Study On The Effect Of Pulsed Laser-Produced Plasma State On Film Deposition Characteristics

Pulsed laser deposition(PLD)technology is widely used in the controllable preparation of complex oxide heterostructures,superlattices and interface materials because of its freely adjustable process parameters and easy to obtain desired stoichiometric materials.The in-depth study on it is not only helpful to develop and explore the new properties and functions of these materials,but can also reveal the special role of PLD technology in the preparation of them.At present,the research on PLD technology is still focused on the influence of experimental parameters on the deposition characteristics of thin films,and the plasma state which directly affects the deposition characteristics of thin films has not been studied.Electron temperature and electron density are two important parameters to characterize the state of plasma.The emission of plasma far from the ablation target is very weak,which brings great difficulties to the diagnosis of electron temperature and density and the study of their spatio-temporal evolution behavior.Most of the reported work is focused on the diagnosis of the plasma state within 2.0 cm from the target surface.However,in order to obtain quality-fine thin films,substrates are often placed farther away.Therefore,the purpose of this work is to diagnose the state parameters of plasma near the substrate in PLD,to study the effect of pulsed laser-produced plasma(LPP)on the deposition characteristics,and to provide parameters of plasma state for the further study of the interaction between plasma and substrate,the physical mechanism of thin film growth on the atomic scale and the precise control of the deposition process.The specific work is as follows:(1)A new experimental device for nanosecond pulsed laser deposition and diagnosis of plasma state was built independently.Based on spatio-resolved and time-integrated emission spectroscopic technique,the weak emission spectra of TiO₂ plasma were detected in the space of 3.0-11.0 cm away from the target surface by improving and optimizing the experimental design.TiO₂ films were deposited at 6.0,7.0,8.0,9.0 and10.0 cm away from the target surface,respectively.(2)Combined with Saha-Boltzmann plot and Stark broadening method,the spatial evolution of electron temperature and density were obtained according to the detected spatial evolution spectra of TiO₂ plasma,and the slight differences of electron temperature and density at different locations in this region were distinguished.The temperature and density gradients were given.The effects of the diagnostic results on the deposition characteristics of thin films were analyzed and discussed.(3)The morphology,element species and their corresponding distribution,element valence,optical and electrical properties of deposited TiO₂ thin films were characterized and analyzed by scanning electron microscope(SEM),X-ray energy spectrum(EDS),X-ray photoelectron spectroscopy(XPS),ultraviolet-visible absorption spectroscopy(UV-Vis spectroscopy)and four-probe resistance measurement.The effect of deposition distance on the properties of thin films was discussed.