Quantifying anisotropic thermal transport in two-dimensional perovskite (PEA2PbI4) through cross-sectional scanning thermal microscopy

Abstract

In this paper, we investigated the anisotropic thermal transport in two-dimensional (2D) perovskite (phenethylammonium lead iodide) nanolayers through a measurement technique called cross-sectional scanning thermal microscopy. In this method, a target perovskite layer on a substrate was oblique polished with an Ar ion beam to create a low-angle wedge with nanoscale roughness that is followed by high-vacuum scanning thermal microscopy to obtain the thermal conductance map as a function of local thickness. The experimentally obtained data were processed with an analytical model and validated by the finite elemental analysis simulation to quantify the in-plane $({k}_{l,xy})$ and cross-plane thermal conductivities $({k}_{l,z})$ of the 2D perovskite from a single set of measurements with nanoscale resolution. We obtained ultralow thermal conductivity $({k}_{l}=0.25\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1})$ for the 2D perovskite along with an anisotropy $({k}_{l,\phantom{\rule{0.16em}{0ex}}xy}=0.45\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}\mathrm{and}\phantom{\rule{0.16em}{0ex}}{k}_{l,\phantom{\rule{0.16em}{0ex}}z}=0.13\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1})$ linked to the unique structure of the perovskite and different phonon lifetimes and group velocities for in-plane and out-of-plane directions. The results that are available are essential for the thermal management of 2D perovskite-based optoelectronic devices and potential thermoelectric applications of these materials.