Using Physical Vapor Deposition to Produce Structured Glasses - from Isotropic to Liquid-Crystalline Order

While liquid-cooled glasses are usually isotropic, glasses can be anisotropic and this is typically the case for glasses produced by physical vapor deposition. For organic electronics, glass anisotropy can be manipulated to increase device efficiency. We have shown that the substrate temperature during deposition plays a key role in controlling the anisotropy of vapor-deposited glasses. For hole transport materials such as TPD, mildly anisotropic glasses in which molecules have a tendency to either “lie down” or “stand up” can be prepared, as indicated by ellipsometry and grazing incidence x-ray scattering. For the smectic mesogen itraconazole, a highly ordered smectic monodomain is obtained directly by deposition just below Tg; everywhere in the sample the smectic planes are parallel to the free surface. For discotic mesogens, glasses with highly ordered columnar structures are obtained directly by deposition with substrate temperature allowing a switch between in-plane and out-of-plane columns. Remarkably, molecules with no known liquid-crystalline states can also form glasses with substantial liquid-crystalline order. These developments present significant opportunities to design new anisotropic solids for organic electronics and optoelectronics.