Heterogeneous nucleation and growth of thin films

Harsdorff, M.

doi:10.1016/0040-6090(82)90061-x

Cited by 49 publications

(23 citation statements)

References 22 publications

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“…7 There are other examples in the literature where nucleation on surface point defects takes place. 3,8,9 In recent examples plateaus in the island density with temperature were found with Fe and Cd growth on CaF 2 surfaces 8 and Fe growth on UHV-cleaved MgO͑001͒. 9 In the latter work a constant island density of 6ϫ10 12 cm Ϫ2 , very comparable to the value observed in the present study, was found between 200 and 500 K, which suggests the operation of a similar growth mechanism.…”

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confidence: 77%

Nucleation and growth of supported clusters at defect sites: Pd/MgO(001)

et al. 2000

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Nucleation and growth of Pd on cleaved MgO͑001͒ surfaces were studied by variable-temperature atomic force microscopy in the temperature range 200-800 K. Constant island densities (ϳ3ϫ10 12 cm Ϫ2 ) were observed over a wide temperature range, indicating nucleation kinetics governed by point defects with a high trapping energy. These results are compared to a rate equation model that describes the principal atomistic nucleation and growth processes, including nucleation at attractive point defects. Energies for defect trapping, adsorption, surface diffusion, and pair binding are deduced, and compared with recent ab initio calculations.Metal aggregates supported on oxide surfaces have many practical applications due to their catalytic, magnetic, and electrical properties. Consequently, fundamental studies have been carried out on a range of model systems.1 Although the main microscopic steps governing nucleation and growth of the films are now understood, detailed characterization of these processes has proven difficult. In particular, little is known about the energies involved. In recent years, ab initio calculations of the binding of metal atoms and clusters to oxide surfaces have progressed, generating further stimulus for experimental determination of the relevant interactions. On the other hand, a much more complete understanding has been achieved for the case of metallic substrates. In large part, this is due to the application of variable-temperature scanning tunneling microscopy ͑STM͒ for in situ imaging of the nucleation and growth stages, compared to analytic models and numerical simulations. In this work, we adopt a similar approach to metal growth on insulating oxide surfaces. This allows us to determine the principal energies governing nucleation and growth, and in particular to consider the influence of defects. On oxides, defects like vacancies or steps are present even at wellprepared single-crystal surfaces. Frequently the nucleation and growth behavior on these substrates is dominated by the defects. Early transmission electron microscopy studies of metal growth on alkali halide and alkaline earth surfaces 3 indicated defect nucleation in some cases, but relatively little is known about the interaction between defects and adsorbed metal atoms.We have studied the growth of Pd on MgO͑001͒ surfaces, utilizing variable-temperature atomic force microscopy ͑AFM͒ to image the deposits. This is one of the most explored metal/oxide systems, being a model for supported metal catalysts. Palladium grows in three-dimensional clusters, similar to most metal/oxide systems, as the surface energy is usually higher for metals than for oxides.1 We demonstrate that the nucleation kinetics in a large temperature range is determined by attractive point defects. With the help of a simple rate equation model we deduce the relevant interaction energies for the Pd/MgO͑001͒ system. It is expected that the understanding of nucleation at defects can be explored to produce novel nanostructures. The experiments were performed...

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confidence: 77%

Nucleation and growth of supported clusters at defect sites: Pd/MgO(001)

et al. 2000

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“…30 In usual deposition conditions AG is positive, and so n is an increasing function of R and a decreasing function of T. 36 If we believe that this is the case also for (001) YBCO films, we can explain the increasing void density at high temperature, and we can infer that a lower void density can be achieved by resorting to higher deposition rates. 30 In usual deposition conditions AG is positive, and so n is an increasing function of R and a decreasing function of T. 36 If we believe that this is the case also for (001) YBCO films, we can explain the increasing void density at high temperature, and we can infer that a lower void density can be achieved by resorting to higher deposition rates.…”

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confidence: 97%

Morphological and structural properties of high quality YBCO thin films

et al. 1995

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High-quality YBCO thin films have been grown by Inverted Cylindrical Magnetron Sputtering (ICMS) on LaAlO 3 (100), SrTiO 3 (100), SrTiO 3 (110), and MgO(lOO) substrates. Transition temperatures of oaxis films exceed 90 K, and transition widths are within 1 K. Critical currents range up to 5 X 10 6 A/cm 2 at 77 K. Structural and morphological features analyzed by x-ray diffraction and scanning electron microscopy, respectively, are found to be strongly dependent on film orientation and deposition temperature. In order to understand such dependence, a simple interpretation is proposed in terms of Gibbs energies and growth dynamics of the nucleation process.

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“…At a deposition temperature of T < 200 K, Pb on Ni(001) grows in the VolmerWeber (VW) [38,39] mode, as shown by monotonic parts of the AES(t) plots for 61 eV nickel and 94 eV lead peaks (Fig. 1a).…”

Section: Resultsmentioning

confidence: 99%