THE EFFECT OF DEPOSITION TIME ON COPPER OXIDE THIN FILMS D

Abstract

This paper reports the preparation of Copper Oxide thin films by Chemical Bath Deposition method .The copper oxide thin films were synthesis on glass slide substrates by chemical bath deposition by varying the deposition time using 0.4M of copper acetate, ammonia solution, and hydrazine hydrate. The thin film were deposited by varying deposition time at 15’, 25’, and 35’ at 50oC having the total volume of 70ml. The deposited thin film were red in color, thick, well adhere and uniform. The samples are annealed at 300o c for 1.5hrs. The thin films were characterized by XRD and UV-VIS spectroscopy to investigate the structural and optical phase properties. The structural property was scanned by SHIMADZU XRD-7000 X-ray difractometer 2θ ranging from 10-80o . The XRD result shows all films prepared with deposition time 15’ and 25’ are highly crystalline in cubic Cu2O structure while at the deposition time of 35’additional dominant cubic Cu structure is observed. And the preferred orientation of the film at 15’ and 25’ has 36.38 o along the (111) and at 35’ along the (111) plane of metallic copper. The optical characteristics were identified in the wave length ranging from 400-800nm and the band gap decreased with increasing the deposition time from 2.45-1.75eV. The film deposited at 25' has a band gap of the 1.85 eV. Which similar to the band gap of Cu2O reported by [69]. Although XRD result shows a dominant metallic copper phase at deposition time 35’, UV-Vis result shows the presence of band gap which is in contradiction of XRD result. Therefore further investigation is required. The result shows the decrement of band gap with increasing deposition time. However the band gap and crystalline size doesn’t show correlation. This could be due to varies factor like deposition method, dopant, defects, diffusion and super saturation. That is as the film thickens diffusion of reactant become slower and the solution become supersaturated with copper ion hindering further nucleation; these factors eventually limit crystal growth. And also Ostwald ripening occurs when larger crystal grows at the expense of smaller ones. Then smaller grain dissolves and their material migrate to larger grains. This process reduces the overall crystal size. Generally initially, increasing reaction time leads to larger crystal; beyond a critical point, Ostwald ripening also dominates, causing a decrease in crystal size. The balance between the