Stanene is a quantum spin hall insulator and a favourable material for electronic and optoelectronic devices. Density functional theory (DFT) calculations are performed to study the band gap opening in stanene by investigating the effect of beryllium and magnesium doped stanene single layer to study the electronic and structural properties in stanene. The electronic band energy of pure stanene without spin orbit coupling (SOC) appear to show no energy gap at the Fermi level showing that stanene is a gapless material with Dirac cones at the K point and the band gap opens by a gap of 0.08 eV is opened at the K point. The electronic structure of Be and Mg doped stanene shows that the Fermi level is shifted towards the valance band edge when compared to pure stanene. We have considered 6.25, 12.5, 18.75 and 25% of both Be and mg doping. The electronic structure of Be doped stanene show that the Fermi level is shifted towards the valance band edge when compared to pure stanene. The Dirac point of stanene locates at Γ shifted by 0.38 and 0.51eV for 6.25 and 12.5 %, an energy band gap of 0.27 and 0.50 eV were obtained above the Fermi level for 6.25 and 12.5% respectively. In the case of Mg, the bandgap remains slightly above the Fermi-level and amounts to 0.34 eV for 6.25 % and 0.43eV for 12.5 %, in the case of 18.75 and 25 % the Dirac cone disappear completely, an energy gap of 0.28 eV and 0.60 eV were obtained above the Fermi level for 6.25 and 12.5% respectively, our findings show that the band gap of stanene open at 12.5% doping concentration of both Be and Mg impurities. These obtained band-gap value seem to be sufficient for use of alkaline earth metal doped stanene in optoelectronic and such applications where stanene is incapacitate for its use to switch on/off devices.
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