摘要:

The optical properties of several thin metal film palladium-silicon oxide structures are examined at room temperature before and after annealing to 200 °C and also at 90 °C—in all cases in the presence of hydrogen gas. Multicycling sample activation is shown to occur in the presence of hydrogen at room temperature with an increase in reflectivity on exposure to hydrogen, in contrast to thicker 80 Å films. The reflectivity change increases with increasing film thickness(1–10 Å).The surface activation at room temperature, before and after annealing to 200 °C, is compared with the performance at 90 °C, where it is shown that heat treatment strongly influences the behavior of the metal film.©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149116

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We describe a novel capacitance measurement technique which is used to determine lubricant film thickness on magnetic thin-film rigid disks. Using this technique, variations in lubricant thickness as small as 0.1 nm can be measured quickly and nondestructively. Film thickness measurements made with an ellipsometer are found to be comparable to the capacitance measurements. We compare the uniformity in film thickness of disks lubricated with a dip-coating process with that of disks lubricated with a drain-coating process and find that the drain coated disks have better film uniformity than those that are dip coated. Also, wear tracks in fully bonded and partially bonded perfluoropolyether lubricants are profiled. We find that lubricant depletion occurs more rapidly in fully bonded lubricant than in partially bonded lubricant and that some recovery of the partially bonded lubricant occurs while none is observed in fully bonded lubricant. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149098

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

High-resolution commercial photomasks and x-ray masks are at present manufactured by a multistep process which involves the use of etching. This route imposes a limitation on the resolution that can be achieved. We describe here a new approach to the fabrication of x-ray masks involving the use of organometallic compounds which undergo direct conversion to metal under the influence of electron beam irradiation. This approach permits fabrication of both x-ray masks and extreme ultraviolet masks in essentially a single processing step. The attainable resolution is unaffected by any limitation incurred by etching processes and is dependent only on such factors as electron scattering and electron beam diameter. We describe here the production of a gold x-ray mask, which was used in conjunction with a compact laser plasma source to demonstrate the lithographic process. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149099

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We describe a quantitative method of measuring film thickness profiles as deposited by plasma beams. Film thickness profiles are usually closely related to the plasma density profile of the depositing beam. The technique relies on the deposition of a semiopaque film over a large area transparent mediumin situand thus is particularly suitable for plasma systems used for thin film deposition. A simple and fast technique for quantifying the optical density versus position in the deposited film using a scanner and image processing software is described. The ability to quantify the relative optical density between different deposition profiles makes this a powerful tool for the study of the effects of process parameters on plasma density profiles and for the optimization of deposition systems. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149100

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A versatile high powerX-band (8.5–9.5 GHz) pulsed EPR/ENDOR (electron-nuclear double resonance) spectrometer which can generate hundreds of microwave (MW) and rf pulses is described. The pulse programmer is constructed from a word generator with 32 channels and 4 ns resolution, coupled to five digital delay generators which can produce a total of ten pulses with a resolution better than 1 ns. The spectrometer contains two MW and two rf channels that allow independent variation of the frequency, amplitude, and phase of the MW and rf pulses. The ENDOR probe head is based on a bridged loop gap (BLG) resonator, coupling is achievedviaa coupling loop connected to a waveguide, and the rf coil serves as a MW shield as well. The adjustment of the coupling is done by an up/down motion of the of the resonator assembly with respect to the fixed coupling loop. A flexible and user friendly data acquisition program written in C++ (Borland version 4.5), which uses the Windows-95 Multiple Document Interface (MDI) programming model, was developed to run the spectrometer. This program allows easy programming of any pulse sequence with sophisticated phase cycling. The performance of the spectrometer is demonstrated by two experiments. The first is the triple resonance hyperfine-selective (HS) ENDOR experiment carried out on a frozen solution of the copper protein laccase. The second is the two-dimensional hyperfine-ENDOR (HYEND) correlation experiment performed on a single crystal of &ggr;-irradiated malonic acid. ©1998 American Institute of Physics. 

ISSN:0034-6748    

DOI:10.1063/1.1149101

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A microwave temperature-jump nuclear magnetic resonance (NMR) system suitable for aqueous solutions has been developed. A microwave pulse of a desired length is generated at a frequency of 2.46 GHz from a 1.3 kW magnetron, and is delivered through a waveguide and a coaxial cable to a coupling loop which works as an antenna to the dielectric resonator in the NMR probe. Inside the dielectric resonator, the microwave power is efficiently absorbed by the sample solution (about 100 &mgr;l) contained in a glass tube, causing a temperature jump by about 25 °C in less than 20 ms. The temperature after the jump can be maintained by applying intermittent microwave pulses of shorter length. A saddle-type radio-frequency coil is placed around the sample tube inside the hollow of the dielectric resonator to excite spins and detect NMR signals. Both the microwave pulses and the radio-frequency pulses are gated by a pulse programmer of the NMR spectrometer to form a desired temperature-jump pulse sequence. A mechanical mixing device is introduced, which significantly reduces the temperature gradient of the sample solution well within 100 ms after the jump. Application to an aqueous solution of ribonuclease A showed that the protein unfolds within 20 ms of microwave heating. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149102

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A two-thermocouple probe, composed of two fine-wire thermocouples of unequal diameters, is a novel technique for estimating thermocouple time constants without any dynamic calibration of the thermocouple response. This technique is most suitable for measuring fluctuating temperatures in turbulent combustion. In the present study, the reliability and applicability of this technique are appraised in a turbulent wake of a heated cylinder (without combustion). A fine-wire resistance thermometer (cold wire) of fast response is simultaneously used to provide a reference temperature. A quantitative and detailed comparison between the cold-wire measurement and the compensated thermocouple ones shows that a previous estimation scheme gives thermocouple time constants smaller than appropriate values, unless the noise in the thermocouple signals is negligible and/or the spatial resolution of the two-thermocouple probe is sufficiently high. The scheme has been improved so as to maximize the correlation coefficient between the two compensated-thermocouple outputs. The improved scheme offers better compensation of the thermocouple response. The present approach is generally applicable toin situparameter identification of a first-order lag system. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149103

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

To investigate catalytic activities of perovskite-type electrodes in a sealed-offCO2laser cavity, we studied the dissociation and reformation reactions ofCO2during electric discharge by monitoring the concentration change ofCO2as a function of time. A photoacoustic spectroscopy detection was introduced to measure the amount ofCO2in a closed discharge system. The catalytic activities in the dissociation ofCO2were demonstrated and compared for both Cu andLa0.7Sr0.3CoO3cathodes. The discharge with the gas mixture ofCO2:N2:He=1:1:8was performed under nine combinations of different conditions at pressures of 10, 20, and 30 Torr and discharge currents of 3, 4, and 5 mA. Within 1 min after the discharge, the concentration ofCO2reduced drastically by as much as 60&percent; for both cathodes. In the case of the Cu cathode, the amounts ofCO2in the tube had not recovered even after 30 min, while with the perovskite cathode theCO2contents recovered slowly up to 90&percent;–95&percent; within 5 min and then remained almost unchanged. The dissociation ofCO2with the Cu cathode increased as the total pressure decreased and the discharge current increased. TheLa0.7Sr0.3CoO3cathode, however, demonstrated strong suppression in the dissociation ofCO2according to the reformation reaction ofCO+(1/2)O2→CO2by its catalytic activity. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149117

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Methods for the analysis and design of solid state nuclear magnetic resonance (NMR) probes are presented. These techniques have been applied to a 200 MHz(1HLarmor frequency)1H–19F–13Ccross polarization magic angle spinning probe. Transmission lines have been used throughout the design enabling the production of a highly power efficient probe(1H-22&percent;,19F-17&percent;,and13C-33&percent;)capable of detecting19FNMR signals while applying proton decoupling fields of 250 kHz. These techniques have proven very useful in designing the probe discussed within the text but are not confined to such a triple resonant design. In fact the techniques are sufficiently general to be useful to all radio frequency design efforts including deuterium wide-line probes and multiresonant high resolution NMR probes. A series of simple but useful design concepts are presented which are used to predict the efficiencies of the design presented. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149104

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A method of measuring the phase lag of the photoacoustic signal obtained by rear surface excitation is employed for the determination of the thermal properties of insulating dental materials such as calcium hydroxide cement, a cavitary varnish and photopolymerized restoration resins. Disk shaped dental materials were glued to the front surface of the thin metal foil window of the photoacoustic cell and illuminated by pulsed light. A three layer model was developed to fit the measurements of the phase angle as a function of the frequency of excitation. The thermal diffusivity and conductivity of the dental material were determined to good precision. The instrumentation employed in the present work is simple and easily obtainable by any laboratory. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149105

出版商:AIP    

年代:1998

数据来源: AIP