Removal of doped poly(methylmetacrylate) from tungsten and titanium substrates by femto- and nanosecond laser cleaning

The influence of different laser pulse lengths on the removal of a polymer layer from metal substrates was investigated. As model systems, doped poly(methylmetacrylate) (PMMA) on titanium and tungsten substrates were selected.The ablation threshold and irradiation spot morphology of titanium and tungsten were compared for femtosecond (fs) and nanosecond (ns) laser irradiation and different pulse numbers. Nanosecond laser treatment resulted in a non-homogeneous surface morphology for both titanium and tungsten substrates. Femtosecond irradiation of tungsten revealed a homogeneous ablation spot with little changes in the surface morphology. For titanium, the formation of columnar structures within the irradiation spot was observed.Two different dopant concentrations were used for PMMA to achieve an equal linear absorption coefficient for the femto- and nanosecond laser wavelengths of 790 and 1064 nm. The best results were achieved for the removal of doped PMMA by femtosecond laser irradiation, where only a minimal modification of the metal surface was detected. In the case of nanosecond laser exposure, a pronounced change of the structure was observed, suggesting that damage-free cleaning of the selected metal may only be possible using femtosecond laser pulses. Different experimental parameters, such as laser fluence, pulse repetition rate and sample speed were also investigated to optimize the cleaning quality of doped PMMA from tungsten substrates with femtosecond laser pulses.     

Synthesis and properties of new photosensitive triazene polyacrylates

1‐(Phenyl)‐3‐(2‐acryloyloxyethyl)‐3‐methyl triazene‐1 (M1) and 1‐(p‐nitrophenyl)‐3‐(2‐acryloyloxyethyl)‐3‐methyl triazene‐1 (M2) were synthesized to study the substituent effect of the triazene unit on the copolymerization with methyl methacrylate (MMA). From the ¹H NMR spectra of the resulting copolymers, their compositions were determined to be 1:3.18 M1/MMA and 1:2.45 M2/MMA, respectively. The polymers were examined with respect to their structure, thermal properties, and surface morphology. The influence of the triazene structure on the photosensitive properties of the copolymers exposed to ultraviolet/laser irradiation was also investigated and compared with that of the parent derivatives. The copolymer containing the phenyl triazene chromophore as the photochemically most active group exhibited a low threshold of ablation and a high etching rate for fluences under 400 mJ cm^?2. Scanning electron microscopy images confirm the formation of ablated craters more clearly in the copolymer made with M1, for which the thermal effects of the ablation mechanism were visible only with 2500× magnification. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5271–5282, 2006     

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