KF-catalyzed Growth Of MoS₂ And NiO Thin Films

With the rapid development of microelectronic devices and the continuous improvement of the integration of electronic devices,researchers have gradually turned their attention to two-dimensional nanomaterials with semiconductor properties.Among them,MoS₂ and NiO have been widely concerned by researchers because of their good structural stability and excellent performance.MoS₂ is a typical transition metal chalcogenide compound,and its band gap is controllable with the change of the number of layers,and the fluorescence properties of the films vary with the number of layers.NiO is a kind of wide band gap P-type semiconductor material with typical 3D electronic band structure and excellent electrical and optical properties,which is widely used in electrochromic devices,memory and so on.In this paper,MoS₂ and NiO thin films were prepared by chemical vapor deposition(CVD),and the effects of different conditions on the quality of thin films were investigated by scanning electron microscope,Raman spectroscopy,photoluminescence spectra and so on.The main results are as follows:(1)four kinds of MoS₂ with different morphologies were prepared by CVD.Raman spectra show that MoS₂ with different morphologies have different layers;PL spectra show that the luminous intensity of single-layer molybdenum disulfide is the highest,and the luminous intensity decreases gradually with the increase of the number of layers or the appearance of defects such as grain boundaries.To explore the catalytic effect of KF on the growth of MoS₂,the size of monolayer MoS₂ increased from 2?m to 8?m at the same temperature by adding KF,and 4?m monolayer MoS₂ was prepared at a lower temperature of 650?.(2)the effects of different experimental parameters on the growth quality and size of NiO thin films were investigated by chemical vapor deposition,and the optimal conditions for preparing NiO thin films were successfully obtained.Through the analysis of the experimental results,the temperature and the amount of KF have an important influence on the growth of NiO.By controlling the amount of KF,we can catalyze the growth of NiO thin films at lower temperature.(3)the physical properties of the NiO films were characterized and the growth mechanism was analyzed.XPS and TEM analyses show that the obtained thin films are NiO thin films and grow on Al₂O₃(0001)substrates along the NiO(111)crystal plane.The optical absorption of NiO thin film was tested by UV-vis spectrophotometer.the results showed that the absorption of NiO thin film was strong in the ultraviolet region.The optical bandgap width of NiO thin film was about 2.86 e V.Finally,the growth mechanism of NiO thin films is analyzed:the growth relationship between NiO thin films and substrates is determined by the arrangement of atoms in the topmost surface.However,due to the existence of mirror symmetrical oxygen sublattices on the sapphire(0001)plane,there are two kinds of triangular domains rotated by 180°on the sapphire(0001)plane,which is consistent with our experimental results.