Thermal conductivity of free-standing silicon nanowire using Raman spectroscopy

Abstract

Low dimensional systems, nanowires (NWs), in particular, have exhibited excellent optical and electronic properties. Understanding the thermal properties in semiconductor NWs is very important for their applications in electronic devices. In the present study, the thermal conductivity of a freestanding silicon NW is estimated by employing Raman spectroscopy. The advantage of this technique is that the excitation source (laser) acts as both the heater and probe. The variations of the first-order Raman peak position of the freestanding silicon NW with respect to temperature and laser power are recorded. From the analysis of effective laser power absorbed by exposed silicon NW and a detailed Raman study along with the concept of longitudinal heat distribution in silicon NW, the thermal conductivity of the freestanding silicon NW of ∼112 nm diameter is estimated to be ∼53 W m−1 K− 1.

Thermal Conductivity of Large-Area Polycrystalline MoSe2 Films Grown by Chemical Vapor Deposition

“…Therefore, the χ value extracted in 30 nm polycrystalline MoSe 2 films is close to that of the monolayer crystalline film. The broadening of the line width related to the phonon lifetime is attributed to the phenomenon of the zone center optical phonon decaying into two or three acoustic phonons, which stems from the lattice potential cubic and quartic anharmonicity. , Considering a four-phonon process, the line width varied with the temperature, which can be expressed using the following equation where x = ℏω/2 k b T , y = ℏω/3 k b T , ω = c ω 0 , ω is the A 1 g mode phonon frequency at 0 K, c is the speed of light in vacuum, and A ( B ) is the cubic (quartic) anharmonic constant. , …”

“…The broadening of the line width related to the phonon lifetime 14 is attributed to the phenomenon of the zone center optical phonon decaying into two or three acoustic phonons, which stems from the lattice potential cubic and quartic anharmonicity. 13,38 Considering a four-phonon process, the line width varied with the temperature, which can be expressed using the following equation…”

“…where x = ℏω/2k b T, y = ℏω/3k b T, ω = cω 0 , ω is the A 1g mode phonon frequency at 0 K, c is the speed of light in vacuum, and A (B) is the cubic (quartic) anharmonic constant. 13,32 The laser-power-dependent Raman study of the suspended MoSe 2 film is carried out using a 532 nm laser power and a 100× objective lens with a numerical aperture NA = 0.90, the Gaussian beam width of which is estimated to be 2λ 0 /(πNA) ≈ 0.37 μm. Herein, the width of the laser beam is much smaller than the diameter of the hole, which makes it possible to extract the thermal conductivity with a high accuracy.…”

“…The transfer of heat via electrons and phonons is related to the heat conductivity coefficient of a solid material . Raman spectroscopy is considered to be a simple, convenient, fast, indirect, and dependable tool to characterize the thermal properties of materials, which utilizes the sensitive response of the phonon frequency of MoSe 2 to local heating caused by a laser. − So far, this technology has been used to measure the thermal conductivity of silicon nanowires, graphene, hexagonal boron nitride, and MoS 2 . ,,,, Zhang et al adopted the optothermal Raman technique to investigate the thermal transport properties of MoSe 2 . The thermal conductivities of one-layer and two-layer MoSe 2 are estimated to be 59 and 42 W/(m·K), respectively .…”

“…13 Raman spectroscopy is considered to be a simple, convenient, fast, indirect, and dependable tool to characterize the thermal properties of materials, which utilizes the sensitive response of the phonon frequency of MoSe 2 to local heating caused by a laser. 13−16 So far, this technology has been used to measure the thermal conductivity of silicon nanowires, 13 graphene, 17 hexagonal boron nitride, 18 and MoS 2 . 2,15,19,34,40 Zhang et al 19 adopted the optothermal Raman technique to investigate the thermal transport properties of MoSe 2 .…”