Investigating the fundamentals of molecular depth profiling using strong-field photoionization of sputtered neutrals

Molecular depth profiling of model organic thin films were performed using a 40 keV C-60(+) cluster ion source in concert with TOF-SIMS. Strong-field photoionization of intact neutral molecules sputtered by 40 keV C-60(+) primary ions was used to analyze changes in the chemical environment of the guanine thin films as a function of ion fluence. Direct comparison of the secondary ion and neutral components of the molecular depth profiles yields valuable information about chemical damage accumulation as well as changes in the molecular ionization probability. An analytical protocol based on the erosion dynamics model is developed and evaluated using guanine and trehalose molecular secondary ion signals with and without comparable laser photoionization data. Copyright (C) 2010 John Wiley & Sons, Ltd.