气体吸附对硅锗异质结纳米线电子结构与光学性质的影响

基于密度泛函理论体系下的广义梯度近似(GGA),采用第一性原理方法探讨了沿[112]晶向的硅锗异质结纳米线作为气体传感器检测CO,CO₂和Cl₂的能力，着重计算了其吸附气体分子前后的吸附能、能带结构与光学性质.几何结构优化计算表明：不同硅锗组分的[112]晶向的硅锗纳米线对CO,CO₂和Cl₂分子的吸附能的绝对值在0.001 eV至1.36 eV之间，其中Si₂₄Ge₃₆H₃₂对CO₂气体的吸附能最大，气敏性能最好.能带结构计算表明：吸附CO和CO₂分子的[112]晶向硅锗纳米线能带的简并度明显减小，带隙变化较小；而吸附Cl₂分子后的价带顶与导带底之间产生了杂质能级使其带隙减小.光学性质计算表明：Si₂₄Ge₃₆H₃₂纳米线吸附CO, CO₂和Cl₂分子后的光学...

ffects of gas adsorption on electronic structure and optical properties of SiGe heterojunction nanowires

Based on the generalized gradient approximation (GGA) under the density functional theory system, the first-principles approach was used to investigate the ability of SiGe nanowires along the [112] crystallographic orientation as molecular sensors to detect CO, CO2 and Cl2. The adsorption energies, energy band structures and optical properties before and after adsorption of gas molecules were mainly calculated. The calculation of geometric structure optimization shows that the absolute values of adsorption energy of CO, CO2 and Cl2 molecules on the [112] crystal orientation of SiGe nanowires with different SiGe compositions are between 0.001 eV and 1.36 eV, and the adsorption energy of Si24Ge36H32 for CO2 gas is maximum and gas sensing performance is the best. The energy band structure calculation shows that the energy band degeneracy of the [112] crystal-oriented SiGe nanowires adsorbed by CO and CO2 molecules is significantly reduced, and the band gap change is small. The impurity energy level is generated between the top of the valence band and the bottom of the conduction band after adsorption of Cl2 molecules, which reduces the band gap. The calculation of optical properties shows that the optical properties of Si24Ge36H32 nanowires after adsorptions of CO, CO2 and Cl2 molecules are obviously different, which is mainly reflected in the range of the absorption spectrum and the amplitude of the absorption peak. The above research results provide a theoretical basis for [112] Si24Ge36H32 nanowires as a sensitive material for gas sensors.