CdTe films grown using a rotating sublimate vapor effusion source in glancing angle deposition mode

Abstract

Thin films of CdTe were deposited on glass substrates using a rotating sublimate vapor effusion source combined with glancing angle deposition substrate mode. The samples were prepared with different incident deposition flux angles of α=0°, 40°, 50° and 60° using substrate rotation of 55rpm in the opposite direction to the source which was in turn rotated at 40rpm. The Scanning electron and atomic force microscopy images showed that the sample with α=0° and without substrate rotation presented dense columnar structures with variable shapes and dimensions. However, the sample with substrate rotation presented dense coalesced columnar structures with uniform shapes. When the substrate is simultaneously tilted and rotated the columnar forms is more individuality defined. The X-ray diffraction measurements demonstrated that all samples crystallized in the CdTe-cubic phase structure, which exhibits a diffraction peak with full width at half-maximum of the (111) Bragg reflection of 390.4arcsec corresponding to a crystallite size of ∼75nm for the sample with α=50°. The crystallite size decreased as α increased. The apparent absorption edge shifting towards lower wavelength regions for samples grown at α=50° and 60° was attributed to light scattering by the columnar structures. The optical band gap for all samples presented an average value of ∼1.5eV.