Observation of Filamentous Nanostructures in Organic‐Inorganic Composite Thin Films Deposited by Co‐Evaporation

Abstract

AbstractNanostructures are important for a wide area of applications, but are very often difficult to fabricate. A novel and basic approach for controlled nanofilament growth in an organic/inorganic composite material is demonstrated. Thin films of MoO3‐doped 4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl are grown via vacuum sublimation and analyzed using advanced electron microscopy and spectroscopy techniques. Using electron spectroscopic imaging in the core‐loss and low‐loss regime, MoO3 agglomerations are identified for different doping concentrations. A 3D reconstruction of the thin film yielded by electron tomography reveals a filamentous structure of MoO3 within the organic matrix. These filaments are preferentially oriented along the growth direction and are only a few nanometers in diameter. Furthermore, control of the filament growth is possible by changing the substrate temperature because for composites grown on substrates cooled to 120 K MoO3 agglomeration cannot be detected.