Ion-beam analysis of phospholipid thin films deposited on c-Si

We report the feasibility of studying thin phospholipid films (viz. cardiolipin) using energetic ion-beams. We have deposited thin films of cardiolipin, on crystalline Si(100) substrates by spin coating technique. Stability of these films under high vacuum has been tested by weight loss measurements. Films have been characterized by Rutherford backscattering spectrometry (RBS), ion channeling and elastic recoil detection analysis (ERDA) using He+ ion-beam. RES analysis provides an accurate determination of C, O and P contents of the films which matches well with the nominal composition of cardiolipin. This indicates that the amount of C, O and P do not alter under He+ bombardment during measurements. On the other hand, hydrogen depth profiling by ERDA exhibits H loss from the Lipid films during measurements. This has been interpreted on the basis of bond-breaking due to energy deposition by He+ ions followed by formation and escape of molecular hydrogen. These changes have been corroborated by Fourier transform infrared (FTIR) spectroscopy. (C) 1999 Elsevier Science B.V. All rights reserved.