We studied the mechanical properties of a suspended graphene layers which have ripples with stripe pattern, by using an atomic force spectroscopy. The local spring constant of the rippled graphene layer has larger value at concave region and smaller at convex region. The attractive force and pull-off force between a tip and the sample also have larger values at the concave region. A local spring constant mapping on the suspended graphene with ripple was obtained and nonlinear behavior of the force-distance curve was analyzed regarding local deformation of the sample.
The temporally-averaged photovoltages were measured on Cu(In,Ga)Se 2 [CIGS] solar cells under the intermittent light excitation by photo-assisted Kelvin probe force microscopy to evaluated a time constant for photovoltage decay and a contribution ratio r of fast carrier recombination process in the entire recombination processes. The results indicate that the sample with higher Ga content exhibited longer and larger r, from which we have investigated the influences of both the carrier transport across the potential barrier and the carrier separation around the grain boundary on the entire photo-carrier recombination processes.
We applied the scanning probe lithographic technique to a graphite patterning in air and analyzed the patterned sample with the lateral force microscopy and Raman spectroscopy. The local electric field generated from a tip caused either etching or oxidization depending on the electric field intensity in air. We have found that the frictional force between the tip and local oxidized graphite surface was increased remarkably from lateral force analysis. Also, it was found that the graphene layer was peeled from the graphite surface in the etching process, which could be a potential tool as a top-down nano-fabrication process for the graphene nano device without contamination.
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