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排序方式: 共有166条查询结果,搜索用时 15 毫秒
1.
Laser projection-patterned etching of GaAs in a HCl and CH3Cl atmosphere performed using a pulsed KrF-excimer laser (=248 nm, =15 ns) and deep-UV projection optics (resolution 2 m) is reported. The etching process carried out in a vacuum system having a base pressure of 10–6 mbar is shown to result from a purely thermochemical reaction. Etching takes place in two steps: (i) between the laser pulses, the etchant gas reacts with the GaAs surface-atomic layer to form chlorination products (mainly As and Ga monochlorides), (ii) local laser surface heating results in the desorption of these products allowing further reaction of the gas with the surface. The influence of the etching parameters (laser energy density, gas pressure and pulse repetition rate) on the etch rate and the morphology of the etched features was studied. Etch rates up to 0.15 nm per pulse, corresponding to the removal of 0.5 GaAs molecular layer, are achieved. The spatial resolution of the etching process is shown to be controlled by the heat spread in the semiconductor and by the nonlinear dependence of the etch rate on the surface temperature. As a result, etched features smaller or larger than the projected features of the photomask are achieved depending on the laser energy density. Etched lines having a width of 1.3 m were obtained at low fluences by the projection of 2 m wide lines onto the GaAs surface. 相似文献
2.
A. Tokmakoff W. F. Banholzer M. D. Fayer 《Applied Physics A: Materials Science & Processing》1993,56(1):87-90
The photopyroelectric (PPE) technique is used to measure the specific heat of YBa2Cu3O7–X
thin films. Hysteresis in the PPE amplitude is observed in the temperature range 90 K to 250 K. Peaks in the inverse PPE amplitude at T=110 K in the cooling path and at T230 K in the heating path are observed. The magnitude of hysteresis depends upon the thermal history of the sample. 相似文献
3.
Francisco J. Salgado Sara Vázquez Amparo Pérez-Díaz Pilar Arias 《Analytica chimica acta》2010,658(1):18-3648
Serum is a typical sample for non-invasive studies in clinical research. Its proteome characterization is challenging, since requires extensive protein depletion. Methods used nowadays for removal of high-abundance proteins are expensive or show quite often a low loading capacity, which has strong repercussions on the number of samples and replicates per analysis.In order to deplete immunoglobulins (Igs) and albumin (HSA) from 1 mL serum samples, we have developed a protocol based on a combination of thiophilic chromatography, not previously used in clinical proteomics, and a HSA-specific resin. Ig/HSA-depleted samples, immunoglobulinome and albuminone were analyzed by 2-DE. Thiophilic chromatography, coupled with HSA-depletion, allows a good 2-DE resolution as well as the visualization of new spots. Moreover, it yields enough protein to evaluate technical variability and facilitate subsequent protein identification. To validate the protocol, we carried out a preliminary comparative study between triplicate Igs/HSA-depleted serum samples from healthy control individuals and recently diagnosed/untreated rheumatoid arthritis (RA) patients. RA patients showed several acute phase proteins, as well as additional serum proteins, differentially and significantly regulated.Therefore, thiophilic chromatography can be used as an efficient and economical method in 2-DE to deplete immunoglobulins from large human serum samples before a more extensive fractioning. 相似文献
4.
K. Osvay I.N. Ross J.M.D. Lister C.J. Hooker 《Applied physics. B, Lasers and optics》1999,69(1):19-23
This paper presents an experimental technique for measurement of the contrast ratio of ultrashort UV pulses. As a multiple-shot
device based on the scheme of difference frequency generation this is, to our knowledge, the only cross correlator in the
UV so far, which offers a dynamic range of 107 and operates with input pulse energies as low as 5 μJ. By changing the cross correlator into single-shot mode, the temporal
shape of the UV pulse can be measured.
Received: 26 October 1998 / Revised version: 13 January 1998 / Published online: 28 April 1999 相似文献
5.
T. Brixner 《Applied physics. B, Lasers and optics》2003,76(5):531-540
The usage of Poincaré phase space for the representation of polarization-shaped femtosecond laser pulses is discussed. In
these types of light fields the polarization state (i.e. ellipticity and orientation) changes as a function of time within
a single laser pulse. Such deliberate variation can be achieved by frequency-domain femtosecond pulse shaping in which two
polarization components are manipulated individually. Here it is shown how these light pulses can be represented as temporal
trajectories through the ellipticity-orientation (Poincaré) phase space, whereas conventional light (either continuous-wave
or pulsed) is determined by only one specific Poincaré location. General properties of parametric Poincaré trajectories are
discussed, and their relation to experimentally accessible pulse-manipulation parameters (i.e. amplitudes and phases) determined.
Specifically, it is shown how the maximum rate by which a given polarization state can be turned into a different one (at
significant intensity levels) is limited by the spectral laser bandwidth. Apart from their direct usage in polarization-shaped
pulse representation, Poincaré trajectories also form the basis for intuitive quasi-three-dimensional renderings of the electric
field profile. There, the temporal evolution of polarization, intensity, and chirp is directly apparent in a single illustration.
Received: 10 December 2002 / Published online: 24 April 2003
RID="*"
ID="*"Corresponding author. Fax: +49-931/888-4906, E-mail: brixner@physik.uni-wuerzburg.de 相似文献
6.
M.?Braun C.?Root F.?J.?Lederer T.?E.?Schrader W.?Zinth C.?von?Korff?Schmising M.?Bargheer T.?Elsaesser M.?Woerner 《Applied Physics A: Materials Science & Processing》2009,96(1):107-115
Intramolecular charge transfer in aminobenzonitrile (DIABN) single crystals is studied by a combination of ultrafast techniques.
The intramolecular dynamics is probed by time-resolved spectroscopy in the UV/Vis and mid-IR. The intermolecular structural
response is investigated by transient X-ray scattering and transmission experiments. A theoretical analysis shows that diffuse
scattering and dipole solvation determine the X-ray data. The observed dynamics results from charge transfer reaction leading
to strong local changes of molecular dipole moments and related structural rearrangements in the crystal. 相似文献
7.
S. Ota S. Shimoura H. Iwasaki M. Kurokawa S. Michimasa N. Aoi H. Baba K. Demichi Z. Elekes T. Fukuchi T. Gomi S. Kanno S. Kubono K. Kurita H. Hasegawa E. Ideguchi N. Iwasa Y.U. Matsuyama K.L. Yurkewicz T. Minemura T. Motobayashi T. Murakami M. Notani A. Odahara A. Saito H. Sakurai E. Takeshita S. Takeuchi M. Tamaki T. Teranishi Y. Yanagisawa K. Yamada M. Ishihara 《Physics letters. [Part B]》2008
8.
9.
In this paper, the mathematical expressions and the particularities of the joint fractional Fourier transform correlator (JFRTC) are detailedly analyzed. In a JFRTC, the distance between the two fractional correlation peaks can be adjusted flexibly by shifting the fractional orders. However, the intensity of the fractional correlation peaks decreases rapidly as the first fractional order p1 drops. The former property is very useful in a practical recognition system, but the latter one seriously reduces the recognition sensitivity of a JFRTC. For this reason, phase masks should be added at the input plane of the JFRTC to enhance the intensities of the fractional correlation peaks and effectively overcome the default. Compared with the existing JFRTC with single phase modulation, a JFRTC with double phase modulation is suggested to more flexibly improve the performance of a JFRTC. 相似文献
10.
Realization of MMI Power Splitter by UV-light Imprinting Technique Using Hybrid Sol-Gel SiO2 Materials 下载免费PDF全文
An efficient fabrication scheme of buried ridge waveguide devices is demonstrated by UV-light imprinting technique using organic-inorganic hybrid sol-gel Zr-doped SiO2 materials. The refractive indices of a guiding layer and a cladding layer for the buried ridge waveguide structure are 1.537 and 1.492 measured at 1550nm, respectively. The tested results show more circular mode profiles due to existence of the cladding layer. A buried ridge single-mode waveguide operating at 1550 nm has a low propagation loss (0.088 dB/cm) and the 1× 2 MMI power splitter exhibits uniform outputs, with a very iow splitting loss of 0.029 dB at 1549nm. 相似文献