Nanoscale heat transport through the hetero-interface of SrRuO₃ thin films

Abstract

A SrRuO3 thin film has been widely used as a metal electrode in electronic devices based on transition metal oxides, and hence it is important to understand its thermal transport properties to minimize a thermal degradation problem during the device operation. Using the time-domain thermoreflectance measurement technique, we investigate the cross-plane thermal conductivity of the SrRuO3 thin films with a thickness variation from 1 μm to 8 nm. We find that the thermal conductivity is reduced from about 6 W m−1 K−1 for the 1 μm thick film to about 1.2 W m−1 K−1 for the 8 nm thick film, and attribute this behavior to the boundary scattering of thermal carriers which originally have the mean free path of about 20 nm in a bulk state. Also, we observe a clear dip behavior of the thermal conductivity in the intermediate thickness around 30 nm which suggests an existence of a strong scattering source other than the film boundary. We explain this result by considering an additional interfacial scattering at the tetragonal-orthorhombic phase boundary which is formed during the strain relaxation with an increase of the film thickness.

Giant Enhancement of Electron–Phonon Coupling in Dimensionality‐Controlled SrRuO3 Heterostructures

“…The experimental results (symbols) are well reproduced by Boltzmann's transport model (dashed line) with l MFP = 20 nm and κ bulk = 5.5 W m −1 K −1 in good agreement with the previous results obtained by the conventional t ‐domain thermo‐reflectance method. [ 31 ] On the other hand, the bottom panel of Figure 2c shows that σ B is nearly independent of x , indicating well‐defined SRO/STO interfaces of SLs. These results consistently validate our analyses for characterizing G ep values of the SRO heterostructures.…”

“…The phonon specific heat was taken from the literatures as C l = 2.85 and 2.56 J cm −3 K −1 for SRO and STO, respectively. [ 31 ] The electron heat capacity was ignored for the insulating STO, and that for the SRO was estimated from the density of states at the Fermi level for a given SRO thickness (Supporting Information S3 ). At the bottom and top surfaces, the Neumann boundary condition was considered as .…”

Thermal Transport Evolution Due to Nanostructural Transformations in Ga-Doped Indium-Tin-Oxide Thin Films

“…In the error estimation, we considered the sensitivity results, uncertainties in the pre-parameters used in the thermal transport model, and the position-dependent inhomogeneity. After merging all these factors, we estimated the final error by minimizing the Kullback-Leibler divergence [ 30 ]. The obtained parameters of G Al-ITO and κ ITO are presented in Figure 4 a,b, respectively.…”

Correlation between structural phase transition and surface chemical properties of thin film SrRuO3/SrTiO3 (001)

“…22 In addition, the exotic transport properties of SRO have attracted much interest in basic research, e.g., superconductivity, ferromagnetism, and topological hall effect. [23][24][25][26][27][28][29][30][31] Previously, it is reported that bulk SRO shows a structural phase transition (SPT) from the orthorhombic to tetragonal phase at 547 ○ C, and from the tetragonal to cubic phase at 677 ○ C. 32 Interestingly, when prepared as a thin film (∼less than 40 nm thick), SRO makes the SPT from the monoclinic to tetragonal phase at 200 ○ C, which is significantly lower than the bulk SRO. 33 Although a substrate-induced strain is pointed out as the cause of the low temperature SPT of the SRO thin film, the exact mechanism of the SPT has not been answered.…”