ELSEVIER Applied Surface Science 96-98 (1996) 227-232 Energy-dispersive mass spectrometry of high energy ions generated during KrF excimer and frequency-doubled Nd:YAG laser ablation of metals Glenn C. Tyrrell * , Luigi G. Coccia, Tim H. York, Ian W. Boyd Department of Elecrronic and Electrical Engineering, University College London, Torrington Place, London, WClE 7.1EjUK Received 22 May 1995 Abstract The accurate measurement of high energy ions (up to 500 eV> produced during the laser ablation process has been investigated using energy-dispersive mass spectrometry. A comparison between 5 J cm -’ ablation of metals, such as Cu and Fe, by 532 nm Nd:YAG and 248 nm excimer laser irradiation shows the effect of pulse duration on the kinetic energy distributions of the generated ions. The propagation of Fe + ions within the laser produced plasma through high vacuum shows significant modification due to ion acceleration processes with increasing distance from the target. Significantly, no attenuation of detected signal is observed with increased target-spectrometer distance, thus indicating a highly forward-peaked distribution of high energy ions. 1. Introduction Pulsed laser deposition (PLD) using fluences in the range I-10 J cm-’ is well established as an important materials development technique for the fabrication of complex ceramic, metal and metal oxide thin films for electronic applications [l]. In general, these films are deposited either in vacuum or in a modest partial pressure of a background gas, e.g. O,, N,, Ar, etc. Thus, the gas may provide either a reactive or an inert buffer to the laser produced plasma (LPP). In each case significant partial pressures (> 5 X 10m2 mbar) lead to colli- sional processes between the LPP and the interven- ing gas. This is a clear example of modifying the * Corresponding author. energetics of the nascent ablation plasma by gas dynamic phenomena. However, in vacuum the ki- netic energy distributions (KED) associated with ions in the plasma in vacuum are assumed not to change significantly after the initial acceleration process, compared to the case in high partial pressures. The phenomenon of high energy ions produced in the laser ablation process is of considerable interest. This paper discusses the use of an energy-dispersive mass spectrometric (ED-MS) technique using an electrostatic cylindrical mirror analyser (CMAl/quadntpole mass spectrometer (QMS) com- bination. The presence of ions and neutrals with energies of tens of eV are known to be beneficial to the densification of growing films [2], but ions with higher energies (> 100 eV> can result in significant alterations to the substrate such as sputtering of the growing surface, amorphisation, intermixing of lay- 0169.4332/96/$1.5.00 0 1996 Elsevier Science B.V. All rights reserved S S DI 0169-4332(95)00484-X