Analyze Monolayers and Thin Films with AFM
Atomic force microscopy is ideally suited for imaging, measuring and analyzing monolayers, bilayers or molecules on the nanoscale. Self-assembled monolayers can be evaluated using the topography signal in oscillating mode. Phases and molecular orientation can be evaluated for monolayers or thin films.
Nano-Observer AFM topography image of C36 molecules on HOPG, scan size 250 nm
Versatility, the ability to image a wide range of samples, is an advantage of oscillating mode. Sample and tip damage is minimized using oscillating mode. Phase imaging can reveal material differences where there is no topographic distinction.
For electrical characterization, an advanced mode like Kelvin probe force microscopy (KFM) using the potential signal can show monolayers and bilayers that are not evident in a topographic image. KFM measures the contact potential difference between a conductive tip and substrate potential. Electrical characterization of semiconductors, solar cells, and biomolecules on the nanoscale are examples of KFM applications.
As a material of interest for nanoscale devices, graphene on SiC requires nanoscale characterization. Graphene uniformity is key to product performance. Due to substrate effects and interfacial oxide, graphene growth often results in a non-uniform film. Monolayers and bilayers of graphene can be imaged using the potential signal with KFM.
Nano-Observer AFM image of graphene on SiC using KFM potential signal, scan size 7 microns
In this potential signal image using KFM, monolayers of graphene are orange. Bilayers of graphene are yellow. For comparison, the topography signal is shown below. The potential signal of KFM mode provides the nanoscale electrical characterization needed for graphene layers on SiC.
Nano-Observer AFM topography image of graphene on SiC, scan size 7 microns