Electronic properties of alkali- and alkaline-earth-intercalated silicon nanowires

We present a first-principles study of the electronic properties of silicon clathrate nanowires intercalated with various types of alkali- or alkaline-earth atoms. We find that the band structure of the nanowires can be tailored by varying the impurity atom within the nanowire. The electronic character of the resulting systems can vary from metallic to semiconducting with direct band gaps. These properties make the nanowires specially suitable for electrical and optoelectronic applications.

Figure 1

(Color online) Top and lateral views of two unit cells of (a) a $2\mathrm{M}$ at Si(30) and (b) a $2\mathrm{M}$ at Si(36), where M is an alkali- or alkaline-earth atom.

Figure 2

Band structure of pristine (first top box), alkaline-earth-intercalated (next three top boxes), and alkali-intercalated (bottom) Si(30) nanowires.

Figure 3

Band structure of pristine (first top box), alkaline-earth-intercalated (next three top boxes), and alkali-intercalated (bottom) Si(36) nanowires.

Figure 4

(Color online) Projected density of states on the silicon atoms of (a) a pristine Si(36), (b) a Na-deformed pristine Si(36), (c) a 2Na at Si(36), (d) a Ba-deformed pristine Si(36), and (e) a 2Ba at Si(36). The dashed lines in graphs (c) and (e) are the projected densities of states on the sodium and barium atoms, respectively, multiplied by a factor of 3 for clarity.