Electrical and Thermal Transport in Coplanar Polycrystalline Graphene–hBN Heterostructures

• DOI: 10.1021/acs.nanolett.6b04936
• Publication Date: 2017-02-14T15:21:44Z
• Authors: José Eduardo Barr...; Bohayra Mortazavi; Aron W. Cummings; Rafael Martinez-G...; Miguel Pruneda; Luciano Colombo; Timon Rabczuk; Stephan Roche
• Keywords: [PHYS]Physics [physics]; Thermoelectrics; Chemical vapour deposition; Thermal properties; Condensed Matter - Mesoscale and Nanoscale Physics; boron nitride; chemical vapor deposition; electrical properties; grain boundary; Polycrystalline graphene; thermal properties; thermoelectrics; Bioengineering; Chemistry (all); Materials Science (all); Condensed Matter Physics; Mechanical Engineering; FOS: Physical sciences; Grain boundary; 02 engineering and technology; 7. Clean energy; [PHYS] Physics [physics]; Boron nitride; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Electrical properties; Polycrystalline graphene; Chemical vapor deposition; 0210 nano-technology

We present a theoretical study of electronic and thermal transport in polycrystalline heterostructures combining graphene (G) and hexagonal boron nitride (hBN) grains of varying size and distribution. By increasing the hBN grain density from a few percents to $100\%$, the system evolves from a good conductor to an insulator, with the mobility dropping by orders of magnitude and the sheet resistance reaching the M$��$ regime. The Seebeck coefficient is suppressed above $40\%$ mixing, while the thermal conductivity of polycrystalline hBN is found to be on the order of $30-120\,{\rm W}{\rm m}^{-1}{\rm K}^{-1}$. These results, agreeing with available experimental data, provide guidelines for tuning G-hBN properties in the context of two-dimensional materials engineering. In particular, while we proved that both electrical and thermal properties are largely affected by morphological features (like e.g. by the grain size and composition), we find in all cases that nm-sized polycrystalline G-hBN heterostructures are not good thermoelectric materials.