Use of Laser Beam Diffraction for Non-invasive Characterisation of CdTe Thin Film Growth Structure

Characterisation of Cadmium Telluride (CdTe) thin films commonly requires the use of invasive techniques for the identification of their structural growth and the detection of defects which occur during the deposition process. Structural growth and the presence of defects can affect the performance of the final device. A non-invasive inspection system for CdTe films has been developed to identify the structural properties of this material, comparing two different deposition techniques, Close Space Sublimation (CSS) and Magnetron Sputtering (MS). The proposed system utilises a 1 μm diode laser which passes through the CdTe layer, originating detectable diffraction patterns, which are characterised using image processing techniques and assessed using a neural network-based cognitive decision-making support system. Results are found to be consistent with the conventional microscopic techniques (SEM and TEM) used to analyse morphological and structural properties of thin-film CdTe solar cells.