Structure And Morphology Of Obliquely Deposited Cdte Films

Secondary Author(s)

Pinheiro, Roberto; Parikh, Nalin


Structure and morphology of CdTe films deposited in vacuum, on glass substrates, at oblique vapor incidence angles and at substrate temperatures up to 250°C, have been studied by reflection-electron diffraction and scanning-electron microscopy, so as to help in the understanding of their unusually high photo-electromotive force. Thinner films developed sphalerite type of face centred cubic (c) structure with a0 = 6.48 '. Thicker films showed additional wurtzite type of hexagonal close packed (h) phase with a0 = 4.57 ', c0 = 7.47 ', and a large hexagonal (H) phase, a0 = 4.57 ', c0 = 11,27 ', with a corresponding reduction in the proportion of the c phase. For oblique vapor incidence, 1 ' d {111} orientation of c phase and 1' d {00.1} orientation of h phase, both being close packed layers showed normal or only slightly oblique growth, while 1 ' d {331} orientation of c phase and 1 ' d {10.3} orientations of hexagonal phases showed oblique growth towards the vapor direction but not aligned with it. Hillock growth of deposits was observed, with the hillocks forming rows normal to or at an angle to the vapor direction. The leeward side of the hillocks is controlled by the vapor direction. This side called by us, the growth direction is tilted towards but is not aligned with the vapor direction. It has been indicated that, as against the model based on the mismatch between adjacent hillocks, for explaining the high photo-emf, that based on the transition between cubic and hexagonal structures is in better conformity with the results.

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