Analysis of neutral fragments from ultraviolet laser irradiation of a photolabile triazeno polymer

Lippert, Thomas; Langford, S. C.; Wokaun, Alexander; Savas, Georgiou; Dickinson, J. T.

doi:10.1063/1.371800

Cited by 32 publications

(30 citation statements)

References 26 publications

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“…This work shows that the thermal contribution plays an important role in the ablation of very thin triazene films, as discussed previously for thick samples [17,42,43]. However, it is difficult to conclude the ablation mechanism from these experiments.…”

Section: Considerations On the Mechanismsupporting

confidence: 68%

Influence of thermal diffusion on the laser ablation of thin polymer films

et al. 2007

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The laser ablation of a photosensitive triazene polymer was investigated with a ns XeCl excimer laser over a broad range of thicknesses (10-400 nm). We found that the ablation threshold fluence increased dramatically with decreasing film thickness for films thinner than 50 nm. Ablation on substrates with different thermal properties (sapphire, fused silica, PMMA) was investigated as well, and a clear influence of the substrate material was obtained. A mathematical model combining thermal diffusion and absorption effects was used to explain the experimental data. The model is in good agreement with the experimental data and shows that heat diffusion into the substrate plays a crucial role for the ablation process of very thin films.PACS 52.38.Mf; 44.05.+e; 81.05.Lg IntroductionLaser ablation finds a broad range of applications because it allows us to create microstructures by dry etching, deposit material from a target to a substrate, perform analysis of fragments and is also used for some special applications, such as laser plasma thrusters [1,2].Material deposition by laser ablation is a useful tool in the field of materials processing. The pulsed laser deposition (PLD) technique allows us to transfer and produce films of inorganic [3,4] and organic materials [5][6][7][8]. Matrix-assisted pulsed laser evaporation (MAPLE) can be applied to transfer small molecules from a frozen matrix to a substrate [8,9]. One of the most promising techniques to transfer organic thin films is laser-induced forward transfer (LIFT), which allows us to deposit and pattern materials in the same process [10][11][12][13][14]. It consists of the following steps: a transparent substrate is coated with the material that has to be transferred. This so-called donor substrate is placed in front of a receiver plate and a laser pulse is applied through the donor. The coated material absorbs the laser pulse and is ablatively ejected and deposited on the receiver. This method is appropriate for metal deposition but not for sensitive materials, such as polymers, because these may be damaged by the thermal load and photochemical reactions due to irradiation. A modification of the technique can solve this problem. The principle is the application of a twolayer system: a sacrificial layer acting as an absorber and the transfer material are successively coated on the donor substrate. Upon receiving the laser pulse, the sacrificial layer absorbs the energy, is decomposed into gaseous fragments and provides the thrust for propelling the top layer onto the receiver [15]. Furthermore, the absorbing material protects the top layer from the laser pulse and is specially designed to decompose at low fluences. Among various polymers, triazenebased polymers (TP) show the lowest ablation threshold at 308 nm and are therefore the most promising materials for this application [16][17][18].It has been shown that this sacrificial layer allows us to transfer quantum dots [19], living cells embedded in a matrix [20] and even functional pixels of organic ligh...

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Section: Considerations On the Mechanismsupporting

confidence: 68%

Influence of thermal diffusion on the laser ablation of thin polymer films

et al. 2007

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“…78). The fast and slow components have been described in previous work at 248 nm [327,328]. The peak at intermediate energies was only observed when the quadrupole was aligned perfectly along a straight line from the sample.…”

Section: Additional Experimentssupporting

confidence: 68%

“…The TOF of the fast component (arriving <50 s after the laser pulse) is unusually short for a neutral molecule. Kinetic energy estimates, assuming that these molecules were emitted with a Gaussian energy distribution and experienced no subsequent collisions, range from 3-6 eV [327,328].…”

Section: Additional Experimentsmentioning

confidence: 99%

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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“…Various time-resolved techniques (i.e. time-resolved Raman spectroscopy [4,5], time-resolved infrared spectroscopy [6,7], time-resolved quadropole mass spectroscopy [8][9][10][11]) have been applied, resulting in new information about the chemical and physical processes involved in ablation. In this paper, additional time resolved methods, i.e.…”

Section: Introductionmentioning

confidence: 99%

Time-resolved techniques as probes for the laser ablation process

Hauer

Funk

Lippert

et al. 2005

Optics and Lasers in Engineering

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Laser material processing is an increasing market although many processes are still not yet fully understood. It was repeatedly emphasized that a better understanding of the transient processes can help to improve the understanding of the ablation mechanism. Examples using ns-surface interferometry, ns-shadowgraphy and emission spectroscopy are shown to illustrate how these techniques can be used to obtain new insights in the laser ablation processes.Time-resolved surface interferometry probes the remaining polymer, while ns-shadowgraphy and plasma spectroscopy observe the ablation products. Ns-shadowgraphy can be used for fluences just above the ablation threshold, to the fluences where a plasma is observed, which is probed by emission spectroscopy.Time-resolved ns-surface interferometry of a specially designed triazene polymer reveals that the surface morphology changes and thereby the surface removal occurs only during the laser pulse. Ns-shadowgraphy is used to observe the shockwave and the plume of fragments, which are generated during laser ablation. A comparison of the ablation properties of an energetic polymer at two different wavelengths (1064 and 193 nm) shows that the ejection of non-gaseous fragments (solid or liquid) is only detected after irradiation with 1064 nm. At higher laser fluences, plasma is formed, and the atomic (H), and diatomic species (CN, CH and C 2 ) are identified. r

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Analysis of neutral fragments from ultraviolet laser irradiation of a photolabile triazeno polymer

Cited by 32 publications

References 26 publications

Influence of thermal diffusion on the laser ablation of thin polymer films

Influence of thermal diffusion on the laser ablation of thin polymer films

Laser Application of Polymers

Time-resolved techniques as probes for the laser ablation process

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