Temperature-dependent Thermal Conductivity of a Single Germanium Nanowire Measured by Optothermal Raman Spectroscopy

Abstract

We investigate temperature dependent thermal conductivity 𝜅(𝑇) in a single Ge nanowire (NW) using Optothermal Raman Spectroscopy which utilizes the temperature dependence of Raman lines as a local probe for temperature. The experiment was done from 300 K to above 700 K, a temperature range in which thermal conductivity of single NWs has been explored rarely. The thermal conductivity of Ge NWs (grown by vapor liquid solid mechanism), at around room temperature were observed to lie in the range 1.8 -4.2 W/m.K for diameters between 50-110 nm. The thermal conductivity at a given temperature was found to follow a linear dependence on NW diameter, suggesting that the low magnitude of 𝜅(𝑇) is determined by diffused scattering of phonons from the surface of NWs that reduces it severely from its bulk value. 𝜅(𝑇) shows ~1 T behavior which arises from the Umklapp processes. The quantitative estimation of errors arising from the opto-thermal measurement and methods to mitigate them has been discussed. We also suggest a quick way to estimate approximately the thermal conductivity of Ge and Si NWs using the above observations.

Lattice dynamics of Ge1−xSnx alloy nanowires

“…Temperature dependent Raman spectroscopy is a simple, convenient and contact Paper Nanoscale less method for probing the thermal properties of 2D as well as 1D nanostructures. 42,43 The temperature dependent Raman modes of Ge 1−x Sn x (x = 0.01, 0.06 and 0.08) alloy NWs were investigated over a temperature range between 83 and 523 K. Fig. 5 shows the temperature dependent Raman modes of the NWs estimated from the temperature dependent Raman data presented in Fig.…”

Heat Transport Control and Thermal Characterization of Low-Dimensional Materials: A Review

“…The first studies of the thermal properties of single-layer graphene were conducted by Balandin et al [ 179 , 180 ] using Raman thermometry. Since then, Raman thermometry has been used in a wide range of 2D materials [ 22 , 73 , 98 , 181 , 182 , 183 , 184 , 185 ], carbon nanotubes [ 186 ], nanowires [ 187 , 188 , 189 ], nanomembranes [ 190 , 191 , 192 , 193 ], and phononic crystals [ 24 , 33 ], among others. In general, the 2D material is transferred over a substrate, which was previously patterned with micro-holes and covered with metal layer to ensure a good thermal contact.…”

Phonons and Thermal Properties of Ge Nanowires: A Raman Spectroscopy Investigation and Phonon Simulations

“…Recently, we have used temperature-dependent Raman spectroscopy (opto-thermal spectroscopy) to measure the temperature-dependent κ of single Ge NWs down to an NW diameter of 50 nm in the temperature range of 300−700 K. 16 The results showed that in addition to the boundary scattering, the temperature dependence of κ (given as κ ∝ 1/T) is primarily controlled by the Umklapp process of phonon− phonon interaction which is determined by the anharmonicity and can be parameterized by γ. The discussion above highlights the importance of knowledge of the thermal parameters, which are difficult to measure directly through experiments.…”

“…In addition, we have also simulated the phonon mean free path and compared the simulation with the data obtained from recent experimental measurements of κ. 16 Two well-characterized ensembles of Ge NWs were used for the investigation. One was oxygen-free, pristine Ge NWs only with native surface oxide (thickness ≤2 nm), and the other was Ge NWs with a surface oxide thickness of ∼5−10 nm and thus can be considered as a core−shell type.…”