铁电极化调控SnSe薄膜光电性质研究

Optoelectric properties of SnSe thin-film regulated using ferroelectric polarization substrate

摘要:

利用脉冲激光沉积(PLD)技术在铌酸锂基片上沉积SnSe薄膜，研究了不同极化方向的铁电基片对SnSe薄膜光电性质的影响.控制PLD沉积时间，在铌酸锂基片上沉积出不同厚度的SnSe薄膜. X射线衍射和X射线光电子能谱的结果显示制备了高取向的单相SnSe薄膜.薄膜横截面高分辨透射电镜结果显示了薄膜具有较高的结晶质量.在无光照情况下，当铁电极化方向指向薄膜时，极化场可向SnSe薄膜中注入电子，使p型SnSe薄膜的电阻增加；当极化方向背离薄膜时，极化场可向SnSe薄膜中注入空穴，使p型SnSe薄膜的电阻降低.当用仅能使SnSe薄膜发生电子-空穴分离的632 nm激光照射时，不同极化方向的样品都表现出光电导增加的现象.当用405 nm激光照射时，不同极化方向的铌酸锂与薄膜界面处发生的电子-空穴分离使SnSe薄膜表现出完全不同的光电导效应.利用能带模型解释了不同铁电极化方向的铁电基片对SnSe薄膜光电导性质调控的机理.

Abstract:

To investigate the effect of ferroelectric substrate with different polarization direction on the optoelectric properties of SnSe, SnSe thin-films were synthesized using pulsed laser deposition (PLD) in LiNO₃ substrate. SnSe thin-film with different thickness was prepared by tuning the deposition time. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results show that high orientation single-phase SnSe thin-film was synthesized. Transmission electron microscope (TEM) image of the cross-section shows the high crystalline quality of the as-synthesized SnSe thin-film. In the darkness condition, for the polarization direction pointing to the thin-film, electrons would be introduced into SnSe thin-film, decreasing the conductivity of p-type SnSe. When the polarization direction points away from the thin-film, holes will be introduced into SnSe and thus enhance the conductivity of SnSe. Furthermore, the irradiation of 632 and 405 nm laser was used to test the effect of the coupling fields on the substrates with different polarization direction on the photoelectric effect. Both SnSe films on different polarization directions of LiNbO₃ show enhanced photoconductive effect because the 632 nm laser can only induce the photoelectric effect in SnSe thin-film. However, the 405 nm laser induces a completely different phenomenon. A typical band model was used to explain the regulation mechanism of SnSe photoconductive properties on ferroelectric polarization substrate with different polarization orientations.