Structural, Optical, and Electrical Properties of CdTe Thin Films Deposited by Glancing Angle Deposition

In this paper, glancing angle deposition technique (GLAD) has been used to grow cadmium telluride (CdTe) thin film by vacuum thermal method on glass substrates. During deposition, the substrate temperature was maintained at 20 degrees C. Due to shadowing effect, the oblique angle deposition technique can produce nanorods tilted toward the incident deposition flux. The evaporated atoms arrive at the growing interface at a fixed angle theta, measured from the normal to the substrate surface. An XRD picture, for nonfixed substrate an amorphous film has been seen at small angles (0 degrees, 15 degrees, 30 degrees, 40 degrees) has been obtained. Films deposited at large angles (50 degrees, 60 degrees, 65 degrees, 70 degrees, 80 degrees, 85 degrees) was found to be poly-crystalline in nature along the peak intensity direction. The surface morphology has shown an improvement without the presence of secondary phases for higher incident angles (theta>60 degrees). It has been observed that the use of this growth technique leads to an improvement in the optical properties of the films. The transmittance T and reflectance R spectra of CdTe films, deposited at different incident angles without substrate rotation have been obtained. High absorption coefficients (2x10(4) - 8x10(4) cm(-1)) in the visible range and near-IR spectral range have been observed. Cell efficiency of 7.04 %, and fill factor of 70.6% have been obtained for CdTe thin films of thickness 450 mu m by GLAD technique, deposited at fixed substrate and incident angle 65 degrees.