Preparation Of Ce-doped ZnO Nanofilms And Their Nonlinear Absorption Properties

ZnO nanomaterials have many excellent properties.With various nanostructures and morphologies,ZnO nanomaterials have a wide range of applications in the preparation of gas-sensitive sensor devices,optoelectronic devices,and solar cells.ZnO nanomaterials have inherent defects limiting their application fields,so that the optical,electrical,magnetic,and catalytic properties of ZnO nanomaterials by incorporating some metal materials can be improved.Ce has very good optical properties since its discovery,such as increasing the light conversion rate,being used as a flint stone,and absorbing ultraviolet and infrared as glass additives.In this paper,Ce-doped ZnO?CZO?nano-film materials were prepared by RF-DC co-sputtering experiments.The effects of experimental parameters on the surface morphology,optical absorption,structural components and chemical valence of the samples were studied.The fs Z-scan technology was used to study the nonlinear absorption characteristics of CZO films and the physical mechanism of nonlinear absorption.First,the magnetron sputtering technology was used to control the experimental parameters to obtain CZO thin film materials,and the dependence of material structure,morphology,composition and experimental parameters was studied.The results show that the thickness of the film will be affected by the sputtering time.With the increase of the sputtering time,the thickness of the film will increase.When the sputtering time is 60 minutes,the thickness of the film was about 100 nm.The surface morphology of the CZO film appears clustering at low power,and the clustering phenomenon disappears at high power;changing the substrate temperature will affect the crystalline quality of the CZO nanofilm,the higher the sinking temperature,The better the crystalline quality of the film,which is due to the increased surface diffusion of the adsorbed material of the film.Secondly,the crystal morphology and chemical composition of the material were characterized and analyzed.It was confirmed by photoelectron spectroscopy that Ce ions existed in the ZnO lattice.It was found that Ce element exists in the CZO film in the form of Ce³⁺and Ce⁴⁺coexistence.The characteristic peaks of the Raman spectrum of the CZO material were analyzed,and the vibrational energy levels of the material were obtained.The characteristic mode of each peak position was determined,thereby confirming the existence of functional groups.Thirdly,the linear ultraviolet-visible absorption spectrum and band gap structure of CZO thin film materials were studied.The band gaps of CZO films at different sputtering powers were calculated by using absorption spectra to be 3.30,3.30,3.28,3.26,and 3.29 e V.Compared with the undoped ZnO film,the incorporation of Ce caused the blue shift of the absorption wavelength of the ZnO material.As the Ce doping concentration becomes larger,the band gap becomes smaller and then becomes larger,and the edge of the absorption band is first red-shifted and then blue-shifted.Finally,the femtosecond Z-scan technology was used to study the non-linear absorption characteristics of CZO films,to obtain the non-linear absorption coefficient,and to reveal its physical mechanism.The effects of DC sputtering power and laser intensity on the nonlinear optical absorption properties of CZO films were discussed.The results show that CZO films exhibit saturation absorption?SA?or reverse saturation absorption?RSA?behavior.And the nonlinear absorption mechanism of the CZO film was converted from SA to RSA.Under different laser excitation intensities,the nonlinear absorption mechanism of CZO films with DC sputtering power of 25 W is TPA-induced RSA.In addition,the results show that the nonlinear absorption coefficient of the CZO film is on the order of 10^-8 m/W.In summary,the analysis of the surface morphology,structural composition,linear absorption,and nonlinear absorption of CZO thin film materials shows that the nonlinear absorption coefficient of CZO thin films is large under certain experimental parameters,so CZO nanofilms are Promising candidates for further optoelectronic device applications which provide important experimental evidence for applications in optical switching,optical limiting,optical communications,and integrated optics.