Chemical Bath Deposited PbS(Th) Thin Films for Infrared Detection

Nitzan Maman ¹ Tzvi Templeman ^2,3 Michael Shandalov ⁴ Sucheta Sengupta ² Alexander Rabkin ² Yuval Golan ^2,3 Iris Visoly-Fisher ^1,2

¹Solar Energy and Environmental Physics, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein
²Ilse Katz Institute for Nano-scale Science and Technology, Ben Gurion University of the Negev
³Department of Materials Engineering, Ben Gurion University of the Negev
⁴Department of Physics, Nuclear Research Center Negev

The electronic and optical properties of PbS(Th) films with nano-spherical morphology deposited on GaAs(100) substrates were studied in order to determine their potential use as SWIR absorber material for upconversion night vision devices. The films were grown by chemical bath deposition during which small concentrations of Th⁺⁴ cations were incorporated, The films demonstrated quantum confinement effects, in which the band gap increases with Th at%.

FTIR transmission measurements showed a strong absorption band at 1.8 µm for films containing ~8 at% Th. Several absorption states in the forbidden gap were monitored as a function of post-deposition thermal treatment parameters such as temperature, duration and atmosphere.

Photoconduction measurements were performed on these films in the dark and under SWIR illumination (nm, 5mW) as a function of film thickness and different thermal treatments. The resistivity of the films was found to decrease by more than 50% under SWIR illumination compared to dark resistivity.