Structure, surface composition, and electronic properties of CuInS2 and CuIn(1-x)AlxS2

International audienceCuInS2 and CuIn(1-x)AlxS2 thin films have been deposited on different substrates using the spray pyrolysis technique at 320 degreesC. X-ray diffraction, atomic force microscopy, and scanning electron microscopy were used to characterize the structure of the films; the surface compositions of the films were studied by Auger electrons spectroscopy and energy dispersive spectrometry (EDS), the work function and the photovoltage by the Kelvin method. Using these techniques, we have specified the effect of the nature of the substrate, its surface morphology, and the introduction of small amounts of Al in the layer on the properties of the films. The best crystallized composition of CuInS2 was obtained for deposits on pyrex. This was improved by the introduction of Al atoms. The work function differences (phi(material)-phi(probe)) for CuInS2 and CuIn(1-x)AlxS2 deposited on pyrex were equal to -350 meV and to -400 meV, respectively. Putting Al atoms in the film increases phi(m) (by about 50 meV) and induces the formation of a negative surface barrier. The best composition was obtained for CuInS2 deposited on SnO2 and annealed. Auger studies shows that the concentration of S and C elements increased when the samples were annealed under a vacuum, whereas the concentration of Cu, In, and O decreased. In the case of CuInS2 grown on pyrex, the introduction of Al increases the O, S, and Cl concentrations and reduces Cu and C concentrations. Analysis of the film compositions by EDS gives the following concentrations [Cu]=24.270%, [In]=24.487%, [S]=46.670%, and [Cl]=4.573%. (C) 2002 American Institute of Physics

Structure, surface composition, and electronic properties of beta-In2S3 and beta-In2-xAlxS3

International audiencebeta -In2S3 and beta -In2-xAlxS3 thin films have been deposited on different substrates using the spray pyrolysis technique at 320 degreesC. X-ray diffraction, atomic force microscopy, and scanning electron microscopy were used to characterize the structure of the films; the surface compositions of the films were studied by Auger electrons spectroscopy and energy dispersive spectrometry (EDS), the work function and the photovoltage by the Kelvin method. Using these techniques, we have specified the effect of the nature of the substrate, of its surface morphology, of the introduction of small amounts of Al in the layer, on the properties of the films. The best crystallized of beta -In2S3 were obtained for deposits on pyrex. This was improved by the introduction of Al atoms. The work function differences (phi (material)-phi (probe)) for beta -In2S3 and beta -In2-xAlxS3 deposited on steel were equal to -150 meV and to -180 meV, respectively. Putting Al atoms in the film increases phi (m) (by about 30 meV) and induces the formation of a negative surface barrier. The concentration of In, S, and O elements increased when the samples were annealed under a vacuum, whereas the concentration of carbon decreased. The best composition was obtained for In2S3 deposited on SnO2 and annealed. The introduction of Al increases O and C concentrations and reduce In, Cl, and S concentrations. Analysis of the film compositions by EDS gives the following concentrations [In]=37%, [S]=52%, and [Cl]=11%. (C) 2001 American Institute of Physics

Magnetic field induced alignment of cyanine dye J-aggregates

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Optical second-harmonic generation and scanning tunneling microscopy study of the self-assembly process of cyanine dyes on Br-Ag(111) substrates

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Image calculations with a numerical frequency-modulation atomic force microscope

cited By 6International audienceWe investigated the implementation of a numerical tool able to mimic an experimental noncontact atomic force microscope (nc-AFM). Main parts of an experimental setup are modeled and are implemented inside a computer code. The goal was to build a numerical AFM (n-AFM) as versatile, efficient, and powerful as possible. In particular, the n-AFM can be used in the two working regimes, that is, in attractive and repulsive regimes, with settings for a standard AFM cantilever oscillating with a large amplitude (typically, 10 nm) or for a tuning-fork probe with ultrasmall amplitudes (∼0.01 nm). We present various tests to show the reliability of the n-AFM used as a frequency-modulation AFM (FM-AFM). As an example, we calculated FM-AFM images of adsorbed molecular systems, which range from two-dimensional planar molecules to corrugated systems with a three-dimensional molecule. The submolecular resolution of the FM-AFM is confirmed to originate from repulsive Pauli-like interactions between the tip and the sample. The versatility of the n-AFM is finally discussed in the perspective of new functionalities that will be included in the future