Evaluating In-Plane Thermal Expansion of Two-Dimensional Layered Materials via Effective Descriptors

Abstract

Two-dimensional layered materials show promising applications in miniaturized devices, such as transistors, spintronics, and field emitters. However, substantial thermal management issues, including thermal mismatch and thermal stress, may degrade device performance. To address such challenges, the thermal expansion (TE) anisotropy determined by the structure feature of layered material needs to be well understood. Here, we propose two new descriptors to evaluate the TE behavior of layered materials, namely the axial elastic deviation factor σ i and the axial net thermal stress f i along the ith direction. The former, defined as the normalized elastic element difference of material elastic tensor C and compliance tensor S, can distinguish whether the thermal expansion of a material is driven by phonons (with small σ i ) or elastic property (with large σ i ) with few computational costs. The latter, axial stress (in GPa/K) induced by temperature, shows an accurate determination of the positive or negative thermal expansion along different in-plane directions of layered materials. Based on the analysis of descriptors, we found that PtS2 and PtSe2 are featured with a larger axial elastic deviation factor (>23%). Considering the elastic property, we for the first time report the in-plane negative thermal expansion in PtS2 (−1.2 ppm/K) and PtSe2 (−0.8 ppm/K). Our work provides a unified understanding of TE causes of layered materials via effective descriptors, which can serve as a guideline for high-throughput screening of thermal expansion materials and subsequent device design.

Emerging Trends in Thermal Properties of Graphene

“…It can be challenging to tell FLG from By measuring the integrated Raman intensity of the G peak [4,5] or using a detector positioned beneath the graphene [32,33], one can measure the amount of heat dissipated in graphene. Since the optical absorption of graphene is wavelength dependent [1,2,34,35,36] and is influenced by strain, defects, and multiple reflections for graphene hung over trenches, it is important to quantify the optical absorption under the precise experimental circumstances. The many-body effects are responsible for the dependence of the graphene light absorption on wavelength [34,35,36].…”