| Co-Investigator(Kenkyū-buntansha) |
MAJUMDAR Arun Arizona State University Faculty of Engineering Associate professor, 工学部, 助教授
FLIK Markus Massachusetts Institute of Technology Faculty of Engineering Associate Professor, 工学部, 助教授
HIJIKATA Kunio Tokyo Institute of Technology, Faculty of Engineering Professor, 工学部, 教授 (60016582)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1991: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
High temperature superconductors possess great promise for application in electronic integrated circuit devices such as Josephson junctions. The performance of these superconducting devices is greatly affected by the temperature field of which prediction requires the knowledge of heat conduction in microscale of atomic or molecular levels, that is, molecular engineering studies. In the present study, the heat conduction and the related thermal characteristics of superconducting materials are studied from the standpoint of thermo-molecular theory as well as the interaction between thermal and electromagnetic fields in the integrated circuits of high-temperature superconducting materials to make clear the thermal problems of high-density integration of these devices.
1. Heat conduction and thermal properties of high-temperature superconducting materials : By solving the molecular dynamics and Boltzmann equations of atomic vibration and pair/nonpair electron motion in superconducting mater
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ials, it is shown that the transfer of thermal energy has two directional features of metallic and semiconductor heat conductions which are controlled by electron motion and atomic vibration, respectively. At temperatures lower than the critical temperature, heat is conducted mainly through the atomic vibration. When the size of material grains or thin films is of the order of the correlation length of atomic vibration, the temperature shows great jumps at these boundaries as in the radiation heat transfer. These size effects occur more easily at lower temperatures even for large scale circuits.
2. Thermal interactions of high-temperature superconducting elements : In order to make high-density integrated circuits of superconducting and/or semiconducting materials in hybrid systems, which have strong directionality of heat conduction, detailed knowledge is required of the thermal interaction between the circuit elements. At the boundaries of film elements, the atomic vibration and electron motion are to be dispersed, reflected and transmitted, and the heat conduction both in the film thickness direction and along the film is greatly affected by the boundaries. For superconducting materials, these features are controlled by the boundary effects of atomic vibration and electron motion at lower and higher temperatures than the critical temperature, respectively. The size of grains or film thickness at which these effects are dominated is of the order of 100nm, being increased inversely proportional to the third and fourth power of temperature for metal-like and semiconductor-like heat conduction, respectively. The features decide the thermal limit of integration circuit in size and density.
3. Thermal and electromagnetic interaction between circuit elements : The critical electric current dominates the stability of superconduction, being a function of the temperature and the associated magnetic field. The critical current is determined by the area integration of the local critical current density in the cross section normal to the current. The temperature field can be predicted by considering both the thermal features of directional heat conduction and the boundary effects. For a simple system of integrated system, the computation result shows that the size and configuration effects control the thermal limit of the integration. Less
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