However, by using a two step masked oxide evaporation, as shown in Fig. 3(a) and (b), this task can be accomplished. In the first step, a solid mask consisting of fine parallel wires is employed to deposit strips of oxide on the backside of the silicon. This step is shown in Fig. 3(a). Next a similar mask with wires perpendicular to the already deposited oxide strips is used to apply another group of oxide strips. This will result in an array of silicon contacts as shown in Fig. 3(b). Prior to this oxide deposition step polycrystalline silicon is deposited on the frontside to provide texture. Concurrently with either of the backside oxide deposition steps a frontside oxide deposition is employed to reduce radiation damage. After the contact holes are fabricated a solid mask is used to ion implant first the p-type contacts and then the n-type contacts as shown in Fig. 3(c). This implant is followed by an anneal to eliminate the ion damage. After this doping step a solid mask can be utilized to deposit the metal film. This metallization step is shown in Fig. 3(d). Wire bonding and mounting follow the metal deposition. All these steps can be accomplished with the restraints imposed by this study. Conclusions The fabrication of a variety of different types of silicon solar cells in space with lunar material, no imported gases or chemicals, in zero-gravity and utilizing existing technologies was shown to be feasible. Processing steps such as crystal growth, zone refining, molecular beam epitaxy, ion implantation, alloying, evaporation of metals and oxides and wire bonding were shown to be space compatible. Due to the requirement of annealing radiation damage it was proposed that titanium or possibly iron or a silicide of either, be used as the primary cell conductor. It may be possible to fabricate highly efficient point-contact solar cells in space with the constraints imposed in this study. REFERENCES [1] Glaser, P.E. (1968) Power from the Sun: its future, Science, 162, 857. [2] O'Leary, B. (1977) Mining the Apollo and Amor Asteroids, Science, 197, 363. [3] O'Neill, G.K. (1978) The low (profile) road to space manufacturing, Astronaut. Aeronaut. 16, 24. [4] Koelle, H.H. (1982) Preliminary analysis of a baseline system model for lunar manufacturing, Acta Astronautica, 9, 401. [5] Sparks, D.R. (1986) Recovery of asteroidal metals for terrestrial utilization, Acta Astronautica, 13, 101. [6] DuBose, P. et al. (1986) Solar power satellite built of lunar materials, Space Power, 6, 1. [7] Swanson, R.M. (1986) IEEE Spectrum, 23, 24. [8] Hutchenson, G.D. (1985) Semiconductor demand and wafer consumption, Semiconductor Inti., 8, 43. [9] Piland, R.O. (1978) The solar power satellite concept evaluation programme, in: Billman, K.W. (ed.) Radiation Energy Conservation in Space, AIAA, 61, pp. 3. [10] Glaser, P.E. (1977) The potential of satellite solar power, Proc. IEEE, 65, 1162. [11] Sparks, D.R. (1987) The large-scale manufacturing of electronic and electrical components in space, Acta Astronautica, 15, 239. [12] Adler, L, Trombka, J., Gerard, J., Blodget, H., Eller, E., Yin, L. Lamother,
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