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Journal of Nanomaterials
Volume 2014, Article ID 578758, 8 pages
http://dx.doi.org/10.1155/2014/578758
Research Article

Study on the Cross Plane Thermal Transport of Polycrystalline Molybdenum Nanofilms by Applying Picosecond Laser Transient Thermoreflectance Method

1College of Mechanical and Transportation Engineering, China University of Petroleum, Beijing 102249, China
2Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
3International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan
4Department of Mechanical Engineering, Kyushu University, Fukuoka 819-0395, Japan
5Department of Aeronautics and Astronautics, Graduate School of Engineering, Kyushu University, Fukuoka 819-0395, Japan

Received 19 February 2014; Revised 17 May 2014; Accepted 27 May 2014; Published 18 June 2014

Academic Editor: Theodorian Borca-Tasciuc

Copyright © 2014 Tingting Miao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Thin metal films are widely used as interconnecting wires and coatings in electronic devices and optical components. Reliable thermophysical properties of the films are required from the viewpoint of thermal management. The cross plane thermal transport of four polycrystalline molybdenum nanofilms with different thickness deposited on glass substrates has been studied by applying the picosecond laser transient thermoreflectance technique. The measurement is performed by applying both front pump-front probe and rear pump-front probe configurations with high quality signal. The determined cross plane thermal diffusivity of the Mo films greatly decreases compared to the corresponding bulk value and tends to increase as films become thicker, exhibiting significant size effect. The main mechanism responsible for the thermal diffusivity decrease of the present polycrystalline Mo nanofilms is the grain boundary scattering on the free electrons. Comparing the cross plane thermal diffusivity and inplane electrical conductivity indicates the anisotropy of the transport properties of the Mo films.