THERMAL-STABILITY OF THE CARBON CARBON BOND IN ETHYLENE ADSORBED ON SI(100) - AN ISOTOPIC MIXING STUDY

The dominant surface chemical process involving chemisorbed C2H4 on Si(100) is the desorption of the intact C2H4 molecule. Decomposition of C2H4(a) to produce SiC is a minor process on Si(100). By studying the isotopic mixing between 13C2H4 and 12C2H4 to produce 13CH2 = 12CH2, it has been shown that less than 1% isotopic mixing occurs in the temperature range 500- This observation excludes the recombination process 2CH2(a) → C2H4(a) → C2H4(g) as being of importance in C2H4 desorpti from Si(100). In addition, the efficiency, ηSiC, of SiC formation from C2H4 has been carefully remeasured using direct calibration of the Auger spectrometer for adsorbed carbon using C2H4 of known absolute coverage as a standard. We find that ηSic = 3.3 × 10-3 SiC units per C2H4 collision at a Si(100) temperature of 950 K. © 1990.