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Optical properties of nanostructured mesoporous semiconductor films

Iris Nandhakumar 

University of Southampton, Department of Chemistry, Southampton SO17 1BJ, United Kingdom

Abstract

Nanostructuring of semiconductors and metals is now a clear route to optimise and elicit new functional properties, e.g. allowing quantum engineering of electron and photon states. Hence materials with mesoporous nanoarchitectures (2–50 nm) exhibit novel electronic, optical and magnetic properties in comparison to their non-mesoporous counterparts. Recently we have devised an elegant and highly versatile route to the production of a wide range of nanostructured materials with well-defined mesoporous architectures of extended spatial periodicities. This method utilises lyotropic liquid crystalline (LC) mesophases of non-ionic surfactants as templates for electrochemical growth. Here we report the fabrication of adherent nanostructured semiconductor films such as cadmium telluride and lead telluride that have been fabricated by this method. Our results indicate that nanostructuring produces strong birefringence for wavelength both above and below the bandgap of the mesoporous semiconductor films. These exciting results show that electrodeposition from LC phases can be used to access a wide range of Group VI, II-VI and related semiconductor films (e.g. CdSe, CdS, PbSe). Such materials would be of considerable fundamental interest because they are entirely composed of surface atoms (no atom in the structure is further than 1.5 nm from a surface). As a consequence we expect that these materials should exhibit unusual charge carrier dynamics, improved collection of the photogenerated carriers and hence solar conversion efficiencies. Nanostructured semiconductors will show quantum size effects by virtue of their reduced dimensionality and nanometre lengthscales (from 2 to 15nm). The ability to electrodeposit mesoporous nanostructured semiconductors highlights the possibility of creating a new class of materials that would exhibit unusual electronic and optical properties.

 

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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium B, by Iris Nandhakumar
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-20 18:38
Revised:   2009-06-07 00:44