Thermal transport and energy dissipation in two-dimensional Bi2O2Se

Abstract

Thermal transport and energy dissipation are important for a material in both thermoelectric and electronic devices. Here, we investigate the lateral and interfacial thermal transport of two-dimensional (2D) Bi2O2Se by Raman spectroscopy. It is found that thin Bi2O2Se flakes have a low in-plane thermal conductivity while maintaining an appropriate interfacial thermal conductance. The in-plane thermal conductivity of Bi2O2Se decreases with decreasing thickness, to as low as 0.92 ± 0.18 W⋅m−1⋅K−1 at a thickness of ∼8 nm. Such a low thermal conductivity is derived from the low phonon group velocity, strong anharmonicity, and large surface scattering of acoustic phonons of the Bi2O2Se thin layer. Simultaneously, thinner Bi2O2Se presents a higher thermal dissipation to the substrate than the thicker counterparts in the device. The interfacial thermal conductance increases with decreasing thickness, and reaches ∼21 MW⋅m−2⋅K−1 at ∼8 nm. These results provide critical information for the design of thermoelectric devices with high figures of merit and electronics with low-power consumption based on 2D materials.

Gate‐Tunable Polar Optical Phonon to Piezoelectric Scattering in Few‐Layer Bi2O2Se for High‐Performance Thermoelectrics

“…[21][22][23][24] In addition, the ferroelectric soft phonon modes and weak bonding facilitate extremely low thermal conductivity in 2D Bi 2 O 2 Se. [21,25] These render Bi 2 O 2 Se the capability to effectively engineer the scattering mechanism, upon which the independent modulation of PF via carrier mobility makes Bi 2 O 2 Se a promising TE material.…”

Progress Report on Property, Preparation, and Application of Bi2O2Se

“…As we have mentioned previously, the band structure, thermal transport, and optical absorption of Bi 2 O 2 Se all display a typical feature of layer-dependence, [10,21,29] so it would be feasible to tune these properties through modulation of thickness. Defects in Bi 2 O 2 Se can be induced by synthetic control, such as changing the ratios of raw materials, [36] and shear exfoliation.…”

“…[ 10,27,28 ] Bi 2 O 2 Se shows strong anisotropy in crystal structure along with electronic, mechanical, thermal, and optical properties. [ 17a,c,29 ] For instance, the carrier mobility along a ‐direction is larger than that along c ‐direction at the measured temperature range of 2–300 K. [ 17c ] Thermal transport in Bi 2 O 2 Se is thickness‐dependent, but the in‐plane and interfacial thermal conductivity show opposite tendencies as layer number changes. [ 29 ] According to first‐principle calculations, Bi 2 O 2 Se has good mechanical properties, and its monolayer structure possesses a moderate elastic constant, which is smaller than that of graphene, but competitive with monolayer BP.…”

Nonvolatile Memory and Artificial Synaptic Characteristics in Thin‐Film Transistors with Atomic Layer Deposited HfOx Gate Insulator and ZnO Channel Layer

“…[ 4–10 ] Besides two‐terminal memristors, a variety of three‐terminal or four‐terminal artificial synapses, called synaptic transistors, have been investigated because the drain current changes by gate biasing corresponds to the synaptic weight modulation. [ 11–20 ] Thanks to multi‐terminal configuration, the synaptic transistors enable to update synaptic weight by gate biasing during performing signal processing by drain biasing. In addition, the wide range of drain current with respect to gate and drain voltages provides substantial change of synaptic weight for reliable training operation.…”

“…In addition, the wide range of drain current with respect to gate and drain voltages provides substantial change of synaptic weight for reliable training operation. Until now, proposed synaptic transistors have employed various operation schemes such as electrical charging of floating‐gate or interface states, [ 11,12 ] tunable polarizations in gate insulator, [ 13,14 ] exchange of protons between oxide‐semiconductor channel and gate insulator, [ 15,16 ] exchange of Li ions between lithium electrolyte gate insulator and oxide channel layer, [ 17,18 ] and oxygen ionic redistribution between oxygen‐deficient gate insulator and oxide‐semiconductor channel. [ 19,20 ]…”