Scanning Probe Microscopy

The design and the control of surface and interface properties play a central role in almost all modern optoelectronic devices. We useScanning Probe Microscopyto investigate the surfaces of functional materials on the nanometer scale. In particular, we are interested in materials for solar cell applications, where the interface between the n-type and p-type semiconductors determines, in many cases, the performance of these resulting devices.

We pay special attention to analyze clean and well-defined surfaces. Consequently, all measurements are performed in a variable temperature ultra-high vacuum STM/AFM system. We do have the possibility to analyze the local density of states of the semiconductor surfaces via scanning tunneling spectroscopy (STS), the electrostatic landscape of the surfaces via Kelvin Probe Force Microscopy (KPFM) and current collection via conductive atomic force microscopy (c-AFM). Additional measurement modes include magnetic force microscopy (MFM) and piezo force microscopy (PFM).

Our current interest is focused on two types of thin film solar cells, namely Cu(In,Ga)Se2 (CIGSe) and hybrid organic inorganic perovskites.  Within the ATTRACT project SUNSPOT we analyze the influence of surface treatments on epitaxial and polycrystalline CIGSe. Furthermore, we will synthesize and characterize the surfaces of hybrid perovskites with SPM.