Effects 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]crystallo-graphic orientation as molecular sensors to detect CO,CO2 and Cl2.The adsorption energies,energy band struc-tures 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 mole-cules 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 Si24 Ge36H32 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-ori-ented 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 conduc-tion 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 ob-viously different,which is mainly reflected in the range of the absorption spectrum and the amplitude of the ab-sorption peak.The above research results provide a theoretical basis for[112]Si24 Ge36 H32 nanowires as a sensi-tive material for gas sensors.
国家科技期刊平台
NSTL
万方数据
维普
