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采用基于密度泛函理论的第一性原理方法(DMOL3程序),在广义梯度近似(GGA)下,计算了硅纳米晶(Si75H76)在B和P掺杂和乙基(—CH2CH3)、异丙基(—CH(CH3)2)表面改性等情形下态密度、结合能及能隙的变化。结果表明:掺杂对体系的禁带宽度(约3.12eV)几乎没有影响,但会引入带隙态;三配位的B掺杂,在禁带中靠近导带约0.8eV位置引入带隙态,三配位的P掺杂在禁带中靠近价带0.2eV位置引入带隙态;四配位的B掺杂,在禁带中靠近价带约0.4eV位置引入带隙态,四配位的P掺杂在禁带中靠近导带约1.1eV位置引入带隙态;且同等掺杂四配位时体系能量要低于三配位;适当的乙基或异丙基表面覆盖可以降低体系的总能量,且表面覆盖程度越高体系能量越低,但在表面嫁接有机基团过多将导致过高位阻,计算时系统不能收敛。
The first-principle method based on density functional theory (DMOL3) was used to calculate the dependence of Si75H76 on B and P doping and ethyl (-CH2CH3) (-CH (CH3) 2) surface modification state density, binding energy and energy gap changes. The results show that the doping has almost no effect on the forbidden band width of the system (about 3.12eV), but it will introduce into the bandgap state. The three-coordinated B doping introduces the band gap state in the forbidden band about 0.8eV near the conduction band , The three-coordinated P-doping introduced into the bandgap near the valence band 0.2eV in the forbidden band. The four-coordinated B-doping introduced the bandgap near the valence band about 0.4eV, Of the P-doped bandgap in the forbidden band near the conduction band of about 1.1eV position; and the same doping four coordination system energy is lower than the three coordination; appropriate ethyl or isopropyl surface coverage can reduce the system Of the total energy, and the higher the degree of surface coverage, the lower the energy of the system, but excessive grafting of the organic groups on the surface will result in excessive steric hindrance and the system will not converge during the calculation.