Cryogenic heavy ion RBS-ERDA depth profiling of ion implanted PET films

Abstract

The analysis of thin films using heavy ions offers some specific advantages over traditional light ion beam analysis techniques. In this work, polyethylene terephthalate (PET) substrate was implanted with 150 keV Ag+-ions at low temperature at fluences of 1.00 x 1016 and 5.00 x 1016 ions/cm2. A newly constructed low temperature chamber equipped with heavy ion Rutherford Backscattering Spectrometry (HI-RBS) and Elastic Recoil Detection Analysis (HI-ERDA) detectors was used for sample characterisation, using 14 MeV 28Si4+-ions at an irradiation fluence of about 2.40 x 1013 ions/cm2. The analyses were carried out at room temperature and with the sample holder cooled to liquid nitrogen temperature. Silicon beam irradiation effects on the PET were then compared at room- and low-temperature measurements. Significant hydrogen loss of about 64 % relative to pristine PET was observed for room-temperature measurements, whereas for low-temperature analyses the hydrogen loss was about 12 %. The significant release of hydrogen atoms from the surface region of the PET was accompanied by a drastic change in the surface layer composition. For room-temperature measurements, there was surface enhancement of the carbon content by about 31 %, while for low-temperature measurements the accumulation was about 9 % compared to the nominal 45 % content in pristine PET.