Tuning the phase structure of multicomponent PVD glasses by controlling surface mobility

Physical vapor deposition (PVD) leverages the mobility at the free surface of a glass to create glassy films with exceptional properties beyond those of a liquid-cooled glass. As PVD continues, subsequent material locks the surface molecules into the bulk glass. Deposition conditions that affect the mobility at the surface control the structure of the PVD glass. We expect surface mobility in multicomponent PVD glasses to affect their structure and morphology. Here, we deposit two organic semiconductors, Alq3 and DSA-Ph, into multicomponent films. Using GIWAXS and GISAXS, we find that we can control the distribution of each material within the PVD glass by controlling the deposition conditions. A multicomponent glass of a set composition can be prepared as either a well-mixed glass or with phase separated regions rich with either Alq3 or DSA-Ph. When Alq3 and DSA-Ph are deposited in alternating small amounts, we can create either well-defined layers of each material or 3D nanodomains within the glass. We hypothesize that 3D Alq3/DSA-Ph nanodomains are created if a small amount of one material is not able to wet a film before the second material is deposited. This kinetically traps the structure of the organic islands formed on the substrate in the first monolayers of deposition.