Effect of electric field on the electronic properties of functionalized germanane by organic molecular adsorption

Abstract

Modulating the doping effect and charge transfer in germanane is very important for germanane-based electronic or optoelectronic devices with reproducible electrical characteristics. In this letter, we investigate the effect of electric field on the electronic properties of functionalized germanane by tetrathiafulvalene (TTF) molecular adsorption through first-principles calculations. It is found that the nondestructive n-type doping effect induced by tetrathiafulvalene (TTF) molecular adsorption could be linearly tuned by external electric field ranged from −0.3 V/Å to 0.3 V/Å. Especially under the electric field of −0.3 V/Å, an excellent n-type doping in germanane can be realized where the energy difference between the filled band maximum of dopant and the conduction band minimum of germanane for electron excitation is only 0.085 eV. More interestingly, once the external electric field exceeds 0.15 V/Å, the typical electron donor molecule TTF would even overturn to accept the electrons from germanane substrate.