Showing papers by "Sheldon Schultz published in 1999"

Loop-wire medium for investigating plasmons at microwave frequencies

Abstract: We present numerical simulations and microwave measurements on a loop-wire structure that acts as an effective medium exhibiting a well-defined bulk plasma frequency in the microwave regime, with an effective negative dielectric function below this plasma frequency. The dependence of this plasmonic response on the self-inductance of the constituent wire elements is made explicit. A finite structure, approximately spherical, composed of this inductive medium is studied, and reveals subwavelength surface plasmon resonances below the bulk plasma frequency.

Writing and reading of single magnetic domain per bit perpendicular patterned media

Abstract: By fabricating patterned media with a large number of nanoscale single domain magnetic particles embedded in a nonmagnetic substrate, and by writing the magnetization for each of these particles in a desired direction, nonvolatile magnetic storage of information could reach densities much higher than what is currently thought possible for longitudinal continuous media. We have fabricated high aspect ratio perpendicular nickel columnar nanoparticles embedded in a hard Al2O3/GaAs substrate. We show that the magnetization states of the individual magnets can be controlled by demonstrating that prototype patterned "single magnetic domain per bit" data tracks can be written and read back using current magnetic information storage technology.

Generalized field propagator for arbitrary finite-size photonic band gap structures

Abstract: The electromagnetic (EM) properties of infinitely periodic dielectric and metallic systems have been studied extensively in the context of photonic band gap (PBG) structures [1,2], where powerful numerical methods exist that take advantage of the periodicity. Any physical realization of a PBG structure, however, is finite, and thus will have electromagnetic properties and phenomena distinct from an infinite structure. Such phenomena may include surface modes, sensitivity to boundary termination, or band-edge resonances [3 ‐ 5]. The objective of this Letter is twofold. First, we present a new method of computing the EM properties of a finite PBG structure. Second, we use this approach to study an array of finite-height dielectric cylinders on a substrate, illuminated with an evanescent field. This geometry was chosen to demonstrate the versatility of the scattering method, since it is a nontrivial three-dimensional finite system with open boundary conditions. Furthermore, this configuration is accessible experimentally, requiring only a single PBG layer which could readily be fabricated by lithographic methods. Accurate numerical methods previously reported for calculating the properties of finite PBG structures include modal method [6], finite difference time domain [7], transfer matrix [8,9], and repeated supercell [10]. Our method uses a scattering solution to obtain the EM modes and modes density associated with an arbitrary finite PBG region. The scattering solution is based on the Green’s tensor technique in the frequency domain. Let us consider a scattering system «sr; vd embedded in an infinite homogeneous background «Bsvd like the finite sn 3 md lattice of infinite cylinders shown in Fig. 1(a). We assume harmonic fields with the usual expf2ivtg dependence. When the system is illuminated by an incident field E 0 sr; vd, the total electric field Esr; vd is a solution of the Fredholm equation of the second kind, Esr; vd › E 0 sr; vd

Fabrication and Characterization of High Aspect Ratio Perpendicular Patterned Information Storage Media in an Al2O3/GaAs Substrate

Abstract: In a new approach, we have fabricated 6:1 aspect ratio magnetic nanocolumns, 60–250 nm in diameter, embedded in a hard aluminum-oxide/gallium-arsenide (Al2O3/GaAs) substrate. The fabrication technique uses the highly selective etching properties of GaAs and AlAs, and highly efficient masking properties of Al2O3 to create small diameter, high aspect ratio holes. Nickel (Ni) is subsequently electroplated into the holes, followed by polishing, which creates a smooth and hard surface appropriate for future reading and writing of the columns as individual bits for high density information storage. We have used magnetic force microscopy and scanning magneto-resistance microscopy to characterize the resulting magnets. We find the columns more magnetically stable than previously achieved with magnets embedded in a SiO2 substrate. Such stability is necessary before further writing of perpendicular patterned media can be demonstrated.

Perpendicular Patterned Media in an (Al0.9Ga0.1)2O3/GaAs Substrate for Magnetic Storage

Abstract: By using electron beam lithography, chemically assisted ion beam etching, and electroplating, we have fabricated high aspect ratio magnetic columns, 60–170 nm in diameter, embedded in an aluminum–gallium–oxide/gallium–arsenide [(Al0.9Ga0.1)2O3/GaAs] substrate. In our previous work, we demonstrated storage of data in individual columns spaced 2 µm apart. Here the electroplated Ni columns are in the form of tracks (0.5 and 0.25 µm in the down-track direction, and 1 µm in the cross-track direction), corresponding to areal densities of 1.3 and 2.6 Gbits/in.2, respectively. In this report we describe in more detail the issues in the fabrication of patterned media samples, such as dry etching and oxidation of AlGaAs, and electrodeposition of Ni into GaAs substrate. Initial characterization of the resulting magnets using magnetic force microscopy are also presented.