关键词: 氮化镓纳米薄膜/
表面修饰/
应变/
电磁学性质
English Abstract
Strain field tuning the electronic and magnetic properties of semihydrogenated two-bilayer GaN nanosheets
Xiao Mei-Xia,Liang You-Ping,
Chen Yu-Qin,
Liu-Meng
1.College of Materials Science and Engineering, Xi'an Shiyou University, Xi'an 710065, China
Fund Project:Project supported by the Scientific Research Foundation of the Education Department of Shaanxi Province, China (Grant No. 2013JK0894), the National College Students' Training Programs for Innovation and Entrepreneurship of Shaanxi province, Chine (Grant No. 201510705230), the Youth Science and Technology Innovation Fund of Xi'an Shiyou University, China (Grant No. 2012BS004), and the Provincial Superior Discipline for Materials Science and Engineering of Xi'an Shiyou University, China (Grant No. 312010005).Received Date:25 September 2015
Accepted Date:25 October 2015
Published Online:20 January 2016
Abstract:In this paper, first-principles calculations based on the density functional theory, are performed to investigate the effects of strain field on the electronic and magnetic properties of two-bilayer gallium nitride (GaN) nanosheets. The two-bilayer GaN nanosheet without surface modification forms a planar graphitic structure, whereas that with full hydrogenation for the surface Ga and N atoms adopts the energetically more favorable wurtzite structure. Surface hydrogenation is proven to be an effective way to induce a transition from indirect to direct band gap. The bare and fully-hydrogenated GaN nanosheets are nonmagnetic semiconductors. When only one-side Ga or N atoms on the surface are hydrogenated, the semihydrogenated two-bilayer GaN nanosheets will preserve their initial wurtzite structures. The two-bilayer GaN nanosheet with one-side N atoms hydrogenated transforms into a nonmagnetic metal, while that with one-side Ga atoms hydrogenated (H-GaN) is a ferromagnetic semiconductor with band gaps of 3.99 and 0.06 eV in the spin-up and spin-down states, respectively. We find that the two-bilayer H-GaN nanosheets will maintain ferromagnetic states under a strain field and the band gaps Eg in spin-up and spin-down states are a function of strain . As the tensile strain is +6%, the band gap in spin-up state reduces to 2.71 eV, and that in spin-down state increases to 0.41 eV for the two-bilayer H-GaN nanosheets. Under the compressive strain field, the two-bilayer H-GaN nanosheets will show a transition from semiconducting to half-metallici state under compression of -1%, where the spin-up state remains as a band gap insulator with band gap of 4.16 eV and the spin-down state is metallic. Then the two-bilayer H-GaN nanosheets will turn into fully-metallic properties with bands crossing the Fermi level in the spin-up and spin-down states under a compressive strain of -6%. Moreover, the value of binding energy Eb for the two-bilayer H-GaN nanosheet decreases (increases) monotonically with increasing compressive (tensile) strain. It is found that although hydrogenation on one-side Ga atoms of the two-bilayer H-GaN nanosheets is preferred to be under compressive strain, the two-bilayer H-GaN nanosheets are still the energetically favorable structures. The physical mechanisms of strain field tuning band gaps in the spin-up and spin-down states for the two-bilayer H-GaN nanosheets are mainly induced by the combined effects of through-bond and p-p direct interactions. Our results demonstrate that the predicted diverse and tunable electronic and magnetic properties may lead to the potential application of GaN nanosheets in novel electronic and spintronic nanodevices.
Keywords: GaN nanosheets/
surface modification/
strain field/
electronic and magnetic properties
