efforts this quarter concentrated on completion and check-out of the mbe system, deposition of zns films, analysis of the internal photoresponse for cu-cu sub 2 o cells, and fabrication and characterization of cu-cu sub 2 o solar cells. in-doped zns films with very good optical quality and finite conductivity were obtained by co-depositing in and zns. analysis of the internal photoresponse indicated that minority carrier diffusion lengths on the order of 10 mu m are being achieved with the present cu sub 2 o growth procedure active area values of j/sub ph/ = 8.52 ma/cm exp 2 and am1 efficiency = 1.76 were achieved for cu-cu sub 2 o cells. these devices appear to have an mis structure, or fixed charge at the interface. in particular, analysis of i-v data indicates that the current-voltage characteristics for applied voltages greater than 0.3 v are characterized by n approx. = 1 and j sub 0 approx. = 2 x 10 exp -9 ma/cm exp 2 , which implies an effective barrier height of 0.94 ev compared to the theoretical value of 0.7 ev for a cu/cu sub 2 o schottky barrier. another very significant achievement this past quarter was the development of a surface preparation procedure which results in a nearly perfect stochiometry at the surface. (era citation 05:027069)