Roome Nathanael J, Carey J David
Advanced Technology Institute, University of Surrey , Guildford GU2 7XH, United Kingdom.
ACS Appl Mater Interfaces. 2014 May 28;6(10):7743-50. doi: 10.1021/am501022x. Epub 2014 Apr 28.
Two-dimensional materials are one of the most active areas of nanomaterials research. Here we report the structural stability, electronic and vibrational properties of different monolayer configurations of the group IV elemental materials silicene and germanene. The structure of the stable configuration is calculated and for planar and low (<1 Å) atomic buckling configurations, analysis of the electronic band structure reveals linear band dispersion giving rise to massless Dirac Fermions with a Fermi velocity about two-thirds that of graphene. Monolayer stability is shown to be directly attributed to the phonons present with the instability being driven by the out-of-plane ZA and ZO phonon modes. Long momentum relaxation lengths and high carrier mobilities are predicted for silicene and germanene based devices as carrier relaxation via phonon scattering is found to be inhibited as the electron-optical phonon coupling matrix elements are calculated to be small, being about a factor of 25 times smaller than in graphene. The consequences for phonon scattering, high energy electrical transport and integration of elemental monolayers into electronic devices are further discussed.
二维材料是纳米材料研究中最活跃的领域之一。在此，我们报告了第IV族元素材料硅烯和锗烯不同单层构型的结构稳定性、电子和振动特性。计算出了稳定构型的结构，对于平面和低（<1 Å）原子屈曲构型，电子能带结构分析揭示了线性能带色散，产生了无质量狄拉克费米子，其费米速度约为石墨烯的三分之二。单层稳定性被证明直接归因于存在的声子，不稳定性由面外ZA和ZO声子模式驱动。对于基于硅烯和锗烯的器件，预测了长的动量弛豫长度和高的载流子迁移率，因为通过声子散射的载流子弛豫被发现受到抑制，因为计算出的电子 - 光学声子耦合矩阵元素很小，比石墨烯中的小约25倍。进一步讨论了声子散射、高能电输运以及元素单层集成到电子器件中的后果。
