We present a continuous tip monitoring method during atomic force microscopy imaging based on the use of higher harmonics, which are generated in the repulsive regime as a result of the nonlinear interactions between the cantilever tip and the surface under study. We have applied this method to commercial rectangular microfabricated silicon cantilevers with force constants in the 45 N/m range and fundamental frequencies in the 300-400 kHz range and with tip radii below 10 nm. We have focused in the resonance of the 2nd flexural mode and the 6th harmonic using polystyrene surfaces. The simultaneous acquisition of topographic and higher harmonic images allows a continuous control of the state of the tip. The experimental results have been rationalized with computer simulations taking into account both the cantilever dynamics and the tip-surface interactions.
We present an approach for the creation of guiding patterns to direct the self-assembly of block copolymers. A neutral layer of a brush polymer is directly exposed by electrons, causing the cross-linking of the brush molecules, and thus changing its local affinity. The advantage relies on the achievable resolution and the reduction of the process steps in comparison with deep UV and conventional electron beam lithography, since it avoids the use of a resist. We envision that this method will be highly valuable for the investigation of high-chi directed self-assembly materials and complex guiding pattern designs, where pattern placement and resolution are becoming critical.
The nanomechanical properties of solvent-cast polymer thin films have been investigated using PeakForce™ Quantitative Nanomechanical Mapping. The samples consisted of films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) obtained after the dewetting of toluene solution on a polymeric brush layer. Additionally, we have probed the mechanical properties of poly(styrene-b-methyl methacrylate) block copolymers (BCP) as randomly oriented thin films. The probed films have a critical thickness <50 nm and present features to be resolved <42 nm. The Young’s modulus values obtained through several nanoindentation experiments present a good agreement with previous literature, suggesting that the PeakForce™ technique could be crucial for BCP investigations, e.g., as a predictor of the mechanical stability of the different phases.
We present a novel approach for the creation of guiding patterns to direct the self-assembly of block copolymers. A
neutral layer of a brush polymer is directly exposed by electrons, causing the cross-linking of the brush molecules, and
thus changing its local affinity. The advantage relies on the achievable resolution and the reduction of the process steps
in comparison with deep UV and conventional electron beam lithography, since it avoids the use of a resist. We envision
that this method will be highly valuable for the investigation of novel high-chi DSA materials and complex guiding
pattern designs, where pattern placement and resolution is becoming critical.
The nanomechanical properties of solvent cast polymer thin films have been investigated using PeakForceTM quantitative nanomechanical mapping. The samples consisted in films of polystyrene and poly(methyl methacrylate) obtained after dewetting of toluene solution on a polymeric brush layer. As a second step, we have probed the mechanical properties of Poly(styrenen- methilmethacrylate) (PS-b-PMMA) block co-polymers (BCP) thin films randomly oriented. The measured films has a critical thickness below 50 nm and present features to be resolved of less than 42 nm. Measured surface elastic modulus obtained present a good agreement with previous literature and show how PeakForce technique could be crucial to BCP investigation predicting the mechanical stability of the different phases.
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