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Unformatted text preview: Molecular dynamics simulations of carbon nanotube/silicon interfacial thermal conductance Jiankuai Diao, 1, a ! Deepak Srivastava, 1, b ! and Madhu Menon 2, c ! 1 University Affiliated Research Center, University of California, Santa Cruz and NASA Ames Center for Nanotechnology, Moffett Field, California 94035, USA 2 Department of Physics and Astronomy, and Center for Computational Sciences, University of Kentucky, Lexington, Kentucky 40506, USA s Received 25 January 2008; accepted 8 March 2008; published online 22 April 2008 d Using molecular dynamics simulations with Tersoff reactive many-body potential for Si–Si, Si–C, and C–C interactions, we have calculated the thermal conductance at the interfaces between carbon nanotube s CNT d and silicon at different applied pressures. The interfaces are formed by axially compressing and indenting capped or uncapped CNTs against 2 3 1 reconstructed Si surfaces. The results show an increase in the interfacial thermal conductance with applied pressure for interfaces with both capped and uncapped CNTs. At low applied pressure, the thermal conductance at interface with uncapped CNTs is found to be much higher than that at interface with capped CNTs. Our results demonstrate that the contact area or the number of bonds formed between the CNT and Si substrate is key to the interfacial thermal conductance, which can be increased by either applying pressure or by opening the CNT caps that usually form in the synthesis process. The temperature and size dependences of interfacial thermal conductance are also simulated. These findings have important technological implications for the application of vertically aligned CNTs as thermal interface materials. © 2008 American Institute of Physics . f DOI: 10.1063/1.2905211 g I. INTRODUCTION As the size of the electronic circuits in microprocessors decreases and their density increases, there is a correspond- ing increase in the heat generation. Metallic heat sink mate- rials such as copper are usually attached to electronic devices to help dissipate the heat generated in electronic devices into the environment. The thermal conductance at interfaces formed by bringing two solid surfaces that were originally separated into contact, however, is generally low due to the very low effective contact area s less then a few percent d at the interface. 1 This low effective contact area stems from the fact that solid surfaces are usually rough at the atomic level. To increase the effective contact area and thereby the inter- facial thermal conductance, thermal interface materials such as a thermal grease are commonly used in the electronic industry, e.g., in between microprocessor chips and heat sink materials....
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