Stiffness calibration of qPlus sensors at low temperature through thermal noise measurements

• Laurent Nony,
• Sylvain Clair,
• Daniel Uehli,
• Aitziber Herrero,
• Jean-Marc Themlin,
• Andrea Campos,
• Franck Para,
• Alessandro Pioda and
• Christian Loppacher

Beilstein J. Nanotechnol. 2024, 15, 580–602, doi:10.3762/bjnano.15.50

• , the technique mostly employs QTFs, based on the so-called qPlus design, which actually covers different types of sensors in terms of size and design of the electrodes. They all have in common a QTF featuring a metallic tip glued at the free end of one of its prongs. In this study, we report the

• stiffness calibration of a particular type of qPlus sensor in UHV and at 9.8 K by means of thermal noise measurements. The stiffness calibration of such high-k sensors, featuring high quality factors (Q) as well, requires to master both the acquisition parameters and the data post-processing. Our approach

• relies both on numerical simulations and experimental results. A thorough analysis of the thermal noise power spectral density of the qPlus fluctuations leads to an estimated stiffness of the first flexural eigenmode of ≃2000 N/m, with a maximum uncertainty of 10%, whereas the static stiffness of the

Design, fabrication, and characterization of kinetic-inductive force sensors for scanning probe applications

• August K. Roos,
• Ermes Scarano,
• Elisabet K. Arvidsson,
• Erik Holmgren and
• David B. Haviland

Beilstein J. Nanotechnol. 2024, 15, 242–255, doi:10.3762/bjnano.15.23

• superconducting cavity read-out scheme is intrinsically low noise. Compared to other low-temperature AFM probes, such as the qPlus sensor [42], our versatile design allows for achieving a wide variety of the parameters of the mechanical mode (force transducer) with a much lower effective mass and, consequently

From a free electron gas to confined states: A mixed island of PTCDA and copper phthalocyanine on Ag(111)

• Alfred J. Weymouth,
• Emily Roche and
• Franz J. Giessibl

Beilstein J. Nanotechnol. 2022, 13, 1572–1577, doi:10.3762/bjnano.13.131

• of the sample preparation is available in Supporting Information File 1. A qPlus AFM/STM sensor [21] with an etched W-tip was used. Tunneling spectoscopy data (dI/dV data) were acquired with a lock-in amplifier included in the control electronics (Nanonis from SPECS GmbH). The AC signal had a

Topographic signatures and manipulations of Fe atoms, CO molecules and NaCl islands on superconducting Pb(111)

• Carl Drechsel,
• Philipp D’Astolfo,
• Jung-Ching Liu,
• Thilo Glatzel,
• Rémy Pawlak and
• Ernst Meyer

Beilstein J. Nanotechnol. 2022, 13, 1–9, doi:10.3762/bjnano.13.1

• temperature in the preparation chamber. Low-temperature scanning tunneling microscope The experiments were performed using a low-temperature STM/AFM microscope (T = 4.8 K) from Omicron GmbH in UHV (p ≈ 1 × 10−10 mbar) operated with Nanonis RC5 electronics. The sensor is a tuning fork sensor in a qPlus design

• [47] operated in the frequency-modulation mode (resonance frequency f0 ≈ 25 kHz, spring constant k ≈ 1800 N/m, quality factor Q ≈ 14000, and oscillation amplitude A ≈ 0.5 Å). The tip mounted to the qPlus sensor consists of a 25 μm-thick PtIr wire, shortened and sharpened with a focused ion beam. A

Reducing molecular simulation time for AFM images based on super-resolution methods

• Zhipeng Dou,
• Jianqiang Qian,
• Yingzi Li,
• Rui Lin,
• Jianhai Wang,
• Peng Cheng and
• Zeyu Xu

Beilstein J. Nanotechnol. 2021, 12, 775–785, doi:10.3762/bjnano.12.61

• and 0.1 Å vertical resolution [3]. Then, functionalizing the tip with closed-shell molecules and using a qPlus force sensor enabled the imaging of the internal structure of the molecules [4][5][6][7], resolving features of weak-bonded molecules [8][9][10][11][12], and measurement of bond-order

Local stiffness and work function variations of hexagonal boron nitride on Cu(111)

• Abhishek Grewal,
• Yuqi Wang,
• Matthias Münks,
• Klaus Kern and
• Markus Ternes

Beilstein J. Nanotechnol. 2021, 12, 559–565, doi:10.3762/bjnano.12.46

• , CH-1015 Lausanne, Switzerland II. Institute of Physics, RWTH Aachen University, D-52074 Aachen, Germany 10.3762/bjnano.12.46 Abstract Combined scanning tunnelling and atomic force microscopy using a qPlus sensor enables the measurement of electronic and mechanic properties of two-dimensional

• . Experimental We employ a custom-built ultrahigh-vacuum (below 10−10 mbar) low-temperature (T = 1.4 K) nc-AFM operated in frequency-modulated mode. A stiff qPlus cantilever design [49] (k0 = 1800 N·m−1, f0 = 29077 Hz, Q = 60000) at an oscillation amplitude Aosc = 50 pm enables the nc-AFM functionality. We

Determining amplitude and tilt of a lateral force microscopy sensor

• Oliver Gretz,
• Alfred J. Weymouth,
• Thomas Holzmann,
• Korbinian Pürckhauer and
• Franz J. Giessibl

Beilstein J. Nanotechnol. 2021, 12, 517–524, doi:10.3762/bjnano.12.42

• ]. This has been used to achieve atomic resolution of a sample that is laterally stiff and vertically soft [5]. It has also been used under ultrahigh-vacuum conditions [6] as well as in liquid to yield atomic resolution [7]. Also in 2002, Giessibl and co-workers performed LFM using a qPlus sensor as shown

• molecular adsorbate [11][12]. Moreover, other methods, including the use of a long tip on a qPlus sensor that oscillates laterally at a higher flexural mode are also possible [13]. In LFM or normal AFM, the recorded frequency shift Δf is related to the force gradient kts in the direction of the tip

• , Germany) operating in ultra-high vacuum at 5.6 K equipped with a qPlus sensor [25]. The sensor was equipped with an etched tungsten tip, which was repeatedly poked into a Cu(111) surface to generate well-defined tip apex configurations. Cu(111) was cleaned by standard sputtering and annealing cycles

Numerical analysis of vibration modes of a qPlus sensor with a long tip

• Kebei Chen,
• Zhenghui Liu,
• Yuchen Xie,
• Chunyu Zhang,
• Gengzhao Xu,
• Wentao Song and
• Ke Xu

Beilstein J. Nanotechnol. 2021, 12, 82–92, doi:10.3762/bjnano.12.7

• Sciences (CAS), Suzhou 215123, China CAS Key Laboratory of Nanophotonic Materials and Devices, Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China 10.3762/bjnano.12.7 Abstract We study the oscillatory behavior of qPlus sensors with a long tilted tip by means of finite element simulations

• . The vibration modes of a qPlus sensor with a long tip are quite different from those of a cantilever with a short tip. Flexural vibration of the tungsten tip will occur. The tip can no longer be considered as a rigid body that moves with the prong of the tuning fork. Instead, it oscillates both

• horizontally and vertically. The vibration characteristics of qPlus sensors with different tip sizes were studied. An optimized tip size was derived from obtained values of tip amplitude, ratio between vertical and lateral amplitude components, output current, and quality factor. For high spatial resolution

PTCDA adsorption on CaF₂ thin films

• Philipp Rahe

Beilstein J. Nanotechnol. 2020, 11, 1615–1622, doi:10.3762/bjnano.11.144

• [27][28][29]. PTCDA molecules were deposited from custom-built Knudsen cells heated to 290–300 °C. Samples were held at room temperature during deposition unless noted otherwise. STM data were acquired at 77 or 5 K using a ScientaOmicron qPlus LT AFM/STM operated by a MATRIX controller and an atom

Protruding hydrogen atoms as markers for the molecular orientation of a metallocene

• Linda Laflör,
• Michael Reichling and
• Philipp Rahe

Beilstein J. Nanotechnol. 2020, 11, 1432–1438, doi:10.3762/bjnano.11.127

• experiments (5 and 77 K) with qPlus sensors as well as at room temperature using silicon cantilevers [22]. Although the NC-AFM tips were not functionalised, i.e., not specifically terminated with atoms or molecules for imaging, we find a very good agreement between the experimental data and probe particle

• determined by considering the B-type epitaxy of the CaF2/CaF1/Si(111) thin films samples, see [22][26] for further details. STM and NC-AFM experiments were conducted at low temperatures (5 and 77 K) in two separate systems. Experiments on bulk crystals were performed using an Omicron LT qPlus gen.III

• instrument (ScientaOmicron GmbH, Taunusstein, Germany), while experiments on thin films used a ScientaOmicron LT qPlus gen.II machine, both operated with a MATRIX controller. W tips attached to tuning fork sensors in qPlus configuration [29] were used in both systems. For the measurements on thin film

Atomic defect classification of the H–Si(100) surface through multi-mode scanning probe microscopy

• Jeremiah Croshaw,
• Thomas Dienel,
• Taleana Huff and
• Robert Wolkow

Beilstein J. Nanotechnol. 2020, 11, 1346–1360, doi:10.3762/bjnano.11.119

• . Methods Experiments were performed using an Omicron LT STM and an Omicron qPlus LT AFM [88][89] system operating at 4.5 K and ultrahigh vacuum (3 × 10−11 Torr). STM tips were electrochemically etched from polycrystalline tungsten wire, resistively heated, and field-evaporated to clean and sharpen the apex

Ion mobility and material transport on KBr in air as a function of the relative humidity

• Dominik J. Kirpal,
• Korbinian Pürckhauer,
• Alfred J. Weymouth and
• Franz J. Giessibl

Beilstein J. Nanotechnol. 2019, 10, 2084–2093, doi:10.3762/bjnano.10.203

• relationship between humidity, water coverage and movement speed, however, is complex. In this study we investigated the surface of KBr, a salt crystal, by using frequency-modulation atomic force microscopy (FM-AFM) using a qPlus sensor [9][10][11]. The aim of our experiments is a qualitative and quantitative

• range for each experiment. Experimental For the experiments we used a custom-designed AFM equipped with a qPlus sensor. The qPlus sensor is a stiff (k = 1800 N/m) self-sensing quartz sensor with a resonance frequency around f0 = 32 kHz. It has enabled unprecedented results in low-temperature AFM, such

• that a qPlus AFM is capable of observing material dissolution [7][15]. These studies show that the high stiffness is beneficial and allows one to use larger tips built from any appropriate tip material and to operate the AFM at small amplitudes without risking jump to contact [7][16][17][18][19]. A

Nitrous oxide as an effective AFM tip functionalization: a comparative study

• Taras Chutora,
• Bruno de la Torre,
• Pingo Mutombo,
• Jack Hellerstedt,
• Jaromír Kopeček,
• Pavel Jelínek and
• Martin Švec

Beilstein J. Nanotechnol. 2019, 10, 315–321, doi:10.3762/bjnano.10.30

• with exposures of 0.5–1.7 L. AFM measurements were performed with a qPlus sensor (resonance frequency ca. 30 kHz; k ≈ 1800 N/m), using an oscillation amplitude of 50 pm. Prior to functionalization, the Pt tip was repeatedly indented into the Au(111) substrate several nanometers deep for sharpening and

Optimizing qPlus sensor assemblies for simultaneous scanning tunneling and noncontact atomic force microscopy operation based on finite element method analysis

• Omur E. Dagdeviren and
• Udo D. Schwarz

Beilstein J. Nanotechnol. 2017, 8, 657–666, doi:10.3762/bjnano.8.70

• , Yale University, New Haven, CT 06520, USA 10.3762/bjnano.8.70 Abstract Quartz tuning forks that have a probe tip attached to the end of one of its prongs while the other prong is arrested to a holder (“qPlus” configuration) have gained considerable popularity in recent years for high-resolution atomic

• numerical analysis of qPlus-style setups without tips, this work quantifies the influence of tip attachment on the operational characteristics of the sensor. The results using finite element modeling show in particular that for setups that include a metallic tip that is connected via a separate wire to

• information, when a conducting probe is attached to the end of the oscillator [5][6][7][8][9][10][11]. Towards this end, microfabricated cantilevers [15][16][17], length-extension resonators [18][19][20], and quartz tuning forks in the so-called “qPlus” configuration, in which one of the prongs of the fork is

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

• similarity to experimental results, and demonstrate how ‘sub-atomic’ contrast can arise from a flexible tip exploring an asymmetric potential created due to the positioning of the surrounding surface atoms. Keywords: NC-AFM; qPlus; sub-atomic; sub-molecular; Introduction Recent developments in low

Length-extension resonator as a force sensor for high-resolution frequency-modulation atomic force microscopy in air

• Hannes Beyer,
• Tino Wagner and
• Andreas Stemmer

Beilstein J. Nanotechnol. 2016, 7, 432–438, doi:10.3762/bjnano.7.38

• [4][5]. Recently, atomic resolution has been achieved with a qPlus sensor in air on potassium bromide and graphite [2][6]. In this paper, we demonstrate the suitability of the piezoelectric self-sensing length-extension resonator (LER) [7][8] for high-resolution FM-AFM imaging in air. The LER has a

Virtual reality visual feedback for hand-controlled scanning probe microscopy manipulation of single molecules

• Philipp Leinen,
• Matthew F. B. Green,
• Taner Esat,
• Christian Wagner,
• F. Stefan Tautz and
• Ruslan Temirov

Beilstein J. Nanotechnol. 2015, 6, 2148–2153, doi:10.3762/bjnano.6.220

• commercial, combined qPlus tuning fork [4] non-contact atomic force/scanning tunnelling microscope (NC-AFM/STM) operated at 5 K under ultra-high vacuum conditions. Each extraction attempt started with positioning the tip over one of the four carboxylic oxygen atoms (marked by red circles in Figure 1) of the

A simple method for the determination of qPlus sensor spring constants

• John Melcher,
• Julian Stirling and
• Gordon A. Shaw

Beilstein J. Nanotechnol. 2015, 6, 1733–1742, doi:10.3762/bjnano.6.177

• John Melcher Julian Stirling Gordon A. Shaw National Institute of Standards and Technology, Gaithersburg, MD 20899, USA 10.3762/bjnano.6.177 Abstract qPlus sensors are widely used to measure forces at the atomic scale, however, confidence in these measurements is limited by inconsistent reports

• of the spring constant of the sensor and complications from finite tip heights. Here we combine a numerical investigation of the force reconstruction with an experimental characterization of the flexural mechanics of the qPlus sensor. Numerical studies reveal significant errors in reconstructed force

• ; calibration; non-contact atomic force microscopy; qPlus; Introduction Non-contact-atomic force microscopy (ncAFM) has paved new inroads to the measurement of nanometer-scale properties that were previously inaccessible. By allowing the atomic-scale imaging of surfaces from insulators to conductors, the

Nano-contact microscopy of supracrystals

• Adam Sweetman,
• Nicolas Goubet,
• Ioannis Lekkas,
• Marie Paule Pileni and
• Philip Moriarty

Beilstein J. Nanotechnol. 2015, 6, 1229–1236, doi:10.3762/bjnano.6.126

• based on a combination of STM and dynamic force microscopy (DFM) imaging and spectroscopy. DFM experiments, also known as non-contact AFM (NC-AFM), are carried out using a quartz tuning fork sensor in the qPlus geometry [16][17] to which a tip has been glued. Shifts in the resonant frequency of a tine

• of the tuning fork due to variations in the tip–sample interaction are tracked and, via the formula introduced by Sader and Jarvis [18], can be converted to force or potential energy measurements. The qPlus sensor facilitates, in principle, a straight-forward method of acquiring tunnelling current

• probe displacement has been studied in considerable detail [23][24][25][26][27]. A recent review [28] outlines key developments in point-contact measurements, including the quantum point-contact microscopy strategy introduced by Zhang et al. [29]. State-of-the-art qPlus DFM, where both intra- [30][31

Patterning a hydrogen-bonded molecular monolayer with a hand-controlled scanning probe microscope

• Matthew F. B. Green,
• Taner Esat,
• Christian Wagner,
• Philipp Leinen,
• Alexander Grötsch,
• F. Stefan Tautz and
• Ruslan Temirov

Beilstein J. Nanotechnol. 2014, 5, 1926–1932, doi:10.3762/bjnano.5.203

• used a qPlus sensor [17] manufactured by CREATEC. The AFM/STM tip was made from a 0.3 mm long and 15 μm thick PtIr wire glued to the tuning fork of the qPlus sensor, and sharpened with a gallium focused ion beam (FIB). The resulting resonance frequency of the qPlus sensor was f0 = 30,300 Hz with a

• quality factor of Q ≈ 70,000. Contacting and manipulation were performed with the qPlus sensor oscillating with an amplitude of A0 ≈ 0.2–0.3 Å. Interactions in the junction were monitored by measuring the frequency shift Δf(z) ≈ −(f0/2k0)dFz/dz, where k0 = 1800 N/m is the stiffness of the quartz tuning

Calibration of quartz tuning fork spring constants for non-contact atomic force microscopy: direct mechanical measurements and simulations

• Jens Falter,
• Marvin Stiefermann,
• Gernot Langewisch,
• Philipp Schurig,
• Hendrik Hölscher,
• Harald Fuchs and
• André Schirmeisen

Beilstein J. Nanotechnol. 2014, 5, 507–516, doi:10.3762/bjnano.5.59

• -Leopoldshafen, Germany 10.3762/bjnano.5.59 Abstract Quartz tuning forks are being increasingly employed as sensors in non-contact atomic force microscopy especially in the “qPlus” design. In this study a new and easily applicable setup has been used to determine the static spring constant at several positions

• scale usually demand well defined environments, such as ultrahigh vacuum (UHV) and low temperatures (LT). For these conditions, force sensors based on quartz tuning forks in the “qPlus” design [5] have been proven to routinely provide stable operation and sufficient sensitivity to achieve the highest

• relative forces with high accuracy, for which the absolute stiffness of the sensor was not critical. Latest measurements of the absolute interaction forces impress by their force resolution [3][4][9] but suffer from the large error and spread in the determination of the geometric factors of the “qPlus

Impact of thermal frequency drift on highest precision force microscopy using quartz-based force sensors at low temperatures

• Florian Pielmeier,
• Daniel Meuer,
• Daniel Schmid,
• Christoph Strunk and
• Franz J. Giessibl

Beilstein J. Nanotechnol. 2014, 5, 407–412, doi:10.3762/bjnano.5.48

• eigenfrequency of the force sensor is of key importance for highest precision force measurements. Here, we study the influence of temperature changes on the resonance frequency of force sensors made of quartz, in a temperature range from 4.8–48 K. The sensors are based on the qPlus and length extensional

• principle. The frequency variation with temperature T for all sensors is negative up to 30 K and on the order of 1 ppm/K, up to 13 K, where a distinct kink appears, it is linear. Furthermore, we characterize a new type of miniaturized qPlus sensor and confirm the theoretically predicted reduction in

• detector noise. Keywords: AFM; frequency drift; length extensional resonator; needle sensor; qPlus sensor; quartz; Findings Frequency modulation atomic force microscopy [1] has become an essential tool for surface scientist‘s to study chemical and magnetic interactions at the atomic scale [2][3][4][5][6

Uncertainties in forces extracted from non-contact atomic force microscopy measurements by fitting of long-range background forces

• Adam Sweetman and
• Andrew Stannard

Beilstein J. Nanotechnol. 2014, 5, 386–393, doi:10.3762/bjnano.5.45

• transferred into the scan head and left to cool before imaging. Commercial qPlus sensors from Omicron with electrochemically etched tungsten wire glued to one tine of the tuning fork were introduced into the scan head without any further preparation. We typically recorded resonant frequencies of f0 ≈ 25 kHz

• indentation of the tip into the surface will require the tip structure checks to be repeated. This is likely to be even more important in the case of experiments using qPlus-type setups, where STM tip treatment methods are often used to prepare tips in situ on the surface. In these cases, significant transfer

The role of surface corrugation and tip oscillation in single-molecule manipulation with a non-contact atomic force microscope

• Christian Wagner,
• Norman Fournier,
• F. Stefan Tautz and
• Ruslan Temirov

Beilstein J. Nanotechnol. 2014, 5, 202–209, doi:10.3762/bjnano.5.22

• -molecule manipulation has particularly promising potential to yield new insights. We recently reported experiments, in which 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) molecules were lifted with a qPlus-sensor and analyzed these experiments by using force-field simulations. Irrespective of the

• experimental data points is related to the sliding of the molecule across the surface. Keywords: atomic force microscopy (AFM); force-field model; 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA); qPlus; single-molecule manipulation; Introduction The problem of the adsorption of organic molecules

• , and qPlus-based non-contact atomic force (NC-AFM) microscopes can be a potent tool when applied to studies of single-molecule manipulation [6][11][15]. The STM function facilitates the effective preparation of the experiment while the NC-AFM, operated simultaneously with the STM, is used to control

Influence of the adsorption geometry of PTCDA on Ag(111) on the tip–molecule forces in non-contact atomic force microscopy

• Gernot Langewisch,
• Jens Falter,
• André Schirmeisen and
• Harald Fuchs

Beilstein J. Nanotechnol. 2014, 5, 98–104, doi:10.3762/bjnano.5.9

• atomic force microscope (Omicron LT-SPM) that was operated in frequency-modulation mode [11] under ultrahigh vacuum conditions and at a temperature of ≈5 K using a tuning fork sensor (resonance frequency f0 = 24640 Hz, spring constant k ≈ 2000 N/m) in the qPlus design [12]. The amplitude of the sensor