Dopant induced ablation of poly(methyl methacrylate) at 308 nm

Lippert, Thomas; Webb, R. L.; Langford, S. C.; Dickinson, J. T.

doi:10.1063/1.369331

Cited by 58 publications

(70 citation statements)

References 61 publications

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“…These experiments may also provide us with more information on the significance of gas-dynamic processes among the emitted fragments, where a substantial population of phenyl radicals appears to have been accelerated by entrainment, perhaps by reducing the density of the emitted N 2 to where we might be able to see the direct phenyl radical time-of-flight. It is possible, as proposed in an earlier laser-polymer study [224], that both photochemical and photothermal mechanisms are occurring.…”

Section: Discussionmentioning

confidence: 96%

“…The 35-amu signal intensity increases slowly at the beginning and much faster at the high fluence end. This can again be due to a dense surface region with a lower amount of solvent, which has been previously found for PMMA cast from chlorobenzene [224]. Other possibilities are the higher ablation rates at higher fluences, which result in higher Cl signals, or a more effective decomposition of the chlorobenzene at higher fluences.…”

Section: 265mentioning

confidence: 86%

“…At low fluences the signal is quite low and increases significantly at fluences above 150 mJ cm 2 . This can be explained by a surface region which contains less solvent than the deeper layers [224]. As the fluence increases, the depth of the ablated crater increases and more solvent is removed.…”

Section: 265mentioning

confidence: 98%

“…In the case of polystyrene irradiated at 193 nm, an adiabatic expansion model inferred temperatures of 2,350 K [223]. When absorbing chromophores were purposefully added to PMMA, a combined photochemical/photothermal mechanism was evident [224]. In general, most TOF-MS studies have given strong indications for photothermal ablation mechanisms.…”

Section: Introductionmentioning

confidence: 97%

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Laser Application of Polymers

Lippert

2004

Polymers and Light

148

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Laser ablation of polymers has been studied with designed materials to evaluate the mechanism of ablation and the role of photochemically active groups on the ablation process, and to test possible applications of laser ablation and designed polymers. The incorporation of photochemically active groups lowers the threshold of ablation and allows high-quality structuring without contamination and modification of the remaining surface. The decomposition of the active chromophore takes place during the excitation pulse of the laser and gaseous products are ejected with supersonic velocity. Time-of-flight mass spectrometry reveals that a metastable species is among the products, suggesting that excited electronic states are involved in the ablation process. Experiments with a reference material, i.e., polyimide, for which a photothermal ablation mechanism has been suggested, exhibited pronounced differences. These results strongly suggest that, in case of designed polymers which contain photochemically active groups, a photochemical part in the ablation mechanism cannot be neglected. Various potential applications for laser ablation and the special photopolymers were evaluated and it became clear that the potential of laser ablation and specially designed material is in the field of microstructuring. Laser ablation can be used to fabricate three-dimensional elements, e.g., microoptical elements.Keywords Laser ablation · Ablation mechanism · Photopolymers · Polyimide · Spectroscopy This was not always true, of course. For many years, the laser was viewed as "an answer in search of a question". That is, it was seen as an elegant device, but one with no real useful application outside of fundamental scientific research. In the last two to three decades however, numerous laser applications have moved from the laboratory to the industrial workplace or the commercial market. Lasers are unique energy sources characterized by their spectral purity, spatial and temporal coherence, and high average peak intensity. Each of these characteristics has led to applications that take advantage of these qualities: -Spatial coherence: e.g., remote sensing, range finding and many holographic techniques. -Spectral purity: e.g., atmospheric monitoring based on high-resolution spectroscopies. -and of course the many other applications in communication and storage, e.g., CDs.All of these high-tech applications have come to define everyday life in the late twentieth century. One property of lasers, however, that of high intensity, did not immediately lead to "delicate" applications but rather to those requiring "brute force". That is, the laser was used in applications for removing material or heating. The first realistic applications involved cutting, drilling, and welding, and the laser was little more advanced than a saw, a drill, or a torch. In a humorous vein A.L. Schawlow proposed and demonstrated the first "laser eraser" in 1965 [4], using the different absorptivities of paper and ink to remove the ink without damaging the und...

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Section: Discussionmentioning

confidence: 96%

Section: 265mentioning

confidence: 86%

Section: 265mentioning

confidence: 98%

Section: Introductionmentioning

confidence: 97%

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Laser Application of Polymers

Lippert

2004

Polymers and Light

148

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“…This means that more material is removed with pulses following the first pulse. The reason for this behavior is not yet fully understood but could be related to the preparation of the sample, where a dense skin layer may be formed [9].…”

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confidence: 99%

Changes in the etch rate of photosensitive polymers as a function of the pulse number

et al. 2004

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The ablation rates of a polyimide and a triazene polymer were studied gravimetrically by a quartz micro balance for 248-nm and 308-nm irradiation. Special care was taken to examine the dependence of the ablation rate at constant fluences for single pulses and the influence of consecutive pulses at the same position. A clear trend was observed in these measurements, i.e., that the mass loss after the first pulse is always different from values for the following pulses. This implies that it is very difficult to determine true ablation rates, which are the foundation of most ablation models. The differences of the mass loss between the first pulse and the following pulses is most probably due to carbonization of the material, resulting in varying ablation rates for the following pulses. The ablation rates are thus not a real material property but a superposition of the material ablation rates with the ablation rates of carbon and carbonized material. UV laser ablation of polymers is the objective of intense experimental and theoretical research due to the potential applications in many fields (chemistry, physics, biology, and electronics) [1,2]. Studies of the laser-induced decomposition or transformation of polymers with single pulses and laser fluences close to the threshold of ablation require very sensitive techniques such as a quartz crystal microbalance (QCM) and atomic force microscopy (AFM). One important question in polymer ablation is related to the ablation mechanisms, i.e., photochemical versus photothermal. The understanding of these mechanisms is important for the design of new materials (e.g., photosensitive polymers) or the optimization of existing industrial processes. Models play an important role in the understannding of these mechanisms. The mass loss during laser ablation is one important parameter for the development of theoretical models that decribe ablation.A mass loss (e.g., by QCM) due to photochemical reactions is expected for photosensitive polymers before a change

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Photoablation of Polymer Materials

Urech

Lippert

2010

Photochemistry and Photophysics of Polymer Materials

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Dopant induced ablation of poly(methyl methacrylate) at 308 nm

Cited by 58 publications

References 61 publications

Laser Application of Polymers

Laser Application of Polymers

Changes in the etch rate of photosensitive polymers as a function of the pulse number

Photoablation of Polymer Materials

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