Preparation and electrical properties of cobalt-platinum nanoparticle monolayers deposited by the Langmuir-Blodgett technique

The Langmuir-Blodgett technique was utilized and optimized to produce closed monolayers of cobalt-platinum nanoparticles over vast areas. It is shown that sample preparation, "dipping angle", and subphase type have a strong impact on the quality of the produced films. The amount of ligands on the nanoparticles surface must be minimized, the dipping angle must be around 105$^{\circ}$, while the glycol subphase is necessary to obtain nanoparticle monolayers. The achieved films were characterized by scanning electron microscopy (SEM) and grazing incidence x-ray scattering (GISAXS). The electrical properties of the deposited films were studied by direct current (DC) measurements showing a discrepancy to the variable range hopping transport from the granular metal model, and favoring the simple thermal activated charge transport. SEM, GISAXS as well as DC measurements confirm a narrow size distribution and high ordering of the deposited films.