Fig. 2: Bandgap engineering by stacking BP layers.
From: Bandgap engineering of two-dimensional semiconductor materials
a Experimentally observed absorption spectrum in N-BP, N = 4, 5, 7, 846, where peaks are identified as the Eij transitions labeled in (d). b Positions of experimentally observed (symbols) peaks labeled as E11 (black), E22 (red), E33 (blue), and E44 (green), as a function of the number of layers N. Theoretical predictions (see text) are shown as curves. c Energy bands in monolayer, bilayer, and trilayer BP. d Conduction (Ee) and valence (Eh) band edges, separated by a \({E}_{gap}^{(1)}\) gap in the monolayer case. As the number of layers N increase, more bands appear around Ee(h), with energies Ee(h) ± te(h), for 2-BP, and \({E}_{e(h)}\pm \sqrt{2}{t}_{e(h)}\), for 3-BP. For N-BP, N bands appear around Ee(h), whose energies can be estimated by the eigenvalues of a Toeplitz matrix (see text). Panels a, b reused from Springer Nature/Zhang et al.46, permissible under a CC-BY [4.0/3.0] license.
