Epitaxial Growth Of Metals Research Articles

A strain-relieve transition in epitaxial growth of metals on Si(111)(7 × 7)

Pronounced RHEED specular beam intensity oscillations have been observed during the growth of several metals on a Si(111)(7×7) substrate at low temperature (100 K), showing that the metals grow in a layer-by-layer fashion. For all metals studied three regimes can be distinguished. Up to one or two monolayers the variation of the reflected intensity is due to changes in the surface structure rather than surface morphology. Next, a limited number ofoscillations with an ill-defined period appears. Most surprisingly, however, in most cases a sudden revival of the oscillations with a much more regular period is observed. It is suggested that this phenomenon is caused by a transition from a lattice-matched to a relaxed layer-by-layer growth mechanism.

In situ RBS and channeling study of molecular beam epitaxial growth of metals and semiconductors on semiconductors

High energy ion scattering (HEIS) has been used for in situ surface and interface studies of molecular beam epitaxial growth of metals and semiconductors on semiconductors. In the study of phase transitions during the initial growth and thermal desorption of Pb on Si(111), HEIS measurement has directly and accurately determined the metal overlayer coverage associated with various surface structures and clearly revealed SiPb interface relaxation and Pb island formation. These results contribute to an unambiguous interpretation of LEED patterns and STM images. HEIS has been used to monitor the homoepitaxial growth of Ge on Ge(111) through liquid metal media, and to characterize in situ the grown thin films. This leads to a better understanding of the growth mechanism and optimal growth conditions.

7399. Epitaxial growth of metals studied with thermal energy atom scattering: S Ferrer and J J de Miguel, Vacuum, 41, 1990, 464–466

7399. Epitaxial growth of metals studied with thermal energy atom scattering: S Ferrer and J J de Miguel, Vacuum, 41, 1990, 464–466

Epitaxial growth of metals: from monolayer to superlattice

The aim of this work is to show that, in order to produce high-quality metallic superlattices, the major requirements are to have an accurate control of the growth process and to use very flat, well ordered substrates. To this end, the growth of Co and Cu on Cu(100) has been studied from its very early stages, by means of Thermal Energy Atom Scattering (TEAS). Also, different Co Cu superlattices have been produced, and studied by neutron diffraction and SQUID magnetometry. They show good crystallinity, with the cobalt layers magnetized in plane and ordered antiferromagnetically. The magnetic moment of the cobalt atoms coincides with that of bulk fcc cobalt.

Epitaxial growth of metals studied with thermal energy atom scattering

The intensities of diffracted beams from a surface show, in some cases, pronounced temporal oscillations when an epitaxial film is growing from the vapour. This is easily understandable within the frame of the kinematical diffraction theory as being due to scattering from different surface levels. Analysis of the diffracted intensities allows quantitative values of the step densities of the growing film to be obtained. This is illustrated by the diffraction of neutral atoms (TEAS) from the surface of a Cu(100) crystal growing from the vapour phase. Also, it is shown that analysis of the diffracted intensity allows differentiation among the island nucleation vs step propagation growth regimes. The growth of cobalt on Cu(100) has also been studied with TEAS. It has been found that it grows pseudomorphically with an interplanar spacing of 1.74 ± 0.04 A°. The intensity vs deposition time curves show a peculiar shape that has been understood as being caused by the existence of two different step heights at the surface at low coverages: the substrate steps (1.80 A) and the cobalt steps (1.74 A).

The role of adsorbed gases in metal on metal epitaxy

It is found that a variety of (deliberately) adsorbed gases influence in some manner the epitaxial growth of metals on metals. The adsorbed gases investigated included molecularly adsorbed CO and H2O and dissociatively adsorbed H, O, N, C, and S. The effects of adsorbed gases have been investigated in metal-on-metal epitaxial systems including Cu/Cu(100), Ni/Ni(100), Cu/Ni(100), Ni/Cu(100), Fe/Cu(100), Cu/Fe(100), Fe/Ag(100), and Fe/Fe(100). Although not all of the possible gas–metal combinations among these systems have been studied, enough have been to make the following generalizations. Around room temperature and above, these gases exhibit a strong tendency to ‘‘float out’’ to the growing surface, hardly reducing the extent of epitaxial ordering. All but the most strongly bound, e.g., C or N, have a strong tendency to float out even during epitaxy at temperatures as low as 100 K. The most strongly bound, e.g., C, N, or O, tend to suppress the agglomeration or interdiffusion (which otherwise occurs) when a monolayer of a transition metal is deposited on a noble metal at room temperature or above, e.g., Fe/Cu(100) or Ni/Cu(100). In some cases, these effects may be useful as a new tool for gaining improved control over epitaxial growth.

Epitaxial growth of metals: Experimental results and Monte Carlo simulation

Abstract Layer-by-layer growth of epitaxial systems has been studied with Monte Carlo (MC) simulations, and the results have been compared with those of thermal energy atom scattering (TEAS). This technique has proved to be purely kinematical and sensitive only to defects in the outermost layers, thus allowing for a direct comparison with MC results.

Epitaxial growth of metals: Experimental results and Monte Carlo simulation

Layer-by-layer growth of epitaxial systems has been studied with Monte Carlo (MC) simulations, and the results have been compared with those of thermal energy atom scattering (TEAS). This technique has proved to be purely kinematical and sensitive only to defects in the outermost layers, thus allowing for a direct comparison with MC results.

Epitaxy of metals on metal substrates: The contribution of field electron emission microscopy

The contribution to the literature on the epitaxial growth of metals on metal substrates made by research using field electron emission microscopy are reviewed. In addition to a large amount of information about specific metal/metal pairs, some generalities have emerged. It is especially striking that in many cases of metal/metal epitaxy, the dominant factor determining the epitaxial relationship is the alignment of close-packed atomic rows in low-index crystallographic planes of each metal.

Intensity oscillations for electron beams reflected during epitaxial growth of metals

Beam intensities in reflection high-energy electron diffraction (RHEED) are observed to oscillate during the epitaxial growth at 300 K of body-centered-cubic nickel on the (100) surface of iron and of face-centered-cubic Ni on the (100) surface of Ni. Such oscillations have been studied thoroughly by others for the growth of GaAs by molecular-beam epitaxy, where there is little doubt about the mechanisms of layer-by-layer growth. Because the RHEED oscillations are observed on vicinal surfaces [e.g., the (100) planes of the iron substrate are misoriented with respect to the surface by \ensuremath{\sim}30 mrad], the implication is that diffusion of Ni is sufficiently slow that growth does not take place by growing from the step edges, yet fast enough for completion of one monolayer before substantial development of the next. The demonstrated utility of RHEED oscillations for monitoring controlling growth in GaAs is now applicable to metal growth.

A theoretical study of the epitaxial growth of metal overlayers on semiconductor surfaces

We report on the energetics for the epitaxial growth of metals on semiconductors and obtain optimal interplanar distances using the self-consistent pseudopotential method. A prototype system for which the lattice mismatch is not too severe has been considered so that the lattice can strain elastically to achieve coherency. An example of such a system is Al(001)–Ge(001) in an epitaxial relation (001)[100]Al∥(001)[110]Ge where the [100]Al axis has been rotated 45° with respect to the Ge [100] axis. We have investigated the pseudomorphic growth of Al from submonolayer to multilayers (in various registry patterns) on the rigid unreconstructed Ge(001) substrate. One significant result of our calculation is that the A1–Ge bond length relaxes as one goes from submonolayer to multilayer coverages of metal indicating a transition from directional covalent to more metallic type of bonding. Another important conclusion is that at monolayer coverages, aluminum at bridging positions in the first layer is more stable (∼1 eV) than at on top positions. This suggests that Frank–van der Merwe growth sequence is likely to initiate at the bridging sites. Furthermore, the energy lost due to an overall strain in pseudomorphically growing many layers is estimated to be well below the energy benefit due to interfacial bonding in bridging sites. We also report that the calculated interfacial bonding energy and the interplanar separation reaches limiting values at about one monolayer coverage, but other properties show slow convergence. The implications of these results for the electronic structure of interfaces and Fermi-level pinning are briefly investigated.

Epitaxial growth of metal single-crystal films

A review of the epitaxial growth of metals in high and ultra-high vacuum leading to single-crystal films is presented. The conditions for obtaining such films are described and tabulated for two groups of substrates: (i) metals, Si, Ge (strong interfacial bonding) and (ii) alkali halides and MgO cleavage faces (weak interfacial bonding). Information on the crystal defects and their relation with the growth parameters and annealing procedures is also given.

1451. Epitaxial growth of metals on rocksalt faces cleaved in vacuum Part II: S Ino,J Phys Soc Japan,21,Feb 1966, 346–362

1451. Epitaxial growth of metals on rocksalt faces cleaved in vacuum Part II: S Ino,J Phys Soc Japan,21,Feb 1966, 346–362

Epitaxial Growth of Metals on Rocksalt Faces Cleaved in Vacuum. II. Orientation and Structure of Gold Particles Formed in Ultrahigh Vacuum

The orientation and structure of gold particles formed by evaporation on rocksalt cleaved in ultrahigh vacuum have been studied at various stages of the nucleation and growth process. Besides four 200 and twenty-four 220 spots which indicate the presence of the (001) orientation and (111) orientation respectively, twenty-four abnormal 111 spots have been observed in electron diffraction patterns taken at earlier stages of growth, and various unusual contrasts have been observed in dark field electron micrographs using one of 111 spots. A multiply twinned particle model is proposed by the present author, and the appearance of the 111 spots and the dark field image contrasts can satisfactorily be explained by this model. With increasing thickness particles with the (111) orientation and without the multiple twinning exclusively grow up, while multiply twinned particles and those with the (001) orientation seem to stop their growth; and a continuous gold film with the (111) fibrous structure is formed at a t...

Epitaxial Growth of Metals on Rocksalt Faces Cleaved in Vacuum. I

The epitaxial growth of Ni, Cu, Ag, Au and Al on NaCl crystals cleaved in vacuum has been studied. When the crystals are cleaved in ordinary high vacuum (10 -4 –10 -5 mmHg), a considerable lowering of the epitaxial temperatures for the parallel epitaxy takes place for the first four metals, as compared with the case in which the crystals are cleaved in air. The temperature differences due to this lowering are 270°C for Ni, 250°C for Cu, 150°C for Ag, and 120°C for Au. Al has been found for the first time to form single crystal films with the (111)-plane parallel to the substrate at the substrate temperature of 100°C. When the degree of vacuum is improved to ultrahigh vacuum (10 -7 –10 -9 mmHg), on the other hand, the (001) preferred orientation deteriorates and the (111) preferred orientation appears for Cu, Ag and Au, the latter orientation becoming conspicuous with rising temperature for Au and Ag, while no considerable change arises for Ni and Al with the improvement of the degree of vacuum.

5. Epitaxial growth of metals on rock-salt faces cloven in vacuum: S. Ino, D. Watanabe and S. Ogawa, J. Phys. Soc. Japan, 17 (6), June 1962, 1074–1075

5. Epitaxial growth of metals on rock-salt faces cloven in vacuum: S. Ino, D. Watanabe and S. Ogawa, J. Phys. Soc. Japan, 17 (6), June 1962, 1074–1075

Epitaxial growth of metals on rock-salt faces cloven in vacuum

Epitaxial growth of metals on rock-salt faces cloven in vacuum