pirogov, A. V.; Pavlov, D. A.; Bobrov, A. I.

    2015-02-15

    The results of studies of the crystal structure of silicon nanoislands on sapphire are reported. It is shown that the principal defects in silicon nanoislands on sapphire are twinning defects. As a result of the formation of such defects, different crystallographic orientations are formed in silicon nanoislands on sapphire. In the initial stages of the molecular-beam epitaxy of silicon on sapphire, there are two basic orientations: the (001) orientation parallel to the surface and the (001) orientation at an angle of 70° to the surface.

  15. Coherent Josephson phase qubit with a single crystal silicon capacitor

    NASA Astrophysics Data System (ADS)

    Patel, U.; Gao, Y.; Hover, D.; Ribeill, G. J.; Sendelbach, S.; McDermott, R.

    2013-01-01

    We have incorporated a single crystal silicon shunt capacitor into a Josephson phase qubit. The capacitor is derived from a commercial silicon-on-insulator wafer. Bosch reactive ion etching is used to create a suspended silicon membrane; subsequent metallization on both sides is used to form the capacitor. The superior dielectric loss of the crystalline silicon leads to a significant increase in qubit energy relaxation times. T1 times up to 1.6 μs were measured, more than a factor of two greater than those seen in amorphous phase qubits. The design is readily scalable to larger integrated circuits incorporating multiple qubits and resonators.

  16. All-silicon photonic crystal photoconductor on silicon-on-insulator at telecom wavelength.

    PubMed

    Haret, Laurent-Daniel; Checoury, Xavier; Han, Zheng; Boucaud, Philippe; Combrié, Sylvain; De Rossi, Alfredo

    2010-11-08

    We demonstrate an all-silicon photodetector working at telecom wavelength. The device is a simple metal-semiconductor-metal detector fabricated on silicon-on-insulator. A two-dimensional photonic crystal nanocavity (Q=60,000) is used to increase the response that arises from the linear and two-photon absorption of silicon. The responsivity of the detector is about 20 mA/W and its bandwidth is larger than 1 GHz.

  17. Thermal imaging of synchrotron beams on silicon crystals

    SciTech Connect

    Smither, R.K.

    1992-06-01

    Advanced Photon source, a next generation synchrotron source, currently under construction at Argonne National Laboratory, will deliver large thermal loads of 1 to 10 kW to the first optical elements (usually a silicon crystal) in the synchrotron, x-ray beam lines. The first optical elements will distort and attenuate the x-ray beam if they are not extremely well cooled. An infrared camera is used to monitor the temperature distribution of the these first optical elements. This measurement is complicated because the silicon crystal is transparent to the infrared radiation and requires a special approach to the analysis of the data to get a meaningful temperature for the crystal.

  18. Influence of impurity atmosphere on the deformation of silicon crystals

    NASA Astrophysics Data System (ADS)

    Klyuchnik, P. A.; Petukhov, B. V.

    2017-07-01

    The Alexander-Haasen theory, which describes the deformation kinetics of silicon crystals, has been generalized for impurity crystals. The deformation kinetics of an impurity sample is calculated in a wide range of parameters, including the cases of partial and complete entrainment of impurities by moving dislocations. The developed model, despite its simplicity, adequately describes the qualitative transformation of the stress-strain curves of impurity silicon crystals in dependence of the impurity concentration and other material parameters. The manifestation of negative velocity dependence of the yield stress, observed in natural experiments, is analyzed.

  19. Liquid Crystal on Silicon Wavefront Corrector

    NASA Technical Reports Server (NTRS)

    Pouch, John; Miranda, Felix; Wang, Xinghua; Bos, Philip, J.

    2004-01-01

    A low cost, high resolution, liquid crystal on silicon, spatial light modulator has been developed for the correction of huge aberrations in an optical system where the polarization dependence and the chromatic nature are tolerated. However, the overall system performance suggests that this device is also suitable for real time correction of aberration in human eyes. This device has a resolution of 1024 x 768, and is driven by an XGA display driver. The effective stroke length of the device is 700 nm and 2000 nm for the visible and IR regions of the device, respectively. The response speeds are 50 Hz and 5 Hz, respectively, which are fast enough for real time adaptive optics for aberrations in human eyes. By modulating a wavefront of 2 pi, this device can correct for arbitrary high order wavefront aberrations since the 2-D pixel array is independently controlled by the driver. The high resolution and high accuracy of the device allow for diffraction limited correction of the tip and tilt or defocus without an additional correction loop. We have shown that for every wave of aberration, an 8 step blazed grating is required to achieve high diffraction efficiency around 80%. In light of this, up to 125 waves peak to valley of tip and tilt can be corrected if we choose the simplest aberration. Corrections of 34 waves of aberration, including high order Zernicke terms in a high magnification telescope, to diffraction limited performance (residual wavefront aberration less than 1/30 lambda at 632.8 nm) have been observed at high efficiency.

  20. Advanced crystallization techniques of 'solar grade' silicon

    NASA Astrophysics Data System (ADS)

    Gasparini, M.; Calligarich, C.; Rava, P.; Sardi, L.; Alessandri, M.; Redaelli, F.; Pizzini, S.

    Microstructural, electrical and photo-voltaic characteristics of polycrystal line silicon solar cells fabricated with silicon ingots containing 5, 100 and 500 ppmw iron are reported and discussed. All silicon ingots were grown by the directional solidification technique in graphite or special quartz molds and doped intentionally with iron, in order to evaluate the potentiality of the D.S. technique when employed with solar silicon feedstocks. Results indicate that structural breakdown limits the amount of the ingot which is usable for solar cells fabrication, but also that efficiencies in excess of 10 percent are obtained using the 'good' region of the ingot.

  1. Room Temperature Crystallization of Hydroxyapatite in Porous Silicon Structures.

    PubMed

    Santana, M; Estevez, J O; Agarwal, V; Herrera-Becerra, R

    2016-12-01

    Porous silicon (PS) substrates, with different pore sizes and morphology, have been used to crystallize hydroxyapatite (HA) nano-fibers by an easy and economical procedure using a co-precipitation method at room temperature. In situ formation of HA nanoparticles, within the meso- and macroporous silicon structure, resulted in the formation of nanometer-sized hydroxyapatite crystals on/within the porous structure. The X-ray diffraction technique was used to determine the tetragonal structure of the crystals. Analysis/characterization demonstrates that under certain synthesis conditions, growth and crystallization of hydroxyapatite layer on/inside PS can be achieved at room temperature. Such composite structures expand the possibility of designing a new bio-composite material based on the hydroxyapatite and silicon synthesized at room temperature.

  2. Silicon Materials Research on Growth Processes, Impurities, and Defects

    SciTech Connect

    Ciszek, T. F.; Wang, T. H.; Page, M. R.; Landry. M. D.; Bauer, R. E.

    2003-05-01

    Research progress on silicon crystal growth processes for photovoltaic applications and defect and impurity effects on PV performance is presented. Growth processes, in addition to thin-film silicon growth, include techniques for silicon-feedstock generation and a method for rapid, replenished Czochralski growth. We have produced research samples of silicon with low and very high dislocation densities for collaborative research with other institutes, and have also made samples with varying amounts of incorporated nitrogen and oxygen, again, for collaborative studies with university researchers, concerning the effects of these impurities on mechanical strength. Transition-metal doping of silicon for understanding metallic impurity effects on lifetime and cell performance is ongoing.

  3. Friction and deformation behavior of single-crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1977-01-01

    Friction and deformation studies were conducted with single-crystal silicon carbide in sliding contact with diamond. When the radius of curvature of the spherical diamond rider was large (0.3), deformation of silicon carbide was primarily elastic. Under these conditions the friction coefficient was low and did not show a dependence on the silicon carbide orientation. Further, there was no detectable cracking of the silicon carbide surfaces. When smaller radii of curvature of the spherical diamond riders (0.15 and 0.02 mm) or a conical diamond rider was used, plastic grooving occured and the silicon carbide exhibited anisotropic friction and deformation behavior. Under these conditions the friction coefficient depended on load. Anisotropic friction and deformation of the basal plane of silicon carbide was controlled by the slip system. 10101120and cleavage of1010.

  4. A silicon sheet casting experiment. [for solar cell water production

    NASA Technical Reports Server (NTRS)

    Bickler, D. B.; Sanchez, L. E.; Sampson, W. J.

    1980-01-01

    The casting of silicon blanks for solar cells directly without slicing is an exciting concept. An experiment was performed to investigate the feasibility of developing a machine that casts wafers directly. A Czochralski furnace was modified to accept a graphite ingot-simulating fixture. Silicon was melted in the middle of the ingot simulator in a boron nitride mold. Sample castings showed reasonable crystal size. Solar cells were made from the cast blanks. The performance is reported.

  5. A silicon sheet casting experiment. [for solar cell water production

    NASA Technical Reports Server (NTRS)

    Bickler, D. B.; Sanchez, L. E.; Sampson, W. J.

    1980-01-01

    The casting of silicon blanks for solar cells directly without slicing is an exciting concept. An experiment was performed to investigate the feasibility of developing a machine that casts wafers directly. A Czochralski furnace was modified to accept a graphite ingot-simulating fixture. Silicon was melted in the middle of the ingot simulator in a boron nitride mold. Sample castings showed reasonable crystal size. Solar cells were made from the cast blanks. The performance is reported.

  6. Electrical Control of Silicon Photonic Crystal Cavity by Graphene

    DTIC Science & Technology

    2012-01-01

    Electrical Control of Silicon Photonic Crystal Cavity by Graphene Arka Majumdar,†,‡,∥ Jonghwan Kim,†,∥ Jelena Vuckovic,‡ and Feng Wang...of electronics and photonics . The combination of graphene with photonic crystals is promising for electro-optic modulation. In this paper, we...demonstrate that by electrostatic gating a single layer of graphene on top of a photonic crystal cavity, the cavity resonance can be changed significantly. A

  7. Silicon and polymer nanophotonic devices based on photonic crystals

    NASA Astrophysics Data System (ADS)

    Jiang, Wei; Jiang, Yongqiang; Gu, Lanlan; Wang, Li; Chen, Xiaonan; Chen, Ray T.

    2006-02-01

    Photonic crystals (PhCs) provide a promising nanophotonic platform for developing novel optoelectronic devices with significantly reduced device size and power consumption. Silicon nanophotonics is anticipated to play a pivotal role in the future nano-system integration owing to the maturity of sub-micron silicon complementary metal oxide semiconductor (CMOS) technology. An ultra-compact silicon modulator was experimentally demonstrated based on silicon photonic crystal waveguides. Modulation operation was achieved by carrier injection into an 80-micron-long silicon PhC waveguide of a Mach-Zehnder interferometer (MZI) structure. The driving current to obtain a phase shift of pi across the active region was as low as 0.15 mA, owing to slow light group velocity in PhC waveguides. The modulation depth was 92%. The electrode between the two waveguide arms of the MZI structure was routed to the space outside the MZI. In real devices, this planarized routing design would be essential to integrating the silicon modulator with electrical driving circuitry on a single silicon chip. For laboratory test, this routing scheme also eliminated the need of placing a bulky pad between the two arms and gave our modulator a distinctive slim profile and a much smaller footprint. Polymeric photonic crystals were designed for superprism based laser beam steering applications, and were fabricated by nano-imprint and other techniques.

  8. Process Research on Polycrystalline Silicon Material (PROPSM)

    NASA Technical Reports Server (NTRS)

    Culik, J. S.

    1983-01-01

    The performance limiting mechanisms in large grain (greater than 1-2 mm in diameter) polycrystalline silicon was investigated by measuring the illuminated current voltage (I-V) characteristics of the minicell wafer set. The average short circuit current on different wafers is 3 to 14 percent lower than that of single crystal Czochralski silicon. The scatter was typically less than 3 percent. The average open circuit voltage is 20 to 60 mV less than that of single crystal silicon. The scatter in the open circuit voltage of most of the polycrystalline silicon wafers was 15 to 20 mV, although two wafers had significantly greater scatter than this value. The fill factor of both polycrystalline and single crystal silicon cells was typically in the range of 60 to 70 percent; however several polycrystalline silicon wafers have fill factor averages which are somewhat lower and have a significantly larger degree of scatter.

  9. Cost of Czochralski wafers as a function of diameter

    NASA Technical Reports Server (NTRS)

    Leipold, M. H.; Radics, C.; Kachare, A.

    1980-01-01

    The impact of diameter in the range of 10 to 15 cm on the cost of wafers sliced from Czochralski ingots was analyzed. Increasing silicon waste and decreasing ingot cost with increasing ingot size were estimated along with projected costs. Results indicate a small but continuous decrease in sheet cost with increasing ingot size in this size range. Sheet costs including silicon are projected to be $50 to $60/sq m (1980 $) depending upon technique used.

  10. Cost of Czochralski wafers as a function of diameter

    SciTech Connect

    Leipold, M.H.; Radics, C.; Kachare, A.

    1980-02-15

    The impact of diameter in the range of 10 to 15 cm on the cost of wafers sliced from Czochralski ingots is analyzed. Increasing silicon waste and decreasing ingot cost with increasing ingot size are estimated along with projected costs. Results indicate a small but continuous decrease in sheet cost with increasing ingot size in this size range. Sheet costs including silicon are projected to be $50 to $60/m/sup 2/ (1980 $) depending upon technique used.

  11. Application of enthalpy model for floating zone silicon crystal growth

    NASA Astrophysics Data System (ADS)

    Krauze, A.; Bergfelds, K.; Virbulis, J.

    2017-09-01

    A 2D simplified crystal growth model based on the enthalpy method and coupled with a low-frequency harmonic electromagnetic model is developed to simulate the silicon crystal growth near the external triple point (ETP) and crystal melting on the open melting front of a polycrystalline feed rod in FZ crystal growth systems. Simulations of the crystal growth near the ETP show significant influence of the inhomogeneities of the EM power distribution on the crystal growth rate for a 4 in floating zone (FZ) system. The generated growth rate fluctuations are shown to be larger in the system with higher crystal pull rate. Simulations of crystal melting on the open melting front of the polycrystalline rod show the development of melt-filled grooves at the open melting front surface. The distance between the grooves is shown to grow with the increase of the skin-layer depth in the solid material.

  12. Crystallization behavior of silicon quantum dots in a silicon nitride matrix.

    PubMed

    Ha, Rin; Kim, Shinho; Kim, Hyun Jong; Lee, Jung Chul; Bae, Jong-Seong; Kim, Yangdo

    2012-02-01

    Silicon quantum dot superlattice was fabricated by alternating deposition of silicon rich nitride (SRN) and Si3N4 layers using RF magnetron co-sputtering. Samples were then annealed at temperatures between 800 and 1,100 degrees C and characterized by grazing incident X-ray diffraction (GIXRD), transmission electron microscopy (TEM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). GIXRD and Raman analyses show that the formation of silicon quantum dots occurs with annealing above 1,100 degrees C for at least 60 minutes. As the annealing time increased the crystallization of silicon quantum dots was also increased. TEM images clearly showed SRN/Si3N4 superlattice structure and silicon quantum dots formation in SRN layers after annealing at 1,100 degrees C for more than 60 minutes. The changes in FTIR transmission spectra observed with annealing condition corresponded to the configuration of Si-N bonds. Crystallization of silicon quantum dots in a silicon nitride matrix started stabilizing after 60 minutes' annealing and approached completion after 120 minutes'. The systematic investigation of silicon quantum dots in a silicon nitride matrix and their properties for solar cell application are presented.

  13. The lattice parameter of highly pure silicon single crystals

    NASA Astrophysics Data System (ADS)

    Becker, P.; Scyfried, P.; Siegert, H.

    1982-08-01

    From crystal to crystal comparison, the d 220 lattice spacing in PERFX and WASO silicon crystals used in the only two existing absolute measurements have been found to be equal within ±2×10-7 d 220. This demonstrates that generic variabilities of the two crystals account only for a small part of the 1.8×10-6 d 220 difference in the two absolute measurements. In a new series of 336 single measurements, our d 220 value reported recently has been confirmed within ±2×10-8 d 220. From these results we derive the following lattice parameter for highly pure silicon single crystals: a 0=(543 102.018±0.034) fm (at 22.5°C, in vacuum).

  14. Kinetics of thermal donor generation in silicon

    NASA Technical Reports Server (NTRS)

    Mao, B.-Y.; Lagowski, J.; Gatos, H. C.

    1984-01-01

    The generation kinetics of thermal donors at 450 C in Czochralski-grown silicon was found to be altered by high-temperature preannealing (e.g., 1100 C for 30 min). Thus, when compared with as-grown Si, high-temperature preannealed material exhibits a smaller concentration of generated thermal donors and a faster thermal donor saturation. A unified mechanism of nucleation and oxygen diffusion-controlled growth (based on solid-state plate transformation theory) is proposed to account for generation kinetics of thermal donors at 450 C, in as-grown and high-temperature preannealed Czochralski silicon crystals. This mechanism is consistent with the main features of the models which have been proposed to explain the formation of oxygen thermal donors in silicon.

  15. Quantification of the Void Volume in Single-Crystal Silicon.

    PubMed

    D'Agostino, Giancarlo; Di Luzio, Marco; Mana, Giovanni; Martino, Luca; Oddone, Massimo; Sasso, Carlo Paolo

    2016-12-06

    This paper investigates the use of a method based on Cu decoration and neutron activation to determine the total volume of voids in a silicon single crystal. A measurement protocol was developed and tested in an experiment carried out with a 5 cm(3) volume and 10 g mass high-purity natural silicon sample. The few percent uncertainty reached in the determination of the Cu concentration, at a 10(14) cm(-3) level, makes this method a candidate to set an upper limit to the concentration of the vacancies contributing to the void volume in the enriched silicon material used to determine the Avogadro constant.

  16. Growth of 450 mm diameter semiconductor grade silicon crystals

    NASA Astrophysics Data System (ADS)

    Lu, Zheng; Kimbel, Steven

    2011-03-01

    Research and development of the next generation 450 mm semiconductor grade silicon crystal and related technology have been carried out in MEMC following the company's philosophy to stay one generation ahead on research and development. The first 450 mm dislocation free crystal was grown in early 2009 and the first 450 mm semiconductor wafer was produced shortly after. General challenges in crystal growth process, puller, and hot zone designs, as well as control, automation, and handling are discussed in this paper. General considerations on working with customers and equipment manufacturers on fundamental crystal and wafer quality characteristics are also discussed.

  17. Silicon-based photonic crystal waveguides and couplers

    NASA Astrophysics Data System (ADS)

    Farrell, Stephen G.

    2008-10-01

    Most commercial photonics-related research and development efforts currently fall into one or both of the following technological sectors: silicon photonics and photonic integrated circuits. Silicon photonics [18] is the field concerned with assimilating photonic elements into the well-established CMOS VLSI architecture and IC manufacturing. The convergence of these technologies would be mutually advantageous: photonic devices could increase bus speeds and greatly improve chip-to-chip and board-to-board data rates, whereas photonics, as a field, would benefit from mature silicon manufacturing and economies of scale. On the other hand, those in the photonic integrated circuit sector seek to continue the miniaturization of photonic devices in an effort to obtain an appreciable share of the great windfall of profits that occur when manufacturing, packaging, and testing costs are substantially reduced by shrinking photonic elements to chip-scale dimensions. Integrated photonics companies may [12] or may not [34] incorporate silicon as the platform. In this thesis, we seek to further develop a technology that has the potential to facilitate the forging of silicon photonics and photonic integrated circuits: photonic crystals on silicon-on-insulator substrates. We will first present a brief overview of photonic crystals and their physical properties. We will then detail a finely-tuned procedure for fabricating two-dimensional photonic crystal in the silicon-on-insulator material system. We will then examine transmission properties of our fabricated devices including propagation loss, group index dispersion, and coupling efficiency of directional couplers. Finally, we will present a description of a system for adiabatically tapering optical fibers and the results of using tapered fibers for efficiently coupling light into photonic crystal devices.

  18. Microchannel water cooling of silicon x-ray monochromator crystals

    SciTech Connect

    Arthur, J.; Tompkins, W.H.; Troxel, C. Jr. ); Contolini, R.J.; Schmitt, E. ); Bilderback, D.H.; Henderson, C.; White, J.; Settersten, T. )

    1992-01-01

    The use in silicon x-ray monochromator crystals of water cooling channels with dimensions optimized for efficient heat transfer from silicon to water has been investigated. Such channels are typically about 40 {mu}m wide and 400 {mu}m deep. Procedures have been found for reliably producing microchannel-cooled crystals with very small amounts of residual strain. These crystals have been tested at a high-power wiggler beam line at the Cornell High Energy Synchrotron Source, using an x-ray beam having total power in excess of 250 W and normal-incidence power density greater than 5 W/mm{sup 2}. Under these conditions, the surface-temperature rise of a typical microchannel-cooled crystal was less than 5 {degree}C, and degradation of the (111) rocking curve at 12 keV was very slight. The cooling efficiency is consistent with analytic calculations.

  19. Investigation of Backside Textures for Genesis Solar Wind Silicon Collectors

    NASA Technical Reports Server (NTRS)

    Gonzalez, C. P.; Burkett, P. J.; Rodriguez, M. C.; Allton, J. H.

    2014-01-01

    Genesis solar wind collectors were comprised of a suite of 15 types of ultrapure materials. The single crystal, pure silicon collectors were fabricated by two methods: float zone (FZ) and Czochralski (CZ). Because of slight differences in bulk purity and surface cleanliness among the fabrication processes and the specific vendor, it is desirable to know which variety of silicon and identity of vendor, so that appropriate reference materials can be used. The Czochralski method results in a bulk composition with slightly higher oxygen, for example. The CZ silicon array wafers that were Genesis-flown were purchased from MEMC Electronics. Most of the Genesis-flown FZ silicon was purchased from Unisil and cleaned by MEMC, although a few FZ wafers were acquired from International Wafer Service (IWS).

  20. Structural and photoluminescence studies on europium-doped lithium tetraborate (Eu:Li2B4O7) single crystal grown by microtube Czochralski (μT-Cz) technique

    NASA Astrophysics Data System (ADS)

    A, Kumaresh; R, Arun Kumar; N, Ravikumar; U, Madhusoodanan; B, S. Panigrahi; K, Marimuthu; M, Anuradha

    2016-05-01

    Rare earth europium (Eu3+)-doped lithium tetraborate (Eu:Li2B4O7) crystal is grown from its stoichiometric melt by microtube Czochralski pulling technique (μT-Cz) for the first time. The grown crystals are subjected to powder x-ray diffraction (PXRD) analysis which reveals the tetragonal crystal structure of the crystals. UV-vis-NIR spectral analysis is carried out to study the optical characteristics of the grown crystals. The crystal is transparent in the entire visible region, and the lower cutoff is observed to be at 304 nm. The existence of BO3 and BO4 bonding structure and the molecular associations are analyzed by Fourier transform infrared (FTIR) spectroscopy. The results of excitation and emission-photoluminescence spectra of europium ion incorporated in lithium tetraborate (LTB) single crystal reveal that the observations of peaks at 258, 297, and 318 nm in the excitation spectra and peaks at 579, 591, 597, 613, and 651 nm are observed in the emission spectra. The chromaticity coordinates are calculated from the emission spectra, and the emission intensity of the grown crystal is characterized through a CIE 1931 (Commission International d’Eclairage) color chromaticity diagram. Project supported by the Department of Science and Technology-Science and Engineering Research Board (Grant No. SR/S2/LOP-0012/2011), the Government of India for Awarding Major Research Project, the University Grants Commission-Department of Atomic Research-Consortium for Scientific Research (Grant No. CSR-KN/CSR-63/2014-2015/503), and the Kalpakkam and Indore, India.

  1. Excimer laser crystallization of amorphous silicon on metallic substrate

    NASA Astrophysics Data System (ADS)

    Delachat, F.; Antoni, F.; Slaoui, A.; Cayron, C.; Ducros, C.; Lerat, J.-F.; Emeraud, T.; Negru, R.; Huet, K.; Reydet, P.-L.

    2013-06-01

    An attempt has been made to achieve the crystallization of silicon thin film on metallic foils by long pulse duration excimer laser processing. Amorphous silicon thin films (100 nm) were deposited by radiofrequency magnetron sputtering on a commercial metallic alloy (N42-FeNi made of 41 % of Ni) coated by a tantalum nitride (TaN) layer. The TaN coating acts as a barrier layer, preventing the diffusion of metallic impurities in the silicon thin film during the laser annealing. An energy density threshold of 0.3 J cm-2, necessary for surface melting and crystallization of the amorphous silicon, was predicted by a numerical simulation of laser-induced phase transitions and witnessed by Raman analysis. Beyond this fluence, the melt depth increases with the intensification of energy density. A complete crystallization of the layer is achieved for an energy density of 0.9 J cm-2. Scanning electron microscopy unveils the nanostructuring of the silicon after laser irradiation, while cross-sectional transmission electron microscopy reveals the crystallites' columnar growth.

  2. Kinetics of silicon precipitation in a directionally crystallized binary aluminum-silicon alloy

    NASA Astrophysics Data System (ADS)

    Egorova, L. M.; Korchunov, B. N.; Osipov, V. N.; Bershtein, V. A.; Nikanorov, S. P.

    2013-12-01

    The precipitation of silicon atoms in aluminum in an Al-Si alloy has been studied using differential scanning calorimetry. The alloys containing 8, 13, and 15 wt % silicon were obtained by directional solidification of a ribbon pulled from the melt through a shaper by the Stepanov method at a rate of about 103 μm/s. From the characteristics of the exothermic effects observed in the temperature range 430-650 K, it has been found that the precipitation process leading to the formation of the Guinier-Preston zones occurs with the effective activation energy of 75 kJ/mol, and its intensity decreases with increasing silicon content in the alloy from 8 wt % to the eutectic content. The effect correlates with a decrease in the volume fraction of dendrites of the primary α-Al crystals in the alloy. It can be assumed that the precipitation occurs in the dendrite primary crystals of the solid solution. Based on this assumption, it has been concluded that, during directional solidification of an aluminum-silicon alloy at a rate of 103 μm/s, the metastable solid solution of silicon in aluminum, in which silicon atoms of the metallic lattice are transformed into clusters with covalent bonding forces, is formed during the dendrite growth of the primary crystals.

  3. Crystal Growth of Germanium-Silicon Alloys on the ISS

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.; Croell, A.

    2015-01-01

    A series of Ge(1-x)Si(x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. The experiments are part of the investigation "Influence of Containment on the Growth of Silicon-Germanium" (ICESAGE). The primary objective of the research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon alloy crystals. A comparison will be made between crystals grown by the normal and "detached" Bridgman methods and the ground-based float zone technique. Crystals grown without being in contact with a container have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. "Detached" or "dewetted" Bridgman growth is similar to regular Bridgman growth in that most of the melt is in contact with the crucible wall, but the crystal is separated from the wall by a small gap, typically of the order of 10-100 microns. Long duration reduced gravity is essential to test the proposed theory of detached growth. Detached growth requires the establishment of a meniscus between the crystal and the ampoule wall. This meniscus can exist over a much larger range of processing parameters in microgravity and the meniscus is more stable under microgravity conditions. The plans for the flight experiments will be described.

  4. Silicon crystal surface temperature: Computational and radiometric studies

    SciTech Connect

    Khounsary, A.M.; Kuzay, T.M.; Forster, G.A.

    1988-12-01

    The surface temperature of the three-channel, gallium cooled Cornell silicon crystal was evaluated for the given system configuration and specifications. The THTB thermal-hydraulic program is used for the numerical solution of the problem, and the results are to be compared with the radiometric measurements obtained at Cornell.

  5. Microwave Induced Direct Bonding of Single Crystal Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Budraa, N. K.; Jackson, H. W.; Barmatz, M.

    1999-01-01

    We have heated polished doped single-crystal silicon wafers in a single mode microwave cavity to temperatures where surface to surface bonding occurred. The absorption of microwaves and heating of the wafers is attributed to the inclusion of n-type or p-type impurities into these substrates. A cylindrical cavity TM (sub 010) standing wave mode was used to irradiate samples of various geometry's at positions of high magnetic field. This process was conducted in vacuum to exclude plasma effects. This initial study suggests that the inclusion of impurities in single crystal silicon significantly improved its microwave absorption (loss factor) to a point where heating silicon wafers directly can be accomplished in minimal time. Bonding of these substrates, however, occurs only at points of intimate surface to surface contact. The inclusion of a thin metallic layer on the surfaces enhances the bonding process.

  6. Distribution of radiative crystal imperfections through a silicon ingot

    SciTech Connect

    Flø, A. Burud, I.; Kvaal, K.; Olsen, E.; Søndenå, R.

    2013-11-15

    Crystal imperfections limit the efficiency of multicrystalline silicon solar cells. Recombination through traps is more prominent in areas with high density of crystal imperfections. A method to visualize the distribution of radiative emission from Shockley Read Hall recombination in silicon is demonstrated. We use hyperspectral photoluminescence, a fast non-destructive method, to image radiatively active recombination processes on a set of 50 wafers through a silicon block. The defect related emission lines D1 and D2 may be detected together or alone. The D3 and D4 seem to be correlated if we assume that an emission at the similar energy as D3 (VID3) is caused by a separate mechanism. The content of interstitial iron (Fe{sub i}) correlates with D4. This method yields a spectral map of the inter band gap transitions, which opens up for a new way to characterize mechanisms related to loss of efficiency for solar cells processed from the block.

  7. Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals

    PubMed Central

    Ptasinski, Joanna; Khoo, Iam-Choon; Fainman, Yeshaiahu

    2014-01-01

    In this work we explore the negative thermo-optic properties of liquid crystal claddings for passive temperature stabilization of silicon photonic integrated circuits. Photonic circuits are playing an increasing role in communications and computing, but they suffer from temperature dependent performance variation. Most existing techniques aimed at compensation of thermal effects rely on power hungry Joule heating. We show that integrating a liquid crystal cladding helps to minimize the effects of a temperature dependent drift. The advantage of liquid crystals lies in their high negative thermo-optic coefficients in addition to low absorption at the infrared wavelengths. PMID:28788565

  8. Growth conditions, structure, Raman characterization and optical properties of Sm-doped (LuxGd1-x)2SiO5 single crystals grown by the Czochralski method

    NASA Astrophysics Data System (ADS)

    GŁowacki, MichaŁ; Dominiak-Dzik, Grażyna; Ryba-Romanowski, Witold; Lisiecki, RadosŁaw; Strzęp, Adam; Runka, Tomasz; Drozdowski, MirosŁaw; Domukhovski, Viktor; Diduszko, Ryszard; Berkowski, Marek

    2012-02-01

    The (LuxGd0.995-xSm0.005)2SiO5 single crystals with x=0.095, 0.11, 0.15, 0.17, 0.19 0.35 and 0.5 were grown by the Czochralski method. Structural properties were investigated by X-ray diffraction measurements. Unit cell parameters and cell volume were determined by the Rietveld refinement of the collected X-ray powder spectra. The segregation features between Gd and Lu were estimated and analyzed. Vibrational properties of the solid solutions were analyzed on the basis of polarized Raman spectra acquired at 300-875 K temperature range. Absorption and emission spectra of Sm3+ ion in the crystals with different composition were analyzed in the terms of dopant energy levels, oscillator strengths of transitions and spectral features of luminescence bands in the visible range. Both structural and optical investigations revealed that change of Lu3+ content in (LuxGd0.995-xSm0.005)2SiO5 solid solution crystals induces the phase transition from C2/c (Lu2SiO5) to P21/c (Gd2SiO5) structure. It was found that the break of LSO to GSO-type structure occurs at 0.15

  9. Defects in Amorphous Silicon: Dynamics and Role on Crystallization.

    NASA Astrophysics Data System (ADS)

    Shin, Jung Hoon

    Defects play a crucial role in determining the properties of many materials of scientific and technological interest. With ion irradiation, it is possible to controllably inject defects, and thus carefully study the dynamics of defect creation and annihilation, as well as the effects such defect injection has on materials properties and phase transformations. Amorphous silicon is a model system for the study of amorphous solids characterized as continuous random networks. In hydrogenated form, it is an important material for semiconductor devices such as solar cells and thin film transistors. It is the aim of this thesis to elucidate the dynamics of defects in an amorphous silicon matrix, and the role such defects can play on crystallization of amorphous silicon. In the first chapter, the concept of a continuous random network that characterizes amorphous silicon is presented as an introduction to amorphous silicon. Structural relaxation, or annihilation of non-equilibrium defects in an amorphous matrix, is introduced. Also developed are the concept of the activation energy spectrum theory for structural relaxation of amorphous solids and the density of relaxation states. In the second chapter, the density of relaxation states for the structural relaxation of amorphous silicon is measured by measuring changes in electrical conductivity, using ion irradiation and thermal anneal to create and annihilate defects, respectively. A new quantitative model for defect creation and annihilation, termed the generalized activation energy spectrum theory, is developed in Chapter 3, and is found to be superior to previous models in describing defect dynamics in amorphous silicon. In Chapter 4, the effect of irradiation on the crystallization of amorphous silicon is investigated. It is found that irradiation affects crystallization even when the growth kinetics of crystal grains is unaffected, and that defects injected into amorphous matrix by irradiation probably play a role in

  10. Stability limits for the horizontal ribbon growth of silicon crystals

    NASA Astrophysics Data System (ADS)

    Daggolu, Parthiv; Yeckel, Andrew; Bleil, Carl E.; Derby, Jeffrey J.

    2013-01-01

    A rigorous, thermal-capillary model, developed to couple heat transfer, melt convection and capillary physics, is employed to assess stability limits of the HRG system for growing silicon ribbons. Extending the prior understanding of this process put forth by Daggolu et al. [Thermal-capillary analysis of the horizontal ribbon growth of silicon crystals, Journal of Crystal Growth 355 (2012) 129-139], model results presented here identify additional failure mechanisms, including the bridging of crystal onto crucible, the spilling of melt from the crucible, and the undercooling of melt at the ribbon tip, that are consistent with prior experimental observations. Changes in pull rate, pull angle, melt height, and other parameters are shown to give rise to limits, indicating that only narrow operating windows exist in multi-dimensional parameter space for stable growth conditions that circumvent these failure mechanisms.

  11. Crystallization of silicon films on glass: a comparison of methods

    SciTech Connect

    Lemons, R.A.; Bosch, M.A.; Herbst, D.

    1983-01-01

    The lure of flat panel displays has stimulated much research on the crystallization of silicon films deposited on large-area transparent substrates. In most respects, fused quartz is ideal. It has high purity, thermal shock resistance, and a softening point above the silicon melting temperature. Unfortunately, fused quartz has such a small thermal expansion that the silicon film cracks as it cools. This problem has been attacked by patterning with islands or moats before and after crystallization, by capping, and by using silicate glass substrates that match the thermal expansion of silicon. The relative merits of these methods are compared. Melting of the silicon film to achieve high mobility has been accomplished by a variety of methods including lasers, electron beams, and strip heaters. For low melting temperature glasses, surface heating with a laser or electron beam is essential. Larger grains are obtained with the high bias temperature, strip heater techniques. The low-angle grain boundaries characteristic of these films may be caused by constitutional undercooling. A model is developed to predict the boundary spacing as a function of scan rate and temperature gradient.

  12. High-Q silicon carbide photonic-crystal cavities

    SciTech Connect

    Lee, Jonathan Y.; Lu, Xiyuan; Lin, Qiang

    2015-01-26

    We demonstrate one-dimensional photonic-crystal nanobeam cavities in amorphous silicon carbide. The fundamental mode exhibits intrinsic optical quality factor as high as 7.69 × 10{sup 4} with mode volume ∼0.60(λ/n){sup 3} at wavelength 1.5 μm. A corresponding Purcell factor value of ∼10{sup 4} is the highest reported to date in silicon carbide optical cavities. The device exhibits great potential for integrated nonlinear photonics and cavity nano-optomechanics.

  13. Can the crystallization rate be independent from the crystallization enthalpy? The case of amorphous silicon.

    PubMed

    Kail, F; Molera, J; Farjas, J; Roura, P; Secouard, C; Roca i Cabarrocas, P

    2012-03-07

    The crystallization enthalpy measured in a large series of amorphous silicon (a-Si) materials varies within a factor of 2 from sample to sample (Kail et al 2011 Phys. Status Solidi RRL 5 361). According to the classical theory of nucleation, this variation should produce large differences in the crystallization kinetics leading to crystallization temperatures and activation energies exceeding 550 °C and 1.7 eV, respectively, the 'standard' values measured for a-Si obtained by self-implantation. In contrast, the observed crystallization kinetics is very similar for all the samples studied and has no correlation with the crystallization enthalpy. This discrepancy has led us to propose that crystallization in a-Si begins in microscopic domains that are almost identical in all samples, independently of their crystallization enthalpy. Probably the existence of microscopic inhomogeneities also plays a crucial role in the crystallization kinetics of other amorphous materials and glasses.

  14. Industry needs for silicon crystals and standards

    NASA Technical Reports Server (NTRS)

    Benson, K. E.

    1981-01-01

    The trend of the device fabrication industry requirement for larger crystals is reviewed. The ranges of properties and uniformities measurement standards needed for resistivity (four-point probe and spreading resistance) and for the chemical composition of oxygen and carbon impurities are presented.

  15. Shock compression of [001] single crystal silicon

    SciTech Connect

    Zhao, S.; Remington, B.; Hahn, E. N.; Kad, B.; Bringa, E. M.; Meyers, M. A.

    2016-03-14

    Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent with dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Furthermore, application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.

  16. Shock compression of [001] single crystal silicon

    DOE PAGES

    Zhao, S.; Remington, B.; Hahn, E. N.; ...

    2016-03-14

    Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent withmore » dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Furthermore, application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.« less

  17. Shock compression of [001] single crystal silicon

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Hahn, E. N.; Kad, B.; Remington, B. A.; Bringa, E. M.; Meyers, M. A.

    2016-05-01

    Silicon is ubiquitous in our advanced technological society, yet our current understanding of change to its mechanical response at extreme pressures and strain-rates is far from complete. This is due to its brittleness, making recovery experiments difficult. High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon (using impedance-matched momentum traps) unveiled remarkable structural changes observed by transmission electron microscopy. As laser energy increases, corresponding to an increase in peak shock pressure, the following plastic responses are are observed: surface cleavage along {111} planes, dislocations and stacking faults; bands of amorphized material initially forming on crystallographic orientations consistent with dislocation slip; and coarse regions of amorphized material. Molecular dynamics simulations approach equivalent length and time scales to laser experiments and reveal the evolution of shock-induced partial dislocations and their crucial role in the preliminary stages of amorphization. Application of coupled hydrostatic and shear stresses produce amorphization below the hydrostatically determined critical melting pressure under dynamic shock compression.

  18. Spark-source mass spectrometric assessment of silicon concentrations in silicon-doped gallium arsenide single crystals.

    PubMed

    Wiedemann, B; Meyer, J D; Jockel, D; Freyhardt, H C; Birkmann, B; Müller, G

    2001-07-01

    The spark-source mass spectrometric assessment of silicon concentrations in silicon-doped vertical-gradient-freeze gallium arsenide is presented. The silicon concentrations determined are compared with the charge-carrier densities measured by means of the Hall effect with van der Pauw symmetry along the axis of a single crystal.

  19. Crystal lattice optimization and new forms of silicon

    NASA Astrophysics Data System (ADS)

    Stucke, David P.

    In Chapter 1 a basic outline of the two main methods used in this thesis is given. A genetic algorithm optimization method based on the concept of natural selection is given. The important factors to consider in creating an effective genetic algorithm search are described. I then give a brief overview of Density Functional Theory (DFT) which is the technique most commonly used to do ab-inito calculations on solid-state systems. The basis for its formulation along with how it is applied to a practical system with some approximations is discussed. In Chapter 2 a description of a genetic search algorithm for optimizing the crystal structure of an infinite crystal is given. This method is applied to a system of colloidal spheres, where the packing density is the figure of merit for structure selection. Our examination of self-assembled multi-component crystals of nanoparticles predicts several new structures with stoichiometries of AB (fused spheres), ABC2, ABC 3, ABC4 and AB2 C2. These new structures have hierarchical layered or linear arrangements that could be useful for functional self-assembled systems. For example, the fused-sphere binary crystal assembles with zig-zag rows of parallel nanowires. The genetic search suceeds while a comparable stochastic algorithm fails to find any structures better than the well-known unary or binary phase-separated systems. Here we describe the algorithm and the results it produces: several new classes of binary and ternary crystals of spherical nanoparticles, including a family of layered perovskite-like systems and an unusual three-dimensional array of parallel zig-zag nanowires. In Chapter 3, We discuss the possibility of constructing new forms of silicon by building in multiple bonds consistent with molecules that have been produced experimentally. We find a dilated diamond crystal lattice containing a silicon-silicon triple bond that is metastable. This structure has very soft vibrational modes that are common in similar

  20. Brittle crack propagation in silicon single crystals

    SciTech Connect

    Brede, M.; Hsia, K.J.; Argon, A.S. )

    1991-07-15

    Viewing the brittle-to-ductile transition of fracture in intrinsically brittle solids as a crack tip initiated critical event of either nucleation of dislocation loops from the crack tip or the motion away of such dislocations from the crack tip, experiments have been devised to measure the critical activation energy of such events by measuring the arrest temperature of cleavage cracks with different velocities in experiments that were conducted on large Si single crystals subjected to a steep temperature gradient. While such experiments can provide precise information that can be related directly to mechanisms of crack tip bifurcation behavior, they are hampered by nontrivial perturbations that must be controlled. Here in the first of a series of communications we discuss the nature of these perturbations in Si single crystals, cleaving either on the {l brace}111{r brace} or the {l brace}110{r brace} planes.

  1. Studies of the Crystallization Process of Aluminum-Silicon Alloys Using a High Temperature Microscope. Thesis

    NASA Technical Reports Server (NTRS)

    Justi, S.

    1985-01-01

    It is shown that primary silicon crystals grow polyhedral in super-eutectic AlSi melts and that phosphorus additives to the melt confirm the strong seeding capacity. Primary silicon exhibits strong dendritic seeding effects in eutectic silicon phases of various silicon alloys, whereas primary aluminum does not possess this capacity. Sodium addition also produces a dendritic silicon network growth in the interior of the sample that is attributed to the slower silicon diffusion velocity during cooling.

  2. Novel silicon crystals and method for their preparation

    NASA Technical Reports Server (NTRS)

    Authier, B.

    1977-01-01

    Plate shaped silicon crystals and their preparation by pouring a silicon melt into a suitable mold and then allowing it to solidify in a temperature gradient were investigated. The production of energy by direct conversion of solar energy into electrical energy by means of solar cells takes on increasing importance. While this type of energy production is already the prevailing form today in the realm of satellite technology, its terrestrial application has thus far encountered strict limitations owing to the high price of such solar cells. Of the greatest interest in this connection are silicon cells. A substantial reduction in the semiconductor material costs and the costs involved in the further processing to make solar cells are prerequisites for a rational market growth for solar energy.

  3. Crystallization Behavior of M97 Series Silicone Cushions

    SciTech Connect

    Chien, A.; DeTeresa, S.; Cohenour, R.; Schnieder, J.; LeMay, J.; Balazs, B.

    2000-09-07

    M97 series siloxanes are poly(dimethyl-diphenyl) siloxanes that are reinforced through a mixture of precipitated and fumed silica fillers which are blended in through the addition of a short chain polydimethylsiloxane processing aid. M97 silicones exhibit crystallization at -80.25 C by thermal (modulated differential scanning calorimetry) and mechanical (dynamic mechanical analysis) techniques. Isothermal dynamic mechanical analysis experiments illustrated that crystallization occurred over a 1.8 hour period in silica-filled systems and 2.8 hours in unfilled systems. The onset of crystallization typically occurred after a 30 minute incubation/nucleation period. {gamma}-radiation caused the crystallization rate to decrease proportionally with dosage, but did not decrease the amount of crystallization that ultimately occurred. Irradiation in vacuum resulted in slower overall crystallization rates compared to air irradiation due to increased crosslinking of the polymer matrix under vacuum. Modulated differential scanning calorimetry contrasted the crystallization and melting behavior of pure PDMS versus the M97 base polymer and helped determine which component of the composite was the origin of the crystallization phenomena.

  4. Schottky diode silicon liquid-crystal light valve

    NASA Astrophysics Data System (ADS)

    Sayyah, Keyvan; Efron, Uzi; Forber, Richard A.; Goodwin, Norman W.; Reif, Philip G.

    1991-06-01

    The authors report the operation of the Hughes Schottky diode-based silicon liquid crystal light valve (SLV) using readout light in the visible region. Limiting resolutions of 28 lp/mm limited by the Schottky diode periodicity, contrast ratios of >100:1, visible input light sensitivities of better than 50 (mu) W/cm2, and response times as fast as 5 ms have been measured. Both standard twisted nematic and homeotropically-aligned liquid crystal configurations have been utilized. The main parameter of this device is the leakage current of the Schottky diodes.

  5. Crystallization of silicon carbide thin films by pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    De Cesare, G.; La Monica, S.; Maiello, G.; Masini, G.; Proverbio, E.; Ferrari, A.; Chitica, N.; Dinescu, M.; Alexandrescu, R.; Morjan, I.; Rotiu, E.

    1996-10-01

    Pulsed laser irradiation at low incident fluences was demonstrated to be effective for the crystallization of amorphous hydrogenated silicon carbide (a-SiC:H) films deposited on Si wafers. The amorphous films, with a carbon content in the range 30-50%, were deposited on (100) Si wafers by low temperature plasma enhanced chemical vapor deposition (PECVD). The crystallization treatment was carried out by a multipulse KrF excimer laser. The crystallinity modifications induced by the laser treatment were evidenced by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction. An important increase of the microhardness was evidenced as an effect of the laser treatment.

  6. Point defects generated by oxidation of silicon crystal surface

    NASA Astrophysics Data System (ADS)

    Suezawa, M.; Yamamoto, Y.; Suemitsu, M.; Yonenaga, I.

    2009-12-01

    To study the generation of interstitials and vacancies due to oxidation of silicon crystals, we applied a quenching method, namely, oxidation at high temperatures in mixed gases of water vapor and hydrogen gas followed by the quenching into water. Contrary to our expectation that the interstitial concentration is high, the vacancy concentration generated due to the short period of oxidation is higher than that of the thermal equilibrium concentration.

  7. Simulation of Electronic Center Formation by Irradiation in Silicon Crystals

    NASA Astrophysics Data System (ADS)

    Yeritsyan, H. N.; Sahakyan, A. A.; Grigoryan, N. E.; Harutyunyan, V. V.; Tsakanov, V. M.; Grigoryan, B. A.; Yeremyan, A. S.; Amatuni, G. A.

    2017-02-01

    We present the results of a study on localized electronic centers formed in crystals by external influences (impurity introduction and irradiation). The main aim is to determine the nature of these centers in the forbidden gap of the energy states of the crystal lattice. For the case of semiconductors, silicon (Si) was applied as model material to determine the energy levels and concentration of radiation defects for application to both doped and other materials. This method relies on solving the appropriate equation describing the variation of the charge carrier concentration as a function of temperature n( T) for silicon crystals with two different energy levels and for a large set of N 1, N 2 (concentrations of electronic centers at each level), and n values. A total of almost 500 such combinations were found. For silicon, energy level values of ɛ 1 = 0.22 eV and ɛ 2 = 0.34 eV were used for the forbidden gap (with corresponding slopes determined from experimental temperature-dependent Hall-effect measurements) and compared with photoconductivity spectra. Additionally, it was shown that, for particular correlations among N 1, N 2, and n, curve slopes of ɛ 1/2 = 0.11 eV, ɛ 2/2 = 0.17 eV, and α = 1/2( ɛ 1 + ɛ 2) = 0.28 eV also apply. Comparison between experimental results for irradiation of silicon crystals by 3.5-MeV energy electrons and Co60 γ-quanta revealed that the n( T) curve slopes do not always coincide with the actual energy levels (electronic centers).

  8. Phase-sensitive amplification in silicon photonic crystal waveguides.

    PubMed

    Zhang, Yanbing; Husko, Chad; Schröder, Jochen; Lefrancois, Simon; Rey, Isabella H; Krauss, Thomas F; Eggleton, Benjamin J

    2014-01-15

    We experimentally demonstrate phase-sensitive amplification in a silicon photonic crystal waveguide based on pump-degenerate four-wave mixing. An 11 dB phase-extinction ratio is obtained in a record compact 196 μm nanophotonic device due to broadband slow light, in spite of the presence of two-photon absorption and free carriers. Numerical calculations show good agreement with the experimental results.

  9. Silicon single-crystal cryogenic optical resonator.

    PubMed

    Wiens, Eugen; Chen, Qun-Feng; Ernsting, Ingo; Luckmann, Heiko; Rosowski, Ulrich; Nevsky, Alexander; Schiller, Stephan

    2014-06-01

    We report on the demonstration and characterization of a silicon optical resonator for laser frequency stabilization, operating in the deep cryogenic regime at temperatures as low as 1.5 K. Robust operation was achieved, with absolute frequency drift less than 20 Hz over 1 h. This stability allowed sensitive measurements of the resonator thermal expansion coefficient (α). We found that α=4.6×10(-13)  K(-1) at 1.6 K. At 16.8 K α vanishes, with a derivative equal to -6×10(-10)  K(-2). The temperature of the resonator was stabilized to a level below 10 μK for averaging times longer than 20 s. The sensitivity of the resonator frequency to a variation of the laser power was also studied. The corresponding sensitivities and the expected Brownian noise indicate that this system should enable frequency stabilization of lasers at the low-10(-17) level.

  10. Growth conditions, structure, Raman characterization and optical properties of Sm-doped (Lu{sub x}Gd{sub 1-x}){sub 2}SiO{sub 5} single crystals grown by the Czochralski method

    SciTech Connect

    GLowacki, MichaL; Runka, Tomasz; Drozdowski, MirosLaw; Domukhovski, Viktor; Berkowski, Marek

    2012-02-15

    The (Lu{sub x}Gd{sub 0.995-x}Sm{sub 0.005}){sub 2}SiO{sub 5} single crystals with x=0.095, 0.11, 0.15, 0.17, 0.19 0.35 and 0.5 were grown by the Czochralski method. Structural properties were investigated by X-ray diffraction measurements. Unit cell parameters and cell volume were determined by the Rietveld refinement of the collected X-ray powder spectra. The segregation features between Gd and Lu were estimated and analyzed. Vibrational properties of the solid solutions were analyzed on the basis of polarized Raman spectra acquired at 300-875 K temperature range. Absorption and emission spectra of Sm{sup 3+} ion in the crystals with different composition were analyzed in the terms of dopant energy levels, oscillator strengths of transitions and spectral features of luminescence bands in the visible range. Both structural and optical investigations revealed that change of Lu{sup 3+} content in (Lu{sub x}Gd{sub 0.995-x}Sm{sub 0.005}){sub 2}SiO{sub 5} solid solution crystals induces the phase transition from C2/c (Lu{sub 2}SiO{sub 5}) to P2{sub 1}/c (Gd{sub 2}SiO{sub 5}) structure. It was found that the break of LSO to GSO-type structure occurs at 0.15crystals of Sm{sup 3+}-doped (Lu{sub x}Gd{sub 1-x}){sub 2}SiO{sub 5} solid solutions have been grown by Czochralski method and characterized by various techniques. Crystal structure changes from C2/c to P2{sub 1}/c for composition with 0.15crystal structure causes changes in emission spectra. Highlights: Black-Right-Pointing-Pointer The (Lu{sub x}Gd{sub 1-x}){sub 2}SiO{sub 5} crystals are an alternative to LSO and GSO hosts for applications. Black-Right-Pointing-Pointer The break of the P2{sub 1}/c to C2/c structure in (Lu{sub x}Gd{sub 1-x}){sub 2}SiO{sub 5}:Sm occurs for 0.15

  11. Development of advanced Czochralski growth process to produce low-cost 150 kG silicon ingots from a single crucible for technology readiness

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The modified CG2000 crystal grower construction, installation, and machine check out was completed. The process development check out proceeded with several dry runs and one growth run. Several machine calibrations and functional problems were discovered and corrected. Exhaust gas analysis system alternatives were evaluated and an integrated system approved and ordered. Several growth runs on a development CG2000 RC grower show that complete neck, crown, and body automated growth can be achieved with only one operator input.

  12. A comparison between Rad-Hard Standard Float Zone (FZ) and Magnetic Czochralski (MCz) Silicon Diodes in Radiotherapy Electron Beams Dosimetry

    NASA Astrophysics Data System (ADS)

    dos Santos, T. C.; Gonçalves, J. A. C.; Vasques, M. M.; Tobias, C. C. B.; Neves-Junior, W. F. P.; Haddad, C. M. K.; Harkonen, J.

    2011-08-01

    In this work we present the preliminary results obtained with a comparison between rad-hard FZ and MCz silicon diodes as on-line clinical electron beams dosimeters. The dynamic current response of the diodes under irradiation with electron beams within the energy range of 6 MeV up to 21 MeV was investigated. For all energies, data show good instantaneous repeatability of the diodes, characterized by coefficients of variation better than 2.8% and 2.5% to FZ and MCz, respectively. The dose-response curves of both diodes are quite linear with charge sensitivities better than 0.55 μC/Gy and 0.68 μC/Gy to FZ and MCz devices. These results show that MCz diode is more sensitive than FZ diode.

  13. Development of advanced Czochralski growth process to produce low cost 150 kg silicon ingots from a single crucible for technology readiness

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The process development continued, with a total of nine crystal growth runs. One of these was a 150 kg run of 5 crystals of approximately 30 kg each. Several machine and process problems were corrected and the 150 kg run was as successful as previous long runs on CG2000 RC's. The accelerated recharge and growth will be attempted when the development program resumes at full capacity in FY '82. The automation controls (Automatic Grower Light Computer System) were integrated to the seed dip temperature, shoulder, and diameter sensors on the CG2000 RC development grower. Test growths included four crystals, which were grown by the computer/sensor system from seed dip through tail off. This system will be integrated on the Mod CG2000 grower during the next quarter. The analytical task included the completion and preliminary testing of the gas chromatograph portion of the Furnace Atmosphere Analysis System. The system can detect CO concentrations and will be expanded to oxygen and water analysis in FY '82.

  14. Enhanced crystallization of amorphous silicon thin films using embedded silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Anderson, Curtis Michael

    This thesis is concerned with the production of silicon thin films for photovoltaic applications. Much research has been carried out to find a stable, more efficient alternative to amorphous silicon, resulting in a number of various amorphous/crystalline mixed-phase film structures with properties superior to amorphous silicon. This thesis work details a completely new approach to mixed-phase film deposition, focusing on the fast crystallization of these films. The deposition of amorphous silicon films with embedded nanocrystals was carried out via a dual-plasma system. It is known that plasma conditions to produce high quality films are much different from those to produce particles. Hence the experimental system used here involved two separate plasmas to allow the optimum production of the crystalline nanoparticles and the amorphous film. Both plasmas use 13.56 MHz excitation voltage with diluted silane as the silicon precursor. The nanoparticle production reactor is a flow-through device that can be altered to control the size of the particles from around 5--30 nm average diameter. The film production reactor is a parallel-plate capacitively-coupled plasma system, into which the aerosol-suspended nanoparticles were injected. The nanocrystals could either be "co-deposited" simultaneously with the amorphous film, or be deposited separately in a layer-by-layer technique; both approaches are discussed in detail. Measurements of the film conductivity provide for the first time unambiguous evidence that the presence of nanocrystallites above 5 nm in the amorphous film have a direct impact on the electronic properties of co-deposited films. Further measurements of the film structure by transmission electron microscopy (TEM) and Raman spectroscopy demonstrate clearly the effect of embedded nanocrystals on the annealed crystallization process; the immediate growth of the crystal seeds has been observed. Additionally, a newly discovered mechanism of film crystallization

  15. Single crystal ternary oxide ferroelectric integration with Silicon

    NASA Astrophysics Data System (ADS)

    Bakaul, Saidur; Serrao, Claudy; Youun, Long; Khan, Asif; Salahuddin, Sayeef

    2015-03-01

    Integrating single crystal, ternary oxide ferroelectric thin film with Silicon or other arbitrary substrates has been a holy grail for the researchers since the inception of microelectronics industry. The key motivation is that adding ferroelectric materials to existing electronic devices could bring into new functionality, physics and performance improvement such as non-volatility of information, negative capacitance effect and lowering sub-threshold swing of field effect transistor (FET) below 60 mV/decade in FET [Salahuddin, S, Datta, S. Nano Lett. 8, 405(2008)]. However, fabrication of single crystal ferroelectric thin film demands stringent conditions such as lattice matched single crystal substrate and high processing temperature which are incompatible with Silicon. Here we report on successful integration of PbZr0.2Ti0.8O3 in single crystal form with by using a layer transfer method. The lattice structure, surface morphology, piezoelectric coefficient d33, dielectric constant, ferroelectric domain switching and spontaneous and remnant polarization of the transferred PZT are as good as these characteristics of the best PZT films grown by pulsed laser deposition on lattice matched oxide substrates. We also demonstrate Si based, FE gate controlled FET devices.

  16. Apparatus and method for the horizontal, crucible-free growth of silicon sheet crystals

    SciTech Connect

    Ciszek, T.F.

    1987-03-17

    This patent describes an apparatus for crucible-free growth of a sheet crystal of silicon, the apparatus comprising; means for providing a substantially enclosed space having an inert atmosphere; heating means for sequentially forming molten silicon from a source of substantially pure silicon within the space; means for vertically feeding a silicon source toward the heating means to form a molten layer of silicon at a top of the source; means for drawing a continuous silicon sheet crystal from the molten silicon layer within the space; wherein a meniscus of molten silicon is created by the drawing means. The apparatus includes means to control the shape of the meniscus, and the controlling means includes a repulsive RF generator for repulsive support of the meniscus as a molten silicon sheet crystal is drawn from the molten silicon. A crucible-free, non-dendritic growth method is described for continuously forming a silicon crystal sheet from a rod of substantially pure silicon, the method comprising: employing an RF heating means having first and second portions to provide a molten layer at an end of the silicon rod in an inert atmosphere by actively heating a first region at the end of the silicon rod while preventing an active heating of a second region of the end of the silicon rod.

  17. Detached Solidification of Germanium-Silicon Crystals on the ISS

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.; Croell, A.

    2016-01-01

    A series of Ge(sub 1-x) Si(sub x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. The primary objective of the research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon alloy crystals. A comparison will be made between crystals grown by the normal and "detached" Bridgman methods and the ground-based float zone technique. Crystals grown without being in contact with a container have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. "Detached" or "dewetted" Bridgman growth is similar to regular Bridgman growth in that most of the melt is in contact with the crucible wall, but the crystal is separated from the wall by a small gap, typically of the order of 10-100 microns. Long duration reduced gravity is essential to test the proposed theory of detached growth. Detached growth requires the establishment of a meniscus between the crystal and the ampoule wall. The existence of this meniscus depends on the ratio of the strength of gravity to capillary forces. On Earth, this ratio is large and stable detached growth can only be obtained over limited conditions. Crystals grown detached on the ground exhibited superior structural quality as evidenced by measurements of etch pit density, synchrotron white beam X-ray topography and double axis X-ray diffraction.

  18. Water cooled silicon crystals for X-ray monochromators

    NASA Astrophysics Data System (ADS)

    Wahl, R.; Shah, R.; Jackson, K.; Tonnessen, T.

    1992-07-01

    Insertion devices (wigglers and undulators) proposed for synchrotron radiation sources will produce up to 10 kW/cm2 of thermal loading. In a double crystal monochromator, the first crystal must absorb nearly all of this output power, as it diffracts the desired wavelength to the second crystal. Storage rings currently projected or under construction produce heat loads of this intensity and thus require significantly improved optical element cooling methods to preserve the spectral quality of the output radiation. As beam intensities reach these higher levels, analysis of the thermal performance of passive and actively cooled optical elements becomes more and more critical because such elements are a cost effective means for producing a cooled crystal that performs to its design specifications the first time it is installed in the beamline. The Rocketdyne Division of Rockwell International is applying the experience gained in high energy laser optics research (the design of cooled IR and UV optical components for free electron lasers) to the problems of cooled X-ray monochromator crystals and grazing incidence VUV optics. In this paper, a set of first order parametric calculations and a second order finite element calculation were performed to determine surface temperature rise, coolant pressure drop and surface distortion in a single crystal silicon heat exchanger with heat loads of 100 to 550 W/cm2. Two different heat exchanger designs (microchannels and pin post cell) and two different coolants (water and liquid gallium) were analyzed to assess performance advantages of each.

  19. Development of Advanced Czochralski Growth Process to produce low cost 150 KG silicon ingots from a single crucible for technology readiness

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The modified CG2000 crystal grower construction, installation, and machine check-out was completed. The process development check-out proceeded with several dry runs and one growth run. Several machine calibrations and functional problems were discovered and corrected. Several exhaust gas analysis system alternatives were evaluated and an integrated system approved and ordered. A contract presentation was made at the Project Integration Meeting at JPL, including cost-projections using contract projected throughput and machine parameters. Several growth runs on a development CG200 RC grower show that complete neck, crown, and body automated growth can be achieved with only one operator input. Work continued for melt level, melt temperature, and diameter sensor development.

  20. Thermally actuated resonant silicon crystal nanobalances

    NASA Astrophysics Data System (ADS)

    Hajjam, Arash

    As the potential emerging technology for next generation integrated resonant sensors and frequency references as well as electronic filters, micro-electro-mechanical resonators have attracted a lot of attention over the past decade. As a result, a wide variety of high frequency micro/nanoscale electromechanical resonators have recently been presented. MEMS resonators, as low-cost highly integrated and ultra-sensitive mass sensors, can potentially provide new opportunities and unprecedented capabilities in the area of mass sensing. Such devices can provide orders of magnitude higher mass sensitivity and resolution compared to Film Bulk Acoustic resonators (FBAR) or the conventional quartz and Surface Acoustic Wave (SAW) resonators due to their much smaller sizes and can be batch-fabricated and utilized in highly integrated large arrays at a very low cost. In this research, comprehensive experimental studies on the performance and durability of thermally actuated micromechanical resonant sensors with frequencies up to tens of MHz have been performed. The suitability and robustness of the devices have been demonstrated for mass sensing applications related to air-borne particles and organic gases. In addition, due to the internal thermo-electro-mechanical interactions, the active resonators can turn some of the consumed electronic power back into the mechanical structure and compensate for the mechanical losses. Therefore, such resonators can provide self-sustained-oscillation without the need for any electronic circuitry. This unique property has been deployed to demonstrate a prototype self-sustained sensor for air-borne particle monitoring. I have managed to overcome one of the obstacles for MEMS resonators, which is their relatively poor temperature stability. This is a major drawback when compared with the conventional quartz crystals. A significant decrease of the large negative TCF for the resonators has been attained by doping the devices with a high

  1. Low cost Czochralski crystal growing technology. Near implementation of the flat plate photovoltaic cost reduction of the low cost solar array project

    NASA Technical Reports Server (NTRS)

    Roberts, E. G.

    1980-01-01

    Equipment developed for the manufacture of over 100 kg of silicon ingot from one crucible by rechanging from another crucible is described. Attempts were made to eliminate the cost of raising the furnace temperature to 250 C above the melting point of silicon by using an RF coil to melt polycrystalline silicon rod as a means of rechanging the crucible. Microprocessor control of the straight growth process was developed and domonstrated for both 4 inch and 6 inch diameter. Both meltdown and melt stabilization processes were achieved using operator prompting through the microprocessor. The use of the RF work coil in poly rod melting as a heat sink in the accelerated growth process was unsuccessful. The total design concept for fabrication and interfacing of the total cold crucible system was completed.

  2. Computer modelling in crystal growth from the melt; Proceedings of the First NATO Workshop, Parma, Italy, Apr. 6, 7, 1989

    NASA Astrophysics Data System (ADS)

    Mueller, G.; Hurle, D. T. J.; Wenzl, H.

    1989-09-01

    This volume includes papers on three-dimensional time-dependent modeling of the Marangoni convection in zone melting configurations for GaAs, the real-time modeling and adaptive control of Czochralski growth, species transport in magnetic field Gzochralski growth, and Czochralski growth of silicon under an axial magnetic field. Consideration is also given to the effect of a shaped magnetic field on Czochralski silicon growth, a numerical analysis of heat transfer in LEC growth of GaAs, temperature and stress-field calculations in indium phosphide during LEC growth, and a numerical method for reducing stress level in GaAs crystals. Other papers are on a numerical simulation of oscillatory convection in semiconductor melts, linear and nonlinear analysis of the Hadley circulation, and the influence of the Prandtl number on laminar natural convection in a cylinder caused by g-jitter.

  3. Silicon photonic crystal thermal emitter at near-infrared wavelengths.

    PubMed

    O'Regan, Bryan J; Wang, Yue; Krauss, Thomas F

    2015-08-21

    Controlling thermal emission with resonant photonic nanostructures has recently attracted much attention. Most of the work has concentrated on the mid-infrared wavelength range and/or was based on metallic nanostructures. Here, we demonstrate the experimental operation of a resonant thermal emitter operating in the near-infrared (≈1.5 μm) wavelength range. The emitter is based on a doped silicon photonic crystal consisting of a two dimensional square array of holes and using silicon-on-insulator technology with a device-layer thickness of 220 nm. The device is resistively heated by passing current through the photonic crystal membrane. At a temperature of ≈1100 K, we observe relatively sharp emission peaks with a Q factor around 18. A support structure system is implemented in order to achieve a large area suspended photonic crystal thermal emitter and electrical injection. The device demonstrates that weak absorption together with photonic resonances can be used as a wavelength-selection mechanism for thermal emitters, both for the enhancement and the suppression of emission.

  4. Improved Silicon Carbide Crystals Grown From Atomically Flat Surfaces

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.

    2003-01-01

    The NASA Glenn Research Center is demonstrating that atomically flat (i.e., step-free) silicon carbide (SiC) surfaces are ideal for realizing greatly improved wide bandgap semiconductor films with lower crystal defect densities. Further development of these improved films could eventually enable harsh-environment electronics beneficial to jet engine and other aerospace and automotive applications, as well as much more efficient and compact power distribution and control. The technique demonstrated could also improve blue-light lasers and light-emitting-diode displays.

  5. Modeling of dislocation dynamics in germanium Czochralski growth

    NASA Astrophysics Data System (ADS)

    Artemyev, V. V.; Smirnov, A. D.; Kalaev, V. V.; Mamedov, V. M.; Sidko, A. P.; Podkopaev, O. I.; Kravtsova, E. D.; Shimansky, A. F.

    2017-06-01

    Obtaining very high-purity germanium crystals with low dislocation density is a practically difficult problem, which requires knowledge and experience in growth processes. Dislocation density is one of the most important parameters defining the quality of germanium crystal. In this paper, we have performed experimental study of dislocation density during 4-in. germanium crystal growth using the Czochralski method and comprehensive unsteady modeling of the same crystal growth processes, taking into account global heat transfer, melt flow and melt/crystal interface shape evolution. Thermal stresses in the crystal and their relaxation with generation of dislocations within the Alexander-Haasen model have been calculated simultaneously with crystallization dynamics. Comparison to experimental data showed reasonable agreement for the temperature, interface shape and dislocation density in the crystal between calculation and experiment.

  6. Structure development in silicon sheet by shaped crystallization

    NASA Technical Reports Server (NTRS)

    Leipold, M. H.; De Angelis, R. J.

    1978-01-01

    Models are presented for the development of a parallel twinned structure of the 110 plane type and the 112 line type in silicon ribbons. The models are believed to be mutually compatible and operable. The first model relates the requirements for super-cooling during crystallization. The existence of reentrant angles associated with the twin structure is proposed to provide a rough interface to reduce super-cooling. The spacing of the twins is proposed to be limited by the geometrical relationship between the thermal gradient in the liquid and the dimensions of the twinned crystallization front. The second model relates the thermal stress configuration to detail dislocation reactions which would be expected to develop twins. While a specific dislocation mechanism cannot yet be defined, a number of alternatives are presented. All of these various dislocation mechanisms would result in the observed crystalline configuration and the choice among them is not critical.

  7. Structure development in silicon sheet by shaped crystallization

    NASA Technical Reports Server (NTRS)

    Leipold, M. H.; De Angelis, R. J.

    1978-01-01

    Models are presented for the development of a parallel twinned structure of the 110 plane type and the 112 line type in silicon ribbons. The models are believed to be mutually compatible and operable. The first model relates the requirements for super-cooling during crystallization. The existence of reentrant angles associated with the twin structure is proposed to provide a rough interface to reduce super-cooling. The spacing of the twins is proposed to be limited by the geometrical relationship between the thermal gradient in the liquid and the dimensions of the twinned crystallization front. The second model relates the thermal stress configuration to detail dislocation reactions which would be expected to develop twins. While a specific dislocation mechanism cannot yet be defined, a number of alternatives are presented. All of these various dislocation mechanisms would result in the observed crystalline configuration and the choice among them is not critical.

  8. Control of Nd and Cr concentrations in Nd,Cr : Gd 3Ga 5O 12 single crystals grown by Czochralski method

    NASA Astrophysics Data System (ADS)

    Keszei, B.; Paitz, J.; Vandlik, J.; Süveges, A.

    2001-06-01

    During the growth process of the Nd,Cr : Gd 3Ga 5O 12 (Nd,Cr : GGG) laser crystals the optimum concentrations of the dopants cannot be realized in axial direction of the crystal at a constant pulling (growth) rate as the effective segregation coefficients ( k) of Nd 3+ and Cr 3+ are not unity and not uniform ( k<1 and k>1, respectively). To solve this problem the dopant concentrations were measured in the crystals grown at different pulling rates by atomic absorption to determine the effective and equilibrium segregation coefficients and the ratio of the boundary layer thickness and diffusion coefficients. In the light of these parameters we suggest a pulling (growth) rate program as a function of the fraction of the crystallized melt leading to the smallest concentration variation of the dopants along the length axis of the crystals. The variation of Nd 3+ concentration in the crystal reduced from 35% to 19% while the laser efficiency increased by 15-20% by this method.

  9. A quantitative model with new scaling for silicon carbide particle engulfment during silicon crystal growth

    NASA Astrophysics Data System (ADS)

    Derby, Jeffrey J.; Tao, Yutao; Reimann, Christian; Friedrich, Jochen; Jauß, Thomas; Sorgenfrei, Tina; Cröll, Arne

    2017-04-01

    We present rigorous numerical modeling and analytical arguments to describe data on the engulfment of silicon carbide particles during silicon crystal growth obtained via advanced terrestrial and microgravity experiments. For the first time in over a decade of research on SiC inclusions in silicon, our model is able to provide a quantitative correlation with experimental results, and we are able to unambiguously identify the underlying physical mechanisms that give rise to the observed behavior of this system. In particular, we identify a significant and previously unascertained interaction between particle-induced interface deflection (originating from the thermal conductivity of the SiC particle being larger than that of the surrounding silicon liquid) and curvature-induced changes in melting temperature arising from the Gibbs-Thomson effect. For a particular range of particle sizes, the Gibbs-Thomson effect flattens the deflected solidification interface, thereby reducing drag on the particle and increasing its critical velocity for engulfment. We show via numerical calculations and analytical reasoning that these effects give rise to a new scaling of the critical velocity to particle size as vc ∼R - 5 / 3 , whereas all prior models have predicted either vc ∼R-1 or vc ∼R - 4 / 3 . This new scaling is needed to quantitatively describe the experimental observations for this system.

  10. Observation of soliton compression in silicon photonic crystals

    PubMed Central

    Blanco-Redondo, A.; Husko, C.; Eades, D.; Zhang, Y.; Li, J.; Krauss, T.F.; Eggleton, B.J.

    2014-01-01

    Solitons are nonlinear waves present in diverse physical systems including plasmas, water surfaces and optics. In silicon, the presence of two photon absorption and accompanying free carriers strongly perturb the canonical dynamics of optical solitons. Here we report the first experimental demonstration of soliton-effect pulse compression of picosecond pulses in silicon, despite two photon absorption and free carriers. Here we achieve compression of 3.7 ps pulses to 1.6 ps with <10 pJ energy. We demonstrate a ~1-ps free-carrier-induced pulse acceleration and show that picosecond input pulses are critical to these observations. These experiments are enabled by a dispersion-engineered slow-light photonic crystal waveguide and an ultra-sensitive frequency-resolved electrical gating technique to detect the ultralow energies in the nanostructured device. Strong agreement with a nonlinear Schrödinger model confirms the measurements. These results further our understanding of nonlinear waves in silicon and open the way to soliton-based functionalities in complementary metal-oxide-semiconductor-compatible platforms. PMID:24423977

  11. Photonic crystal enhanced silicon cell based thermophotovoltaic systems

    DOE PAGES

    Yeng, Yi Xiang; Chan, Walker R.; Rinnerbauer, Veronika; ...

    2015-01-30

    We report the design, optimization, and experimental results of large area commercial silicon solar cell based thermophotovoltaic (TPV) energy conversion systems. Using global non-linear optimization tools, we demonstrate theoretically a maximum radiative heat-to-electricity efficiency of 6.4% and a corresponding output electrical power density of 0.39 W cm⁻² at temperature T = 1660 K when implementing both the optimized two-dimensional (2D) tantalum photonic crystal (PhC) selective emitter, and the optimized 1D tantalum pentoxide – silicon dioxide PhC cold-side selective filter. In addition, we have developed an experimental large area TPV test setup that enables accurate measurement of radiative heat-to-electricity efficiency formore » any emitter-filter-TPV cell combination of interest. In fact, the experimental results match extremely well with predictions of our numerical models. Our experimental setup achieved a maximum output electrical power density of 0.10W cm⁻² and radiative heat-to-electricity efficiency of 1.18% at T = 1380 K using commercial wafer size back-contacted silicon solar cells.« less

  12. Photonic crystal enhanced silicon cell based thermophotovoltaic systems

    SciTech Connect

    Yeng, Yi Xiang; Chan, Walker R.; Rinnerbauer, Veronika; Stelmakh, Veronika; Senkevich, Jay J.; Joannopoulos, John D.; Soljacic, Marin; Čelanović, Ivan

    2015-01-30

    We report the design, optimization, and experimental results of large area commercial silicon solar cell based thermophotovoltaic (TPV) energy conversion systems. Using global non-linear optimization tools, we demonstrate theoretically a maximum radiative heat-to-electricity efficiency of 6.4% and a corresponding output electrical power density of 0.39 W cm⁻² at temperature T = 1660 K when implementing both the optimized two-dimensional (2D) tantalum photonic crystal (PhC) selective emitter, and the optimized 1D tantalum pentoxide – silicon dioxide PhC cold-side selective filter. In addition, we have developed an experimental large area TPV test setup that enables accurate measurement of radiative heat-to-electricity efficiency for any emitter-filter-TPV cell combination of interest. In fact, the experimental results match extremely well with predictions of our numerical models. Our experimental setup achieved a maximum output electrical power density of 0.10W cm⁻² and radiative heat-to-electricity efficiency of 1.18% at T = 1380 K using commercial wafer size back-contacted silicon solar cells.

  13. Photonic crystal enhanced silicon cell based thermophotovoltaic systems.

    PubMed

    Yeng, Yi Xiang; Chan, Walker R; Rinnerbauer, Veronika; Stelmakh, Veronika; Senkevich, Jay J; Joannopoulos, John D; Soljacic, Marin; Čelanović, Ivan

    2015-02-09

    We report the design, optimization, and experimental results of large area commercial silicon solar cell based thermophotovoltaic (TPV) energy conversion systems. Using global non-linear optimization tools, we demonstrate theoretically a maximum radiative heat-to-electricity efficiency of 6.4% and a corresponding output electrical power density of 0.39 W cm(-2) at temperature T = 1660 K when implementing both the optimized two-dimensional (2D) tantalum photonic crystal (PhC) selective emitter, and the optimized 1D tantalum pentoxide - silicon dioxide PhC cold-side selective filter. In addition, we have developed an experimental large area TPV test setup that enables accurate measurement of radiative heat-to-electricity efficiency for any emitter-filter-TPV cell combination of interest. In fact, the experimental results match extremely well with predictions of our numerical models. Our experimental setup achieved a maximum output electrical power density of 0.10W cm(-2) and radiative heat-to-electricity efficiency of 1.18% at T = 1380 K using commercial wafer size back-contacted silicon solar cells.

  14. Porous silicon photonic crystals for detection of infections

    NASA Astrophysics Data System (ADS)

    Gupta, B.; Guan, B.; Reece, P. J.; Gooding, J. J.

    2012-10-01

    In this paper we demonstrate the possibility of modifying porous silicon (PSi) particles with surface chemistry and immobilizing a biopolymer, gelatin for the detection of protease enzymes in solution. A rugate filter, a one-dimensional photonic crystal, is fabricated that exhibits a high-reflectivity optical resonance that is sensitive to small changes in the refractive index. To immobilize gelatin in the pores of the particles, the hydrogen-terminated silicon surface was first modified with an alkyne, 1,8-nonadiyne via hydrosilylation to protect the silicon surfaces from oxidation. This modification allows for further functionality to be added such as the coupling of gelatin. Exposure of the gelatin modified particles to the protease subtilisin in solution causes a change in the refractive index, resulting in a shift of the resonance to shorter wavelengths, indicating cleavage of organic material within the pores. The ability to monitor the spectroscopic properties of microparticles, and shifts in the optical signature due to changes in the refractive index of the material within the pore space, is demonstrated.

  15. Crystallization of Electrodeposited Germanium Thin Film on Silicon (100)

    PubMed Central

    Abidin, Mastura Shafinaz Zainal; Matsumura, Ryo; Anisuzzaman, Mohammad; Park, Jong-Hyeok; Muta, Shunpei; Mahmood, Mohamad Rusop; Sadoh, Taizoh; Hashim, Abdul Manaf

    2013-01-01

    We report the crystallization of electrodeposited germanium (Ge) thin films on n-silicon (Si) (100) by rapid melting process. The electrodeposition was carried out in germanium (IV) chloride: propylene glycol (GeCl4:C3H8O2) electrolyte with constant current of 50 mA for 30 min. The measured Raman spectra and electron backscattering diffraction (EBSD) images show that the as-deposited Ge thin film was amorphous. The crystallization of deposited Ge was achieved by rapid thermal annealing (RTA) at 980 °C for 1 s. The EBSD images confirm that the orientations of the annealed Ge are similar to that of the Si substrate. The highly intense peak of Raman spectra at 300 cm−1 corresponding to Ge-Ge vibration mode was observed, indicating good crystal quality of Ge. An additional sub peak near to 390 cm−1 corresponding to the Si-Ge vibration mode was also observed, indicating the Ge-Si mixing at Ge/Si interface. Auger electron spectroscopy (AES) reveals that the intermixing depth was around 60 nm. The calculated Si fraction from Raman spectra was found to be in good agreement with the value estimated from Ge-Si equilibrium phase diagram. The proposed technique is expected to be an effective way to crystallize Ge films for various device applications as well as to create strain at the Ge-Si interface for enhancement of mobility. PMID:28788375

  16. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs

    PubMed Central

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K.; Christiansen, Silke; Vollmer, Frank

    2016-01-01

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported. PMID:27113674

  17. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs.

    PubMed

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K; Christiansen, Silke; Vollmer, Frank

    2016-04-26

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported.

  18. Self-assembled single-crystal silicon circuits on plastic.

    PubMed

    Stauth, Sean A; Parviz, Babak A

    2006-09-19

    We demonstrate the use of self-assembly for the integration of freestanding micrometer-scale components, including single-crystal, silicon field-effect transistors (FETs) and diffusion resistors, onto flexible plastic substrates. Preferential self-assembly of multiple microcomponent types onto a common platform is achieved through complementary shape recognition and aided by capillary, fluidic, and gravitational forces. We outline a microfabrication process that yields single-crystal, silicon FETs in a freestanding, powder-like collection for use with self-assembly. Demonstrations of self-assembled FETs on plastic include logic inverters and measured electron mobility of 592 cm2/V-s. Finally, we extend the self-assembly process to substrates each containing 10,000 binding sites and realize 97% self-assembly yield within 25 min for 100-microm-sized elements. High-yield self-assembly of micrometer-scale functional devices as outlined here provides a powerful approach for production of macroelectronic systems.

  19. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs

    NASA Astrophysics Data System (ADS)

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K.; Christiansen, Silke; Vollmer, Frank

    2016-04-01

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported.

  20. Defects in silicon effect on device performance and relationship to crystal growth conditions

    NASA Technical Reports Server (NTRS)

    Jastrzebski, L.

    1985-01-01

    A relationship between material defects in silicon and the performance of electronic devices will be described. A role which oxygen and carbon in silicon play during the defects generation process will be discussed. The electronic properties of silicon are a strong function of the oxygen state in the silicon. This state controls mechanical properties of silicon efficiency for internal gettering and formation of defects in the device's active area. In addition, to temperature, time, ambience, and the cooling/heating rates of high temperature treatments, the oxygen state is a function of the crystal growth process. The incorporation of carbon and oxygen into silicon crystal is controlled by geometry and rotation rates applied to crystal and crucible during crystal growths. Also, formation of nucleation centers for oxygen precipitation is influenced by the growth process, although there is still a controversy which parameters play a major role. All these factors will be reviewed with special emphasis on areas which are still ambiguous and controversial.

  1. Crystallization and activation of silicon by microwave rapid annealing

    NASA Astrophysics Data System (ADS)

    Kimura, Shunsuke; Ota, Kosuke; Hasumi, Masahiko; Suzuki, Ayuta; Ushijima, Mitsuru; Sameshima, Toshiyuki

    2016-07-01

    A combination of the carbon-powder absorber with microwave irradiation is proposed as a rapid heat method. 2-μm-diameter carbon powders with a packing density of 0.08 effectively absorbed 2.45 GHz 1000-W-microwave and heated themselves to 1163 °C for 26 s. The present heat treatment recrystallized n-type crystalline silicon surfaces implanted with 1.0 × 10^{15}hbox {-cm}^{-2}-boron and phosphorus atoms with crystalline volume ratios of 0.99 and 0.93, respectively, by microwave irradiation at 1000 W for 20 s. Activation and carrier generation were simultaneously achieved with a sheet resistivity of 62 Ω / hbox {sq}. A high photo-induced-carrier effective lifetime of 1.0 × 10^{-4} s was also achieved. Typical electrical current-rectified characteristic and solar cell characteristic with an efficiency of 12.1 % under 100-mW/cm2-air-mass-1.5 illumination were obtained. Moreover, heat treatment with microwave irradiation at 1000 W for 22 s successfully crystallized silicon thin films with thicknesses ranging from 2.4 to 50 nm formed on quartz substrates. Nano-crystalline cluster structure with a high volume ratio of 50 % was formed in the 1.8-nm (initial 2.4-nm)-thick silicon films. Photoluminescence around 1.77 eV was observed for the 1.8-nm-thick silicon films annealed at 260 °C in 1.3 × 106-Pa-H2O-vapor for 3 h after the microwave heating.

  2. Digital photofinishing system based on liquid crystal on silicon

    NASA Astrophysics Data System (ADS)

    Zheng, Minmin; Yan, Huimin; Zhang, Xiuda; Du, Yanli

    2006-01-01

    As the digital camera user base grows, so does the demand for digital imaging services. A new digital photo finishing system based on Liquid Crystal On Silicon (LCOS) is presented. The LCOS panel motherboard is made up of CMOS chip. Three individual streams of light (red, green, blue) are directed to corresponding Polarization Beam Spliter (PBS) to make the S polarization beam arrive at LCOS panel. When the Liquid appears light, the S polarization beam is changed to P polarization beam and reflected to pass through Polarization Beam Spliter. Compared with Thin Film Transistor-Liquid Crystal Display (TFT-LCD), LCOS has many merits including high resolution, high contrast, wide viewing angle, low cost and so on. In this work, we focus on the way in which the images will be displayed on LCOS. A liquid crystal on silicon microdisplay driver circuit for digital photo finishing system has been designed and fabricated using BRILLIAN microdisplay driver lite(MDD-LITE) ASIC and LCOS SXGA (1280×1024 pixel) with a 0.78"(20mm) diagonal active matrix reflective mode LCD. The driver includes a control circuit, which presents serial data, serial clock , write protect signals and control signals for LED, and a mixed circuit which implements RGB signal to input the LCOS. According to a minimum error sum of squares algorithm, we find a minimum offset and then shift RGB optical intensity vs voltage curves right and left to make these three curves almost coincide with each other. The design had great application in the digital photo finishing.

  3. Process for making silicon

    NASA Technical Reports Server (NTRS)

    Levin, Harry (Inventor)

    1987-01-01

    A reactor apparatus (10) adapted for continuously producing molten, solar grade purity elemental silicon by thermal reaction of a suitable precursor gas, such as silane (SiH.sub.4), is disclosed. The reactor apparatus (10) includes an elongated reactor body (32) having graphite or carbon walls which are heated to a temperature exceeding the melting temperature of silicon. The precursor gas enters the reactor body (32) through an efficiently cooled inlet tube assembly (22) and a relatively thin carbon or graphite septum (44). The septum (44), being in contact on one side with the cooled inlet (22) and the heated interior of the reactor (32) on the other side, provides a sharp temperature gradient for the precursor gas entering the reactor (32) and renders the operation of the inlet tube assembly (22) substantially free of clogging. The precursor gas flows in the reactor (32) in a substantially smooth, substantially axial manner. Liquid silicon formed in the initial stages of the thermal reaction reacts with the graphite or carbon walls to provide a silicon carbide coating on the walls. The silicon carbide coated reactor is highly adapted for prolonged use for production of highly pure solar grade silicon. Liquid silicon (20) produced in the reactor apparatus (10) may be used directly in a Czochralski or other crystal shaping equipment.

  4. Rapid thermal annealing and crystallization mechanisms study of silicon nanocrystal in silicon carbide matrix

    PubMed Central

    2011-01-01

    In this paper, a positive effect of rapid thermal annealing (RTA) technique has been researched and compared with conventional furnace annealing for Si nanocrystalline in silicon carbide (SiC) matrix system. Amorphous Si-rich SiC layer has been deposited by co-sputtering in different Si concentrations (50 to approximately 80 v%). Si nanocrystals (Si-NC) containing different grain sizes have been fabricated within the SiC matrix under two different annealing conditions: furnace annealing and RTA both at 1,100°C. HRTEM image clearly reveals both Si and SiC-NC formed in the films. Much better "degree of crystallization" of Si-NC can be achieved in RTA than furnace annealing from the research of GIXRD and Raman analysis, especially in high-Si-concentration situation. Differences from the two annealing procedures and the crystallization mechanism have been discussed based on the experimental results. PMID:21711625

  5. Strong Photoluminescence from the Reaction Product of Erbium and Oxygen on Silicon Crystal

    NASA Astrophysics Data System (ADS)

    Suezawa, Masashi; Sumino, Koji

    1994-12-01

    Photoluminescence spectra around 1.5 µm from silicon (Si) doped with erbium (Er) by various methods have been studied. The doping methods that were adopted were annealing after painting of Er(NO3)3 solutions and evaporation of Er on Si surface, and annealing of specimens in the Er vapour. Strong photoluminescence similar to that of Er2O3 was observed only from the damaged surface of n-type Czochralski-grown Si when Er was doped with the last method. Analysis of the damaged surface by the method of electron spectroscopy for chemical analysis (ESCA) showed that Er2O3 was generated on the surface of n-type Cz.Si.

  6. The homogeneity of Czochralski-grown Bi{sub 2}Te{sub 2.85}Se{sub 0.15} single crystals

    SciTech Connect

    Svechnikova, T.E.; Maksimova, N.M.; Sussmann, G.

    1995-01-01

    The Bi{sub 2}Te{sub 2.85}Se{sub 0.15} solid solution is an optimal material for n-arms of thermoelectric coolers operating in the range of 250-400 K. The use of Bi{sub 2}Te{sub 2.85}Se{sub 0.15} single crystals in thermoelectric coolers substantially improves their power parameters and raises the maximum degree of cooling {Delta}T{sub max}, and extends the range of their application in cooling microdevices of various types. The objective of this work was to investigate the effect of growth conditions and the purity of starting materials on the axial and radial homogeneity of Bi{sub 2}Te{sub 2.85}Se{sub 0.15} single crystals.

  7. Tailoring the optical constants in single-crystal silicon with embedded silver nanostructures for advanced silicon photonics applications

    NASA Astrophysics Data System (ADS)

    Akhter, Perveen; Huang, Mengbing; Spratt, William; Kadakia, Nirag; Amir, Faisal

    2015-03-01

    Plasmonic effects associated with metal nanostructures are expected to hold the key to tailoring light emission/propagation and harvesting solar energy in materials including single crystal silicon which remains the backbone in the microelectronics and photovoltaics industries but unfortunately, lacks many functionalities needed for construction of advanced photonic and optoelectronics devices. Currently, silicon plasmonic structures are practically possible only in the configuration with metal nanoparticles or thin film arrays on a silicon surface. This does not enable one to exploit the full potential of plasmonics for optical engineering in silicon, because the plasmonic effects are dominant over a length of ˜50 nm, and the active device region typically lies below the surface much beyond this range. Here, we report on a novel method for the formation of silver nanoparticles embedded within a silicon crystal through metal gettering from a silver thin film deposited at the surface to nanocavities within the Si created by hydrogen ion implantation. The refractive index of the Ag-nanostructured layer is found to be 3-10% lower or higher than that of silicon for wavelengths below or beyond ˜815-900 nm, respectively. Around this wavelength range, the optical extinction values increase by a factor of 10-100 as opposed to the pure silicon case. Increasing the amount of gettered silver leads to an increased extinction as well as a redshift in wavelength position for the resonance. This resonance is attributed to the surface plasmon excitation of the resultant silver nanoparticles in silicon. Additionally, we show that the profiles for optical constants in silicon can be tailored by varying the position and number of nanocavity layers. Such silicon crystals with embedded metal nanostructures would offer novel functional base structures for applications in silicon photonics, optoelectronics, photovoltaics, and plasmonics.

  8. Tailoring the optical constants in single-crystal silicon with embedded silver nanostructures for advanced silicon photonics applications

    SciTech Connect

    Akhter, Perveen; Huang, Mengbing Spratt, William; Kadakia, Nirag; Amir, Faisal

    2015-03-28

    Plasmonic effects associated with metal nanostructures are expected to hold the key to tailoring light emission/propagation and harvesting solar energy in materials including single crystal silicon which remains the backbone in the microelectronics and photovoltaics industries but unfortunately, lacks many functionalities needed for construction of advanced photonic and optoelectronics devices. Currently, silicon plasmonic structures are practically possible only in the configuration with metal nanoparticles or thin film arrays on a silicon surface. This does not enable one to exploit the full potential of plasmonics for optical engineering in silicon, because the plasmonic effects are dominant over a length of ∼50 nm, and the active device region typically lies below the surface much beyond this range. Here, we report on a novel method for the formation of silver nanoparticles embedded within a silicon crystal through metal gettering from a silver thin film deposited at the surface to nanocavities within the Si created by hydrogen ion implantation. The refractive index of the Ag-nanostructured layer is found to be 3–10% lower or higher than that of silicon for wavelengths below or beyond ∼815–900 nm, respectively. Around this wavelength range, the optical extinction values increase by a factor of 10–100 as opposed to the pure silicon case. Increasing the amount of gettered silver leads to an increased extinction as well as a redshift in wavelength position for the resonance. This resonance is attributed to the surface plasmon excitation of the resultant silver nanoparticles in silicon. Additionally, we show that the profiles for optical constants in silicon can be tailored by varying the position and number of nanocavity layers. Such silicon crystals with embedded metal nanostructures would offer novel functional base structures for applications in silicon photonics, optoelectronics, photovoltaics, and plasmonics.

  9. Spiral formation during Czochralski growth of rare-earth scandates

    NASA Astrophysics Data System (ADS)

    Uecker, R.; Wilke, H.; Schlom, D. G.; Velickov, B.; Reiche, P.; Polity, A.; Bernhagen, M.; Rossberg, M.

    2006-09-01

    Single crystals of the rare-earth scandates DyScO 3, GdScO 3, SmScO 3, and NdScO 3 were grown by the Czochralski technique. The influence of the absorption of radiant heat in the growing crystals on interface stability was investigated. Numerical simulations were performed to calculate the influence of thermal instabilities close to the growth interface on the axial symmetry of the flow field, which eventually leads to spiral growth. To inhibit spiral formation, a conical baffle was utilized to intensifying the buoyant-thermocapillary convection.

  10. Friction and wear behavior of single-crystal silicon carbide in contact with titanium

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1977-01-01

    Sliding friction experiments were conducted with single crystal silicon carbide in sliding contact with titanium. Results indicate that the friction coefficient is greater in vacuum than in argon and that this is due to the greater adhesion or adhesive transfer in vacuum. Thin films of silicon carbide transferred to titanium also adhered to silicon carbide both in argon at atmospheric pressure and in high vacuum. Cohesive bonds fractured on both the silicon carbide and titanium surfaces. The wear debris of silicon carbide created by fracture plowed the silicon carbide surface in a plastic manner. The friction characteristics of titanium in contact with silicon carbide were sensitive to the surface roughness of silicon carbide, and the friction coefficients were higher for a rough surface of silicon carbide than for a smooth one. The difference in friction results was due to plastic deformation (plowing of titanium).

  11. Simulation of ultrasound influence on melt convection for the growth of Ga(x)In(1-x)Sb and Si single crystals by the Czochralski method.

    PubMed

    Kozhemyakin, G N; Nemets, L V; Bulankina, A A

    2014-12-01

    The flow simulation for GaxIn1-xSb and Si melts was conducted for quasi-steady conditions. The maximum velocity was under the solid-liquid interface near periphery of the crystals. An introduction of ultrasound into the liquid formed a standing wave channel under the solid-liquid interface, which acted on melt particles. The calculations of convective and ultrasonic forces acting on the particles in the melt showed that the ultrasonic force is much higher than the convective force. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Low cost Czochralski crystal growing technology: near term implementation of the flat plate photovoltaic cost reduction of the Low Cost Solar Array Project. Fifth quarterly progress report, April 1-June 30, 1980

    SciTech Connect

    Roberts, E.G.

    1980-01-01

    During this reporting period, the primary activity has been to develop microprocessor control of the crystal growth process and to develop and demonstrate the accelerated crystal growth program. Accelerated recharging of the quartz crucible by the RF melting of polycrystalline silicon feed rods was deemphasized by JPL primarily due to the unavailability of suitable quality feed rods at an effective economical price. The development of the cold crucible program as an alternative method of crucible recharging was continued, but at a lower priority. Work continued on the accelerated crystal growth program. Crystal growth runs were made utilizing the water cooled work coil previously used in the RF polycrystalline silicon rod melting program. Accelerated growth rates were demonstrated but an oxide build-up on the cold surface of the work coil, resulting in heavy flaking and consequent falling of oxide into the melt, resulted in abandoning this approach and redesigning, evaluating, and demonstrating an alternative heat sink arrangement. All necessary parts were received for the cold crucible premelter and system was assembled and interfaced to the multiturn high voltage RF power supply.

  13. Optical nonreciprocal transmission in an asymmetric silicon photonic crystal structure

    SciTech Connect

    Wu, Zheng; Chen, Juguang; Ji, Mengxi; Huang, Qingzhong; Xia, Jinsong; Wang, Yi E-mail: ywangwnlo@mail.hust.edu.cn; Wu, Ying E-mail: ywangwnlo@mail.hust.edu.cn

    2015-11-30

    An optical nonreciprocal transmission (ONT) is realized by employing the nonlinear effects in a compact asymmetric direct-coupled nanocavity-waveguide silicon photonic crystal structure with a high loaded quality factor (Q{sub L}) of 42 360 and large extinction ratio exceeding 30 dB. Applying a single step lithography and successive etching, the device can realize the ONT in an individual nanocavity, alleviating the requirement to accurately control the resonance of the cavities. A maximum nonreciprocal transmission ratio of 21.1 dB as well as a working bandwidth of 280 pm in the telecommunication band are obtained at a low input power of 76.7 μW. The calculated results by employing a nonlinear coupled-mode model are in good agreement with the experiment.

  14. Lifetime analysis of laser crystallized silicon films on glass

    SciTech Connect

    Kühnapfel, Sven; Amkreutz, Daniel; Gall, Stefan; Huang, Jialiang; Teal, Anthony; Kampwerth, Henner; Varlamov, Sergey

    2015-08-07

    Only recently, the quality of liquid phase crystallized silicon directly on glass substrates made a huge leap towards the quality of multi-crystalline wafers with open circuit voltages well above 600 mV. In this paper, we investigate the material quality in order to identify the factors limiting further performance improvements. We employ photoluminescence imaging on a state of the art test structure with lifetime calibration by transient photoluminescence. The resulting lifetime map is converted into an effective diffusion length map and the origin of regions with short lifetimes is investigated with electron backscattering and transmission electron microscopy. High local dislocation densities in areas with dissociated coincidence site lattice boundaries were found to be responsible for the localised quenching of the photoluminescence signal.

  15. Photonic crystal waveguides on silicon rich nitride platform.

    PubMed

    Debnath, Kapil; Bucio, Thalia Dominguez; Al-Attili, Abdelrahman; Khokhar, Ali Z; Saito, Shinichi; Gardes, Frederic Y

    2017-02-20

    We demonstrate design, fabrication, and characterization of two-dimensional photonic crystal (PhC) waveguides on a suspended silicon rich nitride (SRN) platform for applications at telecom wavelengths. Simulation results suggest that a 210 nm photonic band gap can be achieved in such PhC structures. We also developed a fabrication process to realize suspended PhC waveguides with a transmission bandwidth of 20 nm for a W1 PhC waveguide and over 70 nm for a W0.7 PhC waveguide. Using the Fabry-Pérot oscillations of the transmission spectrum we estimated a group index of over 110 for W1 PhC waveguides. For a W1 waveguide we estimated a propagation loss of 53 dB/cm for a group index of 37 and for a W0.7 waveguide the lowest propagation was 4.6 dB/cm.

  16. Radiation emission by electrons channeling in bent silicon crystals

    NASA Astrophysics Data System (ADS)

    Polozkov, Roman G.; Ivanov, Vadim K.; Sushko, Gennady B.; Korol, Andrei V.; Solov'yov, Andrey V.

    2014-09-01

    Results of numerical simulations of electron channeling and emission spectra are reported for straight and uniformly bent silicon crystals. The projectile trajectories are computed using the newly developed module [G.B. Sushko, V.G. Bezchastnov, I.A. Solov'yov, A.V. Korol, W. Greiner, A.V. Solov'yov, J. Comput. Phys. 252, 404 (2013)] of the MBN Explorer packageb [I.A. Solov'yov, A.V. Yakubovich, P.V. Nikolaev, I. Volkovets, A.V. Solov'yov, J. Comput. Chem. 33, 2412 (2013)]. The electron channeling along Si(110) crystallographic planes is studied for the projectile energy 855 MeV.

  17. Compact and fast photonic crystal silicon optical modulators.

    PubMed

    Nguyen, Hong C; Hashimoto, Satoshi; Shinkawa, Mizuki; Baba, Toshihiko

    2012-09-24

    We demonstrate the first sub-100 μm silicon Mach-Zehnder modulators (MZMs) that operate at >10 Gb/s, by exploiting low-dispersion slow-light in lattice-shifted photonic crystal waveguides (LSPCWs). We use two LSPCW-MZM structures, one with LSPCWs in both arms of the MZM, and the other with an LSPCW in only one of the arms. Using the first structure we demonstrate 10 Gb/s operation with a operating bandwidth of 12.5 nm, in a device with a phase-shifter length of only 50 μm. Using the second structure, owing to a larger group index as well as lower spectral noise, we demonstrate 40 Gb/s operation with a phase-shifter length of only 90 μm, which is more than an order-of-magnitude shorter than most 40 Gb/s MZMs.

  18. Path to meter class single crystal silicon (SCSi) space optics

    NASA Astrophysics Data System (ADS)

    McCarter, Douglas R.

    2012-03-01

    With the global financial crisis affecting funding for space systems development, customers are calling for lower cost systems. Yet, at the same time, these lower cost systems must have increased thermal response to operational environments and load survivability. We submit that single crystal silicon (SCSi) meets both of these requirements. This paper will highlight some key SCSi material properties, discuss the opportunities that led to the development of McCarter processing methods, and present the latest steps in the manufacturing path of McCarter Mirrors using SCSi, GFB (glass frit bonding) and MSF (McCarter super finish), including the concept drawing of a one meter SCSi lightweight mirror, which together sets up the last step toward a lower cost, high performing one meter SCSi space optic.

  19. Laser induced crystallization of hydrogenated amorphous silicon-carbon alloys

    NASA Astrophysics Data System (ADS)

    Summonte, C.; Rizzoli, R.; Servidori, M.; Milita, S.; Nicoletti, S.; Bianconi, M.; Desalvo, A.; Iencinella, D.

    2004-10-01

    Laser induced crystallization of hydrogenated amorphous silicon carbon alloy (a-Si1-xCx:H) films has been investigated by means of synchrotron x-ray diffraction. The a-Si1-xCx:H films were deposited on (100) silicon wafers by very high frequency plasma enhanced chemical vapor deposition at 100MHz in hydrogen diluted silane-methane gas mixtures. The substrate was kept at 250°C or 350°C and the stoichiometry was changed from x =0.20 to 0.63. The structural characterization of the as-grown films has been carried out by Rutherford backscattering (hydrogen concentration) and infrared spectroscopy (film ordering). The films were irradiated by a KrF excimer laser (248nm ) with varying energy density and number of pulses. After irradiation, the formation of SiC crystallites has been revealed by synchrotron x-ray diffraction. Besides SiC nanocrystals, the formation of crystalline Si and graphite is observed for under- (x <0.50) and over-stoichiometric (x>0.50) samples, respectively. The essential role played by hydrogen concentration and hydrogen bonding configuration in determining the melting threshold and the consequent SiC grain formation is highlighted.

  20. Biomolecular screening with encoded porous-silicon photonic crystals

    NASA Astrophysics Data System (ADS)

    Cunin, Frédérique; Schmedake, Thomas A.; Link, Jamie R.; Li, Yang Yang; Koh, Jennifer; Bhatia, Sangeeta N.; Sailor, Michael J.

    2002-09-01

    Strategies to encode or label small particles or beads for use in high-throughput screening and bioassay applications focus on either spatially differentiated, on-chip arrays or random distributions of encoded beads. Attempts to encode large numbers of polymeric, metallic or glass beads in random arrays or in fluid suspension have used a variety of entities to provide coded elements (bits)-fluorescent molecules, molecules with specific vibrational signatures, quantum dots, or discrete metallic layers. Here we report a method for optically encoding micrometre-sized nanostructured particles of porous silicon. We generate multilayered porous films in crystalline silicon using a periodic electrochemical etch. This results in photonic crystals with well-resolved and narrow optical reflectivity features, whose wavelengths are determined by the etching parameters. Millions of possible codes can be prepared this way. Micrometre-sized particles are then produced by ultrasonic fracture, mechanical grinding or by lithographic means. A simple antibody-based bioassay using fluorescently tagged proteins demonstrates the encoding strategy in biologically relevant media.

  1. Biomolecular screening with encoded porous-silicon photonic crystals.

    PubMed

    Cunin, Frédérique; Schmedake, Thomas A; Link, Jamie R; Li, Yang Yang; Koh, Jennifer; Bhatia, Sangeeta N; Sailor, Michael J

    2002-09-01

    Strategies to encode or label small particles or beads for use in high-throughput screening and bioassay applications focus on either spatially differentiated, on-chip arrays or random distributions of encoded beads. Attempts to encode large numbers of polymeric, metallic or glass beads in random arrays or in fluid suspension have used a variety of entities to provide coded elements (bits)--fluorescent molecules, molecules with specific vibrational signatures, quantum dots, or discrete metallic layers. Here we report a method for optically encoding micrometre-sized nanostructured particles of porous silicon. We generate multilayered porous films in crystalline silicon using a periodic electrochemical etch. This results in photonic crystals with well-resolved and narrow optical reflectivity features, whose wavelengths are determined by the etching parameters. Millions of possible codes can be prepared this way. Micrometre-sized particles are then produced by ultrasonic fracture, mechanical grinding or by lithographic means. A simple antibody-based bioassay using fluorescently tagged proteins demonstrates the encoding strategy in biologically relevant media.

  2. Ferromagnetism in Silicon Single Crystals with Positively Charged Vacancy Clusters

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Zhang, Xinghong; Yuan, Quan; Han, Jiecai; Zhou, Shengqiang; Song, Bo

    Defect-induced ferromagnetism provides an alternative for organic and semiconductor spintronics. Here, we investigated the magnetism in Silicon after neutron irradiation and try to correlate the observed magnetism to particular defects in Si. Commercially available p-type Si single crystal wafer is cut into pieces for performing neutron irradiations. The magnetic impurities are ruled out as they can not be detected by secondary ion mass spectroscopy. With positron annihilation lifetime spectroscopy, the positron trapping center corresponding to lifetime 375 ps is assigned to a kind of stable vacancy clusters of hexagonal rings (V6) and its concentration is enhanced by increasing neutron doses. After irradiation, the samples still show strong diamagnetism. The weak ferromagnetic signal in Si after irradiation enhances and then weakens with increasing irradiation doses. The saturation magnetization at room temperature is almost the same as that at 5 K. The X-ray magnetic circular dichroism further provides the direct evidence that Silicon is the origin of this ferromagnetism. Using first-principles calculations, it is found that positively charged V6 brings the spin polarization and the defects have coupling with each other. The work is financially supported by the Helmholtz Postdoc Programme (Initiative and Networking Fund, PD-146).

  3. Crystallization and doping of amorphous silicon on low temperature plastic

    DOEpatents

    Kaschmitter, James L.; Truher, Joel B.; Weiner, Kurt H.; Sigmon, Thomas W.

    1994-01-01

    A method or process of crystallizing and doping amorphous silicon (a-Si) on a low-temperature plastic substrate using a short pulsed high energy source in a selected environment, without heat propagation and build-up in the substrate. The pulsed energy processing of the a-Si in a selected environment, such as BF3 and PF5, will form a doped micro-crystalline or poly-crystalline silicon (pc-Si) region or junction point with improved mobilities, lifetimes and drift and diffusion lengths and with reduced resistivity. The advantage of this method or process is that it provides for high energy materials processing on low cost, low temperature, transparent plastic substrates. Using pulsed laser processing a high (>900.degree. C.), localized processing temperature can be achieved in thin films, with little accompanying temperature rise in the substrate, since substrate temperatures do not exceed 180.degree. C. for more than a few microseconds. This method enables use of plastics incapable of withstanding sustained processing temperatures (higher than 180.degree. C.) but which are much lower cost, have high tolerance to ultraviolet light, have high strength and good transparency, compared to higher temperature plastics such as polyimide.

  4. Crystallization and doping of amorphous silicon on low temperature plastic

    DOEpatents

    Kaschmitter, J.L.; Truher, J.B.; Weiner, K.H.; Sigmon, T.W.

    1994-09-13

    A method or process of crystallizing and doping amorphous silicon (a-Si) on a low-temperature plastic substrate using a short pulsed high energy source in a selected environment, without heat propagation and build-up in the substrate is disclosed. The pulsed energy processing of the a-Si in a selected environment, such as BF3 and PF5, will form a doped micro-crystalline or poly-crystalline silicon (pc-Si) region or junction point with improved mobilities, lifetimes and drift and diffusion lengths and with reduced resistivity. The advantage of this method or process is that it provides for high energy materials processing on low cost, low temperature, transparent plastic substrates. Using pulsed laser processing a high (>900 C), localized processing temperature can be achieved in thin films, with little accompanying temperature rise in the substrate, since substrate temperatures do not exceed 180 C for more than a few microseconds. This method enables use of plastics incapable of withstanding sustained processing temperatures (higher than 180 C) but which are much lower cost, have high tolerance to ultraviolet light, have high strength and good transparency, compared to higher temperature plastics such as polyimide. 5 figs.

  5. Process development for single-crystal silicon solar cells

    NASA Astrophysics Data System (ADS)

    Bohra, Mihir H.

    Solar energy is a viable, rapidly growing and an important renewable alternative to other sources of energy generation because of its abundant supply and low manufacturing cost. Silicon still remains the major contributor for manufacturing solar cells accounting for 80% of the market share. Of this, single-crystal solar cells account for half of the share. Laboratory cells have demonstrated 25% efficiency; however, commercial cells have efficiencies of 16% - 20% resulting from a focus on implementation processes geared to rapid throughput and low cost, thereby reducing the energy pay-back time. An example would be the use of metal pastes which dissolve the dielectric during the firing process as opposed to lithographically defined contacts. With current trends of single-crystal silicon photovoltaic (PV) module prices down to 0.60/W, almost all other PV technologies are challenged to remain cost competitive. This presents a unique opportunity in revisiting the PV cell fabrication process and incorporating moderately more expensive IC process practices into PV manufacturing. While they may drive the cost toward a 1/W benchmark, there is substantial room to "experiment", leading to higher efficiencies which will help maintain the overall system cost. This work entails a turn-key process designed to provide a platform for rapid evaluation of novel materials and processes. A two-step lithographic process yielding a baseline 11% - 13% efficient cell is described. Results of three studies have shown improvements in solar cell output parameters due to the inclusion of a back-surface field implant, a higher emitter doping and also an additional RCA Clean.

  6. Silicon crystals: Process for manufacturing wafer-like silicon crystals with a columnar structure

    NASA Technical Reports Server (NTRS)

    Authier, B.

    1978-01-01

    Wafer-like crystals suitable for making solar cells are formed by pouring molten Si containing suitable dopants into a mold of the desired shape and allowing it to solidify in a temperature gradient, whereby the large surface of the melt in contact with the mold is kept at less than 200 D and the free surface is kept at a temperature of 200-1000 D higher, but below the melting point of Si. The mold can also be made in the form of a slit, whereby the 2 sides of the mold are kept at different temperatures. A mold was milled in the surface of a cylindrical graphite block 200 mm in diameter. The granite block was induction heated and the bottom of the mold was cooled by means of a water-cooled Cu plate, so that the surface of the mold in contact with one of the largest surfaces of the melt was held at approximately 800 D. The free surface of the melt was subjected to thermal radiation from a graphite plate located 2 mm from the surface and heated to 1500 D. The Si crystal formed after slow cooling to room temperature had a columnar structure and was cut with a diamond saw into wafers approximately 500 mm thick. Solar cells prepared from these wafers had efficiencies of 10 to 11%.

  7. Observation of higher order parametric x-ray spectra in mosaic graphite and single silicon crystals

    NASA Astrophysics Data System (ADS)

    Fiorito, R. B.; Rule, D. W.; Maruyama, X. K.; Dinova, K. L.; Evertson, S. J.; Osborne, M. J.; Snyder, D.; Rietdyk, H.; Piestrup, M. A.; Ho, A. H.

    1993-08-01

    We have observed up to 8 orders (n) in the spectra of parametric x-radiation (PXR) in the range 5-40 keV, produced by the interaction of a 90 MeV electron beam with mosaic graphite and single silicon crystals. The measured yields and intensity ratios, I(n>=2)/I(n=1), in graphite are not in agreement with the theory of PXR for mosaic crystals. In comparison, the ratios of intensities in silicon are close to the predictions of PXR theory for perfect crystals. The bandwidths of spectral lines measured in both silicon and graphite are in good agreement with theoretical predictions.

  8. The effect of pulse energy on the removal form of silicon crystal in electrical discharge machining

    NASA Astrophysics Data System (ADS)

    Mingbo, Qiu; Zongjun, Tian; Ye, Tian; Lida, Shen; Haoran, Chen; Hao, Ding

    2016-09-01

    A single-pulse discharge system for semiconductors was designed and produced. Single-pulse discharge experiments with single-crystal silicon were conducted, and the morphology of the electric erosion pit under different discharge energy levels was observed. Three removal forms, namely, heat removal, stress removal, and secondary crushing in electrical discharge machining (EDM) of single-crystal silicon, were discovered, and the mechanisms of semiconductor discharge processing were described. Finally, the role of different removal forms in single-crystal silicon EDM was explained and verified.

  9. Dual exposure, two-photon, conformal phasemask lithography for three dimensional silicon inverse woodpile photonic crystals

    SciTech Connect

    Shir, Daniel J.; Nelson, Erik C.; Chanda, Debashis; Brzezinski, Andrew; Braun, Paul V.; Rogers, John A.; Wiltzius, Pierre

    2010-01-01

    The authors describe the fabrication and characterization of three dimensional silicon inverse woodpile photonic crystals. A dual exposure, two-photon, conformal phasemask technique is used to create high quality polymer woodpile structures over large areas with geometries that quantitatively match expectations based on optical simulations. Depositing silicon into these templates followed by the removal of the polymer results in silicon inverse woodpile photonic crystals for which calculations indicate a wide, complete photonic bandgap over a range of structural fill fractions. Spectroscopic measurements of normal incidence reflection from both the polymer and siliconphotonic crystals reveal good optical properties.

  10. Crystallization of the glassy grain boundary phase in silicon nitride ceramics

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III

    1991-01-01

    The role was studied of the intergranular glassy phase in silicon nitride as-processed with yttria as a sintering aid. The microstructure, crystallization, and viscosity of the glassy phase were areas studied. Crystallization of the intergranular glassy phase to more refractory crystalline phases should improve the high temperature mechanical properties of the silicon nitride. The addition of a nucleating agent will increase the rate of crystallization. The measurement of the viscosity of the glassy phase will permit the estimation of the high temperature deformation of the silicon nitride.

  11. Material requirements for the adoption of unconventional silicon crystal and wafer growth techniques for high-efficiency solar cells

    SciTech Connect

    Hofstetter, Jasmin; del Cañizo, Carlos; Wagner, Hannes; Castellanos, Sergio; Buonassisi, Tonio

    2015-10-15

    Silicon wafers comprise approximately 40% of crystalline silicon module cost and represent an area of great technological innovation potential. Paradoxically, unconventional wafer-growth techniques have thus far failed to displace multicrystalline and Czochralski silicon, despite four decades of innovation. One of the shortcomings of most unconventional materials has been a persistent carrier lifetime deficit in comparison to established wafer technologies, which limits the device efficiency potential. In this perspective article, we review a defect-management framework that has proven successful in enabling millisecond lifetimes in kerfless and cast materials. Control of dislocations and slowly diffusing metal point defects during growth, coupled to effective control of fast-diffusing species during cell processing, is critical to enable high cell efficiencies. As a result, to accelerate the pace of novel wafer development, we discuss approaches to rapidly evaluate the device efficiency potential of unconventional wafers from injection-dependent lifetime measurements.

  12. Material requirements for the adoption of unconventional silicon crystal and wafer growth techniques for high-efficiency solar cells

    DOE PAGES

    Hofstetter, Jasmin; del Cañizo, Carlos; Wagner, Hannes; ...

    2015-10-15

    Silicon wafers comprise approximately 40% of crystalline silicon module cost and represent an area of great technological innovation potential. Paradoxically, unconventional wafer-growth techniques have thus far failed to displace multicrystalline and Czochralski silicon, despite four decades of innovation. One of the shortcomings of most unconventional materials has been a persistent carrier lifetime deficit in comparison to established wafer technologies, which limits the device efficiency potential. In this perspective article, we review a defect-management framework that has proven successful in enabling millisecond lifetimes in kerfless and cast materials. Control of dislocations and slowly diffusing metal point defects during growth, coupled tomore » effective control of fast-diffusing species during cell processing, is critical to enable high cell efficiencies. As a result, to accelerate the pace of novel wafer development, we discuss approaches to rapidly evaluate the device efficiency potential of unconventional wafers from injection-dependent lifetime measurements.« less

  13. Reusability of contaminated seed crystal for cast quasi-single crystalline silicon ingots

    NASA Astrophysics Data System (ADS)

    Li, Zaoyang; Liu, Lijun; Zhou, Genshu

    2015-04-01

    Reusing seed crystal is beneficial for reducing the production costs for cast quasi-single crystalline (QSC) silicon ingots. We numerically investigate the reusability of seed crystal in the casting processes with quartz crucible and silicon feedstock of different purities. The reused seed crystal is recycled from the standard QSC ingot and has been highly contaminated by iron impurity. Transient simulations of iron transport are carried out and special attention is paid to the diffusion and distribution characteristics of iron impurity at the ingot bottom. The heights of the bottom iron contaminated region are compared for silicon ingots grown from normal and recycled seed crystals. The results show that the purity of quartz crucible can influence the reusability of seed crystal more significantly than that of the feedstock. The recycled seed crystal with high iron concentration can be reused for casting processes with standard crucible, whereas it is not recommended for reusing for processes with pure crucible.

  14. Carbon-nanotube electron-beam (C-beam) crystallization technique for silicon TFTs

    NASA Astrophysics Data System (ADS)

    Lee, Su Woong; Kang, Jung Su; Park, Kyu Chang

    2016-02-01

    We introduced a carbon-nanotube (CNT) electron beam (C-beam) for thin film crystallization and thin film transistor (TFT) applications. As a source of electron emission, a CNT emitter which had been grown on a silicon wafer with a resist-assisted patterning (RAP) process was used. By using the C-beam exposure, we successfully crystallized a silicon thin film that had nano-sized crystalline grains. The distribution of crystalline grain size was about 10 ˜ 30 nm. This nanocrystalline silicon thin film definitely had three crystalline directions which are (111), (220) and (311), respectively. The silicon TFTs crystallized by using a C-beam exposure showed a field effect mobility of 20 cm2/Vs and an on/off ratio of more than 107. The C-beam exposure can modify the bonding network of amorphous silicon with its proper energy.

  15. Environmental Qualification of a Single-Crystal Silicon Mirror for Spaceflight Use

    NASA Technical Reports Server (NTRS)

    Hagopian, John; Chambers, John; Rohrback. Scott; Bly, Vincent; Morell, Armando; Budinoff, Jason

    2013-01-01

    This innovation is the environmental qualification of a single-crystal silicon mirror for spaceflight use. The single-crystal silicon mirror technology is a previous innovation, but until now, a mirror of this type has not been qualified for spaceflight use. The qualification steps included mounting, gravity change measurements, vibration testing, vibration- induced change measurements, thermal cycling, and testing at the cold operational temperature of 225 K. Typical mirrors used for cold applications for spaceflight instruments include aluminum, beryllium, glasses, and glass-like ceramics. These materials show less than ideal behavior after cooldown. Single-crystal silicon has been demonstrated to have the smallest change due to temperature change, but has not been spaceflight-qualified for use. The advantage of using a silicon substrate is with temperature stability, since it is formed from a stress-free single crystal. This has been shown in previous testing. Mounting and environmental qualification have not been shown until this testing.

  16. THE CRYSTAL STRUCTURE OF THE NEW SILICON CARBIDE POLYMORPH 69R,

    DTIC Science & Technology

    The 69R polymorph is one of the 32 silicon carbide polymorphs recently discovered by us. The space group is R3m and the unit cell is hexagonal with...and in two industrial silicon carbide crystal plates. They all pair with the fundamental type 6H. The five ways of pairing are: 6H + 69R + 87R, 6H

  17. Porous silicon-based two-dimensional photonic crystal for biochemical sensing applications

    NASA Astrophysics Data System (ADS)

    Mo, Jiaqing; Lv, Xiaoyi; Jia, Zhenhong

    2016-11-01

    Various porous silicon-based photonic device structures has attracted more attention for use as biochemical optical sensors. In this study, we have designed and characterized porous silicon-based two-dimensional photonic crystal waveguide structure as an optical biosensor. Field intensity distribution of two-dimensional photonic crystal waveguide was simulated using COMSOL Multiphysics. When the refractive index changes, the field strength changes greatly. This study lays the theoretical foundation for further work.

  18. Structural and energy properties of interstitial molecular hydrogen in single-crystal silicon

    SciTech Connect

    Melnikov, V. V.

    2015-06-15

    The structural and energy characteristics of interstitial molecular hydrogen in single-crystal silicon are theoretically studied. The dependence of the potential energy of the system on the position and orientation of the interstitial defect is investigated, and the mechanism of interaction of a hydrogen molecule with a silicon crystal is considered. A three-dimensional model is employed to calculate the energy spectrum of H{sub 2} in Si, and the obtained dispersion law is analyzed.

  19. X-ray and magnetic-field-enhanced change in physical characteristics of silicon crystals

    NASA Astrophysics Data System (ADS)

    Makara, V. A.; Steblenko, L. P.; Krit, A. N.; Kalinichenko, D. V.; Kurylyuk, A. N.; Naumenko, S. N.

    2012-07-01

    The effect of low-energy ( W = 8 keV) low-dose ((0.3-7.3) × 102 Gy) radiation and a dc magnetic field ( B = 0.17 T) on structural, micromechanical, and microplastic characteristics of silicon crystals has been studied. The features in the dynamic behavior of dislocations in silicon crystals, which manifest themselves upon only X-ray exposure and combined (X-ray and magnetic) exposure, have been revealed.

  20. Surface morphological instability of silicon (100) crystals under microwave ion physical etching

    NASA Astrophysics Data System (ADS)

    Yafarov, R. K.; Shanygin, V. Ya.

    2016-02-01

    This paper presents the results of studies of the dynamics of relaxation modification of the morphological characteristics of atomically clean surfaces of silicon (100) crystals with different types of conductivity after microwave ion physical etching in an argon atmosphere. For the first time, the effect of the electronic properties on the morphological characteristics and the surface free energy of silicon crystals is experimentally shown and proven by physicochemical methods.

  1. Growing Single Crystals From Low-Purity Silicon

    NASA Technical Reports Server (NTRS)

    Schmid, F.

    1984-01-01

    Heat exchanger method continuously moves impurities to outside of growth interface. Silicon heated in crucible to above melting point, and melted silicon then solidified by extracting heat from bottom of crucible by means of heat exchanger.

  2. High purith low defect FZ silicon

    NASA Technical Reports Server (NTRS)

    Kimura, H.; Robertson, G.

    1985-01-01

    The most common intrinsic defects in dislocation-free float zone (FZ) silicon crystals are the A- and B-type swirl defects. The mechanisms of their formation and annihilation have been extensively studied. Another type of defect in dislocation-free FZ crystals is referred to as a D-type defect. Concentrations of these defects can be minimized by optimizing the growth conditions, and the residual swirls can be reduced by the post-growth extrinsic gettering process. Czochralski (Cz) silicon wafers are known to exhibit higher resistance to slip and warpage due to thermal stress than do FZ wafers. The Cz crystals containing dislocations are more resistant to dislocation movement than dislocated FZ crystals because of the locking of dislocations by oxygen atoms present in the Cz crystals. Recently a transverse magnetic field was applied during the FZ growth of extrinsic silicon. Resultant flow patterns, as revealed by striation etching and spreading resistance in Ga-doped silicon crystals, indicate strong effects of the transverse magnetic field on the circulation within the melt. At fields of 5500 gauss, the fluid flow in the melt volume is so altered as to affect the morphology of the growing crystal.

  3. Microstructural analysis of the crystallization of silicon ribbons produced by the RGS process

    SciTech Connect

    Steinbach, I.; Hoefs, H.U.

    1997-12-31

    The microstructural evolution of multicrystalline silicon ribbons produced by the RGS process (Ribbon Growth on Substrate) is analyzed by numerical simulation. The crystallization model takes into account the faceted growth structure of silicon, thermal supercooling in front of the crystallization front and nucleation dependent on the thermal supercooling. The thermal conditions for the crystallization of the ribbon are taken from a macroscopic finite element simulation of the RGS process, as it is realized at Bayer AG, Germany. Different crystallization morphologies--single crystal, columnar multicrystal or dendritic--are discussed in their dependence on the process and nucleation conditions. The numerical results are compared to morphologies of silicon ribbons, grown on the pilot plant of Bayer AG, Germany.

  4. On the selection of prognostic equations for the rotating motion in simulating Czochralski flow

    SciTech Connect

    Kim, C.J.; Ro, S.T.

    1995-12-01

    When the fluid flow in the Czochralski crystal growth system involves swirling motion due to rotation effects, numerical simulation of the Czochralski flow can be performed using either the azimuthal velocity component or the angular momentum per unit mass, viz., the swirl, as the dependent variable to resolve the rotating motion. In the presence of a strong inward flow toward the axis, the Coriolis coupling in the azimuthal velocity equation can be a source of computational instability. This difficulty has been overcome by transforming the prognostic equation for the azimuthal velocity into the so-called swirl equation. In this article the authors show that although these two prognostic equations are mathematically identical to each other, numerical simulations based on them could yield appreciably different results under certain circumstances. This important as yet unresolved aspect of the Czochralski flow simulation is highlighted and the underlying cause of the discrepancy is addressed in the present study.

  5. Apparatus for making molten silicon

    NASA Technical Reports Server (NTRS)

    Levin, Harry (Inventor)

    1988-01-01

    A reactor apparatus (10) adapted for continuously producing molten, solar grade purity elemental silicon by thermal reaction of a suitable precursor gas, such as silane (SiH.sub.4), is disclosed. The reactor apparatus (10) includes an elongated reactor body (32) having graphite or carbon walls which are heated to a temperature exceeding the melting temperature of silicon. The precursor gas enters the reactor body (32) through an efficiently cooled inlet tube assembly (22) and a relatively thin carbon or graphite septum (44). The septum (44), being in contact on one side with the cooled inlet (22) and the heated interior of the reactor (32) on the other side, provides a sharp temperature gradient for the precursor gas entering the reactor (32) and renders the operation of the inlet tube assembly (22) substantially free of clogging. The precursor gas flows in the reactor (32) in a substantially smooth, substantially axial manner. Liquid silicon formed in the initial stages of the thermal reaction reacts with the graphite or carbon walls to provide a silicon carbide coating on the walls. The silicon carbide coated reactor is highly adapted for prolonged use for production of highly pure solar grade silicon. Liquid silicon (20) produced in the reactor apparatus (10) may be used directly in a Czochralski or other crystal shaping equipment.

  6. Optical studies of metastable properties of a defect with a zero-phonon transition at 0. 615 eV in 2-MeV electron-irradiated Czochralski-grown silicon

    SciTech Connect

    Svensson, J. H.; Monemar, B.

    1989-07-15

    Using infrared absorption spectroscopy, a new zero-phonon bound exciton(BE) line is found at 0.615 eV in 2-MeV electron-irradiated Czochralski-grownsilicon. The optical properties of this BE reveal an interesting metastabilityin the neutral charge state of the defect. After cooling the sample in darknessthis spectrum is initially very weak, but grows up after optical band-gapexcitation for several hours at low temperatures. An activation energy of 0.21eV is found for the thermal quenching of the line upon heating in darkness. Theoptical data are explained as connected with a carbon-related complex defectwith two different geometrical configurations in the neutral charge state.

  7. Apparatus and method for the horizontal, crucible-free growth of silicon sheet crystals

    DOEpatents

    Ciszek, Theodore F.

    1987-01-01

    Apparatus for continuously forming a silicon crystal sheet from a silicon rod in a noncrucible environment. The rod is rotated and fed toward an RF coil in an inert atmosphere so that the upper end of the rod becomes molten and the silicon sheet crystal is pulled therefrom substantially horizontally in a continuous strip. A shorting ring may be provided around the rod to limit the heating to the upper end only. Argon gas can be used to create the inert atmosphere within a suitable closed chamber. By use of this apparatus and method, a substantially defect-free silicon crystal sheet is formed that can be used for microcircuitry chips or solar cells.

  8. Apparatus and method for the horizontal, crucible-free growth of silicon sheet crystals

    DOEpatents

    Ciszek, T.F.

    1984-09-12

    Apparatus is provided for continuously forming a silicon crystal sheet from a silicon rod in a non-crucible environment. The rod is rotated and fed toward an RF coil in an inert atmosphere so that the upper end of the rod becomes molten and the silicon sheet crystal is pulled therefrom substantially horizontally in a continuous strip. A shorting ring may be provided around the rod to limit the heating to the upper end only. Argon gas can be used to create the inert atmosphere within a suitable closed chamber. By use of this apparatus and method, a substantially defect-free silicon crystal sheet is formed which can be used for micro-circuitry chips or solar cells.

  9. Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method

    PubMed Central

    2012-01-01

    A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared range. PMID:22824206

  10. Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method.

    PubMed

    Dang, Zhiya; Breese, Mark Bh; Recio-Sánchez, Gonzalo; Azimi, Sara; Song, Jiao; Liang, Haidong; Banas, Agnieszka; Torres-Costa, Vicente; Martín-Palma, Raúl José

    2012-07-23

    A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared range.

  11. SIMS Study of Elemental Diffusion During Solid Phase Crystallization of Amorphous Silicon

    SciTech Connect

    Reedy, R. C.; Young, D.; Branz, H. M.; Wang, Q.

    2005-11-01

    Crystallization of hydrogenated amorphous silicon (a-Si:H) films deposited on low-cost substrates shows potential for solar cell applications. Secondary ion mass spectrometry (SIMS) was used to study impurity incorporation, hydrogen evolution, and dopant diffusion during the crystallization process

  12. Electrical and Structural Characterization of Web Dendrite Crystals

    NASA Technical Reports Server (NTRS)

    Schwuttke, G. H.; Koliwad, K.; Dumas, K. A.

    1985-01-01

    Minority carrier lifetime distributions in silicon web dendrites are measured. Emphasis is placed on measuring areal homogeneity of lifetime, show its dependency on structural defects, and its unique change during hot processing. The internal gettering action of defect layers present in web crystals and their relation to minority carrier lifetime distributions is discussed. Minority carrier lifetime maps of web dendrites obtained before and after high temperature heat treatment are compared to similar maps obtained from 100 mm diameter Czochralski silicon wafers. Such maps indicate similar or superior areal homogeneity of minority carrier lifetime in webs.

  13. High-Q silicon-on-insulator slot photonic crystal cavity infiltrated by a liquid

    SciTech Connect

    Caër, Charles; Le Roux, Xavier; Cassan, Eric

    2013-12-16

    We report the experimental realization of a high-Q slot photonic crystal cavity in Silicon-On-Insulator (SOI) configuration infiltrated by a liquid. Loaded Q-factor of 23 000 is measured at telecom wavelength. The intrinsic quality factor inferred from the transmission spectrum is higher than 200 000, which represents a record value for slot photonic crystal cavities on SOI, whereas the maximum of intensity of the cavity is roughly equal to 20% of the light transmitted in the waveguide. This result makes filled slot photonic crystal cavities very promising for silicon-based light emission and ultrafast nonlinear optics.

  14. Devitrification and delayed crazing of SiO2 on single-crystal silicon and chemically vapor-deposited silicon nitride

    NASA Technical Reports Server (NTRS)

    Choi, Doo Jin; Scott, William D.

    1987-01-01

    The linear growth rate of cristobalite was measured in thin SiO2 films on silicon and chemically vapor-deposited silicon nitride. The presence of trace impurities from alumina furnace tubes greatly increased the crystal growth rate. Under clean conditions, the growth rate was still 1 order-of-magnitude greater than that for internally nucleated crystals in bulk silica. Crystallized films cracked and lifted from the surface after exposure to atmospheric water vapor. The crystallization and subsequent crazing and lifting of protective SiO2 films on silicon nitride should be considered in long-term applications.

  15. Thermal oxidation of 3C silicon carbide single-crystal layers on silicon

    NASA Technical Reports Server (NTRS)

    Fung, C. D.; Kopanski, J. J.

    1984-01-01

    Thermal oxidation of thick single-crystal 3C SiC layers on silicon substrates was studied. The oxidations were conducted in a wet O2 atmosphere at temperatures from 1000 to 1250 C for times from 0.1 to 50 h. Ellipsometry was used to determine the thickness and index of refraction of the oxide films. Auger analysis showed them to be homogeneous with near stoichiometric composition. The oxide growth followed a linear parabolic relationship with time. Activation energy of the parabolic rate constant was found to be 50 kcal/mole, while the linear rate constant was 74 kcal/mole. The latter value corresponds approximately to the energy required to break a Si-C bond. Electrical measurements show an effective density of 4-6 x 10 to the 11th per sq cm for fixed oxide charges at the oxide-carbide interface, and the dielectric strength of the oxide film is aproximately 6 x 10 to the 6th V/cm.

  16. Progress on the Dow Corning process for solar-grade silicon

    NASA Technical Reports Server (NTRS)

    Hunt, L. P.; Dosaj, V. D.

    1979-01-01

    The Dow Corning approach to increasing the resistivity of solar-grade silicon from about 0.04 ohm-cm (40 ppma B) to greater than 0.1 ohm-cm (10 ppma B) involves the use of high-purity raw materials carbothermically reduced in a specially designed electric arc furnace. Final purification occurs during Czochralski crystal growth of a polycrystalline ingot. This small-scale purification technology has resulted in silicon that has been fabricated into solar cells with a maximum AM1 conversion efficiency of 13.4%.

  17. Silicon ingot casting: Heat exchanger method. Multi-wire slicing: Fixed abrasive slicing technique, phase 3

    NASA Technical Reports Server (NTRS)

    Schmid, F.; Khattak, C. P.

    1979-01-01

    In the area of ingot casting the proof of concept of heat exchanger method (HEM) was established. It was also established that HEM cast silicon yielded solar cell performance comparable to Czochralski grown material. Solar cells with conversion efficiencies of up to 15% were fabricated. It was shown that square cross-section ingots can be cast. In the area of crystal slicing, it was established that silicon can be sliced efficiently with the fixed abrasive slicing technique approach. This concept was carried forward to 10 cm diameter workpiece.

  18. Thin Single Crystal Silicon Solar Cells on Ceramic Substrates: November 2009 - November 2010

    SciTech Connect

    Kumar, A.; Ravi, K. V.

    2011-06-01

    In this program we have been developing a technology for fabricating thin (< 50 micrometres) single crystal silicon wafers on foreign substrates. We reverse the conventional approach of depositing or forming silicon on foreign substrates by depositing or forming thick (200 to 400 micrometres) ceramic materials on high quality single crystal silicon films ~ 50 micrometres thick. Our key innovation is the fabrication of thin, refractory, and self-adhering 'handling layers or substrates' on thin epitaxial silicon films in-situ, from powder precursors obtained from low cost raw materials. This 'handling layer' has sufficient strength for device and module processing and fabrication. Successful production of full sized (125 mm X 125 mm) silicon on ceramic wafers with 50 micrometre thick single crystal silicon has been achieved and device process flow developed for solar cell fabrication. Impurity transfer from the ceramic to the silicon during the elevated temperature consolidation process has resulted in very low minority carrier lifetimes and resulting low cell efficiencies. Detailed analysis of minority carrier lifetime, metals analysis and device characterization have been done. A full sized solar cell efficiency of 8% has been demonstrated.

  19. Silicon Materials Task of the Low Cost Solar Array Project, Phase 3. Effect of Impurities and Processing on Silicon Solar Cells

    NASA Technical Reports Server (NTRS)

    Hopkins, R. H.; Davis, J. R.; Blais, P. D.; Rohatgi, A.; Campbell, R. B.; Rai-Choudhury, P.; Stapleton, R. E.; Mollenkopf, H. C.; Mccormick, J. R.

    1979-01-01

    The effects of impurities, various thermochemical processes, and any impurity process interactions on the performance of terrestrial silicon solar cells are defined. Determinations of the segregation coefficients of tungsten, tantalum, and cobalt for the Czochralski pulling of silicon single crystals are reported. Sensitive neutron activation analysis was used to determine the metal impurity content of the silicon while atomic absorption was used to measure the metal content of the residual liquid from which the doped crystals were grown. Gettering of Ti doped silicon wafers improved cell performance by one to two percent for the highest temperatures and longest times. The HCl is more effective than POCl3 treatments for deactivating Ti but POCl3 and HCl produced essentially identical results for Mo or Fe.

  20. Silicon-Germanium Alloys for Infrared Detectors.

    DTIC Science & Technology

    1980-04-01

    crystals, aiming at improved crystallinity and higher resistivity and to extend the Czochralski growth method to indium-doped Si-Ge alloys. Our intention...of the disappointingly high boron concentrations achieved in Czochralski growth, we decided to explore a crucible-free method for preparing Si-Ge...material was not high enough to allow an adequately long depletion region in a p-i-n detector. It does not appear that any Czochralski -type growth method

  1. Jan Czochralski: Brief sketch of his life and achievements

    NASA Astrophysics Data System (ADS)

    Pajaczkowska, Anna

    2014-09-01

    On the occasion of the 60th anniversary of the death and the approaching centenary of the discovery of the Czochralski method a brief sketch of biography and achievements of Professor Jan Czochralski is presented. Biography and scientific achievements of Jan Czochralski are associated with Kcynia hometown, and to his stay in Berlin, Frankfurt and Warsaw.

  2. Channeling, Volume Reection and Gamma Emission Using 14GeV Electrons in Bent Silicon Crystals

    SciTech Connect

    Benson, Brandon

    2015-08-14

    High energy electrons can be deflected with very tight bending radius using a bent silicon crystal. This produces gamma radiation. As these crystals can be thin, a series of bent silicon crystals with alternating direction has the potential to produce coherent gamma radiation with reasonable energy of the driving electron beam. Such an electron crystal undulator offers the prospect for higher energy radiation at lower cost than current methods. Permanent magnetic undulators like LCLS at SLAC National Accelerator Laboratory are expensive and very large (about 100 m in case of the LCLS undulator). Silicon crystals are inexpensive and compact when compared to the large magnetic undulators. Additionally, such a high energy coherent light source could be used for probing through materials currently impenetrable by x-rays. In this work we present the experimental data and analysis of experiment T523 conducted at SLAC National Accelerator Laboratory. We collected the spectrum of gamma ray emission from 14 GeV electrons on a bent silicon crystal counting single photons. We also investigated the dynamics of electron motion in the crystal i.e. processes of channeling and volume reflection at 14 GeV, extending and building off previous work. Our single photon spectrum for the amorphous crystal orientation is consistent with bremsstrahlung radiation and the volume reflection crystal orientation shows a trend consistent with synchrotron radiation at a critical energy of 740 MeV. We observe that in these two cases the data are consistent, but we make no further claims because of statistical limitations. We also extended the known energy range of electron crystal dechanneling length and channeling efficiency to 14 GeV.

  3. Development of low-cost silicon crystal growth techniques for terrestrial photovoltaic solar energy conversion

    NASA Technical Reports Server (NTRS)

    Zoutendyk, J. A.

    1976-01-01

    Because of the growing need for new sources of electrical energy, photovoltaic solar energy conversion is being developed. Photovoltaic devices are now being produced mainly from silicon wafers obtained from the slicing and polishing of cylindrically shaped single crystal ingots. Inherently high-cost processes now being used must either be eliminated or modified to provide low-cost crystalline silicon. Basic to this pursuit is the development of new or modified methods of crystal growth and, if necessary, crystal cutting. If silicon could be grown in a form requiring no cutting, a significant cost saving would potentially be realized. Therefore, several techniques for growth in the form of ribbons or sheets are being explored. In addition, novel techniques for low-cost ingot growth and cutting are under investigation.

  4. Development of low-cost silicon crystal growth techniques for terrestrial photovoltaic solar energy conversion

    NASA Technical Reports Server (NTRS)

    Zoutendyk, J. A.

    1976-01-01

    Because of the growing need for new sources of electrical energy, photovoltaic solar energy conversion is being developed. Photovoltaic devices are now being produced mainly from silicon wafers obtained from the slicing and polishing of cylindrically shaped single crystal ingots. Inherently high-cost processes now being used must either be eliminated or modified to provide low-cost crystalline silicon. Basic to this pursuit is the development of new or modified methods of crystal growth and, if necessary, crystal cutting. If silicon could be grown in a form requiring no cutting, a significant cost saving would potentially be realized. Therefore, several techniques for growth in the form of ribbons or sheets are being explored. In addition, novel techniques for low-cost ingot growth and cutting are under investigation.

  5. Crystal growth for high-efficiency silicon solar cells workshop: Summary

    NASA Technical Reports Server (NTRS)

    Dumas, K. A.

    1985-01-01

    The state of the art in the growth of silicon crystals for high-efficiency solar cells are reviewed, sheet requirements are defined, and furture areas of research are identified. Silicon sheet material characteristics that limit cell efficiencies and yields were described as well as the criteria for the ideal sheet-growth method. The device engineers wish list to the material engineer included: silicon sheet with long minority carrier lifetime that is uniform throughout the sheet, and which doesn't change during processing; and sheet material that stays flat throughout device processing, has uniform good mechanical strength, and is low cost. Impurities in silicon solar cells depreciate cell performance by reducing diffusion length and degrading junctions. The impurity behavior, degradation mechanisms, and variations in degradation threshold with diffusion length for silicon solar cells were described.

  6. The development of an inspection system for defects in silicon crystal growth

    NASA Astrophysics Data System (ADS)

    Liu, Ya-Cheng; Tsai, Hsin-Yi; Hung, Min-Wei; Huang, Kuo-Cheng

    2013-03-01

    This study presents an inspection system to detect the growth defects of silicon crystals that comprise a CCD camera, an LED light source, and power modulation. The defects on multicrystalline silicon can be observed clearly while the silicon wafer were irradiated by the red LED light at a small lighting angle (i.e., 20-30°). However, the growth defects on monocrystalline silicon wafer were difficult to observe because of it low image intensity. And then, the growth defects image was significantly enhanced when the wafer was illuminated by a white LED (WLED) and rotated at a specific angle (i.e., 23°). The experimental results showed that the WLED illumination system made the growth defects more easily observable than did other LED sources (i.e., red, blue, and green LEDs). In addition, the proposed inspection system can be used for on-line fast detection for quality control of monocrystalline silicon wafer.

  7. Effect of oxygen and nitrogen interactions on friction of single-crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1978-01-01

    Friction studies were conducted with single-crystal silicon carbide contacting silicon carbide and titanium after having been exposed to oxygen and nitrogen in various forms. After they had been sputter cleaned, the surfaces were (1) exposed to gaseous oxygen and nitrogen (adsorption), (2) ion bombarded with oxygen and nitrogen, or (3) reacted with oxygen (SiC only). Auger emission spectroscopy was used to determine the presence of oxygen and nitrogen. The results indicate that the surfaces of silicon carbide with reacted and ion-bombarded oxygen ions give higher coefficients of friction than do argon sputter-cleaned surfaces. The effects of oxygen on friction may be related to the relative chemical, thermodynamic properties of silicon, carbon, and titanium for oxygen. The adsorbed films of oxygen, nitrogen, and mixed gases of oxygen and nitrogen on sputter-cleaned, oxygen-ion bombarded, and oxygen-reacted surfaces generally reduce friction. Adsorption to silicon carbide is relatively weak.

  8. Photoluminescence at room temperature of liquid-phase crystallized silicon on glass

    NASA Astrophysics Data System (ADS)

    Vetter, Michael; Schwuchow, Anka; Andrä, Gudrun

    2016-12-01

    The room temperature photoluminescence (PL) spectrum due band-to-band recombination in an only 8 μm thick liquid-phase crystallized silicon on glass solar cell absorber is measured over 3 orders of magnitude with a thin 400 μm thick optical fiber directly coupled to the spectrometer. High PL signal is achieved by the possibility to capture the PL spectrum very near to the silicon surface. The spectra measured within microcrystals of the absorber present the same features as spectra of crystalline silicon wafers without showing defect luminescence indicating the high electronic material quality of the liquid-phase multi-crystalline layer after hydrogen plasma treatment.

  9. Melting and crystallization of nanocrystalline silicon microwires through rapid self-heating

    NASA Astrophysics Data System (ADS)

    Bakan, G.; Cywar, A.; Silva, H.; Gokirmak, A.

    2009-06-01

    Nanocrystalline silicon microwires are self-heated through single, large amplitude, and microsecond voltage pulses. Scanning electron micrographs show very smooth wire surfaces after the voltage pulse compared to as-fabricated nanocrystalline texture. Voltage-pulse induced self-heating leads to significant conductance improvement, suggesting crystallization of the wires. The minimum resistivity during the pulse is extracted from wires of different dimensions as 75.0±4.6 μΩ cm, matching previously reported values for liquid silicon. Hence, nanocrystalline silicon microwires melt through self-heating during the voltage pulse and resolidify upon termination of the pulse, resulting in very smooth and less-resistive crystalline structures.

  10. Effect of crystal plane orientation on tribochemical removal of monocrystalline silicon

    NASA Astrophysics Data System (ADS)

    Xiao, Chen; Guo, Jian; Zhang, Peng; Chen, Cheng; Chen, Lei; Qian, Linmao

    2017-01-01

    The effect of crystal plane orientation on tribochemical removal of monocrystalline silicon was investigated using an atomic force microscope. Experimental results indicated that the tribochemical removal of silicon by SiO2 microsphere presented strong crystallography-induced anisotropy. Further analysis suggested that such anisotropic tribochemical removal of silicon was not dependent on the crystallography-dependent surface mechanical properties (i.e., hardness and elastic modulus), but was mainly attributed to various atomic planar density and interplanar spacing in different crystal planes. Phenomenological results speculated that higher density of silicon atom could promote the formation of Si-O-Si bonds between the SiO2 microsphere and silicon substrate, resulting in more severe tribochemical material removal. Larger interplanar spacing with smaller energy barrier facilitated the rupture of the Si-Si network with the help of mechanical shearing stress, which caused more serious wear of the silicon surface. The results may help understand the material removal mechanism of silicon and provide useful knowledge for chemical mechanical polishing.

  11. Effect of crystal plane orientation on tribochemical removal of monocrystalline silicon

    PubMed Central

    Xiao, Chen; Guo, Jian; Zhang, Peng; Chen, Cheng; Chen, Lei; Qian, Linmao

    2017-01-01

    The effect of crystal plane orientation on tribochemical removal of monocrystalline silicon was investigated using an atomic force microscope. Experimental results indicated that the tribochemical removal of silicon by SiO2 microsphere presented strong crystallography-induced anisotropy. Further analysis suggested that such anisotropic tribochemical removal of silicon was not dependent on the crystallography-dependent surface mechanical properties (i.e., hardness and elastic modulus), but was mainly attributed to various atomic planar density and interplanar spacing in different crystal planes. Phenomenological results speculated that higher density of silicon atom could promote the formation of Si-O-Si bonds between the SiO2 microsphere and silicon substrate, resulting in more severe tribochemical material removal. Larger interplanar spacing with smaller energy barrier facilitated the rupture of the Si-Si network with the help of mechanical shearing stress, which caused more serious wear of the silicon surface. The results may help understand the material removal mechanism of silicon and provide useful knowledge for chemical mechanical polishing. PMID:28084433

  12. Density comparison measurements of silicon crystals by a pressure-of-flotation method at NMIJ

    NASA Astrophysics Data System (ADS)

    Waseda, A.; Fujii, K.

    2004-04-01

    A new density comparison apparatus based on a pressure-of-flotation method (PFM) is presented. Density comparison measurements are performed for a new silicon crystal of the National Metrology Institute of Japan (NMIJ) for the density standard and determination of the Avogadro constant. The density comparison measurement of silicon crystals by the new PFM apparatus has an estimated relative standard uncertainty of 4.0 × 10-8. Adjusted values of density are evaluated from the data of the PFM and absolute measurements using a least-squares algorithm, where correlations are taken into consideration.

  13. 40 GHz electro-optic modulation in hybrid silicon-organic slotted photonic crystal waveguides.

    PubMed

    Wülbern, Jan Hendrik; Prorok, Stefan; Hampe, Jan; Petrov, Alexander; Eich, Manfred; Luo, Jingdong; Jen, Alex K-Y; Jenett, Martin; Jacob, Arne

    2010-08-15

    In this Letter we demonstrate broadband electro-optic modulation with frequencies of up to 40 GHz in slotted photonic crystal waveguides based on silicon-on-insulator substrates covered and infiltrated with a nonlinear optical polymer. Two-dimensional photonic crystal waveguides in silicon enable integrated optical devices with an extremely small geometric footprint on the scale of micrometers. The slotted waveguide design optimizes the overlap of the optical and electric fields in the second-order nonlinear optical medium and, hence, the interaction of the optical and electric waves.

  14. Silicon nano-membrane based photonic crystal microcavities for high sensitivity bio-sensing

    PubMed Central

    Lai, Wei-Cheng; Chakravarty, Swapnajit; Zou, Yi; Chen, Ray T.

    2012-01-01

    We experimentally demonstrated photonic crystal microcavity based resonant sensors coupled to photonic crystal waveguides in silicon nano-membrane on insulator for chemical and bio-sensing. Linear L-type microcavities are considered. In contrast to cavities with small mode volumes, but low quality factors for bio-sensing, we showed increasing the length of the microcavity enhances the quality factor of the resonance by an order of magnitude and increases the resonance wavelength shift while retaining compact device characteristics. Q~26760 and sensitivity down to 15 ng/ml and~110 pg/mm2 in bio-sensing was experimentally demonstrated on silicon-on-insulator devices. PMID:22466197

  15. Silicon nano-membrane based photonic crystal microcavities for high sensitivity bio-sensing.

    PubMed

    Lai, Wei-Cheng; Chakravarty, Swapnajit; Zou, Yi; Chen, Ray T

    2012-04-01

    We experimentally demonstrated photonic crystal microcavity based resonant sensors coupled to photonic crystal waveguides in silicon nano-membrane on insulator for chemical and bio-sensing. Linear L-type microcavities are considered. In contrast to cavities with small mode volumes, but low quality factors for bio-sensing, we showed increasing the length of the microcavity enhances the quality factor of the resonance by an order of magnitude and increases the resonance wavelength shift while retaining compact device characteristics. Q~26760 and sensitivity down to 15 ng/ml and ~110 pg/mm2 in bio-sensing was experimentally demonstrated on silicon-on-insulator devices.

  16. Distribution of oxygen in silicon and its effects on electronic characteristics on a microscale

    NASA Technical Reports Server (NTRS)

    Gatos, H. C.; Rava, P.; Lagowski, J. J.

    1980-01-01

    The microdistribution of oxygen in silicon was obtained by scanning IR absorption in as grown Czochralski crystals. The crystals were subsequently submitted to various heat treatments. The profiles of the generated thermal donors were determined by spreading resistance measurements. Contrary to the prevailing views, it was found that the concentration of the activated thermal donors is not strictly a function of the oxygen concentration, but depends strongly on an additional factor, which was shown to be associated with vacancy concentration. These conclusions could only be reached on the basis of microscale characterization. In fact, commonly employed macroscale analysis has led to erroneous conclusions.

  17. Investigations of YAG:Er(3+),Yb(3+) and YAG:Co(2+) Crystals for Laser Applications

    DTIC Science & Technology

    2001-01-01

    doped YAG crystals are given. Erbium and ytterbium doped YAG single crystals were obtained by the Czochralski method . The spectral properties and laser...relaxation time of 290 Rts14 2. CRYSTAL GROWTH The crystals were obtained by the Czochralski method , using iridium crucibles of external dimensions...YAG:Co 2+ single crystal grown by Czochralski method is presented. In all obtained crystals the core area of the characteristic threefold symmetry was

  18. Dendritic web silicon for solar cell application

    NASA Technical Reports Server (NTRS)

    Seidensticker, R. G.

    1977-01-01

    The dendritic web process for growing long thin ribbon crystals of silicon and other semiconductors is described. Growth is initiated from a thin wirelike dendrite seed which is brought into contact with the melt surface. Initially, the seed grows laterally to form a button at the melt surface; when the seed is withdrawn, needlelike dendrites propagate from each end of the button into the melt, and the web portion of the crystal is formed by the solidification of the liquid film supported by the button and the bounding dendrites. Apparatus used for dendritic web growth, material characteristics, and the two distinctly different mechanisms involved in the growth of a single crystal are examined. The performance of solar cells fabricated from dendritic web material is indistinguishable from the performance of cells fabricated from Czochralski grown material.

  19. Dendritic web silicon for solar cell application

    NASA Technical Reports Server (NTRS)

    Seidensticker, R. G.

    1977-01-01

    The dendritic web process for growing long thin ribbon crystals of silicon and other semiconductors is described. Growth is initiated from a thin wirelike dendrite seed which is brought into contact with the melt surface. Initially, the seed grows laterally to form a button at the melt surface; when the seed is withdrawn, needlelike dendrites propagate from each end of the button into the melt, and the web portion of the crystal is formed by the solidification of the liquid film supported by the button and the bounding dendrites. Apparatus used for dendritic web growth, material characteristics, and the two distinctly different mechanisms involved in the growth of a single crystal are examined. The performance of solar cells fabricated from dendritic web material is indistinguishable from the performance of cells fabricated from Czochralski grown material.

  20. Study of silicon strip waveguides with diffraction gratings and photonic crystals tuned to a wavelength of 1.5 µm

    SciTech Connect

    Barabanenkov, M. Yu. Vyatkin, A. F.; Volkov, V. T.; Gruzintsev, A. N.; Il’in, A. I.; Trofimov, O. V.

    2015-12-15

    Single-mode submicrometer-thick strip waveguides on silicon-on-insulator substrates, fabricated by silicon-planar-technology methods are considered. To solve the problem of 1.5-µm wavelength radiation input-output and its frequency filtering, strip diffraction gratings and two-dimensional photonic crystals are integrated into waveguides. The reflection and transmission spectra of gratings and photonic crystals are calculated. The waveguide-mode-attenuation coefficient for a polycrystalline silicon waveguide is experimentally estimated.

  1. Solid-phase crystallization of amorphous silicon nanowire array and optical properties

    NASA Astrophysics Data System (ADS)

    Ishikawa, Ryousuke; Kato, Shinya; Yamazaki, Tatsuya; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Konagai, Makoto

    2014-02-01

    An amorphous silicon nanowire (a-SiNW) array perpendicular to a glass substrate can be successfully obtained through the metal-assisted chemical etching of amorphous silicon (a-Si) thin films. The solid-phase crystallization of a-SiNWs was carried out by thermal annealing in a forming gas in the temperature range from 600 to 900 °C. The effects of hydrogen in the film and the film morphology on the crystallization of a-SiNWs were investigated by Raman spectroscopy and transmission electron microscopy. A higher hydrogen concentration of a-SiNWs reduced the crystallization temperature, as in a-Si thin films. It was also revealed that the large surface area of the a-SiNW array affected the crystallization process. We also studied the optical property of the fabricated SiNW array and demonstrated its high potential as an active layer in solar cells.

  2. Hydrogenated amorphous silicon nitride photonic crystals for improved-performance surface electromagnetic wave biosensors.

    PubMed

    Sinibaldi, Alberto; Descrovi, Emiliano; Giorgis, Fabrizio; Dominici, Lorenzo; Ballarini, Mirko; Mandracci, Pietro; Danz, Norbert; Michelotti, Francesco

    2012-10-01

    We exploit the properties of surface electromagnetic waves propagating at the surface of finite one dimensional photonic crystals to improve the performance of optical biosensors with respect to the standard surface plasmon resonance approach. We demonstrate that the hydrogenated amorphous silicon nitride technology is a versatile platform for fabricating one dimensional photonic crystals with any desirable design and operating in a wide wavelength range, from the visible to the near infrared. We prepared sensors based on photonic crystals sustaining either guided modes or surface electromagnetic waves, also known as Bloch surface waves. We carried out for the first time a direct experimental comparison of their sensitivity and figure of merit with surface plasmon polaritons on metal layers, by making use of a commercial surface plasmon resonance instrument that was slightly adapted for the experiments. Our measurements demonstrate that the Bloch surface waves on silicon nitride photonic crystals outperform surface plasmon polaritons by a factor 1.3 in terms of figure of merit.

  3. Impurities in silicon solar cells

    NASA Technical Reports Server (NTRS)

    Hopkins, R. H.

    1985-01-01

    Metallic impurities, both singly and in combinations, affect the performance of silicon solar cells. Czochralski silicon web crystals were grown with controlled additions of secondary impurities. The primary electrical dopants were boron and phosphorus. The silicon test ingots were grown under controlled and carefully monitored conditions from high-purity charge and dopant material to minimize unintentional contamination. Following growth, each crystal was characterized by chemical, microstructural, electrical, and solar cell tests to provide a detailed and internally consistent description of the relationships between silicon impurity concentration and solar cell performance. Deep-level spectroscopy measurements were used to measure impurity concentrations at levels below the detectability of other techniques and to study thermally-induced changes in impurity activity. For the majority of contaminants, impurity-induced performance loss is due to a reduction of the base diffusion length. From these observations, a semi-empirical model which predicts cell performance as a function of metal impurity concentration was formulated. The model was then used successfully to predict the behavior of solar cells bearing as many as 11 different impurities.

  4. Surface property modification of silicon

    NASA Technical Reports Server (NTRS)

    Danyluk, S.

    1984-01-01

    The main emphasis of this work has been to determine the wear rate of silicon in fluid environments and the parameters that influence wear. Three tests were carried out on single crystal Czochralski silicon wafers: circular and linear multiple-scratch tests in fluids by a pyramidal diamond simulated fixed-particle abrasion; microhardness and three-point bend tests were used to determine the hardness and fracture toughness of abraded silicon and the extent of damage induced by abrasion. The wear rate of (100) and (111) n and p-type single crystal Cz silicon abraded by a pyramidal diamond in ethanol, methanol, acetone and de-ionized water was determined by measuring the cross-sectional areas of grooves of the circular and linear multiple-scratch tests. The wear rate depends on the loads on the diamond and is highest for ethanol and lowest for de-ionized water. The surface morphology of the grooves showed lateral and median cracks as well as a plastically deformed region. The hardness and fracture toughness are critical parameters that influence the wear rate. Microhardness tests were conducted to determine the hardness as influenced by fluids. Median cracks and the damage zone surrounding the indentations were also related to the fluid properties.

  5. Boron Partitioning Coefficient above Unity in Laser Crystallized Silicon

    PubMed Central

    Lill, Patrick C.; Dahlinger, Morris; Köhler, Jürgen R.

    2017-01-01

    Boron pile-up at the maximum melt depth for laser melt annealing of implanted silicon has been reported in numerous papers. The present contribution examines the boron accumulation in a laser doping setting, without dopants initially incorporated in the silicon wafer. Our numerical simulation models laser-induced melting as well as dopant diffusion, and excellently reproduces the secondary ion mass spectroscopy-measured boron profiles. We determine a partitioning coefficient kp above unity with kp=1.25±0.05 and thermally-activated diffusivity DB, with a value DB(1687K)=(3.53±0.44)×10−4 cm2·s−1 of boron in liquid silicon. For similar laser parameters and process conditions, our model predicts the anticipated boron profile of a laser doping experiment. PMID:28772548

  6. Wear particles of single-crystal silicon carbide in vacuum

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1980-01-01

    Sliding friction experiments, conducted in vacuum with silicon carbide /000/ surface in contact with iron based binary alloys are described. Multiangular and spherical wear particles of silicon carbide are observed as a result of multipass sliding. The multiangular particles are produced by primary and secondary cracking of cleavage planes /000/, /10(-1)0/, and /11(-2)0/ under the Hertzian stress field or local inelastic deformation zone. The spherical particles may be produced by two mechanisms: (1) a penny shaped fracture along the circular stress trajectories under the local inelastic deformation zone, and (2) attrition of wear particles.

  7. Micromachined crystal plane on (100) and (110) silicon for optical mirror applications

    NASA Astrophysics Data System (ADS)

    Resnik, Drago; Vrtacnik, Danilo; Aljancic, Uros; Amon, Slavko

    2004-04-01

    Silicon crystal planes that can be potentially used as optical mirrors for deflecting light beams from/to optical fibres aligned in grooves were investigated. Aligning grooves and passive mirror-like planes were formed by wet micromachining in KOH and TMAH etchants with addition of additives such as IPA and Triton surfactant. On (100) silicon, {111}, {110}, {311} mirror planes were realized, while on (110) silicon, {010} and {111} mirror planes were demonstrated for the chosen mask orientation. Characterization of passive mirrors with 632nm incident light was performed by measuring angles and specific shape patterns of reflected light beams and by determination of light scattering due to mirror microroughness. Results show that {111} planes exhibit better surface quality compared to {110} mirrors and lowest scattering, however the reflected angle is 54,74° on (100) silicon. On (110) silicon the 45° reflection angle with {010} crystal planes is obtained by proper mask alignment with very small scattering angle below 3°. For reflecting the beam with 1,33 μm wavelength, sputtered layer of aluminum is used as reflecting coating on silicon mirrors, increasing the reflectivity by 24%.

  8. Crystal Lattice Dynamics of Various Silicon-Carbide Polytypes

    DTIC Science & Technology

    2001-01-01

    basis of these results. 2. SILICON CARBIDE POLYTYPES It is well known that close packed spheres form a face centred cubic structure or a hexagonal...polytypism. The simplest polytype, called 3C, has the cubic structure of sphalerite. The polytype 2H has the hexagonal structure of wurtzite. The

  9. Modeling phosphorus diffusion gettering of iron in single crystal silicon

    NASA Astrophysics Data System (ADS)

    Haarahiltunen, A.; Savin, H.; Yli-Koski, M.; Talvitie, H.; Sinkkonen, J.

    2009-01-01

    We propose a quantitative model for phosphorus diffusion gettering (PDG) of iron in silicon, which is based on a special fitting procedure to experimental data. We discuss the possibilities of the underlying physics of the segregation coefficient. Finally, we show that the proposed PDG model allows quantitative analysis of gettering efficiency of iron at various processing conditions.

  10. Properties of reinforced carbon nanotube and laser-crystallized silicon films

    NASA Astrophysics Data System (ADS)

    Semler, Matthew Roy

    Flexible electronics are anticipated to be one of the next technological advancements of electronic devices. The enhanced durability, light-weight nature, and conformity of flexible electronics are desired properties in a variety of fields and are anticipated to reduce production costs. Two promising materials for use in flexible electronics are carbon nanotube (CNT) films and laser-crystallized thin silicon films. CNTs are in their infancy in respect to their presence in electronic devices; however their superb mechanical and electronic properties make them ideal candidates for flexible electronics. Thin silicon films are a natural transition from bulk silicon as bulk silicon has been the preferred material in electronics since the dawn of the transistor. Thin-film silicon retains the well-studied electronic properties of bulk silicon; however, it becomes flexible as it is thinned. Obstacles to the application of both these materials in flexible electronics nonetheless exist. Compressed CNT films undergo strain softening---a mechanism in which the CNT film restructures itself in response to an applied strain, which reduces the Young's modulus and electronic conductivity. In this dissertation, thin CNT films are capped with a thin polymer layer, with the aim to mitigate strain softening through excluded volume interactions in a bilayer format that serves as a paradigm for more sophisticated device relevant settings. More specifically, metallic and semiconducting CNT films of different thicknesses are capped with a polystyrene film of comparable thickness, and the mechanical and electronic strain response of the capped CNT film is examined and discussed. Ultrathin silicon films cannot be grown as monocrystalline silicon, so amorphous silicon films must be deposited and crystallized. Laser crystallization is an alternative to oven annealing and has a faster throughput. In this dissertation, amorphous silicon films of various thicknesses were deposited on several

  11. Observation of Transparency of Erbium-doped Silicon Nitride in Photonic Crystal Nanobeam Cavities

    DTIC Science & Technology

    2010-06-21

    Neu, and C. Becher, “Design of Photonic Crystal Microcavities in Diamond Films,” Opt. Express 16, 1632-1644 (2008). 9. M. Eichenfield, R. Camacho , J...effort to fabricate light emitting devices with Silicon complementary metal-oxide- semiconductor (Si-CMOS) compat- ible materials. One possible material

  12. Experimental demonstration of analog signal transmission in a silicon photonic crystal L3 resonator.

    PubMed

    Gui, Chengcheng; Zhang, Yong; Du, Jing; Xia, Jinsong; Wang, Jian

    2015-06-01

    We design and fabricate a silicon photonic crystal L3 resonator for chip-scale analog signal transmission. The lattice constant (a) is 420 nm, and the radius of holes (r) is 126 nm. The three holes adjacent to the cavity are laterally shifted by 0.175a, 0.025a and 0.175a, respectively. We experimentally evaluate the performance of silicon photonic crystal L3 resonator for chip-scale analog signal transmission. The spurious free dynamic ranges (SFDRs) of the second-order harmonic distortion (SHD) and the third-order harmonic distortion (THD), which are important factors to assess the analog link performance, are measured for the chip-scale analog signal transmission through the fabricated silicon photonic crystal L3 resonator. The SHD SFDR and THD SFDR are measured to be ~34.6 dB and ~52.2 dB even with the input optical carrier sitting at the dip resonance wavelength of the fabricated silicon photonic crystal L3 resonator. The influences of the optical carrier wavelength and input optical power on the SHD SFDR and THD SFDR are studied in the experiment. The impacts of geometric parameters of the cavity structure (lattice constant, radius of holes, shift of the hole) on the analog signal transmission are also analyzed, showing favorable analog link performance with relatively large fabrication tolerance to design parameters.

  13. Origin of SiC impurities in silicon crystals grown from the melt in vacuums

    NASA Technical Reports Server (NTRS)

    Schmid, F.; Khattak, C. P.; Digges, T. G., Jr.; Kaufman, L.

    1982-01-01

    A main source of high carbon levels in silicon crystals grown from melt under reduced pressures and contained in silica crucibles supported by graphite retainer/susceptor was identified by thermodynamic analysis. The calculations were verified by experimental results and the carbon level is reduced by approximately 50% with the use of molybdenum retainers.

  14. Crystallization behavior of three-dimensional silica fiber reinforced silicon nitride composite

    NASA Astrophysics Data System (ADS)

    Qi, Gongjin; Zhang, Changrui; Hu, Haifeng; Cao, Feng; Wang, Siqing; Jiang, Yonggang; Li, Bin

    2005-10-01

    The crystallization behavior of a new type of ceramic matrix composites, three-dimensional silica fiber reinforced silicon nitride matrix composite prepared by perhydropolysilazane infiltration and pyrolysis, was investigated by X-ray diffractometry and Fourier transform infrared spectroscopy. With the post-annealing treatment of the amorphous as-received composite at elevated tempertures of 1400 and 1600 °C in nitrogen atmosphere, there was remarkable suppression of the crystallization of polymer-derived silicon nitride ceramic matrix into α-Si 3N 4 and silica fibers into α-cristobalite, which was probably attributed to the phase of silicon oxynitrides originating from the strong fiber/matrix interfacial chemical reaction.

  15. Coupled optical and electrical modeling of solar cell based on conical pore silicon photonic crystals

    NASA Astrophysics Data System (ADS)

    Deinega, Alexei; Eyderman, Sergey; John, Sajeev

    2013-06-01

    We compare the efficiency of thin film photonic crystal solar cells consisting of conical pores and nanowires. Solving both Maxwell's equations and the semiconductor drift-diffusion in each geometry, we identify optimal junction and contact positions and study the influence of bulk and surface recombination losses on solar cell efficiency. We find that using only 1 μm of silicon, sculpted in the form of an inverted slanted conical pore photonic crystal film, and using standard contact recombination velocities, solar power conversion efficiency of 17.5% is obtained when the carrier diffusion length exceeds 10 μm. Reducing the contact recombination velocity to 100 cm s-1 yields efficiency up to 22.5%. Further efficiency improvements are possible (with 1 μm of silicon) in a tandem cell with amorphous silicon at the top.

  16. Enhanced efficiency of ultrathin (˜500 nm)-film microcrystalline silicon photonic crystal solar cells

    NASA Astrophysics Data System (ADS)

    De Zoysa, Menaka; Ishizaki, Kenji; Tanaka, Yoshinori; Sai, Hitoshi; Matsubara, Koji; Noda, Susumu

    2017-01-01

    Enhancing the absorption of thin-film microcrystalline silicon solar cells at 600-1000 nm wavelengths is very important to the improvement of the energy conversion efficiency. This can be achieved by creating a large number of resonant modes utilizing two-dimensional photonic crystal band edges, which exceeds the Lambertian limit of absorption in random textures. We focus on suppressing the parasitic absorption of back-reflector metal and doped layers in photonic crystal microcrystalline silicon solar cells. We achieve a high active-area current density of 22.6 mA cm-2 for an ultrathin (˜500 nm)-film silicon layer and obtain an active-area efficiency of ˜9.1%, as independently confirmed by the CSMT of AIST.

  17. Single crystal silicon capacitors with low microwave loss in the single photon regime

    NASA Astrophysics Data System (ADS)

    Weber, S. J.; Murch, K. W.; Slichter, D. H.; Vijay, R.; Siddiqi, I.

    2011-04-01

    We have fabricated superconducting microwave resonators in a lumped element geometry using single crystal silicon dielectric parallel plate capacitors with C >2 pF. Aluminum devices with resonant frequencies between 4.0 and 6.5 GHz exhibited an average internal quality factor Qi of 2×105 in the single photon excitation regime at T =20 mK. Attributing the observed loss solely to the capacitive element, our measurements place an upper bound on the loss tangent of the silicon dielectric layer of tan δi=5×10-6. This level of loss is an order of magnitude lower than is currently observed in structures incorporating amorphous dielectric materials, thus making single crystal silicon capacitors an attractive, robust route for realizing long-lived quantum circuits.

  18. Study of polycrystalline silicon obtained by aluminum-induced crystallization depending on process conditions

    NASA Astrophysics Data System (ADS)

    Pereyaslavtsev, Alexander; Sokolov, Igor; Sinev, Leonid

    2016-11-01

    In this paper, we have decided to consider an alternative method of producing polycrystalline silicon and study change of its electrophysical characteristics depending on process parameters. As an alternative low-pressure chemical vapor deposition method appears aluminum-induced crystallization (AIC), which allows to obtain a polycrystalline silicon film is significantly larger grain size, thereby reducing contribution of grain boundaries. A comprehensive study of polycrystalline silicon was carried out using a variety of microscopic (OM, SEM) and spectroscopic (RAMAN, XPS) and diffraction (EBSD, XRD) analytic methods. We also considered possibility of self-doping in AIC, result of which was obtained polycrystalline silicon with different resistance. Additionally considered changes in temperature coefficient of resistance depending on technological parameters of AIC process.

  19. Thermal load leveling during silicon crystal growth from a melt using anisotropic materials

    DOEpatents

    Carlson, Frederick M.; Helenbrook, Brian T.

    2016-10-11

    An apparatus for growing a silicon crystal substrate comprising a heat source, an anisotropic thermal load leveling component, a crucible, and a cold plate component is disclosed. The anisotropic thermal load leveling component possesses a high thermal conductivity and may be positioned atop the heat source to be operative to even-out temperature and heat flux variations emanating from the heat source. The crucible may be operative to contain molten silicon in which the top surface of the molten silicon may be defined as a growth interface. The crucible may be substantially surrounded by the anisotropic thermal load leveling component. The cold plate component may be positioned above the crucible to be operative with the anisotropic thermal load leveling component and heat source to maintain a uniform heat flux at the growth surface of the molten silicon.

  20. Friction and wear behavior of single-crystal silicon carbide in sliding contact with various metals

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1978-01-01

    Sliding friction experiments were conducted with single-crystal silicon carbide in contact with various metals. Results indicate the coefficient of friction is related to the relative chemical activity of the metals. The more active the metal, the higher the coefficient of friction. All the metals examined transferred to silicon carbide. The chemical activity of the metal and its shear modulus may play important roles in metal-transfer, the form of the wear debris and the surface roughness of the metal wear scar. The more active the metal, and the less resistance to shear, the greater the transfer to silicon carbide and the rougher the wear scar on the surface of the metal. Hexagon-shaped cracking and fracturing formed by cleavage of both prismatic and basal planes is observed on the silicon carbide surface.

  1. Friction and wear behavior of single-crystal silicon carbide in sliding contact with various metals

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1978-01-01

    Sliding friction experiments were conducted with single-crystal silicon carbide in contact with various metals. Results indicate the coefficient of friction is related to the relative chemical activity of the metals. The more active the metal, the higher the coefficient of friction. All the metals examined transferred to silicon carbide. The chemical activity of the metal and its shear modulus may play important roles in metal transfer, the form of the wear debris and the surface roughness of the metal wear scar. The more active the metal, and the less resistance to shear, the greater the transfer to silicon carbide and the rougher the wear scar on the surface of the metal. Hexagon shaped cracking and fracturing formed by cleavage of both prismatic and basal planes is observed on the silicon carbide surface.

  2. Vertical growth of cadmium sulfide crystals on a silicon substrate

    NASA Astrophysics Data System (ADS)

    Belyaev, A. P.; Rubets, V. P.; Antipov, V. V.

    2017-02-01

    The results of the technological and microscopy studies of the mechanisms of the vertical growth of cadmium sulfide crystals during vacuum synthesis from the vapor phase were reported. Whisker crystals with a diameter from 10 nm to a few micrometers and with a length of dozens of millimeters can be grown by the vacuum vapor phase synthesis in a quasi-closed volume. The results of studies are satisfactorily explained in terms of the classical vapor-liquid-crystal model. The SEM micrographs are presented.

  3. Homogeneity characterization of lattice spacing of silicon single crystals by a self-referenced lattice comparator

    NASA Astrophysics Data System (ADS)

    Fujimoto, H.; Waseda, A.; Zhang, X. W.

    2011-04-01

    The homogeneity of the lattice spacings of silicon single crystals from different origins was characterized. Strain measurements were performed on single crystals from NRLM3, NRLM4 and 28Si-10Pr11 ingots, which are all used to determine the Avogadro constant. NRLM3 and NRLM4 both exhibited clear striations, whereas almost no pattern was obtained for 28Si-10Pr11. The standard deviation of the lattice spacing of the single crystal obtained from 28Si-10Pr11 was 4.7 × 10-9, which enabled the lattice spacing to be determined with a standard uncertainty of 3 × 10-9.

  4. Friction, deformation and fracture of single-crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1977-01-01

    Friction experiments were conducted with hemispherical and conical diamond riders sliding on the basal plane of silicon carbide. The results indicate that, when deformation is primarily elastic, the friction does not depend on crystallographic orientation and there is no detectable fracture or cracking. When, however, plastic deformation occurs, silicon carbide exhibits anisotropic friction and deformation behavior. Surface fracture crack patterns surrounding wear tracks are observed to be of three types. The crack-geometries of two types are generally independent of orientation, the third crack, however, depends on the orientation. All surface cracks extend into subsurface. Anisotropic friction, deformation and fracture on the basal plane are primarily controlled by the slip system and cleavage.

  5. Single-Crystal Silicon: Electrical and Optical Properties

    NASA Astrophysics Data System (ADS)

    Hava, Shlomo; Auslender, Mark

    Electrical and optical properties of crystalline semiconductors are important parts of pure physics and material science research. In addition, knowledge of parameters related to these properties, primarily for silicon and III-V semiconductors, has received a high priority in microelectronics and optoelectronics since the establishment of these industries. For control protocols, emphasis has recently been placed on novel optical measurement techniques, which have proved very promising as nondestructive and even non-contact methods. Earlier they required knowledge of the free-carrier-derived optical constants, related to the electrical conductivity at infrared frequencies, but interest in the optical constants of silicon in the visible, ultraviolet (UV) and soft-X-ray ranges has been revived since the critical dimensions in devices have become smaller.

  6. Undoped semi-insulating LEC GaAs - A model and a mechanism. [Liquid Encapsulated Czochralski

    NASA Technical Reports Server (NTRS)

    Oliver, J. R.; Fairman, R. D.; Chen, R. T.; Yu, P. W.

    1981-01-01

    Undoped semi-insulating GaAs grown by the high-pressure liquid encapsulated Czochralski (LEC) method has been produced for use in direct ion implantation in several laboratories. A clear understanding of the factors controlling impurity transport and compensation in these materials has been lacking to date. In this work, detailed characterization has been performed on undoped semi-insulating crystals grown from both SiO2 and PBN crucibles followed by a proposed impurity model and compensation mechanism.

  7. Deactivation of metastable single-crystal silicon hyperdoped with sulfur

    SciTech Connect

    Simmons, C. B.; Akey, Austin J.; Sullivan, Joseph T.; Buonassisi, Tonio; Krich, Jacob J.; Recht, Daniel; Aziz, Michael J.

    2013-12-28

    Silicon supersaturated with sulfur by ion implantation and pulsed laser melting exhibits broadband optical absorption of photons with energies less than silicon's band gap. However, this metastable, hyperdoped material loses its ability to absorb sub-band gap light after subsequent thermal treatment. We explore this deactivation process through optical absorption and electronic transport measurements of sulfur-hyperdoped silicon subject to anneals at a range of durations and temperatures. The deactivation process is well described by the Johnson-Mehl-Avrami-Kolmogorov framework for the diffusion-mediated transformation of a metastable supersaturated solid solution, and we find that this transformation is characterized by an apparent activation energy of E{sub A}=1.7 ± 0.1 eV. Using this activation energy, the evolution of the optical and electronic properties for all anneal duration-temperature combinations collapse onto distinct curves as a function of the extent of reaction. We provide a mechanistic interpretation of this deactivation based on short-range thermally activated atomic movements of the dopants to form sulfur complexes.

  8. Comparison of ordered and disordered silicon nanowire arrays: experimental evidence of photonic crystal modes.

    PubMed

    Dhindsa, Navneet; Saini, Simarjeet S

    2016-05-01

    We experimentally compared the reflectance between ordered and disordered silicon nanowires to observe the evidence of photonic crystal modes. For similar diameters, the resonance peaks for the ordered nanowires at a spacing of 400 nm was at a shorter wavelength than the disordered nanowires, consistent to the excitation of photonic crystal modes. Furthermore, the resonant wavelength didn't shift while changing the density of the disordered nanowires, whereas there was a significant shift observed in the ordered ones. At an ordered spacing of 800 nm, the resonance wavelength approached that of the disordered structures, indicating that the ordered structures were starting to behave like individual waveguides. To our knowledge, this is the first direct experimental observation of photonic crystal modes in vertical periodic silicon nanowire arrays.

  9. Improving thin-film crystalline silicon solar cell efficiencies with photonic crystals.

    PubMed

    Bermel, Peter; Luo, Chiyan; Zeng, Lirong; Kimerling, Lionel C; Joannopoulos, John D

    2007-12-10

    Most photovoltaic (solar) cells are made from crystalline silicon (c-Si), which has an indirect band gap. This gives rise to weak absorption of one-third of usable solar photons. Therefore, improved light trapping schemes are needed, particularly for c-Si thin film solar cells. Here, a photonic crystal-based light-trapping approach is analyzed and compared to previous approaches. For a solar cell made of a 2 mum thin film of c-Si and a 6 bilayer distributed Bragg reflector (DBR) in the back, power generation can be enhanced by a relative amount of 24.0% by adding a 1D grating, 26.3% by replacing the DBR with a six-period triangular photonic crystal made of air holes in silicon, 31.3% by a DBR plus 2D grating, and 26.5% by replacing it with an eight-period inverse opal photonic crystal.

  10. Optical properties of one-dimensional photonic crystals obtained by micromatchining silicon (a review)

    NASA Astrophysics Data System (ADS)

    Tolmachev, V. A.

    2017-04-01

    The theoretical and experimental investigations of photonic band gaps in one-dimensional photonic crystals created by micromatchining silicon, which have been performed by the author as part of his doctoral dissertation, are presented. The most important result of the work is the development of a method of modeling photonic crystals based on photonic band gap maps plotted in structure-property coordinates, which can be used with any optical materials and in any region of electromagnetic radiation, and also for nonperiodic structures. This method made it possible to realize the targeted control of the optical contrast of photonic crystals and to predict the optical properties of optical heterostructures and three-component and composite photonic crystals. The theoretical findings were experimentally implemented using methods of micromatchining silicon, which can be incorporated into modern technological lines for the production of microchips. In the IR spectra of a designed and a fabricated optical heterostructure (a composite photonic crystal), extended bands with high reflectivities were obtained. In a Si-based three-component photonic crystal, broad transmission bands and photonic band gaps in the middle IR region have been predicted and experimentally demonstrated for the first time. Si-liquid crystal periodic structures with electric-field tunable photonic band-gap edges have been investigated. The one-dimensional photonic crystals developed based on micromatchining silicon can serve as a basis for creating components of optical processors, as well as highly sensitive chemical and biological sensors in a wide region of the IR spectrum (from 1 to 20 μm) for lab-on-a-chip applications.

  11. Comment on "Investigations of interstitial generations near growth interface depending on crystal pulling rates during CZ silicon growth by detaching from the melt" by T. Abe et al. [J. Cryst. Growth 434 (2016) 128-137] and on "Observations of secondary defects and vacancies in CZ silicon crystals detached from melt using four different types of characterization technique" by T. Abe et al. [J. Cryst. Growth 436 (2016) 23-33

    NASA Astrophysics Data System (ADS)

    Vanhellemont, Jan; Kamiyama, Eiji; Nakamura, Kozo; Sueoka, Koji

    2016-09-01

    In the papers mentioned above, Abe et al. published beautiful experimental data on intrinsic point defect related defect distributions in detached growing Czochralski Si crystals with and without additional thermal anneals [1,2]. The new fact compared to the results published before [3] is that the crystals are pulled with decreasing speed before detaching, resulting in crystals that vary along the axis from initially vacancy-rich to interstitial-rich for the slowest pulling speed before detaching.

  12. Nematic and blue phase liquid crystals for temperature stabilization and active optical tuning of silicon photonic devices (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ptasinski, Joanna N.; Khoo, Iam Choon; Fainman, Yeshaiahu

    2015-10-01

    We describe the underlying theories and experimental demonstrations of passive temperature stabilization of silicon photonic devices clad in nematic liquid crystal mixtures, and active optical tuning of silicon photonic resonant structures combined with dye-doped nematic and blue phase liquid crystals. We show how modifications to the resonator device geometry allow for not only enhanced tuning of the resonator response, but also aid in achieving complete athermal operations of silicon photonic circuits. [Ref.: I.C. Khoo, "DC-field-assisted grating formation and nonlinear diffractions in methyl-red dye-doped blue phase liquid crystals," Opt. Lett. 40, 60-63 (2015); J. Ptasinski, I.C. Khoo, and Y. Fainman, "Enhanced optical tuning of modified-geometry resonators clad in blue phase liquid crystals," Opt. Lett. 39, 5435-5438 (2014); J. Ptasinski, I.C. Khoo, and Y. Fainman, "Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals," Materials 7(3), 2229-2241 (2014)].

  13. Heat and mass transfer in semiconductor melts during single-crystal growth processes

    NASA Astrophysics Data System (ADS)

    Kakimoto, Koichi

    1995-03-01

    The quality of large semiconductor crystals grown from melts is significantly affected by the heat and mass transfer in the melts. The current understanding of the phenomena, especially melt convection, is reviewed starting from the results of visualization using model fluids or silicon melt, and continuing to the detailed numerical calculations needed for quantitative modeling of processing with solidification. The characteristics of silicon flows are also reviewed by focusing on the Coriolis force in the rotating melt. Descriptions of flow instabilities are included that show the level of understanding of melt convection with a low Prandtl number. Based on hydrodynamics, the origin of the silicon flow structure is reviewed, and it is discussed whether silicon flow is completely turbulent or has an ordered structure. The phase transition from axisymmetric to nonaxisymmetric flow is discussed using different geometries. Additionally, surface-tension-driven flow is reviewed for Czochralski crystal growth systems.

  14. Phase transformation during silica cluster impact on crystal silicon substrate studied by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Chen, Ruling; Luo, Jianbin; Guo, Dan; Lu, Xinchun

    2008-07-01

    The process of a silica cluster impact on a crystal silicon substrate is studied by molecular dynamics simulation. At the impact loading stage, crystal silicon of the impact zone transforms to a locally ordered molten with increasing the local temperature and pressure of the impact zone. And then the transient molten forms amorphous silicon directly as the local temperature and pressure decrease at the impact unloading stage. Moreover, the phase behavior between the locally ordered molten and amorphous silicon exhibits the reversible structural transition. The transient molten contains not only lots of four-fold atom but also many three- and five-fold atoms. And the five-fold atom is similar to the mixture structure of semi-Si-II and semi-bct5-Si. The structure transformation between five- and four-fold atoms is affected by both pressure and temperature. The structure transformation between three- and four-fold atoms is affected mostly by temperature. The direct structure transformation between five- and three-fold atoms is not observed. Finally, these five- and three-fold atoms are also different from the usual five- and three-fold deficient atoms of amorphous silicon. In addition, according to the change of coordination number of atoms the impact process is divided into six stages: elastic, plastic, hysteresis, phase regressive, adhesion and cooling stages.

  15. Crystallization of silicon films on glass: a comparison of methods. [Flat panel displays

    SciTech Connect

    Lemons, R.A.; Bosch, M.A.; Herbst, D.

    1982-01-01

    The lure of flat panel displays has stimulated much research on the crystallization of silicon films deposited on large-area transparent substrates. In most respects, fused quartz is ideal. It has high purity, thermal shock resistance, and a softening point above the silicon melting temperature. Unfortunately, fused quartz has such a small thermal expansion that the silicon film cracks as it cools. This problem has been attacked by patterning with islands or moats before and after crystallization, by capping, and by using silicate glass substrates that match the thermal expansion of silicon. The relative merits of these methods are compared. Melting of the silicon film to achieve high mobility has been accomplished by a variety of methods including lasers, electron beams, and strip heaters. For low melting temperature glasses, surface heating with a laser or electron beam is essential. Larger grains are obtained with the high bias temperature, strip heater techniques. The low-angle grain boundaries characteristic of these films may be caused by constitutional undercooling. A model is developed to predict the boundary spacing as a function of scan rate and temperature gradient. 11 figures.

  16. Silicon crystal morphologies during solidification refining from Al-Si melts

    NASA Astrophysics Data System (ADS)

    Ullah, Mohammad W.; Carlberg, Torbjörn

    2011-03-01

    To obtain a sound basis for further development of a refining process in which Si is precipitated from aluminium melts, a series of experiments have been performed in a Bridgman furnace. Compositions studied are in the range of 17-38% Si, and experiments have been carried out with the hot zone up and with the hot zone down to study the effects of flotation and sedimentation as well as those of different convection conditions on silicon precipitation. The similarity in density between liquid aluminium and silicon crystals implies that the melt convection is important for the possible separation of the crystals in a gravity field, but the crystal morphologies also have to be controlled to avoid aluminum inclusions. At lower silicon contents the silicon morphologies have a fish-bone or star-like shape but as the Si content increases the morphology changes to a plate-like structure, which becomes coarser with increasing Si concentration. The growth pattern for coarse plates growing as (1 1 1) platelets tend to form pockets of aluminium, which will end up as inclusions during dissolution of the matrix.

  17. Photoluminescence properties and crystallization of silicon quantum dots in hydrogenated amorphous Si-rich silicon carbide films

    SciTech Connect

    Wen, Guozhi; Zeng, Xiangbin Wen, Xixin; Liao, Wugang

    2014-04-28

    Silicon quantum dots (QDs) embedded in hydrogenated amorphous Si-rich silicon carbide (α-SiC:H) thin films were realized by plasma-enhanced chemical vapor deposition process and post-annealing. Fluorescence spectroscopy was used to characterize the room-temperature photoluminescence properties. X-ray photoelectron spectroscopy was used to analyze the element compositions and bonding configurations. Ultraviolet visible spectroscopy, Raman scattering, and high-resolution transmission electron microscopy were used to display the microstructural properties. Photoluminescence measurements reveal that there are six emission sub-bands, which behave in different ways. The peak wavelengths of sub-bands P1, P2, P3, and P6 are pinned at about 425.0, 437.3, 465.0, and 591.0 nm, respectively. Other two sub-bands, P4 is red-shifted from 494.6 to 512.4 nm and P5 from 570.2 to 587.8 nm with temperature increasing from 600 to 900 °C. But then are both blue-shifted, P4 to 500.2 nm and P5 to 573.8 nm from 900 to 1200 °C. The X-ray photoelectron spectroscopy analysis shows that the samples are in Si-rich nature, Si-O and Si-N bonds consumed some silicon atoms. The structure characterization displays that a separation between silicon phase and SiC phase happened; amorphous and crystalline silicon QDs synthesized with increasing the annealing temperature. P1, P2, P3, and P6 sub-bands are explained in terms of defect-related emission, while P4 and P5 sub-bands are explained in terms of quantum confinement effect. A correlation between the peak wavelength shift, as well as the integral intensity of the spectrum and crystallization of silicon QDs is supposed. These results help clarify the probable luminescence mechanisms and provide the possibility to optimize the optical properties of silicon QDs in Si-rich α-SiC: H materials.

  18. Liquid Crystal Spatial Light Modulator Using Amorphous Silicon Photoconductor

    NASA Astrophysics Data System (ADS)

    Song, Peng; Qihong, Wu; Jinfa, Tang

    1990-02-01

    The development of a reflection mode nematic field effect a ¬â€? Si:H LCLV is described. The amor-phous silicon photoconductor layer is deposited by glow discharge without doping. The configuration al-so consists of dielectric mirror as CdS LCLVs do. The bias frequency is in the range of 500Hz to 10KHz. MTF, sensitivity and time response of the device are measured. High resolution of > 501p/mm and switching time less than 25ms are achieved. Also reported is an equivalent circuit mode which has been compared with experimental results.

  19. Influence of intermediate layers on the surface condition of laser crystallized silicon thin films and solar cell performance

    NASA Astrophysics Data System (ADS)

    Höger, Ingmar; Himmerlich, Marcel; Gawlik, Annett; Brückner, Uwe; Krischok, Stefan; Andrä, Gudrun

    2016-01-01

    The intermediate layer (IL) between glass substrate and silicon plays a significant role in the optimization of multicrystalline liquid phase crystallized silicon thin film solar cells on glass. This study deals with the influence of the IL on the surface condition and the required chemical surface treatment of the crystallized silicon (mc-Si), which is of particular interest for a-Si:H heterojunction thin film solar cells. Two types of IL were investigated: sputtered silicon nitride (SiN) and a layer stack consisting of silicon nitride and silicon oxide (SiN/SiO). X-ray photoelectron spectroscopy measurements revealed the formation of silicon oxynitride (SiOxNy) or silicon oxide (SiO2) layers at the surface of the mc-Si after liquid phase crystallization on SiN or SiN/SiO, respectively. We propose that SiOxNy formation is governed by dissolving nitrogen from the SiN layer in the silicon melt, which segregates at the crystallization front during crystallization. This process is successfully hindered, when additional SiO layers are introduced into the IL. In order to achieve solar cell open circuit voltages above 500 mV, a removal of the formed SiOxNy top layer is required using sophisticated cleaning of the crystallized silicon prior to a-Si:H deposition. However, solar cells crystallized on SiN/SiO yield high open circuit voltage even when a simple wet chemical surface treatment is applied. The implementation of SiN/SiO intermediate layers facilitates the production of mesa type solar cells with open circuit voltages above 600 mV and a power conversion efficiency of 10%.

  20. Influence of intermediate layers on the surface condition of laser crystallized silicon thin films and solar cell performance

    SciTech Connect

    Höger, Ingmar Gawlik, Annett; Brückner, Uwe; Andrä, Gudrun; Himmerlich, Marcel; Krischok, Stefan

    2016-01-28

    The intermediate layer (IL) between glass substrate and silicon plays a significant role in the optimization of multicrystalline liquid phase crystallized silicon thin film solar cells on glass. This study deals with the influence of the IL on the surface condition and the required chemical surface treatment of the crystallized silicon (mc-Si), which is of particular interest for a-Si:H heterojunction thin film solar cells. Two types of IL were investigated: sputtered silicon nitride (SiN) and a layer stack consisting of silicon nitride and silicon oxide (SiN/SiO). X-ray photoelectron spectroscopy measurements revealed the formation of silicon oxynitride (SiO{sub x}N{sub y}) or silicon oxide (SiO{sub 2}) layers at the surface of the mc-Si after liquid phase crystallization on SiN or SiN/SiO, respectively. We propose that SiO{sub x}N{sub y} formation is governed by dissolving nitrogen from the SiN layer in the silicon melt, which segregates at the crystallization front during crystallization. This process is successfully hindered, when additional SiO layers are introduced into the IL. In order to achieve solar cell open circuit voltages above 500 mV, a removal of the formed SiO{sub x}N{sub y} top layer is required using sophisticated cleaning of the crystallized silicon prior to a-Si:H deposition. However, solar cells crystallized on SiN/SiO yield high open circuit voltage even when a simple wet chemical surface treatment is applied. The implementation of SiN/SiO intermediate layers facilitates the production of mesa type solar cells with open circuit voltages above 600 mV and a power conversion efficiency of 10%.

  1. One-dimensional photonic crystal slot waveguide for silicon-organic hybrid electro-optic modulators

    NASA Astrophysics Data System (ADS)

    Yan, Hai; Xu, Xiaochuan; Chung, Chi-Jui; Subbaraman, Harish; Pan, Zeyu; Chakravarty, Swapnajit; Chen, Ray T.

    2017-02-01

    A one-dimensional (1D) photonic crystal (PC) slot waveguide was proposed and experimentally demonstrated for integrated silicon-organic hybrid modulators. The 1D PC slot waveguide consists of a conventional silicon slot waveguide with periodic rectangular teeth on its two rails. This structure takes advantage of large mode overlap in a conventional slot waveguide and the slow light enhancement from the PC structure. Its simple geometry makes it resistant to fabrication imperfections and helps reduce the propagation loss. The observed effective EO coefficient in an actual Mach-Zehnder interferometer modulator is as high as 490 pm/V owing to slow light effect.

  2. Optical bistability with a repulsive optical force in coupled silicon photonic crystal membranes

    NASA Astrophysics Data System (ADS)

    Hui, Pui-Chuen; Woolf, David; Iwase, Eiji; Sohn, Young-Ik; Ramos, Daniel; Khan, Mughees; Rodriguez, Alejandro W.; Johnson, Steven G.; Capasso, Federico; Loncar, Marko

    2013-07-01

    We demonstrate actuation of a silicon photonic crystal membrane with a repulsive optical gradient force. The extent of the static actuation is extracted by examining the optical bistability as a combination of the optomechanical, thermo-optic, and photo-thermo-mechanical effects using coupled-mode theory. Device behavior is dominated by a repulsive optical force which results in displacements of ≈1 nm/mW. By employing an extended guided resonance which effectively eliminates multi-photon thermal and electronic nonlinearities, our silicon-based device provides a simple, non-intrusive solution to extending the actuation range of micro-electromechanical devices.

  3. Shear dependent nonlinear vibration in a high quality factor single crystal silicon micromechanical resonator

    NASA Astrophysics Data System (ADS)

    Zhu, H.; Shan, G. C.; Shek, C. H.; Lee, J. E.-Y.

    2012-07-01

    The frequency response of a single crystal silicon resonator under nonlinear vibration is investigated and related to the shear property of the material. The shear stress-strain relation of bulk silicon is studied using a first-principles approach. By incorporating the calculated shear property into a device-level model, our simulation closely predicts the frequency response of the device obtained by experiments and further captures the nonlinear features. These results indicate that the observed nonlinearity stems from the material's mechanical property. Given the high quality factor (Q) of the device reported here (˜2 × 106), this makes it highly susceptible to such mechanical nonlinear effects.

  4. 3D modeling of doping from the atmosphere in floating zone silicon crystal growth

    NASA Astrophysics Data System (ADS)

    Sabanskis, A.; Surovovs, K.; Virbulis, J.

    2017-01-01

    Three-dimensional numerical simulations of the inert gas flow, melt flow and dopant transport in both phases are carried out for silicon single crystal growth using the floating zone method. The mathematical model allows to predict the cooling heat flux density at silicon surfaces and realistically describes the dopant transport in case of doping from the atmosphere. A very good agreement with experiment is obtained for the radial resistivity variation profiles by taking into account the temperature dependence of chemical reaction processes at the free surface.

  5. Photonic crystal cavities in cubic (3C) polytype silicon carbide films.

    PubMed

    Radulaski, Marina; Babinec, Thomas M; Buckley, Sonia; Rundquist, Armand; Provine, J; Alassaad, Kassem; Ferro, Gabriel; Vučković, Jelena

    2013-12-30

    We present the design, fabrication, and characterization of high quality factor (Q ~10(3)) and small mode volume (V ~0.75 (λ/n)(3)) planar photonic crystal cavities from cubic (3C) thin films (thickness ~200 nm) of silicon carbide (SiC) grown epitaxially on a silicon substrate. We demonstrate cavity resonances across the telecommunications band, with wavelengths from 1.25 - 1.6 μm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science.

  6. Thermal-capillary model for Czochralski growth of semiconductor materials

    NASA Technical Reports Server (NTRS)

    Derby, J. J.; Brown, R. A.

    1985-01-01

    The success of efficiently calculating the temperature field, crystal radius, melt mensicus, and melt/solid interface in the Czochralski crystal growth system by full finite-element solution of the government thermal-capillary model is demonstrated. The model predicts realistic response to changes in pull rate, melt volume, and the thermal field. The experimentally observed phenomena of interface flipping, bumping, and the difficulty maintaining steady-state growth as the melt depth decreases are explained by model results. These calculations will form the basis for the first quantitative picture of Cz crystal growth. The accurate depiction of the melt meniscus is important in calculating the crystal radius and solidification interface. The sensitivity of the results to the equilibrium growth angle place doubt on less sophisticated attempts to model the process without inclusion of the meniscus. Quantitative comparison with experiments should be possible once more representation of the radiation and view factors in the thermal system and the crucible are included. Extensions of the model in these directions are underway.

  7. Production of extreme-purity aluminum and silicon by fractional crystallization processing

    NASA Astrophysics Data System (ADS)

    Dawless, R. K.; Troup, R. L.; Meier, D. L.; Rohatgi, A.

    1988-06-01

    Large scale fractional crystallization is used commercially at Alcoa to produce extreme purity aluminum (99.999+% Al). The primary market is sputtering targets used to make interconnects for integrated circuits. For some applications the impurities uranium and thorium are reduced to less than 1 ppbw to avoid "soft errors" associated with α particle emission. The crystallization process achieves segregation coefficients which are close to theoretical at normal yields, and this, coupled with the scale of the units, allows practical production of this material. The silicon purification process involves crystallization of Si from molten aluminum alloys containing about 30% silicon. The crystallites from this process are further treated to remove residual Al and an extreme purity ingot is obtained. This material is considered suitable for single crystal or ribbon type photovoltaic cells and for certain IC applications, including highly doped substrates used for epitaxial growth. In production of both extreme purity Al and Si, impurities are rejected to the remaining melt as the crystals form and some separation is achieved by draining this downgraded melt from the unit. Purification of this downgrade by crystallization has also been demonstrated for both systems and is important for achieving high recoveries.

  8. Modeling of the optical properties of porous silicon photonic crystals in the visible spectral range

    NASA Astrophysics Data System (ADS)

    Dovzhenko, D. S.; Martynov, I. L.; Kryukova, I. S.; Chistyakov, A. A.; Nabiev, I. R.

    2017-01-01

    Optical devices based on photonic crystals are of great interest because they can be efficiently used in laser physics and biosensing. Photonic crystals allow one to control the propagation of electromagnetic waves and to change the emission characteristics of luminophores embedded into photonic structures. One of the most interesting materials for developing one-dimensional photonic crystals is porous silicon. However, an important problem in application of this material is the control of the refractive index of layers by changing their porosity, as well as the refractive index dispersion. In addition, it is important to have the possibility of modeling the optical properties of structures to choose precisely select the fabrication parameters and produce one-dimensional photonic crystals with prescribed properties. In order to solve these problems, we used a mathematical model based on the transfer matrix method, using the Bruggeman model, and on the dispersion of silicon refractive index. We fabricated microcavities by electrochemical etching of silicon, with parameters determined by the proposed model, and measured their reflection spectra. The calculated results showed good agreement with experimental data. The model proposed allowed us to achieve a microcavity Q-factor of 160 in the visible region.

  9. CMOS compatible high-Q photonic crystal nanocavity fabricated with photolithography on silicon photonic platform.

    PubMed

    Ooka, Yuta; Tetsumoto, Tomohiro; Fushimi, Akihiro; Yoshiki, Wataru; Tanabe, Takasumi

    2015-06-18

    Progress on the fabrication of ultrahigh-Q photonic-crystal nanocavities (PhC-NCs) has revealed the prospect for new applications including silicon Raman lasers that require a strong confinement of light. Among various PhC-NCs, the highest Q has been recorded with silicon. On the other hand, microcavity is one of the basic building blocks in silicon photonics. However, the fusion between PhC-NCs and silicon photonics has yet to be exploited, since PhC-NCs are usually fabricated with electron-beam lithography and require an air-bridge structure. Here we show that a 2D-PhC-NC fabricated with deep-UV photolithography on a silica-clad silicon-on-insulator (SOI) structure will exhibit a high-Q of 2.2 × 10(5) with a mode-volume of ~ 1.7(λ/n)(3). This is the highest Q demonstrated with photolithography. We also show that this device exhibits an efficient thermal diffusion and enables high-speed switching. The demonstration of the photolithographic fabrication of high-Q silica-clad PhC-NCs will open possibility for mass-manufacturing and boost the fusion between silicon photonics and CMOS devices.

  10. CMOS compatible high-Q photonic crystal nanocavity fabricated with photolithography on silicon photonic platform

    PubMed Central

    Ooka, Yuta; Tetsumoto, Tomohiro; Fushimi, Akihiro; Yoshiki, Wataru; Tanabe, Takasumi

    2015-01-01

    Progress on the fabrication of ultrahigh-Q photonic-crystal nanocavities (PhC-NCs) has revealed the prospect for new applications including silicon Raman lasers that require a strong confinement of light. Among various PhC-NCs, the highest Q has been recorded with silicon. On the other hand, microcavity is one of the basic building blocks in silicon photonics. However, the fusion between PhC-NCs and silicon photonics has yet to be exploited, since PhC-NCs are usually fabricated with electron-beam lithography and require an air-bridge structure. Here we show that a 2D-PhC-NC fabricated with deep-UV photolithography on a silica-clad silicon-on-insulator (SOI) structure will exhibit a high-Q of 2.2 × 105 with a mode-volume of ~1.7(λ/n)3. This is the highest Q demonstrated with photolithography. We also show that this device exhibits an efficient thermal diffusion and enables high-speed switching. The demonstration of the photolithographic fabrication of high-Q silica-clad PhC-NCs will open possibility for mass-manufacturing and boost the fusion between silicon photonics and CMOS devices. PMID:26086849

  11. Digital silicon photomultiplier readout of a new fast and bright scintillation crystal (Ce:GFAG)

    NASA Astrophysics Data System (ADS)

    Lee, Yong-Seok; Leem, Hyun-Tae; Yamamoto, Seiichi; Choi, Yong; Kamada, Kei; Yoshikawa, Akira; Park, Sang-Geon; Yeom, Jung-Yeol

    2016-10-01

    A new Gadolinium Fine Aluminum Gallate (Ce:GFAG) scintillation crystal with both high energy resolution and fast timing properties has successfully been grown. Compared to Gd3Al2Ga3O12 (Ce:GAGG), this new inorganic scintillation crystal has a high luminosity similar to and a faster decay time. In this paper, we report on the timing and energy performance results of the new GFAG scintillation crystal read out with digital silicon photomultipliers (dSiPM) for positron emission tomography (PET) application. The best coincidence resolving time (FWHM) of polished 3×3×5 mm3 crystals was 223±6 ps for GFAG crystals compared to 396±28 ps for GAGG crystals and 131±3 ps for LYSO crystals respectively. An energy resolution (511 keV peak of Na-22) of 10.9±0.2% was attained with GFAG coupled to dSiPM after correcting for saturation effect, compared to 9.5±0.3% for Ce:GAGG crystals and 11.9±0.4% for LYSO crystals respectively. It is expected that this new scintillator may be competitive in terms of overall properties such as energy resolution, timing resolution and growing (raw material) cost, compared to existing scintillators for positron emission tomography (PET).

  12. Characterization of dislocation structures in silicon carbide single crystals

    NASA Astrophysics Data System (ADS)

    Vetter, William M.

    1999-07-01

    Two types of defects in PVT-grown 6H and 4H-SiC crystals were studied: screw dislocations that follow the axial direction of the crystal and dislocations that follow directions in the crystal's basal plane. The screw dislocations possessed a range of Burgers vector magnitudes, multiples of the axial parameter c, that could be determined by x-ray topographic image analysis. Hollow cores termed "micropipes" were observed when Burgers, vectors were larger than 3c. The micropipes were studied by a variety of methods: optical microscopy, laser scanning confocal microscopy, scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The micropipes were tubes 0.1 to 10mum in diameter. They were faceted, primarily along the {101¯0} planes, but also had {112¯0} facets. When encountering the growth surface of a crystal, they flared out into a trumpet-shape. Growth spirals sometimes occurred, originating from the trumpets' rims. The screw dislocations are visible in back-reflection synchrotron white beam x-ray topographs of basal-cut SiC wafers in striking contrast as black rings surrounding white circles, though such topographs are contaminated by a series of harmonic reflections, g = (0006n), where n = 3 to 16. By calculating and considering their intensities, and comparison with a g = 00018 Lang topograph taken with CuKalpha1 radiation, the g = 00024 harmonic was shown to be the most important contributor. Basal plane dislocations were seen in x-ray topographs of SiC looping from the points where screw dislocations occurred. Their extinction behavior showed they belonged to the set b = 13 <112¯0>. In some transmission electron micrographs, perfect dislocations with similar extinction behavior, along with partial dislocations with b = 13 <101¯0>, were seen originating from the micropipes' walls, curving out into the crystal a distance of 1 to 3mum, then back to terminate at the micropipe. Others led out of the field of view. Contrast is

  13. Fabrication of single-crystal silicon nanotubes with sub-10 nm walls using cryogenic inductively coupled plasma reactive ion etching.

    PubMed

    Li, Zhiqin; Chen, Yiqin; Zhu, Xupeng; Zheng, Mengjie; Dong, Fengliang; Chen, Peipei; Xu, Lihua; Chu, Weiguo; Duan, Huigao

    2016-09-09

    Single-crystal silicon nanostructures have attracted much attention in recent years due in part to their unique optical properties. In this work, we demonstrate direct fabrication of single-crystal silicon nanotubes with sub-10 nm walls which show low reflectivity. The fabrication was based on a cryogenic inductively coupled plasma reactive ion etching process using high-resolution hydrogen silsesquioxane nanostructures as the hard mask. Two main etching parameters including substrate low-frequency power and SF6/O2 flow rate ratio were investigated to determine the etching mechanism in the process. With optimized etching parameters, high-aspect-ratio silicon nanotubes with smooth and vertical sub-10 nm walls were fabricated. Compared to commonly-used antireflection silicon nanopillars with the same feature size, the densely packed silicon nanotubes possessed a lower reflectivity, implying possible potential applications of silicon nanotubes in photovoltaics.

  14. Silicon single-crystal cryogenic optical resonator: erratum

    NASA Astrophysics Data System (ADS)

    Wiens, Eugen; Chen, Qun-Feng; Ernsting, Ingo; Luckmann, Heiko; Rosowski, Ulrich; Nevsky, Alexander; Schiller, Stephan

    2015-01-01

    We report on the demonstration and characterization of a silicon optical resonator for laser frequency stabilization, operating in the deep cryogenic regime at temperatures as low as 1.5 K. Robust operation was achieved, with absolute frequency drift less than 20 Hz over 1 hour. This stability allowed sensitive measurements of the resonator thermal expansion coefficient ($\\alpha$). We found $\\alpha=4.6\\times10^{-13}$ ${\\rm K^{-1}}$ at 1.6 K. At 16.8 K $\\alpha$ vanishes, with a derivative equal to $-6\\times10^{-10}$ ${\\rm K}^{-2}$. The temperature of the resonator was stabilized to a level below 10 $\\mu$K for averaging times longer than 20 s. The sensitivity of the resonator frequency to a variation of the laser power was also studied. The corresponding sensitivities and the expected Brownian noise indicate that this system should enable frequency stabilization of lasers at the low-$10^{-17}$ level.

  15. Theory of High Frequency Rectification by Silicon Crystals

    DOE R&D Accomplishments Database

    Bethe, H. A.

    1942-10-29

    The excellent performance of British "red dot" crystals is explained as due to the knife edge contact against a polished surface. High frequency rectification depends critically on the capacity of the rectifying boundary layer of the crystal, C. For high conversion efficiency, the product of this capacity and of the "forward" (bulk) resistance R {sub b} of the crystal must be small. For a knife edge, this product depends primarily on the breadth of the knife edge and very little upon its length. The contact can therefore have a rather large area which prevents burn-out. For a wavelength of 10 cm. the computations show that the breadth of the knife edge should be less than about 10 {sup -3} cm. For a point contact the radius must be less than 1.5 x 10 {sup -3} cm. and the resulting small area is conducive to burn-out. The effect of "tapping" is probably to reduce the area of contact. (auth)

  16. Silicon photonic crystal cavity enhanced second-harmonic generation from monolayer WSe2

    NASA Astrophysics Data System (ADS)

    Fryett, Taylor K.; Seyler, Kyle L.; Zheng, Jiajiu; Liu, Chang-Hua; Xu, Xiaodong; Majumdar, Arka

    2017-03-01

    Nano-resonators integrated with two-dimensional materials (e.g. transition metal dichalcogenides) have recently emerged as a promising nano-optoelectronic platform. Here we demonstrate resonator-enhanced second-harmonic generation (SHG) in tungsten diselenide using a silicon photonic crystal cavity. By pumping the device with ultrafast laser pulses near the cavity mode at the telecommunication wavelength, we observe a near visible SHG with a narrow linewidth and near unity linear polarization, originated from the coupling of the pump photon to the cavity mode. The observed SHG is enhanced by factor of ∼200 compared to a bare monolayer on silicon. Our results imply the efficacy of cavity integrated monolayer materials for nonlinear optics and the potential of building a silicon-compatible second-order nonlinear integrated photonic platform.

  17. Performance of a PET detector module utilizing an array of silicon photodiodes to identify the crystal of interaction

    SciTech Connect

    Moses, W.W.; Derenzo, S.E. ); Nutt, R.; Digby, W.M.; Williams, C.W.; Andreaco, M. )

    1992-11-01

    We present initial performance results for a new multi-layer PET detector module consisting of an array of 3 mm square by 30 mm deep BGO crystals coupled on one end to a single photomultiplier tube and on the opposite end to an array of 3 mm square silicon photodiodes. The photomultiplier tube provides an accurate timing pulse and energy discrimination for the all the crystals in the module, while the silicon photodiodes identify the crystal of interaction. When a single BGO crystal at +25[degree]C is excited with 511 key photons, we measure a photodiode signal centered at 700 electrons (e[sup [minus

  18. Fabrication of triangular nanobeam waveguide networks in bulk diamond using single-crystal silicon hard masks

    SciTech Connect

    Bayn, I.; Mouradian, S.; Li, L.; Goldstein, J. A.; Schröder, T.; Zheng, J.; Chen, E. H.; Gaathon, O.; Englund, Dirk; Lu, M.; Stein, A.; Ruggiero, C. A.; Salzman, J.; Kalish, R.

    2014-11-24

    A scalable approach for integrated photonic networks in single-crystal diamond using triangular etching of bulk samples is presented. We describe designs of high quality factor (Q = 2.51 × 10{sup 6}) photonic crystal cavities with low mode volume (V{sub m} = 1.062 × (λ/n){sup 3}), which are connected via waveguides supported by suspension structures with predicted transmission loss of only 0.05 dB. We demonstrate the fabrication of these structures using transferred single-crystal silicon hard masks and angular dry etching, yielding photonic crystal cavities in the visible spectrum with measured quality factors in excess of Q = 3 × 10{sup 3}.

  19. Origin of a Nanoindentation Pop-in Event in Silicon Crystal

    NASA Astrophysics Data System (ADS)

    Abram, R.; Chrobak, D.; Nowak, R.

    2017-03-01

    The Letter concerns surface nanodeformation of Si crystal using atomistic simulation. Our results account for both the occurrence and absence of pop-in events during nanoindentation. We have identified two distinct processes responsible for indentation deformation based on load-depth response, stress-induced evolution of crystalline structure and surface profile. The first, resulting in a pop-in, consists of the extrusion of the crystalline high pressure Si -III /XII phase, while the second, without a pop-in, relies on a flow of amorphized Si to the crystal surface. Of particular interest to silicon technology will be our clarification of the interplay among amorphization, crystal-to-crystal transition, and extrusion of transformed material to the surface.

  20. Electro-optical modulator in a polymerinfiltrated silicon slotted photonic crystal waveguide heterostructure resonator.

    PubMed

    Wülbern, Jan Hendrik; Petrov, Alexander; Eich, Manfred

    2009-01-05

    We present a novel concept of a compact, ultra fast electro-optic modulator, based on photonic crystal resonator structures that can be realized in two dimensional photonic crystal slabs of silicon as core material employing a nonlinear optical polymer as infiltration and cladding material. The novel concept is to combine a photonic crystal heterostructure cavity with a slotted defect waveguide. The photonic crystal lattice can be used as a distributed electrode for the application of a modulation signal. An electrical contact is hence provided while the optical wave is kept isolated from the lossy metal electrodes. Thereby, well known disadvantages of segmented electrode designs such as excessive scattering are avoided. The optical field enhancement in the slotted region increases the nonlinear interaction with an external electric field resulting in an envisaged switching voltage of approximately 1 V at modulation speeds up to 100 GHz.

  1. Origin of a Nanoindentation Pop-in Event in Silicon Crystal.

    PubMed

    Abram, R; Chrobak, D; Nowak, R

    2017-03-03

    The Letter concerns surface nanodeformation of Si crystal using atomistic simulation. Our results account for both the occurrence and absence of pop-in events during nanoindentation. We have identified two distinct processes responsible for indentation deformation based on load-depth response, stress-induced evolution of crystalline structure and surface profile. The first, resulting in a pop-in, consists of the extrusion of the crystalline high pressure Si-III/XII phase, while the second, without a pop-in, relies on a flow of amorphized Si to the crystal surface. Of particular interest to silicon technology will be our clarification of the interplay among amorphization, crystal-to-crystal transition, and extrusion of transformed material to the surface.

  2. Demonstration of two-dimensional photonic crystals based on silicon carbide.

    PubMed

    Song, Bong-Shik; Yamada, Shota; Asano, Takashi; Noda, Susumu

    2011-06-06

    We demonstrate two-dimensional photonic crystals of silicon carbide (SiC)-a wide bandgap semiconductor and one of the hardest materials-at near-infrared wavelengths. Although the refractive index of SiC is lower than that of a conventional semiconductor such as GaAs or Si, we show theoretically that a wide photonic bandgap, a broadband waveguide, and a high-quality nanocavity comparable to those of previous photonic crystals can be obtained in SiC photonic crystals. We also develop a process for fabricating SiC-based photonic crystals that experimentally show a photonic bandgap of 200 nm, a waveguide with a 40-nm bandwidth, and a nanocavity with a high quality factor of 4,500. This demonstration should stimulate further development of resilient and stable photonics at high power and high temperature analogous to SiC power electronics.

  3. Mechanisms limiting the performance of large grain polycrystalline silicon solar cells

    NASA Technical Reports Server (NTRS)

    Culik, J. S.; Alexander, P.; Dumas, K. A.; Wohlgemuth, J. W.

    1984-01-01

    The open-circuit voltage and short-circuit current of large-grain (1 to 10 mm grain diameter) polycrystalline silicon solar cells is determined by the minority-carrier diffusion length within the bulk of the grains. This was demonstrated by irradiating polycrystalline and single-crystal (Czochralski) silicon solar cells with 1 MeV electrons to reduce their bulk lifetime. The variation of short-circuit current with minority-carrier diffusion length for the polycrystalline solar cells is identical to that of the single-crystal solar cells. The open-circuit voltage versus short-circuit current characteristic of the polycrystalline solar cells for reduced diffusion lengths is also identical to that of the single-crystal solar cells. The open-circuit voltage of the polycrystalline solar cells is a strong function of quasi-neutral (bulk) recombination, and is reduced only slightly, if at all, by grain-boundary recombination.

  4. Fracture characteristics of Czochralski-grown Y{sub 3}Al{sub 5}O{sub 12}

    SciTech Connect

    Reimanis, I.E.; Hawley, M.E.; Mitchell, T.E.; Zhou, D.S.

    1995-08-01

    The fracture surfaces of single-crystal Y{sub 3}al{sub 5}O{sub 12} (YAG) have been examined in detail using differential interference microscopy and atomic force microscopy. In YAG crystals grown in 1977 by the Czochralski method strikingly regular undulations of microscopic and submicroscopic dimensions (4--20 nm in amplitude, 1--20 {micro}m in wavelength) are observed on every fracture surface. The undulations do not exhibit typical characteristics of Wallner lines; furthermore, they are not observed in identical fracture tests for YAG crystals grown in 1990 by the Czochralski method. Transmission electron microscopy reveals that the crystals grown in 1977 exhibit a periodic fluctuation of the ratio of the concentrations of aluminum to yttrium, suggesting that the fracture surface features are caused by periodic astoichiometry.

  5. Elemental characterization of the Avogadro silicon crystal WASO 04 by neutron activation analysis

    NASA Astrophysics Data System (ADS)

    D'Agostino, G.; Bergamaschi, L.; Giordani, L.; Mana, G.; Massa, E.; Oddone, M.

    2012-12-01

    Impurity measurements of the 28Si crystal used for the determination of the Avogadro constant are essential to prevent biased results or underestimated uncertainties. A review of the existing data confirmed the high purity of silicon with respect to a large number of elements. In order to obtain direct evidence of purity, we developed a relative analytical method based on neutron activation. As a preliminary test, this method was applied to a sample of the Avogadro natural silicon crystal WASO 04. The investigation concerned 29 elements. The mass fraction of Au was quantified to be (1.03 ± 0.18) × 10-12. For the remaining 28 elements, the mass fractions were below the detection limits, which ranged between 1 × 10-12 and 1 × 10-5.

  6. Experimental setup for investigating silicon solid phase crystallization at high temperatures.

    PubMed

    Schmidt, Thomas; Gawlik, Annett; Schneidewind, Henrik; Ihring, Andreas; Andrä, Gudrun; Falk, Fritz

    2013-07-15

    An experimental setup is presented to measure and interpret the solid phase crystallization of amorphous silicon thin films on glass at very high temperatures of about 800 °C. Molybdenum-SiO(2)-silicon film stacks were irradiated by a diode laser with a well-shaped top hat profile. From the relevant thermal and optical parameters of the system the temperature evolution can be calculated accurately. A time evolution of the laser power was applied which leads to a temperature constant in time in the center of the sample. Such a process will allow the observation and interpretation of solid phase crystallization in terms of nucleation and growth in further work.

  7. Selective tuning of high-Q silicon photonic crystal nanocavities via laser-assisted local oxidation.

    PubMed

    Chen, Charlton J; Zheng, Jiangjun; Gu, Tingyi; McMillan, James F; Yu, Mingbin; Lo, Guo-Qiang; Kwong, Dim-Lee; Wong, Chee Wei

    2011-06-20

    We examine the cavity resonance tuning of high-Q silicon photonic crystal heterostructures by localized laser-assisted thermal oxidation using a 532 nm continuous wave laser focused to a 2.5 μm radius spot-size. The total shift is consistent with the parabolic rate law. A tuning range of up to 8.7 nm is achieved with ∼ 30 mW laser powers. Over this tuning range, the cavity Qs decreases from 3.2×10(5) to 1.2×10(5). Numerical simulations model the temperature distributions in the silicon photonic crystal membrane and the cavity resonance shift from oxidation.

  8. On-chip optical diode based on silicon photonic crystal heterojunctions.

    PubMed

    Wang, Chen; Zhou, Chang-Zhu; Li, Zhi-Yuan

    2011-12-19

    Optical isolation is a long pursued object with fundamental difficulty in integrated photonics. As a step towards this goal, we demonstrate the design, fabrication, and characterization of on-chip wavelength-scale optical diodes that are made from the heterojunction between two different silicon two-dimensional square-lattice photonic crystal slabs with directional bandgap mismatch and different mode transitions. The measured transmission spectra show considerable unidirectional transmission behavior, in good agreement with numerical simulations. The experimental realization of on-chip optical diodes with wavelength-scale size using all-dielectric, passive, and linear silicon photonic crystal structures may help to construct on-chip optical logical devices without nonlinearity or magnetism, and would open up a road towards photonic computers.

  9. High speed liquid crystal over silicon display based on the flexoelectro-optic effect.

    PubMed

    Chen, Jing; Morris, Stephen M; Wilkinson, Timothy D; Freeman, Jon P; Coles, Harry J

    2009-04-27

    One of the key technologies to evolve in the displays market in recent years is liquid crystal over silicon (LCOS) microdisplays. Traditional LCOS devices and applications such as rear projection televisions, have been based on intensity modulation electro-optical effects, however, recent developments have shown that multi-level phase modulation from these devices is extremely sought after for applications such as holographic projectors, optical correlators and adaptive optics. Here, we propose alternative device geometry based on the flexoelectric-optic effect in a chiral nematic liquid crystal. This device is capable of delivering a multilevel phase shift at response times less than 100 microsec which has been verified by phase shift interferometry using an LCOS test device. The flexoelectric on silicon device, due to its remarkable characteristics, enables the next generation of holographic devices to be realized.

  10. Effect of antireflection coating on the crystallization of amorphous silicon films by flash lamp annealing

    NASA Astrophysics Data System (ADS)

    Sonoda, Yuki; Ohdaira, Keisuke

    2017-04-01

    We succeed in decreasing the fluence of a flash-lamp pulse required for the crystallization of electron-beam (EB)-evaporated amorphous silicon (a-Si) films using silicon nitride (SiN x ) antireflection films. The antireflection effect of SiN x is confirmed not only when SiN x is placed on the surface of a-Si or flash lamp annealing (FLA) is performed from the film side, but also when SiN x is inserted between glass and a-Si and a flash pulse is supplied from the glass side. We also quantitatively confirm, by calculating flash-lamp pulse energies actually reaching a-Si films using reflectance spectra, that the reduction in the fluence of a flash-lamp pulse for the crystallization of a-Si films is due to the antireflection effect of SiN x .

  11. Structural Elements of Shallow Thermal Donors Formed in Nitrogen-Gas-Doped Silicon Crystals

    NASA Astrophysics Data System (ADS)

    Hara, Akito

    2007-02-01

    It has been reported that shallow thermal donors (STDs) are formed in oxygen-rich silicon (Si) crystals preannealed in nitrogen gas (N-gas-doped) and also in hydrogen-doped (H-doped) oxygen-rich Si crystals. The STDs formed in these crystals exhibit very similar electronic structures. Experiments using far-infrared optical absorption showed that several hydrogen-like STDs were formed at the same time and their energy levels in both the above-mentioned crystals were very similar. It has also been reported that the g-values of the STDs formed in both the crystals were identical. On the basis of electron-nucleus double resonance results, it has been strongly suggested that a hydrogen impurity is incorporated as a structural element of the STDs formed in the H-doped Si crystals. However, the origin of the STDs that are formed in N-gas-doped Si crystals is still unclear. To clarify this point, hydrogen detection in N-gas-doped Si was conducted and the annealing behaviors of STDs in N-gas-doped Si and H-doped Si were compared by electron spin resonance and far-infrared optical absorption measurement. It was concluded that the origin of the STDs formed in N-gas-doped Si crystals is not related to the hydrogen impurity.

  12. Doping of germanium and silicon crystals with non-hydrogenic acceptors for far infrared lasers

    DOEpatents

    Haller, Eugene E.; Brundermann, Erik

    2000-01-01

    A method for doping semiconductors used for far infrared lasers with non-hydrogenic acceptors having binding energies larger than the energy of the laser photons. Doping of germanium or silicon crystals with beryllium, zinc or copper. A far infrared laser comprising germanium crystals doped with double or triple acceptor dopants permitting the doped laser to be tuned continuously from 1 to 4 terahertz and to operate in continuous mode. A method for operating semiconductor hole population inversion lasers with a closed cycle refrigerator.

  13. Enhanced bandgap in annular photonic-crystal silicon-on-insulator asymmetric slabs.

    PubMed

    Hou, Jin; Citrin, D S; Wu, Huaming; Gao, Dingshan; Zhou, Zhiping

    2011-06-15

    Photonic band structures of annular photonic-crystal (APC) silicon-on-insulator (SOI) asymmetric slabs with finite thickness were investigated by the three-dimensional plane-wave expansion method. The results show that for a broad range of air-volume filling factors, APC slabs can exhibit a significantly larger bandgap than conventional circular-hole photonic-crystal (PC) slabs. Bandgap enhancements over conventional air hole PC SOI slabs as large as twofold are predicted for low air-volume filling factors below 15%. This desirable behavior suggests a potential for APC SOI slabs to serve as the basis of various optical cavities, waveguides, and mirrors.

  14. Coupling of silicon-vacancy centers to a single crystal diamond cavity.

    PubMed

    Lee, Jonathan C; Aharonovich, Igor; Magyar, Andrew P; Rol, Fabian; Hu, Evelyn L

    2012-04-09

    Optical coupling of an ensemble of silicon-vacancy (SiV) centers to single-crystal diamond microdisk cavities is demonstrated. The cavities are fabricated from a single-crystal diamond membrane generated by ion implantation and electrochemical liftoff followed by homo-epitaxial overgrowth. Whispering gallery modes spectrally overlap with the zero-phonon line (ZPL) of the SiV centers and exhibit quality factors ∼ 2200. Lifetime reduction from 1.8 ns to 1.48 ns is observed from SiV centers in the cavity compared to those in the membrane outside the cavity. These results are pivotal in developing diamond integrated photonics networks.

  15. Commensurate germanium light emitters in silicon-on-insulator photonic crystal slabs.

    PubMed

    Jannesari, R; Schatzl, M; Hackl, F; Glaser, M; Hingerl, K; Fromherz, T; Schäffler, F

    2014-10-20

    We report on the fabrication and characterization of silicon-on-insulator (SOI) photonic crystal slabs (PCS) with commensurately embedded germanium quantum dot (QD) emitters for near-infrared light emission. Substrate pre-patterning defines preferential nucleation sites for the self-assembly of Ge QDs during epitaxial growth. Aligned two-dimensional photonic crystal slabs are then etched into the SOI layer. QD ordering enhances the photoluminescence output as compared to PCSs with randomly embedded QDs. Rigorously coupled wave analysis shows that coupling of the QD emitters to leaky modes of the PCS can be tuned via their location within the unit cell of the PCS.

  16. Absorbing one-dimensional planar photonic crystal for amorphous silicon solar cell.

    PubMed

    El Daif, Ounsi; Drouard, Emmanuel; Gomard, Guillaume; Kaminski, Anne; Fave, Alain; Lemiti, Mustapha; Ahn, Sungmo; Kim, Sihan; Roca I Cabarrocas, Pere; Jeon, Heonsu; Seassal, Christian

    2010-09-13

    We report on the absorption of a 100nm thick hydrogenated amorphous silicon layer patterned as a planar photonic crystal (PPC), using laser holography and reactive ion etching. Compared to an unpatterned layer, electromagnetic simulation and optical measurements both show a 50% increase of the absorption over the 0.38-0.75micron spectral range, in the case of a one-dimensional PPC. Such absorbing photonic crystals, combined with transparent and conductive layers, may be at the basis of new photovoltaic solar cells.

  17. Experimental considerations of higher order parametric x rays from silicon crystals of varying thicknesses

    NASA Astrophysics Data System (ADS)

    Evertson, Scott R.

    1992-06-01

    Generation of parametric x-radiation (PXR) may be described as the Bragg scattering of virtual photons to produce real x-rays which satisfy the Bragg condition n lambda = 2d sin(theta sub B) where theta sub B is the angle between the electron beam and the crystal plane. Enhanced higher order parametric s-radiation from the (220) and the (111) planes of silicon crystals of varying thicknesses were observed. Production of PXR of order n=1 for both planes of a 20 micron thick crystal and orders n=1, and n=2 of the (220) and the n=1, n=3, and n=4 of the (111) planes of the 44 microns and 320 microns crystals were observed. Exploiting the formation and attenuation lengths of silicon crystals of varying thicknesses, higher order x-ray production is enhanced relative to the lower energy first order x ray. Photons of 4.5 to 21 keV have been observed.

  18. Optimal light trapping in ultra-thin photonic crystal crystalline silicon solar cells.

    PubMed

    Mallick, Shrestha Basu; Agrawal, Mukul; Peumans, Peter

    2010-03-15

    Crystalline silicon is an attractive photovoltaic material because of its natural abundance, accumulated materials and process knowledge, and its appropriate band gap. To reduce cost, thin films of crystalline silicon can be used. This reduces the amount of material needed and allows material with shorter carrier diffusion lengths to be used. However, the indirect band gap of silicon requires that a light trapping approach be used to maximize optical absorption. Here, a photonic crystal (PC) based approach is used to maximize solar light harvesting in a 400 nm-thick silicon layer by tuning the coupling strength of incident radiation to quasiguided modes over a broad spectral range. The structure consists of a double layer PC with the upper layer having holes which have a smaller radius compared to the holes in the lower layer. We show that the spectrally averaged fraction of photons absorbed is increased 8-fold compared to a planar cell with equivalent volume of active material. This results in an enhancement of maximum achievable photocurrent density from 7.1 mA/cm(2) for an unstructured film to 21.8 mA/cm(2) for a film structured as the double layer photonic crystal. This photocurrent density value approaches the limit of 26.5 mA/cm(2), obtained using the Yablonovitch light trapping limit for the same volume of active material.

  19. The effect of dopants on the brittle-to-ductile transition in silicon single crystals

    NASA Astrophysics Data System (ADS)

    Hong, Youn Jeong; Tanaka, Masaki; Maeno, Keiki; Higashida, Kenji

    2010-07-01

    The brittle-to-ductile transition (BDT) in boron, antimony and arsenic doped Cz silicon crystals has been experimentally studied, respectively. The BDT temperatures in antimony and arsenic doped silicon wafers are lower than that in a non-doped wafer while the BDT temperature in a boron doped wafer is almost the same as that in the non-doped wafer. The activation energy was obtained from the strain rate dependence of the BDT temperature. It was found that the values of the activation energy in the antimony and arsenic doped wafers are lower than that in the non-doped and boron doped wafers, indicating that the dislocation velocity in the antimony and arsenic doped silicon is faster than that in the non-doped while the dislocation velocity in the boron doped is the same as that in the non-doped. The effect of increasing in dislocation velocity on the BDT temperature was calculated by two-dimensional discrete dislocation dynamics simulations, indicating that the increasing in dislocation velocity decreases the BDT temperature in silicon single crystals.

  20. Study the performance of LYSO and CeBr3 crystals using Silicon Photomultipliers

    NASA Astrophysics Data System (ADS)

    Kryemadhi, Abaz

    2016-03-01

    The Silicon Photomultipliers (SiPMs) are novel photon-detectors which have been progressively found their use in particle physics. Their small size, good single photon resolution, simple readout, and immunity to magnetic fields offers advantages compared to traditional photomultipliers. LYSO and CeBr3 crystals are relatively new scintillators with high light yield and fast decay time. The response of these detectors to low energy gamma rays and cosmic ray muons will be presented. Messiah College Workload Reallocation Program.

  1. Crystallization of the glassy phase of grain boundaries in silicon nitride

    NASA Technical Reports Server (NTRS)

    Jefferson, D. A.; Thomas, J. M.; Wen, S.

    1984-01-01

    Three types of hot-pressed silicon nitride specimens (containing 5wt% Y2O3 and 2wt% Al2O3 additives) which were subjected to different temperature heat treatments were studied by X-ray diffraction, X-ray microanalysis and high resolution electron microscopy. The results indicated that there were phase changes in the grain boundaries after heat treatment and the glassy phase at the grain boundaries was crystallized by heat treatment.

  2. Nanostructuring of single-crystal silicon carbide by picosecond UV laser radiation

    SciTech Connect

    Barmina, E V; Serkov, A A; Shafeev, G A

    2013-12-31

    Surface nanostructures are produced on single-crystal 4H-SiC by laser ablation in water using a Nd : YAG laser (355-nm wavelength, 10-ps pulse duration) as a radiation source. The morphology of the nanostructured surface and the nanostructure size distribution are examined in relation to the energy density of the incident laser beam. The potential of the described process for improving the luminosity of light-emitting diodes on silicon carbide substrates is discussed. (letters)

  3. Observation of four-wave mixing in slow-light silicon photonic crystal waveguides.

    PubMed

    McMillan, James F; Yu, Mingbin; Kwong, Dim-Lee; Wong, Chee Wei

    2010-07-19

    Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB increase in the conversion efficiency is observed. Concurrently, a decrease in the conversion bandwidth is observed due to the increase in group velocity dispersion in the slow-light regime. The experimentally observed conversion efficiencies agree with the numerically modeled results.

  4. Electron-irradiation-induced crystallization at metallic amorphous/silicon oxide interfaces caused by electronic excitation

    SciTech Connect

    Nagase, Takeshi; Yamashita, Ryo; Lee, Jung-Goo

    2016-04-28

    Irradiation-induced crystallization of an amorphous phase was stimulated at a Pd-Si amorphous/silicon oxide (a(Pd-Si)/SiO{sub x}) interface at 298 K by electron irradiation at acceleration voltages ranging between 25 kV and 200 kV. Under irradiation, a Pd-Si amorphous phase was initially formed at the crystalline face-centered cubic palladium/silicon oxide (Pd/SiO{sub x}) interface, followed by the formation of a Pd{sub 2}Si intermetallic compound through irradiation-induced crystallization. The irradiation-induced crystallization can be considered to be stimulated not by defect introduction through the electron knock-on effects and electron-beam heating, but by the electronic excitation mechanism. The observed irradiation-induced structural change at the a(Pd-Si)/SiO{sub x} and Pd/SiO{sub x} interfaces indicates multiple structural modifications at the metal/silicon oxide interfaces through electronic excitation induced by the electron-beam processes.

  5. Dislocation formation in seed crystals induced by feedstock indentation during growth of quasimono crystalline silicon ingots

    NASA Astrophysics Data System (ADS)

    Trempa, M.; Beier, M.; Reimann, C.; Roßhirth, K.; Friedrich, J.; Löbel, C.; Sylla, L.; Richter, T.

    2016-11-01

    In this work the dislocation formation in the seed crystal induced by feedstock indentation during the growth of quasimono (QM) silicon ingots for photovoltaic application was investigated. It could be shown by special laboratory indentation experiments that the formed dislocations propagate up to several millimeters deep into the volume of the seed crystal in dependence on the applied pressure of the feedstock particles on the surface of the seed crystal. Further, it was demonstrated that these dislocations if they were not back-melted during the seeding process grow further into the silicon ingot and drastically reduce its material quality. An estimation of the apparent pressure values in a G5 industrial crucible/feedstock setup reveals that the indentation phenomenon is a critical issue for the industrial production of QM silicon ingots. Therefore, some approaches to avoid/reduce the indentation events were tested with the result, that the most promising solution should be the usage of suitable feedstock particles as coverage of the seed.

  6. Single-crystal silicon MEMS microactuator for high-density hard disk drive

    NASA Astrophysics Data System (ADS)

    Mou, Jianqiang; Chen, Shixin; Lu, Yi

    2001-11-01

    A single crystal silicon MEMS microactuator for high density hard disk drives is described in this paper. The microactuator is located between a slider and a suspension, and drives the slider on which a magnetic head is attached. The MEMS actuator is fabricated by improved LISA process. It has an electrically isolated 20:1 (40micrometers thick, 2micrometers width) high aspect ratio structure directly processed from a single crystal silicon substrate. The overall dimension of the micro-actuator is 1.4mm by 1.4mm and by a thickness of 0.15mm. Experiments show that +/- 0.6 micrometers displacement stroke of the Read/Write magnetic head, which is attached on the MEMS actuator, can be achieved when input voltage is 40V. The dynamic performances of the MEMS actuator integrated with a Head Gimbal Assembly (HGA) are analyzed by FEM Simulation. The simulation results demonstrated that the controllable in-plane resonance frequency of the MEMS actuator is 1.5 kHz, and the first uncontrollable out-of- plane resonance frequency of the MEMS actuator integrated with the HGA is 16.6kHz. The single crystal silicon microactuator has good shock reliability, and eliminates large material creep and thermal mismatch problems.

  7. Improved quality control of silicon wafers using novel off-line air pocket image analysis

    NASA Astrophysics Data System (ADS)

    Valley, John F.; Sanna, M. Cristina

    2014-08-01

    Air pockets (APK) occur randomly in Czochralski (Cz) grown silicon (Si) crystals and may become included in wafers after slicing and polishing. Previously the only APK of interest were those that intersected the front surface of the wafer and therefore directly impacted device yield. However mobile and other electronics have placed new demands on wafers to be internally APK-free for reasons of thermal management and packaging yield. We present a novel, recently patented, APK image processing technique and demonstrate the use of that technique, off-line, to improve quality control during wafer manufacturing.

  8. Liquid crystal colloidal structures for increased silicone deposition efficiency on colour-treated hair.

    PubMed

    Brown, M A; Hutchins, T A; Gamsky, C J; Wagner, M S; Page, S H; Marsh, J M

    2010-06-01

    An approach is described to increase the deposition efficiency of silicone conditioning actives from a shampoo on colour-treated hair via liquid crystal (LC) colloidal structures, created with a high charge density cationic polymer, poly(diallyldimethyl ammonium chloride) and negatively charged surfactants. LCs are materials existing structurally between the solid crystalline and liquid phases, and several techniques, including polarized light microscopy, small angle X-Ray analysis, and differential scanning calorimetry, were used to confirm the presence of the LC structures in the shampoo formula. Silicone deposition from the LC-containing shampoo and a control shampoo was measured on a range of hair substrates, and data from inductively coupled plasma optical emission spectroscopy analysis and ToF-SIMS imaging illustrate the enhancement in silicone deposition for the LC shampoo on all hair types tested, with the most pronounced enhancement occurring on hair that had undergone oxidative treatments, such as colouring. A model is proposed in which the LC structure deposits from the shampoo onto the hair to: (i) provide 'slip planes' along the hair surface for wet conditioning purposes and (ii) form a hydrophobic layer which changes the surface energy of the fibres. This increase in hydrophobicity of the hair surface thereby increases the deposition efficiency of silicone conditioning ingredients. Zeta potential measurements, dynamic absorbency testing analysis and ToF-SIMS imaging were used to better understand the mechanisms of action. This approach to increasing silicone deposition is an improvement relative to conventional conditioning shampoos, especially for colour-treated hair.

  9. Solar-Grade Silicon from Metallurgical-Grade Silicon Via Iodine Chemical Vapor Transport Purification: Preprint

    SciTech Connect

    Ciszek, T. F.; Wang, T. H.; Page, M. R.; Bauer, R. E.; Landry, M. D.

    2002-05-01

    This conference paper describes the atmospheric-pressure in an ''open'' reactor, SiI2 transfers from a hot (>1100C) Si source to a cooler (>750C) Si substrate and decomposes easily via 2SiI2 Si+ SiI4 with up to 5?m/min deposition rate. SiI4 returns to cyclically transport more Si. When the source is metallurgical-grade Si, impurities can be effectively removed by three mechanisms: (1) differing free energies of formation in forming silicon and impurity iodides; (2) distillation; and (3) differing standard free energies of formation during deposition. Distillation has been previously reported. Here, we focused on mechanisms (1) and (3). We made feedstock, analyzed the impurity levels, grew Czochralski single crystals, and evaluated crystal and photovoltaic properties. Cell efficiencies of 9.5% were obtained. Incorporating distillation (step 2) should increase this to a viable level.

  10. Advances in large-diameter liquid encapsulated Czochralski GaAs

    NASA Technical Reports Server (NTRS)

    Chen, R. T.; Holmes, D. E.; Kirkpatrick, C. G.

    1982-01-01

    The purity, crystalline perfection, and electrical properties of n- and p-type GaAs crystals grown by the liquid encapsulated Czochralski (LEC) technique are evaluated. The determination of the dislocation density, incidence of twinning, microstructure, background purity, mobility, and minority carrier diffusion length is included. The properties of the LEC GaAs crystals are generally comparable to, if not superior to those of small-diameter GaAs material grown by conventional bulk growth techniques. As a result, LEC GaAs is suitable for application to minority carrier devices requiring high-quality and large-area substrates.

  11. N-type compensated silicon: resistivity, crystal growth, carrier lifetime, and relevant application for HIT solar cells

    NASA Astrophysics Data System (ADS)

    Li, Shuai; Gao, Wenxiu; Li, Zhen; Cheng, Haoran; Lin, Jinxia; Cheng, Qijin

    2017-05-01

    N-type compensated silicon shows unusual distribution of resistivity as crystal grows compared to the n-type uncompensated silicon. In this paper, evolutions of resistivities with varied concentrations of boron and varied starting resistivities of the n-type silicon are intensively calculated. Moreover, reduction of carrier mobility is taken into account by Schindler’s modified model of carrier mobility for the calculation of resistivity of the compensated silicon. As for substrates of solar cells, optimized starting resistivity and corresponding concentration of boron are suggested for better uniformity of resistivity and higher yield (fraction with ρ >0.5 ~ Ω \\centerdot \\text{cm} ) of the n-type compensated Cz crystal rod. A two-step growth method is investigated to obtain better uniformity of resistivity of crystal rod, and this method is very practical especially for the n-type compensated silicon. Regarding the carrier lifetime, the recombination by shallow energy-level dopants is taken into account for the compensated silicon, and evolution of carrier lifetime is simulated by considering all main recombination centers which agrees well with our measured carrier lifetimes as crystal grows. The n-type compensated silicon shows a larger reduction of carrier lifetime compared to the uncompensated silicon at the beginning of crystal growth, and recombination with a oxygen-related deep defect is sufficient to describe the reduction of degraded lifetime. Finally, standard heterojunction with intrinsic thin-layer (HIT) solar cells are made with substrates from the n-type compensated silicon rod, and a high efficiency of 22.1% is obtained with a high concentration (0.8× {{10}16}~\\text{c}{{\\text{m}}-3} ) of boron in the n-type compensated silicon feedstock. However, experimental efficiencies of HIT solar cells based on the n-type compensated silicon show an average reduction of 4% along with the crystal length compared to the uncompensated silicon. The

  12. Photoconductivity in inverse silicon opals enhanced by slow photon effect: Yet another step towards optically amplified silicon photonic crystal solar cells

    NASA Astrophysics Data System (ADS)

    Suezaki, Takashi; Yano, Hiroshi; Hatayama, Tomoaki; Ozin, Geoffrey A.; Fuyuki, Takashi

    2011-02-01

    While silicon photonic crystals have promised revolutionary advances in the field of optical telecommunications and optical computing, it has only recently been realized that their prowess to trap and slow photons could potentially improve the efficiency of silicon solar cells. In this work, spectral responses for the electrical properties of inverse silicon opals are evaluated and show a correlation with photonic bandgaps. In particular, a sign of the enhanced photoelectric generation by the slow photon effect is observed at the edges of photonic bandgaps.

  13. Titanium distribution profiles obtained by luminescence and LIBS measurements on Ti: Al2O3 grown by Czochralski and Kyropoulos techniques

    NASA Astrophysics Data System (ADS)

    Alombert-Goget, Guillaume; Trichard, Florian; Li, Hui; Pezzani, Cyril; Silvestre, Maud; Barthalay, Nicolas; Motto-Ros, Vincent; Lebbou, Kheirreddine

    2017-03-01

    The titanium distributions in Ti-doped sapphires grown by Czochralski and Kyropoulos techniques were evaluated using Laser-Induced Breakdown Spectroscopy (LIBS) and luminescence characterizations. Distinctly different radial profiles of Ti4+ distribution were observed in the as grown Ti: Al2O3 crystals. The Ti4+ distribution in the crystal grown by Kyropoulos technique was analyzed as a function of the specific of the growth technique, the conclusion is significant for Ti: sapphire on laser application. Kyropoulos technique presents an advantage to reduce the proportion of Ti4+ in Ti: sapphire comparing to Czochralski technique.

  14. Reflectivity calculated for a three-dimensional silicon photonic band gap crystal with finite support

    NASA Astrophysics Data System (ADS)

    Devashish, D.; Hasan, Shakeeb B.; van der Vegt, J. J. W.; Vos, Willem L.

    2017-04-01

    We study numerically the reflectivity of three-dimensional (3D) photonic crystals with a complete 3D photonic band gap. We employ the finite element method to study crystals with the cubic diamondlike inverse woodpile structure. The high-index backbone has a dielectric function similar to silicon. We study crystals with a range of thicknesses up to ten unit cells (L ≤10 c ). The crystals are surrounded by vacuum, and have a finite support as in experiments. The polarization-resolved reflectivity spectra reveal Fabry-Pérot fringes related to standing waves in the finite crystal, as well as broad stop bands with nearly 100 % reflectivity, even for thin crystals. The frequency ranges of the stop bands change little with angle of incidence, which is plausible since the stop bands are part of the 3D band gap. Moreover, this result supports the previous assertion that intense reflection peaks measured with a large numerical aperture provide a faithful signature of the 3D photonic band gap. For p -polarized waves, we observe an intriguing hybridization between the Fabry-Pérot resonances and the Brewster angle that remains to be observed in experiments. From the strong reflectivity peaks, it is inferred that the maximum reflectivity observed in experiments is not limited by finite size. The frequency ranges of the stop bands agree very well with stop gaps in the photonic band structure that pertain to infinite and perfect crystals. The angle-dependent reflectivity spectra provide an improved interpretation of the reflectivity measurements performed with a certain numerical aperture and a new insight in the crystal structure, namely unequal pore radii in X and Z directions. The Bragg attenuation lengths LB are found to be smaller by a factor 6 to 9 than earlier estimates that are based on the width of the stop band. Hence, crystals with a thickness of 12 unit cells studied in experiments are in the thick crystal limit (L ≫LB ). Our reflectivity calculations suggest

  15. Carrier mobility reduction and model in n-type compensated silicon

    NASA Astrophysics Data System (ADS)

    Li, Shuai; Gao, Wenxiu; Zheng, Songsheng; Cheng, Haoran; Yang, Xing; Cheng, Qijin; Chen, Chao

    2017-10-01

    Research on electrical properties of the compensated silicon is very crucial for understanding the doping layer and compensated substrates of solar cells. Regarding the fact that there are still inadequate experimental data of carrier mobility on the n-type compensated silicon, hence in this paper, both majority electron and minority hole mobilities measured on the n-type compensated solar-grade silicon substrates are presented. Prediction models of carrier mobility are essential for material characterization and device (e.g. solar cells) simulation. However, as prediction models of carrier mobility are commonly established based on the uncompensated silicon, large deviations of carrier mobility have been observed on the compensated silicon. In this work, the standard Klaassen's model and optimized model for the compensated silicon by Schindler et al. are reviewed and compared to measured carrier mobilities. Moreover, the factors that lead to deviations of Klaassen's model on the n-type compensated silicon are critically discussed, and then we propose an optimized model for prediction of carrier mobility in the compensated silicon. This model can also be extended to both majority and minority carrier mobilities in p- and n-type compensated silicon and fits well with previous published data as well as carrier mobility data presented here. In addition, evolutions of majority electron and minority hole mobilities as crystal grows are also simulated for n-type compensated Czochralski silicon which agrees well with our measured results.

  16. Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon

    SciTech Connect

    Zeng, Y.; Roland, I.; Checoury, X.; Han, Z.; El Kurdi, M.; Sauvage, S.; Boucaud, P.; Gayral, B.; Brimont, C.; Guillet, T.; Mexis, M.; Semond, F.

    2015-02-23

    We demonstrate second harmonic generation in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated by the second-order nonlinear susceptibilities χ{sub zxx}{sup (2)}, χ{sub zyy}{sup (2)} and the electric fields of the fundamental cavity mode.

  17. Microscopic three-dimensional topometry with ferroelectric liquid-crystal-on-silicon displays.

    PubMed

    Proll, Klaus-Peter; Nivet, Jean-Marc; Körner, Klaus; Tiziani, Hans J

    2003-04-01

    When three dimensional measurements are conducted with fringe projection, the quality of the grating used for the generation of the fringes is important. It has a direct influence on the achievable depth resolution in a given measurement setup. In the past, Ronchi grating or gratings written in nematic liquid-crystal displays or in digital micromirror devices have been used. We report on the application of a reflective ferroelectric liquid-crystal-on-silicon display as the fringe-generating element in a setup based on a stereo microscope. With this device the depth resolution of measurements by use of phase-shifting algorithms can be significantly improved compared with the application of a Ronchi grating or a nematic liquid-crystal display.

  18. Crystallization of hydrogenated amorphous silicon films by exposure to femtosecond pulsed laser radiation

    SciTech Connect

    Volodin, V. A.; Kachko, A. S.

    2011-02-15

    To crystallize hydrogenated amorphous silicon films on glass substrates, pulsed Ti-sapphire laser radiation is used, with a pulse duration less than 30 fs. The initial films are grown by plasma-enhanced chemical-vapor deposition at the temperatures 200 and 250 Degree-Sign C. The structural properties of the initial films and films treated with laser radiation pulses are studied by Raman spectroscopy. The conditions for complete crystallization of the films grown on glass substrates to thicknesses of up to 100 nm and hydrogen content of up to 20 at % are established. The conditions provide the fabrication of highly homogeneous films by scanning laser treatments. It is found that, if the hydrogen content in the film is 30-40 at %, the crystallization is an inhomogeneous process and laser ablation is observed in some areas of the films.

  19. Molecular dynamics simulations of crystal growth from melted silicon: Defect formation processes

    SciTech Connect

    Ishimaru, Manabu; Motooka, Teruaki

    1999-07-01

    Molecular dynamics calculations have been performed to simulate crystal growth from melted silicon (Si) and defect formation processes based on the ordinary Langevin equation employing the Tersoff interatomic potential. The findings of this investigation are as follows: (1) The [110] bonds at the solid-liquid interface induce the eclipsed configurations or hexagonal Si structures which stabilize microfacets composed of the {l{underscore}brace}111{r{underscore}brace} planes. (2) Defect formation during crystal growth processes is due to misorientations at the {l{underscore}brace}111{r{underscore}brace} interfaces which result in an elementary grown-in defect structure including five- and seven-member rings. (3) The elementary grown-in defect migrates in c-Si by bond-switching motions during further crystal pulling or annealing.

  20. A New Cell-Selective Three-Dimensional Microincubator Based on Silicon Photonic Crystals

    PubMed Central

    Carpignano, Francesca; Silva, Gloria; Surdo, Salvatore; Leva, Valentina; Montecucco, Alessandra; Aredia, Francesca; Scovassi, Anna Ivana; Merlo, Sabina; Barillaro, Giuseppe; Mazzini, Giuliano

    2012-01-01

    In this work, we show that vertical, high aspect-ratio (HAR) photonic crystals (PhCs), consisting of periodic arrays of 5 µm wide gaps with depth of 50 µm separated by 3 µm thick silicon walls, fabricated by electrochemical micromachining, can be used as three-dimensional microincubators, allowing cell lines to be selectively grown into the gaps. Silicon micromachined dice incorporating regions with different surface profiles, namely flat silicon and deeply etched PhC, were used as microincubators for culturing adherent cell lines with different morphology and adhesion properties. We extensively investigated and compared the proliferative behavior on HAR PhCs of eight human cell models, with different origins, such as the epithelial (SW613-B3; HeLa; SW480; HCT116; HT29) and the mesenchymal (MRC-5V1; CF; HT1080). We also verified the contribution of cell sedimentation into the silicon gaps. Fluorescence microscopy analysis highlights that only cell lines that exhibit, in the tested culture condition, the behavior typical of the mesenchymal phenotype are able to penetrate into the gaps of the PhC, extending their body deeply in the narrow gaps between adjacent silicon walls, and to grow adherent to the vertical surfaces of silicon. Results reported in this work, confirmed in various experiments, strongly support our statement that such three-dimensional microstructures have selection capabilities with regard to the cell lines that can actively populate the narrow gaps. Cells with a mesenchymal phenotype could be exploited in the next future as bioreceptors, in combination with HAR PhC optical transducers, e.g., for label-free optical detection of cellular activities involving changes in cell adhesion and/or morphology (e.g., apoptosis) in a three-dimensional microenvironment. PMID:23139792