Optimal geometry for a quartz multipurpose SPM sensor

• Julian Stirling

Beilstein J. Nanotechnol. 2013, 4, 370–376, doi:10.3762/bjnano.4.43

• through an angle θ is given by where J and G are the torsion constant and shear modulus of the beam. In the case of a cantilever beam with a tip of length Ltip (measured from the central axis of the beam), the lateral displacement of the tip apex, Alat, is Ltipθ. Replacing the torque with the lateral tip

• component to the motion of the tip apex in the first eigenmode [2]. This lateral component is perpendicular to the torsional eigenmode, thus making it impossible to truly separate the normal and lateral forces. This problem is exacerbated if the tip length is further increased to increase sensitivity to

• tip length. However, due to the symmetry of the sensor this will not cause unwanted lateral motion at the tip apex in the first eigenmode. Eigenfrequencies When considering the eigenfrequencies of the sensor, the inertia of the tip plays a very strong role, which cannot be ignored. Solving Equation 5

Photoresponse from single upright-standing ZnO nanorods explored by photoconductive AFM

• Igor Beinik,
• Markus Kratzer,
• Astrid Wachauer,
• Lin Wang,
• Yuri P. Piryatinski,
• Gerhard Brauer,
• Xin Yi Chen,
• Yuk Fan Hsu,
• Aleksandra B. Djurišić and
• Christian Teichert

Beilstein J. Nanotechnol. 2013, 4, 208–217, doi:10.3762/bjnano.4.21

• ™ with a cantilever resonance frequency of approximately 330 kHz, a tip-curvature radius smaller than 10 nm, and a half-cone angle at the tip apex of about 10°. The applied forces have to be tuned carefully to avoid breaking the ZnO NRs [30][43]. For all experiments we used fresh probes as received from

Bimodal atomic force microscopy driving the higher eigenmode in frequency-modulation mode: Implementation, advantages, disadvantages and comparison to the open-loop case

• Daniel Ebeling and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2013, 4, 198–207, doi:10.3762/bjnano.4.20

• was not the case. We believe that this asymmetry is likely to be related to the shape of the tip apex. Amplitude control capability and its implications An important advantage of the AM-FM scheme with respect to the AM-OL method is that the spectroscopy eigenmode operates at a fixed phase of 90

Calculation of the effect of tip geometry on noncontact atomic force microscopy using a qPlus sensor

• Julian Stirling and
• Gordon A. Shaw

Beilstein J. Nanotechnol. 2013, 4, 10–19, doi:10.3762/bjnano.4.2

• qPlus atomic force microscopy the tip length can in principle approach the length of the cantilever. We present a detailed mathematical model of the effects this has on the dynamic properties of the qPlus sensor. The resulting, experimentally confirmed motion of the tip apex is shown to have a large

• structure of the tip apex [2], many experiments have demonstrated the ability of qPlus atomic force microscopy (AFM) to produce unprecedented imaging resolution. Other qPlus studies have measured both the forces necessary to perform atomically precise manipulation [3][4][5], and the strength of both atomic

• and molecular interactions [6][7]. As with all forms of AFM, image resolution and force measurements ultimately depend on the structure of the last few angstroms of the tip apex [1][2][4][6][7][8][9]. The qPlus sensor is unusual for an AFM sensor in that it is constructed from a quartz tuning fork and

Probing three-dimensional surface force fields with atomic resolution: Measurement strategies, limitations, and artifact reduction

• Mehmet Z. Baykara,
• Omur E. Dagdeviren,
• Todd C. Schwendemann,
• Harry Mönig,
• Eric I. Altman and
• Udo D. Schwarz

Beilstein J. Nanotechnol. 2012, 3, 637–650, doi:10.3762/bjnano.3.73

• function of the three spatial dimensions, with picometer and piconewton accuracy. Since the results of such measurements may be affected by piezo nonlinearities, thermal and electronic drift, tip asymmetries, and elastic deformation of the tip apex, these effects need to be considered during image

• , empowering experimentalists to characterize the tip–sample interaction in terms of normal forces Fn, potential energies E, and the distance z between the tip apex and the sample surface [4][5][6][7]. More recently, thanks to improvements in the design of atomic force microscopes [8][9] as well as the

• development of new data-acquisition strategies [10][11], DFS measurements have been extended to two and three spatial dimensions. As a result, tip–sample interaction forces and energies can be measured as a function of both the tip–sample distance z and the lateral position (x, y) of the tip apex above the

Models of the interaction of metal tips with insulating surfaces

• Thomas Trevethan,
• Matthew Watkins and
• Alexander L. Shluger

Beilstein J. Nanotechnol. 2012, 3, 329–335, doi:10.3762/bjnano.3.37

• regions of the tip–surface interaction with high stability, in particular the “near contact” region of separation where the tip apex atom and surface are separated by only a few angstroms (i.e., the typical range of chemical bonds). However, the nature of the force between the tip and the surface is

• highly dependent on the exact atomic structure and chemical nature of the tip apex. In the case of ionic surfaces, different terminating atoms can lead to completely inverted image contrasts [3][4], in which case it is not even possible to identify the polarity of surface ions corresponding to

• protrusions in the image. The control and characterization of the tip-apex termination is therefore critical for the reliable interpretation of images. AFM tip–cantilever assemblies are usually fabricated from silicon, which is then exposed to air and will thus develop a native oxide layer with air-induced

Combining nanoscale manipulation with macroscale relocation of single quantum dots

• Francesca Paola Quacquarelli,
• Richard A. J. Woolley,
• Martin Humphry,
• Jasbiner Chauhan,
• Philip J. Moriarty and
• Ashley Cadby

Beilstein J. Nanotechnol. 2012, 3, 324–328, doi:10.3762/bjnano.3.36

• , we can ascertain the minimum amount of surface–tip contact force required for the manipulation to take place; reducing tip wear and image degradation. Tip state also plays an important role in the manipulation process, and the automatic characterisation and optimization of the AFM tip apex would be

Graphite, graphene on SiC, and graphene nanoribbons: Calculated images with a numerical FM-AFM

• Fabien Castanié,
• Laurent Nony,
• Sébastien Gauthier and
• Xavier Bouju

Beilstein J. Nanotechnol. 2012, 3, 301–311, doi:10.3762/bjnano.3.34

• functionalized tip, that is, with a CO molecule attached to the tip apex acting as a supertip [60]. Most of the mentioned studies were based on a technical improvement consisting of the use of a tuning fork of the qPlus sensor type [61]. This sensor is an AFM tip that is fixed to one branch of a quartz tuning

• future. It should be mentioned also that when the tip interacts chemically with the substrate through bond creation between the tip apex atom and surface atoms, the choice of the force-field method may be difficult to justify. In that case, although reactive force fields exist [89][90][91] and may be

• composed of a nanosphere to mimic the probe body supporting a cluster of atoms for the tip apex. The sphere has a radius R of 4 nm and its force of interaction with a surface is well described by if (r − R) « R [98]. Hk is the Hamaker constant (1 eV) and r the sphere–surface distance. The cluster has a

Simultaneous current, force and dissipation measurements on the Si(111) 7×7 surface with an optimized qPlus AFM/STM technique

• Zsolt Majzik,
• Martin Setvín,
• Andreas Bettac,
• Albrecht Feltz,
• Vladimír Cháb and
• Pavel Jelínek

Beilstein J. Nanotechnol. 2012, 3, 249–259, doi:10.3762/bjnano.3.28

• chemical interaction [43] between the tip apex and the adatoms becomes larger. In addition, we performed site-specific point spectroscopy [44][45] above Si adatoms. Note that the spectroscopy curves shown in Figure 8A were obtained with a slightly different tip than the maps in Figure 7. To obtain the bare

• measurement with the same sensor but with a different tip apex. The tip change was induced by applying a combination of z pulses and voltage pulses. The obtained data show (Figure 8B) a significant reduction of the force maximum of the short-range force FSR ≈ 0.8 nN. In the weak-interaction regime (here z

Modeling noncontact atomic force microscopy resolution on corrugated surfaces

• Kristen M. Burson,
• Mahito Yamamoto and
• William G. Cullen

Beilstein J. Nanotechnol. 2012, 3, 230–237, doi:10.3762/bjnano.3.26

• of a supersharp tip (Figure 1c). Atomic resolution on Si(111) depends on the short-range chemical forces and the bonding configuration of the tip apex atom [20][21][22][23], whereas long-range vdW interactions are a constant background force for AFM imaging of this and other flat surfaces. In

• interaction is repulsive. This is rather unsatisfactory at present, as it would be preferable to have well-defined numerical values (even if unrealistically large), and then let the limits of the model be decided on physical grounds, i.e., peak force or stress on the tip apex, etc. 3 Calculation of frequency

• interaction of the tip and the corrugated sample surface. For flat surfaces, the vdW interaction provides a constant background and is most strongly concentrated at the tip apex, but for corrugated surfaces the vdW interactions over peak positions and valley positions are different and interactions with the

A measurement of the hysteresis loop in force-spectroscopy curves using a tuning-fork atomic force microscope

• Manfred Lange,
• Dennis van Vörden and
• Rolf Möller

Beilstein J. Nanotechnol. 2012, 3, 207–212, doi:10.3762/bjnano.3.23

• gradient between the oscillating tip and a surface (force-spectroscopy measurements). When nonconservative forces act between the tip apex and the surface the oscillation amplitude is damped. The dissipation is caused by bistabilities in the potential energy surface of the tip–sample system, and the

• constant by a second control loop. The amplitude control loop provides valuable information on nonconservative interactions between the tip apex and the sample, which cause damping of the oscillation amplitude [3]. The excitation energy needed to keep the oscillation amplitude constant is directly related

• caused by bistabilities in the potential energy surface of the tip–sample system. Experiments and calculations [7][8] show that dissipation on the atomic level originates from the adhesion or displacement of single atoms caused by strong interaction between the sample and the tip apex. Simulations for an

Noncontact atomic force microscopy study of the spinel MgAl₂O₄(111) surface

• Morten K. Rasmussen,
• Kristoffer Meinander,
• Flemming Besenbacher and
• Jeppe V. Lauritsen

Beilstein J. Nanotechnol. 2012, 3, 192–197, doi:10.3762/bjnano.3.21

• differences [23] or the structure and composition of the tip [2]. Furthermore, the size of the NC-AFM tip apex may hinder the accurate measurement of the true lowest point in the narrow geometrical depression between the triangles, and from this perspective it is reasonable to consider the dark region to

Molecular-resolution imaging of pentacene on KCl(001)

• Julia L. Neff,
• Jan Götzen,
• Enhui Li,
• Michael Marz and
• Regina Hoffmann-Vogel

Beilstein J. Nanotechnol. 2012, 3, 186–191, doi:10.3762/bjnano.3.20

• in the center of the unit cell is often weaker. This could also be the case here such that no dark feature is observed in the center of the unit cell. In particular if one or several molecules are located on the tip apex and contribute to the imaging forces, the contrast could strongly depend on the

Effect of the tip state during qPlus noncontact atomic force microscopy of Si(100) at 5 K: Probing the probe

• Adam Sweetman,
• Sam Jarvis,
• Rosanna Danza and
• Philip Moriarty

Beilstein J. Nanotechnol. 2012, 3, 25–32, doi:10.3762/bjnano.3.3

• surfaces, and has demonstrated the capability for atomic manipulation solely using chemical forces. Nonetheless, the role of the tip apex in both imaging and manipulation remains poorly understood and is an active area of research both experimentally and theoretically. Recent work employing specially

• functionalised tips has provided additional impetus to elucidating the role of the tip apex in the observed contrast. Results: We present an analysis of the influence of the tip apex during imaging of the Si(100) substrate in ultra-high vacuum (UHV) at 5 K using a qPlus sensor for noncontact atomic force

• ; noncontact AFM; qPlus; Si(001); Si(100); tip (apex) structure; Introduction It is now generally accepted that atomic resolution in NC-AFM imaging on semiconducting surfaces is due to the chemical force between the atoms of the surface and the last few atoms of the tip apex [1][2][3][4]. Even with well

Distance dependence of near-field fluorescence enhancement and quenching of single quantum dots

• Volker Walhorn,
• Jan Paskarbeit,
• Heinrich Gotthard Frey,
• Alexander Harder and
• Dario Anselmetti

Beilstein J. Nanotechnol. 2011, 2, 645–652, doi:10.3762/bjnano.2.68

• the dependence of the fluorescence emission from a single quantum dot on the distance from the gold coated cantilever tip apex, we acquired the fluorescence emission intensity at several z-distances. After each 2.5 nm step, 200 frames with an exposure time of 50 ms were obtained. The measurements

• dipolar coupling between the incident light and the gold tip leads to a field enhancement confined at the tip apex. Secondly, we have to consider the dipolar coupling between the fluorophore and the tip, which either leads to fluorescence enhancement due to resonant coupling or fluorescence quenching as a

• ranging from 18–46° were modelled. We evaluated the observable intensity of the fluorescence emission I as a function of tip distance, in a three step procedure. Firstly, we examined the interaction between the cantilever tip apex and the incident light. The relative excitation rate Γexc (Equation 2) of a

The role of the cantilever in Kelvin probe force microscopy measurements

• George Elias,
• Thilo Glatzel,
• Ernst Meyer,
• Alex Schwarzman,
• Amir Boag and
• Yossi Rosenwaks

Beilstein J. Nanotechnol. 2011, 2, 252–260, doi:10.3762/bjnano.2.29

• spherical tip apex and the bottom part of the cone contribute 25% and 30% to the overall homogeneous force, respectively. The rest of the force stems mostly from the cantilever, especially from the two segments which are nearest to the tip which contribute 25.8% and 6.5% each. The effect of the cantilever

• the cone contribute 82.7% and 17.2%, respectively, of the inhomogeneous force, while the contribution of the rest of the probe was negligible. This demonstrates the profound effect of the tip apex on the KPFM resolution and, consequently, the minor influence of the cantilever. Further calculations

• showed that at smaller probe sample distances the homogenous force contribution of the tip apex is higher. At a probe–sample distance of 1.2 nm (a typical distance in ultra-high vacuum measurements) the tip apex contributes 83% to the homogenous force, the cone lower segment contributes 7.3%, and the

Single-pass Kelvin force microscopy and dC/dZ measurements in the intermittent contact: applications to polymer materials

• Sergei Magonov and
• John Alexander

Beilstein J. Nanotechnol. 2011, 2, 15–27, doi:10.3762/bjnano.2.2

• nanotubes probes (generously provided by Carbon Design Innovations). The probes with small tip apex and tips with high aspect ratio provide higher spatial resolution of surface potential images whereas the probes with thicker tips have a better signal-to-noise ratio of the surface potential. The majority of

• exhibit a different dC/dZ patterns with a central part darker that the perimeter. This suggests that at elevated locations only the tip apex is sensing the electrostatic force and a large part of the tip participates in the force interactions when the domains are lower. The second is related to the

Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

• Thomas König,
• Georg H. Simon,
• Lars Heinke,
• Leonid Lichtenstein and
• Markus Heyde

Beilstein J. Nanotechnol. 2011, 2, 1–14, doi:10.3762/bjnano.2.1

• surface [26]. Assuming that the forces acting on such metal adatoms are comparable to those on the tip apex, one may conclude that a more attractive interaction occurs between the oxygen sites and the tip. This results in a contrast where oxygen atoms are imaged as protrusions in a constant Δf NC-AFM

Tip-sample interactions on graphite studied using the wavelet transform

• Giovanna Malegori and
• Gabriele Ferrini

Beilstein J. Nanotechnol. 2010, 1, 172–181, doi:10.3762/bjnano.1.21

• decrease of the Q value just before the jumps-to-contact. The dissipation mechanism related to this sharp transition is due to a local interaction of the tip apex with the surface. In these experiments, the acquisition and storage of the photodiode time signal requires tens of seconds at each tip-sample