David D. Allred received Alumni Professorship Award

Raman spectroscopy (RS) and low-angle x-ray diffraction (LAXRD) have been used to characterize semiconductor multilayer interfaces. In the present study a model for Raman spectra of multilayers is developed and applied to the specific case of the interfaces of a-Si/a-Ge multilayers. Quantification of the “blurring” of interfaces is possible because peak heights in the Raman spectra of thin films are proportional to the number of scatterers, thus RS is capable of directly “counting” the total number of chemical bonds of a given type in the film. Multilayers, prepared by various deposition techniques, are compared. The relative roles of LAXRD and RS in investigating interfaces are contrasted. Several a-Si/a-Ge multilayers deposited by ultra-high vacuum (UHV) evaporation (MBD) are found to exhibit very regular periodicities and exceptionally sharp interfaces (<1.0 Å intermixing).

Chemical Vapor Deposition (CVD) is a versatile and efficient technique for thin film deposition in the microelectronics, electro-optics, tool and protective coatings industries. This technology has been adapted by several groups to the preparation of optical thin films. We report on several CVD thin films stacks for photothermal solar energy conversion which combine promising spectral selectivity and durability at elevated operating temperatures.