Single-crystal Indium Research Articles

Magnetoacoustic oscillations in indium due to the frequency dispersion

Abstract A detailed investigation of the recently disco vered magnetoacoustic oscillations of ellipticity has been undertaken in indium single crystals under the non-traditional mutual orientation of the magnetic field H and the ultrasound wave-vector q (close to H‖q). It has been found that oscillations appear in the field dependences of absorption and phase velocity of the circularly polarized ultrasonic waves, and also in those of ellipticity and the angle of rotation of the polarization piane. A description of the phenomenon observed has been given. The oscillations have been shown to be conditioned, unlike the Pippard geometrie oscillations, not only by spatial, but also by frequency dispersion. An analysis of the experimental data points to an electromagnetic nature of the oscillations discussed. Attention is drawn to opportunities to utilize the phenomena to determine the size of the cyclotron trajectory along the magnetic field and to recover the temperature dependence of the relaxation time for t...

A novel method for preparing thin films with selective doping in a single evaporation step

Thin films exhibiting high optical transmission, low emissivity for thermal radiations and good electrical conductivity have important applications, such as transparent electrodes for electrochemical studies, infrared reflectors, antistatic coatings, thin-film resistors, antireflection coatings, resistance-reducing top layers on various solar cells and for a variety of display devices and imaging tubes [1-5]. Tin-doped indium oxide (ITO) is the best and most extensively studied material of this type. The required quality of the film increases with increasing sophistication of application. Achievement of the lowest possible resistivity is of practical significance, as it provides some freedom over the choice of film thickness to achieve high optical transmission while still maintaining low sheet resistance. Efforts to improve the resistivity while maintaining high optical transparency have included: postdeposition heat treatment [6], doping at both cation and anion sites [7], and production of multilayered indium oxide-tin oxide films [8]. Two methods which could reduce the resistivity and have not yet been tried are: growth of single-crystal indium oxide films followed by epitaxial growth of a thin film of Sn203, so that the single-crystal epilayer of S n 2 0 3 provides free electrons which could then be mobile in the indium oxide layers; and doping of the top few layers of a single-crystal indium oxide film with tin. Both of these methods require very expensive equipment and impose limitations on the choice of the substrate. Hence, they are impractical for commercial production. In addition to the achievement of the lowest possible resistivities, the other main objectives of the present research were to achieve the highest possible electron mobility and to provide an answer to the long-debated [9-12] question of the dominant scattering mechanism in tin-doped indium oxide films. This letter reports a very simple method for preparing selectively doped thin films. The objective was to devise a simple cost-effective method to produce films containing "zones" of heavily doped material sandwiches between the "zones" or relatively high-purity material. The heavily doped "zones" would act as free electron generators and the high-purity "zones" would provide a path for the electrons. The result would be high electron mobility and charge carrier density, and hence lower electri-

Surface concentrations of indium, phosphorus and oxygen in indium phosphide single crystals after exposure to gamble solution

The surface of indium phosphide single crystals exposed to synthetic lung fluid (Gamble solution) has been investigated. An oxygen depth profile, obtained by employing the 3.034-MeV resonance in the elastic scattering of α particles from 16 O, detected oxygen at maximum concentrations of 24% in a layer 1000 A thick. O:In and O:P ratios were found to increase with prolonged exposure time as determined by angle-resolved XPS, although binding energies and peak fwhm's remained relatively constant

μ + Knight shift and spin relaxation in indium single crystalKnight shift and spin relaxation in indium single crystal

μ+ SR measurements have been performed in a single crystal indium sample between 12 K and 300 K with a stroboscopic μSR spectrometer. The muonic Knight shiftKμ and the muonic depolarization rate σ were obtained for various angles θ between the tetragonal crystallinec-axis and the direction of the external field. The isotropic part ofKμ is only weakly temperature dependent and is consistent with the estimated Pauli spin susceptibility value. At a temperature of 12 K the angular dependence ofM2 (the second moment of the field distribution at the muon, obtained from the measured σ(θ) values) allows a clear determination of the muon location — the symmetric tetrahedral site. The observed anisotropicKμ cannot be explained by the dipoles at the In atoms responsible for the bulk magnetic susceptibility but probably originates from an anisotropic Pauli spin susceptibility.

The elastic behaviour of indium under pressure and with temperature up to the melting point

Abstract The ultrasonic pulse-echo overlap technique has been used to measure pressure and temperature dependences of elastic wave propagation velocities along various crystallographic directions in single-crystal indium. The results provide a complete set of the pressure derivatives of the elastic constants of indium between room temperature and the melting point (429·7 K). This in turn has allowed the long-wavelength acoustic mode Gruneisen parameters to be determined over that temperature range. The values obtained for acoustic mode Gruneisen parameters show that there is a significant increase in vibrational anharmonicity as the melting temperature is approached. To allow determination of the thermal Gruneisen parameters γth up to the melting point, the thermal expansion tensor components α11 and α33 have also been measured. The mean zone-centre acoustic mode Gruneisen parameter γe1 is found to be larger than γth owing mainly to the contributions from the more anharmonic slow shear modes (k[110], e[11...

HREM study of atomic image of single crystal indium phosphide

This paper reports some experimental results of high resolution electron microscopy (HREM) studies on single crystal indium phosphide (InP) along the [0 0 1] zone axis. Using 400 kV electrons, with defocus value about 46.0 nm, the optimum conditions for structure imaging for both In and P atoms were found to be about 26.0 nm. Decreasing the specimen thickness to about 15.0 nm, only atomic images of P remain; increasing the specimen thickness to about 37.0 nm, only atomic images of In remain. These experimental results are in good agreement with computer simulation. It was also observed that for bent crystal deviating from the [0 0 1] axis, the bright spots, corresponding to In and P atomic columns in high resolution structure imaging, are elongated at a deviation angle equal to 0.18 degrees, the two bright spots are connected together along the direction of the [1 1 0] zone axis. This phenomenon is also confirmed by computer simulation. In the experiment, a pair of dislocation waves were observed with apparent Burgers vectors of\(\tfrac{1}{2}[0 1 0]\) and\(\tfrac{1}{2}[0 \bar 1 0]\) while the actual Burgers vectors may be\(\tfrac{1}{2}[0 11]\) and\(\tfrac{1}{2}[0 \bar 1\bar 1]\).

Mechanism of internal oxidation of Sb and in in silver

A new two step oxidation model is proposed that describes the mechanism of internal oxidation of the non-noble impurities antimony and indium in silver. We have found that internal oxidation at 550 K leads to the formation of isolated SbO2 or InO2 molecules, respectively. The commonly used model of Wagner treats the oxidation as a one step process, which means that in the case of antimony and indium two oxygen atoms must be trapped effectively in one step. Assuming a trapping radius of one lattice constant this model predicts an oxidation front that is much steeper than observed experimentally. The two step oxidation model assumes that first one oxygen atom is trapped at the non-oxidized impurity to form a relatively unstable complex. If within the lifetime of this complex a second oxygen atom is trapped, a stable and completely oxidized complex is formed in the silver matrix. The two step oxidation model predicts the shape of the oxidation front during internal oxidation at 550 K of antimony or indium in silver single crystals correctly, when a dissociation energy of 0.60(5) eV for the unstable complex is taken.

Reflection High-Energy Electron Diffraction Studies of Indium Phosphide Surface

Reflection high-energy electron diffraction studies of single-crystal indium phosphide substrates have been performed. It is shown that the substrates do not undergo any deleterious changes during chemical etching or the back contact sintering process. The low-power plasma exposure of the substrates is, however, responsible for structural modifications at the front surface and the performance of indium tin oxide/indium phosphide solar cells.

X-ray diffraction with a four-reflection monochromator

A formula is derived for simulating rocking-curve measurements made with an X-ray diffractometer fitted with a four-reflection monochromator. The derivation is carried out both graphically and algebraically. Results of a simulation using this formula are then compared with experimentally obtained rocking curves. The rocking curves were obtained using a diffractometer with a four-reflection monochromator that uses 440 reflections from two channel-cut germanium crystals. The experimental data comprise 200, 400, 600, 511, 711, 622, 422 and 444 reflections from thick single-crystal indium phosphide grown by the vertical-gradient freeze technique. The simulated data correlate well with the experimental data, although the simulations consistently show somewhat higher reflectivities and narrower linewidths than the experiment, indicating the existence of broadening mechanisms not included in the simulation that are affecting the experiment.

Anisotropy in the Hall coefficient of indium

The Hall coefficient of single-crystal indium was measured in two geometries: B//(100)(RH perpendicular to ) and B//(001)(RH//) at 4.2K. An anisotropy was observed in the Kohler plot: in intermediate and low fields, RH perpendicular to is more negative than RH//. Isothermal measurements of RH at 3.5K and 1.9K are also reported. The effects of the Fermi surface geometry and the wavenumber-dependent electronic relaxation time on the anisotropy are discussed.

Reaction of the (111) faces of single-crystal indium phosphide with alkylating agents. Evidence for selective reaction of the P-rich face

We wish to report that the P-rich, (111)B, face of single-crystal InP, but not the In-rich, (111)A, face of the same crystal, reacts with molecular reagents to yield surface-bound material derived from the apparent alkylation of a surface P atom. Exploitation of surface functional groups has been demonstrated to be very important in the attachment of molecular reagents and polymers to electrode surfaces. Electrodes derivatized with molecules have potential uses in analysis, fuel cells, electrosynthetic cells, and photoelectrochemical cells. We now wish to present evidence showing that an important photoelectrode material, InP, can be functionalized with molecules by reaction of the P-rich, (111)B, face with alkylating reagents.

Growth of indium phosphide from indium rich melts

Single crystal indium phosphide has been grown by the LEC process from melts containing up to 20 wt% excess indium. The electrical properties of the crystals were measured using the Van der Pauw method. Chemical impurity concentrations were determined by spark source mass spectrometry. Crystals grown from 20 wt% excess In melts were n-type with N D − N A =3×10 15 cm -3 and mobilities of 30,000 cm 2 V -1 s -1 at 77 K. These are significantly purer than equivalent undoped crystals grown from stoichiometric melts.

The growth and perfection of single crystal indium phosphide produced by the LEC technique

This paper describes recent studies at RSRE concerned with identifying residual impurities and structural defects in single crystal InP grown by the Czochralski liquid encapsulation technique (LEC) and discusses means whereby the impurities and defects can be controlled. The role of some deliberately added dopants (e.g., Fe, Co and Ge) in inducing specific properties is also described.

Ultrasonic attenuation in normal and superconducting indium

Abstract : The dependence of ultrasonic attenuation on temperature, sonic frequency, propagation direction, and superconducting state has been measured in indium single crystals using low-amplitude longitudinal waves. These measurements and the experimental apparatus with which they have been obtained are described. These data indicate that, in addition to the usual electronic attenuation described quantitatively by the BCS theory of superconductivity (Bardeen et al., Phys. Rev. 108, 1175), there is an additional source of attenuation. This secondary attenuation is generally attributed to the interaction of sound waves and crystal dislocations within the specimen, a process which has been described most thoroughly by Granato and Lucke (J. Appl. Phys. 27, 583). A comparison of the measured dislocation attenuations with those predicted by the theory of Granato and Lucke is given. This theory is shown to be inapplicable to the situation of this experiment, i.e., to indium at low temperatures. Earlier works in which similar data appear to substantiate the Granato and Lucke theory of dislocation attenuation are shown to be insufficient tests of that theory. (Author)

Measurement of the impurity diffusion of In in Ni single crystals by secondary-ion mass spectrometry (SIMS)

Abstract Secondary-ion mass spectrometry (SIMS) has been used to study the impurity diffusion ion of indium in nickel single crystals over the temperature range of 777 to 1513 K. The diffusion coefficients ranged from 4.1 × 10−17 to 2.4 × 10−9 cm2 s−1. Comparison of these values with radiotracer data in the literature shows very good agreement. The resulting values for the frequency factor and activation energy of the lattice impurity diffusion are: D o = 1.1 ± 0.4 cm2 s−1 and Q = 250 ±4 kJ mol−1. “Short-circuit” contributions to the diffusional flux were evident in three specimens annealed at the lowest temperatures. Evaporation of the solute during annealing was observed in some cases and is discussed in terms of Reimers's analysis. The applicability of SIMS to impurity diffusion studies is demonstrated.

Dislocation clusters in Czochralski-grown single crystal indium phosphide

Clusters of etch pits which sometimes form in single crystal indium phosphide grown by the Czochralski liquid-encapsulation technique, are shown to equate with prismatic dislocation loops generated by a stress source at the centre of the cluster. The morphology of the clusters and the conditions under which such clusters form are shown to be consistent with the presence of either a precipitate or an inclusion. It is demonstrated that water vapour associated with the boric oxide used as the liquid encapsulant is a positive cause of clusters and that vacuum baking is a pre-requisite for their control. The elements responsible for the stress generation promoting the clusters have not been positively identified but the likely possibilities are discussed.

Effect of strain content on the ultrasonic attenuation in the intermediate state of type I superconductors

The attenuation of longitudinal ultrasonic waves has been measured in single-crystal indium doped with 0.002 at. % of bismuth in various physical states of the specimen in the intermediate state over the frequency range 23 to 30 MHz. Two phases have been identified in the superconducting layers. The fundamental frequency v/sub 0/ for one phase is approximately constant for various physical states of the specimen for the same field, but increases with increase in magnetic field from .07H/sub c/ to 0.9H/sub c/; the fundamental frequency v/sub 0/ for the other phase decreases with decrease in dislocation density. The origin of the first phase is due to the laminar structure of the intermediate state. The second phase is due to the formation of microstructure in the superconducting layers due to the impurity and strain content in the specimen. The thickness of the microstructure has been calculated utilizing Granato and Lucke's vibrating string model of dislocation for various physical states of the specimen.

Impurities in single crystal indium phosphide

The impurity concentrations in present low carrier concentration indium phosphide single crystals (ND-NA=2×1015 to 5×1015cm−3) grown by the Czochralski technique have been measured by spark-source mass spectrometry and radio-gamma activation analysis and compared with both the polycrystalline source material and the excess indium produced during compounding and growth. The predominant impurities are shown to be carbon, oxygen and silicon but the segregation of lesser impurities into the excess indium has allowed some nineteen other elements which are likely to be present in indium phosphide to be identified. No consistent correlation is evident between the measured concentration of specific impurities and the ionized donor (ND) and acceptor (NA) impurity levels as determined from the free-electron concentration (ND-NA) and Hall mobility at 77 K using the Brooks-Herring theory.

Etch features in Czochralski-grown single crystal indium phosphide

Two etchants for InP have been used to categorize etch features in both horizontal and vertical sections of InP single crystals grown by the Czochralski liquid encapsulation technique; these are the AB etchant, used extensively for defect analysis in GaAs and another etchant based on a phosphoric acid/hydrobromic acid mixture. The behaviour of these etchants is different but a cross correlation has been made between the types of etch feature produced. Transmission X-ray topography has been used to correlate etch features with dislocations. Nominally undoped crystals and material doped with specific impurities, e.g. Fe, Ge, Zn, have been examined. The principal features produced by etching are pits, ridges and striations. It is shown that the density and distribution of pits and ridges is consistent with these features being dislocation structures and the mechanisms by which they are revealed are discussed in terms of etching rates. The results allow comment to be made upon interface shape and the source of dislocations in InP crystals grown by the Czochralski technique.

Ultrasonic velocity dispersion in single-crystal indium

Measurements of the ultrasonic velocity dispersion have been made in single-crystal indium over a range of temperatures and magnetic fields where the Hall coefficient changes sign. Results are well described by the free-electron Alpher-Rubin theory.