In laser-induced semiconductor processing, two features are commonly observed in the semiconductor surface. The ﬁrst feature is pit formation, which occurs due to the presence of defects in
semiconductors (1). When a high-power laser pulse interacts with the semiconductor surface, the temperature of the semiconductor surface rises enough to make possible the movement of defects.
Through these movements, defects accumulate to form pits.
In the work of Amit Pratap Singh, a mathematical expression that includes the effect of pit formation as well as surface
roughness has been deduced. In the light of the above discussion, the following conclusions have
been drawn:(i) The presence of pits and surface roughness reduces the thermal conductivity of thin ﬁlms.
(ii) The net thermal conductivity is less for comparatively thin ﬁlms. This reduction in the value
of net thermal conductivity is more visible when there are comparatively fewer numbers of
pits on the ﬁlm.
(iii) The size effect on net thermal conductivity is more prominent when the ﬁlm is smooth.
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With an aperture size of 7.3 meters, the concentration factor of the new 275 kilowatt Sunray system is over 100 times that of normal sunlight. The 3M panels are half the weight of glass panels and provide 94.5 percent reflectivity, with testing of the performance confirmed by NREL, the U.S. National Renewable Energy Lab.
Read more: http://www.pv-magazine.com/news/details/beitrag/3m-and-gossamer-start-up-largest-aperture-parabolic-trough-_100006630/#ixzz1uZFwsQmJ
Singh, A. (2011). Effect of pit formation and surface roughness on size-dependent thermal conductivity of nanometer-thick semiconducting films. Radiation Effects & Defects In Solids, 166(1), 44-49. doi:10.1080/10420150.2010.493176