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Open Access Publications from the University of California

Scholarly Works (23 results)

  • Article
  • Peer Reviewed
UC Berkeley Previously Published Works (2005)

This letter demonstrates the application of scanning acoustic force microscopy for the characterization of film bulk acoustic resonators beyond detection of the gigahertz vibration amplitude and acoustic wave field imaging. We present a method to measure thermal expansion effects on these resonators by modulating the driving signal amplitude and then varying the modulation frequency from a few hertz to several tens of kilohertz. For the particular device considered here, we show the influence of thermal expansion effects on its electromechanical response and the acoustic wave field images. The thermal relaxation time constant of the resonator is measured and compared with a theoretical estimation based on the heat transfer analysis of the system. (c) 2005 American Institute of Physics.

    Cover page: Scanning acoustic force microscopy characterization of thermal expansion effects on the electromechanical properties of film bulk acoustic resonators
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2016)
    All-optical magnetic switching (AOS) is a recently observed rich and puzzling phenomenon that offers promising technological applications. However, a fundamental understanding of the underlying mechanisms remains elusive. Here we present a model for multishot helicity-dependent AOS in ferromagnetic materials based on a purely heat-driven mechanism in the presence of magnetic circular dichroism (MCD). We predict that AOS should be possible with as little as 0.5% of MCD, after a minimum number of laser shots heat the sample close to the Curie temperature. Finally, we qualitatively reproduce the all-optically switched domain patterns observed experimentally by numerically simulating the result of multiple laser shots on an FePtC granular ferromagnetic film.
      • Article
      LBL Publications (2007)
      We report measurements of spin-dependent scattering of conduction electrons by neutral donors in accumulation-mode field-effect transistors formed in isotopically enriched silicon. Spin-dependent scattering was detected using electrically detected magnetic resonance where spectra show resonant changes in the source-drain voltage for conduction electrons and electrons bound to donors. We discuss the utilization of spin-dependent scattering for the readout of donor spin-states in silicon based quantum computers.
        Cover page: Spin-Dependent Scattering off Neutral Antimony Donors in 28Si Field-Effect Transistors
        • Article
        LBL Publications (2004)
          Cover page: Development of single electron transistors as sensitive charge sensors for impurity spin quantum bits in silicon
          • Article
          • Peer Reviewed
          Lawrence Berkeley National Laboratory (2005)
            Cover page: Integration of scanning probes and ion beams
            • Article
            • Peer Reviewed
            Lawrence Berkeley National Laboratory (2008)

            We report the detection of single ion impacts through monitoring of changes in the source-drain currents of field effect transistors (FET) at room temperature. Implant apertures are formed in the interlayer dielectrics and gate electrodes of planar, micro-scale FETs by electron beam assisted etching. FET currents increase due to the generation of positively charged defects in gate oxides when ions (121Sb12+, 14+, Xe6+; 50 to 70 keV) impinge into channel regions. Implant damage is repaired by rapid thermal annealing, enabling iterative cycles of device doping and electrical characterization for development of single atom devices and studies of dopant fluctuation effects.

              Cover page: Detection of low energy single ion impacts in micron scale transistors at room temperature
              • Article
              Lawrence Berkeley National Laboratory (2006)

              We report Stark shift measurements for 121Sb donor electron spins in silicon using pulsed electron spin resonance. Interdigitated metal gates on top of a Sb-implanted 28Si epi-layer are used to apply electric fields. Two Stark effects are resolved: a decrease of the hyperfine coupling between electron and nuclear spins of the donor and a decrease in electron Zeeman g-factor. The hyperfine term prevails at X-band magnetic fields of 0.35T, while the g-factor term is expected to dominate at higher magnetic fields. A significant linear Stark effect is also resolved presumably arising from strain.

                Cover page: Stark tuning of donor electron spins in silicon
                • Article
                Lawrence Berkeley National Laboratory (2005)
                  Cover page: Ion Implantation with Scanning Probe Alignment
                  • Article
                  • Peer Reviewed
                  UC Berkeley Previously Published Works (2016)
                  Ultrafast optical heating of the electrons in ferrimagnetic metals can result in all-optical switching (AOS) of the magnetization. Here we report quantitative measurements of the temperature rise of GdFeCo thin films during helicity-independent AOS. Critical switching fluences are obtained as a function of the initial temperature of the sample and for laser pulse durations from 55 fs to 15 ps. We conclude that nonequilibrium phenomena are necessary for helicity-independent AOS, although the peak electron temperature does not play a critical role. Pump-probe time-resolved experiments show that the switching time increases as the pulse duration increases, with 10 ps pulses resulting in switching times of ∼13 ps. These results raise new questions about the fundamental mechanism of helicity-independent AOS.
                    Cover page: Role of electron and phonon temperatures in the helicity-independent all-optical switching of GdFeCo
                    • Article
                    Lawrence Berkeley National Laboratory (2005)
                      Cover page: Electrical activation and spin coherence of ultra low dose antimony implants in silicon
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