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

• improvements in bandwidth or resonance frequency of all of the components constituting the tip–sample distance regulation loop, such as the cantilever, cantilever excitation unit, cantilever deflection sensor, scanner, feedback controller, and phase-locked loop (PLL) circuit. In particular, the PLL circuit is

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

• detecting the electrostatic frequency modulation is to use non-linear frequency mixing with a mechanical cantilever oscillation at angular frequency ωm, such as the tapping oscillation used for the height feedback [36]. As the capacitance gradient monotonically decreases away from the surface, it will also

• cantilevers was ≈225 μm, the width ≈35 μm. Tip, tip cone and cantilever are coated with PtIr (work function 5.5 eV [39]) on both sides. The topography feedback was performed with amplitude modulation (AM) on the first eigenmode and the oscillation amplitude was kept to approximately 40 nm for all methods. To

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

Electrostatically actuated encased cantilevers

• Benoit X. E. Desbiolles,
• Gabriela Furlan,
• Adam M. Schwartzberg,
• Paul D. Ashby and
• Dominik Ziegler

Beilstein J. Nanotechnol. 2018, 9, 1381–1389, doi:10.3762/bjnano.9.130

• an annealed ultra-flat gold surface. The surface is imaged in tapping mode using harmonic excitation with amplitude modulation feedback, a free amplitude of 1 nm and a set-point of 0.8 nm. In harmonic excitation, we observe that intentional switching of the applied Udc by a few volts would result in

• ) Topographic image of copper grains evaporated onto an annealed ultra-flat gold surface. The image is recorded in air using electrostatic excitation with amplitude modulation feedback and a free amplitude of 1 nm and set-point of 0.8 nm. a) Oscillation amplitude at the resonance frequency of the cantilever

Artifacts in time-resolved Kelvin probe force microscopy

• Sascha Sadewasser,
• Nicoleta Nicoara and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2018, 9, 1272–1281, doi:10.3762/bjnano.9.119

• the Fermi level, affecting the work function, which is defined as the energy difference between the local vacuum level and the Fermi level [12]. Usually, KPFM is used as a slow technique aiming at imaging local variations in the CPD. The KPFM feedback circuit applies a dc voltage to the tip (or the

• simulation results. Furthermore, additional artifacts are observed due to an undesired influence on the z feedback controller and on the photodiode of the beam-deflection system in case of light modulation. Results and Discussion Simulations Numerical simulations of the cantilever motion were performed using

• -detection voltage and VCPD the contact potential difference. In our numerical simulations, no z feedback is considered and the z position of the cantilever tip is only influenced by electrostatic forces. This was done in order to focus on the effect of the electrostatic forces. To realize time-resolved KPFM

Field-controlled ultrafast magnetization dynamics in two-dimensional nanoscale ferromagnetic antidot arrays

• Anulekha De,
• Sucheta Mondal,
• Sourav Sahoo,
• Saswati Barman,
• Yoshichika Otani,
• Rajib Kumar Mitra and
• Anjan Barman

Beilstein J. Nanotechnol. 2018, 9, 1123–1134, doi:10.3762/bjnano.9.104

• stage, which gives high stability to the sample in the presence of feedback loops. The pump beam was chopped at 2 kHz frequency, and the phase-sensitive detection of the Kerr rotation and reflectivity were performed using lock-in amplifiers and an optical bridge detector at room temperature. A variable

Magnetic characterization of cobalt nanowires and square nanorings fabricated by focused electron beam induced deposition

• Federico Venturi,
• Gian Carlo Gazzadi,
• Amir H. Tavabi,
• Alberto Rota,
• Rafal E. Dunin-Borkowski and
• Stefano Frabboni

Beilstein J. Nanotechnol. 2018, 9, 1040–1049, doi:10.3762/bjnano.9.97

• a two-dimensional magnetization map can be recorded. MFM analysis was performed with a VEECO EnviroScope system, working in tapping mode with amplitude detection feedback. The MFM maps were acquired in two-pass lift-mode, with the magnetic signal collected about 30 nm above the surface. The probe

Nanoscale mapping of dielectric properties based on surface adhesion force measurements

• Ying Wang,
• Yue Shen,
• Xingya Wang,
• Zhiwei Shen,
• Bin Li,
• Jun Hu and
• Yi Zhang

Beilstein J. Nanotechnol. 2018, 9, 900–906, doi:10.3762/bjnano.9.84

• AFM tip changed very little, which is quite different from the result in our previous SPFM experiment, in which the apparent height of RGO sheets under a biased tip usually increased sharply when RH was lower than 40% [32]. This is because the set point of the force, which is used as the feedback

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

• , enabling both z-axis feedback and phase contrast imaging to be achieved. This article proposes a model-based multifrequency Lyapunov filter implemented on a field-programmable gate array (FPGA) for high-speed MF-AFM demodulation. System descriptions and simulations are verified by experimental results

• interactions [2], atomic scale resolution imaging is achieved, which far exceeds the optical diffraction limit. An image generated by constant-force topography AFM depends entirely on its feedback control loop. The composition of a sample is visualized in three-dimensions by plotting the control signal against

• 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

High-contrast and reversible scattering switching via hybrid metal-dielectric metasurfaces

• Jonathan Ward,
• Khosro Zangeneh Kamali,
• Lei Xu,
• Guoquan Zhang,
• Andrey E. Miroshnichenko and
• Mohsen Rahmani

Beilstein J. Nanotechnol. 2018, 9, 460–467, doi:10.3762/bjnano.9.44

• , respectively. The polarization of the incident beam is along y direction (along the gold bar lengths). A grating resonance in the spectrum occurs around 1235 nm at the grating diffraction edge (λ0 = n × D = 1.45 × 850 nm = 1232.5 nm) due to the constructive diffractive feedback among neighbouring antennas

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

• of the nanofluidic confinement apparatus. We vary the gap distance for different measurements and then use the feedback-control loop to keep it constant (see Figure 2e) while acquiring frames for 15 s. The number of particles in the field of view reduces with decreasing gap distance. In our

• 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

Liquid-crystalline nanoarchitectures for tissue engineering

• Baeckkyoung Sung and
• Min-Ho Kim

Beilstein J. Nanotechnol. 2018, 9, 205–215, doi:10.3762/bjnano.9.22

• the cell density estimated in human connective tissues. Additionally, the mechanical feedback from the matrix to the cell body could stimulate the development of myofibroblast phenotype. This implicates that the LC matrix of dense collagen fibrils can be used as a biocompatible and biodegradable 3D

• factors (2D/3D topography and mechanical stiffness) and the biochemical factors (cell binding and molecular stimulation). The mechanical feedback from the scaffold is transmitted to the cell nucleus (N) via actin bundles (stress fibers). The chemical signal is generated by growth factors and then

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

• topography, geometrical artefacts and feedback problems can be minimized by appropriate control schemes [20]. The typical lateral resolution of our SThM and KFM setups is on the order of the tip radius (below 10 nm), at a noise level of 20 μK·Hz−0.5 and 1 mV·Hz−0.5, respectively, depending on operating

• 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

• 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