[Paper Review] Electron Transport Properties of Graphene-Graphyne-Graphene Transistors: First Principles Study

Young In Jhon, Myung S. Jhon|arXiv (Cornell University)|Jul 16, 2013

Graphene research and applications3 citations

TL;DR

This first-principles study investigates graphene–graphyne–graphene field-effect transistors (FETs), demonstrating robust electron transport via a lattice-matched interface between graphene and graphyne. The devices exhibit ON/OFF ratios of 10²–10³, with a minimum of 650 at a small 8.5 Å graphyne size and a transmission gap of 0.8 eV, indicating strong potential for high-performance, molecular-scale integrated circuits.

ABSTRACT

A novel nanoelectronic device is constructed by graphyne that is robustly connected between graphene electrodes, where graphyne is composed of hexagonal carbon rings and carbon chains. Owing to similarities between the bond lengths and unit cell shapes of graphene and graphyne, they have perfectly matched interfacial structure at periodic locations, enabling the facilitated charge transfer and heterostructural stability. Using a combined nonequilibrium Green's function and density functional theory formalism, we have systematically investigated the electron transport properties of graphene-graphyne-graphene field effect transistors (FETs) by varying the graphyne size and the carbon chain length. These devices exhibit excellent switching behaviors with ON/OFF ratios on the order of 10^2-10^3. The ON/OFF ratio increases as either of the graphyne size or the carbon chain length increases. Noticeably, these devices sustain good FET features even at the small graphyne size of 8.5 A, yielding ON/OFF ratio of 650 and transmission energy gap of 0.8 eV, which suggests their potential applications for fabricating highly-integrated circuits at the level comparable to molecular devices. Their boron-nitrides analogues show similar qualitative behaviors for the changes of the graphyne size and bias voltage, but they show higher ON/OFF ratios for the smaller chain length in contrast to graphyne TFTs.

Motivation & Objective

• To explore the electron transport behavior in graphene–graphyne–graphene heterostructures for nanoelectronic applications.
• To analyze the impact of graphyne size and carbon chain length on device performance.
• To evaluate the feasibility of these heterostructures as high-performance, atomically thin field-effect transistors.
• To compare the transport characteristics of carbon-based graphyne FETs with their boron-nitride analogues.

Proposed method

• Employed nonequilibrium Green's function (NEGF) formalism combined with density functional theory (DFT) for electronic structure and transport calculations.
• Modeled the graphene–graphyne–graphene heterostructure with periodic boundary conditions to ensure lattice-matched interfacial stability.
• Systematically varied the graphyne unit cell size and carbon chain length to assess their influence on conductance and switching behavior.
• Calculated transmission spectra and current-voltage (I-V) characteristics under applied gate bias to evaluate FET performance.
• Analyzed the band structure and transmission gap to understand the origin of the switching behavior.
• Compared results for carbon-based graphyne with BN-based analogues to assess material-dependent trends.

Experimental results

Research questions

• RQ1 How does the size of the graphyne unit cell affect the electron transport and switching performance in graphene–graphyne–graphene FETs?
• RQ2 What is the role of carbon chain length in modulating the ON/OFF ratio and transmission gap of these heterostructures?
• RQ3 Can a small graphyne size (e.g., 8.5 Å) still support effective field-effect transistor behavior with high performance?
• RQ4 How do the transport properties of graphyne-based FETs compare to those of their boron-nitride analogues under similar structural variations?
• RQ5 What is the intrinsic origin of the observed transmission gap and switching behavior in these 2D heterostructures?

Key findings

• The graphene–graphyne–graphene FETs exhibit ON/OFF ratios on the order of 10² to 10³, with a minimum of 650 at a graphyne size of 8.5 Å.
• The ON/OFF ratio increases with both increasing graphyne size and longer carbon chains, indicating tunable switching performance.
• A transmission energy gap of 0.8 eV is observed at the 8.5 Å graphyne size, confirming a clear bandgap for switching functionality.
• The devices maintain excellent FET characteristics even at the smallest graphyne size studied, suggesting viability for molecular-scale integration.
• BN-based analogues show similar qualitative trends but achieve higher ON/OFF ratios at shorter chain lengths compared to carbon-based graphyne FETs.
• The lattice-matched interface between graphene and graphyne enables efficient charge transfer and structural stability, supporting robust device operation.