Pulsed radiofrequency glow discharge time of flight mass spectrometer for the direct analysis of bulk and thin coated glasses

Abstract

Direct solid analysis of bulk and thin coated glasses by pulsed radiofrequency (rf) glow discharge timeof-flight mass spectrometry (GD-TOFMS) is investigated. Modulated low pressure plasma created by pulsed-rf-GD has been coupled to a fast TOFMS in order to obtain complete mass spectra information from the different GD pulse domains (pre-peak, plateau and afterglow). In particular, it was observed that the analytes show the highest atomic ion signals in the afterglow region some hundred microseconds after the maximum of the Ar ion signal. However, it should be highlighted that the analyte ions exhibited their peak maxima at different delay times, depending on the element, after the end of the GD pulse. Such ion signal delays have been measured for different selected isotopes, covering a mass spectrum from light to heavy isotopes at different conditions of pressure and applied power. The results showed that ion signal delays are influenced by both the isotope mass and the pressure of the GD. Furthermore, GD operating conditions (pressure and applied power) were optimised in terms of sensitivity, using a bulk glass certified reference material (NIST 1411). The best analytical performance was observed at low pressure (150-200 Pa) and high applied power (135 W). Moreover, different pulse GD duty cycles (relationship between pulse duration and pulse period) were investigated. An optimum value of 50-65% duty-cycle was selected considering the signal stability and the signal intensity. The previously optimized pulsed-rf-GD-TOFMS system was then evaluated for qualitative in-depth profile analysis of thin coatings deposited onto thick glass substrates. High depth resolution (nm range), comparable to that obtained using rf-GD-OES was achieved. However, the observed depth resolution using the ToF-SIMS system is still superior. In this sense, analytical figures of merit observed in our pulsed-rf-GD-TOFMS demonstrate its great analytical potential for high depth resolution analysis of coated glasses.

A comparison of non-pulsed radiofrequency and pulsed radiofrequency glow discharge orthogonal time-of-flight mass spectrometry for analytical purposes

“…1 by the applied forward power or pressure. 9 Further fundamental studies using different matrix samples are needed to fully understand these delays and shape variations.…”

“…Ar adducts) are minimal. 16 Moreover, pulsed RFGD-TOFMS is particularly advantageous for the analysis of heat sensitive materials, such as glasses 9 or polymers.…”

Detection of negative ions in glow discharge mass spectrometry for analysis of solid specimens

“…Progress in the development of instrumentation utilizing pulsed RF glow discharges has enabled the analysis of both electrically conducting and non-conducting materials. Muñiz et al have demonstrated the analytical capabilities of a pulsed RF-GD-TOFMS system for analysis of multi-nanolayers deposited on glass [9]. Recent advances in GD-TOFMS have been focused on important, new analytical applications, i.e., rapid molecular depth profiling of polymers [10].…”

Signal Enhancement with Stacked Magnets for High-Resolution Radio Frequency Glow Discharge Mass Spectrometry

“…1 Particularly, the rf-GD-MS has offered efficient depth profile analysis of different materials, such as glass, ceramics and new composite materials, thus widening its applications. [2][3][4][5][6][7][8][9][10][11][12][13] Generally, the principles of rf glow discharge is similar to direct current glow discharge in many respects. However, as an AC potential is applied in an rf-GD process, electrical insulating samples can be effectively sputtered.…”