Ultramicrosensors based on transition metal hexacyanoferrates for scanning electrochemical microscopy

• Maria A. Komkova,
• Angelika Holzinger,
• Andreas Hartmann,
• Alexei R. Khokhlov,
• Christine Kranz,
• Arkady A. Karyakin and
• Oleg G. Voronin

Beilstein J. Nanotechnol. 2013, 4, 649–654, doi:10.3762/bjnano.4.72

• . The microelectrode modified by metal cyanoferrate was positioned in close proximity to the hydrogen peroxide generating UME in feedback mode recording the Faraday current of the Au microelectrode during the approach of the modified electrode. Prior to the approach curve, the electrodes were positioned

• centered to each other using an optical microscope. The non-biased modified UME was then approached to the Au microelectrode while the feedback current at the Au UME was recorded in 10 mM ferrocyanide/0.1 M KCl. A negative feedback signal was obtained due to the hindered diffusion of ferrocyanide towards

Apertureless scanning near-field optical microscopy of sparsely labeled tobacco mosaic viruses and the intermediate filament desmin

• Alexander Harder,
• Mareike Dieding,
• Volker Walhorn,
• Sven Degenhard,
• Andreas Brodehl,
• Christina Wege,
• Hendrik Milting and
• Dario Anselmetti

Beilstein J. Nanotechnol. 2013, 4, 510–516, doi:10.3762/bjnano.4.60

• . Furthermore, the distance-control feedback loop of the probe can be used to gain topographical information as it is done in atomic force microscopy (AFM). Thus, SNOM generally allows the acquisition of both optical and topographical information. Various conceptual approaches have been reported: In fiber SNOM

Kelvin probe force microscopy of nanocrystalline TiO₂ photoelectrodes

• Alex Henning,
• Gino Günzburger,
• Res Jöhr,
• Yossi Rosenwaks,
• Biljana Bozic-Weber,
• Catherine E. Housecroft,
• Edwin C. Constable,
• Ernst Meyer and
• Thilo Glatzel

Beilstein J. Nanotechnol. 2013, 4, 418–428, doi:10.3762/bjnano.4.49

• using a bias voltage of Vdc = 0 V applied to the tip. The cantilever oscillation amplitude was kept constant by a feedback controller at a setpoint, Asp, of 20 nm rms that was pre adjusted to 75% of the free vibrational amplitude, A0 = 27 nm rms. The second scan was performed 20 nm above the previously

• electrostatic force, Fes, was phase-adjusted and retrieved with a lock-in amplifier and subsequently nullified by the applied dc voltage in the Kelvin feedback. Cantilever bending and vibration were optically detected with an infrared laser (λ = 1300 nm, 1 mW, spot size 50 × 50 μm2) and a four-quadrant

Ni nanocrystals on HOPG(0001): A scanning tunnelling microscope study

• Michael Marz,
• Keisuke Sagisaka and
• Daisuke Fujita

Beilstein J. Nanotechnol. 2013, 4, 406–417, doi:10.3762/bjnano.4.48

• attractive force between tip and cluster overcomes the adhesive force of the Ni nanocrystal on the HOPG surface. For this purpose, the tip was first stabilized above the center of the targeted cluster, and then the current setpoint was increased to a value up to 10 nA while the z-feedback was kept enabled

• installed to enhance the resolution) was gradually decreased with closed z-feedback loop. Since we used small bias values, we can assume that the distance depends linearly on the voltage. As soon as a jump in the current or z-feedback signal was observed, the bias was gradually increased again. Afterwards

• , the usual tunnelling conditions were readjusted (V = 1.0 V, I = 0.2 nA), and the outcome of the pick-up attempt was checked with a topographic scan. In roughly 50% of the attempts the pick-up was successful. We point out that an instability in the z-feedback and current signal is always observed in a

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

• Figure 4c and Figure 4d, which is exactly the trend noted in the experiments in Figure 3. To further explore this phenomenon, we perform a simulation in which the cantilever is tapping on a surface with the normal feedback controller on while the second eigenmode drive amplitude (and hence second

• bistability by using frequency modulation, phase modulation or other newer feedback control schemes, such as drive modulation. From a theoretical point of view, more research is needed to understand the nature of the different states and exactly why the contrast should reverse. The fact that there is no

• the experimental observations of Figure 2. Further, comparing (c) versus (d), drops as A2,init is raised. This matches the experimental observation in Figure 3. A simulation in which the second eigenmode drive amplitude is swept up and then down continuously. The feedback controller remains active so

Polynomial force approximations and multifrequency atomic force microscopy

• Daniel Platz,
• Daniel Forchheimer,
• Erik A. Tholén and
• David B. Haviland

Beilstein J. Nanotechnol. 2013, 4, 352–360, doi:10.3762/bjnano.4.41

• complicated multifrequency tip motion. With spectral data, certain points on the tip–surface force curve will receive greater weight if the tip spends more time at these positions. On the FI(A) and FQ(A) curves the weight at each amplitude can be controlled by design. Furthermore, distortions due to feedback

Micro- and nanoscale electrical characterization of large-area graphene transferred to functional substrates

• Gabriele Fisichella,
• Salvatore Di Franco,
• Patrick Fiorenza,
• Raffaella Lo Nigro,
• Fabrizio Roccaforte,
• Cristina Tudisco,
• Guido G. Condorelli,
• Nicolò Piluso,
• Noemi Spartà,
• Stella Lo Verso,
• Corrado Accardi,
• Cristina Tringali,
• Sebastiano Ravesi and
• Filippo Giannazzo

Beilstein J. Nanotechnol. 2013, 4, 234–242, doi:10.3762/bjnano.4.24

• . The torsion amplitude is used as the feedback signal to measure surface morphology. A dc bias was applied to a macroscopic metal contact deposited onto graphene, and the current locally injected from the nanometric conductive tip into graphene was probed by a high sensitivity (fA) current sensor

Photoresponse from single upright-standing ZnO nanorods explored by photoconductive AFM

• Igor Beinik,
• Markus Kratzer,
• Astrid Wachauer,
• Lin Wang,
• Yuri P. Piryatinski,
• Gerhard Brauer,
• Xin Yi Chen,
• Yuk Fan Hsu,
• Aleksandra B. Djurišić and
• Christian Teichert

Beilstein J. Nanotechnol. 2013, 4, 208–217, doi:10.3762/bjnano.4.21

• collimating lenses. A calibration curve, which accounts for both the transmittance of the optical system and the emission spectrum of the light source, was recorded and used for the correction of the photocurrent spectra. The illumination from the AFM feedback laser diode, which has a wavelength of ≈850 nm

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

• the amplitude-modulation (AM) scheme while the second eigenmode was driven with a much smaller amplitude in open loop (OL, that is, only the first mode amplitude signal was used to control the tip–sample distance feedback loop. The second eigenmode drive signal had a constant amplitude and frequency

• ]) or it can provide a signal with variable drive amplitude to maintain a constant oscillation amplitude of the cantilever eigenmode (accordingly denoted as constant amplitude (CA) mode [9]). The latter case is internally realized by running an additional feedback loop that controls the oscillation

• tip–sample-distance feedback loop. These transient times scale as 2Q/ω0, with Q being the quality factor and ω0 the natural frequency [22]. Clearly, imaging becomes impractical when Q increases significantly (as in vacuum operations). In FM-AFM, this drawback is overcome by using the frequency shift

High-resolution dynamic atomic force microscopy in liquids with different feedback architectures

• John Melcher,
• David Martínez-Martín,
• Miriam Jaafar,
• Julio Gómez-Herrero and
• Arvind Raman

Beilstein J. Nanotechnol. 2013, 4, 153–163, doi:10.3762/bjnano.4.15

• forces can be remarkable similar. Furthermore, the reduction in noncontact forces and quality factors in liquids diminishes the role of feedback control in achieving high-resolution images. The theoretical findings are supported by atomic-resolution images of mica in water acquired with AM, FM and DAM

• of imaging resolution and the role of feedback control in dAFM. Prior efforts to analyze imaging resolution in dAFM have typically focused on the small-amplitude limit in order to establish a relationship between various noise sources in the experimental setup and the minimum detectable gradient of

• the tip–sample force [1][4][8][9]. However, the optimal imaging amplitude in FM has also been considered [10]. The role of feedback control in dAFM and its stability have been studied largely by using numerical simulations to solve complex systems of nonlinear, integro-differential equations governing

Effect of normal load and roughness on the nanoscale friction coefficient in the elastic and plastic contact regime

• Aditya Kumar,
• Thorsten Staedler and
• Xin Jiang

Beilstein J. Nanotechnol. 2013, 4, 66–71, doi:10.3762/bjnano.4.7

• detailed information about surface topography and surface roughness. The samples were imaged with commercial tips featuring a nominal tip radius of 10 nm in a feedback-controlled mode on all three axes. Five 8 × 8 μm2 images with a pixel resolution of 512 × 512 were taken at different surface positions on

Interpreting motion and force for narrow-band intermodulation atomic force microscopy

• Daniel Platz,
• Daniel Forchheimer,
• Erik A. Tholén and
• David B. Haviland

Beilstein J. Nanotechnol. 2013, 4, 45–56, doi:10.3762/bjnano.4.5

• slowly varied (frequency-shift–distance curves). Active feedback is used to adjust both the drive power and drive frequency, to keep the response amplitude and phase constant. The obtained frequency shifts and drive forces can then be converted into the force quadratures [38][39] so that the measurement

Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy

• Jannis Lübbe,
• Matthias Temmen,
• Sebastian Rode,
• Philipp Rahe,
• Angelika Kühnle and
• Michael Reichling

Beilstein J. Nanotechnol. 2013, 4, 32–44, doi:10.3762/bjnano.4.4

• system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth. Keywords: Cantilever; feedback loop; filter; noncontact atomic force

• by the amplitude feedback loop. Signal processing in NC-AFM involves the demodulation of the periodic cantilever-displacement signal Vz(t) as well as filtering in the frequency domain to yield the frequency shift Δf(t) carrying the information on the tip–surface interaction [1]. Demodulation is

• instabilities arising from the interaction of the force microscopy tip with the surface as well as arising from the feedback loops stabilising the cantilever oscillation amplitude and the tip–surface distance [5]. Here, we investigate noise for the case of negligible tip–surface interaction and discuss the

Characterization of the mechanical properties of qPlus sensors

• Jan Berger,
• Martin Švec,
• Martin Müller,
• Martin Ledinský,
• Antonín Fejfar,
• Pavel Jelínek and
• Zsolt Majzik

Beilstein J. Nanotechnol. 2013, 4, 1–9, doi:10.3762/bjnano.4.1

• routinely used nowadays as a standard technique to characterize and modify objects at the atomic scale. However, its application is limited only to conductive samples as the tunneling current flowing between a probe and a sample is employed as the feedback signal. This limitation was surpassed by AFM

• by two electrodes of the fork during its sinusoidal motion. OP 111 operational amplifiers (OPA) in a TO 99 package were used as IVCs with 100 MΩ feedback resistors. In order to gain the maximum performance of the device, the inputs of amplifiers were brought as close as possible to the outputs of the

• sensor: the lengths of the connecting wires were about 1 cm only. Furthermore, the SMD-packed feedback resistor was mounted directly between the input and the output legs minimizing the length of wiring to a few millimetres. By this construction the input and the parasitic capacitance of the feedback

Pure hydrogen low-temperature plasma exposure of HOPG and graphene: Graphane formation?

• Baran Eren,
• Dorothée Hug,
• Laurent Marot,
• Rémy Pawlak,
• Marcin Kisiel,
• Roland Steiner,
• Dominik M. Zumbühl and
• Ernst Meyer

Beilstein J. Nanotechnol. 2012, 3, 852–859, doi:10.3762/bjnano.3.96

• Nanosurf FlexAFM operated in ambient conditions. The quantities that were measured are the cantilever oscillation amplitude (Afree = 20 nm) and phase related to the driving signal. The distance to the sample was controlled in a feedback loop, maintaining the cantilever oscillation amplitude equal to a

Physics, chemistry and biology of functional nanostructures

• Paul Ziemann and
• Thomas Schimmel

Beilstein J. Nanotechnol. 2012, 3, 843–845, doi:10.3762/bjnano.3.94

• understanding of nanoscaled phenomena. We deem progress in theory necessary in order to gain feedback for testing new predicted phenomena or optimizing already existing nanosystems and devices. All three of these conditions together with the given examples play a major role in the present Thematic Series, which

Large-scale analysis of high-speed atomic force microscopy data sets using adaptive image processing

• Blake W. Erickson,
• Séverine Coquoz,
• Jonathan D. Adams,
• Daniel J. Burns and
• Georg E. Fantner

Beilstein J. Nanotechnol. 2012, 3, 747–758, doi:10.3762/bjnano.3.84

• . Square areas of 4 µm were scanned at 78 lines/second at 256 × 256 pixels giving an approximate image acquisition time of 3 seconds/image. The fast-scan drive signal was passed through a custom filter designed to minimize the excitation of the tube scanner resonance [38]. The internal PID feedback of the

The memory effect of nanoscale memristors investigated by conducting scanning probe microscopy methods

• César Moreno,
• Carmen Munuera,
• Xavier Obradors and
• Carmen Ocal

Beilstein J. Nanotechnol. 2012, 3, 722–730, doi:10.3762/bjnano.3.82

• conducting tip (top electrode) was placed in direct contact with the sample surface, under controlled load, i.e., by using a normal force feedback, and the current between the tip and sample was measured. Simultaneous topographic images z(x,y) and current maps I(x,y) over a given region at a fixed voltage

Probing three-dimensional surface force fields with atomic resolution: Measurement strategies, limitations, and artifact reduction

• Mehmet Z. Baykara,
• Omur E. Dagdeviren,
• Todd C. Schwendemann,
• Harry Mönig,
• Eric I. Altman and
• Udo D. Schwarz

Beilstein J. Nanotechnol. 2012, 3, 637–650, doi:10.3762/bjnano.3.73

• current, which is recorded together with the frequency-shift data, does not decay too fast to provide accurate calibration at all distances covered by the 3-D set. A completely different source of drift may originate from the use of analog electronics for oscillation detection and amplitude/phase-feedback

• the layer-by-layer approach with active feedback are likely restricted to tip–sample distances that are unaffected by contrast flips. This situation changes if asymmetric tips are employed. For θ values of 45° and 58° (Figures 6b and Figure 6c, respectively), the simulated atomic-scale force fields

Mapping mechanical properties of organic thin films by force-modulation microscopy in aqueous media

• Jianming Zhang,
• Zehra Parlak,
• Carleen M. Bowers,
• Terrence Oas and
• Stefan Zauscher

Beilstein J. Nanotechnol. 2012, 3, 464–474, doi:10.3762/bjnano.3.53

• Supporting Information File 1). The cantilever deflection with a second-order harmonic can be rewritten as, where is the second-harmonic factor. The frequency-independent, zeroth-order term in Equation 3 reflects a DC deflection. The feedback loop, however, cannot differentiate this zeroth-order component

• from the surface-topography-induced deflection response of the cantilever, thus precluding clear signal deconvolution [29]. Both the first and second harmonics, however, do not interfere with the feedback loop and can be detected by lock-in techniques. At low forces, the second-harmonic factor (β

• feedback controller of the AFM keeps the tip–sample force constant during the surface scan. In addition, however, a piezoelectric transducer in the cantilever holder was used to excite the cantilever with a small amplitude, off-resonance frequency. A lock-in amplifier (AMETEK model 7280) was used to

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

• feedback, whereas the amplitude and phase of the higher eigenmode encode the material contrast. According to previous experiments and theoretical simulations, the second eigenmode of a cantilever is very sensitive to material variations [6][13]. With standard silicon cantilevers, bimodal force microscopy

• instantaneous amplitude of the combined motion varies: A01 − A02 ≤ Ainst ≤ A01 + A02. Under such conditions, the higher-frequency oscillation only slightly affects topographical feedback because the first eigenmode is barely affected by the second eigenmode. The response of the second-eigenmode amplitude

Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids

• Miriam Jaafar,
• David Martínez-Martín,
• Mariano Cuenca,
• John Melcher,
• Arvind Raman and
• Julio Gómez-Herrero

Beilstein J. Nanotechnol. 2012, 3, 336–344, doi:10.3762/bjnano.3.38

• microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses

• the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different

• environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode. Keywords: atomic force microscopy; control systems; dissipation; frequency

Combining nanoscale manipulation with macroscale relocation of single quantum dots

• Francesca Paola Quacquarelli,
• Richard A. J. Woolley,
• Martin Humphry,
• Jasbiner Chauhan,
• Philip J. Moriarty and
• Ashley Cadby

Beilstein J. Nanotechnol. 2012, 3, 324–328, doi:10.3762/bjnano.3.36

• that have resulted in a break up of a cluster or a manipulation that has not successfully manipulated a single QD. Our manipulation routines are also quite uncomplicated, using the AFM in contact mode rather than lift mode, allowing us to maintain feedback as the nanoparticles are pushed. Importantly

Graphite, graphene on SiC, and graphene nanoribbons: Calculated images with a numerical FM-AFM

• Fabien Castanié,
• Laurent Nony,
• Sébastien Gauthier and
• Xavier Bouju

Beilstein J. Nanotechnol. 2012, 3, 301–311, doi:10.3762/bjnano.3.34

• fork and provides a stiff probe capable of being approached close enough to the sample without touching the surface [62]. When the probe is oscillating above the sample, one of the characteristics of an experimental FM-AFM setup is the presence of several feedback loops to pilot the probe based on the

Dipole-driven self-organization of zwitterionic molecules on alkali halide surfaces

• Laurent Nony,
• Franck Bocquet,
• Franck Para,
• Frédéric Chérioux,
• Eric Duverger,
• Frank Palmino,
• Vincent Luzet and
• Christian Loppacher

Beilstein J. Nanotechnol. 2012, 3, 285–293, doi:10.3762/bjnano.3.32

• oscillation feedback controller and the topography is regulated by keeping the frequency shift Δf constant. The contact potential difference between the tip and the sample was compensated by applying the corresponding bias voltage to the tip (static, no feedback). For image evaluation we used the WSxM