High-density stable glasses formed on soft substrates

High Density Two-Component Glasses of Organic Semiconductors Prepared by Physical Vapor Deposition

“…These properties can be explained by the surface equilibration mechanism, which is based on high molecular mobility at the free surface relative to the bulk. ,,, Consistent with this mechanism, the density of a vapor-deposited low molecular weight system, ethylbenzene, was shown to approach the density of the ideal glass . Fakhraai and co-workers have recently reported that a vapor-deposited glass of TPD can have significantly high density when it is ultrathin (thinner than 50 nm) or deposited on a soft substrate . Furthermore, the structure of molecules in the as-deposited glasses can be anisotropic whereas liquid-cooled glasses are usually isotropic. ,,,,, Dalal et al demonstrated that three linear-shaped organic semiconductors (NPD, TPD and DSA-Ph) have tunable molecular orientation depending on the ratio of the substrate temperature ( T sub ) to the glass transition temperature ( T g ) during deposition .…”

“…28 Fakhraai and co-workers have recently reported that a vapor-deposited glass of TPD can have significantly high density when it is ultrathin (thinner than 50 nm) 10 or deposited on a soft substrate. 29 Furthermore, the structure of molecules in the as-deposited glasses can be anisotropic whereas liquid-cooled glasses are usually isotropic. 1,2,9,12,30,31 Dalal et al demonstrated that three linear-shaped organic semiconductors (NPD, TPD and DSA-Ph) have tunable molecular orientation depending on the ratio of the substrate temperature (T sub ) to the glass transition temperature (T g ) during deposition.…”