A Veeco resistance heated Czochralski crystal growing furnace was redesigned to allow for the in-situ casting of semicrystalline silicon ingots. The casting technique that is being employed in this program is based upon the Bridgeman technique of crystal growth. Samples of metallurgical grade silicon have been obtained from Ohio-Ferro Alloys corporation and preparation of this material has begun for incorporation into the experimental castings. Initial casting experiments have commenced using pure semiconductor grade silicon to establish a base line process for later experiments which will employ metallurgical grade silicon.

Design modifications were made to incorporate thermocouples into the polysilicon casting furnace to allow for the constant monitoring of the temperature profile during the casting process. A source of metallurgical grade (MG) silicon was chosen and the material was prepared by grinding the large pieces into powder. The uniformity of the feedstock was ascertained by optical emission spectrograph analysis of three random samples of the feedstock. A total of sixteen casting runs were made this quarter; Union Carbide CMG graphite was found to be the most suitable crucible material. Solar cells were fabricated from the successful castings (five 100% SG, and two containing 1% and 5% MG silicon, respectively). The average efficiency from the first SG ingot was 10.4% AM0 (in excess of 12% AM1). In general, solar cells fabricated from the top and bottom of the ingots exhibited better overall characteristics. The addition of MG silicon to the casting caused a large degradation in both light and dark I-V characteristics. The dark current tended to be dominated almost entirely by the space-charge component in these castings. A new method was developed which eliminates temperature scanning in DLTS measurements by incorporating a spectrum analyzer into the system; results are in good agreement with published data. Efforts were directed toward decreasing the spot size of the scanning photoresponse system from 60 .mu.m to 5 .mu.m. Successful scans were made on a single crystal cell having a large shunt resistance. Electron channelling patterns were obtained for all crystallographic directions in polysilicon material and were assembled into a composite (001)-(111) standard triangle; measurement results are presented. Preliminary x-ray topographs were obtained for grains 1 and 2 in solar cell 1-1 using the asymmetrical crystal topography technique; results are discussed.