The effect of ion energy on the chemistry of air-aged polymer films grown from the hyperthermal polyatomic ion Si2OMe5+

Thin polymer films have been grown from hyperthermal [m/z 147, Si2OMe5+] io ns, using ion energies of 15, 25, 50, and 100 eV. X-ray photoelectron spect roscopy (XPS) and secondary ion mass spectrometry (SIMS) analyses were unde rtaken of the air-aged polymer films. The SMS and XPS of samples deposited from ion beams of 15 and 25 eV energies (15 and 25 eV polymers) are remarka bly similar, but different in a number of respects to those of the 50 and 1 00 eV polymers. The positive SMS of the lower energy polymers resemble clos ely that of the linear polymer polydimethyl siloxane (PDMS). However, the X PS of these polymers reveal a range of silicon binding environments [Si-C/H , Si(-O-1) Si(-O-2) (Si-O-3) and Si(-O-4)], whilst the 'monomer ion' (m/z 1 47) has only one, Si(-O-1). Although the positive ion SIMS of the 50 and 10 0 eV polymers contain 'PDMS-like' fragments (m/z 147, 207, 221, 281), these ions are much reduced in intensity (cf. 15 and 25 eV), and we postulate th at the extent of cross-linking is much higher in these polymers. In fitting the XPS of these polymers it was necessary to include an additional compon ent peak for Si(-Si-3). These polymers are compared with a low power plasma polymer of HMDSO. The polymers grown from the 15 and 25 eV ions are remark ably similar to the plasma polymer in terms of their molecular structure an d their surface chemistry. (C) 2001 Elsevier Science BY All rights reserved .