Polycrystalline Antimony Research Articles

Electronic Conduction Mechanisms and Defects in Polycrystalline Antimony Selenide

A study of the electronic conduction mechanisms and electrically active defects in polycrystalline Sb2Se3 is presented. It is shown that for temperatures above 200 K, the electrical transport is do...

Observation of coherent optical phonons excited by femtosecond laser radiation in Sb films by ultrafast electron diffraction method

The generation of coherent optical phonons in a polycrystalline antimony film sample has been investigated using femtosecond electron diffraction method. Phonon vibrations have been induced in the Sb sample by the main harmonic of a femtosecond Ti:Sa laser (λ = 800 nm) and probed by a pulsed ultrashort photoelectron beam synchronized with the pump laser. The diffraction patterns recorded at different times relative to the pump laser pulse display oscillations of electron diffraction intensity corresponding to the frequencies of vibrations of optical phonons: totally symmetric (A1g) and twofold degenerate (Eg) phonon modes. The frequencies that correspond to combinations of these phonon modes in the Sb sample have also been experimentally observed.

Evidence of Induced Underpotential Deposition of Crystalline Copper Antimonide via Instantaneous Nucleation

was electrodeposited onto transmission electron microscopy (TEM) grids to investigate changes in morphology, composition, and crystal structure during the early stages of nucleation and growth. Multiple transitions were observed within the first second of the deposition, leading to the formation of crystalline . These transitions were analyzed using TEM, scanning electron microscopy, selected area electron diffraction, and energy-dispersive X-ray spectroscopy. The nucleation sites are initially polycrystalline antimony with amorphous copper, which then transition through a polycrystalline copper intermediate containing some antimony before forming crystalline . These analyses provide direct evidence that does not deposit directly from solution but deposits by induced underpotential deposition. This is indicative of the electrodeposition of a typical alloy initially, but what is unusual is that the deposit at longer time scales is a highly crystalline intermetallic. This investigation is unique because TEM grids allow the interface between the deposited material and the substrate to be investigated. This is possible because the composite carbon film on the TEM grid behaves as a transparent substrate. This approach can be extended to other systems, allowing the development of a comprehensive understanding of the electrodeposition of intermetallic compounds.

New approach for elucidating the oxygen sensitivity and calibration of the antimony electrode.

The biomedical use of the polycrystalline antimony pH electrode is hampered by oxygen dependence and low pH resolution (0.1 pH). Although, the pH resolution is improved by using highly purified crystallographically oriented monocrystalline antimony (COMA), the oxygen effect on the electrode remains. In an in vitro examination of the COMA electrode it was found that the oxygen dependence is similar to that of polycrystalline antimony, i.e. nonlinear with an increase in sensitivity below 10 kPa. These findings imply that the oxygen tension in the vicinity of a COMA pH electrode, has to be known or controllable for the pH reading to be at all valid especially at low oxygen levels, such as is often seen in biomedical applications. A calibration procedure using a zero oxygen solution is used in order to obtain absolute pH readings in a measurement solution of pre-set or known oxygen levels. Furthermore, the nonlinear oxygen sensitivity of the antimony electrode suggests that the underlying electrochemical reactions are other than those described by corrosion theory.

Initial oxidation of ultrathin antimony films on Au(111) and of polycrystalline antimony.

It has been shown previously that antimony evaporated onto a Au(111) surface grows in a layer-by-layer mode. The present work compares the initial, fast-oxidation stage of these films with that on bulk polycrystalline antimony. Measurements were carried out in an ultrahigh-vacuum environment using Auger electron spectroscopy, low-energy electron diffraction, electron-energy-loss spectroscopy, and work-function change measurements. At 300 K and for oxygen pressures between 1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ and 2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ Torr, oxidation follows first-order Langmuir kinetics, with an initial sticking probability of about ${10}^{\mathrm{\ensuremath{-}}5}$. Oxidation essentially saturates by ${10}^{7}$ L (1 L=${10}^{\mathrm{\ensuremath{-}}6}$ Torr s). A layer of oxide about 8.5 \AA{} thick is formed in this initial stage, both for Sb films and for bulk antimony. An initial antimony film on Au(111) of about 1.7 monolayers, or 1.6\ifmmode\times\else\texttimes\fi{}${10}^{15}$ atoms/${\mathrm{cm}}^{2}$, is required to complete this oxide layer, for saturation oxidation. The chemical composition of the oxidized films and the oxidized surface of bulk antimony is ${\mathrm{Sb}}_{2}$${\mathrm{O}}_{3}$. These results are compared with earlier work on Pb, Bi, and Sn.

Ellipsometric investigation of the growth mode of antimony overlayers on GaAs(110)

Antimony overlayers deposited on GaAs(110) surfaces prepared by cleavage in ultrahigh vacuum have been investigated by ellipsometric spectroscopy. Antimony films in the submonolayer coverage range exhibit spectral features arising from interband transitions. Films of up to 10ML (where ML denotes monolayer) thickness are of inhomogeneous consistency as demonstrated by comparison with calculations based on the Maxwell Garnett model. Slight annealing causes a smoothing of the films. Thicker films exhibit an optical behaviour like that of polycrystalline antimony.

Polycrystalline and monocrystalline antimony, iridium and palladium as electrode material for pH-sensing electrodes

Different ways of making pH-sensing electrodes from monocrystalline or polycrystalline antimony, iridium and palladium have been investigated. Monocrystalline antimony and iridium are superior to the polycrystalline elements with respect to reproducibility between electrodes and stability of the electrode potential over long periods of time. No good palladium/palladium oxide electrode could be obtained by electrochemical oxidation and the thermal preparation method could not take advantage of the properties of the monocrystalline palladium. Therefore, only polycrystalline palladium was used to study this type of electrodes. The different electrodes were compared with respect to the manner of preparation, the pH-response (reproducibility and time response) and the effect that different complexing ligands present in the measuring solutions may have on the electrode response. Also, the redox-response of the electrodes and the effect of different oxygen pressures on the electrode potentials were studied. The monocrystalline antimony electrodes have the best reproducibility and long-term stability but also respond to complexing ligands and to variations in the oxygen pressure. Monocrystalline iridium electrodes can be obtained by continuously cycling the potential between −0.25 and +1.25 V (SCE) in 0.5 M sulphuric acid. They do not respond to the complexing ligands tested, and have fairly good long-term stability, but the reproducibility between electrodes is inferior to that of the monocrystalline antimony electrodes. Polycrystalline antimony and iridium electrodes were inferior to the monocrystalline ones. The properties of the palladium electrodes were similar to those of the iridium ones.

The differential capacitance of polycrystalline antimony in aqueous solution

The results of measurements of the differential capacitance of the solid antimony/aqueous solution interphase for the electrolytes, HNO 3, H 2SO 4 and H 3PO 4 are presented. The electrode is not ideally polarisable. However an accessible experimental region exists from +0.3 to −0.5 V. The p.z.c. can only be estimated as −0.15 ± 0.1 V since the interphase is complicated by the adsorption of anionic and cationic species.

The surface re-orientation caused by undirectional abrasion on polycrystalline antimony

The surface re-orientation caused by undirectional abrasion on polycrystalline antimony