jueves, 10 de mayo de 2012

Nanometer. thick films.. making the imposible

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.

One of the newst application is in the solar cell, like the 3M .In the bulletin at the news they said "3M has started up what it says is the world's largest aperture solar parabolic trough, in partnership with Gossamer Space Frames, as an addition to the 400-acre Sunray Energy facility in Daggett, California, formerly known as the SEGs I and II plants"

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.

Singh, A. (2011). Effect of pit formation and surface roughness on size-dependent thermal conductivity of nanometer-thick semiconducting films. Radiation Effects & Defects In Solids166(1), 44-49. doi:10.1080/10420150.2010.493176

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