Science in China Series a-Mathematics Physics Astronomy
Recent development in the study of nonequilibrium thermophysical properties of thin films in our lab is reported. A high-speed indirect heating system by using 0.1 mus CO2 laser pulse was established. A photoelectric installation for micrometric length-change measurement, an infrared radiation pyrometer for transient temperature measurement, a high-speed acquisition system as recording device and microcomputer system for data treatment were developed. Using the systems, the traditional flash method is extended to the measurement of thermal diffusivity of the thin films of around 50 mum in thickness, and deviations of this method is analyzed for the case of thin film specimens. Nonsynchronous change of temperature rise and thermal expansion under transient heating was observed.
关键词:
thermal-diffusivity measurements
Journal of Applied Physics
Transient laser pulse has been used to generate nonsynchronous change of temperature rise and thermal expansion in thin films. The transient process of thermal expansion is recorded by a photoelectric high-speed acquisition system. By comparison of the calculated temperature rise and thermal expansion, thermal stress relaxation processes in Al films of 20-50 mum thickness is obtained. This result shows that, for transient heating, thermal stress exists even in the case of uniform temperature distribution and free expansion. And also there is a transient high stress in thin films under high-speed heating.
关键词:
Solid State Communications
Room temperature ageing and high temperature annealing were conducted to study the restructuring of the ion induced fractal aggregates on Co-Yb alloy thin films. The evolution of the nonequilibrium fractals towards equilibrium compact clusters was observed by tracing the microstructure change under transmission electron microscopy examination. The fractal aggregates restructured and eventually turned into an equilibrium morphology of Yb particles distributing uniformly on the film surfaces.
关键词:
diffusion-limited aggregation;viscous fingers;growth;dimension;anisotropy;crystal;model;zinc
Chinese Physics Letters
Measurements of the Hall coefficient (R(H)) were carried out for a polycrystalline YBa2Cu3O7-y film, a well oriented YBa2Cu3O7-y film and an oriented GdBa2Cu3O7-y film. Sign change of R(H) was observed for the two YBa2Cu3O7-y films near T(c), but not for the GdBa2Cu3O7-y film which contains partly the component of (110) orientation. The R(H) anisotropy model proposed previously turns out to be incorrect. Why the YBa2Cu3O7-y films experience sign change of R(H) while the GdBa2Cu3O7-y film does not is tentatively investigated.
关键词:
transition
Review of Scientific Instruments
The flash method including the single- and double-ended method has gained widespread acceptance for measuring thermal diffusivity of thick foils (in millimeters) as well as thin films (in microns). However when the method is employed, some basic experimental conditions are assumed. In this paper, two of the assumptions, the finite absorption depth effect and the nonlinearity of the detector, are discussed in the situation of thin film samples. For the first one, the deviation of the factor omega(1/2) (=pi(2) alpha t(1/2)/L(2)) from 1.37 and the corresponding errors in deriving thermal diffusivity from t(1/2) are discussed for various relative absorption depth delta. The result indicates criteria for the method to be available, that is, L>10 delta and L>14 delta for the double- and the single-ended method. For the second one, by considering the errors in voltage output of a (Hg, Cd)Te IR detector, how the factor omega(1/2) deviates from 1.37 and the corresponding errors in thermal diffusivity measurement under various initial temperature conditions are discussed. The results are shown graphically and tabulated. (C) 1995 American Institute of Physics.
关键词:
radiometry;pulse
Applied Physics Letters
The ferroelectric polarization dependent bipolar and conductive filament related unipolar resistive switching behaviors are investigated systematically in Au/BiFe0.95Mn0.05O3/La5/8Ca3/8MnO3 heterostructure. The results show that after conductive filaments are formed, the ferroelectric state previously polarized will keep almost unchanged. By combining the two resistive switching mechanisms together under appropriate programming conditions, a tri-state-like resistive switching behavior is realized, finding effective routes in designing high-density storage. According to these distinctive characteristics, a prototype memory device with secure information storage is properly designed as an example of promising applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4714514]
关键词:
thin-films
Acta Materialia
Pb thin films confined in Al were synthesized by means of repeated cold-rolling from stacked Al/Pb/Al sandwiches and magnetron sputtering deposition, respectively. The layer thickness of the confined Pb thin films was in a range of 6-27 nm. Differential scanning calorimetry (DSC) was used to systematically study the melting behavior of the confined Pb thin films. Above the equilibrium bulk melting point, a melting peak of superheated Pb was noticed in DSC traces. The degree of superheating increases with a decreasing film thickness and an increasing heating rate. The melting kinetics of the superheated Pb thin films is analyzed in terms of the lateral growth mechanism. The observed superheating of Pb thin films is attributed to the suppressed melt growth by the epitaxial Pb/Al interfacial configuration. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
thin films;superheating;melting;kinetics;al matrix;pb;particles;temperature;nanocrystals;stability;metals;lead;solidification;crystal
Y.F.Hu
金属学报(英文版)
Polycrystalline silicon thin films were prepared by RTCVD (rapid thermal chemical vapor deposition) method on several substrates such as SSP (silicon sheet from powder) ribbon, poly-Si wafer and mono-Si wafer, lntra-granular defects such as stacking faults, twins and microstructure defects were investigated on thin films by scan electron microscopy (SEM) technique.
关键词:
poly-Si thin film
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Japanese Journal of Applied Physics Part 1-Regular Papers Brief Communications & Review Papers
Silicon carbonitride thin films,were synthesized by reactive rf sputtering a silicon carbide target in nitrogen and argon atmosphere, or sputtering a silicon nitride target in methane and argon atmosphere, respectively. The Nanoindentation technique (Nanoindenter XP system with a continuous stiffness measurement technique) was employed to measure the hardness and elastic modulus of thin films. The effects of sputtering power on the mechanical properties are different for the two SiCN thin films. With increasing sputtering power, the hardness and the elastic modulus decrease for, the former but increase for the latter. The tendency is similar to the evolution trend of Si-C bonds in SiCN materials. This reflects that Si-C bonds provide greater hardness for SiCN thin films than Si-N and C-N bonds.
关键词:
silicon carbonitride;hardness;bond impact;chemical-vapor-deposition;nitride;coatings;carbide;growth
