Growth dynamics of molecular semiconductors studied by time resolved X-ray scattering
by
Stefan Kowarik, Dept. of Physics, Humboldt-Universität zu Berlin
→
Europe/Berlin
Bldg. 25b, room 109
Bldg. 25b, room 109
Description
Molecular semiconductors ("plastic" semiconductors) commonly display polymorphism and complicated growth modes, because the binding forces are weak (v. d. Waals) and the molecular building blocks possess more degrees of freedom (e.g. molecular orientation, conformation) than atomic semiconductors. Therefore X-ray scattering is important for characterizing thin films and achieving high quality device structures.
Real-time X-ray measurements in particular are important for /in-situ, /online process control of growth, annealing, and dewetting. We will present examples of real-time GIXD during growth of the molecule diindenoperylene, which reveals transient structures. Also X-ray growth oscillations (i.e. an oscillating X-ray signal due to crystal growth) are an important characterization technique for the out of plane structure and film roughness. The structural evolution obtained from fits to the growth oscillations agrees with the static, post-growth structure obtained from AFM, and we find a strong correlation between the device performance of an organic field effect transistor (OFET) and the filling factors of molecular layers near the gate. We will discuss how real time X-ray measurements can be used to grow organic heterostructures with molecularly precise interfaces, and will also give an outlook on (real-time) X-ray microscopy for chemically selective characterization of heterostructures.
