气体分子吸附调控CdG电子结构和磁性的第一性原理研究

采用基于密度泛函理论的第一性原理方法,深入研究单个气体分子CO、NO、NO2、SO2、O2和H2S吸附对Cd掺杂石墨烯(CdG)电子结构和磁性的影响及调控机理。结果表明:六种气体分子以较大的吸附能与CdG基底中的Cd原子键合并形成Cd-X键(X代表C,O,N,S),属于化学吸附;由气体吸附注入的空穴使得复合体系的电子分布发生重构,致使复合体系电子结构和磁性明显改变。CO吸附后,体系仍保持CdG基底原有的半导体性,但带隙宽度有所变化;NO、NO2、SO2和O2吸附的CdG基底转变为金属性,H2S@CdG为半金属性。CO的吸附使得原本自旋极化的CdG基底磁性消失;NO2、H2S、NO和O2吸附基底时,产生局域自旋极化。对于NO2@CdG和H2S@CdG,自旋极化主要分布于基底之上且极化方向相同,NO2和H2S发生弱极化且自旋方向相反;而NO@CdG和O2@CdG的自旋分布特征与之相反;SO2@CdG呈现完全自旋极化特征,即SO2和基底皆有显著的自旋分布但自旋方向不同。据此,由各气体分子引起体系电子结构和磁性的不同变化特征,可有效检测和甄别气体分子。

First-principles Study on Modulation Mechanism of the Electronic Structures and Magnetic Properties of CdG by Gas Molecules Adsorption

The effect of single gas molecule(CO,NO,NO2,SO2,O2 and H 2S)adsorption on the electronic structures and magnetic properties of Cd-doped graphene(CdG)and its modulation mechanism were studied by using first-principles analysis based on density functional theory(DFT).The results show that gas molecule combines to the Cd atom in CdG substrate and Cd-X bond is formed(X=C,O,N,S),which belongs to chemisorption.The electron distribution of the combined system is reconstructed by the holes injected by gas adsorption,and the structures and magnetic properties of the combined system obviously change.For CO adsorption,the system remains the original semiconducting property of the CdG substrate,but the width of band gap is changed.The CdG substrate transforms into metallic property by adsorption of NO,NO2,SO2 and O2,while H 2S@CdG shows half-metallic property.In addition,the magnetism of the original spin-polarized CdG substrate disappears after CO adsorption;the systems of NO2,H2S,NO and O2 adsorbed CdG produce the local spin-polarization;For NO2@CdG and H 2S@CdG,spin-polarization are mainly distributed on the substrate and the two gas molecules have only weak polarization with opposite spin direction;In contrast,the spin distribution of NO@CdG and O2@CdG is opposite.SO2@CdG shows the characteristics of complete spin polarization and the spin states of both the gas and CdG are in the opposite direction.Thus,gas molecule can be effectively detected and identified according to the different characteristics of electromagnetic properties caused by each gas molecule adsorption.