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  • 2020-2022  (1)
  • 1985-1989  (34)
  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the electrical resistivity of Ti, Mo, Ta, and W monocrystalline disilicides (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1584-1590 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical resistivity of monocrystalline TiSi2, TaSi2, MoSi2, and WSi2 has been measured from 4.2 to 1100 K. These disilicides are metallic, yet there is a remarkable difference in the temperature dependence of their intrinsic resistivities. TiSi2 and TaSi2 are found to exhibit a T5 dependence in the temperature range of 13〈T〈30 K and 15〈T〈28 K, respectively, while MoSi2 and WSi2 show a T3.8 dependence from 15 to 40 K. For TiSi2, along the three crystallographic directions 〈100〉, 〈010〉, and 〈001〉, the phonon contribution to the resistivity was found to be linear in temperature above 300 K. The same behavior was observed for TaSi2 along the 〈0001〉 axis, while a negative deviation from the linearity followed by a quasisaturation was observed with the current, parallel to the 〈101¯0〉 axis. The resistivity data of WSi2 and MoSi2 with the current parallel to 〈001〉 and 〈110〉 crystallographic directions showed a positive deviation from linearity. The data are fitted to several theoretical expressions at low temperatures and in the full range of temperatures. The results are discussed in light of these theories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342949
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology and kinetics of crystallization of amorphous V75Si25 thin-alloy films (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2445-2452 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical and microstructural changes of coevaporated V75Si25 alloy thin films have been studied as a function of temperature from room temperature to 830 °C. In situ resistivity measurements, hot-stage transmission electron microscopy, Rutherford backscattering spectroscopy and the Seeman–Bohlin glancing angle incidence x-ray diffraction technique were applied. Upon heat treatment at a heating rate of 8 °C/min, a sharp decrease in resistivity occurs at ∼670 °C which results from an amorphous to crystalline phase transformation. The crystallized phase was identified as V3Si. The mechanism of transformation is random nucleation at a rapidly decreasing rate and a fast quasi-isotropic growth. The kinetics of crystallization have been studied by utilizing electrical resistivity measurements during isothermal heat treatment. Six different temperatures between 570 °C and 630 °C were adopted. The apparent activation energy (∼3.6 eV) obtained from isothermal measurements was found to be in agreement with that obtained from nonisothermal treatments at varying rates of heating. The distinct change of the Avrami mode parameter from 4 to 2 at a constant value of t/τ during the process of crystallization is not immediately understood.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337157
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  • 3
    Electronic Resource
    Electronic Resource
    Electrical transport properties in Co-silicides formed by thin-film reactions (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 310-317 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Four different Co-silicide compounds were obtained by solid-state reaction at 800 °C in thin bilayers of amorphous silicon and cobalt evaporated on SiO2 substrates. Rutherford backscattering spectroscopy (2 MeV 4He+), x-ray diffraction, and Auger electron spectroscopy were used to obtain information about the chemical and crystallographic characteristics of the samples. Results indicate that in each sample only one of the following phases is present: CoSi2, CoSi, Co2Si, and Co4Si, the latter identified on the basis of the stoichiometric ratio only. Electrical resistivity and Hall effect measurements on van der Pauw structures were carried out as a function of the temperature in the intervals: 10–1000 and 10–300 K, respectively. At room temperature the resistivity ranges from the value 19 μΩ cm for CoSi2 to the value 142 μΩ cm for CoSi. There are some analogies with the case of a classical metal, but remarkable differences are also detectable in the resistivity versus temperature behavior and in the order of magnitude of the resistivity and of the Hall coefficient. In particular, at T〉300 K the resistivity of the CoSi2 samples linearly depends on temperature and is well fitted by the classical Bloch–Grüneisen expression. The other silicides show, in the same temperature range, a deviation from linearity (d2ρ/dT2〈0), while a quasi saturation of the resistivity can be extrapolated at higher temperatures. This saturation phenomenon can be described by the parallel of an ideal conductivity and of a saturation conductivity, and associated with the electron mean free path approaching interatomic distances. A similar model already has been put forth to describe the saturation of the resistivity in systems, such as A-15 superconducting compounds, characterized by a high value of the room-temperature resistivity. The transport parameters, deduced in a free electron framework from the resistivity curves of the Co silicides, show values which are consistent with the proposed model. Hall coefficient versus temperature behavior indicates that between 10 and 300 K a multicarrier effect is present. Conduction is predominantly n type in CoSi and p type in the other silicides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337645
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  • 4
    Electronic Resource
    Electronic Resource
    Temperature dependence of semiconducting and structural properties of Cr-Si thin films (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 2018-2025 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical and structural properties of coevaporated Cr-Si thin alloy films and bilayer Cr/Si films as a function of annealing temperature from 10 to 1000 °K have been studied by in situ electrical resistivity and Hall measurements, and structural analysis including MeV 4He+ ion backscattering, x-ray diffraction, Auger electron spectroscopy combined with Ar sputtering, electron microprobe, and scanning and transmission electron microscopy. In the as-deposited state, the coevaporated alloy film was amorphous. Upon annealing, a sharp increase in resistivity occurred near 270 °C and the increase has been determined to be amorphous to crystalline CrSi2 phase transformation. The resistivity increased further with annealing up to 550 °C then a gradual decrease took place beyond 600 °C. In cooling, the resistivity increased monotonically with decreasing temperature. For the bilayer Cr/Si films, the annealing behavior is similar except the sharp increase in resistivity occurred around 450 °C due to the formation of CrSi2. The crystalline CrSi2 has been determined to be a semiconductor with an energy gap of 0.27 eV. It is p-type, having a hole concentration of 4×1019 cm−3 at room temperature and a hole mobility of 7.2×104×T (temp)−3/2 cm2/V sec in the acoustic scattering region. The kinetics of amorphous-to-crystalline transformation of Cr-Si alloy film in the temperature range of 225–25 °C has been determined to follow a t7 (time) dependence with an apparent activation energy of 1.13 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334389
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  • 5
    Electronic Resource
    Electronic Resource
    Electrical transport properties of transition-metal disilicide films (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1085-1093 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical resistivity in the temperature range of 2–1100 K and Hall-effect measurements from 10 to 300 K of CoSi2, MoSi2, TaSi2, TiSi2, and WSi2 polycrystalline thin films were studied. Structure, composition, and impurities in these films were investigated by a combination of techniques of Rutherford backscattering spectroscopy, x-ray diffraction, transmission electron microscopy, and Auger electron spectroscopy. These silicides are metallic, yet there is a remarkable difference in their residual resistivity values and in their temperature dependence of the intrinsic resistivities. For CoSi2, MoSi2, and TiSi2, the phonon contribution to the resistivity was found to be linear in temperature above 300 K. At high temperatures, while a negative deviation from the linearity followed by a quasisaturation was observed for TaSi2, the resistivity data of WSi2 showed a positive deviation from linearity. It is unique that the residual resistivity, ρ(2 K), of the WSi2 films is quite high, yet the temperature dependent part, i.e., ρ(293 K) − ρ(2 K), is the smallest among the five silicides investigated. This suggests that the room-temperature resistivity of WSi2 can be greatly reduced by improving the quality of the film, and we have achieved this by using rapid thermal annealing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338203
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal stability and electrical conduction behavior of coevaporated WSi2±x thin films (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 354-364 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of coevaporated amorphous WSi2±x(x(approximately-equal-to)±0.2) thin films from room temperature to 1000 °C has been studied by in situ resistivity measurements and hot-stage transmission-electron microscopy. During continuous heating two consecutive phase transformations were observed to occur via nucleation and growth processes. The first which occurs at ∼420 °C is the crystallization of the amorphous film to a metastable, semiconducting hexagonal phase WSi2. The second which occurs at ∼620 °C is the transformation of the hexagonal phase to the thermodynamically stable, metallic, tetragonal phase of WSi2. The hexagonal phase is characterized by an acicular morphology and its formation is associated with a drastic increase in resistivity. The crystallites (grains) of the stable tetragonal phase are equiaxed and their formation is associated with a rapid decrease in resistivity. In order to achieve a low value of resistivity, ∼70 μΩ cm at room temperature, the tetragonal phase must be annealed to the neighborhood of 1000 °C. The activation energy for the hexagonal to tetragonal transformation (∼3 eV) was found to be higher than that for the crystallization (∼2 eV). The mode parameters for both transformations were found to be almost the same, n∼2. The characteristics of both transformations were not greatly influenced by the compositional changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341435
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  • 7
    Electronic Resource
    Electronic Resource
    Phase transformations in alloy and bilayer thin films of vanadium and silicon (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2429-2438 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Phase transformations in coevaporated amorphous vanadium-silicon thin alloy films and bilayer vandium/silicon films have been studied as a function of heat treatment by in situ electrical resistivity measurement together with Rutherford backscattering spectrometry, Seeman–Bohlin glancing angle incidence x-ray diffraction, and scanning and transmission electron microscopy. In the as-deposited state the amorphous alloy films were silicon rich, having an atomic ratio of 1:3 for vanadium and silicon, respectively. Upon heat treatment a sharp decrease in resistivity occurs at approximately 250 °C, which has been determined to be a transformation from the amorphous to crystalline VSi2 phase. The kinetics of the transformation have been obtained by isothermal treatment over the temperature range of 184–220 °C. The transformation is described by a Johnson–Mehl–Avrami-type equation with an apparent activation energy of 1.30±0.06 eV. Subsequent heat treatment causes a gradual decrease in resistivity up to 850 °C. Upon cooling, a monotonic decrease in resistivity was observed. Heat treatment at high temperatures (900 °C) promotes the growth of nonuniformly distributed silicon grains. For the bilayer vanadium/silicon films, the sheet resistance increases gradually upon heat treatment up to 500 °C, then a sharp decrease is observed, which is due to the formation of VSi2. Further heat treatment at higher temperatures (850 °C) promotes a monotonical decrease in the resistance. The cooling behavior is similar to that of the crystallized alloy specimens except for having a slightly lower resistivity value. In a model for the two thin films connected electrically in parallel, the growth kinetics of VSi2 in the bilayer films has been found to be linear in time over the temperature range of 500–535 °C with an activation energy of 2.23±0.09 eV. The microstructure of films at various stages of annealing have been studied by x-ray diffraction and transmission electron microscopy. Correlation between the resistivity and microstructure is given and discussed. In situ resistivity of annealed films below room temperature has been measured. Crystalline VSi2 thin films do not become superconductive down to 2 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336345
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  • 8
    Electronic Resource
    Electronic Resource
    Metal silicides with energetic pulses (1986)
    Springer
    Applied physics 40 (1986), S. 183-190 
    Details
    ISSN: 1432-0630
    Keywords: 68.55 ; 79.20H ; 79.20D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Samples formed of a thin metal film deposited on silicon single crystal were annealed with electron and laser (ruby and excimer) pulses over a wide range of fluences. From a comparison of the experimental results with the temperature profiles of the irradiated samples, it turns out that suicide formation starts when the metal/silicon interface reaches the lowest eutectic temperature of the binary metal/silicon system. The growth rate of reacted layers is of the order of 1 m/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617402
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  • 9
    Electronic Resource
    Electronic Resource
    Automatic seismic wave detection and autoregressive model method (1988)
    Springer
    Mathematical geology 20 (1988), S. 37-48 
    Details
    ISSN: 1573-8868
    Keywords: Automatic detection ; seismic networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The problem of automatic detection of seismic waves by large telemetered seismic networks such as the Mexican Continental Aperture Seismic Network (RESMAC), is extended here to include determination of seismic first-arrival and S-phase-arrival times. A short general outline of the detection problem background and a small introduction to the autoregressive model (AR) concept are presented. Several automatic detection algorithms were implemented and compared with a newly developed autoregressive algorithm. Careful consideration of the advantages and disadvantages of each method determined that a mixed detection scheme is optimal and suitable for RESMAC. A few examples are shown that illustrate the relative performances of the methods tried here. The proposed detection scheme has the following characteristics: (a) First-arrival detection, based on a simple (average of squared input) characteristic function, and a trigger criterion that uses as a distortion measure the long-average-to-short-average ratio of the characteristic function, checked using a duration criterion; (b) use of two threshold values, one for triggering, and another for beginning the backward search for the phase arrival time; (c) use of the autoregressive model (AR) method, with the Itakura-Saito distortion measure, for S-phase detection, checked using both duration and amplitude criteria; and (d) characterization of the reliability of the determinations for their subsequent use in automatic location programs, alarms, etc. The automatic detection scheme has proved effective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00903187
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  • 10
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    Oxygen in-diffusion processes in tetragonalYBa2Cu3O7−xoxide (1989)
    American Physical Society
    Details
    Publication Date: 1989-05-01
    Print ISSN: 0163-1829
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society
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