Structural and Optical Properties of CuInS2Thin Films Fabricated by Electron-beam Evaporation

Abstract

Single phase CuInS<TEX>$_2$</TEX> thin film with the strongest diffraction peak (112) at diffraction angle (2<TEX>$\theta$</TEX>) of 27.7<TEX>$^{\circ}$</TEX> and the second strongest diffraction peak (220) at diffraction angle (2<TEX>$\theta$</TEX>) of 46.25<TEX>$^{\circ}$</TEX>was well made with chalcopyrite structure at substrate temperature of 70<TEX>$^{\circ}C$</TEX>. annealing temperature of 250<TEX>$^{\circ}C$</TEX>, annealing time of 60 min. The CuInS<TEX>$_2$</TEX> thin film had the greatest grain size of 1.2 Um when the Cu/In composition ratio of 1.03, where the lattice constant of a and c were 5.60<TEX>${\AA}$</TEX> and 11.12<TEX>${\AA}$</TEX>, respectively. The Cu/In stoichiometry of the single-phase CuInS<TEX>$_2$</TEX>thin films was from 0.84 to 1.3. The film was p-type when tile Cu/In ratio was above 0.99 and was n-type when the Cu/In was below 0.95. The fundamental absorption wavelength, absorption coefficient and optical band gap of p-type CuInS<TEX>$_2$</TEX> thin film with Cu/In=1.3 were 837nm, 3.OH 104 cm-1 and 1.48 eV, respectively. The fundamental absorption wavelength absorption coefficient and optical energy band gap of n-type CuInS<TEX>$_2$</TEX> thin film with Cu/In=0.84 were 821 nm, 6.0<TEX>${\times}$</TEX>10<TEX>$^4$</TEX>cm<TEX>$\^$</TEX>-1/ and 1.51 eV, respectively.