Phonon interaction with ripples and defects in thin layered molybdenum disulfide

Abstract

Compared to other extrinsic phonon scattering mechanisms such as surface and interior defects, phonon scattering and lattice thermal resistance due to structural rippling in few-layer two-dimensional (2D) materials is under-examined. Here the temperature-dependent basalplane thermal conductivities () of one rippled and four flat molybdenum disulfide (MoS2) samples are measured with a four-probe thermal transport measurement method. A flat 18 nm thick sample and a rippled 20 nm thick sample show similar peak  values of 122±17 and 129±19 W m-1 K-1 , respectively. In comparison, a 32 nm thick flat sample has a peak  of only 58±11 W m-1 K-1 despite having increased thickness. The peak thermal conductivities of the five samples decrease with increasing integrated Raman intensity caused by defects in the frequency range of the phonon band gap in MoS2. In conjunction with the experimental findings, theoretical calculations of the temperature-, thickness-, strain-, and defect-dependent  of thin MoS2 layers reveal the importance of interior defect scattering over scattering from compression-induced ripples and surface defects in these samples. The results further clarify the conditions where ripples are important in determining the basal plane thermal resistance in layered systems.

Large Area Vertically Oriented Few-Layer MoS2 for Efficient Thermal Conduction and Optoelectronic Applications

“…The thermal conductivities of different MoS 2 nanostructures obtained via optothermal Raman study are summarized in Table . The higher thermal conductivity of our VFL-MoS 2 compared to other MoS 2 nanostructures can be attributed to the presence of minimal substrate’s strain effect and fewer defects in VFL-MoS 2 , which leads to the reduced phonon-defect scattering, as suggested in literature. − The maximum possible theoretical room temperature thermal conductivities of 673 and 841.1 W m –1 K –1 was predicted for armchair and zigzag nanoribbon, respectively, while experimentally thermal conductivities of 157 and 80 W m –1 K –1 were observed at 87 K and near room temperature, respectively, for 57 nm thick MoS 2 using four probe method . Thermally conducting VFL-MoS 2 may be used in optoelectronic devices to avoid thermal breakdown and improve the performance of such devices.…”

“…38−40 The maximum possible theoretical room temperature thermal conductivities of 673 and 841.1 W m −1 K −1 was predicted for armchair and zigzag nanoribbon, respectively, 41 while experimentally thermal conductivities of 157 and 80 W m −1 K −1 were observed at 87 K and near room temperature, respectively, for 57 nm thick MoS 2 using four probe method. 42 Thermally conducting VFL-MoS 2 may be used in optoelectronic devices to avoid thermal breakdown and improve the performance of such devices.…”

Defect-limited thermal conductivity in MoS2

“…An abundance of experimental [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and theoretical [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] investigations have examined thermal transport and its underlying vibrational properties in bulk, multilayer, and monolayer MoS2 only to raise a variety of questions, including: What is the role of defects and size in limiting thermal conductivity (k)? How do different synthesis and characterization techniques lead to quantitatively different k values in these systems?…”

“…As long mean free path phonons carry a significant portion of heat in monolayer and van der Waals (vdW) layered materials k values can be sensitive to size effects even at RT. Measured in-plane multilayer and bulk MoS2 RT k values range from 30-35 W/m-K (thin films) [15,19] to 110 W/m-K [5], while calculations range from ~80 W/m-K [31] to 390 W/m-K [34] (some anomalously low values from molecular dynamics simulations are neglected here). For monolayer MoS2 the experimental range of RT in-plane k values is 13 W/m-K [13] to 84 W/m-K [7], while the theoretical range for these is 20 W/m-K [27] to 400 W/m-K [24].…”

Synthesis and Magnon Thermal Transport Properties of Spin Ladder Sr14Cu24O41 Microstructures

“…Such a four probe method has been used to measure the  of Si nanowires, [33] black phosphorus nanolayers, [34] BAs microstructures, [35] and MoS 2 nanolayers recently. [36] The four-probe thermal transport measurement method and its prior two-probe version have been used to measure low-D micro-and nanostructures with cross section ranging from 1 nm 2 to 1 m 2 , thermal conductivity ranging between 0.1 W m -1 K -1 and 3000 W m -1 K -1 , and temperatures between 10 K and 500 K. [37][38][39] Compared to prior two-probe measurement method, this new four-probe measurement approach has allowed us to eliminate the uncertainty arising from contact thermal resistance, which is important for samples with either a large  or large diameter to length ratio. For this measurement to obtain accurate results, the thermal resistance of the suspended resistance thermometer lines needs to be designed to match the thermal resistance of the sample.…”