摘要:

Laser ablation of poly(methyl methacrylate) and polystyrene films doped with porphyrins have been studied by etch depth measurement and time resolved spectroscopy. At the laser intensity above the ablation threshold, the broadening of fluorescence spectra of porphyrins was observed. The spectra broadened within laser pulse duration, which suggests that bulk polymer matrices were heated up by sensitizer molecules leading to the laser ablation. Transient changes in absorptivity of the films at the laser wavelength were found during the laser pulse. From these results, it is considered that repetitive photo‐absorption and relaxation in electronic excited states of sensitizers play a key role in sensitizer‐induced laser ablation. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50412

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Here, we present a new approach to simulate the molecular dissociation dynamics in strong IR laser field, which combines a quantum description of the dynamics of electronic states of a molecule and classical dynamics within a single electronic state. As an example, computer simulation results on HCl+dissociation in intense (I∼1014W/cm2) laser field in two‐level approximation are presented. The probabilities of different stable states of a molecule at the end of laser pulse are calculated. It is shown that molecule’s dissociation dynamics in intense laser field has a quantum stochastic nature. It is argued that the used model can be applied to multiatomic molecules as well. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50413

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Textured Nd doped yttrium aluminum garnet (Y3Al5O12,YAG) crystalline thin films have been grown on silicon substrates by pulsed laser deposition method. The films were characterized by means of Rutherford backscattering spectrometry (RBS), x‐ray analysis, atomic force microscopy (AFM). The results indicate that the composition of these films are that of YAG doped with Nd (1.2, 2.4 at. %). AFM image shows that the Nd:YAG crystallites were oriented to the silicon surface at the substrate temperature of 700 °C. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50415

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Laser assisted silicon etching was developed for packaged microsensors. Laser assisted Cr CVD was applied for selective metallization on nonplaner surfaces. High rate laser CVD using low temperature condensation method was developed for micro assembly and projection patterning. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50416

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The problem of deep laser melting of the metals and alloys is theoretically and experimentally studied. It is shown that the process of laser melting consists of two stages: the formation of a melt buffer layer, and its penetration under the action of the saturated vapor pressure. There has been investigated an optimal regime of pulsed laser welding without melt species ejection as a regime when the affecting pulse is close in its form to the step‐like pulse consisting of two parts. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50417

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Diamond‐like carbon (DLC) films were deposited by laser ablation, using an ArF laser and a KrF laser. The target of laser ablation was frozen acetylene, instead of a conventional graphite. The DLC films were produced by the ArF laser between room temperature and 300 °C. The C‐H bond was missing from the films produced by the ArF laser, while it was present for the films produced by the KrF laser. It was possible to deposit particle‐free films in contrast to laser ablation of the graphite target. Experimental results suggested the importance of energetic charged species ejected from frozen acetylene. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50418

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have proposed the new PLD technique, called the ‘‘Eclipse PLD Method,’’ wherein the droplet problem (peculiar to the standard PLD technique) is almost completely removed. This method is characterizes by a simple placement of a shadow mask between the target and substrate. The present paper deals with traveling behavior of the ablated particles in the chamber and discloses the exclusive role of the shadow mask for elimination of the droplet particles. From comparison of the growth rates between the analysis and experiment, it was made clear that the neutral gas molecules serve as the dominant scatterer against the traveling ablated particles in the PLD, and consequently our eclipse‐method is basically supported by the intensive diffusion of growth species. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50419

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Transversely excited atmospheric (TEA) CO2laser ablation of boron nitride ceramics in both cubic and hexagonal phases (cBN, hBN) was demonstrated. A TEA CO2laser oscillating at a wavelength of 9.2 &mgr;m, which coincides with a TO‐phonon spectrum of the cBN, could ablate the cBN ceramics more efficiently than with 10 &mgr;m band radiation. The hBN samples were also ablated well with 9.2 &mgr;m laser irradiation, however, the ablated site color changed to black due to a boron rich phase left on the surface. In the case of hBN sintered with Al2O3and SiO2, the ablation threshold fluence is determined by the one of Al2O3, which is the highest threshold among the three elements. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50420

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have studied the structural change of targets and the ablated particles to classify the characteristics of laser ablation. Neutral atoms, positive ions and global particles are generated from metal targets irradiated by the KrF excimer laser beam. The average energy of 100∼180 eV per atom is required to ablate atomic particles. The targets after irradiation show the change of surface morphologies and X‐ray diffraction patterns due to heating. The change of chemical compositions and the resolidified layer are not observed. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50421

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The time required for the cluster growth (the stagnation time) of 0.3 ms was deduced from velocity and mass distribution measurements of iron cluster beams. From shock speed measurements in an ambient gas, initial density and temperature of aluminum plume vaporized by a laser pulse were estimated to be 1021cm−3and 6000 °K, respectively. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.50422

出版商:AIP    

年代:1996

数据来源: AIP