Current-induced runaway vibrations in dehydrogenated graphene nanoribbons

• Rasmus Bjerregaard Christensen,
• Jing-Tao Lü,
• Per Hedegård and
• Mads Brandbyge

Beilstein J. Nanotechnol. 2016, 7, 68–74, doi:10.3762/bjnano.7.8

• circular “water-wheel” motion, either in real space [10] or in mode space. Another requirement is that these modes have little damping due to the coupling to the phonon reservoir. Unfortunately, there has not been a clear experimental setup where these new theoretical findings can be put to a test proving

• negative the mode is damped. The damping can be quantified by the inverse Q-factor giving the change in energy per period Thus, the run-away modes can be identified as the modes where Im(ω) > 0. The run-away modes are a linear combination of the non-perturbed normal modes. Normally, the runaway makes

• closed loops in real or in abstract mode space. Thus, the NC force allows the mode to pick up energy every time a loop is completed, eventually leading to break down of the harmonic approximation, ending with, e.g., rupture or damping by anharmonic effects leading to a limit cycle motion [24]. Numerical

Large area scanning probe microscope in ultra-high vacuum demonstrated for electrostatic force measurements on high-voltage devices

• Urs Gysin,
• Thilo Glatzel,
• Thomas Schmölzer,
• Adolf Schöner,
• Sergey Reshanov,
• Holger Bartolf and
• Ernst Meyer

Beilstein J. Nanotechnol. 2015, 6, 2485–2497, doi:10.3762/bjnano.6.258

• damping of the sensor. Furthermore, UHV environment allows for the analysis of clean surfaces under controlled environmental conditions. Because of these requirements we built a large area scanning probe microscope operating under UHV conditions at room temperature allowing to perform various electrical

• under UHV condition has the advantage of a high quality factor (Q ≈ 30,000) due to the suppression of viscous damping and therefore increases the force sensitivity by orders of magnitude [27][28]. To analyse complex and large micro-structures a large positioning and scanning unit is necessary, under

• range of 20 mm in vertical direction, used for coarsely approaching the sample to the cantilever tip. All piezo elements are driven with a custom designed controller generating saw tooth voltages with amplitudes ranging from 0 to 400 V and frequencies up to 1 kHz. Damping system Figure 4 shows the CAD

Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains

• Carlos Sabater,
• Carlos Untiedt and
• Jan M. van Ruitenbeek

Beilstein J. Nanotechnol. 2015, 6, 2338–2344, doi:10.3762/bjnano.6.241

• ). They observe that a pair of nearly-degenerate vibration modes becomes coupled by the action of the current-induced forces, leading to negative damping of the atomic motion. In other words, the amplitude of the motion keeps increasing as a result of the energy that is pumped into the motion by the non

Kelvin probe force microscopy for local characterisation of active nanoelectronic devices

• Tino Wagner,
• Hannes Beyer,
• Patrick Reissner,
• Philipp Mensch,
• Heike Riel,
• Bernd Gotsmann and
• Andreas Stemmer

Beilstein J. Nanotechnol. 2015, 6, 2193–2206, doi:10.3762/bjnano.6.225

• topography of the sample. To maintain best feedback settings at every location during a scan, we introduce a novel controller for FM-KFM based on stochastic optimal control [37]. Optimal control and model-based controllers have been successfully used before in AFM, e.g., for active damping of cantilevers [38

An adapted Coffey model for studying susceptibility losses in interacting magnetic nanoparticles

• Mihaela Osaci and
• Matteo Cacciola

Beilstein J. Nanotechnol. 2015, 6, 2173–2182, doi:10.3762/bjnano.6.223

• calculation and experimental results [21]. This calculation shows the dependence of the relaxation time on the magnetic damping constant α. For the case of most ferromagnetic and ferrimagnetic nanoparticle systems, the magnetic damping constant α exhibits low values (α << 1) [22]. In this section, we adapt

• the Coffey analytical model according to Equations 9–11. Under these conditions, the time relaxation relation, in case of an oblique magnetic field, is [12]: With being the free diffusion magnetization time at low damping constants (α << 1) [12]: In Equation 21γ is the gyromagnetic ratio. If ψi is

Thermoelectricity in molecular junctions with harmonic and anharmonic modes

• Bijay Kumar Agarwalla,
• Jian-Hua Jiang and
• Dvira Segal

Beilstein J. Nanotechnol. 2015, 6, 2129–2139, doi:10.3762/bjnano.6.218

• done rigorously at the level of the quantum master equations and within the NEGF technique [7][43] to yield the rates with and a damping term Γph(ω0). Interestingly, we confirmed (not shown) that this additional energy relaxation process does not modify the thermoelectric efficiency displayed in

Magnetic reversal dynamics of a quantum system on a picosecond timescale

• Nikolay V. Klenov,
• Alexey V. Kuznetsov,
• Igor I. Soloviev,
• Sergey V. Bakurskiy and
• Olga V. Tikhonova

Beilstein J. Nanotechnol. 2015, 6, 1946–1956, doi:10.3762/bjnano.6.199

• field; the presence of which allows for the definition of the so-called Larmor frequency, ΩL = γHZ. Classical damping can be set as α = 0 for the simplest case when the decoherence processes in the quantum model can be neglected. For H(t) = H0f(t)cos(ωlt), with ωl = ΩL, ΩLτ >> 1 one can arrive at: For

Large-voltage behavior of charge transport characteristics in nanosystems with weak electron–vibration coupling

• Tomáš Novotný and
• Wolfgang Belzig

Beilstein J. Nanotechnol. 2015, 6, 1853–1859, doi:10.3762/bjnano.6.188

• and the oscillator mode decoupled from any other degrees of freedom apart from the electronic level, i.e., with no external damping studied previously [18][19][20]. The above result (Equation 19) can be, however, applied under far wider conditions (multilevel dot, non-zero temperature and/or external

• damping of the oscillator mode) as we briefly discuss in the concluding section. In the case specified above, we can obtain the large-V asymptotics of the CGF by identifying the known leading contributions of the constituent parts. From the definitions and with the voltage-independent relaxation time

• expressions are well known in the literature [10][12][19][25] and can/have been applied to cases with multiple electronic levels, finite temperatures, and/or external damping (whose magnitude can be even assessed from ab-initio calculations [33]). In particular, all the relevant quantities for the multilevel

Improved atomic force microscopy cantilever performance by partial reflective coating

• Zeno Schumacher,
• Yoichi Miyahara,
• Laure Aeschimann and
• Peter Grütter

Beilstein J. Nanotechnol. 2015, 6, 1450–1456, doi:10.3762/bjnano.6.150

• damping of the cantilever, leading to a lower mechanical quality factor (Q-factor). In dynamic mode operation in high vacuum, a cantilever with a high Q-factor is desired in order to achieve a lower minimal detectable force. The reflective coating can also increase the low-frequency force noise. In

• desired to achieve a lower minimal detectable force gradient. By using a cantilever in an ultra high vacuum environment (UHV), the Q-factor is drastically increased due to the absence of damping by air atmosphere and is limited by the intrinsic properties of the cantilever. It is known that adding a metal

• available short cantilevers [5]. These changes in the cantilever performance can be described by the additional viscoelastic damping and increased susceptibility to temperature fluctuations due to the added metal layer causing a bimetallic effect. Paoline et al. presented a model that uses a complex spring

Nanomechanical humidity detection through porous alumina cantilevers

• Olga Boytsova,
• Alexey Klimenko,
• Vasiliy Lebedev,
• Alexey Lukashin and
• Andrey Eliseev

Beilstein J. Nanotechnol. 2015, 6, 1332–1337, doi:10.3762/bjnano.6.137

• vacuum, when the vapors are absent, the measurement of the resonance frequency is routinely made compared to measurements in viscous media. At first we emphasized the damping effect on cantilever vibration for porous AAO and standard Si cantilevers explored in the real system (air) and in model (vacuum

Attenuation, dispersion and nonlinearity effects in graphene-based waveguides

• Almir Wirth Lima Jr.,
• João Cesar Moura Mota and
• Antonio Sergio Bezerra Sombra

Beilstein J. Nanotechnol. 2015, 6, 1221–1228, doi:10.3762/bjnano.6.125

• supported in graphene when and , respectively. By numerical simulations it was proved that energy is absorbed or dissipated when . However, if we consider a fixed graphene chemical potential, the temperature increase causes a finite damping, which is smaller for TM vs TE modes. This is because the real

Stiffness of sphere–plate contacts at MHz frequencies: dependence on normal load, oscillation amplitude, and ambient medium

• Jana Vlachová,
• Rebekka König and
• Diethelm Johannsmann

Beilstein J. Nanotechnol. 2015, 6, 845–856, doi:10.3762/bjnano.6.87

• level on the other. The CM model ignores viscous dissipation. In consequence, the energy dissipated in reciprocating sliding scales as the cube of the oscillation amplitude in the low-amplitude limit. Following from this scaling law, the damping of a resonator, which experiences particle slip in one way

• or another, should go to zero at small amplitudes. An explanation of the contact resonance method, which probes these relations, is given below. Deviating from this scaling prediction, the contacts usually do damp a resonance even at the smallest accessible amplitudes. This type of damping must be

• shown in the four panels at the top and the four panels at the bottom were acquired in air and in water, respectively. In liquids, the maximum achievable amplitude is lower than in air because of damping. Δf and ΔΓ decrease and increase with amplitude, respectively, as is characteristic for partial slip

Stick–slip behaviour on Au(111) with adsorption of copper and sulfate

• Nikolay Podgaynyy,
• Sabine Wezisla,
• Christoph Molls,
• Shahid Iqbal and
• Helmut Baltruschat

Beilstein J. Nanotechnol. 2015, 6, 820–830, doi:10.3762/bjnano.6.85

• was observed by Meyer and coworkers [33]: Upon an increase in normal load on a NaCl(001) surface a transition to multiple slip was found. According to [34], who predicted such transitions from theory for low damping conditions and also observed it on HOPG, this process is based on energy minimisation

Mapping of elasticity and damping in an α + β titanium alloy through atomic force acoustic microscopy

• M. Kalyan Phani,
• Anish Kumar,
• T. Jayakumar,
• Walter Arnold and
• Konrad Samwer

Beilstein J. Nanotechnol. 2015, 6, 767–776, doi:10.3762/bjnano.6.79

• . Physikalisches Institut, Georg-August-Universität, Friedrich Hund Platz 1, D-37077 Göttingen, Germany 10.3762/bjnano.6.79 Abstract The distribution of elastic stiffness and damping of individual phases in an α + β titanium alloy (Ti-6Al-4V) measured by using atomic force acoustic microscopy (AFAM) is reported

• in the present study. The real and imaginary parts of the contact stiffness k* are obtained from the contact-resonance spectra and by using these two quantities, the maps of local elastic stiffness and the damping factor are derived. The evaluation of the data is based on the mass distribution of the

• cantilever with damped flexural modes. The cantilever dynamics model considering damping, which was proposed recently, has been used for mapping of indentation modulus and damping of different phases in a metallic structural material. The study indicated that in a Ti-6Al-4V alloy the metastable β phase has

Manipulation of magnetic vortex parameters in disk-on-disk nanostructures with various geometry

• Maxim E. Stebliy,
• Alexander G. Kolesnikov,
• Alexey V. Ognev,
• Alexander S. Samardak and
• Ludmila A. Chebotkevich

Beilstein J. Nanotechnol. 2015, 6, 697–703, doi:10.3762/bjnano.6.70

• by using OOMMF software [9] with standard parameters for Py: Ms = 860 Gs, exchange stiffness A = 1.38 · 106 erg/cm, damping factor α = 0.05 [11]. The magnetic anisotropy was chosen zero in order not to insert an asymmetry of magnetic properties into the system. Dimension of the simulated disk-on-disk

Influence of spurious resonances on the interaction force in dynamic AFM

• Luca Costa and
• Mario S. Rodrigues

Beilstein J. Nanotechnol. 2015, 6, 420–427, doi:10.3762/bjnano.6.42

• as calibration method [17][18][19] compared to the standard characterization of the cantilever transfer function. Results and Discussion Interaction stiffness and damping In this section we review two general formulas for the interaction stiffness ki and damping γi without using the assumption that

• motion of the mass: , which from Newton’s second law implies Ar = −mAω2. Hence, from basic trigonometric relationships: Consider that the force Fy(t) has two contributions, a restoring force Frest and a damping force Fdamp, so that Fy(t) = Frest(t) + Fdamp(t). The restoring force is directly proportional

• to the position of the moving mass, whereas the damping is directly proportional to its velocity. Let us define k as being the proportionality constant between the force and the position and γ the proportionality constant between the damping force and the speed of the mass. Hence, Comparing Equation

Dynamic force microscopy simulator (dForce): A tool for planning and understanding tapping and bimodal AFM experiments

• Horacio V. Guzman,
• Pablo D. Garcia and
• Ricardo Garcia

Beilstein J. Nanotechnol. 2015, 6, 369–379, doi:10.3762/bjnano.6.36

• , where E is the Young modulus of the cantilever, I the area moment of inertia, α1 the internal damping coefficient of the cantilever, ρ the cantilever mass density, b, h and L are the width, thickness and length of the cantilever, respectively, α0 is the hydrodynamic damping of the medium, and w(x,t) is

Mechanical properties of MDCK II cells exposed to gold nanorods

• Anna Pietuch,
• Bastian Rouven Brückner,
• David Schneider,
• Marco Tarantola,
• Christina Rosman,
• Carsten Sönnichsen and
• Andreas Janshoff

Beilstein J. Nanotechnol. 2015, 6, 223–231, doi:10.3762/bjnano.6.21

• concentration-dependent QCM measurements and found that damping (dissipation) increases steadily from 2.5 to 25 μg/mL until eventually leveling off (Figure 6). Generally, dark-field micrographs showed that particles are homogeneously distributed within the cell interior with a trend to accumulate around the

Tunable light filtering by a Bragg mirror/heavily doped semiconducting nanocrystal composite

• Ilka Kriegel and
• Francesco Scotognella

Beilstein J. Nanotechnol. 2015, 6, 193–200, doi:10.3762/bjnano.6.18

• optical properties in heavily doped semiconductor NCs in the NIR, with a complex dielectric function given by [27][28][29][30][31]: where where Γ is the free carrier damping and is the plasma frequency of the free carriers of the system. Here, NC is the carrier density, e the charge of the electron, m

• considered a dispersion of Cu2−xSe NCs in toluene with a spherical shape and a diameter of 15 nm, with ε∞ = 11 [27][43]. The carrier density-dependent effective mass and damping constant were taken from [43] with the following parameters: m1* = 0.445·m0, m2* = 0.394·m0, m3* = 0.334·m0, and m4* = 0.336·m0 and

• of effective mass and damping constant. A blue shift of up to 0.7 eV and an increase in intensity with increasing carrier density is observed. The calculated results are in good agreement with experimental results obtained in [27][28][29][30][31][32]. In those works, a modulation of the plasmonic

Accurate, explicit formulae for higher harmonic force spectroscopy by frequency modulation-AFM

• Kfir Kuchuk and
• Uri Sivan

Beilstein J. Nanotechnol. 2015, 6, 149–156, doi:10.3762/bjnano.6.14

• –surface interaction Here, k is the effective cantilever spring constant, ω0 is the fundamental resonance frequency in the absence of tip–surface interaction, q(t) is the tip position, γ is the damping coefficient, and F0 and ω are the amplitude and frequency of the driving force, respectively. As the

• . The derivation of Feven relies on its sole dependence upon tip–sample separation in Equation 6. This is not the case for Fodd, which is out of phase with q(t). This issue is resolved by noting that many dissipative forces have the form [13] with Γ, the generalised damping coefficient, depending only

• therefore have the same solutions. We may then refer to Table 1 for these solutions. For example, using Equation 15, the formula for the generalized damping coefficient for n = 2 is readily derived as (Equation 20): Expressions in terms of higher harmonics may be similarly derived. We have shown that by

High-frequency multimodal atomic force microscopy

• Adrian P. Nievergelt,
• Jonathan D. Adams,
• Pascal D. Odermatt and
• Georg E. Fantner

Beilstein J. Nanotechnol. 2014, 5, 2459–2467, doi:10.3762/bjnano.5.255

• squeeze-film damping of the cantilever, the latter of which is roughly constant while in feedback. We used a thin-film blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA) as a sample (PS–PMMA–15M, Bruker AFM probes); its separation into soft and hard domains makes it a widely used standard for

• due to viscous damping, however the detection bandwidth scales linearly with the dissipated power. The linear scaling is due to the fact that both the dissipated power (see Equation 1) and the cantilever AC-bandwidth, which is proportional to (f0/Q), scale proportionally with the resonance frequency

Inorganic Janus particles for biomedical applications

• Isabel Schick,
• Steffen Lorenz,
• Dominik Gehrig,
• Stefan Tenzer,
• Wiebke Storck,
• Karl Fischer,
• Dennis Strand,
• Frédéric Laquai and
• Wolfgang Tremel

Beilstein J. Nanotechnol. 2014, 5, 2346–2362, doi:10.3762/bjnano.5.244

• . attributed this broadening and damping to the tunnelling of conduction band electrons of the Au nanoparticles into the projected density of states of the Fe3O4 domains, the so-called “interface decay channel” [56]. As a metal oxide starts to nucleate heterogeneously on the gold nanoparticles, the induced

Localized surface plasmon resonances in nanostructures to enhance nonlinear vibrational spectroscopies: towards an astonishing molecular sensitivity

• Dan Lis and
• Francesca Cecchet

Beilstein J. Nanotechnol. 2014, 5, 2275–2292, doi:10.3762/bjnano.5.237

• described as: where Aijk(l) (NR) and are the non-resonant amplitudes and phase; Aijk(l) (q), Γq and ωq are the oscillator strength, the damping factor and the vibrational frequency of the q-th vibrational mode; ωIR, ωp and ωS are the infrared, the pump and the Stokes beam frequencies. The oscillator

Modeling viscoelasticity through spring–dashpot models in intermittent-contact atomic force microscopy

• Enrique A. López-Guerra and
• Santiago D. Solares

Beilstein J. Nanotechnol. 2014, 5, 2149–2163, doi:10.3762/bjnano.5.224

• displacement while the former experience dissipation through subsequent surface relaxation of stress initially stored in springs. In the case of the Nafion model we have varied the magnitude of c1 and c2 (see Figure 3a) to observe the effect of changing the relative importance of the damping elements. Figure 7

• shows the results for the case when both dashpots have the same damping constant. Figure 7a illustrates how dissipation decreases when the frequency increases for the range studied here (10–200 kHz). It is interesting to see in Figure 7b that regardless of the amplitude setpoint (A1/A01) the level of

• increases within a range of 0.4 to 0.5 of the ratio A1/A01. In contrast, for Figure 8, when the dashpot c2 is set to a high damping value compared to c1 (notice that the dashpot c2 in Figure 3a hardly yields when compared to c1) the behavior of dissipation changes drastically compared to the results of

Properties of plasmonic arrays produced by pulsed-laser nanostructuring of thin Au films

• Katarzyna Grochowska,
• Katarzyna Siuzdak,
• Peter A. Atanasov,
• Carla Bittencourt,
• Anna Dikovska,
• Nikolay N. Nedyalkov and
• Gerard Śliwiński

Beilstein J. Nanotechnol. 2014, 5, 2102–2112, doi:10.3762/bjnano.5.219

• indicate damping confirmed by short dephasing times not exceeding 4 fs, the self-organized Au NP structures reveal quite a strong enhancement of the optical signal. This was consistent with the near-field modeling and micro-Raman measurements as well as a test of the electrochemical sensing capability

• microscope and inspection spectroscopic measurements. The effect of the nanostructure morphology on plasmonic properties (such as resonance position and damping), the near- and mid-field enhancement of the optical signal, and evidence of sensing capability are discussed. Moreover, the possibility of tuning

• enhanced Raman spectroscopy)). In the estimation of the plasmon damping effect, the relation between the observable Г and dephasing time T2 = 2/Γ can be applied, where Г is the FWHM of the plasmon resonance. For simplified analysis, it is assumed that the line broadening effects are independent and