Henryk Birecki

Thermal stability of magneto‐optic quadrilayers

The thermal stability of sputtered TbFeCo thin films in magneto‐optic quadrilayer structures containing Si3N4, SiO, and SiO2 dielectrics has been examined. The observed changes in coercivity upon annealing are attributed to two parallel mechanisms: structural relaxation in the amorphous magnetic alloy and preferential oxidation of Tb at the TbFeCo/SiO and TbFeCo/SiO2 interfaces. Kinetic modeling has revealed that a spectrum of activation energies is required to explain the relaxation data, whereas a single activation energy of 1.65 eV describes the oxidation process.

Modeling domain behavior in magneto‐optic recording

Two methods of modeling the domain behavior during the magneto‐optic write process are reviewed and contrasted. One model divides the medium into discrete cells and attempts to find a domain configuration which minimizes the energy. The second model assumes that the wall is continuous and finds the domain configuration which minimizes the pressure everywhere on the wall. The predictions of the models are compared. An ad hoc model for the nucleation process is also presented.

Electron current extraction from radio frequency excited micro-dielectric barrier discharges

Micro dielectric barrier discharges (mDBDs) consist of micro-plasma devices (10–100 μm diameter) in which the electrodes are fully or partially covered by dielectrics, and often operate at atmospheric pressure driven with radio frequency (rf) waveforms. In certain applications, it may be desirable to extract electron current out of the mDBD plasma, which necessitates a third electrode. As a result, the physical structure of the m-DBD and the electron emitting properties of its materials are important to its operation. In this paper, results from a two-dimensional computer simulation of current extraction from mDBDs sustained in atmospheric pressure N2 will be discussed. The mDBDs are sandwich structures with an opening of tens-of-microns excited with rf voltage waveforms of up to 25 MHz. Following avalanche by electron impact ionization in the mDBD cavity, the plasma can be expelled from the cavity towards the extraction electrode during the part of the rf cycle when the extraction electrode appears anodi...

The optics of twisted nematic liquid‐crystal displays

A simple two‐layer model explaining all the main features of angular and voltage dependences of light transmission through twisted nematic liquid‐crystal devices is proposed. The model is based on the physical symmetries of the twisted nematic structure and, for the first time, provides a qualitative description of transmission patterns without need for detailed calculations.

Ultracompact electron-beam column

An electron optical system with an array of columns was developed for an electron-beam addressable data storage device that has the form factor of Compact Flash and a capacity >10GB. The electron optical column occupies an area <2500μm2 and produces a focused beam with current <100nA and a diameter <40nm. An extended-area electron source that consists of an array of randomly distributed hemispherical-grain polysilicon nodules was developed. The field at the nodules is enhanced by a factor of 3–5 compared with metal-insulator-semiconductor structures with smooth cathodes. Electron emission consequently occurs predominantly at the nodules. A maximum current density of ∼20A∕cm2 was achieved with this electron source. The multiplicity of emission sites helps us to reduce significantly the emission current noise. An electron optical column to focus the emission from this extended source into a diameter <30nm was also developed. The column consists of a single main lens and an array of auxiliary nanolenses. The...

Erasable Optical Liquid Crystal Disc Memory

An erasable optical disc memory with smectic liquid crystal (LC) as the active medium has been fabricated and tested. Using appropriate dark field optics, we have demonstrated writing, reading and erasing at data rates of 13.5 MHz with a bit spacing of 1.25 microns. Although not all problems with this memory have been solved, we think the concept is viable with an expanded research effort in materials and system aspects.

Magnetooptic Quadrilayer Reliability And Performance

The stability of magnetooptic recording films based on rare earth - transition metal alloys has been investigated. Experimental results show two distinct degradation processes, one of which has been identified as oxidation of the active layer, the other of which appears to be a thermally activated relaxation of the microstructure. Performance data are presented for newly developed, stable structures which exhibit virtually unchanged 55-60 dB C/N ratios after annealing at 200 degrees centigrade in air. Environmental stability is discussed.

Charging of moving surfaces by corona discharges sustained in air

Atmospheric pressure corona discharges are used in electrophotographic (EP) printing technologies for charging imaging surfaces such as photoconductors. A typical corona discharge consists of a wire (or wire array) biased with a few hundred volts of dc plus a few kV of ac voltage. An electric discharge is produced around the corona wire from which electrons drift towards and charge the underlying dielectric surface. The surface charging reduces the voltage drop across the gap between the corona wire and the dielectric surface, which then terminates the discharge, as in a dielectric barrier discharge. In printing applications, this underlying surface is continuously moving throughout the charging process. For example, previously charged surfaces, which had reduced the local electric field and terminated the local discharge, are translated out of the field of view and are replaced with uncharged surface. The uncharged surface produces a rebound in the electric field in the vicinity of the corona wire which in turn results in re-ignition of the discharge. The discharge, so reignited, is then asymmetric. We found that in the idealized corona charging system we investigated, a negatively dc biased corona blade with a dielectric covered ground electrode, the discharge is initially sustained by electron impact ionization from the bulk plasma and then dominated by ionization from sheath accelerated secondary electrons. Depending on the speed of the underlying surface, the periodic re-ignition of the discharge can produce an oscillatory charging pattern on the moving surface.

Multiplexing Limits of Twisted Nematic Liquid Crystal Displays and Implications for the Future of High Information Content LCDs

“Why have liquid crystal displays (LCDs) become important in the decade of the 1970’s?” The answer is that LCDs have satisfied a major need in the world of electronic displays (see Fig. 1), i.e., a need for compact displays with power dissipations on the order of microwatts per square centimeter of active display area. That such a need existed has been well confirmed by the commercial success of multiple generations of watches, calculators, electronic games and other portable instruments incorporating LCDs. Although there are many more dimensions to the display world that those accounted for in Fig. 1, the critical dimension resulting in the commercial proliferation of LCDs in the 1970’s was power dissipation.

Glow-like atmospheric pressure micro-discharges produced by charge rollers

Summary form only given. Conductive charge rollers (CR) are used in print engines for surface charging of the cylindrical photoconductor (PC) at atmospheric pressure. The charging process is essentially a dielectric-barrier-discharge (DBD). Microplasmas are produced in the narrowing gap between the CR and PC, which then charges the PC. The streamer-like plasmas can be terminated by surface charging of the PC if operated with a dc or quasi-dc voltage on the CR. From a practical matter, the surfaces of both the CR and PC are rotating. The rotation of the PC brings in uncharged surface which reestablishes the voltage between the CR and PC, and re-ignites the plasma. As a result, a periodic charging pattern on the PC surface may be formed. Under certain operating conditions, a glow-like discharge was simulated in the CR and a quasi-dc current was collected on the PC surface. These behaviors and the uniformity of surface charging are sensitive to the speed of the PC and applied voltage.In this presentation, we will discuss the behavior of atmospheric pressure microplasmas sustained in air between the CR and PC, and the charging properties on the PC surface using results from a 2-dimensional simulation. The model, nonPDPSIM, solves Poissons equation and transport equations for charge and neutral species and the electron energy conservation equation for electron temperature. A Monte Carlo simulation is used for tracking sheath accelerated electrons. Rate and transport coefficients for bulk electrons are obtained from local solutions of Boltzmanns equation for the electron energy distribution. Radiation transport is addressed using a Greens function approach.