It is proposed that inhomogeneities in the deposition rate can be a powerful tool for investigating properties of growing films. The macroscopic shape of the resulting surface deformation is discussed analytically for the growth equation proposed by Kardar, Parisi, and Zhang [Phys. Rev. Lett. 56, 889 (1986)]. Computer simulations for a single-step growth model confirm the predictions based on this equation and give explicit values for its parameters. It is argued that inhomogeneous deposition also provides a new method for measuring the roughness exponent.

Indications for a crossover between two distinct dynamical regimes at a temperature ${\mathit{T}}_{\mathit{c}}$ above the glass-transition temperature ${\mathit{T}}_{\mathit{g}}$ are presented for simple supercooled liquids. (i) Relating diffusion coefficient D and reorientational correlation times τ with viscosity η, a discontinuity for the temperature coefficient of τ/η or 1/Dη is observed, demonstrating the failure of the Stokes-Einstein relations for T<${\mathit{T}}_{\mathit{c}}$. (ii) Plotting NMR and dielectric correlation times on a reduced scale ${\mathit{T}}_{\mathit{g}}$/T shows that a bifurcation of the two relevant processes in a supercooled liquid (α and β processes) appears for T<${\mathit{T}}_{\mathit{c}}$. ${\mathit{T}}_{\mathit{c}}$ is found at T/${\mathit{T}}_{\mathit{g}}$=1.18–1.28.

Using a model based on the theory for hierarchically constrained relaxation of Palmer et al., it has been possible to account for the quadrupolar freezing of the CN ion in KBr-KCN alloys observed in both Brillouin scattering and low-frequency shear resonance. In particular, the small change in the glass-transition temperature with probe frequency can be accounted for.

A structure refinement of the decagonal quasicrystal ${\mathrm{Al}}_{70}$${\mathrm{Co}}_{20}$${\mathrm{Ni}}_{10}$ with the five-dimensional superspace group P10/mmm was made on the basis of single-crystal x-ray-diffraction data. The structure is a layer structure that consists of two kinds of layers stacked along the c (tenfold) axis with an interval of c/2 (c=4.08 Å). The structure has a local-atom arrangement similar to that of monoclinic ${\mathrm{Al}}_{13}$${\mathrm{Fe}}_4$, but includes stacking disorder of the layers. The model explains well the diffraction intensity, chemical composition, and density. There exists another model with P${10}_5$mc, which gives a diffraction intensity similar to that of the above model, except for the extinct reflections due to the extinction rule of the superspace group.

A dislocation emerging on a Cu(111) surface was studied by scanning tunneling microscopy. The Burgers vector and the resulting lateral and vertical shifts in atomic positions were determined. The dislocation was found to consist of two partial dislocations separated by 25 Å.

The transition between the √3 × √3 and 6×6 reconstructions of the Au/Si(111) surface is unusual in that, as the Au coverage increases, there is a continuous evolution of the surface structure with Au coverage, rather than a simple change in the relative abundances of two distinct, well-ordered phases. Scanning-tunneling-microscope images show that the √3 × √3 structure is broken up into sub-100-Å domains that decrease in size with increasing Au coverage. The 6×6 phase can be described as a periodic arrangement of small √3 × √3 domains.

Equilibrium Re segregation is studied at a grain boundary in a single-phase W–25-at. %-Re alloy employing atom-probe field-ion microscopy. The grain-boundary concentration is measured, without data deconvolution, to be 73.8±5.45 at. % Re at an interface plane. This is the first direct proof that segregation at a grain boundary can be purely two dimensional, and that it can occur at a so-called low-energy interface.

We incorporate the exchange interaction into a simulation in which all electron motion, including that involved in screening, is treated explicitly with a molecular-dynamics simulation run concurrently within an ensemble Monte Carlo treatment of scattering. Exchange is treated for the first time in such an approach by a semiclassical modification of the molecular dynamics that takes full account of the Fermi statistics, and, in particular, does not violate the exclusion principle. A comparison is made with the short-time relaxation data of Becker et al.

We use transient optical hole burning and photoluminescence to investigate the static and dynamic electronic properties of 32-Å CdSe quantum dots. We observe a number of discrete electronic transitions, resolve LO-phonon progressions, and obtain homogeneous linewidths and electron–LO-phonon couplings. We find that the band-gap luminescence is not from the exciton state, but from a surface trapped state. Rapid (∼160 fs) trapping into these surface states results in long-lived (∼10–100 ns) bleach and induced-absorption features in pump-probe experiments.

Measurements of the mass-abundance spectra of sodium clusters from supersonic expansions are presented. The spectra show evidence of a regular spherical shell structure with magic numbers ${\mathit{N}}_0$ scaling approximately with the cube root of the number of sodium atoms N, and hence the number of delocalized (valence) electrons in the cluster. Altogether, twelve shell closings are observed, adding to the previously known shell closings, ${\mathit{N}}_0$=2, 8, 20, 40, 58, 92, and 138; the 8–12th magic numbers ${\mathit{N}}_0$=196, 260, 344, 440, and 558. The implications of shell structure in such large systems are discussed.

Nanometer-scale quantum wires have been directly produced using an epitaxial-growth technique. Modulation of the in-plane lattice constant of a GaAs/GaAlAs quantum well, grown over an InGaAs/GaAs strained-layer superlattice, laterally confines the carriers to one dimension. These novel structures are studied by luminescence and luminescence-excitation spectroscopies and by transmission electron microscopy. Large energy shifts and polarization anisotropy are observed. The results compare very well with a theoretical model based on the effective-mass approximation and elastic and phenomenological deformation-potential theories.

The negative-donor centers ${\mathit{D}}^{\mathrm{-}}$ in a magnetic field in semiconductors and quantum wells are studied by an effective-mass model that is solved exactly by a diffusion quantum Monte Carlo method. For ${\mathit{D}}^{\mathrm{-}}$ in bulk GaAs, excellent agreement is found between theory and magneto-optical experiments. For ${\mathrm{D}}^{\mathrm{-}}$ in a 100-Å GaAs/ ${\mathrm{Ga}}_{0.75}$${\mathrm{Al}}_{0.25}$As quantum well, a sevenfold increase in binding energy over that of the bulk case is predicted at zero field, and the calculated field-dependent ground-state energy is in good agreement with the interpretation of recent high-field magneto-optical data.

Photoemission studies with varying degrees of surface sensitivity are reported for the Ce 3d core-level and Ce 4f valence-band regions of the α-like Ce compounds ${\mathrm{CeIr}}_2$, ${\mathrm{CePd}}_3$, and ${\mathrm{CeRh}}_3$. In all cases studied, strong changes of the 4f electronic structure at the surface towards a more localized γ-like behavior are observed, requiring a reanalysis of previously reported photoemission spectra of α-like Ce compounds. Implications for an improved understanding of the surface-catalytic properties of Ce systems, as well as of the surface-electronic structure of narrow-band materials, are pointed out.

The electrical-transport properties of magnetic multilayered structures are dominated by three ingredients: (1) the scattering within layers that changes from one layer to another, (2) the additional scattering resistivity due to the roughness of the interfaces between layers, and (3) the resistivity that depends on the orientation of the magnetization of the magnetic layers. In the quasiclassical approach the boundary scattering is treated differently from other sources. Here we present a unified treatment of all sources of resistivity, and determine the origin of the giant magnetoresistance observed in Fe/Cr superlattices.

The combination of spin-polarization detection with core-level photoemission to give spin-polarized electron spectroscopy for chemical analysis provides new information on the oxidation of an iron surface. During the initial stage of oxidation the predominant phase is of a ferrimagnetic γ-${\mathrm{Fe}}_2$${\mathrm{O}}_3$ form. An observed antiferromagnetic coupling of this oxide with the iron substrate is attributed to a superexchange interaction, providing evidence for a possible site-exchange mechanism during the initial oxidation. Annealing transforms this oxide into an antiferromagnetic ${\mathrm{Fe}}_{\mathit{x}}$O form which is also present at the initial stage.

Ballistic transport through a two-dimensional cross junction is chaotic. The classical transmissivity, from which total transmission coefficients are obtained, exhibits self-similar regions of high transparency about a hierarchy of injection angles, ${\mathrm{\alpha }}_{\mathit{N}}$. These geometrical channels dominate the phase space of possible exits from the junction. Long dwell times within the junction, a manifestation of irregular scattering, strongly enhance the role of random processes in real devices.

We consider the motion of electrons through a mesoscopic ring in the presence of a classical, static, inhomogeneous, magnetic field. Zeeman interaction between the electron spin and this texture couples spin and orbital motion, and results in a Berry phase. As a consequence, the system supports persistent equilibrium spin and charge currents, even in the absence of conventional electromagnetic flux through the ring. We mention the possibility of analogous persistent mass and spin currents in normal ${}_{}{}^3{}_{}{}^{}\mathrm{He}$.

A localized two-spin bound state with the resultant spin S=1 is proposed as an elementary excitation of the Haldane state in Ni(${\mathrm{C}}_2$${\mathrm{H}}_8$${\mathrm{N}}_2$)${\mathrm{NO}}_2$(${\mathrm{ClO}}_4$) (NENP) and Ni(${\mathrm{C}}_3$${\mathrm{H}}_{10}$${\mathrm{N}}_2$)${\mathrm{NO}}_2$(${\mathrm{ClO}}_4$) (NINO). The bound state corresponds to the lowest excited triplet and behaves like a soliton or a small exciton. An ESR study has been done, and the resonance of the two-spin bound state is observed. The result is satisfactorily explained by the spin-cluster model and supports the Haldane conjecture. Various magnetic properties of NENP and NINO are well explained by the present model.

We show that even for fermionic lattice models with on-site interaction a mean-field Hamiltonian can be constructed, which–in analogy with spin-lattice models–becomes exact in the limit of high spatial dimensions d. Here the mean fields are fermion operators, rather than numbers. We use this method to obtain the exact solution of a simplified Hubbard model on a Bethe lattice for all temperatures. The order parameter is found to have the conventional mean-field form, but exhibits unusually rich behavior as a function of the interaction.

We report the first observation of soliton-antisoliton (fluxon-antifluxon) collision processes of all types (annihilation, passing through, and pair creation) in a discrete Josephson transmission line of niobium. These collision processes were directly measured not only in time, but also in space by a Josephson sampling system with precise control of the collision point. Negative phase shifts, contrary to the analytic solution for the sine-Gordon equation, were observed and attributed to the dissipation.