气相输运沉积制备c轴择优取向的碘化铋薄膜

c-Axis-Oriented BiI_(3) Thin Films Prepared by Vapor Transport Deposition

铋基卤化物材料因其无毒和优良的光电性能而显示出巨大的应用潜力。BiI_(3)作为一种层状重金属半导体,已被用于X射线检测、γ射线检测和压力传感器等领域,最近其作为一种薄膜太阳能电池吸收材料备受关注。本文采用简单的气相输运沉积(VTD)法,以BiI_(3)晶体粉末作为蒸发源,在玻璃基底上得到高质量c轴择优取向的BiI_(3)薄膜。并通过研究蒸发源温度和沉积距离对薄膜物相和形貌的影响,分析了BiI_(3)薄膜择优生长的机理。结果表明VTD法制备的BiI_(3)薄膜属于三斜晶系,其光学带隙为~1.8 eV。沉积温度对薄膜的择优取向有较大影响,在沉积温度低于270℃时,沉积的薄膜具有沿c轴择优取向生长的特点,超过此温度,c轴择优取向生长消失。在衬底温度为250℃、沉积距离为15 cm时制备的薄膜结晶性能最好,晶体形貌为片状八面体。

Bismuth based halide materials show great potential because of their non-toxic and excellent photoelectric properties.As a layered heavy metal semiconductor,BiI_(3) has been used in X-ray detection,γ-ray detection and pressure sensor.Recently it attracted much attention as an absorbing material for thin film solar cells.In this paper,a simple vapor transport deposition(VTD)method is used to obtain high-quality BiI_(3) films with preferred c-axis orientation on glass substrate using BiI_(3) crystal powder as evaporation source.By studying the effects of evaporation source temperature and deposition distance on the phase and morphology of BiI_(3) thin films,the mechanism of preferential growth of BiI_(3) thin films was proposed.The results show that the BiI_(3) thin film prepared by VTD method belongs to triclinic crystal system,and its optical band gap is~1.8 eV.The deposition temperature has a great influence on the preferred orientation of the films.When the deposition temperature is lower than 270℃,the deposited thin films have the characteristics of preferred orientation growth along the c-axis.Beyond this temperature,the c-axis preferential orientation is not observed.When the substrate temperature is 250℃and the deposition distance is 15 cm,the thin films have the highest crystallanity and octahedral morphology.