Preroughening transitions in a model for Si and Ge (001) type crystal surfaces

The uniaxial structure of Si and Ge (001) facets leads to nontrivial topological properties of steps and hence to interesting equilibrium phase transitions. The disordered flat phase and the preroughening transition can be stabilized without the need for step-step interactions. A model describing this is studied numerically by transfer matrix type finite-size-scaling of interface free energies. Its phase diagram contains a flat, rough, and disordered flat phase, separated by roughening and preroughening transition lines. Our estimate for the location of the multicritical point where the preroughening line merges with the roughening line, predicts that Si and Ge (001) undergo preroughening induced simultaneous deconstruction transitions.Comment: 13 pages, RevTex, 7 Postscript Figures, submitted to J. Phys.

Triviality of the prolongation algebra of the Kuramoto-Sivashinsky equation

The authors apply the well known Wahlquist-Estabrook prolongation technique to the Kuramoto-Sivashinsky equation. The prolongation algebra turns out to be trivial in the sense that it is commutative. This supports nonintegrability of the equation

The Ti/c-Si solid state reaction : III. The low-temperature reaction kinetics

Thin Ti layers (≈10nm) are grown on top of a clean Si(111) substrate. Heating these layers initiates a solid state reaction, yielding a monosilicide phase at ≈350°C and a C49 disilicide at ≈450°C. The present study concerns the growth kinetics of both phases by means of ellipsometry. A diffusion-limited growth kinetics is found for the monosilicide formation. However, two growth rates are observed, a fast initial one and a slow terminal growth rate. An enhanced Si diffusion in atomically disordered regions as compared to well ordered regions (grains or clusters) could be an explanation. From the measurements we have found a value of 2×10-15 cm2/s for the diffusion coefficient at ≈370°C and an activation energy of 0.62 ± 0.1 eV. Both values correspond to the fast process. Subsequently increasing the temperature to ≈450°C permits the growth of the homogeneous C49 TiSi2 phase. For this process, both planar layer growth and intermixing are observed, however, quantitative results could not be derived from the present study

Holographic QCD in the Veneziano limit at finite Magnetic Field and Chemical Potential

We investigate the phase diagram of QCD-like gauge theories at strong coupling at finite magnetic field $B$, temperature $T$ and baryon chemical potential $\mu$ using the improved holographic QCD model including the full backreaction of the quarks in the plasma. In addition to the phase diagram we study the behavior of the quark condensate as a function of $T$, $B$ and $\mu$ and discuss the fate of (inverse) magnetic catalysis at finite $\mu$. In particular we observe that inverse magnetic catalysis exists only for small values of the baryon chemical potential. The speed of sound in this holographic quark-gluon plasma exhibits interesting dependence on the thermodynamic parameters.Comment: 7 pages, 6 figure

A novel derivative ellipsometric method for the study of the growth of thin films: Titanium

The growth of a titanium film at room temperature from an evaporation source on a silicon substrate covered by its native oxide layer is continuously monitored with an ellipsometer at three wavelengths. The momentary positions and the derivatives of the trajectories thus obtained in the (Δ, Ψ) plane can be used for uniquely determining the momentary thickness and the momentary dielectric constants of the layer at each of the wavelengths. The optical properties of the titanium, which reflect the film structure and defect rate, strongly depend upon the growth conditions; the top region of a film approximately 40 nm thick appears to contain more voids and lattice defects than the region near the substrate

Systematic and random errors in rotating-analyzer, ellipsometry

Errors and error sources occurring in rotating-analyzer ellipsometry are discussed. From general considerations it is shown that a rotating-analyzer ellipsometer is inaccurate if applied at P = 0° and in cases when π = 0° or where Δ is near 0° or 180°. Window errors, component imperfections, azimuth errors and all other errors may, to first order, be treated independently and can subsequently be added. Explicit first-order expressions for the errors δΔ and δπ caused by windows, component imperfections, and azimuth errors are derived, showing that all of them, except the window errors, are eliminated in a two-zone measurement. Higher-order errors that are due to azimuth errors are studied numerically, revealing that they are in general less than 0.1°. Statistical errors are also discussed. Errors caused by noise and by correlated perturbations, i.e., periodic fluctuations of the light source, are also considered. Such periodic perturbations do cause random errors, especially when they have frequencies near 2ωA and 4ωA