The influence of sequence of precursor films on CZTSe thin films prepared by ion-beam sputtering deposition

The CuZnSn（CZT） precursor thin films are grown by ion-beam sputtering Cu, Zn, Sn targets with different orders and then sputtering Se target to fabricate Cu_2ZnSnSe_4（CZTSe） absorber thin films on molybdenum substrates. They are annealed in the same vacuum chamber at 400 ℃. The characterization methods of CZTSe thin films include X-ray diffraction（XRD）, energy dispersive spectroscopy（EDS）, scanning electron microscopy（SEM）, and X-ray photoelectron spectra（XPS） in order to study the crystallographic properties, composition, surface morphology, electrical properties and so on. The results display that the CZTSe thin films got the strongest diffraction peak intensity and were with good crystalline quality and its morphology appeared smooth and compact with a sequence of Cu/Zn/Sn/Se, which reveals that the expected states for CZTSe are Cu~（1＋）, Zn~（2＋）, Sn~（4＋）, Se~（2）.With the good crystalline quality and close to ideal stoichiometric ratio the resistivity of the CZTSe film with the sequence of Cu/Zn/Sn/Se is lower, whose optical band gap is about 1.50 eV.