Fundamental Properties of Hydrogen-Functionalized GaSe Monolayer.

Functionalization reveals potential opportunities for modifying essential properties and designing materials due to the strong interaction between functionalized atoms and the surface. Among them, hydrogenation possesses such a way to control electronic and optical characteristics. In this paper, the stability and transformed electronic, optical properties of H-functionalized GaSe in two cases (single and double sites) were reported that exhibit the effects of hydrogen functionalization via first-principles calculations. Formation energies suggest that H-functionalized GaSe systems are stable for construction. H-GaSe and 2H-GaSe display distinct properties based on the functionalized way (single- or double-site functionalization). Accordingly, H-GaSe is metallic, while 2H-GaSe belongs to a semiconductor. The magnetic configuration with ferro- and anti-ferromagnetic could be found in H- and 2H-functionalized cases through spin distribution, respectively. Especially, the chemical hybridized bonds of Se-H, Ga-Se, and Ga-Ga corresponding to s-sp 3 and sp 3 -sp 3 bondings, respectively, are clearly verified in the orbital-projected density of states and charge density. The optical properties of 2H-GaSe could provide the main characteristics of a semiconductor, which is the limited range of transparency by electronic absorption at short and long wavelengths. Moreover, increasing the number of GaSe segments ( L ) could change the band gap leading to application in the band gap engineering of the 2H-GaSe systems. Thus, hydrogen functionalization could provide the possible manner for adjusting and controlling features of GaSe, promising for the development of electronic devices and applications.