Band-gap unification of partially Si-substituted single-wall carbon nanotubes

Abstract

The atomic and electronic structure of a set of pristine single wall SiC nanotubes as well as Si-substituted carbon nanotubes and a SiC sheet was studied by the local-density approximation ͑LDA͒ plane wave band structure calculations. Consecutive substitution of carbon atoms by Si leads to a gap opening in the energetic spectrum of the metallic ͑8,8͒ SWCNT with approximately quadratic dependence of the band gap upon the Si concentration. The same substitution for the semiconductor ͑10,0͒ single wall carbon nanotubes ͑SWCNT͒ results in a band gap minimum ͑0.27 eV͒ at ϳ25% of Si concentration. In the Si concentration region of 12-18 %, both types of nanotubes have less than 0.5 eV direct band gaps at the ⌫-⌫ point. The calculation of the chiral ͑8,2͒ SWSi 0.15 C 0.85 NT system gives a similar ͑0.6 eV͒ direct band gap. The regular distribution of Si atoms in the atomic lattice is by ϳ0.1 eV/ atom energetically preferable in comparison with a random distribution. Time dependent density functional theory ͑DFT͒ calculations showed that the silicon substitution sufficiently increases ͑roughly by one order of magnitude͒ the total probability of optical transitions in the near infrared region, which is caused by the opening of the direct band gap in metallic SWCNTs, the unification of the nature and energy of the band gaps of all SWCNT species, the large values of ͗Si3p͉r͉Si3s͘ radial integrals and participation of Si3d states in chemical bonding in both valence and conductance bands.

Electronic Structure of Si-Doped BN Nanotubes Using X-ray Photoelectron Spectroscopy and First-Principles Calculation

“…Unlike CNTs, the band structure of BNNTs shows semiconducting properties with a nearly constant band gap (5.5 eV), which is weakly dependent on the tube diameter and chirality. − Therefore, the modification of their properties by doping has attracted a great deal of interest. Recent work has revealed that the band gap of BNNTs can be effectively tailored by carbon (C) doping, depending on their atomic compositions and configurations. − On the other hand, the doping of silicon (Si), which belongs to the same group as C, group IV, but strongly prefers sp 3 -like bonding, is considered to influence the electronic and structural properties of CNTs and BNNTs in a different way from that of C doping. − Theoretically, it was predicted that the large outward displacement of the Si atom and its nearest-neighbor C atoms may impose changes in the chemical reactivity and, hence, in the interaction with foreign atoms and molecules through the Si sites. , A quadratic dependence of the band gap upon the Si concentration was also calculated for single-walled CNTs . Unfortunately, no experimental reports of Si-doped CNTs have so far been published, which would allow the theoretical predictions to be confirmed.…”

“…[6][7][8][9][10][11][12][13] On the other hand, the doping of silicon (Si), which belongs to the same group as C, group IV, but strongly prefers sp 3 -like bonding, is considered to influence the electronic and structural properties of CNTs and BNNTs in a different way from that of C doping. [14][15][16][17][18][19][20] Theoretically, it was predicted that the large outward displacement of the Si atom and its nearest-neighbor C atoms may impose changes in the chemical reactivity and, hence, in the interaction with foreign atoms and molecules through the Si sites. 14,15 A quadratic dependence of the band gap upon the Si concentration was also calculated for singlewalled CNTs.…”

A study on Si and P doped h-BN sheets: DFT calculations

“…The doping of silicon (Si), which belongs to the same group as C, is also studied for carbon nanotubes (CNTs) [45] and boron nitride nanotubes (BNNTs) [46]. In the present work, Si and phosphorus (P) substituted h-BN sheets were considered using density functional theory (DFT) in order to assess the influence of Si and P dopants on the structural and energetics properties at the B and N sites.…”

First principles study of electronic and structural properties of single walled zigzag boron nitride nanotubes doped with the elements of group IV

“…Experimental measurements based on Cathodoluminescence method have estimated values from 5.3 to 5.4 eV [19,20]. Studying the effects of group IV elements on the electronic properties of BNNT's is an attractive subject that many workers have reported many of the structural and electronic properties for C, Si and Ge-doped BNNT in recent years [21][22][23][24][25][26][27][28][29][30][31][32]. However there are not any researches considering the effects of Sn and Pb.…”