AuthorRock, David Franklin
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractA study was made of the thermoreflectance spectra of a series of five thin film samples spanning the range of composition of the amorphous Ge(x)Te(1-x) binary semiconductors. The experiment was performed over photon energies ranging from 0.5 ev in the infrared to 6 ev in the ultraviolet. The results are plotted for energies above the absorption edge. In the Ge-rich materials there was little structure in the thermoreflectance spectrum. However, there was the development of two peaks in the spectrum as the Te content was increased beyond a 50:50 mixture. The results are analyzed in terms of optical constants and electronic structure. It was found that the energy separation of the peaks in the thermoreflectance corresponded closely to the separation of peaks in the valence band density of states seen in photoemission experiments. The existence of the two peaks indicates a "lone pair" band of energy levels positioned between the valence and conduction bands. This is aditional evidence of two-fold coordination of the Te atoms in these materials. At energies below the band gap there was strong interference due to increased transimission of the film. This made the analysis more complicated. A procedure is discussed for extracting from the modulated interference the specific changes occurring in the optical constants with temperature modulation.
Degree ProgramOptical Sciences