Transport Properties of Few-Layer NbSe2: from Electronic Structure to Thermoelectric Properties
Transport Properties of Few-Layer NbSe2: from Electronic Structure to Thermoelectric Properties
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DOI：
10.1016/j.mtphys.2022.100789
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发表时间：
2022-07
影响因子：
11.5
通讯作者：
Tian-Yuan Zhu;Peter M. Litwin;Md. Golam Rosul;D. Jessup;Md Sabbir Akhanda;F. Tonni;S. Krylyuk;A. Davydov;P. Reinke;S. McDonnell;M. Zebarjadi
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文献类型：
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作者：
Tian-Yuan Zhu;Peter M. Litwin;Md. Golam Rosul;D. Jessup;Md Sabbir Akhanda;F. Tonni;S. Krylyuk;A. Davydov;P. Reinke;S. McDonnell;M. Zebarjadi
4-用分子束外延法在SiO2上生长NbSe 2层。原位X射线光电子能谱测量表明，Nb的丰富的化学计量比（Nb 1 + xSe 2）可能是由于Nb原子之间的NbSe 2层的嵌入。使用扫描隧道显微镜和局域态密度测量以及能带结构计算确认样品的金属性质。这种金属性质与测得的小塞贝克系数和大电导率值一致。在50 K下观察到块状单晶样品的Seebeck系数的符号变化，而在120 K下观察到多晶少层样品的Seebeck系数的符号变化。由于样品是金属的，这种符号的变化是费米能级处态密度斜率变化的结果。测得的塞贝克系数的温度依赖性与理论计算4层NbSe 2。少层样品的室温Seebeck系数为负值，但氧化后，其Seebeck系数变为正值。用热扩散成像法测量了样品的低温面内热导率，在200 K时为（32 ± 10）W/m·K。
4-layer NbSe2is grown on SiO2by molecular beam epitaxy. The in-situ X-ray photoelectron spectroscopy measurements suggest an Nb-rich stoichiometry (Nb1+xSe2) likely due to the intercalation of Nb atoms in between the NbSe2layers. The metallic nature of the samples is confirmed using scanning tunneling microscopy and local density of state measurements as well as band structure calculations. This metallic nature is consistent with the small measured Seebeck coefficient and large electrical conductivity values. A change of sign in the Seebeck coefficient is observed in the bulk single crystal sample at 50 K, and in the polycrystalline few-layer sample at 120 K. Since the samples are metallic, this change of sign is the result of a change in the density of state slope at the Fermi level. The temperature dependence of the measured Seebeck coefficient matches with theoretical calculations for 4-layer NbSe2. The room temperature Seebeck coefficient is negative, but when oxidized, that of the few-layer sample changed to positive. The in-plane thermal conductivity of the few-layer samples is measured using the heat diffusion imaging method at low temperatures and is (32 ± 10) W/m∙K at 200 K.