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O'Gorman, Colm
Preferred name
O'Gorman, Colm
Official Name
O'Gorman, Colm
Research Output
Now showing 1 - 3 of 3
- PublicationThe effect of viewing angle on the spectral behavior of a Gd plasma source near 6.7 nm(American Institute of Physics, 2012)
; ; ; ; ; ; ; ; ; ; We have demonstrated the effect of viewing angle on the extreme ultraviolet (EUV) emission spectra of gadolinium (Gd) near 6.7 nm. The spectra are shown to have a strong dependence on viewing angle when produced with a laser pulse duration of 10 ns, which may be attributed to absorption by low ion stages of Gd and an angular variation in the ion distribution. Absorption effects are less pronounced at a 150-ps pulse duration due to reduced opacity resulting from plasma expansion. Thus for evaluating source intensity it is necessary to allow for variation with both viewing angle and target orientation.Scopus© Citations 18 568 - PublicationScaling of laser produced plasma UTA emission down to 3 nm for next generation lithography and short wavelength imaging(Society of Photo-optical Instrumentation Engineers, 2011-08-22)
; ; ; ; ; ; ; ; ; ; ; An engineering prototype high average power 13.5-nm source has been shipped to semiconductor facilities to permit the commencement of high volume production at a 100 W power level in 2011. In this source, UTA (unresolved transition array) emission of highly ionized Sn is optimized for high conversion efficiency and full recovery of the injected fuel is realized through ion deflection in a magnetic field. By use of a low-density target, satellite emission is suppressed and full ionization attained with short pulse CO2 laser irradiation. The UTA is scalable to shorter wavelengths, and Gd is shown to have similar conversion efficiency to Sn (13.5 nm) at a higher plasma temperature, with a narrow spectrum centered at 6.7 nm, where a 70% reflectivity mirror is anticipated. Optimization of short pulse CO2 laser irradiation is studied, and further extension of the same method is discussed, to realize 100 W average power down to a wavelength of 3 nmScopus© Citations 9 674 - PublicationOptimizing conversion efficiency and reducing ion energy in a laser-produced Gd plasma(American Institute of Physics, 2012)
; ; ; ; ; ; ; ; ; ; We have demonstrated an efficient extreme ultraviolet (EUV) source at 6.7 nm by irradiating Gd targets with 0.8 and 1.06 μm laser pulses of 140 fs to 10 ns duration. Maximum conversion efficiency of 0.4% was observed within a 0.6% bandwidth. A Faraday cup observed ion yield and time of flight signals for ions from plasmas generated by each laser. Ion kinetic energy was lower for shorter pulse durations, which yielded higher electron temperatures required for efficient EUV emission, due to higher laser intensity. Picosecond laser pulses were found to be the best suited to 6.7 nm EUV source generation.Scopus© Citations 47 718