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941.
J.?KongEmail author D.Y.?Tang S.P.?Ng B.?Zhao L.J.?Qin X.L.?Meng 《Applied physics. B, Lasers and optics》2004,79(2):203-206
We report on a diode end-pumped passively mode-locked Nd:GdVO4 laser. By using a GaAs wafer simultaneously as the saturable absorber and the output coupler, stable continuous-wave mode locking was achieved. The pulse width was measured to be 18.9 picoseconds at a repetition rate of 370 MHz. The most remarkable property of the laser is that its repetition rate can be changed from 370 MHz to 3.348 GHz by simply changing the cavity length. An average output power of 3.46 W at a 3.348 GHz repetition rate was obtained with a 14 W pump power. To our knowledge, this is the first demonstration of a passively mode-locked Nd:GdVO4 laser using a GaAs wafer as the saturable absorber. PACS 42.55.Rz; 42.60.Fc; 42.55.Xi. 相似文献
942.
Z.X.?QinEmail author Z.Z.?Chen Y.Z.?Tong X.M.?Ding X.D.?Hu T.J.?Yu G.Y.?Zhang 《Applied Physics A: Materials Science & Processing》2004,78(5):729-731
The contacts of Ti/Au, Ti/Al/Au, and Ti/Al/Ni/Au films deposited on n-GaN were studied by current–voltage (I–V) and transmission-line-method measurements. The effect of annealing temperature on specific contact resistivity has been investigated by changing the annealing temperature from 400 to 900 °C. Ti/Al/Au and Ti/Al/Ni/Au films were superior to the bilayer (Ti/Au) in ohmic contact characteristics and thermal stability. The Ti/Al/Ni/Au composite showed the best thermal stability due to the fact that Ni plays a more important role than the alloy of Ti/Al in preventing the interdiffusion of Ti, Al, and Au. The lowest contact resistivity (10-7cm2) to n-GaN was obtained for the Ti/Al/Ni/Au sample by short-time/high-temperature annealing. The formation mechanism of ohmic contacts to n-GaN is also discussed. PACS 73.40.Cg; 73.61.Ey 相似文献
943.
J.?Wang Z.?Li W.?Xu X.?Guo W.?Cai Q.?Wang X.?Chen W.?LuEmail author 《Applied Physics A: Materials Science & Processing》2004,79(7):1809-1811
The hydrogen-enhanced recrystallization during thermal annealing in N+-implanted GaAs has been studied by combinatorial implantation process. Raman spectroscopy was used to study the crystallization properties of a set of hydrogenated cells on the N+-implanted GaAs wafer. A whole competitive process between H+ implantation-induced damage and recovery in the regrowth process of amorphous GaAs was observed within the proton dose region of 1.6×1015 to 1.1×1017 cm-2. In H+ dose region of 2.1×1016 to 5.4×1016 cm-2, H-enhanced recovery of crystal dominates the regrowth process. The crystal quality is better than that of unhydrogenated cell of N+-implanted GaAs in the H+ dose range from 4.7×1016 to 8.1×1016 cm-2. It is suggested that the vacancy supersaturation produced during hydrogen irradiation is dominantly responsible for the enhancement of thermal regrowth in the N+-implanted GaAs. Both the crystallization and amorphization process are clearly observed in different proton implantation dose regions. PACS 61.72.Vv; 63.20.Dj; 81.05.Ea 相似文献
944.
Q.?Zhao H.Z.?Zhang B.?Xiang X.H.?Luo X.C.?Sun D.P.?YuEmail author 《Applied Physics A: Materials Science & Processing》2004,79(8):2033-2036
Selenium dioxide nanowires were fabricated as the co-products of ZnSe nanostructures. The SeO2 nanowires have diameters between 2070 nm and lengths up to several hundred micrometers. The morphology and microstructure of the nanowires were analyzed using TEM, and the growth mechanism of the SeO2 nanowires was explained under the framework of a vapor-solid model, in which structure defects may play a very important role in the nanowire growth. The nanostructured SeO2 materials may find application in both catalytic and biological fields. PACS 81.07.-b; 81.16.-c; 81.07.Nb; 81.05.-t; 68.37.Lp 相似文献
945.
W.?ZhongEmail author X.S.?Liu H.Y.?Jiang L.J.?Zhao Y.W.?Du N.?Zhang 《Applied Physics A: Materials Science & Processing》2004,78(4):575-579
Polycrystalline layered-perovskites La2.5-xK0.5+x·Mn2O7+ (0<x<0.5) have been prepared by a modified sol-gel method and their structures, and magnetic and electric properties have been studied. Experimental results show that these materials exhibit ferromagnetic-to-paramagnetic phase transitions at 200, 225, 235, 247, and 253 K for x=0.05, 0.15, 0.25, 0.35, and 0.45, respectively. A large deviation between the metal-insulator transition temperature (T) and the magnetic transition temperature (TC) is observed, and a large magnetoresistance (MR) effect with /0 of 40% at 12 kOe is obtained over a wide temperature range. These behaviors are quite different from those observed in the well-knownABO3-type perovskite manganites. PACS 75.30.Gw; 75.30.Et; 81.20.-n 相似文献
946.
L.?Dai G.Z.?Ran J.C.?Zhang X.F.?Duan W.C.?Lian G.G.?QinEmail author 《Applied Physics A: Materials Science & Processing》2004,79(1):139-142
We have studied the influence of C and Si ion implantation with different implantation doses on yellow luminescence (YL) from GaN. Three kinds of GaN samples were used. In their as-grown states, #1 samples had strong YL, #2 samples had no YL, while #3 samples had weak YL. Our experimental results show that: (i) after annealing at 950 °C, the YL intensity for Si ion implanted #1 sample decreased with increasing implantation dose, while that for C ion implanted #1 sample exhibited a reverse rule; (ii) for #2 samples, C ion implantation produced much stronger YL than Si ion implantation did after annealing at 950 °C; (iii) the YL intensity sequence for Si ion implanted and 950 °C annealed #1, #2, and #3 samples was consistent with that for the unimplanted #1, #2, and #3 samples. However, the YL intensity sequence for the C ion implanted and 950 °C annealed #1, #2, and #3 samples reversed with that for the unimplanted ones. In order to explain all these phenomena, we suggested a physical model which claims that the deep C center is another important origin of YL in GaN, and during C ion implantation, the C ion prefers to combine with a VGa to form a CGa. PACS 78.55.-m, 85.40.Ry, 68.55.Ln 相似文献
947.
N.?Fang C.?Sun X.?ZhangEmail author 《Applied Physics A: Materials Science & Processing》2004,79(8):1839-1842
The trade-off between process speed and resolution in microstereolithography (SL) roots on the diffusion-limited kinetics of photopolymerization. Using a numerical model, we have investigated the influence of diffusion dominant effect under high photon flux. Radical depletion turned out to limit the smallest feature achievable to the order of 10 m under high process speed. A solution of pulsed laser curing is proposed in order to realize sub-micron resolution in high speed SL process. PACS 66.30.Ny; 85.85.+j; 85.40.Ux 相似文献
948.
Dynamics of femtosecond laser interactions with dielectrics 总被引:1,自引:0,他引:1
S.S.?MaoEmail author F.?Quéré S.?Guizard X.?Mao R.E.?Russo G.?Petite P.?Martin 《Applied Physics A: Materials Science & Processing》2004,79(7):1695-1709
Femtosecond laser pulses appear as an emerging and promising tool for processing wide bandgap dielectric materials for a variety of applications. This article aims to provide an overview of recent progress in understanding the fundamental physics of femtosecond laser interactions with dielectrics that may have the potential for innovative materials applications. The focus of the overview is the dynamics of femtosecond laser-excited carriers and the propagation of femtosecond laser pulses inside dielectric materials. PACS 61.80.Ba; 52.38.Mf; 42.65.Jx; 78.47.+p; 71.35.-y 相似文献
949.
Parlitz U Hornstein A Engster D Al-Bender F Lampaert V Tjahjowidodo T Fassois SD Rizos D Wong CX Worden K Manson G 《Chaos (Woodbury, N.Y.)》2004,14(2):420-430
The hysteretic nonlinear dependence of pre-sliding friction force on displacement is modeled using different physics-based and black-box approaches including various Maxwell-slip models, NARX models, neural networks, nonparametric (local) models and dynamical networks. The efficiency and accuracy of these identification methods is compared for an experimental time series where the observed friction force is predicted from the measured displacement. All models, although varying in their degree of accuracy, show good prediction capability of pre-sliding friction. Finally, we show that even better results can be achieved by using an ensemble of the best models for prediction. 相似文献
950.
L.?Dai X.L.?ChenEmail author X.?Zhang T.?Zhou B.?Hu 《Applied Physics A: Materials Science & Processing》2004,78(4):557-559
ZnO/SiO2 coaxial nanocables have been synthesized on silicon substrates by simply evaporating zinc powder under an argon and argon/oxygen mixed atmosphere sequentially. The diameters of these nanocables vary from 50 to 100 nm and the lengths up to several millimeters. Electron microscopy and chemical composition investigations reveal that the nanocable consists of a crystalline ZnO core surrounded by an amorphous silica sheath. The electron diffraction pattern proves that the long-axis direction of ZnO cores grows along the [0001] direction. Silica nanotubes with wall structures have been obtained by the selective dissolution of the cores with hydrochloric acid. PACS 81.10.Bk; 81.05.Hd 相似文献