Multiple regimes of operation in bimodal AFM: understanding the energy of cantilever eigenmodes

• Daniel Kiracofe,
• Arvind Raman and
• Dalia Yablon

Beilstein J. Nanotechnol. 2013, 4, 385–393, doi:10.3762/bjnano.4.45

• property contrast with high resolution. Bimodal AFM, where two eigenmodes are simultaneously excited, confers significant advantages over conventional single-frequency tapping mode AFM due to its ability to provide contrast between regions with different material properties under gentle imaging conditions

• . Bimodal AFM traditionally uses the first two eigenmodes of the AFM cantilever. In this work, the authors explore the use of higher eigenmodes in bimodal AFM (e.g., exciting the first and fourth eigenmodes). It is found that such operation leads to interesting contrast reversals compared to traditional

• bimodal AFM. A series of experiments and numerical simulations shows that the primary cause of the contrast reversals is not the choice of eigenmode itself (e.g., second versus fourth), but rather the relative kinetic energy between the higher eigenmode and the first eigenmode. This leads to the

Bimodal atomic force microscopy driving the higher eigenmode in frequency-modulation mode: Implementation, advantages, disadvantages and comparison to the open-loop case

• Daniel Ebeling and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2013, 4, 198–207, doi:10.3762/bjnano.4.20

• fundamental eigenmode is driven by using the amplitude-modulation technique (AM-AFM) while a higher eigenmode is driven by using either the constant-excitation or the constant-amplitude variant of the frequency-modulation (FM-AFM) technique. We also offer a comparison to the original bimodal AFM method, in

• 2004 Garcia and co-workers [2] reported on computational simulations of a bimodal AFM technique for the simultaneous imaging of topography and mapping of compositional contrast across the sample. Within their method the fundamental cantilever eigenmode was used to acquire the sample topography through

• -parallel relationship between phase and frequency can be easily observed in a trimodal experiment in which one higher eigenmode is driven in OL and another one is driven in FM [12][13], or in separate bimodal experiments conducted in AM-OL or AM-FM [7]. Figure 3 shows a comparison of bimodal AFM

Repulsive bimodal atomic force microscopy on polymers

• Alexander M. Gigler,
• Christian Dietz,
• Maximilian Baumann,
• Nicolás F. Martinez,
• Ricardo García and
• Robert W. Stark

Beilstein J. Nanotechnol. 2012, 3, 456–463, doi:10.3762/bjnano.3.52

• magnitude smaller than the first two fundamental eigenmodes. Thus, repulsive bimodal imaging of polymer surfaces yields a good signal quality for amplitude ratios smaller than A01/A02 = 10:1 without affecting the topography feedback. Keywords: bimodal AFM imaging; diblock copolymer; polybutadiene

• ., Santa Barbara, CA) extended with an external setup for bimodal AFM [7][8]. The system was equipped with a Signal Access Module and special circuitry to access the deflection signals directly at the segmented photodiode, as shown in Figure 1. A digital function generator (33220A; Agilent Technologies Inc

• , Germany) with a nominal fundamental resonance of 130 kHz and a nominal flexural stiffness of 30 N/m. A 60 nm thick film of SB diblock copolymer (MW(PS) = 13600 g/mol; MW(PB) = 33700 g/mol) was prepared as a test specimen for bimodal AFM. SB is a diblock copolymer with a polydispersity of Mw/Mn = 1.03

Theoretical study of the frequency shift in bimodal FM-AFM by fractional calculus

• Elena T. Herruzo and
• Ricardo Garcia

Beilstein J. Nanotechnol. 2012, 3, 198–206, doi:10.3762/bjnano.3.22

• Lennard-Jones and Derjaguin–Muller–Toporov forces. Keywords: AFM; atomic force microscopy; bimodal AFM; frequency shift; integral calculus applications; Introduction Since the invention of the atomic force microscope (AFM) [1], numerous AFM studies have been pursued in order to extract information from

• modulus of samples in air [14] and liquids [29][30][31]. Bimodal AFM [32][33] is a force-microscopy method that allows quantitative mapping of the sample properties (Figure 1). Bimodal AFM operates by exciting simultaneously the cantilever at its first and second flexural resonances. The technique

• and dissipation of the second mode in bimodal FM-AFM. Experimental measurements have shown the ability of bimodal AFM to measure a variety of interactions, from electrostatic to magnetic or mechanical, both in ultrahigh vacuum [36][37][38], air [33][34][39][40][41] and liquids [15][18][19