Selective laser ablation of radiation exposed methyl acetoxy calix(6)arene
(Color online) Schematic representations of the dry development and traditional wet chemical development for MAC6. MAC6 becomes a positive resist under laser development. Dry development is carried out using a 532 nm CW laser to volatilize the e-beam exposed MAC6 in positive tone. A positively developed buttress pattern with 532 nm is shown. Chemical structure of MAC6 is shown on top left.
(Color online) Dependence of MAC6 ablation onset on laser power for unexposed and e-beam exposed films. As the e-beam dose increases, the ablation onset decreases while maintaining nonlinear dependence on laser power for all doses including unexposed films. Theoretically, a power-time combination in the gray area should selectively ablate exposed film over pristine MAC6. Inset shows a typical ablation curve; an integrated fluorescence vs laser exposure time curve can be seen in Fig. 4. Ablation onset, the appearance of strong fluorescence signal has previously been correlated to the ablation of the film.
(Color online) Raman spectra of prestine (black), e-beam exposed (2mC at 10 keV) and laser exposed (532 nm, exposure time just below the ablation threshold) of methyl acetoxy calix(6)arene. Fluorescence background has been removed. Spectra have been normalized to the height of the CH stretching mode (at ∼2900 cm−1) for comparison.
(Color online) Typical photoluminescence curve of prestine MAC6 with time (solid red) at ambient conditions. Raman peak ratio of aromatic stretching mode at ∼1600 cm−1 and CH stretching mode at ∼2900 cm−1 near the ablation threshold (green circles) shows that significantly increased conjugation near the ablation onset. Fluorescence background was subtracted prior to calculating the Raman peak areas. Raman signal was integrated for 10 s.
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