Material transport regimes and mechanisms for growth of molecular organic thin films using low-pressure organic vapor phase deposition

We determine the physical mechanisms controlling the growth of amorphous organic thin films by the process of low-pressure organic vapor phase deposition (LP-OVPD). In LP-OVPD, multiple host and dopant molecular sources are introduced into a hot wall reactor via several injection barrels using an inert carrier gas, allowing for controlled film growth rates exceeding 10 Å/s. The temperature and carrier flow rate for each source can be independently regulated, allowing considerable control over dopant concentration, deposition rate, and thickness uniformity of the thin films. The rate of film deposition is limited either by the rate of condensation on the substrate or by the rate of supply from the source. The source-limited regime can be further classified into equilibrium or kinetically limited evaporation, coupled to convection- or diffusion-limited deposition. Models are developed to relate the rate of film growth to source and substrate temperature, and carrier gas flow rate. These models characterize and predict the performance of the LP-OVPD system used to grow high performance organic light emitting devices.