3.1.4. XPS
Surface characterization of the 20cd20 and 20cd0 samples has been carried out by XPS. The survey spectra were shown in Fig. 4(a) that indicates the presence of carbon, cadmium, oxygen and zinc in the 20cd20 [24]. There was no peak corresponding to the Cd in the 20cd0. The peak of carbon (C (1s)) in both samples is due to the presence of adventitious elemental carbon and some surface contamination [7]. Fig. 4(b) shows the core level spectra of the Cd (3d) that consists of the Cd (3d5/2) and Cd (3d3/2) spin orbit com- ponents that are located at binding energy of 405.0 and 411.8 eV, respectively [25]. The binding energy of the Cd (3d) is attributed to the Cd2+ bonding state of the CdO in the (ZnO)1−x (CdO)x nanofibers. Fig. 4(c) shows the Zn (2p) region of the 20cd20 nanofibers that con- sist of the Zn (2p3/2) and Zn (2p1/2) spin orbit components located at binding energy of 1022.2 and 1045.3 eV, respectively. The Zn (2p) core level spectrum is believed to be the Zn2+ of the ZnO wurtzite crystal structure [7].