Dual-heterodyne Kelvin probe force microscopy

• Benjamin Grévin,
• Fatima Husainy,
• Dmitry Aldakov and
• Cyril Aumaître

Beilstein J. Nanotechnol. 2023, 14, 1068–1084, doi:10.3762/bjnano.14.88

• time-periodic surface electrostatic potential generated under optical (or electrical) pumping with an atomic force microscope. The modulus and phase coefficients are probed by exploiting a double heterodyne frequency mixing effect between the mechanical oscillation of the cantilever, modulated

• components of the time-periodic electrostatic potential at harmonic frequencies of the pump, and an ac bias modulation signal. Each harmonic can be selectively transferred to the second cantilever eigenmode. We show how phase coherent sideband generation and signal demodulation at the second eigenmode can be

• with the application of a light pulse (i.e., a curve is recorded at each point of the surface along a 2D grid). Again, a differential SPV image can be reconstructed from the matrix of spectroscopic curves [5]. However, this approach is not free from artefacts, in particular the cantilever photothermal

Spatial mapping of photovoltage and light-induced displacement of on-chip coupled piezo/photodiodes by Kelvin probe force microscopy under modulated illumination

• Zeinab Eftekhari,
• Nasim Rezaei,
• Hidde Stokkel,
• Jian-Yao Zheng,
• Andrea Cerreta,
• Ilka Hermes,
• Minh Nguyen,
• Guus Rijnders and
• Rebecca Saive

Beilstein J. Nanotechnol. 2023, 14, 1059–1067, doi:10.3762/bjnano.14.87

• KPFM shown in Figure 1a illustrates multiple lock-in amplifiers employed to excite the cantilever both mechanically and electrically at the same time, and to retrieve simultaneously the amplitude and phase of the movement of the cantilever at different frequencies. The cantilever is excited at its

• the cantilever resonance. Modulating the tip with VAC while the cantilever is oscillating near its resonance frequency leads to frequency mixing and intermodulation of the two frequencies (f0 ± fAC) [34]. The lock-in amplifiers 2 and 3 are fed with the vertical deflection signal of the cantilever to

• measure the sideband signals at f0 + fAC and f0 − fAC. Then, their average is used for the KPFM feedback to adjust the DC bias. If fAC is chosen to be small enough, such that the sideband peaks are close to f0, the amplitude of these peaks will be enhanced by the mechanical resonance of the cantilever

Exploring internal structures and properties of terpolymer fibers via real-space characterizations

• Michael R. Roenbeck and
• Kenneth E. Strawhecker

Beilstein J. Nanotechnol. 2023, 14, 1004–1017, doi:10.3762/bjnano.14.83

• N/m (nominal), k = 12–21 N/m (measured)) were used for AFM scans. By simultaneously exciting the AFM cantilever to its first and second resonance (f1 = 160–190 kHz and f2 = 900–1150 kHz, Figure 1c) and applying two distinct control conditions (amplitude modulation (AM) and frequency modulation (FM

• . Dashed line highlights a shear plane between the two notches. The fiber readily opens along this plane, exposing internal fiber surfaces for characterization. (c) Multifrequency AFM schematic. A cantilever is driven by a blue laser that simultaneously excites the cantilever at its first and second

• resonance frequencies (f1 and f2). The response of the cantilever as it scans across the exposed internal fiber surface provides information about the local fiber internal morphology and mechanical response (stiffness and transverse elastic modulus (ET)). Fiber-wide Technora® AFM maps. (a) Topography map

Cross-sectional Kelvin probe force microscopy on III–V epitaxial multilayer stacks: challenges and perspectives

• Mattia da Lisca,
• José Alvarez,
• James P. Connolly,
• Nicolas Vaissiere,
• Karim Mekhazni,
• Jean Decobert and
• Jean-Paul Kleider

Beilstein J. Nanotechnol. 2023, 14, 725–737, doi:10.3762/bjnano.14.59

• the cantilever are reduced, as well as the effect of parasitic capacitances [16]. Additionally, in FM-KPFM, surface potential measurements are less dependent on the lift-height tip–sample distance than in AM-KPFM since this mode is less sensitive to static offsets induced by capacitive coupling or

• + dc potential is applied, the KPFM tip scans across a surface. The ac signal is sinusoidal with a frequency that equals the mechanical resonance of the cantilever. The four-quadrant detector gives feedback in order to minimize cantilever oscillation modifying the dc signal providing the sample surface

High–low Kelvin probe force spectroscopy for measuring the interface state density

• Ryo Izumi,
• Masato Miyazaki,
• Yan Jun Li and
• Yasuhiro Sugawara

Beilstein J. Nanotechnol. 2023, 14, 175–189, doi:10.3762/bjnano.14.18

• advantages, namely high sensitivity to the electrostatic force gradient, high detection sensitivity using a cantilever with a weak spring constant at the first resonance, ease of implementation in adding FM-AFM, and no need to enhance the bandwidth of the cantilever deflection sensor. FM-KPFM is used to

• apply an AC bias voltage at frequencies lower than the cutoff frequency fc of carrier transport, and heterodyne FM-KPFM, based on the heterodyne effect (frequency conversion effect) between mechanical oscillation of the cantilever and electrostatic force oscillation, is used to apply an AC bias voltage

• vibrating cantilever are A and f0, respectively. The time-varying tip–sample distance is given by From this equation and the relationship Cg = ε0/z, we obtain the following expression: Because of frequency mixing between the electrostatic force due to the AC bias voltage cos 2πfmt and the cantilever

Intermodal coupling spectroscopy of mechanical modes in microcantilevers

• Ioan Ignat,
• Bernhard Schuster,
• Jonas Hafner,
• MinHee Kwon,
• Daniel Platz and
• Ulrich Schmid

Beilstein J. Nanotechnol. 2023, 14, 123–132, doi:10.3762/bjnano.14.13

• opportunity to bring intermodal coupling techniques, derived from optomechanics, to AFM. It is easily accessible, with no hardware modifications and only requiring multifrequency excitation applied to the cantilever by either a piezoshaker or a modulated laser, found in many AFM setups. The field of

• excitation of the first mode of a cantilever with measurements being performed at its harmonics [37]. Another method involved clever designs such as T-shaped cantilevers [38] and inner-paddled cantilevers [39] aiming at reducing the noise impact on force reconstruction. Bimodal AFM is another addition to the

• field, where two eigenmodes are excited and read simultaneously [40]. Last, intermodulation products, created by two signals close to the fundamental cantilever mode, form a sea of evenly spaced tones to be measured [35][41][42]. All of these rely on the nonlinear tip–surface force to create these

Characterisation of a micrometer-scale active plasmonic element by means of complementary computational and experimental methods

• Ciarán Barron,
• Giulia Di Fazio,
• Samuel Kenny,
• Silas O’Toole,
• Robin O’Reilly and
• Dominic Zerulla

Beilstein J. Nanotechnol. 2023, 14, 110–122, doi:10.3762/bjnano.14.12

• plasmonic response. This heating also results in thermal expansion of the element. This expansion will result in deflection of an AFM cantilever scanning the surface. If a sinusoidal voltage is applied to an electrically conducting sample, such as the active plasmonic element discussed here, the resulting

• nanomechanical operations such as lithography and machining. The high spring constant of this cantilever has the advantage of minimising the unwanted deflection of the cantilever resulting from electrostatic interaction of the potential on the surface and the probe. The tip is constructed from wear-resistant

• Cypher AFM. This frequency is also well below the resonance frequency of the selected cantilever avoiding unwanted resonant oscillations in the cantilever as a result of the periodic force applied by the expanding surface when deflecting the cantilever. In principle, the drive frequency of the active

Frequency-dependent nanomechanical profiling for medical diagnosis

• Santiago D. Solares and
• Alexander X. Cartagena-Rivera

Beilstein J. Nanotechnol. 2022, 13, 1483–1489, doi:10.3762/bjnano.13.122

• optical imaging, the device could be equipped with one or more piezoelectrically excited membranes coupled with a sensing mechanism, such as an AFM cantilever or other type of mechanical sensor (similar stand-alone developments already exist [31][32]). The mechanical response of the membrane could be

Studies of probe tip materials by atomic force microscopy: a review

• Ke Xu and
• Yuzhe Liu

Beilstein J. Nanotechnol. 2022, 13, 1256–1267, doi:10.3762/bjnano.13.104

• . Applications range from mechanical and electrical sample characterization to measurements in liquids [1][2][3][4] and even in living cells [5][6][7][8]. The critical element of an AFM is the scanning probe itself, which is usually represented by a micro-cantilever beam equipped with a conical scanning tip. As

• the tip approaches the sample surface, an interaction force is generated that deflects (bends or stretches) the probe cantilever. As the AFM probe moves across the sample surface (in the X and Y directions), morphological information is obtained over the entire scan area. Its tip structure and the

• mechanical properties of the cantilever beam directly affect the performance, measurement resolution, and image quality of the AFM instrument. AFM probe tips [9][10] are generally fabricated with coatings, carbon nanotubes, magnetic nanoparticles, or even protein functionalization. A combination of probe

A cantilever-based, ultrahigh-vacuum, low-temperature scanning probe instrument for multidimensional scanning force microscopy

• Hao Liu,
• Zuned Ahmed,
• Sasa Vranjkovic,
• Manfred Parschau,
• Andrada-Oana Mandru and
• Hans J. Hug

Beilstein J. Nanotechnol. 2022, 13, 1120–1140, doi:10.3762/bjnano.13.95

• Cantilever-based atomic force microscopy (AFM) performed under ambient conditions has become an important tool to characterize new material systems as well as devices. Current instruments permit robust scanning over large areas, atomic-scale lateral resolution, and the characterization of various sample

• tuning fork force sensor became increasingly popular. In comparison to microfabricated cantilevers, the more macroscopic tuning forks, however, lack sensitivity, which limits the measurement bandwidth. Moreover, multimodal and multifrequency techniques, such as those available in cantilever-based AFM

• carried out under ambient conditions, are challenging to implement. In this article, we describe a cantilever-based low-temperature UHV AFM setup that allows one to transfer the versatile AFM techniques developed for ambient conditions to UHV and low-temperature conditions. We demonstrate that such a

Comparing the performance of single and multifrequency Kelvin probe force microscopy techniques in air and water

• Jason I. Kilpatrick,
• Emrullah Kargin and
• Brian J. Rodriguez

Beilstein J. Nanotechnol. 2022, 13, 922–943, doi:10.3762/bjnano.13.82

• first two eigenmodes of the cantilever. These comparisons allow the reader to quickly and quantitatively identify the parameters for the best performance for a given KPFM-based experiment in a given environment. Furthermore, we apply these performance metrics in the identification of KPFM-based modes

• forces in KPFM is generally expressed as the minimum detectable CPD [53], and is directly limited by the geometry of the interaction, thermal noise of the cantilever, and the detection noise limits of the AFM [36][54]. Cantilevers have a number of eigenmodes, ωn, where there is a mechanical enhancement

• to ωn where ∝ Qn/kn and there is a significant enhancement in the oscillation amplitude of the cantilever in response to the electrostatic force, thereby increasing the signal-to-noise ratio (SNR) [10]. In this paper we define the SNR as the ratio of the measured signal (oscillation amplitude of the

Temperature and chemical effects on the interfacial energy between a Ga–In–Sn eutectic liquid alloy and nanoscopic asperities

• Yujin Han,
• Pierre-Marie Thebault,
• Corentin Audes,
• Xuelin Wang,
• Haiwoong Park,
• Jian-Zhong Jiang and
• Arnaud Caron

Beilstein J. Nanotechnol. 2022, 13, 817–827, doi:10.3762/bjnano.13.72

• force–distance curve with each cantilever on a quartz glass sample (manufactured by Goodfellow, United Kingdom) and extracting its slope in the range of repulsive forces. Subsequently, we determined the bending stiffness Cn of each cantilever by analyzing its thermal noise vibration [18]. After

• consisted of approaching a cantilever towards the sample surface at varying velocities dZ/dt = 0.1–25 µm/s (see Figure 1). We repeated force spectroscopy measurements at each approach/retraction velocity 15 times. We used the retraction part of the force–distance curves to determine the adhesion force Fad

• hysteresis for the normal force is not as straightforward to explain. In our experiments, we can exclude the effect of crosstalk due to misalignment of the cantilever since we mounted each cantilever on the same alignment chip on the cantilever holder. We consider it more likely that the hysteresis of the

Optimizing PMMA solutions to suppress contamination in the transfer of CVD graphene for batch production

• Chun-Da Liao,
• Andrea Capasso,
• Tiago Queirós,
• Telma Domingues,
• Fatima Cerqueira,
• Nicoleta Nicoara,
• Jérôme Borme,
• Paulo Freitas and
• Pedro Alpuim

Beilstein J. Nanotechnol. 2022, 13, 796–806, doi:10.3762/bjnano.13.70

• frequency. The AFM measurement was carried out in tapping mode. A 633 nm laser light aimed at the back side of the cantilever tip was reflected toward a position-sensitive photodetector, which provides feedback signals to piezoelectric scanners that maintain the cantilever tip at constant height (force

Gelatin nanoparticles with tunable mechanical properties: effect of crosslinking time and loading

• Agnes-Valencia Weiss,
• Daniel Schorr,
• Julia K. Metz,
• Metin Yildirim,
• Saeed Ahmad Khan and
• Marc Schneider

Beilstein J. Nanotechnol. 2022, 13, 778–787, doi:10.3762/bjnano.13.68

• same day. AFM measurements were carried out with a JPK NanoWizard® 3 AFM (JPK Instruments, Berlin, Germany) using the MLCT cantilever tip D (Bruker France Nano Surfaces, Wissembourg, France) with a nominal resonance frequency of 15 kHz and a spring constant of 0.03 N/m. Before each measurement, the

• actual sensitivity and the spring constant of the used cantilever were calibrated on a cleaned silica wafer by the thermal noise method by Hutter et al. [27] using a correction factor of 0.251. The data was acquired using the quantitative imaging mode (QI™) with image sizes of 5 × 5 µm and a resolution

• single nanoparticles. For the values of Young’s moduli, the respective curves were treated as follows: The determined spring constant and sensitivity must be applied to calibrate the cantilever deflection. To correct the vertical offset, a baseline subtraction is applied, and the contact point is

Direct measurement of surface photovoltage by AC bias Kelvin probe force microscopy

• Masato Miyazaki,
• Yasuhiro Sugawara and
• Yan Jun Li

Beilstein J. Nanotechnol. 2022, 13, 712–720, doi:10.3762/bjnano.13.63

• force This signal is measured with a lock-in amplifier and compensated by VAC control, yielding the SPV value. To improve the sensitivity, ωm is usually tuned to the second (first) resonance frequency of the cantilever, while the first (second) resonance frequency is assigned to the AFM measurement [29

• -AFM was operated in the FM mode [32] with a constant oscillation amplitude A of 500 pm. The cantilever deflection was measured by an optical beam deflection (OBD) method [33]. AC-KPFM was carried out in the FM mode, in which the topography and SPV were measured simultaneously. An AC bias VAC with

• was arranged in front of a photodetector of the OBD system to suppress the influence of the UV light on the deflection sensor. We used a commercial Ir-coated Si cantilever (NANOSENSORS, SD-T7L100) with a resonant frequency f0 of 913 kHz, a spring constant k of 650 N/m, and a quality factor Q of 7748

Quantitative dynamic force microscopy with inclined tip oscillation

• Philipp Rahe,
• Daniel Heile,
• Reinhard Olbrich and
• Michael Reichling

Beilstein J. Nanotechnol. 2022, 13, 610–619, doi:10.3762/bjnano.13.53

• measuring a heterogeneous atomic surface. We propose to measure the AFM observables along a path parallel to the oscillation direction in order to reliably recover the force along this direction. Keywords: atomic force microscopy; cantilever; quantitative force measurement; sampling path; Introduction

• for technical reasons. Consequences of this inclined AFM cantilever mount have been identified before, in particular for atomic force microscopy performed in static (“contact”) mode where an effective spring constant [6][7][8] has been introduced and a torque [9][10] as well as load [11] correction

• has been applied. Additionally, a tilted cantilever has been found to lead to a modification of the tip–sample convolution [12], to enhance the sensitivity of the measurement to the probe side [13], and to influence results of multifrequency AFM and Kelvin probe force microscopy [14]. In the presence

Effects of substrate stiffness on the viscoelasticity and migration of prostate cancer cells examined by atomic force microscopy

• Xiaoqiong Tang,
• Yan Zhang,
• Jiangbing Mao,
• Yuhua Wang,
• Zhenghong Zhang,
• Zhengchao Wang and
• Hongqin Yang

Beilstein J. Nanotechnol. 2022, 13, 560–569, doi:10.3762/bjnano.13.47

• Germany) for 2 h to prevent damage to the cells. Before the experiment, the thermal noise method was used to adjust the cantilever spring constant, and then the experiment was carried out in contact mode. The AFM probe (MLCT probe, Bruker, USA) slightly contacted the cell surface and a constant force was

Electrostatic pull-in application in flexible devices: A review

• Teng Cai,
• Yuming Fang,
• Yingli Fang,
• Ruozhou Li,
• Ying Yu and
• Mingyang Huang

Beilstein J. Nanotechnol. 2022, 13, 390–403, doi:10.3762/bjnano.13.32

• the first time. They used single-walled carbon nanotubes (SWCNTs) to prepare a suspended cross bistable switch array. Table 1 summarizes the structures and the voltage of CNT-NEM switches described in the literature. In addition to bridge and cantilever structures, the vertical structure further

• the critical voltage is about 3.6 V. Abbasi et al. [2] prepared a bistable switch based on SWCNTs, with a pull-in voltage of 2.5–3 V, which is suitable for nonvolatile memory applications. Cantilever model: A typical cantilever structure is shown in Figure 2b. Lee et al. [22][23] prepared a three

• -terminal cantilever MWCNT NEM switch. The diameter of the CNTs is 50 nm, the length is 2 µm, and the gap is 150 nm. When Vds is 0.5 V, Vgs is in the range of 6–30 V. Loh et al. [24] prepared a cantilever SWCNT and diamond electrode structure with a pull-in voltage of 23.4 V. C–C bonds can greatly improve

Relationship between corrosion and nanoscale friction on a metallic glass

• Haoran Ma and
• Roland Bennewitz

Beilstein J. Nanotechnol. 2022, 13, 236–244, doi:10.3762/bjnano.13.18

• corrosive solution was added. For these experiments, we used an electrochemical atomic force microscope (ECAFM, Agilent 5500) and the oxidized tip (radius of ca. 30 nm) of a single-crystalline Si cantilever (PPP-CONT, NanoSensors, Germany). We adopted the beam geometry method to calibrate the force

• constants of the cantilever [47]. The resonance frequency of the cantilever at the first normal oscillation mode measured in the air was used to calculate the thickness of the cantilever [47]. The AFM tip sliding velocity was 8.0 μm·s−1 and the scan field was 1.0 × 0.125 μm2. Sixteen cycles of repetitive

Measurement of polarization effects in dual-phase ceria-based oxygen permeation membranes using Kelvin probe force microscopy

• Kerstin Neuhaus,
• Christina Schmidt,
• Liudmila Fischer,
• Wilhelm Albert Meulenberg,
• Ke Ran,
• Joachim Mayer and
• Stefan Baumann

Beilstein J. Nanotechnol. 2021, 12, 1380–1391, doi:10.3762/bjnano.12.102

• were performed in a single-pass experiment. For this kind of measurements, the surface potential and the sample topography are mapped in a single pass in intermittent contact mode with the cantilever vibrating at its resonance frequency (i.e., the cantilever is not in lift mode during this experiment

Alteration of nanomechanical properties of pancreatic cancer cells through anticancer drug treatment revealed by atomic force microscopy

• Xiaoteng Liang,
• Shuai Liu,
• Xiuchao Wang,
• Dan Xia and
• Qiang Li

Beilstein J. Nanotechnol. 2021, 12, 1372–1379, doi:10.3762/bjnano.12.101

• characterized by AFM is shown in Figure 1. For the mechanical mapping, the AFM cantilever needs to be calibrated first. During the scanning process, the applied force should be less than 3 nN to prevent cell destruction. For force mapping, 400 force curves were collected for each selected area and at least 30

Cantilever signature of tip detachment during contact resonance AFM

• Devin Kalafut,
• Ryan Wagner,
• Maria Jose Cadena,
• Anil Bajaj and
• Arvind Raman

Beilstein J. Nanotechnol. 2021, 12, 1286–1296, doi:10.3762/bjnano.12.96

• atomic force microscopy modes in which the cantilever is held in contact with the sample at a constant average force while monitoring the cantilever motion under the influence of a small, superimposed vibrational signal. Though these modes depend on permanent contact, there is a lack of detailed analysis

• on how the cantilever motion evolves when this essential condition is violated. This is not an uncommon occurrence since higher operating amplitudes tend to yield better signal-to-noise ratio, so users may inadvertently reduce their experimental accuracy by inducing tip–sample detachment in an effort

• to improve their measurements. We shed light on this issue by deliberately pushing both our experimental equipment and numerical simulations to the point of tip–sample detachment to explore cantilever dynamics during a useful and observable threshold feature in the measured response. Numerical

Enhancement of the piezoelectric coefficient in PVDF-TrFe/CoFe₂O₄ nanocomposites through DC magnetic poling

• Marco Fortunato,
• Alessio Tamburrano,
• Maria Paola Bracciale,
• Maria Laura Santarelli and
• Maria Sabrina Sarto

Beilstein J. Nanotechnol. 2021, 12, 1262–1270, doi:10.3762/bjnano.12.93

• through PFM [1][5][27] using a commercial Bruker-Veeco Dimension Icon AFM with a Co/Cr-coated-tip silicon cantilever (MESP-RC-V2, Bruker). Following the procedure described in [2][3], we scanned three different areas, 5 × 5 μm2 in size, of each sample, with 256 × 256 acquisition points per scanning area

Two dynamic modes to streamline challenging atomic force microscopy measurements

• Alexei G. Temiryazev,
• Andrey V. Krayev and
• Marina P. Temiryazeva

Beilstein J. Nanotechnol. 2021, 12, 1226–1236, doi:10.3762/bjnano.12.90

• tip and to visualize the contamination there. Such a sample is available in any AFM laboratory and allows one to demonstrate some of the features that make it difficult to work in standard modes. On the one hand, next to the scan area, there is a high console of the cantilever; on the other hand

• parameters: 256 by 256 points, A0 = 10 nm, Tline = 0.5 s, Tdir = 0.4 s, Vup = 5 µm/s, Vdown = 2 µm/s, p1 = 70%, p2 = p1 + 4%. We used a Mikromasch NSC15 cantilever with a nominal force constant 46 N/m and resonance frequency of 328 kHz. This scan took Tscan = 6 min. Figure 3b shows the time spent on the

Open-loop amplitude-modulation Kelvin probe force microscopy operated in single-pass PeakForce tapping mode

• Gheorghe Stan and
• Pradeep Namboodiri

Beilstein J. Nanotechnol. 2021, 12, 1115–1126, doi:10.3762/bjnano.12.83

• the measured electrical tip–sample interaction is directly affixed to the topography rendered by the mechanical PFT modulation at each tap. Furthermore, because the detailed response of the cantilever to the bias stimulation was recorded, it was possible to analyze and separate an average contribution

• of the cantilever to the determined local contact potential difference between the AFM probe and the imaged sample. The removal of this unwanted contribution greatly improved the accuracy of the AM-KPFM measurements to the level of the FM-KPFM counterpart. Keywords: electrostatic interaction; Kelvin

• -excitation OL BE-KPFM [37][38][39], intermodulation electrostatic force microscopy [40], and dual-harmonic KPFM (DH-KPFM) [34][41][42]. In DH-KPFM, the CPD is obtained from the ratio of the amplitudes of the first two harmonics of the cantilever response to an AC bias modulation and requires a prior