Strain effect on quantum conductance of graphene nanoribbons from maximally localized Wannier functions

Abstract

Density functional study of strain effects on the electronic band structure and transport properties of the graphene nanoribbons (GNR) is presented. We apply a uniaxial strain (ε) in the x (nearest-neighbor) and y (second nearest-neighbor) directions, related to the deformation of zigzag and armchair edge GNRs (AGNR and ZGNR), respectively. We calculate the quantum conductance and band structures of the GNR using the Wannier function in a strain range from −8% to +8% (minus and plus signs show compression and tensile strain). As strain increases, depending on the AGNR family type, the electrical conductivity changes from an insulator to a conductor. This is accompanied by a variation in the electron and hole effective masses. The compression ε x in ZGNR shifts some bands to below the Fermi level (E f ) and the quantum conductance does not change, but the tensile ε x causes an increase in the quantum conductance to 10e 2 /h near the E f .For transverse direction, it is very sensitive to strain and the tensile ε y causes an increase in the conductance while the compressive ε y decreases the conductance at first but increases later.

Strain effects in graphene and graphene nanoribbons: The underlying mechanism

“…It was shown that below a threshold value (which may exceed 20%, depending on direction), uniaxial strain will not open an energy gap for infinite graphene sheets, but just cause the Fermi crossing to move away from the K point [26,27,30,31]. In the case of GNRs, uniaxial strain has little influence on the band structure of zigzag GNRs (ZGNRs), while the energy gap of armchair GNRs (AGNRs) is modified in a periodic way with a zigzag pattern [21,25,29,32]. Accordingly, AGNRs and ZGNRs possess distinct charge transport properties under strain [30,[32][33][34], e.g., ZGNRs remain robust against high uniaxial strain [33].…”

“…Scanning tunneling microscopy (STM) studies on graphene have indeed revealed a correlation between local strain and tunneling conductance [20]. Theoretically, both the tight-binding (TB) model and ab initio approaches have been widely adopted to investigate the effect of strain on the band structure of graphene and graphene nanoribbons (GNRs) [14,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. It was shown that below a threshold value (which may exceed 20%, depending on direction), uniaxial strain will not open an energy gap for infinite graphene sheets, but just cause the Fermi crossing to move away from the K point [26,27,30,31].…”

Graphene Nanoribbons Under Mechanical Strain

“…[24][25][26] In contrast, theoretical studies advise a GNR could have sizable bandgap changes under uniaxial strain, [ 22 ] which could be useful for implementing graphene technology. Uniaxial strain modulates the bandgap of GNRs by shifting the Dirac point relative to the allowed wavevector lines ( k -lines) in armchair GNRs, and by modifying the magnitude of spin polarization at the edges in zigzag GNRs.…”

“…[ 22,23 ] Both ab initio calculations and tightbinding modeling show no bandgap opening for 2D graphene [+] These authors contributed equally to this work.…”

I-V characteristics of in-plane and out-of-plane strained edge-hydrogenated armchair graphene nanoribbons

“…Particularly, strain studies on graphene nanoribbons are gaining much attention as the control of their mechanical deformation could allow the creation of novel devices for energy harvesting [83][84][85][86] . There exist many reports on the electronic structure modification via strain engineering of simulated systems of different edge type, edge decoration, shape, and width [46][47][48][49][50][87][88][89][90][91][92][93][94][95][96] . Among those researchers, some outstand by including analyses of the current-voltage characteristics 43,44,92,97,98 .…”