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121.
122.
T. Woike U. Dörfler L. Tsankov G. Weckwerth D. Wolf M. Wöhlecke T. Granzow R. Pankrath M. Imlau W. Kleemann 《Applied physics. B, Lasers and optics》2001,72(6):661-666
The purity and the concentrations of the constituents Sr, Ba, Nb and Cr were determined in single crystals of chromium-doped
Sr0.61Ba0.39Nb2O6 (SBN) by instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRF). Experiments with different
Cr concentrations CCr reveal constant Sr and Ba concentrations as well as a decreasing Nb concentration with an increasing CCr. Therefore, Cr is incorporated at Nb lattice sites. The distribution coefficient of Cr is 1.2 between 100 and about 7000 ppm
Cr and 1 above. From measurements of the holographic two-beam coupling gain Γ for different CCr, we deduced response times for the buildup of holographic gratings. The saturation value of Γ depends in a nonlinear manner
on CCr and reaches its maximum at about 6000 ppm Cr. The inverse photorefractive response time of the grating erasure depends linearly
on the erasure intensity for all doping concentrations. Thus a one-center model can be assumed for the charge transport in
SBN:Cr.
Received: 8 December 2000 / Revised version: 23 January 2001 / Published online: 21 March 2001 相似文献
123.
J.-P. Meyn C. Laue R. Knappe R. Wallenstein M.M. Fejer 《Applied physics. B, Lasers and optics》2001,73(2):111-114
Fabrication of periodically poled lithium tantalate (PPLT) with periods as short as 1.3 μm for second harmonic generation
(SHG) in the UV range and for optical parametric oscillators pumped at 532 nm is reported. Both the maximum crystal size of
up to 40 mm and the minimum poling period of 1.3 μm are improvements on earlier results, achieved by optimizing the poling
conditions and by using a novel electrode design consisting of electrode structures on both surfaces of the crystal. Single-pass
SHG of a master oscillator power amplifier (MOPA) diode laser with an output power of 1.36 mW at 336 nm using a 16-mm-long
PPLT crystal with a 1.5 μm poling period is reported.
Received: 11 June 2001 / Published online: 18 July 2001 相似文献
124.
Enhanced fatigue property of PZT thin films using LaNiO3 thin layer as bottom electrode 总被引:2,自引:0,他引:2
X.J. Meng J.L. Sun J. Yu G.S. Wang S.L. Guo J.H. Chu 《Applied Physics A: Materials Science & Processing》2001,73(3):323-325
A highly (100)-oriented metallic LaNiO3 film was prepared directly on a Si substrate by a simple metalorganic decomposition (MOD) technique using lanthanum nitrate
and nickel acetate as the starting sources. Subsequent Pb(Zr,Ti)O3 (PZT) thin films deposited on the LaNiO3-coated Si substrate were obtained by a modified sol–gel method. It was found that the PZT thin films began to form a single
perovskite phase at a low annealing temperature of 530 °C, and exhibited highly (100) orientation. A ferroelectric capacitor
of Pt/Pb(Zr,Ti)O3/LaNiO3/Si annealed at 600 °C displayed a good P-E hysteresis characteristic and was fatigue-free even after 1011 switching cycles.
Received: 25 May 2000 / Accepted: 9 August 2000 / Published online: 30 November 2000 相似文献
125.
J.A. Chaos J. Gonzalo C.N. Afonso J. Perrière M.T. García-González 《Applied Physics A: Materials Science & Processing》2001,72(6):705-710
Laser ablation of single-crystal LiNbO3 in a gas environment is used to grow films on (100) Si substrates heated to 650 °C. The film composition and crystallinity
are studied as a function of the nature (reactive, O2, or inert, Ar) and pressure of the gas environment applied during deposition and cooling-down processes, the laser energy
density and the target–substrate distance. Experimental results show that a gas pressure close to 1 mbar is required to produce
stoichiometric films in either O2 or Ar. The modification of the laser energy density and the target–substrate distance allows us to improve the crystallinity
of the films that become textured along the (006) direction. The influence of the experimental parameters on the film properties
is discussed in the frame of the formation of a blast wave, that leads to the focusing of the expanding Li species and thus,
to the increase of the Li content in the films.
Received: 8 February 2001 / Accepted: 9 February 2001 / Published online: 3 May 2001 相似文献
126.
J. Gonzalo R. Gómez San Román J. Perrière C.N. Afonso R. Pérez Casero 《Applied Physics A: Materials Science & Processing》1998,66(5):487-491
2 , Ar) in a broad pressure range (10-7–1 mbar) are correlated to the plasma expansion dynamics. It is found that the deposited films present an excess of Ba in
the intermediate pressure range (10-2<P<10-1 mbar) and a peaked distribution of Ba to Ti atoms ratio, that is not related to either the substrate temperature or the nature
of the gas environment. The results are discussed in terms of the dependence of the plume length (LP) on the gas pressure and the existence of scattering processes for distances (d) from the target lower than LP and the diffusion of the ejected species for LP<d.
Received: 7 November 1997/Accepted: 8 November 1997 相似文献
127.
F. P. Schäfer 《Applied physics. B, Lasers and optics》1986,39(1):1-8
The radial and axial pump power distribution in the line focus of a cone (as simplest example of an axicon) is discussed. It is also shown that four conical surfaces covered with antireflection coatings can make an efficient polarizer for radial and tangential polarization of a light beam. Glass cones can be used as efficient pump optics for laser-pumped lasers. The advantages of the novel pumping scheme are discussed in detail for the cases of dye-laser and x-ray laser pumping. 相似文献
128.
In this paper, we extend Parikh’s (massless particles) and Zhang’ work to massive particles’ Kerr black hole tunnelling. By treating the massive particle as de Broglie wave, we calculate the emission rates of the particles across the event horizon of the Kerr black holes. Our result is successful and is in agreement with the form of the massless particles. 相似文献
129.
Thin film of both A- and B-site co-substituted Sr0.8Bi2.2Ta2O9 (SBT) by Pr3+ and Nb5+, i.e. Sr0.8Pr0.1Bi2.1Ta1.5Nb0.5O9 (SPBTN) was fabricated on Pt/Ti/SiO2/Si substrates by metalorganic decomposition method. The Nb5+ substitution at B-site and Pr3+ substitution at A-site enhanced the remanent polarization and reduced the coercive field of the films, respectively. The remanent polarization (2Pr) value of the SPBTN film was 22 μC/cm2. The coercive field (2Ec) value of the SPBTN film was 102 kV/cm, which was much lower than that of SBTN (165 kV/cm). The effects of substitution on structural and ferroelectric properties of SBT were discussed in detail. As a result, the A- and B-sites co-substitution may be one of the promising ways to improve ferroelectric properties of SBT. 相似文献
130.
Structural aspects of phase transitions in barium titanate are analysed from a crystal-chemical point of view. The respective discussion is focused on two possible sources of ferroelectric deformation of TiO68− octahedron. First, gradual changes of π-electron localisation are considered. Under an assumption of a mean field related to actual crystal symmetry, an adequate model is proposed. The values of bond orders are evaluated from resonance structures. They are compared with respective bond lengths. Another source of the ferroelectric deformation, which is taken into consideration, relates to the Ti-ion movements between eight potential minima on the cube diagonals. The analysis of the problem is grounded within adiabatic (local field) approximation and follows ideas of an eight-site model. The crystal structure is treated as a result of averaging of atomic positions according to the postulated disorder. Comparison of the X-ray interatomic distances with the values calculated from the disorder model is made. The collected data generally prove that the ferroelectric deformation of the TiO68− octahedron, which is observed in barium titanate, contains two components. One is related to the changes of structural disorder degree and should be considered as a main factor. The other includes the effects attributed to the changes of π-electron localisation. 相似文献