The role of atomic vacancies and boundary conditions on ballistic thermal transport in graphene nanoribbons

Abstract

Quantum thermal transport in armchair and zig-zag graphene nanoribbons are investigated in the presence of single atomic vacancies and subject to different boundary conditions. We start with a full comparison of the phonon polarizations and energy dispersions as given by a fifth-nearest-neighbor force-constant model (5NNFCM) and by elasticity theory of continuum membranes (ETCM). For free-edges ribbons we discuss the behavior of an additional acoustic edge-localized flexural mode, known as fourth acoustic branch (4ZA), which has a small gap when it is obtained by the 5NNFCM. Then, we show that ribbons with supported-edges have a sample-size dependent energy gap in the phonon spectrum which is particularly large for in-plane modes. Irrespective to the calculation method and the boundary condition, the dependence of the energy gap for the low-energy optical phonon modes against the ribbon width W is found to be proportional to 1/W for in-plane, and 1/W${}^2$ for out-of-plane phonon modes. Using the 5NNFCM, the ballistic thermal conductance and its contributions from every single phonon mode are then obtained by the non equilibrium Green's function technique. We found that, while edge and central localized single atomic vacancies do not affect the low-energy transmission function of in-plane phonon modes, they reduce considerably the contributions of the flexural modes. On the other hand, in-plane modes contributions are strongly dependent on the boundary conditions and at low temperatures can be highly reduced in supported-edges samples. These findings could open a route to engineer graphene based devices where it is possible to discriminate the relative contribution of polarized phonons and to tune the thermal transport on the nanoscale.

References in corpus (21)

• Electric Field Effect in Atomically Thin Carbon Films
• Experimental Observation of Quantum Hall Effect and Berry's Phase in Graphene
• Universal Dynamic Conductivity and Quantized Visible Opacity of Suspended Graphene
• Thermal Properties of Graphene, Carbon Nanotubes and Nanostructured Carbon Materials
• Graphene -- Based Nanocomposites as Highly Efficient Thermal Interface Materials
• Thermal Properties of Isotopically Engineered Graphene
• Length-dependent thermal conductivity in suspended single-layer graphene
• Graphene-Graphite Quilts for Thermal Management of High-Power GaN Transistors
• The phonon dispersion of graphite by inelastic x-ray scattering
• Thermal Properties of the Hybrid Graphene-Metal Nano-Micro-Composites: Applications in Thermal Interface Materials
• Phonon Transport in Graphene
• Ballistic to diffusive crossover of heat flow in graphene ribbons
• Anomalous Size Dependence of the Thermal Conductivity of Graphene Ribbons
• Nonequilibrium Green's function method for quantum thermal transport
• Tuning the thermal conductivity of graphene nanoribbons by edge passivation and isotope engineering: a molecular dynamics study
• Effect of Grain Boundaries on Thermal Transport in Graphene
• Vibrational properties of graphene nanoribbons by first-principles calculations
• First principle study of the thermal conductance in graphene nanoribbon with vacancy and substitutional silicon defect
• Acoustic phonons and spin relaxation in graphene nanoribbons
• Single-mode phonon transmission in symmetry broken carbon nanotubes
• Bending mode fluctuations and structural stability of graphene nanoribbons

Cited by in corpus (5)

• Theory of anharmonic phonons in 2D crystals
• Low-dimensional phonon transport effects in ultra-narrow, disordered graphene nanoribbons
• Steady-state ballistic thermal transport associated with transversal motions in a damped graphene lattice subjected to a point heat source
• Tuning the polarized quantum phonon transmission in graphene nanoribbons
• Transport through graphene nanoribbons: suppression of transverse quantization by symmetry breaking