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Thin microcrystalline films of the metastable semiconducting alloy Ge1−xSnx (x≊0.22) have been formed using excimer laser radiation to crystallize amorphous sputtered films on glass and semiconducting crystalline substrates. X-ray diffraction, electroreflectance, and Raman spectroscopy have been used to characterize the semiconducting material which is stable to at least 200 °C. The study demonstrates the possibility of extending earlier studies of amorphous Ge1−xSnx alloys into a crystalline regime with a direct band-gap variable with x from 0 up to about 0.5 eV. The crystallization technique is potentially applicable to the formation of other metastable semiconducting compounds of device potential.

Hydrogen evolution from annealed samples of amorphous silicon-hydrogen alloys (a-Si:H} is discussed. From the results of isothermal-annealing experiments, it is demonstrated that at fairly low temperatures (T =225 'C} the ratelimiting step for hydrogen evolution is a singly activated desorption process with a free energy of activation of 1.7 eV. We show that this low-temperature evolution is not limited by the diffusion of hydrogen through the silicon network. For this low-temperature desorption process, we measure in isochronal-annealing experiments an activation enthalpy of 0.4 eV and an activation free energy of 1.7 eV. Approximately one third of the hydrogen in a-Si:H resides in the relatively weakly bound states investigated in these low-temperature evolution studies. Also observed is the evolution of hydrogen associated with crystallization that occurs near 600 'C, and (in some samples} an intermediate temperature desorption process near 500 'C that involves a free energy (enthalpy} of activation of 2.4 (1.6}eV.

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We report measurements of infrared (ir) vibrational absorption made on thin films of rf-sputtered a-Si:H bombarded with 100and 200-keV He+ ions, and also after an anneal at temperatures up to 320 'C. We find that the integrated intensities of ir vibrational bands at 2000 and 850 cm ' are enhanced significantly after the bombardment, whereas bands at 2100, 890, and 650 cm ' show little change. Annealing at 320'C reduces the integrated intensities of the 2000and 850-cm peaks, again with little change in the other peaks, thus reversing the effect of bombardment. We explain these observations in terms of changes in the oscillator strengths of the vibrational modes induced by defects created near the vibrating complex during bombardment. The significance of the dependence of the ir oscillator strengths on the local defect structure and its implications for the interpretations of ir spectra are discussed.