Computational study of a new resonant tunneling diode based on an MoS2 nanoribbon with sulfur line vacancies

摘要

Recent experimental studies have shown that sulfur vacancies in monolayer MoS2 are mobile under exposure to an electron beam and tend to accumulate as sulfur line vacancies (Komsa in Phys Rev B 88: 035301, 2013). In this work, we designed a new resonant tunneling diode (RTD) based on this natural property. Two rows of sulfur vacancies are introduced into armchair MoS2 nanoribbons (A-MoS2 NRs) to tune the nanoribbons' bandgap to obtain the doublebarrier quantum well structure of the resonant tunneling diode. This arrangement has a unique benefit that will result in very little physical distortion. A tight-binding (TB) model, with five 4d-orbitals of the Mo atom and three 3p-orbitals of the S atom, is employed for calculations. In the TB model, which is described in terms of Slater-Koster parameters, we also incorporate the changes of edge bonds. Density functional theory is used to determine all the necessary parameters of the TB model. They are obtained by an optimization procedure which achieves very fine parameter values, which can regenerate the most important energy bands of A-MoS2 NRs of different widths, with highly satisfactory precision. The introduction of these new parameters is another contribution of this work. Lastly, the nonequilibrium Green's function formalism based on the TB approximation is used to explore the properties of the new RTD structures based on A-MoS2 NRs. Negative differential resistance with peak to valley ratio (PVR) of about 78 at room temperature is achieved for one RTD, having peak current I-p = 90 nA. We show that the PVR can exceed 120 when increasing the barrier length of the RTD at the expense of lower I-p.