A Study of Solid CO₂/H₂O and CO₂/CH₃OH by XPS

High quality solid CO₂/H₂O and CO₂/CH₃OH films have been grown on a stainless steel cold-finger using a continuous flow liquid nitrogen system. The solid (or ice) was formed from research grade (99.995% min. purity) isotopic ¹³CO₂ gas, and ultrapure water vapor or methanol vapor. The isotopic ¹³CO₂ gas was used to distinguish it from any background CO₂ gas in the vacuum system. The gases were mixed in a stainless steel prechamber with the pressure monitored using an MKS capacitance manometer. The base pressure in the analysis chamber was less than 5 × 10⁻¹⁰ T prior to deposition and upon gas introduction was inceased, using a precision leak valve, to approximately 2 × 10⁻⁸ T. Films were grown at this pressure for approximately 1 h. Gas purity was monitored using a Balzers Prisma QMS 300 quadrupole mass spectrometer. The nucleated films were characterized using x-ray photoelectron spectroscopy (XPS). The reported spectra include survey and high resolution scans of the major photoelectron peaks.