Thickness dependent anisotropy of in-plane Raman modes under different temperatures in supported few-layer WTe2

Chen, Yangbo; Deng, Chuyun; Wei, Yuehua; Liu, Jinxin; Su, Yue; Xie, Siyi; Cai, Weiwei; Peng, Gang; Huang, Han; Dai, Mengyan; Zheng, Xiaoming; Zhang, Xueao

doi:10.1063/5.0058438

Cited by 10 publications

(6 citation statements)

References 48 publications

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“…The excitation wavelength dependent anisotropic χ for both A g 1 and A g 2 phonons of both b-As flakes are summarized in Table 3 (see Supporting Information section 4 for details). The larger absolute values of χ ZZ than χ AC might be attributed to the corresponding higher phonons group velocities in the ZZ direction, 20,44 The smaller absolute values of χ b-As than χ BP 45−47 can be attributed to the larger mass of arsenic atom induced lower phonon frequency and group velocities. The results are consistent with the reported higher thermal conductivity in the ZZ direction and lower thermal conductivity of b-As than BP.…”

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confidence: 99%

In-Plane Phonon Anisotropy and Anharmonicity in Exfoliated Natural Black Arsenic

Wang

Chen

Guo

et al. 2021

J. Phys. Chem. Lett.

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Group-VA two-dimensional layered materials in a puckered honeycomb structure exhibit strong in-plane anisotropy and have emerged as new platforms for novel devices. Here, we report on systematic Raman investigations on exfoliated b-As flakes on the A g 1 and A g 2 polarization dependence on their symmetry, excitation wavelength, and flake thickness. The intensity maximums of both phonons are corrected in the b-As armchair direction under 633 nm excitation regardless of the flake thickness upon considering optical birefringence effects and interference effects. The intensity ratio of A g 1 to A g 2 modes under 532 nm excitation is useful for b-As crystalline orientation identification. Temperature-dependent Raman investigations reveal the linearly anharmonic behaviors of both phonons in the range from 173 to 293 K and a slightly greater first-order temperature coefficient in the zigzag direction. Our findings give deep insight into the in-plane phonon anisotropy and anharmonicity of b-As and provide a step toward future device applications.L ayered crystalline materials such as graphene, transition metal dichalcogenides (TMDCs), and black phosphorus (BP) have attracted tremendous interest owing to their high carrier mobility, large specific surface area, and thicknessdependent physical properties, 1−3 etc. Monoelemental group-VA (P, As, Sb, Bi) layered materials in a puckered honeycomb structure exhibit strong in-plane anisotropy and have emerged in recent years as new platforms for novel electrical and optical devices. 4−10 Among them, BP has been extensively investigated to show the layer-dependent optical direct band gap, 11 carrier mobility over 10 4 cm 2 V −1 s −1 , 12 anisotropies, 6,13 and abnormal polarized Raman scattering. 13 However, BP flakes are easily degraded in ambient conditions.Arsenic sits just below phosphorus in the periodic table. There mainly exist three arsenic allotropes: gray, orthorhombic, and yellow arsenic. The orthorhombic arsenic has been found in natural arsenolamprite (Copiapo area, northern Chile) 14 and is black and has a metallic luster, as shown in the optical image in Figure 1a, suggesting its high air stability. It is also named black arsenic (b-As). The high quality and atomic structure of such natural b-As crystals have been proven in previous reports. 15−18 Similar to BP, each arsenic atom in b-As is covalently bonded with three other adjacent ones to form a puckered honeycomb structure (as shown in the top and side views in Figure 1b). In-plane band a-axes correspond to the armchair (AC) and zigzag (ZZ) directions, respectively. The out-of-plane van der Waals (vdW) stacking direction is the caxis. In contrast to BP, monolayer b-As is an indirect band gap semiconductor. The carrier mobility and band gap of b-As are

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confidence: 99%

In-Plane Phonon Anisotropy and Anharmonicity in Exfoliated Natural Black Arsenic

Wang

Chen

Guo

et al. 2021

J. Phys. Chem. Lett.

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“…It can be clearly seen that all three peaks show red-shift with the temperature going up, which is similar to experimental results from TMDs. [35][36][37] This shift is usually caused by electron-phonon, anharmonic phonon-phonon interaction and thermal expansion. [38,39] Raman shift (cm ) Temperature (K) The temperature-dependent FWHM of A 1 g , A 2 g , and A 3 g modes for the Raman peaks of 2D VOCl.…”

Section: Temperature-dependent Raman Spectramentioning

confidence: 99%

In-plane optical anisotropy of two-dimensional VOCl single crystal with weak interlayer interaction

Wang¹,

Cui²,

Zhu³

et al. 2022

Chinese Phys. B

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MOX (M = Fe, Cr, V; O = oxygen, X = F, Cl, Br, I), an emerging type of two-dimensional (2D) van der Waals materials, have been both theoretically and experimentally demonstrated to possess unique electronic and magnetic properties. However, the intrinsic in-plane anisotropic properties of 2D VOCl still lacks in-depth research, especially optical anisotropy. Herein, a systematic Raman spectroscopic study is performed on VOCl single-crystal with different incident laser polarization at various temperatures. The polarized-dependent Raman scattering spectra reveal that the A g mode of VOCl show a 2-lobed shape in parallel polarization configuration while a 4-lobed shape in vertical configuration. In addition, the temperature-dependent and thickness-dependent Raman scattering spectra confirm a relatively weak van der Waals interaction between each layers among VOCl single crystal. These findings might provide better understanding on the in-plane anisotropic phenomenon in VOCl layers, thus will accelate further application of 2D single crystals for nanoscale angle-dependent optoelectronics.

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“…Low-symmetry materials exhibit anisotropic thermal [ 1 , 2 , 3 , 4 ], electrical [ 5 , 6 , 7 , 8 ], optical [ 5 ], optoelectronic [ 9 ], and thermoelectric [ 10 ] properties along different lattice orientations, which provides a brand-new opportunity to design high-performance devices. WTe 2 , a recently popular player in two-dimensional (2D) materials with low-symmetry lattice structures, has exhibited outstanding functional device applications [ 11 , 12 ] based on its heavy atomic mass, low-energy optical absorption [ 13 ], thickness-dependent anisotropy of Raman modes [ 14 ], and superconductivity properties [ 15 , 16 ]. It has been reported that the conductivity and the photoelectric anisotropy ratio of WTe 2 film are about 10 3 and 300 [ 17 ], respectively, allowing it to be applied to anisotropic electric and photonic devices [ 18 , 19 , 20 , 21 , 22 ].…”

Section: Introductionmentioning

confidence: 99%

Improved Thermal Anisotropy of Multi-Layer Tungsten Telluride on Silicon Substrate

Fang

Liu

et al. 2023

Nanomaterials

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WTe2, a low-symmetry transition metal dichalcogenide, has broad prospects in functional device applications due to its excellent physical properties. When WTe2 flake is integrated into practical device structures, its anisotropic thermal transport could be affected greatly by the substrate, which matters a lot to the energy efficiency and functional performance of the device. To investigate the effect of SiO2/Si substrate, we carried out a comparative Raman thermometry study on a 50 nm-thick supported WTe2 flake (with κzigzag = 62.17 W·m−1·K−1 and κarmchair = 32.93 W·m−1·K−1), and a suspended WTe2 flake of similar thickness (with κzigzag = 4.45 W·m−1·K−1, κarmchair = 4.10 W·m−1·K−1). The results show that the thermal anisotropy ratio of supported WTe2 flake (κzigzag/κarmchair ≈ 1.89) is about 1.7 times that of suspended WTe2 flake (κzigzag/κarmchair ≈ 1.09). Based on the low symmetry nature of the WTe2 structure, it is speculated that the factors contributing to thermal conductivity (mechanical properties and anisotropic low-frequency phonons) may have affected the thermal conductivity of WTe2 flake in an uneven manner when supported on a substrate. Our findings could contribute to the 2D anisotropy physics and thermal transport study of functional devices based on WTe2 and other low-symmetry materials, which helps solve the heat dissipation problem and optimize thermal/thermoelectric performance for practical electronic devices.

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Thickness dependent anisotropy of in-plane Raman modes under different temperatures in supported few-layer WTe2

Cited by 10 publications

References 48 publications

In-Plane Phonon Anisotropy and Anharmonicity in Exfoliated Natural Black Arsenic

In-Plane Phonon Anisotropy and Anharmonicity in Exfoliated Natural Black Arsenic

In-plane optical anisotropy of two-dimensional VOCl single crystal with weak interlayer interaction

Improved Thermal Anisotropy of Multi-Layer Tungsten Telluride on Silicon Substrate

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