Lattice distortion energy spectra of as-grown bismuth thin films and their thickness dependence
TL;DR: In this paper, the initial lattice distortion energy spectra of as-grown bismuth thin films have been evaluated and it is found that the defects have preferential activation energy values around 1.06 eV, 1.14 eV and 1.32 ev.
Abstract: Bismuth thin films of various thicknesses between 15 nm and 350 nm were vacuum deposited at room temperature on to glass substrates, immediately after which they were twice heat treated at a uniform rate. During the heat treatment, the resistance changes were monitored and, using these data, the initial lattice distortion energy spectra of as-grown bismuth thin films have been evaluated. It is found that the defects have preferential activation energy values around 1.06 eV, 1.14 eV and 1.32 ev. It is also found that ∫F0 (E) dE oscillates with thickness, which is attributed to the quantum size effect.
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TL;DR: In this article, Bismuth thin films in the thickness range from 10 to 200 nm were deposited on glass substrates by thermal evaporation and investigated by electron microscopy and X-ray diffraction.
Abstract: Bismuth thin films in the thickness range from 10 to 200 nm were deposited on glass substrates by thermal evaporation. The films were investigated by electron microscopy and X-ray diffraction. No anomalous dependence of the structural features on the film thickness was observed but only a normal monotonic variation. All the samples were polycrystalline with a high degree of preferred orientation. The [0001] H or [111] R fibre texture was against heat treatment. The residual strain decreased abruptly with increasing thickness up to 30 nm while the grain size increased up to a thickness of 100 nm and then exhibits almost no further change. The substructure within the individual grain, such as twining and/or stacking faults, was considered on the basis of the large values of grain size revealed by direct observation with transmission electron microscopy compared with those obtained from X-ray diffraction line profile analysis. A structure-properties (electrical) intercorrelation was proved.
23 citations
TL;DR: In this paper, the thermoelectric power and electrical conductivity data were combined and simultaneously analyzed using the effective mean free path theory of size effect in thin antimony films developed by Tellier and Pichard et al.
Abstract: Thin antimony films of thicknesses in the range 30 to 200 nm have been vacuum deposited on glass substrates at room temperature. After annealing for about an hour at 500 K, the thermoelectric power and electrical resistivity were measured in vacuum as a function of temperature. The thermoelectric power and electrical conductivity data were combined and simultaneously analysed using the effective mean free path theory of size effect in thin films developed by Tellier and Pichard et al. In addition, their temperature dependence was also analysed. It was found that the thermoelectric power is positive and increases with increasing temperature and is inversely proportional to the thickness of the film. The electrical resistivity was found to be temperature dependent with the temperature coefficient of resistivity being positive, and inversely proportional to the thickness of the film. Analysis combining the data from the thermoelectric power and electrical conductivity measurements has led to the determination of mean free path, carrier concentration, effective mass, Fermi energy and the parameter \(U_g = (d ln l_g /d ln E)_{E = E_F } \) The data were analysed for least squares fitting by local functions, such as the spline functions, which eliminates possible errors in conventional least squares fitting of data using non-local functions valid throughout the range.
13 citations
10 Jul 2005
TL;DR: The properties of bismuth have been studied, motivated by potential spacecraft contamination effects of Bismuth Hall thrusters as mentioned in this paper, and an extensive literature survey was conducted to obtain electrical, thermal, sputtering, and optical characteristics, as well as morphology and quantum size effects of thin films.
Abstract: The properties of bismuth have been studied, motivated by potential spacecraft contamination effects of bismuth Hall thrusters. An extensive literature survey was conducted to obtain electrical, thermal, sputtering, and optical characteristics, as well as morphology and quantum size effects of thin films. Implications for contaminati on effects are discussed. The temperature -dependent balance between deposition, evaporation, and sputtering was also investigated. Deposition dominates over evaporation at essentially all locations around the thruster for typical spacecraft conditions. The sputter rate of emitted thruster ions on deposited films will compete effectively with the deposition rate in areas where energetic ions impinge. Accumulation of bulk deposition will occur in the backflow region unless control measures can mitigate the pr oblem.
4 citations
TL;DR: In this article, thin bismuth films were vacuum-deposited onto glass substrates at different substrate temperatures in a vacuum of 2×10−5 torr, and the resistance of the films has been measured as a function of temperature in situ during and after annealing.
Abstract: Thin bismuth films (thickness 25 nm) have been vacuum-deposited onto glass substrates at different substrate temperatures in a vacuum of 2×10−5 torr. The resistance of the films has been measured as a function of temperaturein situ during and after annealing. It is found that the resistance of all the annealed films decreases with increasing temperature thus showing a semiconducting type of behaviour. The films do not show a resistivity minimum observed in thicker films [1]. The absence of a resistivity minimum is attributed to the thinness of the films and consequent larger energy band gap and smaller grain size.
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TL;DR: In this article, the effects produced by the initial distribution, the order of reaction, and the frequency factor are discussed, as well as the complications which can result from successive reactions and varying frequency factors.
Abstract: The kinetic behavior of systems in which processes occur which are distributed over a range of activation energies is considered. The effects produced by the initial distribution, the order of reaction, and the frequency factor are discussed. Imaginary and actual experimental situations are used to illustrate the large errors which can result when the distribution of the processes in activation energy is neglected. Some of the complications which can result from successive reactions and varying frequency factors are mentioned.
304 citations
01 May 1943
TL;DR: In this article, the decay of lattice distortions is investigated and a characteristic function F0 expressing the law of distribution of the decay energies is formulated, calculated from measurements available and found to be of the expected order, and the shape of this function and the position of its maxima depend on the structure of the support and the thickness of the film.
Abstract: Metallic films prepared by evaporation show characteristic irreversible changes, especially if prepared at low temperatures. The changes can be explained by a decay of lattice distortions. To allow of a mathematical treatment, a set of simplifying assumptions is formulated. To initiate a decomposition of a distortion, a certain energy must be reached, but the observed changes cannot be explained if all distortions have the same decay energy. A characteristic function F0 expressing the law of distribution of the decay energies is formulated, calculated from measurements available and found to be of the expected order. The shape of this function and the position of its maxima depend on the structure of the support and on the thickness of the film. The resistance measurement at a constant temperature has the disadvantage that it reveals only a small part of F0. This is overcome if uniformly rising temperature is used. A possibility that the changes are caused by a recombination of interstitial atoms and lattice vacancies is investigated, but as this requires essentially only a single value of the transition energy, the results are inconsistent with the observed changes, so that the decay theory should be preferred, as it gives more consistent results.
243 citations
TL;DR: In this article, the initial lattice distortion energy spectra of the films have been determined from the resistance-temperature data, and it is found that the resistivity values for films of different thicknesses are in good agreement with the size effect theory.
Abstract: Tin antimonide alloy films, vacuum-deposited at room temperature onto glass substrates, were heated to a maximum temperature of about 300 °C and the changes in their electrical resistance with temperature were recorded. The initial lattice distortion energy spectra of the films have been determined from the resistance-temperature data. It is found that the F0(E)max and Emax values vary from 200×10-4 to 700×10-4ohms;cm/eV and from 1.55 to 1.74 eV respectively and that they depend upon the thickness of the film. The resistivities of the films due to thermal vibrations alone have been calculated and it is found that the calculated resistivity values for films of different thicknesses are in good agreement with the size effect theory.
23 citations
TL;DR: In this article, the authors measured the defect density and activation energy of an annealed polycrystalline polysilicon film of thickness 270-1670 A. The defect density F 0 (E ) max varies considerably from 21.4 to 5.25 μΩ cm eV -1 in the thickness range of 270 -1670
Abstract: Silver films of thickness 270–1670 A were deposited onto galss substrates by vacuum evaporation. The films were subjected to heat treatment at a constant rate and the variation of the electrical resistance with temperature was measured. From a knowledge of the time and the change in electrical resistance with temperature the defect density and activation energy were calculated for various thicknesses. The defect density F 0 ( E ) max varies considerably from 21.4 to 5.25 μΩ cm eV -1 in the thickness range 270–1670 A, whereas no appraciable variation in the activation energy is observed. The dependence of the resistivity and temperature coefficient of resistivity (TCR) on thickness were studied in the above thickness range and the bulk resistivity and TCR were found to be 1.675 μΩ cm and 4.075 × 10 -3 K -1 respectively. As the structure of the annealed film was found to be polycrystalline, the mean free path of the conduction electrons was estimated assuming the scattering coefficient to be zero.
22 citations