Technical note: Characterization of gold coated ceramics by radiofrequency pulsed glow discharge – time of flight mass spectrometry

Abstract

Although it is well known that glow discharge (GD) spectrometry can be used for characterization of both conductive and non-conductive materials, its application to insulators is limited and can be challenging when aiming at the analysis of thick samples. Voltage drop across the material can lead to low power deposition and so to non-efficient sputtering. In this article successful depth profile characterization studies on 6 mm thick ceramic samples coated with a thin (in the nm range) gold layer by means of a commercially available radiofrequency pulsed GD (RF-PGD) coupled time of flight mass spectrometry (RF-PGD-TOFMS) instrument are presented. Careful optimization of the operating conditions was required to achieve proper sputtering of the insulator substrate. 30 W applied rf power, 95 Pa pressure in the GD chamber and a pulse width of 500 μs with a period of 1.49 ms were selected. Characterization of a set of industrially prepared ceramic samples under different conditions was carried out. To overcome problems related to the roughness of the samples, estimation of sample thickness was achieved with an alternative approach based on the use of flat glasses with known Au layer thicknesses. Results of the investigated ceramic samples have shown Au layer thicknesses ranging between 20 and 120 nm. Moreover, screening of other metallic elements within the Au thin coating was carried out, and the presence of Rh, Bi, Pt, Ir and Pd in the Au layer was observed.