The subject of photoacoustic spectroscopy is reviewed. The basic areas of instrumentation (excitation sources, acoustic cells, and acoustic detectors) are described, and the specific advantages of various designs and techniques are discussed. Results are presented to highlight the applicability of photoacoustic spectroscopy to a wide variety of spectroscopic measurements. Applications include: linear absorption spectroscopy (vibrational and electronic), reaction kinetics, vibrational overtone spectroscopy, trace analysis, and nonlinear spectroscopy (multiphoton and stimulated Raman scattering). Special emphasis is given to photoacoustic Raman spectroscopy (PARS) and its application to gaseous trace component analysis.
We have deposited polycrystalline cobalt silicide films by chemical vapor deposition using Co2(CO)8 or HCo(CO)4 as the Co source and SiH4 or Si2H6 as the Si source. The Co:Si ratio of the films is controlled by changing the deposition temperature, and CoSi2 stoichiometry is obtained at 300 °C using SiH4 or at 225 °C when Si2H6 is the Si precursor. Carbon or oxygen contamination of the films is <0.5 at. % at deposition temperatures above 200 °C. Resistivities of films deposited near CoSi2 stoichiometry are typically 200 μΩ cm and drop to 40 μΩ cm upon annealing at 900 °C.
We have produced thin photoluminescent films of Eu-doped Y 2 O 3 (Y 2 O 3 : Eu) by low-pressure metalorganic chemical vapor deposition (MOCVD). Yttrium and europium j3-diketonate precursors are thermally decomposed in a hot-walled MOCVD reactor in the presence of oxygen at a total reactor pressure of 1 Torr. The films are microcrystalline and photoluminescent as-deposited and contain <1 at.% of carbon contamination. Subsequent annealing at 1200 °C in air enhances and stabilizes the luminescence. We have measured the photoluminescent lifetimes of the MOCVD films as a function of temperature for the Eu +3 5 £>i -> 7 Fi and 5 D 0 -» 7 F 2 transitions using excimer laser excitation at 248 nm. We present a kinetic model which can account for the observed emission lifetimes from 20-1000 °C.
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