A5005768286- Magnetic properties of thin films
- Fullerene Chemistry and Applications
- Graphene research and applications
- Quantum and electron transport phenomena
- Advanced Memory and Neural Computing
- Semiconductor materials and devices
- Molecular Junctions and Nanostructures
- Ferroelectric and Negative Capacitance Devices
- Phase-change materials and chalcogenides
- Semiconductor Quantum Structures and Devices
- Advanced Chemical Physics Studies
- Advanced Physical and Chemical Molecular Interactions
- Diamond and Carbon-based Materials Research
- Physics of Superconductivity and Magnetism
- Theoretical and Computational Physics
- Transition Metal Oxide Nanomaterials
- Magnetic Properties and Applications
- Advancements in Semiconductor Devices and Circuit Design
- Copper Interconnects and Reliability
- Surface and Thin Film Phenomena
- Boron and Carbon Nanomaterials Research
- Quantum optics and atomic interactions
- Force Microscopy Techniques and Applications
- Block Copolymer Self-Assembly
- Optical Coatings and Gratings
Western Digital (United States)
2015-2025
Hitachi Global Storage Technologies (United States)
2009-2015
Western Digital (Japan)
2013-2014
Stanford University
2007-2011
Lawrence Berkeley National Laboratory
2002-2009
University of California, Berkeley
2002-2008
Bit Patterned Media (BPM) for magnetic recording provide a route to densities $>1 Tb/in^2$ and circumvents many of the challenges associated with conventional granular media technology. Instead bit on an ensemble random grains, BPM uses array lithographically defined isolated islands, each which stores one bit. Fabrication is viewed as greatest challenge its commercialization. In this article we describe fabrication method combines e-beam lithography, directed self-assembly block copolymers,...
We have used scanning tunneling microscopy and spectroscopy to study the electronic structure of individual ${\mathrm{C}}_{60}$ molecules adsorbed onto Au(111) Ag(100) surfaces. on show an increase in HOMO-LUMO gap 0.6 eV compared Ag(100). Splitting LUMO manifold is suppressed for Au(111), contrast strong splitting observed Our data implies a intramolecular Coulomb energy as Topographs energy-resolved spectral maps, however, nearly identical features indicate similar influence two substrates...
Recent advances in scanning tunneling microscopy have allowed the observation of Kondo effect for individual magnetic atoms. One hallmark is a strong temperature-induced broadening resonance. In order to test this prediction impurities, we investigated temperature dependent electronic structure isolated Ti atoms on Ag(100). We find that resonance strongly broadened range T = 6.8 K 49.0 K. These results are good agreement with theoretical predictions impurities Fermi liquid regime, and...
We have used scanning tunneling spectroscopy to spatially map the energy-resolved local density of states individual ${\mathrm{C}}_{\mathrm{60}}$ molecules on Ag(100) surface. Spectral maps were obtained for molecular derived from HOMO, LUMO, and $\mathrm{L}\mathrm{U}\mathrm{M}\mathrm{O}+1$ orbitals, revealing new details inhomogeneous electronic structure. Spatial inhomogeneities are explained using ab initio pseudopotential functional calculations. These calculations emphasize need...
Scaling laws and universality play an important role in our understanding of critical phenomena the Kondo effect. We present measurements nonequilibrium transport through a single-channel quantum dot at low temperature bias. find that low-energy conductance is consistent with between bias characterized by quadratic scaling exponent, as expected for spin-1/2 show are well described universal function two parameters.
Abstract Phase change memory (PCM) is a rapidly growing technology that not only offers advancements in storage-class memories but also enables in-memory data processing to overcome the von Neumann bottleneck. In PCMs, storage driven by thermal excitation. However, there limited research regarding PCM properties at length scales close cell dimensions. Our work presents new paradigm manage transport cells manipulating interfacial resistance between phase unit and electrodes without...
We report a method for controllably attaching an arbitrary number of charge dopant atoms directly to single, isolated molecule. Charge-donating K adsorbed on silver surface were reversibly attached C60 molecule by moving it over with scanning tunneling microscope tip. Spectroscopic measurements reveal that each atom donates constant amount (approximately 0.6 electron charge) the host, thereby enabling its molecular electronic structure be precisely and tuned.
Bit patterned media (BPM) provide an alternative to conventional granular thin film recording media, circumventing the challenges of managing grain size and its associated noise thermal stability issues in media. A viable fabrication strategy involves creation a master pattern by rotary-stage e-beam lithography directed self-assembly block copolymers, followed replication via UV-cure nanoimprint transfer magnetic ion beam etching. These steps have been demonstrated for 150 Gdot/cm <sup...
We have observed tunable negative differential resistance (NDR) in scanning tunneling spectroscopy measurements of a double layer C60 molecules on metallic surface. Using simple model we show that the NDR behavior is explained by voltage-dependent changes barrier height.
We present a low-temperature scanning tunneling microscopy (STM) study of K x C 60 monolayers on Au(111) for 3 ≤ 4. The STM spectrum evolves from one that is characteristic metal at = to an insulator This electronic transition accompanied by dramatic structural rearrangement the molecules. Jahn-Teller effect, charge-induced mechanical deformation molecular structure, directly visualized in 4 monolayer single-molecule level. These results, along with theoretical analyses, provide strong...
We studied highly L10-ordered FePtAg–C nanogranular film as a potential high-density storage medium in thermally assisted magnetic recording (TAR). A 6.4-nm-thick with perpendicular coercivity of 37 kOe and an average grain size 6.1±1.8 nm was fabricated on oxidized silicon substrate 10 MgO interlayer at 450 °C. The time-dependence measurement remnant showed the energy barrier Eb = 7.6 eV ∼300 kBT room temperature, meaning excellent thermal stability for long-term data storage. Static tester...
Abstract Amorphous chalcogenide alloys are key materials for data storage and energy scavenging applications due to their large non-linearities in optical electrical properties as well low vibrational thermal conductivities. Here, we report on a mechanism suppress the transport representative amorphous system, silicon telluride (SiTe), by nearly an order of magnitude via systematically tailoring cross-linking network among atoms. As such, experimentally demonstrate that fully dense SiTe...
We report fabrication and characterization of double magnetic tunnel junction (DMTJ) magneto-resistive random access memory cells that exhibit characteristic about 2X reduction switching current compared to single reference layer junctions, but maintain high tunneling magnetoresistance ratio exceeding 120 %, coercive fields the free more than 2 kOe for 65 nm cells, magnetically stable layers with pinning above 6 kOe. Switching analysis performed two different relative magnetization...
We have spatially resolved the local electronic structure of a ${\mathrm{C}}_{60}$ monolayer on Ag(001) using scanning tunneling spectroscopy at $T=7\mathrm{K}.$ Our measurements resolve four band states derived from highest occupied molecular orbital, lowest unoccupied orbital (LUMO), and LUMO+1. observe spatial inhomogeneity in energy-resolved density states, which reflects internal structure. In addition, we are able to orientation coexisting bright dim molecules monolayer. This...
We demonstrate a 2.5-fold coercivity reduction in FePt based exchange coupled composite bit patterned media (ECC-BPM) by coupling lower anisotropy Co/Pd–Co/Ni-multilayer system to the top of high L10 film. Furthermore tight switching field distribution (SFD) reduces SFD ECC-BPM compared single layer The relative amount and these arrays agree with corresponding micromagnetic simulations.
We have measured the elastic and inelastic tunneling properties of isolated $\mathrm{Gd}@{\mathrm{C}}_{82}$ molecules on Ag(001) using cryogenic scanning spectroscopy. find that dominant channel is spatially well localized to a particular region molecule. Ab initio pseudopotential density-functional theory calculations indicate this arises from vibrational cage mode. further show observed localization explained by strong in molecular electron-phonon coupling
We show an electron interferometer between a quantum point contact (QPC) and scanning gate microscope (SGM) tip in two-dimensional gas. The QPC SGM act as reflective barriers of lossy cavity; the conductance through system thus varies function distance tip. characterize how temperature, wavelength, cavity length, reflectivity barrier affect interferometer. report checkerboard interference patterns near and, when injecting electrons above or below Fermi energy, effects dephasing.
Abstract A dilute concentration of magnetic impurities can dramatically affect the transport properties an otherwise pure metal. This phenomenon, known as Kondo effect , originates from interactions individual with conduction electrons. Nearly a decade ago, was observed in new system, which moment stems single unpaired spin lithographically defined quantum dot, or artificial atom. The discovery atoms spurred revival study physics, due part to unprecedented control relevant parameters these...
Using scanning gate microscopy (SGM), we probe the scattering between a beam of electrons and two-dimensional electron gas (2DEG) as function beam's injection energy, distance from point. At low energies, find in scatter by small angles, has been previously observed. high surprising result: placing SGM tip where it backscatters increases differential conductance through system. This effect is explained nonequilibrium distribution localized region 2DEG near Our data indicate that spatial...
We examine the magnetic properties and recording performance of bit patterned exchange coupled composite (ECC) media at different island aspect ratios. The ECC consists Co/Pd Co/Ni multilayers whose coupling is controlled using Pd interlayers. show that this multilayer system can be tuned to provide writeable with a low switching field distribution for recording. 100 Gb/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> shows sub 1e-4...
We demonstrate a technique for measuring the intrinsic bit-error-rate as function of write misregistration in bit patterned media. examine recording performance at densities 100, 200, and 320 Gigabits per square inch (Gb/in2) find that on-track margin error rates below 10−4 is ∼1/4 length all three densities. two-dimensional sub rate 100 200 Gb/in2 with 10−3 Gb/in2.
Chemically ordered 5 nm-thick L1₀ FePtCu films with strong perpendicular magnetic anisotropy were post-patterned by nanoimprint lithography into a dot array over 3 mm-wide circumferential band on inch Si wafer. The dots diameter of 30 nm and center-to-center pitch 60 appear as single domain reveal an enhanced switching field compared to the continuous film. We demonstrate successful recording track using shingled writing conventional hard disk drive write/read head.
We report the observation of Coulomb blockade in a quantum dot contacted by two point contacts each with single fully transmitting mode, system thought to be well described without invoking interactions. Below 50 mK we observe periodic oscillation conductance gate voltage, corresponding residual quantization charge. From temperature and magnetic field dependence, infer oscillations are mesoscopic blockade, type caused electron interference an otherwise open system.
We studied highly L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> -ordered FePtAg-C nanogranular film as a potential high-density storage medium for thermally assisted magnetic recording (TAR). A 6.4-nm-thick was fabricated on an oxidized silicon substrate with 10-nm MgO underlayer at 550°C, the perpendicular coercivity of 35 kOe, and average grain size 6.2 ± 1.4 nm. The time-dependence measurement remnant results in energy barrier E...