Results of experiments studying the utilization of adaptive CdTe:V photoelectromotive force (photo-EMF) detector for high-sensitivity broadband detection of laser-generated ultrasound are presented. Unlike widely used GaAs photo-EMF detectors, the devices used here demonstrate no significant electron-hole competition. This ensures effective detection of ≅1 nm surface displacements with ≅0.1 mW of the signal beam power in 10 MHz detection frequency band, even in simple transverse detector configuration. For the wavelength of λ=852 nm used in the experiments, the dielectric cutoff frequency of a typical device was approaching 1 MHz. This, in principle, enables monitoring of as-processed objects moving with in-plane velocities up to 10 m/s.
A modified mass loss measurement technique has been employed, for the first time, for the direct in situ determination of vacancy concentrations in Hg0.~Cdo.2Te at elevated temperatures. This technique can also be used to establish the pressure-temperature phase diagram for this type of systems. The derived mean value for the heat of formation of mercury vacancies in the above alloy is 0.43 eV. Theoretical considerations concerning the vacancy formation in HgTe and in Hg0.sCd0.2Te are in qualitative agreement with our experimental value.
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