Effect of Substrate Temperature on the Structural and Optical Properties of Nanocrystalline Cadmium Selenide Thin Films Prepared by Electron Beam Evaporation Technique

Cadmium selenide (CdSe) thin films on glass substrates were prepared by physical vapour deposition under vacuum using the electron beam evaporated technique for different substrate temperatures: room temperature, 100; 200, 300 degrees C, respectively. X-ray diffraction analysis indicates that the films are polycrystalline, having hexagonal (wurtzite) structure irrespective of their substrate temperature. All the films show most preferred orientation along (0 0 2) plane parallel to the substrates. The microstructural parameters such as particle size, stress, strain and dislocation density were calculated. The grain size of deposited CdSe films is small and is within the range of 18 to 42 nm. The optical absorption spectra of electrom beam deposited CdSe films were studied in the wavelength region of 250-2500 nm. The energy gap (E(g)) values (allowed direct transitions), calculated from the absorption spectra, ranged between 1.77 and 1.92 eV. The surface morphological quality of electron beam evaporated CdSe films were analyzed by scanning electron microscopy and atomic force microscopy.