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In this work, we theoretically investigate the material and transport properties of strained chevron graphene nanoribbons (CGNRs) which can be easily synthesized by the bottom-up fabrication technology. Because of the unique atomic structures, the energy and pressure of the CGNRs vary asymmetrically along compressive and tensile strains. Under the two strain directions, the CGNRs' bandgaps and carrier effective masses in the conduction band minimum and the valence band maximum are all reduced. The transport properties are promoted accordingly, except some negative differential conductance behaviors caused by energy state localizations. When the tensile strains exceed a criterion value, the C–C bonds in the inner sides of the CGNR corners will be broken in sequence. Meanwhile, the CGNRs can restore their initial unstrained states rapidly when the strains are removed. However, if the broken bonds are saturated by foreign atoms, such as H, a novel kind of stable carbon structure will be obtained. The investigations suggest possible applications of strain engineered CGNRs in transport devices. [ABSTRACT FROM AUTHOR]

The 2-D materials possess application perspective in semiconductor logic devices owing to their bonding free surface carrier transport. However, the scaling transistor width-induced edge issues have significantly limited their surface transport within the lateral direction, leading to effective mass increasing, and bandgap fluctuations. Therefore, it is important to find a novel 2-D material with both excellent surface transport and immunity to edge effect. In this paper, inspired by the recently discovered tellurene and its unique Te-Te bonds, the edge effect on the transport characteristics of tellurene is studied theoretically in the form of tellurene nanoribbons (TNRs). Among the four edge types, three of them exhibit semiconducting characteristic owing to the unique bonding property of Te. Simulation results demonstrate that the tetragonal edges (TEs) in zigzag TNRs (ZTNRs) almost have no influence on surface transport, resulting in minimized bandgap and effective mass variations, compared to that of graphene nanoribbons, and Si and Ge nanowires. Transport behaviors of the TE-ZTNRs are investigated using a metal–oxide–semiconductor transistor model and a multiscale simulation flow, with the calculated current densities exceeding $\textsf {1}$ mA/ $\mu \text{m}$ and the on–off ratios over $10^{\textsf {11}}$. Based on the results, an explicit prediction that the TE-ZTNRs are competitive candidates for nanoscale transistor materials is proposed. [ABSTRACT FROM AUTHOR]

In this paper, segmented edge saturation (SES) is proposed as a novel method to design high-performance tunnel FETs (TFETs) using smooth graphene nanoribbon (GNR). When the edges of a smooth GNR are saturated by different elements in its different segments, the energy gaps ( Eg) of these segments can be tuned. Therefore, the tunneling and blocking effects are achieved simultaneously by reducing and enlarging the Eg of GNR in its specific regions. Both high on-to-off current ( I \mathrm{\scriptscriptstyle ON}/I \mathrm{\scriptscriptstyle OFF}) ratio and large I \mathrm{\scriptscriptstyle ON} are obtained. Simulation results show that the \mathrm I \mathrm{\scriptscriptstyle OFF} of the SES GNR TFET is below 1 \times 10^-4 ~\mu \textA/\mu \textm and the I{ \mathrm{\scriptscriptstyle ON}} reaches 2000 \mu \textA/\mu \textm at 0.4-V supply voltage. Detailed transport mechanisms of this TFET are investigated in comparisons with its uniform saturation counterparts. Dynamic performance and scaling ability analyzes are also carried out. The largest intrinsic delay and switching energy are only 0.17 ps and 0.09 fJ/ \mu \textm . Meanwhile, it can maintain high I{ \mathrm{\scriptscriptstyle ON}}/I \mathrm{\scriptscriptstyle OFF} ratios when the channel length is scaled down to several nanometers. The discussions on GNR edge roughness suggest that the roughness should be avoided for better I \mathrm{\scriptscriptstyle ON} behaviors. The good performance of the TFET highlights the capabilities of SES in the developments of GNR tunnel devices. [ABSTRACT FROM AUTHOR]

Tight-binding (TB) Hamiltonian is widely used in the simulations of many low-dimensional devices, such as graphene nanoribbon (GNR)-based FETs, and usually, it is an empirical parameterized matrix. In this paper, we propose a novel strategy to construct the edge TB parameters of armchair GNR (a-GNR) under different edge saturations. Different from the traditional way’s only edge bonds analysis, this method also considers the diversity of three a-GNR families and the saturation atoms impact on the subedge bonds. The effects of several common elements or groups on the edge of GNRs are studied numerically and among them, hydrogen (H), fluorine (F), and hydroxyl group (OH) show better saturation properties. Through elaborate verifications of these three types of saturations, the TB fitting errors of the proposed new strategy are drastically reduced, in comparison with the traditional parameters. These verifications, which are subjected to the ab initio results, go from an energy-band level to a device-performance level. Simulation results also show that saturated by different atoms, the band structure of GNR obviously varies. Thus, edge saturation can be another effective method of tuning GNR device properties, such as bandgap, current on/off ratio, and carrier mobility. [ABSTRACT FROM AUTHOR]

In this letter, a tunnel FET (TFET) combining both graphene nanoribbon (GNR) heterojunction (HJ) and gate work function (WF) engineering is studied with the numerical simulation. The lowest subthreshold swing is smaller than 15 mV/decade and the ON state current ( $I_{{\mathrm{\scriptscriptstyle ON}}} ) reaches to 1.7~\mu \textA with device width smaller than 3 nm. The tunnel width is well reduced with the dual-material gate (DMG) structure boosting the ON current. The channel with a wide energy gap ( Eg ) GNR can effectively reduce the leakage current at OFF state when its length is 13 nm. It is found out that large WF difference between the gate and the GNR not only effectively enhances the tunneling effect but also leads to an electron quantum well hindering the regulation capability of the gate. This effect can be well reduced with large WF gate material on the top of the HJ region. The numerical simulation reveals that the GNR HJ-DMG TFET is a good candidate for low power applications. [ABSTRACT FROM PUBLISHER]

A detailed simulation study of the graphene antidot nanoribbon (GANR) and its corresponding MOSFET characteristics is shown in this paper. The research uncovers that the GANR's energy gap ( E g ) is continuously tunable by its topography parameters, such as the ribbon's width, the antidot density and the antidot size. At the same ribbon width, the E g of GANR can be tuned flexibly, while it is only a fixed value in GNR. Owing to these flexible E g regulations, device applications based on GANRs could be more widely used. Furthermore, brief compact descriptions are extracted between GANR's band gap and MOSFET's device characteristics. Using E g as a bridge, the relations between the structure characteristics and transport properties of GANR MOSFETs are constructed directly. The results reveal that the antidot nanoribbon structure is a good candidate for MOSFET applications. In the calculation, an elaborate ab initio-based study framework from band structure to device performance is adopted. Using the maximally localized Wannier functions (MLWF) method, the impacts on band structures, which are induced by crystal optimizations, are reserved into the TB Hamiltonian without any parameter revisions. This method overcomes the gap between nano-scale carbon structures' material characteristics and their device applications. [ABSTRACT FROM AUTHOR]