Electron spin resonance studies of evaporated carbon films

✍ Scribed by I.S. McLintock; J.C. Orr

• Publisher: Elsevier Science
• Year: 1967
• Tongue: English
• Weight: 916 KB
• Volume: 5
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(67)90011-5

✦ Synopsis

Carbon films deposited on Pyrex, silica and alumina substrates have free spin concentrations similar to those found for chars. The results of heat treatment show that a maximum in the spin concentration occurs at a heat treatment temperature of about 150°C and that when silica and alumina substrates are employed a second maximum in the spin concentration occurs at 500°C. The second spin production process is considered to originate in the evolution of water and hydrogen from the substrate and to lead to a high concentration of spins at the surface. Line width and line shape analysis suggests that considerable exchange narrowing occurs in films. Activation energies for spin production and destruction over the temperature range 55-314°C increase with extent of reaction. The original spin centres are taken to be unsatisfied sigma valencies situated on the periphery of carbon aggregates in strained regions of the film. The spin destruction process suggests that such centres link up with others by temperature induced release of strain.