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- Photoconductivity kinetics of indium sulfofluoride thin films starPublication . Vygranenko, Yuri; Fernandes, Miguel; Vieira, Manuela; Lavareda, Guilherme; CARVALHO, CARLOS; Brogueira, Pedro; Amaral, AnaIndium sulfofluoride is an amorphous wide-gap semiconductor exhibiting high sensitivity to UV radiation. This work reports on the kinetics of photoconductivity in indium sulfofluoride thin films along with their electrical and optical properties. The films were deposited by radio-frequency plasma-enhanced reactive thermal evaporation. The film characterization includes electrical, optical, and photoconductivity measurements. The films are highly transparent in the visible-infrared range due to an indirect bandgap of 2.8 eV. The spectral response measurements have revealed existence of the band tail states. The synthesized compound is highly resistive (similar to 200 M ohm-cm at 300 K) and exhibits extremely slow photocurrent relaxations. Photoconductivity kinetics was studied under various excitation conditions. A dependence of the photocurrent on the incident photon flux was also determined.
- Conducting indium oxide films on plastic substrates by plasma enhanced reactive thermal evaporationPublication . Vygranenko, Yuri; Fernandes, Miguel; Vieira, Manuela; Lavareda, Guilherme; CARVALHO, CARLOS; Brogueira, P.; Amaral, AnaThis work reports on low temperature deposition of conducing indium oxide films by a radio-frequency plasma enhanced reactive thermal evaporation (rf-PERTE) technique. The films were deposited on polyethylene terephthalate (PET) without intentional heating of the substrate and at elevated temperatures up to 150 degrees C. The material stoichiometry was accurately controlled by adjusting deposition conditions including the oxygen flow, process pressure, pumping speed, and RF-power. Besides, fine turning of the critical deposition parameters during the deposition was implemented by measuring the variation of film conductance in-situ. The film morphology was analyzed by scanning electron microscopy. Hall effect measurements were also performed to determine the relation between the deposition conditions and the electrical properties of the films. A resistivity of 4 x 10(-4) Omega-cm was reached under optimized deposition conditions. A 250 nm-thick coating with 16 Omega/sq sheet resistance shows an 82% peak value of transmittance in the visible spectral range.
- Electrical, optical and photoconductive properties of Sn-doped indium sulfofluoride thin filmsPublication . Vygranenko, Yuri; Fernandes, M.; Vieira, Manuela; Lavareda, G.; Carvalho, C. Nunes De; Brogueira, P.; Amaral, A.; Barradas, N. P.; Alves, E.This work reports on undoped and Sn-doped indium sulfofluoride thin-films deposited by radio-frequency plasma-enhanced reactive thermal evaporation. The deposition was performed evaporating pure indium or indium-tin alloy in SF6 plasma at substrate temperatures ranging from 373 to 423 K. Rutherford backscattering analysis and secondary-ion mass spectrometry were used to determine the chemical composition of the films. The film characterization includes electrical, optical, and photoconductivity measurements. The resistivity of undoped material varies in a wide range of 1 G Omega-cm to 2 T Omega-cm depending on deposition conditions. Sn doping leads to a decrease in the resistance down to 8 M Omega-cm. The films are highly transparent in the visible-infrared region due to an indirect bandgap of 2.7-3 eV. Moreover, the doped material is highly photosensitive in the blue -UV region. Photoconductivity kinetics under various excitation conditions was also studied. The synthesized material is a promising candidate for a buffer layer in chalcogenide-based solar cells.