A review of demodulation techniques for multifrequency atomic force microscopy

• David M. Harcombe,
• Michael G. Ruppert and
• Andrew J. Fleming

Beilstein J. Nanotechnol. 2020, 11, 76–91, doi:10.3762/bjnano.11.8

• the cantilever according to the expression f−3dB = f0/2Q, where f0 is the fundamental resonance frequency. Assuming all other components in the z-axis feedback loop are also working at high speed [3], a low quality factor can demand a fast demodulator [12]. Multifrequency AFM (MF-AFM) is a major field

• flexibility in achieving a desired bandwidth as the (N + 1)-FIR filter is longer. Here, the group delay (N/2) introduced should be considered with respect to the phase margin of the z-axis feedback loop. Off-mode rejection Each multifrequency demodulator was assessed by applying a single-tone sine sweep of

The effect of heat treatment on the morphology and mobility of Au nanoparticles

• Sven Oras,
• Sergei Vlassov,
• Simon Vigonski,
• Boris Polyakov,
• Mikk Antsov,
• Vahur Zadin,
• Rünno Lõhmus and
• Karine Mougin

Beilstein J. Nanotechnol. 2020, 11, 61–67, doi:10.3762/bjnano.11.6

• were heated to 100 °C to remove excess water. An image was first taken in the high-resolution QNM mode to find the Au particles. Then, the operation mode was switched to tapping mode. The oscillation amplitude was kept constant with a feedback loop on, and the power dissipated during tapping was

Development of a new hybrid approach combining AFM and SEM for the nanoparticle dimensional metrology

• Loïc Crouzier,
• Alexandra Delvallée,
• Sébastien Ducourtieux,
• Laurent Devoille,
• Guillaume Noircler,
• Christian Ulysse,
• Olivier Taché,
• Elodie Barruet,
• Christophe Tromas and
• Nicolas Feltin

Beilstein J. Nanotechnol. 2019, 10, 1523–1536, doi:10.3762/bjnano.10.150

• . In contact mode, the interaction force is kept constant during the scanning thanks to a feedback loop that controls the tip–sample distance. This mode is not really suitable for NP imaging because the NPs might be displaced by the tip over the sample. To avoid this effect, the intermittent contact

Molecular attachment to a microscope tip: inelastic tunneling, Kondo screening, and thermopower

• Rouzhaji Tuerhong,
• Mauro Boero and
• Jean-Pierre Bucher

Beilstein J. Nanotechnol. 2019, 10, 1243–1250, doi:10.3762/bjnano.10.124

• step-by-step temperature increase, the feedback loop was “on” (0.2 nA, −0.3V) to prevent accidental loss of the MnPc molecular junction. As soon as the stable sample temperature was reached, the feedback loop was opened (0.1 nA, −0.3 V) and the dI/dV spectra were acquired at the stabilized sample

• surprising since is too small to produce any smearing of the Kondo resonance [36]. The Seebeck coefficient S can be calculated from the dI/dV data as a function of the temperature, obtained at constant height with an open feedback loop [37]: where σ(V) is the differential conductance and Σ(V) is its

• vertically for clarity. The feedback loop has been opened at 0.1 nA, −0.30 V. (c) Maximum conductance of the zero-bias peak as a function of the sample temperature Ts . (d) Conductance step at positive bias as a function of the sample temperature Ts. (e) Close-up of the dI/dV spectra showing the zero-bias

Review of time-resolved non-contact electrostatic force microscopy techniques with applications to ionic transport measurements

• Aaron Mascaro,
• Yoichi Miyahara,
• Tyler Enright,
• Omur E. Dagdeviren and
• Peter Grütter

Beilstein J. Nanotechnol. 2019, 10, 617–633, doi:10.3762/bjnano.10.62

• faster than the KPFM feedback loop can track [36]. In this measurement mode, the tip–sample coupling is in an ‘always-on’ state and the time resolution is achieved by modulating the length of time the system is allowed to decay (i.e., the pulse-off time). The minimum time resolution is no longer limited

Intuitive human interface to a scanning tunnelling microscope: observation of parity oscillations for a single atomic chain

• Sumit Tewari,
• Jacob Bakermans,
• Christian Wagner,
• Federica Galli and
• Jan M. van Ruitenbeek

Beilstein J. Nanotechnol. 2019, 10, 337–348, doi:10.3762/bjnano.10.33

• ’, ‘ii’ and ‘iii’ are marked with respect to the three adatoms shown and also some other neighbouring adatoms, which are outside the field of view in the figure. We have performed manipulation in a new point contact pushing (PCP) mode with feedback loop switched off. The difference between our PCP mode

• feedback loop from the experimental conductance values, a real-time conductance estimation based on the atomistic positions given by the MD simulations could be useful. Tight-binding models have been known [56] to give a relatively fast (as compared to DFT and other computationally expensive methods

Apparent tunneling barrier height and local work function of atomic arrays

• Neda Noei,
• Alexander Weismann and
• Richard Berndt

Beilstein J. Nanotechnol. 2018, 9, 3048–3052, doi:10.3762/bjnano.9.283

• of the vertical tip excursion Δz the feedback loop of the STM was disabled at a sample voltage of V = 20 mV and a current of I = 200 pA. The tip was then brought closer to the structure under investigation at a rate of 1.7 nm/s while recording I. Figure 2 shows typical results from a clean (111

Investigation of CVD graphene as-grown on Cu foil using simultaneous scanning tunneling/atomic force microscopy

• Majid Fazeli Jadidi,
• Umut Kamber,
• Oğuzhan Gürlü and
• H. Özgür Özer

Beilstein J. Nanotechnol. 2018, 9, 2953–2959, doi:10.3762/bjnano.9.274

• the entire cycle. Consequently, while the constant tunnel current is used as feedback loop, the use of very small oscillation amplitudes ensures simultaneous STM/AFM operation as close as possible to the actual STM mode [30][33]. The combination of these two techniques attracts great interest for

Charged particle single nanometre manufacturing

• Philip D. Prewett,
• Cornelis W. Hagen,
• Claudia Lenk,
• Steve Lenk,
• Marcus Kaestner,
• Tzvetan Ivanov,
• Ahmad Ahmad,
• Ivo W. Rangelow,
• Xiaoqing Shi,
• Stuart A. Boden,
• Alex P. G. Robinson,
• Dongxu Yang,
• Sangeetha Hari,
• Marijke Scotuzzi and
• Ejaz Huq

Beilstein J. Nanotechnol. 2018, 9, 2855–2882, doi:10.3762/bjnano.9.266

Low cost tips for tip-enhanced Raman spectroscopy fabricated by two-step electrochemical etching of 125 µm diameter gold wires

• Antonino Foti,
• Francesco Barreca,
• Enza Fazio,
• Cristiano D’Andrea,
• Paolo Matteini,
• Onofrio Maria Maragò and
• Pietro Giuseppe Gucciardi

Beilstein J. Nanotechnol. 2018, 9, 2718–2729, doi:10.3762/bjnano.9.254

• removed from the near-field region of the sample, just excluding the feedback loop of the STM system. Vibrational bands of all molecules agree with the literature [60][61][62][63]. We finally apply our tips to obtain TERS spectra from the N-terminal domain of the Escherichia coli protein HypF (HypF-N

• oligomers when the STM feedback loop is on (red line) and when it is off (black line). Experimental conditions: λexc = 638 nm, P = 0.11 mW, t = 10 s. (a) STM image of Au(111) terraces on which R6G 10−4 M is adsorbed (∆V = 0.05 V – tip positive, current set point is 80 pA). The gray line indicates the zone

Dumbbell gold nanoparticle dimer antennas with advanced optical properties

• Janning F. Herrmann and
• Christiane Höppener

Beilstein J. Nanotechnol. 2018, 9, 2188–2197, doi:10.3762/bjnano.9.205

• maintained with sub-nanometer accuracy to 2–4 nm by means of a force feedback loop regulating on the frequency shift of the force sensor, which is excited at its resonance frequency. The fluorescence emission rate as a function of the antenna–sample distance is recorded with the feedback loop switched off

The structural and chemical basis of temporary adhesion in the sea star Asterina gibbosa

• Birgit Lengerer,
• Marie Bonneel,
• Mathilde Lefevre,
• Elise Hennebert,
• Philippe Leclère,
• Emmanuel Gosselin,
• Peter Ladurner and
• Patrick Flammang

Beilstein J. Nanotechnol. 2018, 9, 2071–2086, doi:10.3762/bjnano.9.196

• (Bruker Nano Inc., Santa Barbara, CA) using AFM in tapping mode. Tapping mode AFM was performed in amplitude modulation mode. The height of the cantilever position is constantly adjusted (via a feedback loop) to keep constant the ratio of the tip vibrational amplitude in contact with the sample surface to

Quantitative comparison of wideband low-latency phase-locked loop circuit designs for high-speed frequency modulation atomic force microscopy

• Kazuki Miyata and
• Takeshi Fukuma

Beilstein J. Nanotechnol. 2018, 9, 1844–1855, doi:10.3762/bjnano.9.176

• the conventional PLL design and their possible solutions. In the conventional design, a low-pass filter with relatively high latency is used in the phase feedback loop, leading to a slow response of the PLL. In the proposed design, a phase detector with a low-latency high-pass filter is located

• outside the phase feedback loop, while a subtraction-based phase comparator with negligible latency is located inside the loop. This design minimizes the latency within the phase feedback loop and significantly improves the PLL response speed. In addition, we implemented PLLs with the conventional and

• signal so that remains constant. In this way, the VCO, PC, and LF form a phase feedback loop, as illustrated in Figure 1. In a steady state, the frequency of the VCO output agrees with that of the PLL input. Thus, the VCO input changes in proportion to the frequency shift Δω of the PLL input. This

Know your full potential: Quantitative Kelvin probe force microscopy on nanoscale electrical devices

• Amelie Axt,
• Ilka M. Hermes,
• Victor W. Bergmann,
• Niklas Tausendpfund and
• Stefan A. L. Weber

Beilstein J. Nanotechnol. 2018, 9, 1809–1819, doi:10.3762/bjnano.9.172

• ωE vanishes. In AM-KPFM, a feedback loop that minimizes the response amplitude by adjusting UDC. AM detection is ususally more prone to artifacts such cross coupling of the AC drive signal, e.g., into the shaker piezo [21]. Furthermore, Equation 3 shows that the amplitude of the electrostatic force

Direct AFM-based nanoscale mapping and tomography of open-circuit voltages for photovoltaics

• Katherine Atamanuk,
• Justin Luria and
• Bryan D. Huey

Beilstein J. Nanotechnol. 2018, 9, 1802–1808, doi:10.3762/bjnano.9.171

• leverages photo-conducting AFM, along with an additional proportional-integral-derivative feedback loop configured to maintain open-circuit conditions while scanning. Alternating with short-circuit current mapping efficiently provides complementary insight into the highly microstructurally sensitive local

• energetic resolution unavoidably conflicts with experimental throughput. Accordingly, this work presents a new approach for directly mapping VOC with nanoscale resolution, requiring a single, standard-speed AFM scan. This leverages the concept of the proportional-integral-derivative (PID) feedback loop that

• underpins nearly all AFM topography imaging. Normally, this feedback loop continually updates the AFM probe height in order to maintain a constant AFM tip–sample interaction, which is sensed via the integrated cantilever deflection or amplitude that, of course, changes at surface protrusions or depressions

Lyapunov estimation for high-speed demodulation in multifrequency atomic force microscopy

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

Beilstein J. Nanotechnol. 2018, 9, 490–498, doi:10.3762/bjnano.9.47

• observables for the characterization of nanomechanical properties. Due to the large bandwidth requirements of tracking high frequencies in MF-AFM, every component of the z-axis feedback loop detailed in Figure 1 needs to be optimized for speed. This includes the lateral and vertical nanopositioner for each

• is shown to have a negative feedback loop in which integral action regulates the error. By feeding back an estimate of the input signal obtained from the parameterized states in the form of Equation 3, an error signal is generated. Regulation of this error through feedback leads to the much desired

The nanofluidic confinement apparatus: studying confinement-dependent nanoparticle behavior and diffusion

• Stefan Fringes,
• Felix Holzner and
• Armin W. Knoll

Beilstein J. Nanotechnol. 2018, 9, 301–310, doi:10.3762/bjnano.9.30

• background interference intensity and adjusts the height of the cover glass to keep the intensity constant. The feedback-loop can also operate during acquisition with a frequency of 20 Hz as illustrated by the red lines in Figure 2e. The blue lines indicate the measured laterally averaged gap distances for

• distance by 1 nm every 10th frame. (d) Effective gap distance variation Δd in the nanofluidic slit obtained from the local variation in optical path difference. (e) The height of the cover glass (red) is adjusted by a feedback loop to ensure a constant gap distance (blue) during experiments. (a) Contrast

Anchoring of a dye precursor on NiO(001) studied by non-contact atomic force microscopy

• Sara Freund,
• Antoine Hinaut,
• Nathalie Marinakis,
• Edwin C. Constable,
• Ernst Meyer,
• Catherine E. Housecroft and
• Thilo Glatzel

Beilstein J. Nanotechnol. 2018, 9, 242–249, doi:10.3762/bjnano.9.26

• of recording a first scan line with a closed feedback loop where the tip–sample distance is regulated using a topographic set point Δf1 and then acquiring a second scan in a open feedback loop following the recorded topography but applying an additional constant Z-offset, reducing the tip–sample

Combined scanning probe electronic and thermal characterization of an indium arsenide nanowire

• Tino Wagner,
• Fabian Menges,
• Heike Riel,
• Bernd Gotsmann and
• Andreas Stemmer

Beilstein J. Nanotechnol. 2018, 9, 129–136, doi:10.3762/bjnano.9.15

• we detect modulations of the force gradient from the sidebands of the drive frequency fd in the deflection signal. The sidebands at fd ± fm are minimized by matching the dc tip bias to Ulcpd using a feedback loop. The sidebands at fd ± 2fm are proportional to the tip–sample capacitance gradient C

• ′′ and the KFM sensitivity. The feedback loop in our setup uses both pairs of sidebands and a Kalman filter to continuously estimate the surface potential and to avoid topographical artefacts [20]. Scanning thermal measurements of the InAs nanowire. (a) Setup for SThM measurements. (b) Topography and

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

• , 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

• of the Young’s modulus of the FDTS monolayer. Feedback loops necessary to track the flexural contact resonances of the cantilever. The main feedback loop ensures that the measurements are performed with a constant normal force. The other feedback loops are used to maintain constant values of phase 1

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

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

• loop is turned off. Then we approach the tip to the target SiNR while measuring the conductance G at the sample voltage of 100 mV as a function of tip vertical position (Z). We set the position where the tip is fixed initially as Z = 0. Once the tip touches the target, we retract the tip to lift up 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

• -amplitude set-point to the free amplitude, Aset/Afree, based on a priori measured relation between dTM−d and (Adef/Afree) [1]. An online data-driven iterative feedforward controller is integrated to the RMS-z-feedback loop to enhance the sample topography tracking (Figure 9). Particularly, the feedforward

• ]. As the TM-deflection responds much faster than the RMS tapping-amplitude to the sample topography variation, so the inner-outer loop feedback control of the TM-deflection is faster than that of the RMS tapping amplitude. Moreover, the TM-deflection feedback loop facilitates the regulation of the

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

• amplitude estimate as a function of the tracking bandwidth. The experimental analysis is concluded by high-speed constant-height tapping-mode AFM experiments which highlight the case where the demodulator is the bandwidth bottleneck in the z-axis feedback loop. Fundamentals of amplitude modulation and