Chemical bath deposition of CdS highly-textured, columnar films

Chemical bath deposition (CBD) is one of the most common techniques for depositing CdS films. While there have been many studies on these films, and considerable characterization of their morphologies, most of this characterization has been by either X-ray diffraction or plan-view electron microscopy. With the exception of epitaxial films deposited on single crystal substrates, there has been little characterization of the cross-sectional structure of CBD CdS films. We show how, using a CdSO₄ bath and ethylenediamine as complexant, dense, columnar films of predominantly cubic CdS can be very reproducibly obtained. The initial growth is disordered, but preferential growth perpendicular to the polar face results in highly textured growth. A similar, if somewhat less ordered, morphology is obtained from a commonly-used ammonia bath using CdCl₂ as the source of Cd. Although not explicitly recognized, chloride baths in the literature exhibited sharp X-ray diffraction peaks and this is now connected with the growth mode these baths have in common with ethylenediamine baths.