Study on the electrical properties of armchair silicon nanotubes

The band structures and state densities of armchair silicon nanotubes with chiral index m = n = K (integer K is 3 ∼ 15) are studied by using the first-principles method of density functional theory in this paper. The results show that (3, 3) armchair silicon nanotube is the indirect band-gap structure, and the rest are the direct band-gap structure. With the increase of the chiral index, the diameter of the silicon nanotubes increases, the band-gap width of the silicon nanotubes decreases gradually, the conduction band moves down gradually, and the peak intensity of the total density diagram increases. (3, 3) armchair silicon nanotube has the widest band-gap. Armchair silicon nanotube (13, 13) has the smallest band-gap width, indicating that its electrical conductivity is better than those of armchair silicon nanotubes with other chiral indexes. Meanwhile, the conduction and valence bands of (4, 4) armchair silico nanotube overlap, indicating that it is the metallic nanotube. The state density diagram shows that the top of the valence band of (9, 9) armchair silicon nanotube is mainly composed of Si-3p electron states, and the bottom of the conduction band is composed of Si-3p and Si-3s state electrons. (authors)