The work deals with studies of the grain size and surface state effect on photoelectric and transport properties of
PbTe(In) films in the temperature range from 4.2 K up to 200 K under irradiation of a blackbody source and terahertz
laser pulses. The PbTe(In) films were deposited on insulating substrates kept at the temperatures TS equal to -120 (see manuscript)
250C. AFM, SEM, Auger spectroscopy and X-ray diffraction were used to study the film microstructure. Increase of the
TS value led to mean grain size growth from 60 up to 300 nm. All films had a column-like structure with the columns
nearly perpendicular to the substrate plane. It is shown that microstructure of the films strongly affects the
photoconductivity character in the terahertz region of the spectrum. Positive persistent photoresponse is observed at low
temperatures in the polycrystalline films. For these films transport and photoelectric properties are determined by the
grain volume and impurity state specifics. Nanocrystalline films have all features of non-homogeneous systems with
band modulation. For these films only negative photoconductivity is observed in the whole temperature range. Possible
mechanisms of the photoresponse formation are discussed.
Photoelectric, transport and optical properties are studied for nanostructured PbTe(In) films. Synthesis of the films was
performed using evaporation of a target source to a glass substrate. The films have column-like structure with a mean
grain size varying from about 60 nm to 170 nm depending on the substrate temperature. Analysis of the data obtained
revealed that the conductivity of the films is determined by two mechanisms: charge transport along the inversion
channels at the grain surface and activation through barriers at the grain boundary. Persistent photoconductivity appears
in the films below T = 150 K. The frequency dependence of the relative photoresponse has a pronounced maximum. The
photoresponse in the ac mode may be by two orders of magnitude higher than in the dc measurements.
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