Daryoosh Dideban

Germanene nanoribbon tunneling field effect transistor (GeNR-TFET) with a 10 nm channel length: analog performance, doping and temperature effects

In this paper, a scheme of the germanene nanoribbon tunneling field effect transistor (GeNR-TFET) is proposed. The characteristics and analog performance of the device were theoretically investigated by exploiting the electrical properties of a germanene nanoribbon and applying the doping concentration in the source and drain regions at 300 K and 4 K temperatures. The device parameters were obtained using a non-equilibrium Greens function (NEGF) method within the tight binding (TB) Hamiltonian. The TB Hamiltonian was extracted from the density functional theory (DFT) through the Wannier function. We find that by increasing the doping concentration the I on current increases which leads to an improvement of the I on/I off ratio to 105. Moreover, decreasing the temperature from 300 K to 4 K causes the I off to become ten times smaller. We find that the device output characteristic displays a negative differential conductance with a good peak-to-valley ratio which is improved by increasing the doping concentration. The analog performance of the device is also investigated in the subthreshold regime of operation by varying the doping concentration. It is observed that by increasing the device doping concentration, the analog figures of merit can be improved.

Investigating the mechanical properties of graphene and silicene and the fracture behavior of pristine and hydrogen functionalized silicene

In this paper, we obtain mechanical properties of monolayer graphene, bilayer graphene and silicene with the aid of molecular dynamics simulation. Thus, the reason for mechanical behavior of these materials is analyzed. For this purpose, first we perform the stress–strain analysis for each structure under tension loading and then we calculate Young’s modulus, tensile strength, and fracture strain of these structures. It is shown that tensile strength of bilayer graphene sheet of type aa is more than type ab and monolayer graphene. Moreover, it is shown that the tensile strength of silicene sheet is less than mono and bilayer graphene. We also investigate the impact of hydrogen functionalization on the mechanical properties of silicene. Hence we consider two situations of random and patterned distribution of hydrogen coating on a silicene sheet. The results indicate that the mechanical properties of the silicene are degraded as a result of functionalizing with hydrogen atoms. It is also revealed that the distribution method of hydrogen atoms affects the strength and fracture strain of hydrogen functionalized silicene.