Electronic thermal conductivity of superconducting thin films of lead-indium alloy

The thermal conductivity of thin films of superconducting Pb-3 at. % In alloy is measured in the normal and the superconducting states. The ratio of the electronic thermal conductivity in the superconducting state K_es to that in the normal state K_en is found to be in good agreement with the Bardeen, Rickayzen and Tewordt theory with 2?_O = 4.36 kT_c.     

Effect of nitrogen doping on the thermal conductivity of GeTe thin films

The 3ω method was employed to determine the effect of nitrogen doping (5 at.%) on the thermal conductivity of sputtered thin films of stoichiometric GeTe (a material of interest for phase change memories). It was found that nitrogen doping has a detrimental effect on the thermal conductivity of GeTe in both phases, but less markedly in the amorphous (–25%) than in the crystalline one (–40%). On the opposite, no effect could be detected on the measured thermal boundary resistance between these films and SiO₂, within the experimental error. Our results agree with those obtained by molecular dynamic simulation of amorphous GeTe. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

氩晶体薄膜法向热导率的分子动力学模拟

结合卫星“微型核”的特点，研究电介质薄膜中的导热机理以及薄膜厚度对导热系数的影响.以结构较为简单、具有可靠势能函数，实验数据较为丰富和可靠的氩的(fcc)晶体为模型,采用平衡分子动力学方法(EMD)和各向异性非平衡分子动力学方法(NEMD)计算了氩晶体及其法向薄膜的热导率,并与实验结果进行比较.模拟结果表明，氩晶体纳米薄膜的热导率显著小于对应大体积晶体的实验值，具有明显的尺寸效应.在氩薄膜厚度为2.124—5.310nm的模拟范围内,薄膜的法向热导率随着薄膜厚度的增加而呈近似线性增加. 关键词： 热导率 纳米薄膜 尺寸效应 平衡分子动力学 非平衡分子动力学     

Electrical conductivity of PbTe thin films

PbTe thin films were prepared by vacuum technique with different thicknesses ranging from 550 to 3000 Å. The electrical resistivity as a function of the film thickness and mobility was measured. The dependence of log (resistivity) and log (current) was studied as a function of the universal temperature. The activation energies were estimated before and after the break. The transition of conductivity from n-type to p-type is attributable to the increase in the number of migrating lead vacancies. An increase of the applied voltages on the thin films caused the shift of breaking temperature to higher temperatures. This shift is attributed to the creation of Pb vacancies which retard the break.     

Microwave relaxation and phenomenological damping in thin films

The relation between relaxation timeT, frequency swept resonance linewidth , and phenomenological damping is given by =2/T=(_x+_y), where _x,y = (H ₀+(N _x,y –N _z ) 4M _s ).N _x,y,z are sample demagnetizing factors,H ₀ is the effectivez-directed static field, 4M _s is the saturation induction, and is the gyromagnetic ratio. This fairly simple but general relation shows that the numerical relation between damping and relaxation at a given frequency can be quite different for in-plane and normally magnetized thin films. For thesame loss processes, so thatT andT are equal, is larger than . For permalloy films at 1 GHz, =15 . In addition, the conventional field swept linewidth, H=/, is simply related to only forN _x =N _y . Both and H are geometry dependent and do not provide an intrinsic measure of the relaxation. These results are confirmed by both resonance and transient response experiments. The large values of for large angle switching may also be partially explained by this analysis because the relevant magnetization motion is due to a demagnetizing field normal to the film plane.Visiting scientist on leave fromRaytheon Company, U.S.A. Supported by the Japan Society for the Promotion of Science.     

On the theory of nonlinear thermal conductivity

A nonlinear differential equation of thermal conductivity is derived phenomenologically from the general principles of construction of functional Q invariant to the inversion operation I(r →–r), and the temperature evolution dynamics is analyzed in the nonstationary case. The proposed method makes it possible to reveal some general regularities in the physical behavior of such systems for describing irreversible phenomena in self-organization processes. It is noted that an analogous situation may take place, for example, in strongly inhomogeneous structures with stochastic internal heat fluxes.     

Electrical conductivity of multi-layered metallic thin films

Multi-layered metallic thin films have quite unique properties such as electrical conductivity because of their enhanced interactions at the interfaces between different metals. A theoretical solution has been derived for the distribution functions of the conduction electrons, through Boltzmann's equation and certain interface boundary conditions. The solution of the electrical conductivity for the multi-layered metallic thin films is given.     

Nanostructure and conductivity of thin metal films

Amorphous silver, copper, gold, and iron films of a thickness between 6 and 350 nm are grown on polymeric substrates by vacuum evaporation. The nanostructure of the films is investigated. The dependence of the conductivity on the film thickness is obtained, and a correlation between the surface morphology and the conductivity is established.     

Effect of scratches on the conductivity of thin films

The conductivity of a two-dimensional composite, a thin film with a system of randomly distributed nonconducting scratches, is considered. A comparison with the results of a model experiment is performed.     

On the electric conductivity of BaTiO3 thin films

Results are presented of tests on the conductivity of BaTiO₃ and Ba(Ti, Sn)O₃ films obtained by various techniques and thickness order 1–100 m. Studies on electrical photoconductivity were conducted using ultraviolet radiation.The author wishes to thank R.Dytry, J.Genbar, J.Pawlik and R.Skulski for help in the experiments.     

On the theory of ferromagnetic thin films

As is known, the second approximation in the calculation of the partition function by the traces method of ferromagnetic thin films gives wrong results for the coordination number equal to eight. In order to obtain correct results even for this case, the third order approximation of the partition function is developed and thus the magnetic properties of body-centred cubic iron thin films are studied. The dependence of the Curie temperature on the thickness, for different values of the ratio between the anisotropy constant and the exchange energy between two neighbours, is discussed. A value can be chosen for this ratio such that the thin film becomes ferromagnetic only for a thickness greater than a definite value.

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Modeling for thermal conductivity measurements of thin films using photothermal deflection with obliquely crossed configuration

Received: 21 December 1996     

A contactless method for investigating the thermal properties of thin films

The photothermal deflection technique has been extended as a contactless method to investigate thermal transport in thin films. A theoretical model is developed which quantitatively describes the transport behavior, and is shown to be in excellent agreement with experimental results. This approach yields the thermal diffusivity directly and in a spatially-resolved manner.     

Electrical conductivity studies of mixed phthalocyanine thin films

Thin films of mixed of Copper Phthalocyanine (CuPc) and Nickel Phthalocyanine (NiPc) are deposited onto a pure glass substrate by a simultaneous thermal evaporation technique at room temperature. The material D.C. electrical conductivity of films at room temperature and also films annealed at 523 K has been investigated. The optical absorption and band gaps of the films are also measured. The results show that the electrical resistance is lower for the mixed films compared with the pure samples and also the optical band gap decreases for the mixed samples compared to the pure samples.     

Preparation and electrical conductivity of LISICON thin films

LISICON thin films have been prepared with RF sputtering and subsequent heat-treatment. The crystal phases of sputtered films depend on the sputtering conditions, especially the target composition and ambient gas atmosphere. Though the as-sputtered films in Ar-O₂ mixed gas (target composition: Li₃Zn_0.5GeO₄+0.5 ZnO, gas pressure: 9×10^-2 Torr, oxygen gas content: 74.6%) were amorphous; LISICON single phase thin films were obtained after annealing at 600°C for 6 h. The conductivity of the film at 500°C is 5×10^-3ω^-1cm^-1 which is slightly lower than that for ceramic Li₃Zn_0.5GeO₄.     

Thermal conductivity of nanoscale polycrystalline ZnO thin films

Thermal conductivities (TCs) of ZnO thin films of thickness 80-276 nm prepared by sol-gel method are measured by the transient thermoreflectance (TTR) system. The obtained TCs ranging from 1.4 to 6.5 W/m K decrease while the thickness decrease. The measured TCs are much smaller than those of bulk ZnO, which is about 100 W/m K. The possible reasons for the decrease are the grain boundary and defects. The latter is the dominating one from the analysis.     

Effect of scratches on the conductivity of anisotropic thin films

The conductivity of a two-dimensional composite with natural anisotropy, a thin anisotropic film with a system of randomly distributed nonconducting scratches is considered. An exact expression for the conductivity in the approximation linear in the concentration of scratches is derived. The case of consider-able concentrations is examined using the generalized effective-medium theory. The conductivity near the percolation threshold is treated in the framework of similarity theory.