Photoemission Study of the Electronic Structure of Layered Oxysulfide ((Lao)Cus)
J. O. Akinlami and A. M Awobode
The electronic structure of LaOCuS has been investigated by means of photoemission spectroscopy. It was found that the theoretical photoemission (PES) spectrum at ћω = 21.2 eV shows four distinct structures with peaks at -9.2 eV, -12.2 eV, -16.7 eV and -19.7 eV but on increasing the photon energy to 40.8 eV, the peak at -9.2 eV decreases in intensity at -25.8 eV, the peak at about -12.2 eV increases in intensity, hence, it becomes most prominent peak at -31.8 eV. The peak at about -16.7 eV decreases in intensity at -37.8 eV and the peak at -19.7 eV disappears. So, the PES spectra is photon energy dependence and this is explained by the photoionization cross section of the valence electron orbitals. These structures are interpreted to be associated with the density of states features on the basis of the results of band structure calculation. Hence, peak at -9.2 eV arises from M symmetry point at -2.0 eV, the peak at -12.2 eV comes from M symmetry at -3.6 eV, the peak at -16.7 eV arises from M symmetry point at -4.8 eV and the peak at -19.7eV arises from M symmetry point at -5.4 eV. Finally, the energy gap (or energy level difference) between two peaks in the PES spectrum of (LaO)CuS fell within the range -0.5 eV to -7.5 eV indicating that they could be used for the development of solid – state devices such as blue light emitting diodes, lasers, solar cells and microwave devices.
Keywords: Photoemission spectroscopy, Electronic structure, Semiconductor, Energy level difference.