[Paper Review] Interface of graphene nanopore and hexagonal boron nitride as a sensing device

Fábio A. L. de Souza, Wanderlã L. Scopel+2 more|arXiv (Cornell University)|Feb 23, 2016

Graphene research and applications39 references19 citations

TL;DR

This paper proposes a graphene/hexagonal boron nitride (h-BN) heterostructure with a nanopore as a highly sensitive nanosensor for detecting molecules or DNA sequences via real-time conductance modulation. Using DFT and non-equilibrium Green's function methods, it shows that current becomes confined to a one-atom-wide carbon chain at the h-BN interface when a nanopore is created, enabling selective electronic sensing with enhanced control over current pathways.

ABSTRACT

The atomically-precise controlled synthesis of graphene stripes embedded in hexagonal boron nitride opens up new possibilities for the construction of nanodevices with applications in sensing. Here, we explore properties related to electronic structure and quantum transport of a graphene nanoroad embedded in hexagonal boron nitride, using a combination of density functional theory and the non-equilibrium Green's functions method to calculate the electric conductance. We find that the graphene nanoribbon signature is preserved in the transmission spectra and that the local current is mainly confined to the graphene domain. When a properly sized nanopore is created in the graphene part of the system, the electronic current becomes restricted to a carbon chain running along the border with hexagonal boron nitride. This circumstance could allow the hypothetical nanodevice to become highly sensitive to the electronic nature of molecules passing through the nanopore, thus opening up ways for the detection of gas molecules, amino acids, or even DNA sequences based on a measurement of the real-time conductance modulation in the graphene nanoroad.

Motivation & Objective

• To design a novel 2D nanosensor using a graphene nanoribbon embedded in h-BN with a controlled nanopore.
• To investigate how electronic transport and current localization are affected by the presence of a nanopore in the graphene region.
• To explore the potential of this hybrid system for sensing applications, including gas detection and DNA sequencing.
• To determine whether current can be confined to a single-atom carbon chain at the graphene-h-BN interface, enabling high-sensitivity detection.
• To evaluate the feasibility of using electrochemical pore creation to tailor the nanopore position near the C-N interface for optimal sensing performance.

Proposed method

• Density Functional Theory (DFT) with GGA-PBE exchange-correlation functional was used to model the electronic structure of the hybrid graphene/h-BN system.
• Non-equilibrium Green's function (NEGF) formalism was applied to calculate quantum transport properties and electric conductance.
• The system was modeled with variable widths of graphene (w) and h-BN (v), and the bandgap dependence on width was analyzed.
• Transmission spectra and local current density were computed to identify current pathways under different bias conditions.
• Wavefunction localization analysis was performed to determine the spatial origin of electronic states contributing to conductance peaks.
• The nanopore was simulated by removing carbon atoms at the graphene edge adjacent to the h-BN interface, mimicking electrochemical pore formation.

Experimental results

Research questions

• RQ1 How does the width of the graphene nanoribbon affect the bandgap and electronic transport in the graphene/h-BN heterostructure?
• RQ2 What happens to the current path when a nanopore is introduced in the graphene region of the heterostructure?
• RQ3 Can the electronic current be confined to a one-atom-wide carbon chain along the h-BN interface due to the nanopore?
• RQ4 How does the transmission spectrum change in the presence of a nanopore, particularly near the Fermi level?
• RQ5 Can this system function as a sensitive sensor for translocating biomolecules through conductance modulation?

Key findings

• The bandgap of the graphene nanoribbon decreases with increasing width, leading to a semiconductor-to-zero-gap-semiconductor transition.
• In the pristine system, current can flow through both the center and edges of the graphene nanoribbon, depending on the energy window.
• After nanopore creation, the current is strongly confined to a one-atom-wide carbon chain at the C-N interface, with minimal contribution from the C-B side.
• Transmission is suppressed to zero in the energy range from |1.25| to |0.25| eV due to the nanopore, indicating strong electronic blockade.
• At specific energies (e.g., -0.1 eV and -0.5 eV), the current flows predominantly along the interface atoms, with wavefunctions localized near the C-N and C-B bonds respectively.
• The system exhibits two distinct conductance plateaus: T = 2G₀ at the central plateau (dominated by interface atoms) and T = 1G₀ at the central region (dominated by bulk graphene atoms).