Electronic properties of Z-shaped graphene nanoribbon under uniaxial strain A. Ahmadi Fouladi a,n , S.A. Ketabi b a Department of Physics, Sari Branch, Islamic Azad University, Sari, Iran b School of Physics, Damghan University, Damghan, Iran HIGHLIGHTS  We studied the effect of uniaxial strain on the transport properties of Z-shaped GNR.  The energy gap of armchair GNR is sensitive to the uniaxial strain.  The uniaxial strain could induce a metal-to-semiconductor transition.  The threshold voltage is sensitive to the uniaxial strain parameter strength. article info Article history: Received 24 April 2015 Received in revised form 5 July 2015 Accepted 7 August 2015 Available online 8 August 2015 Keywords: Graphene nanoribbon Uniaxial strain Noise power Green's function method abstract Based on tight-binding approximation and a generalized Green's function method, the effect of uniaxial strain on the electron transport properties of Z-shaped graphene nanoribbon (GNR) composed of an armchair GNR sandwiched between two semi-infinite metallic armchair GNR electrodes is numerically investigated. Our results show that the increase of uniaxial strain enhances the band gap and leads to a metal-to-semiconductor transition for Z-shaped GNR. Furthermore, in the Landauer–Büttiker formalism, the current–voltage characteristics, the noise power resulting from the current fluctuations and Fano factor of strained Z-shaped GNR are explored. It is found the threshold voltage for the current and the noise power increased so that with reinforcement of the uniaxial strain parameter strength, the noise power goes from the Poisson limit to sub-Poisson region at higher bias voltages. & 2015 Elsevier B.V. All rights reserved. 1. Introduction Graphene is attracting much more attention in carbon-based electronics [1,2]. It is a common knowledge that a perfect gra- phene sheet is a zero-gap semiconductor that exhibits extra- ordinarily high electron mobility and shows considerable promise for applications in electronic and optical devices. How to open the gap of graphene leads to the intensive studies on it. Depending on their widths, the armchair shaped edge ribbons can be semi- conducting (metallic) for n m 3 w = and n m n m 3 1 3 2 w w = + ( = + ) where n w is the width of the ribbon and m is an integer. First- principles calculations showed that the origin of the gaps for the armchair edge nanoribbons arises from both quantum confine- ment and the deformation caused by edge dangling bonds [3,4]. This result implies that the energy gap can be changed by de- formation. Applying mechanical force (e.g., nanoindentation) on the graphene can lead to a strain of about 10% [5]. It is found that engineering the strain on the graphene planes forming a channel can drastically change the interfacial friction of water transport through it [6]. Edge stresses and edge energies of the armchair and zigzag edges in graphene were studied by means of density functional perturbation theory [7]. The results indicated that both edges are under compression along the edge and the magnitude of compressive edge stress of armchair edge is larger than that of zigzag edge. The density-functional theory (DFT) is used to cal- culate the equilibrium shape of graphene sheets as a function of temperature and hydrogen partial pressure [8]. The results showed that the edge stress for all edge orientations is compressive. Compressive edge stresses along zigzag and armchair edges of the sheet cause out-of-plane warping to attain several degenerate mode shapes and edge stresses can lead to twisting and scrolling of nanoribbons as seen in experiments. Studying how tensile stress affects s and π bonds shows that stress affects more strongly π-bonds that can become chemically active and bind to adsorbed species more strongly [9]. A simulation study on strained armchair graphene nanoribbons (GNRs) showed those with strained wide Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physe Physica E http://dx.doi.org/10.1016/j.physe.2015.08.018 1386-9477/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: a.ahmadifouladi@iausari.ac.ir (A. Ahmadi Fouladi). Physica E 74 (2015) 475–480