Electronic properties, doping, and defects in chlorinated silicon nanocrystals

Abstract

Silicon nanocrystals with diameters between 1 and 3 nm and surfaces passivated by chlorine or a mixture of chlorine and hydrogen were modeled using density functional theory, and their properties compared with those of fully hydrogenated nanocrystals. It is found that fully and partially chlorinated nanocrystals are stable, and have higher electron affinity, higher ionization energy, and lower optical absorption energy threshold. As the hydrogenated silicon nanocrystals, chlorinated silicon nanocrystals doped with phosphorus or boron require a high activation energy to transfer an electron or hole, respectively, to undoped silicon nanocrystals. The electronic levels of surface dangling bonds are similar for both types of surface passivation, although in the chlorinated silicon nanocrystals some fall outside the narrower energy gap.

Size dependence of the stability, electronic structure, and optical properties of silicon nanocrystals with various surface impurities

“…Despite the great number of experimental, as well as theoretical, studies of Si NCs, there are only few studies concerning the size dependence of the stability of Si NCs with surface impurities [55,60,61]. In order to investigate the stability of the NCs with different surface impurities, depending on the size of the NCs, we calculated the formation energy of the different NCs [E f (Si N H M X)], per surface area, using the equation NC.…”

“…[2][3][4]32,33,[44][45][46][47][48][49][50][51][52][53][54][55], to name a few. However, there have been only a limited number of theoretical studies concerning the size dependence of the electronic and optical properties of Si NCs with different surface impurities [4,[33][34][35][52][53][54][55][56][57][58]. A number of these articles focus on the influence of only one surface impurity [33,34,52,54,55], while in others, the Si NCs with partially passivated or fully passivated surface with impurities are studied [4,35,53,[56][57][58].…”

“…However, there have been only a limited number of theoretical studies concerning the size dependence of the electronic and optical properties of Si NCs with different surface impurities [4,[33][34][35][52][53][54][55][56][57][58]. A number of these articles focus on the influence of only one surface impurity [33,34,52,54,55], while in others, the Si NCs with partially passivated or fully passivated surface with impurities are studied [4,35,53,[56][57][58]. Among these works, there have been only a few studies of the effect of the surface impurities on the electronic and optical properties for Si NCs larger than 2 nm [4,33,55].…”

“…A number of these articles focus on the influence of only one surface impurity [33,34,52,54,55], while in others, the Si NCs with partially passivated or fully passivated surface with impurities are studied [4,35,53,[56][57][58]. Among these works, there have been only a few studies of the effect of the surface impurities on the electronic and optical properties for Si NCs larger than 2 nm [4,33,55]. Based on their calculations, Vasiliev et al [34] estimated that the effect of the oxygen on the states around the gap should be present for NCs with size ∼2-2.5 nm, and Wolkin et al [33] showed that the electron can be trapped in oxidized NCs smaller than ∼3 nm.…”

Density functional theory study on the boron and phosphorus doping of germanium quantum dots

“…26,41 By carrying out appropriate surface modication and annealing processes, we may obtain defect-free Ge QDs, akin to that for Si QDs 52,53 and twodimensional materials. 54,55 We calculated the formation energy (E f ) of a B or P atom in Ge QD by using 56,57…”