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ABSTRACT: Porous layers have been obtained by electrochemical etching of n-type III-V semiconductor single crystals (GaAs, InP, and GaP) in water or the ethanol solutions of different acids. The InP porous layers have been shown a more ordered and perfect structure than those of GaP and GaAs. Metal inclusions have been incorporated into the porous layers in an electrochemical cell from an aqueous solution of the Au salt. As found, phonon band intensities are significantly increased in the porous region. The homogeneity of the porous layers prepared has been reliably proved by the Raman micro-spectroscopic mapping of their fresh cleavages. The incorporation of gold into pores leads to a stronger Raman signal of the TO and LO modes, especially in the two-phonon absorption region, and also significantly enhances the photoluminescence of porous layers.
XXI INTERNATIO NAL MATERIALS RESEARCH CONGRESS 2012, Cancun, Mexico; 08/2012
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ABSTRACT: We present the results of comparative investigations of the effect of a direct solvent-free modification of C60 thin films with photosensitive molecules: aminosubstituted polycyclic aromatic hydrocarbons (1-aminopyrene, 1-pyrenemethylamine hydrochloride, 1,5-diaminonaphthalene) and meso-tetraphenylporphine on their optical properties, photoluminescence, and photoelectric characteristics of Au/C60/Si photodiode structures (λ = 400–1100 nm). The optical properties (n, k) of the investigated C60 films are shown to differ slightly. The photoluminescence spectra measured at 2 K demonstrate a redistribution of the constituent bands intensities and their overall reduction for all C60 modifications. The greatest enhancement of the photocurrent and the photoconversion efficiency is observed for structures with C60 layers modified with meso-tetraphenylporphine.
Molecular Crystals and Liquid Crystals 01/2011; 535(1):10-17. · 0.58 Impact Factor
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ABSTRACT: A detailed optical and photoelectric characterization of pristine fullerene C60 films deposited onto n-silicon substrates (C60/Si), C60 films crosslinked by means of the solvent-free chemical functionalization with 1,8-diaminooctane (C60-DA/Si), and the pristine and crosslinked films decorated with silver nanoparticles (C60-Ag/Si and C60-DA-Ag/Si), was carried out. The reflectance spectra obtained allowed to calculate the absorption coefficient (alpha = 4pik/lamda) spectral dependencies and the spectra of light transmittance in layered barrier structures metal(Au)/fullerene/Si. Photoelectric properties of the films were investigated as well. The experimentally measured values of band gap were in a good agreement with mobility gap values (2.3 +/- 0.1 eV). The decoration of fullerene films (both pristine and chemically crosslinked) with silver nanoparticles did not change the photocurrent spectra as compared to those for undecorated fullerene films, but lowered the values of internal quantum efficiency Qint. The photocurrent generated in fullerene/Si heterostructure, showed a maximum value at lamda to appromimately 450 nm (Qint max approximately = 0.25 for decorated and undecorated C60-DA/Si films), and it was higher for the samples based on pristine C60 films, in accordance with their higher absorption coefficient. Diminishing of Qint for C60-DA/Si and C60-DA-Ag/Si films was observed for the spectral range of photocurrent generated in Si layer. The analysis of dark current-voltage characteristics showed that the barrier properties differ insignificantly, though a certain increase of series resistance was observed for the C60-DA/Si samples.
Journal of Nanoscience and Nanotechnology 12/2008; 8(11):5958-65. · 1.56 Impact Factor
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ABSTRACT: A detailed optical and photoelectric characterization of pristine fullerene C60 films deposited onto n-silicon substrates (C60/Si), C60 films crosslinked by means of the solvent-free chemical functionalization with 1,8-diaminooctane (C60-DA/Si), and the pristine and crosslinked films decorated with silver nanoparticles (C60-Ag/Si and C60-DA-Ag/Si), was carried out. The reflectance spectra obtained allowed to calculate the absorption coefficient (α = 4pik/λ) spectral dependencies and the spectra of light transmittance in layered barrier structures metal(Au)/fullerene/Si. Photoelectric properties of the films were investigated as well. The experimentally measured values of band gap were in a good agreement with mobility gap values (2.3±0.1 eV). The decoration of fullerene films (both pristine and chemically crosslinked) with silver nanoparticles did not change the photocurrent spectra as compared to those for undecorated fullerene films, but lowered the values of internal quantum efficiency Qint. The photocurrent generated in fullerene/Si heterostructure, showed a maximum value at λ ∼450 nm (Qint max≈0.25 for decorated and undecorated C60-DA/Si films), and it was higher for the samples based on pristine C60 films, in accordance with their higher absorption coefficient. Diminishing of Qint for C60-DA/Si and C60-DA-Ag/Si films was observed for the spectral range of photocurrent generated in Si layer. The analysis of dark current-voltage characteristics showed that the barrier properties differ insignificantly, though a certain increase of series resistance was observed for the C60-DA/Si samples.
Journal of Nanoscience and Nanotechnology 10/2008; 8(11):5958-5965. · 1.56 Impact Factor
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ABSTRACT: The effect of texturing interfaces on the optical and photoelectric properties of anisotype and isotype organic (OS)/inorganic (IS) semiconductor heterojunctions has been investigated. p-(Pentacene) and n-(methyl perylene pigment, MPP) type organic semiconductor layers were evaporated on n-GaAs and p-InP substrates, respectively, with flat substrates and the substrates textured by chemical anisotropicetching (with a microrelief of the quasigrating type). The spectra of the light reflectance and the short-circuit photocurrent for the Au/OS/IS heterostructure were measured and analyzed to distinguish the contribution of the photocurrent generated in the OS layer. A considerable enhancement of the photocurrent generated in both inorganic and organic semiconductors was found for structures with textured interface.
Molecular Crystals and Liquid Crystals 01/2008; 496(1):118-130. · 0.58 Impact Factor
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ABSTRACT: A comparative characterization Of C-60 thin films grown on silicon substrate by Physical Vapor Deposition and polymerized by chemical reaction with 1,8-octanediamine vapor or UV Pulsed laser irradiation has been carried out by means of Atomic Force Microscopy, and optical reflectance, transmittance and photoluminescence spectroscopies. The photovoltaic response and electrical characteristics of AU/C-60/Si diode structures have been investigated. The greatest photoluminescence efficiency and light transmittance, and at the same time the least photocurrent of diode structure were observed for chemically polymerized C60. Found differences in morphology, optical, photoelectric and electrical properties Of C60 films polymerized by two methods indicate a difference in their composition. (c) 2006 Elsevier B.V. All rights reserved.
Thin Solid Films. 01/2007; 515(19):7716-7720.
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ABSTRACT: Optical and photoelectrical studies were performed on octane-1,8-dithiol cross-linked fullerene films, with supported gold nanoparticles (C60–DT–Au). According to high-resolution transmission electron microscopy observations, the average size of obtained gold nanoparticles was about 5 nm, and the shape was spherical. The comparative investigation of optical properties of pristine and cross-linked with octane-1,8-dithiol C60 films, decorated with gold nanoparticles, found the difference in the extinction coefficient spectra, which was observed also in the photocurrent spectra of barrier heterostructure Au/C60/Si. The analysis of dark current–voltage characteristics for Au/C60/Si heterostructures showed that the model for them includes the barrier at the C60/Si interface and internal barriers in the C60 layer, caused by the trapping centers. The hopping mechanism of the current transport in the C60 layer was supplemented with the Poole–Frenkel emission process on these centers, with the barrier height greater for the fullerene C60 film cross-linked with octane-1,8-dithiol.
Thin Solid Films.
