半羟化的碳化硅片的第一性原理研究

First principle study on hydroxylated SiC sheet

通过密度泛函理论,研究了碳化硅片被羟化时的电磁特性.所研究的碳化硅片为六角蜂窝状结构,碳硅原子之比为1∶1,相间排列.由于碳化硅片中含碳、硅两种元素;为此,分别考虑了全部的碳原子以及全部的硅原子分别被羟化的情形,结果发现了丰富的电磁特性.由于羟基对羟化原子的吸引作用,碳硅原子出现分层,对应于碳、硅原子被羟化时的碳硅层间距分别为0.671、0.390,碳硅键长度也分别伸长为1.904、1.861,而对应的键角C-O-H与Si-O-H分别为107.8°、114.1°,表现了新奇的几何结构特点.由形成能计算发现羟化是放热的,说明此过程易实现.为寻找到最稳定的磁状态,分别考察了铁磁、反铁磁以及非磁三种构型,结果发现,当所有碳原子被羟化时,材料为非磁性的正常金属;而当其中所有的硅原子被羟化时,是直接带隙为1.12 eV的反铁磁半导体.其中,硅被羟化时的结构更稳定.这些说明通过调节碳化硅片中羟化的不同位置,可以有效地调节碳化硅片的电磁特性,预示着在未来的纳米功能材料中可能的应用.

By using density functional theory we have studied the electronic and magnetic properties of the hydroxylated SiC sheet.The studied SiC sheet belongs to hexagonal honeycomb structure,in which the ratio of C to Si is 1∶1 and each carbon atom alternates with each silicon atom.Different from grapheme which only includes one element:carbon atoms,there are two kinds of inequivalent sites in SiC sheet:carbon and silicon,and so we study two cases of half-hydroxylation:one is that all carbon atoms are hydroxylated ...