bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of residual stress in Cr-implanted Al2O3 by glancing angle x-ray diffraction
Authors: Specht E. D. , Sparks C. J. , McHargue C. J.
Published: July 2002

We report x-ray diffraction measurements of residual stress in sapphire crystals implanted with Cr+ ions. Stress is determined by measuring both in-plane and out-of-plane lattice constants. Bragg peak positions are measured to determine average stress, while peak widths are measured to determine its variation. Using angles of incidence close to the critical angle for total external reflection of x rays, we compare measurements confined to within ∼2.5 nm of the surface and measurements over the ∼80 nm thickness of the implanted region. These x-ray residual stress determinations are consistent with those based on indentation crack length, but were less by a factor of 10 than reports based on cantilever bending.
Investigations on InP:Ti grown by metalorganic vapor phase epitaxy
Authors: Ottenwälder D. , Scholz F. , Kessler M. , Rückert G. , Pressel K. , Barth F. , Kürner W. , Dörnen A. , Thonke K. , Gao Y.
Published: July 2002

Ti doped InP layers were grown by atmospheric pressure metalorganic vapor phase epitaxy. Using the commercially available tetrakis(diethylamino)-titanium, we obtained total Ti doping levels up to 1020 cm−3. Photocurrent measurements and deep level transient spectroscopy enabled us to investigate the internal 3d-transitions of Ti3+ (2E→2T2: 546.5 and 550 meV) and the Ti3+/Ti4+ transition (0.62 eV) confirming substitutional incorporation of Ti in InP. The concentration of electrically active Ti is limited to a value of 2.5×1017 cm−3, as determined by InP:Ti:Zn co-doping experiments. Secondary ion mass spectroscopy demonstrated, that oxygen incorporation is one reason for incomplete electrical activity, especially in the lower Ti doping region.
Dishing effects in a chemical mechanical polishing planarization process for advanced trench isolation
Authors: Yu C. , Fazan P. C. , Mathews V. K. , Doan T. T.
Published: July 2002

We report the first detailed study of dishing effects in chemical mechanical polishing (CMP) of oxide films, observed during the development of an advanced CMP-only trench isolation process. The degree of dishing has been determined for field widths ranging from 0.3 μm to 4 mm and was found to be highly pattern geometry (field width) sensitive, increasing from ∼0 nm at a field width of 5 μm and below to 200 nm at 4 mm. Although this dishing effect makes complete planarization in a large field oxide region (on the order of 1 mm) difficult, it poses no serious problem for trench isolation in narrow field regions due to its reduced effect at small field geometries.
Property modification of ferroelectric Pb(Zr,Ti)O3 thin films by low-energy oxygen ion bombardment during film growth
Authors: Hu H. , Krupanidhi S. B.
Published: July 2002

Low-energy oxygen ion bombardment is being used to enhance the electrical properties of multi-ion beam sputter deposited ferroelectric Pb(Zr,Ti)O3 thin films. The degree of (100) orientation, remnant polarization (Pr), coercive field (Ec), and dielectric constant (k) of the films were chosen to properly quantify the bombardment effect. It was found that these properties are strongly dependent on the ion beam flux and bombarding ion energy. The ion/atom ratios between 1.0 and 1.3 and the bombarding energies within the range of 60–80 eV are optimal to realize desirable property modification. Relative to the nonbombarding case, the bombardment could increase the Pr and k by up to 60% and 25%, respectively, and reduce the Ec by about 20%.
Intrinsic stress of Ag and Au electrical contact films for high temperature superconductor thin films
Authors: Winau D. , Koch R. , Weber M. , Rieder K.-H. , Garg R. K. , Schurig T. , Koch H.
Published: July 2002

Thin films of the noble metals Ag and Au are prospective candidates for application as electrical contacts in high temperature superconductor (HTSC) thin film devices. We present first results on intrinsic stress in Ag and Au films measured during and after their UHV deposition onto YBa2Cu3O7−x thin film substrates. At 110 K film growth proceeds by columnar grain growth with tensile stresses as huge as the tensile strength of the bulk phase. At room temperature and up to 600 K the films grow via island growth developing much smaller film stress. At temperatures above 550 K a compressive stress contribution due to interdiffusion of oxygen from the HTSC substrates into the contact films is observed.
Calibration of height in atomic force microscope images with subnanometer scale silicon dioxide steps
Authors: Ohmi T. , Aoyama S.
Published: July 2002

Patterned SiO2 surfaces formed on silicon wafer were observed by the atomic force microscope (AFM). The samples which have fine steps were prepared by wet etching with newly developed buffered hydrogen fluoride (BHF) which has an extremely low etching rate of around 1 Å/min level. The height data in the AFM images were successfully calibrated with etching depth measured by the ellipsometry. We recommend this method to calibrate the z-axis in the scanning probe microscope images at sub-nanometer scale.
Tunable blue light source by intracavity frequency doubling of a Cr-doped LiSrAlF6 laser
Authors: Balembois François , Georges Patrick , Salin François , Roger Gérard , Brun Alain
Published: July 2002

A Cr3+:LiSrAlF6 laser in Q-switched operation at 10 kHz was intracavity frequency doubled by using a LiIO3 crystal. The 230 ns tunable blue pulses were obtained in the 395–435 nm range with up to 7 mW average power at 407 nm.
New method for determining the nonlinear optical coefficients of thin films
Authors: Hase Y. , Kumata K. , Kano S. S. , Ohashi M. , Kondo T. , Ito R. , Shiraki Y.
Published: July 2002

A new scheme for characterizing the quadratic optical nonlinearity of thin films grown on opaque substrates is proposed and demonstrated. This involved the measurement, as a function of the film thickness, of second-harmonic waves reflected from a film surface. The d36 coefficient of a ZnSe-on-GaAs film is estimated by this method to be 33±7 pm/V at the fundamental wavelength of 1.06 μm, which agrees reasonably well with the known value for the bulk crystal.
Picosecond optical parametric generation and amplification in LiB3O5 and β-BaB2O4
Authors: Huang Fang , Huang Liu
Published: July 2002

In this letter, an optical parametric generation and amplification system including a type II noncritically phase-matched LiB3O5 and a type I critically phase-matched β-BaB2O4 is reported. Pumped by 4.8 mJ 30 ps 355 nm laser pulse, 415.9–482.6 nm tunable wavelengths with linewidths as low as 0.15 nm have been obtained. System pump-to-signal energy conversion efficiency up to 32.7% with 1.57 mJ energy and 52 MW peak-power single pulse have been achieved.
Synthesis and characterization of epitaxial YBa2Cu3O7−δ/KNbO3 thin-film heterostructures
Authors: Soble C. N. , Rou S. H. , Lichtenwalner D. J. , Graettinger T. M. , Woolcott R. R. , Auciello O. , Kingon A. I.
Published: July 2002

YBa2Cu3O7−δ/KNbO3 thin-film bilayers have been deposited on (100) MgO using an in situ ion-beam sputter-deposition technique. X-ray diffraction and transmission electron microscopy indicate that both films grow epitaxially. The KNbO3 grows with the [00l] direction perpendicular to the MgO substrate surface, and the YBa2Cu3O7−δ (YBCO) grows c-axis oriented (00l) on the (00l) KNbO3 film. The YBCO films have transition temperatures as high as 85 K. Rutherford backscattering spectrometry indicates that there is no noticeable potassium diffusion into the YBCO film or MgO substrate. Transmission electron microscopy has been used to study the microstructural details of the interface. Despite the epitaxy of YBCO on KNbO3, a thin reaction layer exists at the interface. The reacted layer may possibly be eliminated by optimizing deposition parameters.
Self-enhanced diffraction from fixed photorefractive gratings during coherent reconstruction
Authors: Segev Mordechai , Kewitsch Anthony , Yariv Amnon , Rakuljic George A.
Published: July 2002

We explore, theoretically and experimentally, the effects of self-enhancement (or self-depletion) of the diffraction which occurs during coherent reconstruction from fixed photorefractive gratings. These effects are caused by interference between a secondary grating, which forms between the readout and the reconstructed beams, and the fixed grating.
Growth and saturation of stimulated beam modulation in a two-stream relativistic klystron amplifier
Authors: Chen C. , Catravas P. , Bekefi G.
Published: July 2002

A two-stream relativistic klystron amplifier (RKA) is proposed in which the amplification of stimulated beam modulation is achieved via the unstable two-stream interaction rather than the use of passive cavities. After a calculation of the limiting current, the amplification and saturation of the stimulated beam modulation are analyzed using a cold-fluid model and particle-in-cell simulation. Good agreement is found between theory and simulation in the linear regime. Fully modulated intense relativistic electron beams are obtained at saturation. In the proposed scheme, substantial beam energy difference is required to achieve large instability growth.
Real-time, in situ monitoring of surface reactions during plasma passivation of GaAs
Authors: Aydil Eray S. , Zhou Zhen , Giapis Konstantinos P. , Chabal Yves , Gregus Jeffrey A. , Gottscho Richard A.
Published: July 2002

Real-time, in situ observations of surface chemistry during the remote plasma passivation of GaAs is reported herein. Using attenuated total reflection Fourier transform infrared spectroscopy, the relative concentrations of -As-O, -As-H, -H2O, and -CH2 bonds are measured as a function of exposure to the effluent from a microwave discharge through NH3, ND3, H2, and D2. The photoluminescence intensity (PL) from the GaAs substrate is monitored simultaneously and used qualitatively to estimate the extent of surface state reduction. It was found that, while the -CHx(x = 2,3) and -As-O concentrations are reduced rapidly, the rates at which the -As-H concentration and the PL intensity increase are relatively slow. The concentration of -H2O on the GaAs surface increases throughout the process as surface arsenic oxides and the silica reactor walls are reduced by atomic hydrogen. These observations suggest that removal of elemental As by reaction with H at the GaAs–oxide interface limits the passivation rate.
All-solid-state subpicosecond passively mode locked erbium-doped fiber laser
Authors: Loh W. H. , Atkinson D. , Morkel P. R. , Hopkinson M. , Rivers A. , Seeds A. J. , Payne D. N.
Published: July 2002

Using a semiconductor saturable absorber, an erbium-doped fiber laser has been passively mode locked to yield pulses of 840 fs with pulse energies of 0.85 nJ. Stable mode locking at the fundamental roundtrip frequency and also at the second and third harmonic has been achieved.
Electron cyclotron resonance plasma process for InP passivation
Authors: Hu Y. Z. , Li M. , Wang Y. , Irene E. A. , Rowe M. , Casey H. C.
Published: July 2002

In situ ellipsometry has been used to monitor electron cyclotron resonance (ECR) plasma oxidation of InP at room temperature in the shadow plasma between a shutter and the sample. This process leaves no detectable excess P at the InP-oxide interface. A capping layer of SiO2 was grown by ECR chemical-vapor deposition at a substrate temperature of 150 °C. The samples were rapid-thermal annealed at 500 °C for 1 min in an oxygen ambient. The dielectric layers were evaluated by current-voltage and capacitance-voltage measurements on metal-oxide n-type InP capacitors.
Light detection sensitivity of a vertical cavity structure used in an optical switch device
Authors: Yamanaka Yutaka , Numai Takahiro , Kasahara Kenichi , Kuboto Keiichi
Published: July 2002

The light detection characteristics in a vertical cavity surface-emitting laser-type vertical-to-surface transmission electrophotonic device (VC-VSTEP) have been evaluated. To realize a low energy optical interconnection, not only the switching threshold energy but also the light detection sensitivity must be optimized. Maximum sensitivity is achieved when the input light wavelength and the field distribution coincide with fundamental cavity mode characteristics. Under the best matching condition, the input light energy necessary to switch the VC-VSTEP state is easily lower than 1 pJ.
Josephson tunnel junction microwave attenuator
Authors: Koshelets V. P. , Shitov S. V. , Shchukin A. V. , Baryshev A. M. , Filippenko L. V. , Fischer G. M. , Mygind J.
Published: July 2002

A new element for superconducting electronic circuitry—a variable attenuator—has been proposed, designed, and successfully tested. The principle of operation is based on the change in the microwave impedance of a superconductor-insulator-superconductor (SIS) Josephson tunnel junction when dc biased at different points in the current-voltage characteristic. Both numerical calculations based on the Tien–Gordon theory and 70-GHz microwave experiments have confirmed the wide dynamic range (more than 15-dB attenuation for one stage) and the low insertion loss in the ‘‘open’’ state. The performance of a fully integrated submillimeter receiver circuit which comprises a flux–flow oscillator (FFO) as local oscillator, a superconducting variable attenuator, and a microwave SIS detector with tuned-out capacitance is also reported.
Enhancement of the Er3+ emissions from AlGaAs:Er codoped with oxygen
Authors: Colon J. E. , Elsaesser D. W. , Yeo Y. K. , Hengehold R. L. , Pomrenke G. S.
Published: July 2002

Codoping AlxGa1−xAs with both erbium and oxygen drastically enhanced the intensity of the Er3+-4f emissions over that observed from AlxGa1−xAs doped with Er alone, however, similar codoping in GaAs did not result in any enhancement. It is believed that the enhancement of the intra-4f emissions is either due to the formation of Er-Al-O complexes or Er-O complexes along with the variation of the band gap in AlxGa1−xAs, or both.
Thermally stimulated current in fast neutron irradiated semi-insulating GaAs: Ga antisite related new trap
Authors: Kuriyama K. , Tomizawa K. , Koga K. , Hayashi N. , Watanabe H. , Ikeda Y. , Maekawa H.
Published: July 2002

The evaluation of the defects in fast neutron irradiated semi-insulating GaAs was studied using thermally stimulated current (TSC) and photoluminescence (PL) methods. A new TSC peak is observed at an annealing stage between 550 and 600 °C. This peak is associated with a GaAs-X complex defect, which might include X as the gallium vacancy, according to both the analysis of the activation energy and the annealing behavior of the PL emission. A prominent TSC peak is also observed in as-irradiated samples, showing the creation of an AsGa- VAs complex.
Photoamperic probes in scanning tunneling microscopy
Authors: Prins M. W. J. , van der Wielen M. C. M. M. , Jansen R. , Abraham D. L. , van Kempen H.
Published: July 2002

The charge generated at the apex of a semiconductor tip upon laser irradiation is utilized in a scanning tunneling microscope. We show such arrangements can produce photoinduced tunnel currents of several hundred picoamperes, sufficient for stable STM operation and sensitive enough to detect nanowatt variations in the incident optical power.
Uniform and large-area deposition of diamond by cyclic thermal plasma chemical vapor deposition
Authors: Eguchi Keisuke , Yata Shigeo , Yoshida Toyonobu
Published: July 2002

Cyclic thermal plasma chemical vapor deposition is used to deposit diamond films on the substrates placed on a rotating stage with the plasma torch mounted off axis from the center of rotation. The Ar-H2-CH4 plasma jet was generated by a 50 kW level hybrid plasma torch under 250 Torr, and the jet could be extended as long as 300 mm from the torch exit. Pure diamond films were successfully deposited on relatively large-area substrates. The thickness variations within a 10 cm2 area were less than 3% in the direction of rotation, and around 70% in the perpendicular direction. Deposition rates were about 1 nm layers per pass. These corresponded to a conversion efficiency of about 2% (1 carat/h) from CH4 to diamond.
Preparation of cubic boron nitride films by low pressure inductively coupled plasma enhanced chemical vapor deposition
Authors: Ichiki Takanori , Yoshida Toyonobu
Published: July 2002

Cubic boron nitride (c-BN) films have been prepared by low pressure inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD). 13.56 MHz ICP was generated inside a 38 mm diam tube by supplying 7 kW rf power at 1×10−3 Torr. Films were deposited on Si(100) substrates from the B2H6+N2+He+Ar system at 900 °C. Polycrystalline c-BN films with the grain size less than 50 nm were deposited with the proper ion bombardment of the growing surface. The presence of cubic phase of boron nitride has been confirmed by both infrared absorption spectroscopy and electron diffraction patterns. The optimum sheath potential for c-BN growth in this work was revealed to be 80–86 V.
Thermal instability, magnetic field shielding and trapping in single-grain YBa2Cu3O7−δ bulk materials
Authors: Gao L. , Xue Y. Y. , Meng R. L. , Chu C. W.
Published: July 2002

We report results on the temperature dependence of the trap field BT and the thermal instability (flux jump) field Hfj in single-grain YBa2Cu3O7−δ disks. Above 45 K, BT is limited by the critical current density Jc and BT=BT0(1−T/Tc)q with q≊1.67. At 4.2 K, the first flux jump field Hfj of ∼3 T is about an order of magnitude larger than theoretical prediction based on the adiabatic thermal instability model. We also find that the occurrence of large flux avalanches probably causes severe microcracking damages to the superconducting disks.
New observation on thin discontinuous metal films
Authors: Hedborg Eva , Winquist Fredrik , Lundström Ingemar
Published: July 2002

It is shown from the capacitance-voltage curves of metal-insulator-semiconductor structures that molecular species in an electrolyte interact with thin discontinuous, hydrophobic platinum films in a way similar to that in a gas phase. It is suggested that this is due to the presence of air volumes in the cracks of the discontinuous metal. This suggestion is supported by theoretical models for the wetting of thin films. The observation may have implications for the use of thin metal layers as the sensing material in chemical sensors for molecular species in solutions.
Extraction of the coefficient of giant magnetoresistance
Authors: Idzerda Y. U. , Chen C.-T. , Cheng S.-F. , Vavra W. , Prinz G. A. , Meigs G. , Lin H.-J. , Ho G. H.
Published: July 2002

Element specific magnetic hysteresis (ESMH) loops have been used in conjunction with measured magnetoresistance curves to extract the coefficient of giant magnetoresistance (GMR), which is the maximum achievable value of the GMR independent of magnetic domain effects and incomplete moment alignment effects, for sputtered Fe/Cu/Co sandwiches on silicon substrates. Using the ESMH loops to calculate GMR curves, comparison with the measured GMR curves shows that the magnetization reversal process is best described by multidomain Ising behavior.
Nature of strained InAs three-dimensional island formation and distribution on GaAs(100)
Authors: Madhukar A. , Xie Q. , Chen P. , Konkar A.
Published: July 2002

The substrate temperature and arsenic pressure dependence of the density of InAs three-dimensional (3D) islands formed on GaAs(100) is found to exhibit a behavior that cannot be reconciled within the currently popular view of MBE growth. Rather, either an arsenic coverage induced strain enhanced In migration or strain dependent arsenic incorporation at islands, or both, appear to be operative. Plan-view and cross-sectional transmission electron microscopy, including the nature of the Moiré fringes, are used to obtain cluster size distribution and demarcation between size regime for coherent versus incoherent islands. The results point to the possibility of realizing a regular array of quantum dots made of coherently strained 3D islands of uniform size via growth on prepatterned substrates.
Nanosecond imaging study on laser ablation of liquid benzene
Authors: Tsuboi Yasuyuki , Fukumura Hiroshi , Masuhara Hiroshi
Published: July 2002

KrF excimer laser ablation of liquid benzene was studied by a nanosecond imaging technique. The ejection of a plume followed by remarkable transient morphological changes took place, which was directly observed over a wide range of the fluence. From imaging data, an ablation threshold was determined to be 100 mJ/cm2 and ablation behavior induced by electronic excitation of liquid molecules is considered. A delay time prior to the plume ejection is about 40±20 ns, while the remarkable morphological change ranges from sub-μs to ms time regime.
Optically stabilized diode laser using high-contrast saturated absorption
Authors: Cuneo C. J. , Maki Jeffery J. , McIntyre D. H.
Published: July 2002

Doppler-free saturation spectroscopy in an optically thick atomic vapor is used in an optical-feedback stabilization system for a semiconductor diode laser. A portion of the 780 nm diode laser beam passes through a heated rubidium cell and is reflected back to the laser. The optical feedback causes the laser frequency to be stabilized to a hyperfine transition within the Rb D2 line. The linewidth of the laser is reduced by more than two orders of magnitude.
Novel ablation of fused quartz by preirradiation of vacuum-ultraviolet laser beams followed by fourth harmonics irradiation of Nd:YAG laser
Authors: Sugioka K. , Wada S. , Tashiro H. , Toyoda K. , Nakamura A.
Published: July 2002

Preirradiation using vacuum-ultraviolet (VUV) beams of anti-Stokes stimulated Raman scattering VUV laser, followed by the fundamental beam (266 nm) irradiation, provides a novel scheme for fused quartz ablation. The preirradiation of 5th- (171 nm) or 6th- (160 nm) order anti-Stokes beams realizes significant ablation with the succeeding fundamental beam irradiation of a laser fluence less than the ablation threshold. X-ray photoelectron spectroscopy analysis reveals that SiOx(x < 2) is created in the fused quartz by photolysis using the anti-Stokes beams. Each effect of the preirradiation and the succeeding fundamental beam irradiation in the ablation process is discussed.
Josephson properties of basal-plane-faced tilt boundaries in YBa2Cu3O7−δ thin films
Authors: Moeckly B. H. , Buhrman R. A.
Published: July 2002

The Josephson properties of 90° basal-plane-faced tilt boundaries formed between c-axis and a-axis normal grains in YBa2Cu3O7−δ thin films are reported. These boundaries have a low conductance which results in underdamped junction behavior. The junction capacitance and kinetic inductance both scale directly with junction critical current and conductance. The results emphasize the inhomogeneous and filamentary nature of the superconducting properties of cuprate grain boundaries.
Strain compensated InAsP/InP/InGaP multiple quantum well for 1.5 μm wavelength
Authors: Jiang X. S. , Yu P. K. L.
Published: July 2002

We report metalorganic vapor phase epitaxy growth of InAs0.66P0.34/InP/In0.74Ga0.26P strain compensated multiple quantum wells (MQWs) at 1.5 μm wavelength. A composite InP/InGaP/InP barrier structure is used to tune the net strain of the MQWs. Compared with InAs0.66P0.34/InP strained MQWs grown under similar conditions, the InAs0.66P0.34/InP/In0.74Ga0.26P strain compensated MQWs show improvement in crystalline and optical quality.
Effect of interfaces on the electrical behavior of (Pb0.72La0.28)TiO3 thin films
Authors: Lee J. J. , Alluri P. , Dey S. K.
Published: July 2002

Paraelectric (Pb0.72La0.28)TiO3 or PLT(28) thin films were deposited on platinum coated Si substrates by the sol-gel technique. Two distinct groups of top metals, namely MT (Ni, Cr, and Ti, i.e., transition metals) and MN (Pt, Au, and Ag, i.e., noble metals) formed Ohmic and Schottky contacts, respectively. A Schottky barrier height of 1.83 eV at the Pt-PLT interface was determined. The conventional Schottky emission and Fowler–Nordheim tunneling equations were modified to account for the voltage dependence of the interfacial permittivity. It was found that Schottky emission, thermionic tunneling, and Fowler–Nordheim tunneling mechanisms were predominant in the voltage ranges of 2<V<7, 7<V<16, and V≳16, respectively.
Thermal lens coupled magneto-optical effect in a ferrofluid
Authors: Du Tengda , Yuan Suihua , Luo Weili
Published: July 2002

A magnetic-field-induced diffraction pattern was studied by a new technique: thermal lens coupled magneto-optical effect. In low fields, the diffraction angle has an almost quadratic dependence: θ∝H2. This effect can be used as an all optical magnetic field sensor with a resolution of 0.5 Oe, with a potential for further improvement. The method can also lead to the measurement of the onset of agglomeration in the sample.
Slit-scan flow cytometer for recording simultaneous waveforms
Authors: Johnston R. G. , Bartholdi M. F. , Hiebert R. D. , Parson J. D. , Cram L. S.
Published: July 2002

We have developed a slit-scan flow cytometer for recording the transient, simultaneous light scattering and fluorescence waveforms from individual metaphase chromosomes flowing through a focused laser beam. The two waveforms are recorded on a single-memory waveform recorder by delaying one of the waveforms and switching between them. The light scattering and fluorescence waveforms contain complementary information on chromosome structure. The delay and switching electronics developed here may be useful in other contexts.
Near-field magneto-optical imaging in scanning tunneling microscopy
Authors: Prins M. W. J. , Groeneveld R. H. M. , Abraham D. L. , van Kempen H. , van Kesteren H. W.
Published: July 2002

Images of magnetic bits written in a Pt/Co multilayer are presented. Using photosensitive semiconducting tips in a scanning tunneling microscope, both surface topography as well as polarization-dependent optical transmission are measured. Magnetic contrast is achieved by detection of the Faraday effect. Magneto-optical lateral resolution of 250 nm is demonstrated.
Ion beam sputtering apparatus for fabrication of compositionally modulated materials
Authors: Spaepen F. , Greer A. L. , Kelton K. F. , Bell J. L.
Published: July 2002

A new apparatus for production of artificial compositionally modulated materials is presented. It consists of an ion gun that sputters from alternating targets on a rotating assembly, the position of which is controlled by a thickness monitoring crystal. The apparatus is simple, relatively inexpensive, and flexible, in that it allows deposition of metals, semiconductors, and insulators under the same conditions.
Widely tunable, picosecond, distributed feedback dye laser
Authors: Jasny J.
Published: July 2002

A novel optical and mechanical arrangement for a tunable distributed feedback dye laser is described. The spectral bandwidth and the pulse duration of the laser emission are almost transform limited in a tunable spectral range from the near UV to the near IR.
Capillary viscometer for evaluating low-viscosity solutions at elevated temperatures
Authors: Cunningham D. B. , Doe P. H. , Joshi S. D. , Moradi-Araghi A.
Published: July 2002

A capillary viscometer designed for evaluating low-viscosity (0.2–10 cp) solutions at elevated temperatures [20–150 °C (68–302 °F)] has been built and extensively tested. This viscometer is automated, so that minimum operator effort is needed to obtain the viscosity as a function of temperature for a given solution. This viscometer is normally operated at a constant back pressure of 90 psi to avoid bubble formation. While the viscosities are routinely measured at a shear rate of about 38 s−1, viscosity measurement at other shear rates (10–250 s−1) can also be achieved by changing the set point on the flow controller.
High-pressure cell for luminescence studies of condensed phases at low temperatures
Authors: Variano B. F. , Brenner H. C. , Daniels W. B.
Published: July 2002

A clamped optical cell for high-pressure low-temperature fluorescence and phosphorescence studies is described. A particular innovation is the use of a bifurcated fiber-optic lightguide to enable sample illumination and emission collection with a single optical window. This very simple type of cell is adaptable to a variety of optical setups and is easily assembled and disassembled for sample mounting.
Pressure–volume measurements by using diamond-anvil cells and an image processing system
Authors: Tanaka Keiji , Maeda Junji
Published: July 2002

Diamond-anvil cells combined with a video image processing system provide a simple tool for measuring pressure–volume relations of small solid samples under high pressure. The feasibility of the technique is demonstrated for glassy Se and crystalline InSb. Accuracy evaluated for linear-scale measurements is approximately ±0.5%.
Enhancement of H− production in a multicusp source by cold electron injection
Authors: Leung K. N. , Ehlers K. W. , Pyle R. V.
Published: July 2002

The effect on H− production by injecting primary electrons with different energies into the three regions of a magnetically filtered multicusp source has been investigated. A substantial increase in H− yield occurs only when very low-energy electrons (E≊1 eV) are added to the plasma in the filter or extraction chamber region. The measured increases were about 50% and 25%, respectively. This increase may indicate that the H− ions are formed by dissociative attachment of vibrationally excited H2. In that case, the low-energy electron injection scheme could maintain a low average H− ion energy which in turn could improve the brightness of the extracted beam.
Gasolines as primary solvents in liquid scintillation counting
Authors: Fernández Ascensión , Ma Pinto Rosa , Sillero Antonio
Published: July 2002

Gasolines from several commercial sources have been used as primary solvents in liquid scintillation counting of dry and aqueous samples of either 3H- or 14C-labeled compounds. Dry samples can be counted only by the addition of fluors to the gasolines, and compared to a standard liquid scintillator, efficiencies of around 75% were attained. For the counting of aqueous samples, gasolines must also be supplemented with secondary solvents (i.e., 10% naphthalene, 5% Triton X-100, or 10% methanol). Simply with Triton X-100, efficiencies similar to those obtained with a dioxane-based liquid scintillator were observed in the case of some gasolines. Drawbacks to gasoline are the higher toxicity and the variation of efficiency, probably depending on the presence of color markers. On the positive side is the low price of the gasolines, compared with either toluene or dioxane, and the facility of purchasing.
Z-shaped wire profile and position monitor for collimated synchrotron radiation using a single linear motion
Authors: Kanazawa K.
Published: July 2002

A simple position and profile monitor for collimated synchrotron radiation (SR) using only one linear motion feedthrough was constructed and successfully employed to align the SR beam line of the TRISTAN accumulation ring.
Monte Carlo simulation of charged-particle-analyzer line shapes
Authors: Negri Ronald E. , Taylor James W.
Published: July 2002

A Monte Carlo simulation method is presented for calculating line shapes for charged-particle analyzers with cylindrical symmetry. Either isotropic or cosine angular distributions of charged-particle emission can be simulated. Application of this technique is demonstrated by simulation of the line shape exhibited by the Helmer planar-retarding-grid analyzer. Ray tracing is used to determine the origin of line-shape asymmetry, new entrance optics are designed, and subsequently, a simulation is used to optimize the dimensions of the analyzer apertures and beam stop to produce a symmetric nearly Gaussian line shape. This result is then verified experimentally. Although the simulation method is applied to a specific problem, it should prove to be of value for the design of any analyzer having axial symmetry.
Low-cost, high-performance quadrupole mass spectrometer based on a low-performance rf generator
Authors: Slomp Alberto , Chiasera Giuseppe , Mezzena Claudio , Pietra Francesco
Published: July 2002

We describe here a new inexpensive system performing data acquisition as well as process control of a quadrupole mass spectrometer for relatively high molecular weight compounds. The system, based on an ordinary 8-bit personal computer, performs particularly well in terms of mass scale stability, in spite of the use of a cheap, low-stability rf generator, thanks to newly designed hardware and software.
LEDs and laser diodes in schlieren optics methods
Authors: Pawliszyn Janusz
Published: July 2002

The pointing noise of light beams generated by light emitting diodes (LEDs) and laser diodes are investigated and compared with the stability of the He–Ne laser and the incandescent lamp beam. LEDs have superior pointing noise characteristics compared to other light sources with their angular position drift of only about 50 nrad.
Radio frequency voltage division between two plasma sheaths in the Gaseous Electronics Conference reference cell
Authors: Wang Yicheng
Published: July 2002

A new method is described for calculating the rf voltage division between two plasma sheaths in the capacitively coupled asymmetric Gaseous Electronics Conference reference cell, where the effective area ratio of the electrodes is unknown. The rf voltage across the ground sheath is found to decrease with increasing total electrode rf voltage, indicating that the effective area of the ground electrode increases significantly.
Are the time resolutions for the conventional and the pseudorandom methods for time-of-flight analysis different?
Authors: Verheij Laurens K. , Zeppenfeld Peter
Published: July 2002

The pseudorandom method for time-of-flight analysis has the advantage over the conventional method of a greatly improved efficiency, but, according to previous theory, the disadvantage that the time resolution is worse. Here we present an improved theory of pseudorandom modulation. We show that the resolution of this method and the conventional method are identical. This conclusion is in agreement with experimental results. The difference between the previously given and present treatment of the pseudorandom method for time-of-flight analysis is discussed. We show that the treatment given previously does not apply to a possible, real experiment, but only to the nonphysical case of an infinitely good time resolution. Second, we show that the additional broadening which was found previously for the pseudorandom method is not inherent to the method, but is due to a nonoptimal choice of the deconvolution function.
Simple, high-speed x-ray diode
Authors: Adams F. P. , Ng A. , Gazit Y.
Published: July 2002

We describe an x-ray diode which is simple to construct and operate. At a bias voltage of 2000 V, the diode response time is 430 ps (FWHM). The detector was used to obtain temporally resolved x-ray measurements on laser-produced plasmas.
Noise reduction in laser photolysis studies of photolabile samples using an optical multichannel analyzer
Authors: Lewis J. W. , Warner J. , Einterz C. M. , Kliger D. S.
Published: July 2002

An optical multichannel analyzer system for obtaining high-quality spectra of intermediates formed by nanosecond laser photolysis is described. The system is useful for samples which undergo irreversible photochemistry and which are available in limited amounts. Sample volumes as small as 25 μl are possible and a syringe pump driven by a linear stepper motor is used to deliver fresh sample after each photolysis pulse. The microchannel-plate intensified detector used here in gated mode can collect an entire spectrum in 5 ns, but proper synchronization of the detector scans is required to avoid severe distortion which can appear as random noise in signal averaging. Noise from various sources such as phosphor lag in the detector, time jitter, source intensity fluctuations, and the photon character of light are discussed. Experimental design for noise reduction is described including diagnostic procedures and light source filtering to produce more uniform signal-to-noise ratio throughout the spectrum. Finally, a comparison is made between the noise observed to occur between detector channels and the noise predicted to occur based on the photoelectron gain of the intensifier. The disagreement between these is discussed in terms of the spatial resolution of the detector.
Gated base-line restorer without ‘‘droop’’
Authors: Grubic M.
Published: July 2002

Different configurations of an analog gated base-line restorer circuit are discussed. An elimination of a ‘‘droop’’ rate is achieved by replacing the analog memory by a digital one. A design employing a digital feedback loop is described.
Low-cost clipped correlator system for use in measuring the velocity of textile fibers
Authors: Francini F. , Longobardi G.
Published: July 2002

A clipped correlator made with two cascaded commercial chips is described. The correlator works in real time, has a very low cost as compared with the commercially available models, and is designed for velocity measurement in an industrial field. An example of application in the textile industry for measurements of fibers flow is presented. An accurate system for velocity measurement has been developed, calibrated, and tested. The cross correlation formed between the signals from the two photodiodes has a peak at a lag value corresponding to the passage time of samples from the first to the second beam.
Continuous culture of bacteriophage Q-beta using a cellstat with a bubble wall-growth scraper
Authors: Husimi Yuzuru , Keweloh Hans-Christian
Published: July 2002

It has been shown that a virulent phage Qβ can be cultured continuously in a cellstat which was developed to culture a bacteriophage fd for the study of molecular evolution. A cloned disadvantageous mutant was cultured to obtain a biological relaxation curve to selection/mutation equilibrium. A new technique for scraping off the wall growth by air bubbles is introduced. The scraper worked well in short-time cultivation of Qβ. It has various advantages of a closed system.
Split analog-to-digital converter for intensity-modulated optical fiber sensors
Authors: Yakymyshyn Christopher P. , Pollock Clifford R.
Published: July 2002

A technique is described which provides a linear pulse-position modulated signal from an intrinsically analog remote optical sensor having a nonlinear response to the sensed parameter. The technique is applied to a differential absorption optical liquid level sensor. Sensor and system performance are presented.
Time-of-flight analyzer for ion end loss of a mirror plasma
Authors: Petty C. C. , Smith D. K. , Smatlak D. L.
Published: July 2002

A time-of-flight analyzer has successfully been used to measure the extracted charge-state distribution and impurity level of an ECRH mirror plasma. End-loss temperatures for each ion species have been determined from the rise time of the analyzer output pulses. Ions entering the line-of-sight device are first accelerated by a two-aperture lens and are then focused with an einzel lens. Electrostatic deflection plates chop the ion beam into short pulses which travel down a 1.20-m tube to an electron multiplier. Ion spectra are typically summed at a rate of 1 kHz using a hardware signal averager.
Study of pressure distributions in a megabar diamond indentor cell
Authors: Lorenzana Hector E. , Boppart H. , Silvera Isaac F.
Published: July 2002

We have studied pressure distributions and area of contact as a function of load in a diamond indentor cell consisting of a flat diamond plate and diamond indentors of two different radii of curvature. The measurements were conducted with type Ia, IIa, and uncharacterized diamonds. Samples investigated were either ruby or ruby on a tantalum foil. In both cases, the ruby fluorescence was used to determine the pressure distributions. Previous suggestions that the elastic Hertzian solutions are applicable for plastic samples are not supported by these data. We conclude with comments on the prospects of the system for experimental high-pressure research.
Heated cell for electron beam pumped VUV experiments
Authors: Petersen T. , Millar P. , Frey L. , Tittel F. K. , Wilson W. L. , Sauerbrey R. , Wisoff P. J.
Published: July 2002

The design of a high-temperature cell appropriate for electron beam pumping of species emitting in the vacuum ultraviolet is described. The apparatus is capable of maintaining a temperature as high as 750 °C at a cell pressure of up to 6 atm which is suitable for a variety of investigations of atomic and molecular vapors, such as alkali metals and alkali-metal, rare-gas mixtures. The performance of this apparatus with rubidium vapor in a buffer gas is described.
Ceramic probe for measuring the thermal conductivity of an electrically conductive liquid by the transient hot wire method
Authors: Nakamura Shin , Hibiya Taketoshi , Yamamoto Fumio
Published: July 2002

A new ceramic probe has been developed for measuring the thermal conductivity of an electrically conductive liquid by using the transient hot wire method. A wire was fabricated on a 10-mm-thick alumina substrate using a co-firing technique. To avoid leakage of the current to the liquid, the metallized wire was insulated with a 60-μm-thick alumina layer. Also developed for this probe is a method of compensating for the measurement error caused by increases in the resistance of metallized electrodes. The thermal conductivity of mercury was measured with this probe at temperatures of 300–382 K.
Techniques for measuring small changes in the orientation of the easy axis in permalloy films
Authors: Eijkel Kees J. , de Haan Poul , de Ridder René M.
Published: July 2002

It is well known that the orientation of the easy axis in permalloy can be affected by annealing. The need in our research for detailed information of the behavior of the easy-axis orientation in the temperature range from room temperature to 100 °C and the absence of measurement techniques to derive this information, led to the development of two new measurement techniques: (1) an adapted version of the Crowther method for measuring dispersion in easy-axis orientation combined with the optical Kerr technique and (2) a new measurement technique for determining the orientation of the easy axis combined with a galvanomagnetic method for determining magnetization direction. Both methods give detailed information on the behavior of the easy-axis orientation as a function of temperature. The resolution of both methods is 0.01° and may be increased, especially for the optical method. The optical method imposes few restrictions on film geometry and may be used, e.g., during a fabrication process. The easy-axis behavior can be observed locally. The galvanomagnetic technique requires four electrical contacts on the film. The easy-axis behavior is averaged over the total current-carrying area. This method can be used for observing the behavior of the easy axis in encapsulated devices.
Note on the precision cementing of small optical components
Authors: Hartman A. W.
Published: July 2002

When optical or mechanical components are cemented to a substrate that exhibits errors in surface figure or tilt angle, the possibility exists that these errors will propagate to the work piece. If the cement layer thickness shrinks by a given fraction p, during setting of the cement the error propagation will occur at the same fraction causing losses in flatness, tilt angle, etc. These losses can be reduced to near-harmless levels (by a fraction p2) by adopting a two-stage cementing process, involving an intermediate substrate.
Instantaneous measurement of magnetic field strength with combining beam probe and Doppler-tuned laser spectroscopy
Authors: Yamaoka Hitoshi , Kadota Kiyoshi , Yamai Hideki , Kano Satoru S. , Fujita Junji
Published: July 2002

A novel technique to measure the magnetic field strength is demonstrated, which is based on blow-off beam probing combined with Doppler-tuned laser spectroscopy. The field strength is determined from the Zeeman splitting of the LiI resonance line (670.8 nm) with good time and spatial resolutions (Δt<100 μs, Δr<5 mm). The measurable field strength is less than 1 T with an accuracy of 10%.
Six-channel, grating spectrometer for a Nd:YAG Thomson scattering experiment
Authors: Castracane J. , Drèze C. , Oleskevich T. , Waksberg A. , Neufeld R.
Published: July 2002

A receiving system for a Thomson scattering experiment is described. This system includes a multichannel grating spectrometer designed for use with a high repetition rate Nd:YAG laser. Fiber-optic coupling bundles are used at the input and output ends. High throughput is maintained with large-diameter, low f-number grating and aspheric lenses. The detectors are high-responsivity, temperature-compensated avalanche photodiodes. Results of the calibration, including anti-Stokes Raman scattering, are presented. The spectrometer is designed to operate in the Te range between 50 eV and 2 keV with a minimum electron density sensitivity of 1.6×1011 cm−3.
Time-resolved x-ray conversion efficiencies of laser-heated plasmas
Authors: Ze F. , Kauffman R. L. , Lasinski B. , Suter L. , Langer S. , Kornblum H. , Tietbohl G. , Thiessen T. , Montgomery D. , Drake R. P. , Campbell E. M.
Published: July 2002

Experiments to obtain time-resolved, soft-x-ray emission from laser-driven plasmas are succinctly described. The spectra (0.19 keV ≤ hν ≤ 1.3 keV) at various times have been deconvolved and energy integrated to obtain time-resolved yields from Au disk targets. The temporal profiles of the total thermal x-ray output power follow the overall laser temporal shape but do not show the high-frequency fluctuation observed in the laser pulse. The behavior of the ratio of the instantaneous x-ray yields over the laser absorption is studied. The studies were done at the LLNL Nova laser facility. Single pulses and pulses in ‘‘picket fence’’ configuration were used to heat the gold targets.
Current-to-voltage amplifier with a high voltage isolated input
Authors: Jaduszliwer B. , Kahla C. M.
Published: July 2002

The measurement of very low currents collected on electrodes held at high voltages is a commonly encountered experimental problem, since a commercial electrometer’s input can usually be floated only at a few tens of volts. We have run into this problem when attempting to measure the gain of the first dynode of an electron multiplier of the type used on cesium-beam atomic clocks. In order to solve it, we have designed, built, and tested a current-to-voltage (transresistance) amplifier whose input can be floated up to ±2000 V, while providing a ground-referenced low-impedance output capable of driving a voltmeter or chart recorder. This very flexible instrument can measure currents in the 10−12 –10−7-A range, has a 1-Hz bandwidth, and it can be built at a cost of a few hundred dollars.
Method for precision measurement of temperature dependence of scintillation efficiency in NaI(Tl)
Authors: Yamashita Mikio
Published: July 2002

An accurate method of measuring the temperature dependence of the scintillation efficiency in NaI(Tl) crystals is described that uses the single-electron technique. The optical intensity of scintillations is determined from the measured time spectrum that represents the temporal dependence of scintillation intensity, and hence the result is not affected by the temperature effect on the scintillation decay time. Typical experimental data obtained by the proposed method are also presented.