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  • 1
    Electronic Resource
    Electronic Resource
    Laser-induced crystallization phenomena in GeTe-based alloys. III. GeTeSe alloys for a CD compatible erasable disk (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8349-8356 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel multipulse laser technique has been used to study the crystallization behavior of the GeTeSe ternary system, and the dependence of the nucleation and growth rates on composition has been related to the optical and structural properties. We show that the Se content is dominant in determining both the nucleation rate and the amorphous optical constants, while the crystal-growth speed depends primarily on the single or multiphase nature of the resultant crystalline state. In this respect compositions on the GeTe-GeSe line are unique in that they are single-phase for a Se content up to 25%. This characterization of both the optical and crystallization behavior has allowed us to identify materials suitable for use in a CD-compatible erasable optical disk based on the phase change principle, in which local amorphous regions in a crystalline film represent data bits. Readout compatibility with a CD imposes extremely stringent conditions on the reflection from the amorphous and crystalline states as well as the crystallization rate, which previous materials had been unable to satisfy. We present optical recording data on a disk using a composition on the GeTe-GeSe line, Ge50Te25Se25, in a five-layer stack, and show that the criteria for a fully CD-compatible erasable disk are fulfilled. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362547
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  • 2
    Electronic Resource
    Electronic Resource
    Lorentz microscopy on dynamically written domains in GdTbFe (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 963-964 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter a new method for the observation of thermomagnetically written domains using Lorentz electron microscopy is discussed. Domains are written in a GdTbFe layer deposited on a specially prepared silicon wafer disk, provided with Si3N4 windows. This allows direct observation by Lorentz microscopy of the magnetization patterns dynamically written under recording conditions. It is shown that by locally heating the GdTbFe layer with a continuous laser beam, combined with high-frequency switching of the magnetic field, very high storage densities can be achieved. Domains with a length of 0.25 μm in the direction of disk rotation could be written.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101420
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  • 3
    Electronic Resource
    Electronic Resource
    Initial Response of Butterflies to an Overstory Reduction and Slash Mulching Treatment of a Degraded Piñon-Juniper Woodland (2004)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 12 (2004), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Overstory reduction and slash mulching (ORSM) has been shown to be an effective means for increasing herbaceous cover and diversity in degraded piñon (Pinus edulis) and juniper (Juniperus monosperma) woodlands of north-central New Mexico. Local fire history, tree age-class structure, and grazing records suggest that many areas now occupied by dense piñon-juniper woodlands were formerly more open, with grassy understories that supported well-developed soils and a fire regime. At Bandelier National Monument, studies are evaluating the use of ORSM treatments as a restoration management tool. In 1999 and 2001, we evaluated the effects of an ORSM treatment implemented in 1997 upon butterfly abundance and species richness between a pair of treated and control watersheds. Butterfly abundance and species richness were significantly greater on the treated watershed in both years, and these measures were correlated with significant increases in forb and grass cover in the treated watershed. Five of the 10 most common nectar and larval host plants had significantly greater cover in the treated watershed, including the legume Lotus wrightii. Our results suggest that the increased herbaceous cover resulting from an ORSM treatment of a single watershed induced a positive, initial response by butterflies. Using butterflies as indicators of site productivity and species richness, our results suggest ORSM is a promising technique for restoring biodiversity in degraded piñon-juniper woodlands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1061-2971.2004.00212.x
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  • 4
    Electronic Resource
    Electronic Resource
    Laser-induced crystallization phenomena in GeTe-based alloys. I. Characterization of nucleation and growth (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4906-4917 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The laser-induced crystallization behavior of GeTe-based amorphous alloy thin films has been quantitatively studied by local reflection measurements with a focused 780 nm laser. The use of multiple laser pulse sequences enables the nucleation rate and crystal-growth speed to be separately deduced, allowing the compositional variation of both these processes to be followed. This not only gives detailed information on the crystallization mechanism, but also allows the fine tuning of phase change alloy compositions for use in erasable optical recording. The differences between the as-deposited and melt-quenched amorphous phases are also discussed. In particular, it is shown that the crystallization speed of the as-deposited layer can differ by over an order of magnitude from that of the melt-quenched amorphous layer. The as-deposited state can, however, be transformed into a modified amorphous state equivalent to that obtained by melt quenching a previously crystalline layer. This allows the determination of the optical constants and crystallization speeds of the amorphous state written during optical recording. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359779
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  • 5
    Electronic Resource
    Electronic Resource
    Laser-induced crystallization phenomena in GeTe-based alloys. II. Composition dependence of nucleation and growth (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4918-4928 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The laser-induced crystallization behavior of GeTe-based amorphous alloys has been measured with a novel multipulse laser technique. This enables the composition dependence of the nucleation rate and crystal growth speed to be independently followed. Two types of crystallization are investigated. The first involves single-phase crystallization of quaternary alloys based on Ge39Sb9Te52, in which the composition dependence of nucleation and growth is followed as Se, S, Sn, and Si are included. Both the nucleation rate and crystal-growth speed vary exponentially with the composition, and a correlation is found between crystallization behavior and bond strengths. The second involves multiphase crystallization in the GeSbTe ternary system. It is shown that the observed variations in crystallization behavior primarily arise from the composition dependence of nucleation rather than crystal growth. The implications of this finding for the importance of long range diffusion during crystallization in the GeSbTe system are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359780
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  • 6
    Electronic Resource
    Electronic Resource
    Hysteresis, microstructure, and magneto-optical recording in Co/Pt and Co/Pd multilayers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2264-2271 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The factors that influence the coercive field Hc and the shape of the magnetic hysteresis loop for Co/Pt multilayers (MLs), applied as a magneto-optical (MO) recording medium, have been investigated. The hysteresis loop of MLs, made by evaporation of Kr sputtering, became more rectangular when the total film thickness was reduced, i.e., the saturation field Hs decreased and the nucleation field Hn increased. Hs was calculated using a stripe domain model and Hn was modeled assuming that nucleation took place at a field that destabilized small vestigial magnetic domains. Both models assumed that domain walls can move in the ML film and the agreement with experiment was good. However, these models could not explain the hysteresis loops for the MLs deposited on a thick Pt base layer or made at high sputter gas pressure. These MLs showed a more particulate microstructure and the hysteresis loop was sheared, consistent with magnetic reversal by uniform rotation rather than domain-wall motion. From thermomagnetic recording experiments it was concluded that these latter MLs were less suitable as a MO recording medium because of higher noise in spite of the larger Hc. Co/Pt disks made by either evaporation or Kr sputtering showed lower noise and a higher carrier-to-noise ratio than those deposited on a Pt base layer or made by Ar sputtering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349419
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  • 7
    Electronic Resource
    Electronic Resource
    Scanning magnetic force microscopy on Co/Pt magneto-optical disks (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2413-2422 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High resolution images of domains written on Co/Pt magneto-optical disks were obtained using scanning magnetic force microscopy. The key advantage of this technique compared to electron microscopy techniques is that regular disks can be used. We studied the influence of the multilayer composition and preparation conditions as well as the effect of the pregrooves and the incorporation of a Pt underlayer, on the structure of the domains on the disk. Marks were written both with laser and magnetic field modulation, and carrier and noise levels were determined. Regularly shaped and subdomain-free marks for both writing schemes were obtained for multilayers with about 4-A(ring)-thick Co layers and Pt layers thinner than 15 A(ring). The magnitude of the coercive field had only a minor influence on the domain structure. On the other hand, the preparation conditions and the structure of the base layers have a large impact on the recording conditions and domain structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349393
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  • 8
    Electronic Resource
    Electronic Resource
    Co/Pt and Co/Pd multilayers as new magneto-optical recording media (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4966-4966 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we will discuss Co/Pt and, to a lesser extent, Co/Pd multilayers optimized for magneto-optical storage applications. Perpendicular magnetic anisotropy and square hysteresis loops are achieved for multilayers with a total thickness below about 200 A(ring) if they consist of very thin ((approximately-equal-to)4 A(ring)) Co layers alternated with 10–20-A(ring) Pt layers. Multilayer made by evaporation show a high coercivity ((approximately-greater-than)100 kA/m) and have proven to be suitable as magneto-optical recording medium. Recently we showed that Co/Pt layers with high coercivity can be made by sputtering as well, if not Ar but Kr is used as sputter gas.1 We will discuss the properties of Co/Pt multilayers in relation to the preparation technique and will present magneto-optical recording results for both evaporated and sputtered Co/Pt multilayer films. The written domain patterns can be very regular, as observed by scanning magnetic force microscopy, and a CNR as high as 55 dB (1 MHz carrier, 5 m/s, 30 kHz BW) is observed. The good oxidation and corrosion resistance together with increasing Kerr effect towards shorter wavelengths, where higher storage densities are possible, make that Co/Pt multilayers are attractive new magneto-optical recording media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348190
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  • 9
    Electronic Resource
    Electronic Resource
    Dynamic writing of magnetic domains in GdTbFe: Observations made by Lorentz microscopy (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4917-4923 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper the sizes and shapes of thermally written magnetic domains in a GdTbFe layer are discussed. The magneto-optical layer is deposited on a specially prepared silicon wafer disk, provided with Si3N4 windows. This allows dynamic writing of domains under realistic recording conditions on a rotating substrate and direct observation of the magnetization patterns in the transmission electron microscope, using Lorentz microscopy. Domain patterns were written in two different ways: With the first method, laser modulation (LM), the laser beam was modulated while applying a fixed field. In the second method, magnetic field modulation (MFM), the laser was on continuously and the applied magnetic field was modulated. With LM it was observed that both size and shape are closely dependent on the magnitude of the applied field. This behavior is in good agreement with observations made with optical readout of similar magneto-optical disks. Domains written with MFM have somewhat irregular contours. The degree of irregularity depends on the magnitude of the applied magnetic field and its switching time. Reduction of these irregularities can be achieved by simultaneously modulating the laser beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343761
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  • 10
    Electronic Resource
    Electronic Resource
    Ultralow damage depth by electron cyclotron resonance plasma etching of GaAs/InGaAs quantum wells (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1137-1139 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dry etch induced damage of GaAs/InGaAs/GaAs heterostructures in an electron cyclotron resonance (ECR) argon discharge has been investigated as a function of additional radio frequency self-biasing of the sample and process pressure in argon ECR discharges. We used depth resolved photoluminescence measurements to determine the influence of the etch process on the samples. We observe a decreasing damage depth for smaller bias voltages reaching its lowest value of 1.7 nm at 20 V bias and a pressure of 0.15 Pa. For lower pressures we observe a strong increase of the damage, which is attributed predominantly to high energetic vacuum ultraviolet radiation from the ECR region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108767
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