Enhanced tunnel transport in disordered carbon superlattice structures incorporated with nitrogen

Abstract

The possibility for enhanced tunnel transport through the incorporation of nitrogen in a quasi-one dimensional superlattice structure of amorphous carbon (a−C) made of sp2−C and sp3−C rich phases is shown by using a tight-binding model. The proposed superstructure can be described by a set of disordered graphite-like carbon clusters (acting as quantum wells) separated by a thin layer of diamond-like carbon (barriers) where the variation of the width and depth of the carbon clusters significantly control the electron transmission peaks. A large structural disorder in the pure carbon system, introduced through the variation of the bond length and associated deformation potential for respective carbon phases, was found to suppress the sharp features of the transmission coefficients. A small percentage of nitrogen addition to the carbon clusters can produce a distinct transmission peak at the low energy; however, it can be practically destroyed due to increase of the level of disorder of carbon sites. Whereas pronounced resonance peaks, both for C and N sites can be achieved through controlling the arrangement of the nitrogen sites of increased concentration within the disordered sp2−C clusters. The interplay of disorder associated with N and C sites illustrated the tunable nature of resistance of the structures as well as their characteristic times.

Structurally Driven Enhancement of Resonant Tunneling and Nanomechanical Properties in Diamond-like Carbon Superlattices

“…The hopping parameter and the disorder parameter used in this work were determined through a combination of previous theoretical and experimental studies . Details can be found in our previous studies. ,, …”

“…This prompted us to study the case of bond alternation in the sp 3 -hybridized regions, which is likely to arise if polymeric chains form within the sp 3 -hybridized regions. The periodic bond alternation in the sp 3 -hybridized regions results in alternation of the hopping parameter, which varies from one site to the next, from t max σ to t min σ , which are in the range of 3.3–4.3 and 1.1–2.1 eV, respectively, with the transfer hopping parameter between the diamond-like and graphitic regions given by t σ–π , which is 1.37 eV. , There may also be significant incorporation of sp 2 C in the sp 3 -hybridized regions as well as incorporation of nitrogen complexes in the sp 3 -hybridized regions. However, the effects of these inclusions will be similar to bond alternation as they result in a much smaller potential locally in the sp 3 -hybridized regions.…”

“…Nitrogen has proven to be the best doping material for DLC to improve its electron transport and to reduce the stress. ,,, Silva et al and Schwan et al have realized a significant improvement in the conductivity with a reduction in material stress of DLC films based on the introduction of nitrogen. In terms of devices, recently Katkov and Bhattacharyya proposed a theoretical model for enhancing the tunnel transport in disordered carbon superlattice structures through the addition of nitrogen.…”

Density and localized states' impact on amorphous carbon electron transport mechanisms

“…Moreover, to calculate the I-V curves with Equation (8), one has to compute T(E) at each bias point. Therefore, we first calculated I-V characteristic curves using a reduced single-f polarized (SZP) basis set, as shown in Fig.…”

“…Some recent models [8][9][10] attempted to describe the transport phenomena of a-C at the tight-binding level of theory, considering regions of concentrated sp 3 and sp 2 atoms as barriers and wells. These models need further refinement to include the random nature of the material's atomic structure, low-dimensionality, and coupling with electrodes in very thin films, because they affect the transport mechanisms in lowdimensional structures, as observed experimentally.…”