Annealing and surface treatment effect on the optical and electrical properties of n-type CdS binary compound semiconductors

The preparation of CdS thin films were actualised with electrodeposition technique using cathodic voltage of 1200 milli – Volts (mV). The optical and electrical properties of three different classes of CdS semiconductors namely as – deposited CdS layers (AD-CdS), CdS layers heat-treated in air without any chemical treatment (HT-CdS) and CdS layers treated with CdCl2 and annealed in air (CC-CdS) have been investigated in this work. Results from optical analysis showed that AD-CdS layers have the least absorption edge and highest energy bandgap. Annealing the CdS thin films without and with CdCl2 treatment brings the energy bandgap to same value of ~2.42 eV. The main distinction between the HT- and CC-CdS layers is that the absorption edge of CC-CdS films is sharper than the HT-CdS. Results from electrical analysis revealed that the magnitude of photo-electro-chemical (PEC) cell signals which give a clue about the doping concentration of the semiconductor material is greater in CC-CdS layers than in AD- and HT-CdS layers.Keywords: AD-CdS, HT-CdS, CC-CdS, Energy Bandgap, Absorption Edge, PEC Cell Signal.