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1.
2 to 2.5 mJ/cm2 when a 0.5 ps pulse is used instead of a 15 ns laser pulse. Measurements on liquid indium show a different behavior. With 15 ns
laser pulses the threshold fluence is lowered by a factor of ∼3 from 100 mJ/cm2 for solid indium to 30 mJ/cm2 for liquid indium. In contrast, measurements with 0.5 ps laser pulses do not show any change in the ablation threshold and
are independent of the phase of the metal at 2.5 mJ/cm2. This behavior could be explained by thermal diffusion and heat conduction during the laser pulse and demonstrates in an
independent way the energy lost into the material when long laser pulses are applied. Time-of-flight measurements to investigate
the underlying ablation mechanism show thermal behavior of the ablated indium atoms for both ps and ns ablation and can be
fitted to Maxwell-Boltzmann distributions.
Received: 2 December 1996/Accepted: 11 December 1996 相似文献
2.
Received: 3 August 1998/Accepted: 7 August 1998 相似文献
3.
The GaCH3 radical has been directly detected by far UV laser mass spectrometry for the first time, as a UV laser photofragment from gaseous trimethylgallium Ga(CH3)3, but not from triethylgallium, Ga(C2H5)3. The relative yield Y() of GaCH3 was measured, at various UV photolysis laser wavelengths =193, 210 and 245 nm, and follows the absorption spectrum of the Ga(CH3)3 precursor molecules. 相似文献
4.
M. Lassithiotaki A. Athanassiou D. Anglos S. Georgiou C. Fotakis 《Applied Physics A: Materials Science & Processing》1999,69(3):363-367
0 ∝t1/2. The best results are expected for a circular top-hat beam shape.
Received: 15 January 1999 / Accepted: 18 January 1999 相似文献
5.
Femtosecond,picosecond and nanosecond laser ablation of solids 总被引:21,自引:0,他引:21
B. N. Chichkov C. Momma S. Nolte F. von Alvensleben A. Tünnermann 《Applied Physics A: Materials Science & Processing》1996,63(2):109-115
Laser ablation of solid targets by 0.2–5000 ps Ti: Sapphire laser pulses is studied. Theoretical models and qualitative explanations of experimental results are presented. Advantages of femtosecond lasers for precise material processing are discussed and demonstrated. 相似文献
6.
We use tunable UV laser light in the region 200–320 nm, produced by frequency doubling the output of a dye laser, for the decomposition of organometallic compounds. This method has been applied to TMA, trimethylaluminum Al(CH3)3. Only the TMA monomer absorbs UV light for >220 nm. TMA decomposes by one-photon absorption mainly into two channels: aluminum atoms Al plus organic fragments, and aluminummonomethyl AlCH3 molecules plus organic fragments. The ratio [Al]/[AlCH3] is wavelength dependent. We present a mechanism to explain the photolysis of trimethyl compounds of group III elements (Al, Ga, In). 相似文献
7.
Laser ablation of thin Ni films on fused silica by 0.5 ps KrF-excimer-laser pulses at 248 nm is reported. The onset of material removal from different film thicknesses (0.1, 0.3, 0.6 and 1.0 m) was measured in a laser ionization time-of-flight mass spectrometer by the amount of Ni atoms vs laser fluence. Significant amounts of metal atoms are already evaporated at laser fluences around 20 mJ/cm2, a threshold up to 100 times smaller compared to the one for 14 ns pulses. In contrast to ns laser pulses, the ablation threshold for 0.5 ps pulses is independent of the film thickness. These results reflect the importance of thermal diffusion in laser ablation of strongly absorbing and thermally good conducting materials and prove that for ablation with short pulses, energy loss to the bulk is minimized. 相似文献
8.
Z.-M. Ren P.-N. Wang Y.-C. Du Z.-F. Ying F.-M. Li 《Applied Physics A: Materials Science & Processing》1997,65(4-5):407-409
2 radicals when the 355 and 1064 nm outputs of a Nd:YAG laser were applied. While for the 532 nm ablation, a relatively higher
concentration of excited atomic carbon was obtained. Different Raman and FTIR spectral features were observed from the deposited
films with different ablation wavelengths. The 532 nm laser ablation is proposed for the synthesis of high quality carbon
nitride films.
Received: 16 October 1996 / Accepted: 11 April 1997 相似文献
9.
In this work a frequency-doubled Nd:glass laser with a pulse duration of 250 fs has been used to ablate a TaC target and to deposit thin films on silicon. The results have been compared with those previously obtained by nanosecond pulsed laser deposition and evidence of large differences in the plasma characteristics has been revealed. In particular, in the femtosecond and nanosecond plumes the energy and the velocity of neutral and ionized particles are very different. The features of femtosecond ablation include the delayed emission from the target of large and slow particles. The characteristics of the femtosecond plasma are clearly related to the morphology and composition of the deposited films and the results show a nanostructure consisting of a large number of spherical particles, with a mean diameter of about 50 nm, with a stoichiometry corresponding to Ta2C. To explain these features, an ablation-deposition mechanism, related to the ejection of hot particles from the target, is proposed. 相似文献
10.
Synthesis of nanocrystalline material by sputtering and laser ablation at low temperatures 总被引:1,自引:0,他引:1
P. Ayyub R. Chandra P. Taneja A.K. Sharma R. Pinto 《Applied Physics A: Materials Science & Processing》2001,73(1):67-73
Physical vapor deposition techniques such as sputtering and laser ablation – which are very commonly used in thin film technology
– appear to hold much promise for the synthesis of nanocrystalline thin films as well as loosely aggregated nanoparticles.
We present a systematic study of the process parameters that facilitate the growth of nanocrystalline metals and oxides. The
systems studied include TiO2, ZnO, γ-Al2O3, Cu2O, Ag and Cu. The mean particle size and crystallographic orientation are influenced mainly by the sputtering power, the substrate
temperature and the nature, pressure and flow rate of the sputtering gas. In general, nanocrystalline thin films were formed
at or close to 300 K, while loosely adhering nanoparticles were deposited at lower temperatures.
Received: 31 October 2000 / Accepted: 9 January 2001 / Published online: 26 April 2001 相似文献
11.
Pulsed-discharge-aided laser ablation synthesis of nanoscale aluminum nitride powders 总被引:1,自引:0,他引:1
P.N. Wang Q. Pan N.H. Cheung S.C. Chen 《Applied Physics A: Materials Science & Processing》1998,67(2):233-236
2 ) discharges were shown to efficiently generate atomic nitrogen that promoted the synthesis of high-purity aluminum nitride
powders formed by pulsed-laser ablation of aluminum targets. The interaction between the nitrogen discharge plasma and the
ablated aluminum plume depended on the synchronisation of the two pulsed events for maximum overlap of the transient reactants.
By monitoring the optical emissions of the reactive N+ species and analysing the synthesised powder with X-ray photoelectron spectroscopy, it was found that when laser ablation
occurred at about 3 μs after the pulsed discharge, the N+ emission from the overlapping plasma was the most intense and the purity of the aluminum nitride synthesized was the highest.
Received: 8 September 1997/Accepted: 8 September 1997 相似文献
12.
Y.V. Afanasiev V.A. Isakov I.N. Zavestovskaya B.N. Chichkov F. von Alvensleben H. Welling 《Applied Physics A: Materials Science & Processing》1997,64(6):561-572
Received: 29 November 1996/Accepted: 14 March 1997 相似文献
13.
J. Šonský J. Lančok M. Jelínek J. Oswald V. Studnička 《Applied Physics A: Materials Science & Processing》1998,66(5):583-586
3 (YAP) thin films as a promising material for application in a planar waveguide laser has been studied. The films have been
grown on sapphire(0001) and YAP(001) substrates by laser ablation. The influence of the substrate temperature and ambient
oxygen pressure on the crystalline structure, concentration of Nd incorporated into films, and consequent luminescence spectra
were investigated. The waveguiding properties were observed and refractive index of the films was evaluated.
Received: 8 February 1998/Accepted: 9 February 1998 相似文献
14.
In the present paper, a 2D finite element model based on the heat-conduction equation and on the Hertz-Knudsen equation for vaporization was developed and used to simulate the ablation of TiC by Nd:YAG and KrF pulsed laser radiation. The calculations were performed for fluences of 8 and 10 J/cm2, which according to experimental results obtained previously, correspond to large increases of the ablation rate. The calculated maximum surface temperature of the target for both lasers is higher than the estimated value of TiC critical temperature, corroborating the hypothesis that the increase of the ablation rate is explained by the explosive boiling mechanism. 相似文献
15.
M. Dienstbier R. Beneš P. Rejfiř P. Sladký 《Applied physics. B, Lasers and optics》1990,51(2):137-140
Optothermal methods for the study of UV laser ablation are discussed. Pyroelectric and photoacoustic measurements for PMMA and Al irradiated at 193 nm are reported. Ablation thresholds are estimated. The different mechanisms contributing to the signal generation are discussed. 相似文献
16.
M. Morcrette A. Gutiérrez-Llorente A. Laurent J. Perrière P. Barboux J.P. Boilot O. Raymond T. Brousse 《Applied Physics A: Materials Science & Processing》1998,67(4):425-428
x La2/3+yTiO3-δ perovskite (with δ≤0.5) were deposited by the laser ablation technique from Li0.33La0.56TiO3 targets. Their growth onto MgO substrateswas studied as a function of the oxygen pressure. For films grown in vacuum (10-6 mbar), a La0.63TiO2.5 composition was obtained, meaning that Ti3+ alone is present in the films, while Li ions are not incorporated under these conditions. This material shows good electric
conductivity (ρ=500 mΩ cm). By contrast, insulating films with a Li0.1La0.70TiO3 composition corresponding to the Ti4+ species were obtained at high oxygen pressures (>0.05 mbar). For all conditions, textured films were grown with different
orientations depending on the temperature and the oxygen pressure.
Received: 10 September 1997/Accepted: 24 November 1997 相似文献
17.
Thin films of the conducting polymer poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS) were deposited by resonant infrared laser vapor deposition (RIR-LVD). The PEDOT:PSS was frozen in various matrix solutions and deposited using a tunable, mid-infrared free-electron laser (FEL). The films so produced exhibited morphologies and conductivities that were highly dependent on the solvent matrix and laser irradiation wavelength used. When deposited from a native solution (1.3% by weight in water), as in matrix-assisted pulsed laser evaporation (MAPLE), films were rough and electrically insulating. When the matrix included other organic “co-matrices” that were doped into the solution prior to freezing, however, the resulting films were smooth and exhibited good electrical conductivity (0.2 S/cm), but only when irradiated at certain wavelengths. These results highlight the importance of the matrix/solute and matrix/laser interactions in the ablation process. 相似文献
18.
F. Kokai Y. Koga Y. Kakudate M. Kawaguchi S. Fujiwara M. Kubota K. Fukuda 《Applied Physics A: Materials Science & Processing》1994,59(3):299-304
Laser-ionization Time-Of-Flight (TOF) mass-spectrometric studies have been carried out on the 532 nm and 1064 nm laser ablation products from a nitrogen-rich polymer. The polymer used had an elemental composition of C6.0N8.9H3.4 and consisted of C=N, C-N, and N-H chemical bonds. The TOF mass spectra observed were composed of various peaks (150 amu) depending on the ablation laser wavelength. The primary peaks were assigned to C+, CN+, CHnN+
2 (n=1–3) and C2H2N+
3 for 532 nm ablation, and C+, C+
3, HCN+, HCCN+, CH2NH+, HNCN+, H3NCN+, and C4H4N+
7 for 1064 nm ablation. The flight velocity distributions with peak velocities ranging from 8.6×103 cm/s to 3.8×104 cm/s were measured for these products. The distinct velocity distributions observed between small and large products indicate the presence of two origins in the fragment ejection process from the polymer for both 532 nm and 1064 nm ablation. Furthermore, we suggest an importance of the translational energy of the fragments for the product generation in the laser plume. 相似文献
19.
P. Clarke P.E. Dyer P.H. Key H.V. Snelling 《Applied Physics A: Materials Science & Processing》1999,69(7):S117-S120
Ultraviolet (UV) laser thresholds for plasma ignition on solid targets predicted from electron-neutral collisional heating are generally much higher than those observed experimentally. This inconsistency was reconciled by Rosen, et al. [2], who showed that excited-state photoionization played a key role in long-pulse UV laser breakdown. Here we develop a related model but with emphasis on pulses of ~10 ns duration. Experimental results are also reported for titanium, copper, silicon, and ferulic acid targets in vacuum, irradiated with combinations of the XeF, KrF, and ArF lasers for comparison with predictions. 相似文献