Electric-Field Control of Spin-Polarization and Semiconductor-to-Metal Transition in Carbon-Atom-Chain Devices

Abstract

We propose hybrid molecular systems containing small carbon atomic chains interconnected by graphene-like flakes, theoretically predicted as true energy minima, as low-dimensional structures that may be useful in electronic devices at the limit of the atomic miniaturization. The effects of an external electric field applied along the direction of the carbon chains indicate that it is possible to control energy gap and spinpolarization with sufficiently high strength, within the limit of the structural restoring of the systems. In this sense, by applying electric fields with magnitudes in the 1-5 V/nm range, we obtain semiconductor-to-metallic transitions for all odd-numbered carbonchain systems proposed here. Furthermore, high-spin-to-low-spin transitions are determined for these systems as a function of the electric field magnitude. In the case of the even-numbered carbon-chain systems, the overall electric field effect is pushing electron density near the Fermi level, leading to a gapless or metallic regime at 3.0 V/nm. An electric-field control of the spin-polarization of these latter systems is only achieved by doping the extremities of the graphene-like terminations with sulfur atoms. This finding, however, is beneficial for applications of these systems in spin-controlled carbon-based devices connected by gold electrodes, even in the presence of a weak spinorbit coupling.

Close Relationships between NMR J-Coupling Alternation (JCA) and Molecular Properties of Carbon Chains

“…For example, some difficulties in obtaining optimized geometries and vibrational spectra using traditional methods (without applying stringent convergence criteria, ultrafine grids, or considering symmetry breaking) are reported in Tables S2–S4 for some linear carbon chains. Most importantly, for our purpose here, PBE has presented a rapid convergence of energy for different types of carbon chains when combined with the Pople basis sets family. , Moreover, PBE is recognized as a DFT scheme largely utilized for solid-state materials and extended systems. , …”

“…An interesting class of extended materials whose electronic properties can be assessed using NMR spectroscopy experiments is that of the one-dimensional (1D) linear carbon chains. − These 1D systems may be stabilized by choosing proper termination groups − or confining them inside multiwalled carbon nanotubes − and have been extensively studied for different purposes. , However, relationships between the molecular properties of these 1D linear carbon chains and their nuclear magnetic properties, such as SSCCs, are scarce in the literature . In part, this is due to the oscillatory dependence of the J -coupling values on nuclei pairs, hampering a direct analysis over the properties of the entire system.…”

Structural, Electronic, and Vibrational Properties of 2D Graphdiyne-Like Carbon Nanonetwork Synthesized on Au(111): Implications for the Engineering of sp-sp2 Carbon Nanostructures

“…28 An unambiguous demonstration of the power of this approach is the synthesis of atomically-precise graphene nanoribbons 29,30 (GNRs) with engineered properties. [31][32][33][34][35][36] This strategy has been recently developed to synthesize a broad range of novel carbon nanostructures based on sp-hybridization, such as carbon atom wires (CAWs) and 2D extended networks of mixed sp-sp 2 -hybridization. While the fabrication of sp 2 carbon systems is achieved through on-surface Ullman coupling reaction of aryl halides, an efficient strategy for sp carbon nanostructures is represented by on-surface dehalogenative/dehydrogenative homocoupling reaction of precursors functionalized with alkynyl halides.…”

Restoring Observed Classical Behavior of the Carbon Nanotube Field Emission Enhancement Factor from the Electronic Structure

“…To solve the Kohn−Sham equations, we adopt the PBE exchange− correlation potential, 27 which has performed well for carbon structures in applied fields. 28 Figure 1a−c shows the optimized 3D VAGCNTs. These behave as carbon nanoprotrusions (CNPs) formed by capped (6,6) single-walled CNTs (SWCNTs), with different heights relative to the 2D graphene sheet.…”

“…The carbon atoms [of the unit cells] are described in terms of norm-conserving pseudopotentials and double-ζ basis sets, including polarization functions, with energy cutoff of 300 Ry, sampling the Γ point of the Brillouin-zone. To solve the Kohn–Sham equations, we adopt the PBE exchange–correlation potential, which has performed well for carbon structures in applied fields …”