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Mar 2002

Volume 73, Issue 3, pp. 1103-1683

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back to top CONDENSED MATTER; MATERIALS

Velocity distribution measurement and two-wire field effects for electric deflection of a neutral supersonic cluster beam

G. Tikhonov, K. Wong, V. Kasperovich, and V. V. Kresin

Rev. Sci. Instrum. 73, 1204 (2002); http://dx.doi.org/10.1063/1.1447304 (8 pages) | Cited 9 times

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The basic principle of deflection of a beam of polarizable particles by an inhomogeneous electric field is straightforward, but its application to realistic beams having spatial and velocity distributions of finite widths requires special care. We present a detailed treatment of these issues as developed for a measurement of electric polarizabilities of alkali clusters in a continuous supersonic beam. We begin by describing a general technique for extracting the beam velocity distribution from the time-of-flight profile generated by two separate 50–50 gating choppers. This method yields accurate model-free information directly from the experimental profile, without errors associated with detector delays, and with high signal throughput. We then use a simple but accurate approximation for the deflecting field variation over space, and derive analytical expressions for the deflection of beams of finite width and finite velocity spread. This allows us to evaluate the magnitude of a number of corrections to the ideal formula; the results are applicable to optimization of various electric and magnetic field deflection experiments. Finally, we demonstrate, both theoretically and experimentally, the phenomenon of local velocity variations across the beam profile which arise as a result of deflection. © 2002 American Institute of Physics.
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37.20.+j Atomic and molecular beam sources and techniques
07.77.Gx Atomic and molecular beam sources and detectors
36.40.-c Atomic and molecular clusters

The characterization of a magnetron-sputter-type negative-ion source

Nam-Woong Paik and Steven Kim

Rev. Sci. Instrum. 73, 1212 (2002); http://dx.doi.org/10.1063/1.1445865 (5 pages) | Cited 5 times

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Characteristics of an 8-in.-diam magnetron-sputter-type negative-ion source (MSNIS) were investigated. A negative sputtered ion beam is generated by a cesium-induced sputter type secondary negative-ion beam emission process. The plasma properties were obtained using a cylindrical Langmuir probe method. The measured electron temperature was approximately 2–5 eV, while the plasma density and plasma potential were of the order of 1011–1012 cm−3 and 5–20 V, respectively, depending on the pressure and power. A retarding field analyzer with four biasable grids measured the energy distributions of sputtered Mo− beams. The transparency of the analyzer was 22.4%. The negative-ion energy is defined by the potential of sputter cathode. The process pressure was found to have a negligible effect on ion-beam energy, but did affect the ion-beam energy spread. At low pressures (approximately 4×10−4 Torr), the energy spread was 2% of the beam energy, while an average energy spread of less than 5% of beam energy was measured at 10−3 Torr. The result shows that a well-defined negative metal ion beam can be effectively produced on a large scale. © 2002 American Institute of Physics.
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07.77.Ka Charged-particle beam sources and detectors
29.25.Ni Ion sources: positive and negative
41.75.Cn Negative-ion beams
52.59.Wd Emittance-dominated beams
52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties

Reactive oxygen beam generation system using pulsed laser evaporation of highly concentrated solid ozone

Tetsuya Nishiguchi, Yoshiki Morikawa, Mitsuru Kekura, Masaharu Miyamoto, Hidehiko Nonaka, and Shingo Ichimura

Rev. Sci. Instrum. 73, 1217 (2002); http://dx.doi.org/10.1063/1.1448909 (7 pages) | Cited 13 times

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A reactive oxygen beam generation system is described for the formation of high-quality and high-precision films. This system utilizes pulsed laser evaporation of highly concentrated solidified ozone (O3). The equipment for safely generating and handling a large amount of high-purity liquid and solid O3 was also developed for this purpose. The beam is characterized by its high concentration of oxygen atoms in an excited state [O(1D)], constant flux per laser shot (4×1017 molecules cm−2 shot−1), appropriate level of kinetic energy (KE) for enhancing the surface reaction (mean KE of 0.4 eV, maximum KE of 2 eV) and small angular spread (6°). These characteristics enabled us to precisely control the SiO2 film thickness by the number of laser shots, and achieve an enhanced Si oxidation rate and new local oxidation process. © 2002 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth
81.65.Mq Oxidation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Measurement of local magnetic fields in photoelectron emission microscopy by restriction of the electron beams

S. A. Nepijko, N. N. Sedov, H. Ohldag, and E. Kisker

Rev. Sci. Instrum. 73, 1224 (2002); http://dx.doi.org/10.1063/1.1449462 (5 pages)

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The magnetic domain structure of a single crystal of Co (0001) and of polycrystalline AlNiCo was investigated in a photoelectron emission microscope making use of partial restriction of the electron beams. An external movable magnet was used for off-axis deflection of the electron trajectories in the microscope column such that parts of the trajectories are stopped by the apertures of the electron optical elements. As a result, the contrast caused by the stray fields of the magnetic domains is significantly enhanced. The distribution of the local magnetic fields at the surface is reconstructed from the image by means of a theory on the contrast mechanism. © 2002 American Institute of Physics.
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75.60.Ch Domain walls and domain structure
79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.80.Fe Electron and positron radiation effects
61.82.Bg Metals and alloys

High-efficiency spin polarimetry by very-low-energy electron scattering from Fe(100) for spin-resolved photoemission

F. U. Hillebrecht, R. M. Jungblut, L. Wiebusch, Ch. Roth, H. B. Rose, D. Knabben, C. Bethke, N. B. Weber, St. Manderla, U. Rosowski, and E. Kisker

Rev. Sci. Instrum. 73, 1229 (2002); http://dx.doi.org/10.1063/1.1430547 (6 pages) | Cited 13 times

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We describe concept, design, and performance of a novel spin polarimeter based on spin-dependent specular reflection of electrons from a Fe(100) surface. The Fe surface is prepared as an ultrathin film on Ag(100). By tuning the energy of the electrons to a critical point in the Fe band structure, a large spin asymmetry combined with a large scattering efficiency is achieved. The polarimeter yields a figure of merit up to 10−2 for the best Fe(100) surfaces. © 2002 American Institute of Physics.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.20.Kz Other electron-impact emission phenomena

High pressure angle-dispersive Brillouin spectroscopy: A technique for determining acoustic velocities and attenuations in liquids and solids

K. J. Koski, J. Müller, H. D. Hochheimer, and J. L. Yarger

Rev. Sci. Instrum. 73, 1235 (2002); http://dx.doi.org/10.1063/1.1445869 (7 pages) | Cited 6 times

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We report the combination of a high-pressure sample chamber and a stable, nonscanning, angle-dispersive Fabry–Perot interferometer allowing the rapid measurement of inelastic light scattering from acoustic phonon modes in solid and liquid samples at high pressure. The primary components of the apparatus are a (i) narrow frequency gas ion laser, (ii) a solid or air-spaced etalon, (iii) a multichannel charge coupled device detector, and (iv) a large volume, high-pressure cell. The fundamental principle of this spectrometer is based on the angular dispersion of light through an etalon, whereupon the multiple-order frequency dispersed spectrum can be acquired with an array detector. Typical acquisition times are less than 1 s using low to moderate laser power. © 2002 American Institute of Physics.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
07.60.Ly Interferometers
62.60.+v Acoustical properties of liquids
62.65.+k Acoustical properties of solids

Electron spin resonance experiments at ultralow temperatures by means of a dilution refrigerator

T. Sakon, K. Koyama, and M. Motokawa

Rev. Sci. Instrum. 73, 1242 (2002); http://dx.doi.org/10.1063/1.1448901 (5 pages) | Cited 3 times

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An electron spin resonance (ESR) apparatus with a high sensitivity vector network analyzer has been developed for use at ultralow temperatures. The microwave frequency can be varied between 45 and 110 GHz. The resonant cavity was installed in a 3He–4He dilution refrigerator which provides ultralow temperatures down to 160 mK. In order to avoid the heating of the cavity and the sample by microwaves or heat leaks in the cryostat, attenuators and thermal anchors were placed at the most suitable positions. As the first experiment, the ESR was measured for a quantum spin chain Cu benzoate. The breather mode, which is a new ESR mode caused by a field induced gap, has been clearly observed at the lowest temperatures. © 2002 American Institute of Physics.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
76.30.-v Electron paramagnetic resonance and relaxation

High resolution low-temperature superconductivity superconducting quantum interference device microscope for imaging magnetic fields of samples at room temperatures

F. Baudenbacher, N. T. Peters, and J. P. Wikswo

Rev. Sci. Instrum. 73, 1247 (2002); http://dx.doi.org/10.1063/1.1448142 (8 pages) | Cited 19 times

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We have developed a microscope to image weak magnetic fields using submillimeter pickup coils made from conventional low-temperature superconducting niobium wire coupled to the input circuit of a superconducting quantum interference device (SQUID). The pickup coil and the SQUID sensor are mounted in the vacuum space of the cryostat and are thermally anchored to the liquid helium reservoir. A 25 μm thick sapphire window separates the room temperature (RT) sample and the vacuum space. The spacing between the pickup coil and RT sample was typically less than 130 μm. The spatial resolution is limited by the diameter of the pickup coil. The pickup coils are easily interchangeable, allowing us to adapt the SQUID microscope to a variety of different measurements. We have achieved a spatial resolution of 250 μm with a magnetic field sensitivity of 850 fT/Hz1/2 or a spatial resolution of 500 μm with a magnetic field sensitivity of 330 fT/Hz1/2. We have used this instrument to measure various biomagnetic and paleomagnetic fields. © 2002 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
07.55.Ge Magnetometers for magnetic field measurements

Use of a four detector photopolarimeter for Kerr effect measurements

T. Dumelow, M. P. da Silva, C. V. Chianca, and R. M. P. Spinelli

Rev. Sci. Instrum. 73, 1255 (2002); http://dx.doi.org/10.1063/1.1448899 (4 pages)

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A new type of Kerr effect polarimeter, making use of four detectors, is described. The light is reflected at oblique incidence off each detector in turn, in such a way that the plane of incidence changes on each reflection. Since the reflections are polarization dependent, each detector signal depends on the Kerr rotation and, since the detector outputs can be normalized, this rotation may be obtained without the need of either a particularly stable laser source nor any type of modulation. The method thus provides a cheap alternative to more traditional Kerr techniques. We demonstrate its use in obtaining hysteresis loops for a thin film sample of CoO deposited on Co. © 2002 American Institute of Physics.
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07.60.Fs Polarimeters and ellipsometers
78.20.Ls Magneto-optical effects
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
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