Growth Optimization and Device Integration of Narrow‐Bandgap Graphene Nanoribbons

Abstract

The electronic, optical, and magnetic properties of graphene nanoribbons (GNRs) can be engineered by controlling their edge structure and width with atomic precision through bottom‐up fabrication based on molecular precursors. This approach offers a unique platform for all‐carbon electronic devices but requires careful optimization of the growth conditions to match structural requirements for successful device integration, with GNR length being the most critical parameter. In this work, the growth, characterization, and device integration of 5‐atom wide armchair GNRs (5‐AGNRs) are studied, which are expected to have an optimal bandgap as active material in switching devices. 5‐AGNRs are obtained via on‐surface synthesis under ultrahigh vacuum conditions from Br‐ and I‐substituted precursors. It is shown that the use of I‐substituted precursors and the optimization of the initial precursor coverage quintupled the average 5‐AGNR length. This significant length increase allowed the integration of 5‐AGNRs into devices and the realization of the first field‐effect transistor based on narrow bandgap AGNRs that shows switching behavior at room temperature. The study highlights that the optimized growth protocols can successfully bridge between the sub‐nanometer scale, where atomic precision is needed to control the electronic properties, and the scale of tens of nanometers relevant for successful device integration of GNRs.

Remote-Triggered Domino-like Cyclodehydrogenation in Second-Layer Topological Graphene Nanoribbons

“…Atomically precise graphene nanoribbons (GNRs) − can exhibit a nontrivial topology with emerging in-gap boundary states that host spins protected by chiral symmetry, − which offer desired platforms for exploring the quantum spin physics and nonlocal spin entanglement for applications of spintronics and quantum information science (QIS). − The recent development of on-surface synthesis has achieved robust topologically protected spin states at the GNR termini − and frontier topological bands formed by the array of interface states in the GNR backbones consisting of segments with different values of the topological invariant Z 2 . , Usually, sub-monolayer or nearly monolayer GNRs are obtained even though the second-layer polymers can form, where the cyclodehydrogenation/graphitization can be greatly inhibited due to the suppressed catalytic activity of the metal substrate. − However, for these GNRs directly adsorbed on metallic substrates, the strong screening and Fermi level pinning effects can not only alter the designer bulk electronic band structures but also let the end spin states become either quenched or highly untunable with external gates. ,, Previously, the decoupled topological end states and the associated magnetism had been probed through the bottom-up synthesis of GNRs with an ultralow coverage on the insulating substrate or by case-specific tip-assisted manipulation using a scanning tunneling microscope (STM) ,,, while these approaches suffer from low efficiency. A direct synthesis of multilayer GNRs could naturally offer an effective route to uncovering the nearly intrinsic topological states in the second-layer GNRs where the inert first layer acts as a self-decoupling layer.…”

Two-Component GW Calculations: Cubic Scaling Implementation and Comparison of Vertex-Corrected and Partially Self-Consistent GW Variants

“…Due to its favorable price-to-performance ratio, the GW approximation (GWA) , ( G : single-particle Green’s function, W : screened electron–electron interaction) is one of the most popular methods for the calculation of charged excitations in finite systems. , Over the last decade, the GWA has been implemented into a large number of electronic structure codes − and GW implementations for massively parallel architectures, ,− low-order scaling implementations, ,,,, effectively linear scaling stochastic formulations, , fragment-based approaches, − or embedding techniques − have enabled applications of the GW method to large biomolecules, , nanostructures, ,, or interfaces …”

“…Due to its favorable price-to-performance ratio, the GW approximation (GWA) 1,2 (G: single-particle Green's function, W: screened electron−electron interaction) is one of the most popular methods for the calculation of charged excitations in finite systems. 3,4 Over the last decade, the GWA has been implemented into a large number of electronic structure codes 5−20 and GW implementations for massively parallel architectures, 17,21−24 low-order scaling implementations, 15,16,18,19,25 effectively linear scaling stochastic formulations, 26,27 fragment-based approaches, 28−31 or embedding techniques 32−34 have enabled applications of the GW method to large biomolecules, 16,35 nanostructures, 24,31,36 or interfaces. 24 A large number of studies have by now contributed to a thorough understanding of the impact of technical aspects of these implementations, like the choice of single-particle basis, pseudopotential (PP) approximations, or frequency treat-ment, 16,37−41 as well as the performance of various GW approaches for the first ionization potentials (IP) and electron affinities (EA) of weakly correlated organic molecules.…”

Photoresponse of Solution-Synthesized Graphene Nanoribbon Heterojunctions on Diamond Indicating Phototunable Photodiode Polarity

“…Research into atomically precise graphene nanoribbons (GNRs) is approaching atom-by-atom tailoring of advanced electronic properties. − Today, GNRs can be fabricated with different widths, heteroatom doping, shape, edge structure, − and functionalization, which greatly affect their bandgaps. , Moreover, the combination of GNRs with different widths allows the formation of graphene nanoribbon heterostructures (GNRHs) such as type-II heterojunctions, , featuring staggered gaps, thereby epitomizing sophisticated bottom-up fabrication of organic device elements. − An exciting research frontier in GNRHs is the light-induced quantum control of the heterojunction, dictating charge-transfer, emission, magnetism, and advanced optical effects. , …”