Reduced temperature-dependent thermal conductivity of magnetite thin films by controlling film thickness

Abstract

We report on the out-of-plane thermal conductivities of epitaxial Fe3O4 thin films with thicknesses of 100, 300, and 400 nm, prepared using pulsed laser deposition (PLD) on SiO2/Si substrates. The four-point probe three-omega (3-ω) method was used for thermal conductivity measurements of the Fe3O4 thin films in the temperature range of 20 to 300 K. By measuring the temperature-dependent thermal characteristics of the Fe3O4 thin films, we realized that their thermal conductivities significantly decreased with decreasing grain size and thickness of the films. The out-of-plane thermal conductivities of the Fe3O4 films were found to be in the range of 0.52 to 3.51 W/m · K at 300 K. For 100-nm film, we found that the thermal conductivity was as low as approximately 0.52 W/m · K, which was 1.7 to 11.5 order of magnitude lower than the thermal conductivity of bulk material at 300 K. Furthermore, we calculated the temperature dependence of the thermal conductivity of these Fe3O4 films using a simple theoretical Callaway model for comparison with the experimental data. We found that the Callaway model predictions agree reasonably with the experimental data. We then noticed that the thin film-based oxide materials could be efficient thermoelectric materials to achieve high performance in thermoelectric devices.

Effect of grain size on thermal transport in post-annealed antimony telluride thin films

“…Cross-plane thermal conductivity measurements were conducted using four-point-probe 3- ω measurements in the 20 to 300 K temperature range in a vacuum of 5 × 10 −5  Torr, which has been proven to be a promising measurement technique for both 1D nanostructures [7,8,32] and 2D thin films [28]. Figure 3 shows the temperature oscillation of the in-phase component, Δ T s+f ( ω ), for the 400-nm-thick Sb 2 Te 3 thin films annealed at temperatures of 200°C to 350°C, with the Δ T s ( ω ) value of the substrates (SiO 2 /Si) also added as a reference.…”

“…The in-plane electrical conductivity of the films was measured at room temperature using a four-point probe method, and the out-of-plane (cross-plane) thermal conductivity ( κ f ) of the thin film was measured using a four-point-probe differential 3- ω technique with an accuracy of ±5% [27]. A detailed description of the measurement setup can be found in our previous publication [28]. Briefly, a thin SiO 2 layer (approximately 100 nm) was first deposited onto the Sb 2 Te 3 thin film through plasma-enhanced chemical vapor deposition to ensure the electrical insulation of the films.…”

Effect of grain size on thermal transport in post-annealed antimony telluride thin films

“…The in-plane electrical conductivity of the films was measured at room temperature using a four-point probe method, and the out-of-plane (crossplane) thermal conductivity (κ f ) of the thin film was measured using a four-point-probe differential 3-ω technique with an accuracy of ±5% [27]. A detailed description of the measurement setup can be found in our previous publication [28]. Briefly, a thin SiO 2 layer (approximately 100 nm) was first deposited onto the Sb 2 Te 3 thin film through plasma-enhanced chemical vapor deposition to ensure the electrical insulation of the films.…”

“…Cross-plane thermal conductivity measurements were conducted using four-point-probe 3-ω measurements in the 20 to 300 K temperature range in a vacuum of 5 × 10 −5 Torr, which has been proven to be a promising measurement technique for both 1D nanostructures [7,8,32] and 2D thin films [28]. Figure 3 shows the temperature oscillation of the in-phase component, ΔT s+f (ω), for the 400-nmthick Sb 2 Te 3 thin films annealed at temperatures of 200°C to 350°C, with the ΔT s (ω) value of the substrates (SiO 2 /Si) also added as a reference.…”

Thermoelectric characterization and fabrication of nanostructured p-type Bi0.5Sb1.5Te3 and n-type Bi2Te3 thin film thermoelectric energy generator with an in-plane planar structure

“…15 The detailed measurement set-up and theoretical details can be found in our previous publication. 16 The thermal conductivity measurements of the films were performed at room temperature in a closed cycle refrigerator (CCR, Janis, USA) system equipped with turbo pump (Edward, UK).…”