A robust AFM-based method for locally measuring the elasticity of samples

• Alexandre Bubendorf,
• Stefan Walheim,
• Thomas Schimmel and
• Ernst Meyer

Beilstein J. Nanotechnol. 2018, 9, 1–10, doi:10.3762/bjnano.9.1

• excitation of two cantilever eigenmodes [17][18][19][20][21], are performed in non-dry air, the instability of the tip–sample distance feedback loop, due to the use of the frequency shift as control parameter, makes the application of the method difficult if not impossible. However, despite these

• modulus of the tip Etip is at least two orders of magnitude larger than that of the sample Esample then Feedback controls As introduced by Herruzo et al. [7], five different feedback loops are used as feedback controls, as shown in Figure 1: two feedback loops for keeping the amplitudes A1 and A2 constant

• , two feedback loops for keeping the phase shifts 1 and 2 constant in order to track the contact resonances f1 and f2, and the last feedback loop as main feedback for controlling the applied normal force FN. Experimental Microscope and data acquisition The measurements were performed with a flex AFM

Material discrimination and mixture ratio estimation in nanocomposites via harmonic atomic force microscopy

• Weijie Zhang,
• Yuhang Chen,
• Xicheng Xia and
• Jiaru Chu

Beilstein J. Nanotechnol. 2017, 8, 2771–2780, doi:10.3762/bjnano.8.276

• materials and to estimate the mixture ratio of the constituent components in nanocomposites. The major influencing factors, namely amplitude feedback set-point, drive frequency and laser spot position along the cantilever beam, were systematically investigated. Employing different set-points induces

• signals were investigated systematically on a polymer blend composed of polystyrene (PS) and low-density polyehtylene (LDPE). We focused on the influence of feedback amplitude set-point, drive frequency and laser spot position along the cantilever beam. Based on these fundamental studies, harmonic AFM

• imaging was utilized to distinguish NP mixtures with different elastic properties and mixture ratios. Results and Discussion Effect of amplitude set-point The first investigated factor is the amplitude set-point, which is specified by A/A0 where A is the feedback amplitude and A0 the free amplitude. In

Towards molecular spintronics

• Georgeta Salvan and
• Dietrich R. T. Zahn

Beilstein J. Nanotechnol. 2017, 8, 2464–2466, doi:10.3762/bjnano.8.245

• , taking into account that for device integration, the molecular layers need to obey certain boundary conditions, such as long-term stability, process compatibility, and the ability to integrate with electrode materials. Progress in this respect was only made possible by a continuous feedback from basic

• highly professional support and always very fast feedback. We would also like to thank all referees for their effort and constructive criticism. Georgeta Salvan and Dietrich R. T. Zahn Chemnitz, October 2017

Au nanostructure fabrication by pulsed laser deposition in open air: Influence of the deposition geometry

• Rumen G. Nikov,
• Anna Og. Dikovska,
• Nikolay N. Nedyalkov,
• Georgi V. Avdeev and
• Petar A. Atanasov

Beilstein J. Nanotechnol. 2017, 8, 2438–2445, doi:10.3762/bjnano.8.242

• coverage. It should be mentioned that a feedback between the optical and electrical properties of the nanostructures was observed. Higher optical transmission of the nanostructures was associated with a predominantly discrete morphology, as was discussed above. The conductivity of the samples was found to

Robust procedure for creating and characterizing the atomic structure of scanning tunneling microscope tips

• Sumit Tewari,
• Koen M. Bastiaans,
• Milan P. Allan and
• Jan M. van Ruitenbeek

Beilstein J. Nanotechnol. 2017, 8, 2389–2395, doi:10.3762/bjnano.8.238

• [1][2], it became possible to image conducting surfaces with atomic resolution. STM operates by bringing the apex of a fine metallic wire into tunneling distance from a surface of interest. By providing feedback in the tunnel current and scanning the tip over the surface one can make topographic maps

• and mechanical drift have been stabilized, we release the current feedback and move the tip towards surface at a rate of 0.5 Å/s using a custom-written program in MATLAB. The motion is stopped once the conductance reaches the quantum of conductance (G0 = 2e2/h, which is what we expect for a single

• a detectable contribution. In order to scan at such high tunnel currents we first switch off the current feedback and bring the tip closer to the flat part of the surface to a fixed tunnel current value. This value is chosen to ensure that the current is as high as 30 nA, when the tip is over the

Magnetic properties of optimized cobalt nanospheres grown by focused electron beam induced deposition (FEBID) on cantilever tips

• Soraya Sangiao,
• César Magén,
• Darius Mofakhami,
• Grégoire de Loubens and
• José María De Teresa

Beilstein J. Nanotechnol. 2017, 8, 2106–2115, doi:10.3762/bjnano.8.210

• standard laser deflection technique is used to monitor the displacement of the cantilever. Its resonance frequency is tracked using a piezoelectric bimorph and a feedback electronic circuit based on a phase lock loop. The relative frequency shift due to the force acting on the magnetic moment m of the

High-stress study of bioinspired multifunctional PEDOT:PSS/nanoclay nanocomposites using AFM, SEM and numerical simulation

• Alfredo J. Diaz,
• Hanaul Noh,
• Tobias Meier and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2017, 8, 2069–2082, doi:10.3762/bjnano.8.207

• . The fundamental eigenmode is operated in amplitude modulation, i.e., there is a feedback loop modulating the oscillation amplitude for acquiring the topography of the sample, while the higher eigenmode (in this case the second eigenmode) is operated with constant excitation frequency and amplitude

• , without feedback [61]. CRFM-DART was used as implemented in the Asylum Research software. In general, the cantilever is shaken sinusoidally while in continuous contact with the sample, measuring two parameters: the resonance frequency and quality factor of the tip–sample junction (as shown in Figure 6a

(Metallo)porphyrins for potential materials science applications

• Lars Smykalla,
• Carola Mende,
• Michael Fronk,
• Pablo F. Siles,
• Michael Hietschold,
• Georgeta Salvan,
• Dietrich R. T. Zahn,
• Oliver G. Schmidt,
• Tobias Rüffer and
• Heinrich Lang

Beilstein J. Nanotechnol. 2017, 8, 1786–1800, doi:10.3762/bjnano.8.180

• from [44], copyright 2014 Elsevier. (a–e) Manipulation of the electronic structure by applying a voltage pulse with the STM tip at the position marked with a white circle. Converted molecules are marked with green (1→2) or blue (2→1) rectangles. (a–c) 1→2→1 conversion with 2 V pulses for 3 s (feedback

Transport characteristics of a silicene nanoribbon on Ag(110)

• Ryoichi Hiraoka,
• Chun-Liang Lin,
• Kotaro Nakamura,
• Ryo Nagao,
• Maki Kawai,
• Ryuichi Arafune and
• Noriaki Takagi

Beilstein J. Nanotechnol. 2017, 8, 1699–1704, doi:10.3762/bjnano.8.170

• consisting of an SiNR, the STM tip and the Ag substrate. This method reduces the SiNR–Ag interaction and enables us to reveal the intrinsic features of SiNRs. The measurements were performed by a scheme summarized in Figure 3a. At first, the STM tip is fixed over one end of the SiNR while the STM feedback

• feedback is turned off at VS = 100 mV and It = 20 pA and the conductance is measured at VS = 100 mV. The conductance measured during the tip approach and retraction procedures is plotted with black and blue circles, respectively. The red curve shows the result of the least-squares fitting. In the

Air–water interface of submerged superhydrophobic surfaces imaged by atomic force microscopy

• Markus Moosmann,
• Thomas Schimmel,
• Wilhelm Barthlott and
• Matthias Mail

Beilstein J. Nanotechnol. 2017, 8, 1671–1679, doi:10.3762/bjnano.8.167

• the data presented in Figure 3. However, the corresponding cross-section (Figure 5b, red line) contains two artifacts: the additional elevation at the pillar top is due to the feedback loop of the AFM system causing an overshoot in the height signal. The slope on the right, which seems to be too flat

High-speed dynamic-mode atomic force microscopy imaging of polymers: an adaptive multiloop-mode approach

• Juan Ren and
• Qingze Zou

Beilstein J. Nanotechnol. 2017, 8, 1563–1570, doi:10.3762/bjnano.8.158

• control mechanism applied [4][6]. Due to the time delay inevitably induced into the feedback loop for maintaining the RMS tapping amplitude during imaging, errors in tracking the sample topography can quickly result in loss of the tip–sample contact and annihilation of the probe tapping when the imaging

• deflection (the TM deflection) – in addition to the transitional RMS amplitude feedback control, along with an online iterative feedforward control to track the sample topography. Although this AMLM technique has been proposed recently [1], imaging results of only one polymer sample at large scanning size

• track the sample topography by the AFM z-axis piezo. AMLM imaging introduces a feedback control of inner–outer loop structure to regulate the mean cantilever deflection per vibration period (called the TM-deflection). Thus the averaged (vertical) position of the cantilever in each tapping period is kept

A review of demodulation techniques for amplitude-modulation atomic force microscopy

• Michael G. Ruppert,
• David M. Harcombe,
• Michael R. P. Ragazzon,
• S. O. Reza Moheimani and
• Andrew J. Fleming

Beilstein J. Nanotechnol. 2017, 8, 1407–1426, doi:10.3762/bjnano.8.142

• used digital processing system. As a crucial bandwidth-limiting component in the z-axis feedback loop of an atomic force microscope, the purpose of the demodulator is to obtain estimates of amplitude and phase of the cantilever deflection signal in the presence of sensor noise or additional distinct

• nonlinear tip–sample forces acting on the cantilever, a feedback loop has to be employed in order to maintain a fixed setpoint with respect to the sample; the controller performs disturbance rejection by commanding a nanopositioner in its vertical direction. As the high-frequency cantilever deflection

• signal cannot be controlled directly, low-frequency measurables such as the change in oscillation amplitude in amplitude-modulation AFM [11] have to be employed. Other feedback variables such as the shift in cantilever resonance frequency in frequency-modulation AFM [13] or the phase shift in phase

Adsorption characteristics of Er₃N@C₈₀on W(110) and Au(111) studied via scanning tunneling microscopy and spectroscopy

• Sebastian Schimmel,
• Zhixiang Sun,
• Danny Baumann,
• Denis Krylov,
• Nataliya Samoylova,
• Alexey Popov,
• Bernd Büchner and
• Christian Hess

Beilstein J. Nanotechnol. 2017, 8, 1127–1134, doi:10.3762/bjnano.8.114

• , with the bias voltage applied to the tip. The generated images were processed using WSxM [13]. The spatially resolved spectroscopy information was taken by I(U) measurements at open feedback loop at every pixel of the corresponding image. In order to obtain dI/dU(U) data a posterior numerical

BTEX detection with composites of ethylenevinyl acetate and nanostructured carbon

• Santa Stepina,
• Astrida Berzina,
• Gita Sakale and
• Maris Knite

Beilstein J. Nanotechnol. 2017, 8, 982–988, doi:10.3762/bjnano.8.100

• quantitatively characterizes the degree of dispersion. The investigated area size is 100 × 100 μm, the feedback system gain is 1.0, the probe movement speed is 142 μm/s, the image resolution is 512 pt, the applied voltage is 0.5 V and the set point is +2. From [24] the composite is characterized by acquiring a

Scaling law to determine peak forces in tapping-mode AFM experiments on finite elastic soft matter systems

• Horacio V. Guzman

Beilstein J. Nanotechnol. 2017, 8, 968–974, doi:10.3762/bjnano.8.98

• oscillates at its fundamental flexural resonant frequency while the amplitude is used as the feedback parameter to record the topography while imaging. When the tip is in close proximity to the sample the amplitude and the phase shift of the oscillation change with the strength of the tip–sample interaction

• . Ricardo Garcia, Elena T. Herruzo, Marco Chiesa, and Torsten Stuehn for reading the manuscript and giving his valuable feedback.

Analysis and modification of defective surface aggregates on PCDTBT:PCBM solar cell blends using combined Kelvin probe, conductive and bimodal atomic force microscopy

• Hanaul Noh,
• Alfredo J. Diaz and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2017, 8, 579–589, doi:10.3762/bjnano.8.62

• other hand, the soft cantilever makes it possible to obtain current and potential correlations for the defective areas without severely altering the structure of the aggregates, by applying only a few nanonewtons of feedback force. Although it is in principle possible to use contact-mode AFM for the

• . (a)–(d) Topographies consecutively obtained by tapping-mode bimodal AFM using the first eigenmode of the cantilever for the distance feedback control and the third eigenmode for modulating indentation. (e)–(h) The third eigenmode amplitude signal, corresponding to a free amplitude of about 3 nm

Copper atomic-scale transistors

• Fangqing Xie,
• Maryna N. Kavalenka,
• Moritz Röger,
• Daniel Albrecht,
• Hendrik Hölscher,
• Jürgen Leuthold and
• Thomas Schimmel

Beilstein J. Nanotechnol. 2017, 8, 530–538, doi:10.3762/bjnano.8.57

• ) influence the switching rate of the transistor and the copper deposition on the electrodes, and correspondingly shift the electrochemical operation potential. The copper atomic-scale transistors can be switched using a function generator without a computer-controlled feedback switching mechanism. The copper

• developed in “NI LabVIEW” and the conductance was recorded simultaneously with the same program. The electrochemical potential was set using a feedback mechanism, in which the measured conductance was compared with a preset value of quantum conductance of the copper atomic-scale transistor. A transistor

• are operated. With the feedback mechanism the conductance switching is well controlled between “open” and “quantum conductance” (as displayed in Figure 2 and Figure 3), but the duration of each switching cycle varies. Moreover, the maximum/minimum potential values applied on the gate change from one

Multimodal cantilevers with novel piezoelectric layer topology for sensitivity enhancement

• Steven Ian Moore,
• Michael G. Ruppert and
• Yuen Kuan Yong

Beilstein J. Nanotechnol. 2017, 8, 358–371, doi:10.3762/bjnano.8.38

• frequency shift of the cantilever’s motion correlate to properties of the sample [15]. When closing a feedback loop around these observables with the z-axis nanopositioner, the controller output is routinely used to map the surface topography of the sample. Recently, the additional excitation and detection

• structure as in Equation 21, however the resulting transfer function shows flipped poles and zeros (compare Figure 7) as well as slightly differing gains, quality factors and resonance frequencies due to the internal feedback nature in Equation 20 [40]. The transfer function in the neighborhood of the

When the going gets rough – studying the effect of surface roughness on the adhesive abilities of tree frogs

• Niall Crawford,
• Thomas Endlein,
• Jonathan T. Pham,
• Mathis Riehle and
• W. Jon P. Barnes

Beilstein J. Nanotechnol. 2016, 7, 2116–2131, doi:10.3762/bjnano.7.201

• on the force plate which could be moved relative to it by a pair of computer-controlled precision manipulating stages (model PD-126M, Physik Instrumente, Karlsruhe, Germany). A force feedback system implemented in LabView was programmed to maintain a constant preload (2 mN) for measurements of

Noise in NC-AFM measurements with significant tip–sample interaction

• Jannis Lübbe,
• Matthias Temmen,
• Philipp Rahe and
• Michael Reichling

Beilstein J. Nanotechnol. 2016, 7, 1885–1904, doi:10.3762/bjnano.7.181

• increased due to a coupling of the phase-locked loop with the amplitude and the distance control loops. While noise in the amplitude control loop itself is essentially independent of the frequency shift noise without tip–sample interaction, amplitude and topography feedback loop noise are coupled into the

• ), the parameter βts can be obtained by using either the frequency shift set-point Δfset for the topography feedback or by the average frequency shift measured at the tip–sample distance zp with deactivated topography feedback loop. For the numerical evaluation of signal vs time traces and noise spectra

• filtered by the narrowband cantilever response function Hc(f). In the frequency control loop (bottom part of Figure 2), the measured cantilever displacement signal is fed into the PLL demodulator yielding the frequency shift signal Δf as well as the excitation signal for the cantilever in the feedback path

Dynamic of cold-atom tips in anharmonic potentials

• Tobias Menold,
• Peter Federsel,
• Carola Rogulj,
• Hendrik Hölscher,
• József Fortágh and
• Andreas Günther

Beilstein J. Nanotechnol. 2016, 7, 1543–1555, doi:10.3762/bjnano.7.148

• atoms and could possibly allow for active feedback control of the tip motion. Methods like Q-control [33][34], which have been very successful in conventional force microscopy [35][36], are therefore realizable. The article is structured as follows: We start by describing the theory of tip motion in

Customized MFM probes with high lateral resolution

• Óscar Iglesias-Freire,
• Miriam Jaafar,
• Eider Berganza and
• Agustina Asenjo

Beilstein J. Nanotechnol. 2016, 7, 1068–1074, doi:10.3762/bjnano.7.100

• MFM data correspond to the shift in the resonance frequency of the cantilever recorded during the retrace scan (withdrawing the sample by 10–20 nm from the topographic set point distance) by using a phase locked-loop (PLL) feedback. The topography and the magnetic properties of the reference Co/Si

Generalized Hertz model for bimodal nanomechanical mapping

• Aleksander Labuda,
• Marta Kocuń,
• Waiman Meinhold,
• Deron Walters and
• Roger Proksch

Beilstein J. Nanotechnol. 2016, 7, 970–982, doi:10.3762/bjnano.7.89

• as amplitude-modulation (AM) AFM [18][19][20]), is one of the most commonly used parametric techniques, where the cantilever is driven on resonance and the cantilever–sample distance is adjusted by a feedback loop to maintain a constant oscillation amplitude at every image pixel. The time required

• feedback loops used for the PM and FM modes tracked changes in the cantilever eigenmode appropriately. Large and small amplitude approximations The amplitude of the first mode was modeled in the large limit, while the amplitude of the second mode was modeled in the small limit. The validity of these

Noncontact atomic force microscopy III

• Mehmet Z. Baykara and
• Udo D. Schwarz

Beilstein J. Nanotechnol. 2016, 7, 946–947, doi:10.3762/bjnano.7.86

• outermost atoms of the probe apex and the atoms on the surface then cause a downshift in oscillation frequency, which is employed as the feedback signal during lateral scanning. In this way, the probe apex remains atomically sharp and it becomes possible to attain atomic-scale resolution on a wide variety

Modelling of ‘sub-atomic’ contrast resulting from back-bonding on Si(111)-7×7

• Adam Sweetman,
• Samuel P. Jarvis and
• Mohammad A. Rashid

Beilstein J. Nanotechnol. 2016, 7, 937–945, doi:10.3762/bjnano.7.85

• separation. Note a 10 point gaussian filter has been applied to all images to remove high frequency noise. Experimental parameters: A0 = 110 pm, Vgap = 0 V. Experimental tip heights relative to Δf feedback setpoint (top to bottom): +0.186 nm, +0.104 nm, +0.032 nm, 0 nm. Image size 3.6 nm × 3.6 nm. Data