Negative Differential Resistance and Steep Switching in Chevron Graphene Nanoribbon Field-Effect Transistors

Abstract

Ballistic quantum transport calculations based on the non-equilbrium Green's function formalism show that field-effect transistor devices made from chevron-type graphene nanoribbons (CGNRs) could exhibit negative differential resistance with peak-to-valley ratios in excess of 4800 at room temperature as well as steepslope switching with 6 mV/decade subtheshold swing over five orders of magnitude and ON-currents of 88 µA µm −1 . This is enabled by the superlattice-like structure of these ribbons that have large periodic unit cells with regions of different effective bandgap, resulting in minibands and gaps in the density of states above the conduction band edge. The CGNR ribbon used in our proposed device has been previously fabricated with bottom-up chemical synthesis techniques and could be incorporated into an experimentally-realizable structure.In 1970, L.Esaki and R. Tsu predicted 1 that in an appropriately made superlattice, it should be possible to obtain very narrow width bands, which could then lead to negative differential resistance. The remarkable property of these superlattices is in the fact that, unlike the Esaki diodes, this negative differential resistance does not need any tunneling, rather it comes from the direct conduction of electrons. Nonetheless, significant difficulty in synthesizing atomically precise, eptiaxial heterostructures has made it very challenging to realize such superlattice structures 2-8 . Much work has been done on modeling graphene nanoribbon heterostructures and superlattices which could exhibit NDR 9-15 . Other work has been done on steep slope devices based on GNR and CNT heterojunctions 16,17 . Gnani et al. showed how superlattices could be used in a III-V nanowire FET to achieve steep slope behavior by using the superlattice gap to filter high energy electrons in the OFF state 18 . Here, we show that the recently synthesized chevron nanoribbons 19 provides a natural, monolithic material system where narrow-width energy bands and negative differential resistance (NDR) can be achieved. Our atomistic calculations predict that the NDR behavior should manifest at room temperature along with sub-thermal steepness (<60 mV/decade at room temperature). Such NDR behavior could lead to completely novel devices for next generation electronics.Unlike a graphene sheet, a narrow strip etched out of graphene, often called a graphene nanoribbon (GNR), can provide a sizeable bandgap. As a result, GNRs could lead to devices with good ON/OFF ratio at the nanoscale. However, a number of studies have also shown the deleterious effect of edge roughness on the device performance 20,21 . Recent breakthroughs in bottom-up chemical synthesis can produce GNRs with atomistically pristine edge states and overcome this shortcoming 19 . In fact, a recent experimental work demonstrated working transistors with 9-and 13-AGNRs made with these techniques 22 . The methods used to synthesize these ribbons can also be used to generate complex periodic structures beyond simply armchair and zigzag nanoribbon...

Pseudo-atomic orbital behavior in graphene nanoribbons with four-membered rings

“…Early research largely focused on the potential role of GNRs in field-effect transistors (3,4), revolving around tailoring the size of their bandgap through width, edge, and heteroatom engineering (2,(5)(6)(7), as well as the formation of heterojunctions through copolymerization (5,8). Recently, the design of ever more intricate GNR structures has opened new avenues of exploration, including topics such as negative differential resistance (9)(10)(11)(12), spintronics (13,14), magnetism (15)(16)(17)(18)(19)(20), and quantum information processing (21)(22)(23).…”

Quantum transport in zigzag graphene nanoribbon decorated with a phenanthrene molecule

“…As early as 1974, Aviram and Ratner firstly designed a rectifier based on a single organic molecule [1], then the era of molecular devices was coming. Many important breakthroughs have been achieved in molecular devices already [2][3][4][5][6][7][8]. By means of external electric field, deformations of the molecular and light incident, many intriguing properties have been acquired in the past years [9][10][11], such as negative differential resistance (NDR) [12][13][14][15][16][17][18][19][20][21], molecular rectification [1,[22][23][24][25], molecular switch [17,[26][27][28], and conductance enhancement [29][30].…”

Charge Transport Mechanism in Chevron-Graphene Nanoribbons

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