LB films of polyimide with promellitic dianhydride (PMDA) and 4

4′-diaminophenylether (ODA) structure were fabricated by so-called “precursor” method

and SiC ultrathin films were obtained by pyrolyzing the polyimide LB films at a high vacuum of 1×10-5 mbar and a temperature of 1000℃．In order to study the mechanism of this pyrolysis process

X-ray photoelectron spectroscopy (XPS) technology was used to study the polyimide LB film and to trace the pyrolysis process of the LB film in-situ．By probing the polyimide LB film from different angles

it was found that in the LB films

the elements were much evenly distributed

the quantitative analysis of the elements was also in very good agreement with the theoretical value．The in-situ trace showed that at about 500℃ the molecules of polyimide decomposed to amorphous carbon；in the meantime

some small molecular weight gases were given out；the remained skeleton C in the LB film began to react with Si from substrate to form SiC at about 670℃．Higher temperature and longer time would be helpful for the reaction of SiC formation to proceed thoroughly．It also found that at lower temperature

the substrates were oxidized to SiOx (x＜2) by the oxygen it absorbed

but at higher temperature

the SiOx was reduced to SiC by the skeleton C in the LB films．Auger Electron Sputting (AES) spectrum indicated that the atoms of C and Si distributed gradiently in the SiC films

suggesting the mutually diffusion mechanism in the SiC formation．