ToF-SIMS investigation of the cationization of several lubricant components

Abstract

Cationization of molecular substances results often in the emission of characteristic peak patterns of secondary ions (SI) of these molecular species and is accompanied by matrix-enhanced SI yields. Besides the cationization of molecular overlayers on substrates of periodic table group IB elements, recent especially matrix-enhanced SIMS by physical vapor deposition (PVD) processes of Ag and Au was in the focus of investigations. In this work, selected lubricants components were investigated by ToF-SIMS, using different methods for cationization: (i) substrate cationization with periodic table group IA and IB elements (Cu, Ag, Cs, Au), (ii) cationization by dissolved salts of group IA and IB elements (Li, K, Na, Cu, Ag), and (iii) the in situ PVD by sputtering of group IB element targets (Cu, Ag, Au) by using the pulsed dual source column (DSC) of a ToF-SIMS instrument and thick lubricant layers on silicon wafers positioned in the immediate vicinity of the sputter crater. The Cu- and Ag-cationization of the investigated trimethylol-propane esters TMP(C8/C10) and poly-alpha-olefins (PAO) were possible with all specified methods, whereas only the esters were cationized also by alkaline elements (Li, Na, K, Cs). Au-cationization products were only observed for volatile PAO components that have deposited on the fresh cleaned surface of the sputter crater bottom of the Au-target.