Wl. Wu et al., DENSITY PROFILE OF SPIN CAST POLYMETHYLMETHACRYLATE THIN-FILMS, Journal of polymer science. Part B, Polymer physics, 32(15), 1994, pp. 2475-2480
The density profiles of polymethylmethacrylate ( PMMA) thin films on s
ilicon (111) single crystal wafers were investigated via neutron refle
ctivity measurements. Films were prepared by spin casting PMMA onto si
licon wafers from o-xylene solution followed by annealing under vacuum
at 90 degrees C for 5 h. A similar to 45 A thick layer at the free po
lymer surface was observed in the as-prepared samples that has a densi
ty about half the value of bulk PMMA. After heating above 110 degrees
C, this diffuse layer disappeared and the thin film density profile wa
s transformed to one with a sharp free polymer surface. This transitio
n was found to be irreversible. (C) 1994 John Wiley and Sons, Inc.