Physics

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End date: 1989Has files: Yes

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    n-type electrical conductivity in cuprous oxide thin films
    (Natural Resources, Energy and Science Authority of Sri Lanka, 1988) Siripala, W.; Kumara, K.P.
    Electrodeposited cuprous oxide thin films were investigated to determine whether their electrical conductivity is n-type or p-type. The experimental results based on the measurements of thermoelectric e.m.f, sheet resistance, dark and light current-voltage characteristics of Cu2O/CuxS and Cu2O/CuCNS heterojunctions reveal that the electrodeposited cuprous oxide films produce n-type electrical conductivity. These observations are in very good agreement with the previously reported n-type behavior of the electro-deposited Cu2O film electrodes in a photo-electrochemical cell.
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    Electrolyte Electroreflectance of Single-Crystal CdIn2Se4 in a Photoelectrochemical Solar Cell
    (Journal of Electrochemical Society, 1984) Tomkiewicz M; Siripala W
    Electroreflectance was used to evaluate the optical properties of in polysulfide solution, before and after photoetching. The variations of signal intensity with electrode potential were used to trace the band position as a function of potential. It was found that the optical transition fits a three?dimensional parabolic model of the density of states, with direct transition at 1.825 eV. When the crystal is photoetched, there is a shift of 98� in the phase factor and a decrease in the broadening parameter from 0.42 to 0.32 eV. By monitoring the signal intensity with potential, it was shown that, irrespective of photoetching, the Fermi level is pinned as reverse bias conditions are approached. The pinning is ascribed to surface states that most likely originate from the adsorption of the electrolyte. The variation of the flatband potential with electrode potentials was calculated and was determined to occur because of the changes in the potential of the Helmholtz layer; the energy distribution and the density of states, which are responsible for those changes in potential of the Helmholtz layer, were also calculated.
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    Interactions Between Photoinduced and Dark Charge Transfer across n-TiO[sub 2]Aqueous Electrolyte Interface
    (Journal of Electrochemical Society, 1982) Siripala W; Tomkiewicz M
    An intermediate of the dark reductive reaction of with an aqueous electrolyte was identified. This intermediate forms surface states on the semiconductor. The energy and surface concentration of these states were evaluated by impedance measurements. We report on sub?bandgap photoresponse due to excitation of electrons from the valence band to these states. The potential?photocurrent behavior of these states is unique and is being fully accounted for by the proposed mechanism of their dynamic formation and annihilation.
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    Observation of Intrinsic Surface States at the TiO2 Aqueous-Electrolyte Interface by Sub Band-Gap Electroreflectance Spectroscopy
    (Physical Review Letters, 1983) Siripala W; Tomkiewicz M
    Surface states were detected with sub?band-gap electroreflectance spectroscopy in the presence of electrolytes that can adsorb on the surface of TiO2. The energy of these states is located 1.3 eV below the conduction band and they can be detected only in the weak accumulation mode. The potential distribution at the interface as a function of the electrolyte was investigated by impedance spectroscopy. These results were interpreted in terms of "intrinsic" surface states of the unsolvated surface.