Figure 3. XPS spectra of germanane, siloxene and GeNSs/SiNSs heterostructure. (A) Survey spectra, (B) Ge 3d, (C) Si 2p and (D) O 1s. (E) UV-vis-NIR absorption spectra of GeNSs, SiNSs, and GeNSs/SiNSs H1, H2, and H3. (F) Tauc plot diagram of GeNSs and SiNSs.