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Science 19 January 2007:
Vol. 315. no. 5810, p. 297
DOI: 10.1126/science.315.5810.297d
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Materials with low thermal conductivity are not only useful as thermal barriers but thermoelectric energy conversion. Chiritescu et al. (p. 351, published online 14 December; see the Perspective by Goodson) find that when tungsten selenide, a layered material similar to graphite in the weakness of attraction between its layers, is grown from alternating thin films of W and Se, the sheets stack in a random manner. This disordering, coupled with the high in-plane ordering of the layers, leads to an extremely low crossplane thermal conductivity for a fully solid film--as low as 0.05 watts per meter per kelvin at room temperature, or 30 times less than the c-axis thermal conductivity of single-crystal WSe2. Disruption of the in-plane ordering by ion bombardment actually increased the thermal conductivity of the material.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)