共查询到20条相似文献,搜索用时 296 毫秒
1.
M.B. Pushkarsky M.E. Webber O. Baghdassarian L.R. Narasimhan C.K.N. Patel 《Applied physics. B, Lasers and optics》2002,75(2-3):391-396
An industrial trace-ammonia sensor based on photoacoustic spectroscopy and CO2 lasers has been developed for measuring ammonia with a 1σ detection limit of 220 parts-per-trillion (ppt) in an integration
time of 30 s. The instrument response time for measuring ammonia was 200 s, limited by adsorption effects due to the polar
nature of ammonia. The minimum detectable fractional absorbance was 2.0×10-7, and the minimum normalized detectable absorption coefficient for this system was 2.4×10-7 W cm-1/z. The 9R(30) transition of the CO2 laser at 9.22 μm with 2 W of output power was used to probe the strong sR(5,K) multiplet of ammonia at the same wavelength. This sensor was demonstrated with an optically multiplexed configuration
for simultaneous measurement in four cells.
Received: 3 April 2002 / Revised version: 31 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-310/458-0171, E-mail: webber@pranalytica.com 相似文献
2.
A portable modular gas sensor for measuring the 13C/12C isotopic ratio in CO2 with a precision of 0.8‰(±1σ) was developed for volcanic gas emission studies. This sensor employed a difference frequency generation (DFG)-based spectroscopic
source operating at 4.35 μm (∼2300 cm-1) in combination with a dual-chamber gas absorption cell. Direct absorption spectroscopy using this specially designed cell
permitted rapid comparisons of isotopic ratios of a gas sample and a reference standard for appropriately selected CO2 absorption lines. Special attention was given to minimizing undesirable precision degrading effects, in particular temperature
and pressure fluctuations.
Received: 16 April 2002 / Revised version: 28 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-713/5245237, E-mail: fkt@rice.edu 相似文献
3.
B. Bakowski L. Corner G. Hancock R. Kotchie R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2002,75(6-7):745-750
Cavity-enhanced absorption spectroscopy is explained in terms of the transmission function of a rapidly swept interferometer,
and the integrated transmission is shown to be proportional to the cavity ringdown time. The technique is demonstrated on
the b1Σg
+-X3Σg
- (1,0) band in molecular oxygen at 687 nm using a tunable diode laser and a relative-ly high-Q optical cavity (finesse ≈4000).
A detection limit of 3×10-8 cm-1 s1/2 is achieved for a 0.8 cm-1 scanning range.
Received: 24 June 2002 / Revised version: 5 August 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +44-1865/275410, E-mail: peverall@physchem.ox.ac.uk 相似文献
4.
Oxygen plasma and high pressure H2O vapor heat treatment were applied to fabrication of n-channel polycrystalline silicon thin film transistors (poly-Si TFTs).
13.56 MHz-oxygen-plasma treatment at 250 °C, 100 W for 5 min effectively reduced defect states of 25-nm-thick silicon films
crystallized by 30 ns-pulsed XeCl excimer laser irradiation. 1.3×106-Pa-H2O vapor heat treatment at 260 °C for 3 h was carried out in order to improve electrical properties of SiOx gate insulators and SiOx/Si interfaces. A carrier mobility of 470 cm2/V s and a low threshold voltage of 1.8 V were achieved for TFTs fabricated with crystallization at 285 mJ/cm2.
Received: 18 November 2002 / Accepted: 25 November 2002 / Published online: 11 April 2003
RID="*"
ID="*"Corresponding author. Fax: +81-42/388-7109, E-mail: tsamesim@cc.tuat.ac.jp 相似文献
5.
W.M. Shu Y. Kawakubo M.F. Nishi 《Applied Physics A: Materials Science & Processing》2003,76(3):421-425
Recovery of tritium from co-deposited layers formed in deuterium–tritium plasma operations of the TFTR (Tokamak Fusion Test
Reactor) was investigated by the use of an ArF excimer laser operating at the wavelength of 193 nm. At the laser energy density
of 0.1 J/cm2, a transient spike of the tritium-release rate was observed at initial irradiation. Hydrogen isotopes were released in the
form of hydrogen-isotope molecules during the laser irradiation in vacuum, suggesting that tritium can be recovered readily
from the released gases. In a second experiment, hydrogen (tritium) recovery from the co-deposited layers on JT-60 tiles that
had experienced hydrogen-plasma operations was investigated by laser ablation with a focused beam of the excimer laser. The
removal rate of the co-deposited layers was quite low when the laser energy density was smaller than the ablation threshold
(1.0 J/cm2), but reached 1.1 μm/pulse at the laser energy density of 7.6 J/cm2. The effective absorption coefficient in the co-deposited layers at the laser wavelength was determined to be 1.9 μm-1. The temperature of the surface during the irradiation at the laser energy density of 0.5 J/cm2 was measured on the basis of Planck’s law of radiation, and the maximum temperature during the irradiation decreased from
3570 K at the initial irradiation to 2550 K at the 1000th pulse of the irradiation.
Received: 5 August 2002 / Accepted: 7 August 2002 / Published online: 28 October 2002
RID="*"
ID="*"Corresponding author. Fax: +81-29/2825917, E-mail: shu@tpl.tokai.jaeri.go.jp 相似文献
6.
F. Sánchez M.V. García-Cuenca C. Ferrater M. Varela 《Applied Physics A: Materials Science & Processing》2002,75(3):381-385
We report on the epitaxial growth of yttria-stabilised zirconia (YSZ) buffer layers on X-cut LiNbO3 (LNO) single crystals by pulsed laser deposition. Despite the low chemical stability of the substrates at high temperature,
high quality fully reproducible films were obtained over a relatively broad range of processing conditions. The films were
(00h) out-of-plane single oriented and the in-plane edge of the YSZ unit cell was aligned with the polar axis of the LNO.
However, the YSZ deposition also promoted the formation of the compound LiNb3O8. This compound is epitaxial and located at the interface. The homogeneous YSZ film presents a uniform surface, free of outgrowths
and with a low roughness. These characteristics are suitable for the epitaxial growth of other oxides, as has been demonstrated
with the preparation of YBa2Cu3O7/CeO2/YSZ/LNO heterostructures. The superconducting YBa2Cu3O7 films were epitaxial, with the c axis perpendicular to the surface and single in-plane orientation, and presented good transport
properties (critical temperatures around 86 K and critical current densities close to 106 A/cm2 at 77 K).
Received: 5 April 2001 / Accepted: 30 July 2001 / Published online: 30 October 2001 相似文献
7.
Boron isotopic enrichment is observed in the laser ablation of B4C target using nanosecond (ns) wide 532 nm laser beam of a Nd-YAG laser. B10/B11 ratio of 0.9 against the natural abundance of 0.25 is obtained at a laser power density of 8×108 W/cm2 (fluence of 6.4 J/cm2). The enrichment as a function of laser power density is demonstrated using a quadrupole mass spectrometer. Apart from higher
enrichment factor, only singly charged ions are found in the laser plume from the B4C target, in contrast to the multiply charged ions from the BN target reported in a recent report using femtosecond (fs) laser
pulses. This study indicates the possibility of using less expensive, widely used ns lasers, which can also yield a higher
throughput per pulse than a fs laser for isotope enrichment.
Received: 28 September 2001 / Accepted: 4 February 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +91-4114/480-065, E-mail: mj@igcar.ernet.in 相似文献
8.
C.H. Chen A. Saiki N. Wakiya K. Shinozaki N. Mizutani 《Applied Physics A: Materials Science & Processing》2002,74(5):693-697
The structural correlations including the lattice constants and the mosaic dispersions between CeO2 and yttria-stabilized ZrO2 (YSZ) in CeO2/YSZ/Si(001) heteroepitaxial films have been investigated by out-of-plane and in-plane X-ray-diffraction techniques. The distinct
linear correlations of the full width at half-maximum (FWHM) of the ω scan between CeO2 and YSZ have been found in both directions. CeO2 always has a 0.7° lower FWHM of the ω scan than YSZ in the out-of-plane direction, but has a 2.6° higher FWHM in the in-plane
direction. A possible relationship between the out-of-plane and in-plane FWHMs of the ω scans has been demonstrated with a
lattice-rotation model. Besides, the lattice constants of CeO2 are dependent on the FWHMs of the YSZ ω scans: as the FWHM is below 3.5°, CeO2 has a tetragonal distortion, and as the FWHM is higher than 3.5°, CeO2 exhibits a cubic structure without distortion. The results are of great interest, both for the fundamental understanding
of the film-growth mechanisms and for potential applications.
Received: 11 September 2000 / Accepted: 5 June 2001 / Published online: 30 August 2001 相似文献
9.
A pulsed optical parametric oscillator (OPO) operated in an optical cavity with a grazing-incidence grating configuration
(GIOPO) was used for sensitive photoacoustic detection of trace quantities of dinitrogen oxide (N2O). The (ν1+ν3) combination vibration band of N2O was excited with the idler beam of the GIOPO at 2.86 μm using an optical cavity optimized for the idler beam. The linewidth
of the GIOPO could be reduced to 0.4 cm-1, allowing the rotational structure of the absorption spectrum to be resolved. A concentration sensitivity (signal-to-noise
ratio=3) of 60 parts in 109 by volume (60 ppb V) N2O in synthetic air was obtained. This may be sufficient for continuous monitoring of N2O in the atmosphere.
Received: 29 April 2002 / Revised version: 4 June 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +49-6221/54-4255, E-mail: peter.hess@urz.uni-heidelberg.de 相似文献
10.
D. Golberg P.S. Dorozhkin Y. Bando Z.-C. Dong C.C. Tang Y. Uemura N. Grobert M. Reyes-Reyes H. Terrones M. Terrones 《Applied Physics A: Materials Science & Processing》2003,76(4):499-507
Transport and field-emission properties of as-synthesized CNx and BNCx (x<0.1) multi-walled nanotubes were compared in detail. Individual ropes made of these nanotubes and macrofilms of those
were tested. Before measurements, the nanotubes were thoroughly characterized using high-resolution and energy-filtered electron
microscopy, electron diffraction and electron-energy-loss spectroscopy. Individual ropes composed of dozens of CNx nanotubes displayed well-defined metallic behavior and low resistivities of ∼10–100 kΩ or less at room temperature, whereas
those made of BNCx nanotubes exhibited semiconducting properties and high resistivities of ∼50–300 MΩ. Both types of ropes revealed good field-emission
properties with emitting currents per rope reaching ∼4 μA(CNx) and ∼2 μA (BNCx), albeit the latter ropes se- verely deteriorated during the field emission. Macrofilms made of randomly oriented CNx or BNCx nanotubes displayed low and similar turn-on fields of ∼2–3 V/μm. 3 mA/cm2 (BNCx) and 5.5 mA/cm2 (CNx) current densities were reached at 5.5 V/μm macroscopic fields. At a current density of 0.2–0.4 mA/cm2 both types of compound nanotubes exhibited equally good emission stability over tens of minutes; by contrast, on increasing
the current density to 0.2–0.4 A/cm2, only CNx films continued to emit steadily, while the field emission from BNCx nanotube films was prone to fast degradation within several tens of seconds, likely due to arcing and/or resistive heating.
Received: 29 October 2002 / Accepted: 1 November 2002 / Published online: 10 March 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/51-6280, E-mail: golberg.dmitri@nims.go.jp 相似文献
11.
J. Luque R.J.H. Klein-Douwel J.B. Jeffries G.P. Smith D.R. Crosley 《Applied physics. B, Lasers and optics》2002,75(6-7):779-790
Absolute number densities of the CH radical were determined in a partially premixed methane/air flame (equivalence ratio was
1.36) at atmospheric pressure by exciting a predissociating level via the CH B–X(1,0) transition using a quasi-linear laser-induced
fluorescence scheme. The peak number density was (1.0±0.4)×1013 cm-3 or 2.4±1 ppm at 1900 K, with a flame-front width of 250 μm (FWHM). Rotational energy transfer must be considered for correct
laser-induced fluorescence signal interpretation. Competition between optical pumping and rotational relaxation in both excited
and ground states produces a signal that varies almost linearly with laser pulse energy even for large pumping rates. For
these conditions, the population of the initial ground-state rotational level is depleted by optical pumping, and rotational
energy transfer collisions rapidly repopulate the level during the laser pulse. Deviations from linear behavior are less than
20%. The effects of spatial resolution and polarization of the fluorescence on the absolute measurements are also discussed.
Received: 27 March 2002 / Revised version: 22 August 2002 / Published online: 15 November 2002
RID="*"
ID="*"Present address: Lam Research Corporation, Fremont, CA 94538, USA
RID="**"
ID="**"Present address: Mechanical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
RID="***"
ID="***"Present address: Mechanical Engineering Dept., Stanford University, Stanford CA 94305, USA
RID="****"
ID="****"Corresponding author. Fax: +1-650/859-6196, E-mail: smith@mplvax.sri.com 相似文献
12.
The ohmic contact characteristics of Au/Pt/Ti on degenerated doped n-GaAs were evaluated. Structural and electrical properties
were studied by means of X-ray diffraction (XRD), Auger Energy Spectrum (AES) and a HP4145B parameter analyzer. The structural
analysis revealed a TiAs phase in the interface between metal multilayer and GaAs at higher annealing temperatures. Electrical
measurement showed a minimum ohmic contact resistance of 3×10-4 Ω cm2. The dominant current mechanism was found to be thermionic emission with a barrier height of Φb, of 0.09 V by comparing the experimental data with different theoretical models.
Received: 14 December 2001 / Accepted: 4 April 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +86-21/6226-4397, E-mail: zhoujian999@163.net 相似文献
13.
S.T. Sanders 《Applied physics. B, Lasers and optics》2002,75(6-7):799-802
A swept-wavelength source is created by connecting four elements in series: a femtosecond fiber laser at 1.56 μm, a non-linear
fiber, a dispersive fiber and a tunable spectral bandpass filter. The 1.56-μm pulses are converted to super-continuum (1.1–2.2 μm)
pulses by the non-linear fiber, and these broadband pulses are stretched and arranged into wavelength scans by the dispersive
fiber. The tunable bandpass filter is used to select a portion of the super-continuum as a scan-wavelength output. A variety
of scan characteristics are possible using this approach. As an example, an output with an effective linewidth of approximately
1 cm-1 is scanned from 1350–1550 nm every 20 ns. Compared to previous scanning benchmarks of approximately 1 nm/μs, such broad,
rapid scans offer new capabilities: a gas sensing application is demonstrated by monitoring absorption bands of H2O, CO2, C2H2 and C2H6O at a pressure of 10 bar.
Received: 5 August 2002 / Revised version: 23 September 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +1-608/265-2316, E-mail: ssanders@engr.wisc.edu 相似文献
14.
Field emission from single-walled carbon nanotubes (SWNTs) aligned on a patterned gold surface is reported. The SWNT emitters
were prepared at room temperature by a self-assembly monolayer technique. SWNTs were cut into sub-micron lengths by sonication
in an acidic solution. Cut SWNTs were attached to the gold surface by the reaction between the thiol groups and the gold surface.
The field-emission measurements showed that the turn-on field was 4.8 V/μm at an emission current density of 10 μA/cm2. The current density was 0.5 mA/cm2 at 6.6 V/μm. This approach provides a novel route for fabricating CNT-based field-emission displays.
Received: 3 May 2002 / Accepted: 6 May 2002 / Published online: 4 December 2002
RID="*"
ID="*"Corresponding author. Fax: +82-54/279-8298, E-mail: ce20047@postech.ac.kr 相似文献
15.
Spectroscopic sensing of gases can be performed with high sensitivity and photometric precision by cavity ringdown (CRD) absorption
spectroscopy. Our cavity ringdown spectrometer incorporates continuous-wave (cw) tunable diode lasers, fibre-optic coupling
and standard photonics and optical telecommunications components. It comprises a rapidly swept optical cavity in a single-ended
optical heterodyne transmitter–receiver configuration, enabling optical absorption of gases to be recorded either as single-frequency
scanned spectra or as simultaneous, multi-wavelength tailored spectra. By measuring weak near-infrared rovibrational spectra
of carbon dioxide gas (CO2), with high resolution in the vicinity of 1.53 μm, we have realised a noise-limited absorption sensitivity of 2.5×10-9 cm-1 Hz-1/2. Analytical sensitivity limits (both actual and projected) and prospective gas-diagnostic applications are discussed. Our
approach to cw-CRD spectroscopy offers high performance in a relatively simple, low-cost, compact instrument that is amenable
to chemical analysis of trace gases in medical, agricultural, industrial and environmental situations.
Received: 16 May 2002 / Revised version: 3 June 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +61-2/9850-8313, E-mail: brian.orr@mq.edu.au 相似文献
16.
Sensitive absorption measurements in the near-infrared region using off-axis integrated-cavity-output spectroscopy 总被引:3,自引:0,他引:3
A novel instrument that employs a high-finesse optical cavity as an absorption cell has been developed for sensitive measurements
of gas mixing ratios using near-infrared diode lasers and absorption-spectroscopy techniques. The instrument employs an off-axis
trajectory of the laser beam through the cell to yield an effective optical path length of several kilometers without significant
unwanted effects due to cavity resonances. As a result, a minimum detectable absorption of approximately 1.4×10-5 over an effective optical path of 4.2 km was obtained in a 1.1-Hz detection bandwidth to yield a detection sensitivity of
approximately 3.1×10-11 cm-1 Hz-1/2. The instrument has been used for sensitive measurements of CO, CH4, C2H2 and NH3.
Received: 6 May 2002 / Revised version: 31 May 2002 / Published online: 2 September 2002
RID="*"
ID="*"Corresponding author. Fax: +1-650/965-7074, E-mail: d.baer@lgrinc.com 相似文献
17.
E.C. Richard K.K. Kelly R.H. Winkler R. Wilson T.L. Thompson R.J. McLaughlin A.L. Schmeltekopf A.F. Tuck 《Applied physics. B, Lasers and optics》2002,75(2-3):183-194
We describe a near-infrared in situ tunable diode laser spectrometer developed for atmospheric measurements of CH4 in the upper troposphere and lower stratosphere (UT/LS). The instrument is designed to provide fast-response (0.5–1 Hz) measurements
and operate autonomously on the NASA WB-57F high-altitude aircraft. A single-mode InGaAsP distributed feedback laser diode
operating at 1.6537 μm scans continuously over the R(3) rotation–vibration transition in the 2ν3 band. We use a direct absorption technique incorporating a custom-designed long path length (252 m) low-volume (3.6 L) astigmatic
Herriott cell. The present detection sensitivity is 5×1010 molecules cm-3, corresponding to ∼20 ppbv in the UT/LS, with the main limit to instrument precision being background optical interference
fringes. In-flight performance is demonstrated by presentation of recent data.
Received: 25 January 2002 / Revised version: 5 April 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-303/497-5373, E-mail: richard@al.noaa.gov 相似文献
18.
F. Kühnemann M. Wolfertz S. Arnold M. Lagemann A. Popp G. Schüler A. Jux W. Boland 《Applied physics. B, Lasers and optics》2002,75(2-3):397-403
A photoacoustic spectrometer for the simultaneous detection of isoprene and the deuterated species [4,4-2H]-2-methyl-1,3-butadiene (isoprene-d2) is presented. Using a sealed-off 13CO2 laser a single-component detection limit of 400 ppt (isoprene) and 600 ppt (isoprene-d2) was achieved. Simultaneous monitoring of both compounds allowed the detection of labelling levels down to 6% (isoprene-d2 in total isoprene) with a time resolution of 3 min.
In emission studies with Eucalyptus globulus, the deuterated precursor [4,4-2H]-1-deoxy-D-xylulose was fed to a leaf through the transpiration stream. Emission of isoprene-d2 started as early as 10 min after application of the precursor.
Received: 3 May 2002 / Revised version: 31 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +49-228/733474, E-mail: frank.kuehnemann@iap.uni-bonn.de 相似文献
19.
J. Wang Z. Li W. Cai Z. Miao P. Chen X. Chen W. Lu 《Applied Physics A: Materials Science & Processing》2003,76(6):975-978
Raman spectroscopy was used to study the evolution of host lattice recrystallization in Mn+-implanted GaAs. A high dose of Mn+-ions (>1015 cm-2) was introduced into semi-insulating GaAs by the combinatorial implantation method. Subsequent thermal annealing at 920 °C
was carried out to re-grow the implantation-induced amorphous layers. The dependence of the recrystallization behavior on
the Mn content was systematically observed. The lattice orientation of recrystallized layers in the surface changed after
high-dose implantation (>1.6×1015 cm-2) and annealing. The size of the recrystallized crystallites decreased with increasing Mn+ dose, as indicated by images from atomic force microscopy. The decrease in the phonon frequency of the Raman lines with the
size reduction of microcrystals was in good agreement with the spatial correlation model. However, at higher doses (>7×1016 cm-2), a blue shift of the frequency was observed due to the compressive stress exerted on the microcrystals.
Received: 5 March 2002 / Accepted: 29 August 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +86-21/658-30734, E-mail: jqwang@mail.sitp.ac.cn 相似文献
20.
M. Luennemann U. Hartwig G. Panotopoulos K. Buse 《Applied physics. B, Lasers and optics》2003,76(4):403-406
The electrooptic effect in lithium niobate crystals (LiNbO3) for extremely high externally applied electric fields of up to 65 kV/mm is investigated. Homogeneous electrooptic refractive-index
changes of up to 4.8×10-3 are found for ordinarily polarized light. No quadratic electrooptic effect is observed. An upper bound for the quadratic
electrooptic coefficient of |s13|≤2.3×10-21 m2/V2 is determined. Electrooptic, angular, and wavelength tuning of the Bragg condition of a thermally fixed hologram are demonstrated.
Received: 29 October 2002 / Revised version: 14 January 2003 / Published online: 26 March 2003
RID="*"
ID="*"Corresponding author. E-mail: ml@uni-bonn.de 相似文献