共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
X. Zhang H. Q. Xie M. Fujii H. Ago K. Takahashi T. Ikuta H. Abe T. Shimizu 《International Journal of Thermophysics》2007,28(1):33-43
This paper reports on measurements of in-plane thermal conductivities, electrical conductivities, and Lorentz number of two
microfabricated, suspended, nanosized thin films with a thickness of 28 nm. The effect of the film thickness on the in-plane
thermal conductivity is examined by measuring other nanofilm samples with a thickness of 40 nm. The experimental results show
that the electrical conductivity, resistance–temperature coefficient, and in-plane thermal conductivity of the nanofilms are
much smaller than the corresponding bulk values from 77 to 330 K. However, the Lorentz number of the nanofilms is about two
times that of the bulk value at room temperature, and even up to three times that of the bulk value at 77 K. These results
indicate that the relation between the thermal conductivity and electrical conductivity of the nanofilms does not follow the
Wiedemann–Franz law for bulk metallic materials. 相似文献
3.
Sun Rock Choi Dongsik Kim Sung-Hoon Choa Sung-Hoon Lee Jong-Kuk Kim 《International Journal of Thermophysics》2006,27(3):896-905
The thermal conductivity of AlN and SiC thin films sputtered on silicon substrates is measured employing the 3ω method. The thickness of the AlN sample is varied in the range from 200 to 2000 nm to analyze the size effect. The SiC thin films are prepared at two different temperatures, 20 and 500°C, and the effect of deposition temperature on thermal conductivity is examined. The results reveal that the thermal conductivity of the thin films is significantly smaller than that of the same material in bulk form. The thermal conductivity of the AlN thin film is strongly dependent on the film thickness. For the case of SiC thin films, however, increased deposition temperature results in negligible change in the thermal conductivity as the temperature is below the critical temperature for crystallization. To explain the thermal conduction in the thin films, the thermal conductivity and microstructure are compared using x-ray diffraction patterns. 相似文献
4.
The thermal conductivity of thin films of copper (400–8000 Å) has been measured in the temperature range 100–500 K. It decreases with decreasing film thickness. An electrical-thermal transport analogy has been used to calculate the size-dependent thermal conductivity of the thin copper films. The decrease of the thermal conductivity with thickness is attributed partly to the scattering of the conduction electrons from the film surfaces and partly to the scattering by lattice impurities and frozen-in structural defects in the films. The variation of the thermal conductivity with temperature agrees with the variation for bulk copper. The Lorentz ratio has been determined and is found to vary from 2.4 × 10-8 to for film thicknesses ranging from 400 to 8000 Å. 相似文献
5.
Technological development, especially in microelectronics, necessitates the development of new and improved methods for measuring the thermal properties of materials, especially in the form of ultrathin films. Previously, modified ac calorimetry (laser-heating Ångstrom method) using a scanning laser as the energy source was developed and shown to provide accurate values of thermal diffusivity and derived thermal conductivity for a broad range of materials in the form of free-standing thin sheets or films, wires including fiber bundles, and some films on substrates. This paper describes further applications of the modified ac-calorimetry technique for measurements of the thermal conductivity of thin films deposited on substrates. It was used to measure successfully the thermal conductivities of 1000- to 3000-Å-thick aluminum nitride films, aluminum oxide films, etc., which were deposited on a glass substrate. It was also shown to be suitable for developmental measurements on submicron-thick chromatic films deposited on a PET substrate, which are photothermal recording layers, used in the media of CD-R drives of computer systems. 相似文献
6.
S. L. Patil S. G. Pawar A. T. Mane M. A. Chougule V. B. Patil 《Journal of Materials Science: Materials in Electronics》2010,21(12):1332-1336
Nanocrystalline Zinc oxide thin films have been deposited by sol–gel spin coating technique and then have been analyzed before and after a suitable thermal annealing in order to test their applications in various reducing and oxidizing gases. ZnO thin films were highly sensitive and selective for NH3 gas. The spectrophotometric and conductivity measurements have been performed in order to determine the optical and electrical properties of zinc oxide thin films. The structure and the morphology of such material have been investigated by high resolution electron microscopy and small area electron diffraction. The average particle size is in 60–70 nm. 相似文献
7.
Ines Nieto-Carvajal Miriam Más-Montoya Jose Abad David Curiel Jaime Colchero 《Journal of Materials Science: Materials in Electronics》2014,25(12):5452-5461
A systematic study on the thin film morphology of heteroacenic derivatives such as indolo[2,3-a]carbazole and 11,12-dioctylindolo[2,3-a]carbazole has been carried out using scanning force microscopy and optical microscopy techniques. The investigation has comprised the preparation of a series of thin films by combining different solvents (dimethylformamide and tetrahydrofurane), substrates (glass, gold, silicon and aluminium) and deposition techniques (spin coating and thermal evaporation) we found a wide variety of self-assembled structures. In addition, conductivity measurements have been performed, showing a very large spread in conductivity values. Some of the samples give quite high conductivity while others conduct very poorly, even in the case of samples prepared with essentially the same conditions. These results indicate that morphology is very critical for the final conductivity of the thin films. In addition we conclude that for some of the films prepared the homogeneous thin film approximation must be revised otherwise obtained conductivity measurements lead to significant error. 相似文献
8.
Sun Rock Choi Dongsik Kim Sung-Hoon Choa 《International Journal of Thermophysics》2006,27(5):1551-1563
The thermal diffusivity of Au, Sn, Mo, and Al0.97Ti0.03 alloy thin films, which are commonly used in microelectromechanical (MEMs) system applications, is measured by two independent methods — the ac calorimetric and photothermal mirage methods. Both methods yield similar results of the thin-film thermal conductivity, but the uncertainty of the mirage technique is found to be relatively large because of the large temperature increase during the measurement. The measured thermal diffusivities of the thin films are generally lower than those of the same bulk material. Especially, the Al0.97Ti0.03 thin film shows a pronounced thermal conductivity drop compared with bulk Al, which is believed to be mainly due to impurity scattering. Comparison of the thermal conductivity with the electrical conductivity measured by the standard four-probe technique indicates that the relation of thermal and electrical conductivities follows the Wiedemann–Franz law for the case of Au and Sn thin films. However, the Lorentz number is significantly larger than the theoretical prediction for the case of Al0.97Ti0.03 and Mo thin films. 相似文献
9.
A. Albert Irudayaraj R. Srinivasan P. Kuppusami E. Mohandas S. Kalainathan K. Ramachandran 《Journal of Materials Science》2008,43(3):1114-1120
Titanium nitride (TiN) thin films were prepared by reactive DC magnetron sputtering under different nitrogen flow rates and
at constant substrate temperature as well as at constant nitrogen flow rate and at different substrate temperatures. Photoacoustic
measurement of the thermal properties of the films revealed that the thermal diffusivity and thermal conductivity of the TiN
thin films are significantly lower than the bulk values and that the grain size of the films has substantial influence on
the thermal properties of TiN thin films. The thermal conductivity of the films decreases with increasing nitrogen flow rates
and increases with increasing substrate temperature. The above opposing behaviour in the thermal properties is found to be
related to the microstructure, especially, the grain size of the films. 相似文献
10.
Phase transition behaviors and thermal conductivity measurements of nitrogen-doped Sb2Te3 thin films
Crystallization temperature of nitrogen-doped Sb2Te3 (ST) thin films increased with increasing nitrogen doping concentration, which indicates that the long-term stability of the metastable amorphous state can be improved by nitrogen doping. The root-mean-square (rms) roughness values of the films showed a significant decrease with nitrogen doping. Thermal conductivity of nitrogen-doped ST thin films was measured using a transient thermoreflectance (TTR) technique. It was found that the thermal conductivity decreased with increasing nitrogen doping concentration and increased with increasing annealing temperature. Nitrogen-doped ST thin films are suitable phase-change materials for low programming power consumption applications of phase-change random access memory (PCRAM). 相似文献
11.
Improved thermoelectric performance of highly-oriented nanocrystalline bismuth antimony telluride thin films is described. The thin films are deposited by a flash evaporation method, followed by annealing in hydrogen. By optimizing the annealing conditions, the resulting thin films exhibit almost perfect orientation with the c-axis normal to the substrate, and are composed of nano-sized grains with an average grain size of 150 nm. The in-plane electrical conductivity and Seebeck coefficient were measured at room temperature. The cross-plane thermal conductivity of the thin films was measured by a 3ω method, and the in-plane thermal conductivity was evaluated by using an anisotropic factor of thermal conductivity based on a single crystal bulk alloy with almost the same composition and carrier concentration. The measured cross-plane thermal conductivity is 0.56 W/(m K), and the in-plane thermal conductivity is evaluated to be 1.05 W/(m K). Finally, the in-plane power factor and figure-of-merit, ZT, of the thin films are 35.6 μW/(cm K2) and 1.0 at 300 K, respectively. 相似文献
12.
U. S. Sajeev C. Joseph Mathai S. Saravanan Rajeev R. Ashokan S. Venkatachalam M. R. Anantharaman 《Bulletin of Materials Science》2006,29(2):159-163
Polyaniline is a widely studied conducting polymer and is a useful material in its bulk and thin film form for many applications,
because of its excellent optical and electrical properties. Pristine and iodine doped polyaniline thin films were prepared
by a.c. and rf plasma polymerization techniques separately for the comparison of their optical and electrical properties.
Doping of iodine was effectedin situ. The structural properties of these films were evaluated by FTIR spectroscopy and the optical band gap was estimated from
UV-vis-NIR measurements. Comparative studies on the structural, optical and electrical properties of a.c. and rf polymerization
are presented here. It has been found that the optical band gap of the polyaniline thin films prepared by rf and a.c. plasma
polymerization techniques differ considerably and the band gap is further reduced byin situ doping of iodine. The electrical conductivity measurements on these films show a higher value of electrical conductivity
in the case of rf plasma polymerized thin films when compared to the a.c. plasma polymerized films. Also, it is found that
the iodine doping enhanced conductivity of the polymer thin films considerably. The results are compared and correlated and
have been explained with respect to the different structures adopted under these two preparation techniques. 相似文献
13.
High Tc (16.8 K) niobium nitride thin films have been prepared by rf diode sputtering in N2/Ar atmosphere and subsequent high temperature annealing. Josephson tunnel junctions have been made by thermal oxidation of the films. The geometry is defined by high resolution photolithography. The Josephson junctions have been characterized by magnetic field diffraction measurements and other techniques and are shown to be particularly suitable for applications especially in superconducting microwave integrated devices. 相似文献
14.
Taehee Jeong Jian-Gang Zhu Sining Mao Tao Pan Yun Jun Tang 《International Journal of Thermophysics》2012,33(6):1000-1012
The cross-plane thermal conductivity of SiC amorphous films was measured employing the transient thermoreflectance technique. The SiC films were deposited on silicon substrates by RF magnetron sputtering at room temperature. The thickness of the films was varied in the range from 100?nm to 2500?nm to analyze the size effect. The results found that the thermal conductivity of the SiC thin films is significantly smaller than that of the SiC material in bulk form. The small thermal conductivity stems from the structural disorder of the films, which was confirmed by high-resolution transmission electron microscopy and X-ray diffraction. In addition, the contribution of the thermal boundary resistance to the thermal conductivity of the films is discussed. 相似文献
15.
本文通过电化学沉积方法制备了一种四氯苯醌/三苯磷可控掺杂四取代酞菁铜薄膜材料体系,研究了该可控掺杂有机薄膜材料的导电性能.研究结果表明,四取代酞菁铜可控掺杂薄膜材料的电导率,随着温度的升高或掺杂剂浓度的增加而显著增加,其原因是酞菁铜给体与四氯苯醌和三苯基磷等小分子电子受体之间发生了较强的氧化还原作用. 相似文献
16.
Recent contributions of parameter estimation in the measurement of thermal properties are of great importance. In comparison with other techniques such as steady state (hot guarded plate, etc.) or transient (line source method, flash method, etc.), the use of parameter estimation provides more information and, in most cases, produces faster results. With this technique the thermal conductivity and the volumetric specific heat are estimated simultaneously and as a function of time, temperature, or position. This method requires experimental data, such as transient temperature and heat flux measurements. Previously, the temperature measurements came from thermocouples embedded in the sample. These thermocouples are introduced in the sample either by drilling holes or by molding the material around a series of thermocouples. Both operations are time-consuming and costly and are needed for each sample. In this study, temperature measurements are made only on the two sides of the samples with thin resistance thermometers. Since the sensors are not inside the material, the effect of the thermal contact conductance between sensor and sample was first investigated. The value of this thermal contact conductance was estimated by using samples of high-conductivity material. Using these values, the estimated thermal properties obtained with surface temperature measurements are compared with values provided by other methods for several low-thermal conductivity materials; agreement has been very good. 相似文献
17.
CdTe thin films were deposited on KCl and glass substrates using thermal evaporation technique under high vacuum conditions. CdTe bulk compound grown by vertical directional solidification (VDS) technique was used as the source material to deposit thin films. Powder X-ray diffraction technique was employed to identify the phase of the as grown bulk CdTe compound as well as its thin films. Surface morphology and the stoichiometry of the bulk compound and thin films was carried out by using scanning electron microscope (SEM) with an attachment of energy dispersive spectrometer(EDS). Microstructural features associated with the as deposited CdTe thin films were studied by using transmission electron microscope (TEM). The films deposited on to glass substrates at different temperatures have been used to study the I-V characteristics of the films. These parameters have been studied in detail in order to prepare good quality nanostructured thin films of CdTe compound. CdTe bulk compound grown by VDS method and its thin films prepared by thermal evaporation method found to have single phase with cubic structure. Size of the particles in the as deposited films vary between 5 and 40 nm In the present study efforts have been made to correlate the electrical and optical properties of the CdTe thin films with the corresponding microstructural features associated with them. 相似文献
18.
C. A. Nieto de Castro R. A. Perkins H. M. Roder 《International Journal of Thermophysics》1991,12(6):985-997
New measurements of the thermal conductivity of liquid toluene between 300 and 550 K have been used to study the importance of radiative heat transfer when using the transient hot-wire technique. The experimental data were used to obtain the radiation correction to the hot-wire temperature rises. Radiationcorrected values of thermal conductivity are reported. This study shows that the transient hot-wire method is much less affected by radiation than steady-state techniques. 相似文献
19.
The thermal effusivity of gold, aluminum, and copper thin films of nanometric thickness (20 nm to 200 nm) was investigated in terms of the films’ thickness. The metallic thin films were deposited onto glass substrates by thermal evaporation, and the thermal effusivity was estimated by using experimental parameters such as the specific heat, thermal conductivity, and thermal diffusivity values obtained at room conditions. The specific heat, thermal conductivity, and thermal diffusivity values of the metallic thin films are determined with a methodology based on the behavior of the thermal profiles of the films when electrical pulses of few microseconds are applied at room conditions. For all the investigated materials, the thermal effusivity decreases with decreased thickness. The thermal effusivity values estimated by the presented methodology are consistent with other reported values obtained under vacuum conditions and more elaborated methodologies. 相似文献
20.
Metallic zinc thin films were deposited onto glass substrates using vacuum thermal evaporation method. By thermal oxidation of as-deposited Zn films, in ambient conditions, at different temperatures (570, 670 and 770 K, respectively, for 1 h) zinc oxide thin films were obtained. The structural characteristics of the obtained films were investigated by X-ray diffraction technique and atomic force microscopy. Characteristic XRD patterns of oxidized films show small and narrow peaks superimposed on the large broad background of the amorphous component of the substrate. Optical transmittance spectra were recorded and it was observed that the transmittances of the studied films increased with increasing oxidation temperature. The values of the optical bandgap, E g, evaluated from Tauc plots, were found to be ranged between 3·22 and 3·27 eV. Electrical conductivity measurements were performed and it was observed that, after performing a heat treatment, the electrical conductivity of analysed samples decreased with one or two orders of magnitude. The gas sensitivity was investigated for some reducing gases such as acetone, methane and liquefied petroleum gas and it was observed that the films studied were selective to acetone. 相似文献