Analysis of Strontium Titanate by Helium Glow-Discharge Mass Spectrometry Using Dummy Cathode

A dummy cathode brings about the sputtering of non-conductive ceramics, like SrTiO3 in a helium glow discharge ion source. This study addresses that phenomenon. A dummy cathode with an outer diameter of 20 mm and an aperture diameter of 5 mm was prepared from a Ta sheet using electrical-discharge machining. A Ta plate with a 10 mm aperture diameter was used as an anode plate. The optimal electric discharge parameter was obtained at a He flow rate of 10 mL/min and a discharge voltage of 2 kV. The discharge current was about 2 mA. The ion intensities of Ti, Sr, and Ta reached 10(-10) A level in peak-area integrated intensity at a mass resolution of 4000. The ion intensity the ratios to Ta, Ti : Ta and Sr: Ta, were both 0.26: 1. Under these conditions, five data sets were acquired a after pre-discharge for 60 min, which proved that a stable glow discharge continued for 170 min or longer. The relative sensitivity factors of O and Sr to Ti, RSFO,Ti, and RSFSr,Ti, were obtained using the measurement of a SrTiO3 single crystal; they were, respectively, 0.179 and 2.099.