Density Function Theory Study On The Bandstructure Modulating Of Germanene And Germanium Quantum Dots

Crystalline germanium has shown great potential in the applications of various fields such as integrated circuit,photovoltaics,bioimaging due to its unique characteristics,including good compatibility,large exciton bohr radius,high electronic carriers mobility.Recently,low dimensional(0 D,1D,2D)germanium has gained more and more attention since germanene successfully synthesized on Pt and Au substrates,which effectively promoted the application of germenene in various fields.In this work,we have studied the effects of surface modification(hydrogermylation,alkoxylation,aminization and phenylation)on the electronic structure of hydrogen-passivated germanene(germanane),and the effects of boron and phosphorus doping on the electronic structure modulating and formation mechanism of germanium quantum dots.The main research results are as follows:(1)Hydrogermylation,alkoxylation,aminization and phenylation hardly influence the geometrical structure of germanane.However,organic surface modification will increase bandgap of germanane,especially aminizated and phenylated germanane.Hydrogermylated germanane and alkoxylated germanane are direct-bandgap semiconductors.In contrast,aminated germanane and phenylated germanane are indirect-bandgap semiconductors.(2)The formation energy of B-doped Ge QDs decreases as B atom moves from the center of Ge QDs to the surface,which means,B atom tends to located at the surface of Ge QDs.B-doping has induced deep defect energy levels above the valence band when B is inside Ge QDs while it has induced deep of Ge QDs.The P-doping Ge QDs is similar to B-doping Ge QDs,yet the formation energy of P-doping Ge QDs is higher than of B-doping Ge QDs,therefore B atoms defect energy levels around the center of forbidden band when B locates at the surface are more easily incorporated into Ge QDs than P atoms.(3)For the B-P co-doped Ge QDs,the formation energy is smaller than both B doped Ge QDs and P doped Ge QDs,and the electronic structure has also been introduced of deep defect energy levels.