Magnetoplasmon excitations in an array of periodically modulated quantum wires

Motivated by the recent experiment of Hochgraefe et al., we have investigated the magnetoplasmon excitations in a periodic array of quantum wires with a periodic modulation along the wire direction. The equilibrium and dynamic properties of the system are treated self-consistently within the Thomas-Fermi-Dirac-von Weizsaecker approximation. A calculation of the dynamical response of the system to a far-infrared radiation field reveals a resonant anticrossing between the Kohn mode and a finite-wavevector longitudinal excitation which is induced by the density modulation along the wires. Our theoretical calculations are found to be in excellent agreement with experiment.Comment: 9 pages, 8 figure

Thomas-Fermi-Dirac-von Weizsacker hydrodynamics in laterally modulated electronic systems

We have studied the collective plasma excitations of a two-dimensional electron gas with an arbitrary lateral charge-density modulation. The dynamics is formulated using a previously developed hydrodynamic theory based on the Thomas-Fermi-Dirac-von Weizsacker approximation. In this approach, both the equilibrium and dynamical properties of the periodically modulated electron gas are treated in a consistent fashion. We pay particular attention to the evolution of the collective excitations as the system undergoes the transition from the ideal two-dimensional limit to the highly-localized one-dimensional limit. We also calculate the power absorption in the long-wavelength limit to illustrate the effect of the modulation on the modes probed by far-infrared (FIR) transmission spectroscopy.Comment: 27 page Revtex file, 15 Postscript figure

Magnetoplasmon excitations in arrays of circular and noncircular quantum dots

We have investigated the magnetoplasmon excitations in arrays of circular and noncircular quantum dots within the Thomas-Fermi-Dirac-von Weizs\"acker approximation. Deviations from the ideal collective excitations of isolated parabolically confined electrons arise from local perturbations of the confining potential as well as interdot Coulomb interactions. The latter are unimportant unless the interdot separations are of the order of the size of the dots. Local perturbations such as radial anharmonicity and noncircular symmetry lead to clear signatures of the violation of the generalized Kohn theorem. In particular, the reduction of the local symmetry from SO(2) to $C_4$ results in a resonant coupling of different modes and an observable anticrossing behaviour in the power absorption spectrum. Our results are in good agreement with recent far-infrared (FIR) transmission experiments.Comment: 25 pages, 6 figures, typeset in RevTe

Stability of SiC-masks for high resolution synchrotron X-ray lithography

Synchrotron X-ray lithography is a promising technique for high volume production of Ultra-LSI devices with latteral resolution down to 0.2 μm. Besides the powerful source, the X-ray stepper, and the high sensitive resist, mask technology is one of the main features in the development of X-ray lithography. For X-ray masks with high contrast a relatively thick absorbing pattern (0.8 μm) on a thin membrane (2.0 μm) is necessary. The achievable overlay accuracy depends mainly on the alignment accuracy of the X-ray stepper and of the stability of the masks. For a given stress in the absorping layer we will discuss the stability of X-ray masks which is mainly determined by the Young's modulus of the membrane material if we compare identical membrane geometries. SiC-membranes deposited by a high temperature CVD process can be fabricated with a Young's modulus as high as the bulk value (4.6×1011 N/m2) which is roughly a factor of 3 higher than for other relevant membrane materials. Membranes of 2 μm in thickness have been prepared with excellent transparency for synchrotron and optical radiation. A description of the preparation of the rigid SiC-membrane, as well as results of the transparency and the stability of these membranes against strong X-ray exposure will be given. For a high X-ray absorption a tungsten layer has been selected. Because of the thermal expansion coefficient which is comparable to SiC and the high Young's modulus tungsten is a promising material for sub-half micrometre pattern in a stress compensated absorber system. In view of X-ray masks with minimum distortion a description of the etch performance of the tungsten absorber system on SiC-masks will be given

Method and system for rapid thermal processing

A method and system for rapid thermal processing (RTP) comprising a 2-step heating process and using at least one HID lamp is disclosed, in which a ripple-pyrometry temp. measurement of the object by a temp. measurement unit can be conducted without disturbing the rapid thermal processing of the object. Substantially, this is achieved by driving the lamp by a driving circuit with an operating scheme (e.g., an AC-block current shape) with addnl. superimposed pulses with varying specifications, where the frequency of the superimposed pulse is chosen such, that they create a variation of the emitted light flux that is much faster than the variation induced by the light flash used for the 2nd-step flash-anneal RTP. This enables the emissivity detn. of the object, while only causing a short change in the total light flux to the object. [on SciFinder (R)