【摘要】 A~ⅤB~ⅥC~Ⅶ(A=Bi,Sb;B=S,Se;C=I,Br)体系是一类典型的准一维链状半导体材料.由于其特殊的晶格和能带结构,A~ⅤB~ⅥC~Ⅶ体系表现出丰富的物性,如:铁电、压电、热电和光电导特性等,在太阳能电池、光电探测器及超级电容器等领域有着广泛的应用前景,引起了人们广泛的研究兴趣.其中,SbSI在低温下伴随铁电自发极化会出现反常的负热膨胀现象.BiSeI与SbSI结构类似,低温下的物性值得进一步研究.本工作利用物理气相输运法制备了高质量的BiSeI单晶样品,并利用Raman光谱、电输运测量、XRD及光致发光谱(PL)对其低温下的电输运、振动及结构性质进行了系统的研究.随温度降低,PL光谱结果表明低温下能隙内出现激子能级.低温Raman及XRD结果表明测试温区(10～300 K)内其结构对称性无明显改变.然而随温度降低,晶格在200～300 K范围内发生明显的负热膨胀现象.类比于SbSI,我们将BiSeI中的负热膨胀现象归因于410 K发生的反铁电相变.此工作的顺利开展有利于人们进一步理解A~ⅤB~ⅥC~Ⅶ体系低温下负热膨胀背后的物理机制以及促进其在未来零膨胀材料领域中的应用.更多还原

【Abstract】 A~ⅤB~ⅥC~Ⅶ(A=Bi,Sb;B=S.Se;C=I, Br) family belongs to a typical quasi-one dimensional semiconductor.Due to the peculiar lattice and band structures.they exhibit rich physical properties,such as ferroelectricity,piezoelectricity,thermoelectricity and photoconductivity,leading to the potential applications in solar absorber,photodetector and supercapacitor,which attract wide research interests.Among them,accompanying with the ferroelectric phase transition,the negative thermal expansion(NTE) behavior was observed in SbSI.BiSeI is isostructural to SbSI,the physical properties at low temperature of BiSeI deserve further investigation.Here,BiSeI single crystals with the high quality were prepared by physical vapor transport method.The electrical transport,vibrational and structural properties were systematically studied through Raman scattering,photoluminescence(PL),electrical resistance and x-ray diffraction spectra(XRD) at low temperature.With decreasing temperature,PL results show that the appearance of exciton levels inside the gap below 60 K.Raman and XRD measurements demonstrate that the structure of BiSeI is stable upon cooling.However,the NTE behavior is observed in the temperature range of 200～300 K.Analogous to SbSI,we attributed the NTE behavior to the occurrence of antiferroelectric phase transition at 410 K of BiSeI.Our work will shed light on the further understanding of underlying physics of NTE behavior in A~ⅤB~ⅥC~Ⅶ system and promote their potential applications in future zero thermal expansion materials.更多还原