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

• 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

• ). Working under modulated illumination also allows direct SPV measurements using special modulation/demodulation schemes, such as the one recently proposed by Miyazaki and co-workers for ac-bias KPFM [6]. In addition, most time-resolved KPFM modes developed so far rely on the use of a pulsed/modulated

• cantilever eigenmode. This transfer or rejection (i.e., a measurement of a Fourier harmonic at the pump frequency through a demodulation at the second eigenmode frequency) is achieved by using two numerical lock-in amplifiers in cascade, which allows the generation of proper phase-coherent combination of

Mapping of integrated PIN diodes with a 3D architecture by scanning microwave impedance microscopy and dynamic spectroscopy

• Rosine Coq Germanicus,
• Peter De Wolf,
• Florent Lallemand,
• Catherine Bunel,
• Serge Bardy,
• Hugues Murray and
• Ulrike Lüders

Beilstein J. Nanotechnol. 2020, 11, 1764–1775, doi:10.3762/bjnano.11.159

• amplification and demodulation of the reflected signal (Figure 1), the complex admittance of the tip–sample impedance is given by the real part of sMIM (sMIM-R) and by the imaginary part of sMIM (sMIM-C) [27][28]. With a second quadrature mixer (Figure 1), the ∂C/∂V amplitude and ∂C/∂V phase are also measured

Measurement of electrostatic tip–sample interactions by time-domain Kelvin probe force microscopy

• Christian Ritz,
• Tino Wagner and
• Andreas Stemmer

Beilstein J. Nanotechnol. 2020, 11, 911–921, doi:10.3762/bjnano.11.76

• technique. The sample examined consists of two overlapping single-layer graphene sheets, forming a bilayer in the lower part of the image. For comparing the TD controller to state-of-the-art KFM, the graphene flake was initially scanned by standard FM-KFM using sideband demodulation. A Kalman filter was

A review of demodulation techniques for multifrequency atomic force microscopy

• David M. Harcombe,
• Michael G. Ruppert and
• Andrew J. Fleming

Beilstein J. Nanotechnol. 2020, 11, 76–91, doi:10.3762/bjnano.11.8

• the sensitivity to other frequency components and the magnitude of demodulation artifacts for a range of demodulator bandwidths. Performance differences are demonstrated through higher harmonic atomic force microscopy imaging. Keywords: atomic force microscopy (AFM); multifrequency; demodulation

• , which establishes the requirement for demodulation in AFM. In intermittent-contact constant-amplitude AFM [5], a constant cantilever oscillation amplitude is maintained by feeding back the demodulated fundamental amplitude of the deflection signal. The imaging of delicate biological samples [6][7][8] is

• provide further nanomechanical sample information. These include properties such as sample elasticity, stiffness and adhesiveness [17], which are mapped simultaneously with the topography. Acquiring these observables requires the accurate demodulation of amplitude and phase of multiple frequency

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

• 10.3762/bjnano.9.47 Abstract An important issue in the emerging field of multifrequency atomic force microscopy (MF-AFM) is the accurate and fast demodulation of the cantilever-tip deflection signal. As this signal consists of multiple frequency components and noise processes, a lock-in amplifier is

• typically employed for its narrowband response. However, this demodulator suffers inherent bandwidth limitations as high-frequency mixing products must be filtered out and several must be operated in parallel. Many MF-AFM methods require amplitude and phase demodulation at multiple frequencies of interest

• , 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

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

• -range electrostatic forces between the cantilever and sample structures, force-gradient sensitive detection is required [7][19]. In our setup, this is assured by direct demodulation of the sidebands that appear upon electrical modulation of the tip–sample electrostatic force [20]. Figure 2b shows the

A review of demodulation techniques for amplitude-modulation atomic force microscopy

• Michael G. Ruppert,
• David M. Harcombe,
• Michael R. P. Ragazzon,
• S. O. Reza Moheimani and
• Andrew J. Fleming

Beilstein J. Nanotechnol. 2017, 8, 1407–1426, doi:10.3762/bjnano.8.142

• Technology, Trondheim, Norway Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX, USA 10.3762/bjnano.8.142 Abstract In this review paper, traditional and novel demodulation methods applicable to amplitude-modulation atomic force microscopy are implemented on a widely

• frequency components. Specifically for modern multifrequency techniques, where higher harmonic and/or higher eigenmode contributions are present in the oscillation signal, the fidelity of the estimates obtained from some demodulation techniques is not guaranteed. To enable a rigorous comparison, the

• -modulation AFM [14] have also been used. Situated at the heart of these dynamic methods, a demodulator is employed to estimate amplitude and phase of the cantilever deflection signal. A number of demodulation techniques can be found in the existing literature, some of which have found regular use in

Multimodal cantilevers with novel piezoelectric layer topology for sensitivity enhancement

• Steven Ian Moore,
• Michael G. Ruppert and
• Yuen Kuan Yong

Beilstein J. Nanotechnol. 2017, 8, 358–371, doi:10.3762/bjnano.8.38

• actively driven cantilever and subsequent demodulation using a lock-in amplifier. Therefore, the subsequent noise characterization is for the demodulated amplitude signal. A 4th-order low-pass filter with cut-off frequency fc = 1 kHz is employed in the lock-in amplifier (Zurich Instruments, HF2LI). The

Noise in NC-AFM measurements with significant tip–sample interaction

• Jannis Lübbe,
• Matthias Temmen,
• Philipp Rahe and
• Michael Reichling

Beilstein J. Nanotechnol. 2016, 7, 1885–1904, doi:10.3762/bjnano.7.181

• between the amplitude and tip–sample distance control loops of the NC-AFM system as well as by the characteristics of the phase locked loop (PLL) detector used for frequency demodulation. Here, we measure DΔf(fm) for various NC-AFM parameter settings representing realistic measurement conditions and

• for frequency demodulation and amplitude stabilisation. This control system encodes the frequency shift Δf in volts using SΔf = −30 Hz/V. For the distance control loop, we employ a digital PI controller of the HF2LI device (Zurich Instruments AG, Zürich, Switzerland) as this instrument provides loop

High-bandwidth multimode self-sensing in bimodal atomic force microscopy

• Michael G. Ruppert and
• S. O. Reza Moheimani

Beilstein J. Nanotechnol. 2016, 7, 284–295, doi:10.3762/bjnano.7.26

• the first mode is below the sensitivity of the charge sensor associated with that mode. As the use of the charge sensor in amplitude modulation AFM always requires demodulation, we state the total integrated noise from the voltage noise density (ND) plot and standard deviation (RMS noise) of the

• that mode and the fact that the cantilever is actively driven at resonance. However, the authors believe that the procedure is closer to the actual dynamic AFM application (using lock-in demodulation of actively driven cantilevers) and therefore the values reported are a realistic representation of

• determined from narrowband demodulation (ZoomFFT, HF2LI Zürich Instruments) at a frequency span of 14.4 kHz around the resonance frequency of interest. The results for driving the fundamental mode at an amplitude of 253 nm are presented in Figure 8b.1 and Figure 8b.2, yielding a SNR of the OBD sensor of

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

• superior resolution of FM-KFM while maintaining robust topography feedback and minimal crosstalk, we introduce a novel FM-KFM controller based on a Kalman filter and direct demodulation of sidebands. We discuss the origin of sidebands in FM-KFM irrespective of the cantilever quality factor and how direct

• sideband demodulation enables robust amplitude modulated topography feedback. Finally, we demonstrate our single-scan FM-KFM technique on an active nanoelectronic device consisting of a 70 nm diameter InAs nanowire contacted by a pair of 120 nm thick electrodes. Keywords: capacitive crosstalk; frequency

• normalisation approaches [34], this strategy does not increase the noise level. We have tested performance on an InAs nanowire device with rough surface and abrupt height variations, which pose severe challenges to both traditional single-scan and lift-mode FM-KFM setups. Since direct sideband demodulation

Noise performance of frequency modulation Kelvin force microscopy

• Heinrich Diesinger,
• Dominique Deresmes and
• Thierry Mélin

Beilstein J. Nanotechnol. 2014, 5, 1–18, doi:10.3762/bjnano.5.1

• resonance frequency. A modulation of Δf at a frequency within the bandwidth of the distance controller would cause the distance controller to retract the tip periodically. Therefore, by modulation and demodulation, the electrostatically induced tip frequency modulation is translated in a range above the

• contains amplitude and sign of the CPD. It is detected by demodulating at fmod. The PLL response HPLL(fmod) applies before the demodulation. The static forward gain AK,DC is: The static forward gain is determined with engaged distance control loop while using a setpoint of Δf = −5 Hz with Vmod = 300 mV

Determining cantilever stiffness from thermal noise

• Jannis Lübbe,
• Matthias Temmen,
• Philipp Rahe,
• Angelika Kühnle and
• Michael Reichling

Beilstein J. Nanotechnol. 2013, 4, 227–233, doi:10.3762/bjnano.4.23

• demodulator tuned to the cantilever eigenfrequency. Effectively, the PLL projects the displacement noise power spectral density in the sidebands of the mode resonance into a range of frequencies fm starting at 0 Hz. Considering the transfer function of the demodulation and the transfer function of the PLL

Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy

• Jannis Lübbe,
• Matthias Temmen,
• Sebastian Rode,
• Philipp Rahe,
• Angelika Kühnle and
• Michael Reichling

Beilstein J. Nanotechnol. 2013, 4, 32–44, doi:10.3762/bjnano.4.4

• by the amplitude feedback loop. Signal processing in NC-AFM involves the demodulation of the periodic cantilever-displacement signal Vz(t) as well as filtering in the frequency domain to yield the frequency shift Δf(t) carrying the information on the tip–surface interaction [1]. Demodulation is

• power spectral density DΔf(fm) by the demodulation process. The noise contribution in this spectrum is the most relevant noise figure in NC-AFM measurements and can be calculated from the demodulator input noise by applying the appropriate demodulator transfer function and an approximation to obtain a

• (Nanosurf AG, Liestal, Switzerland) for frequency demodulation. The AFM/STM setup has been modified by replacing the light source (light-emitting diode exchanged with a laser diode) and using optimised preamplifiers. Preamplifiers have been optimised for low-noise operation at frequencies around 100 kHz and

Nano-FTIR chemical mapping of minerals in biological materials

• Sergiu Amarie,
• Paul Zaslansky,
• Yusuke Kajihara,
• Erika Griesshaber,
• Wolfgang W. Schmahl and
• Fritz Keilmann

Beilstein J. Nanotechnol. 2012, 3, 312–323, doi:10.3762/bjnano.3.35

• within 7 cm−1 (between 90% and 10% of the peak amplitude); the response is even sharper because our present instrumental resolution is about 6 cm−1 [3]. Additionally, Figure 12b shows that the resonance becomes narrowed simply by choosing a higher order n of signal demodulation (see Experimental section

• optimal working settings of the tapping amplitude, the demodulation order n, and the focusing. In the monochromatic infrared near-field imaging mode of the s-SNOM a line-tunable CO2 laser attenuated to 10 mW is used for illumination. The acquisition time was 5 ms per pixel, requiring several minutes for a

• about 8 cm−1, and the shown result is an average over five consecutive scans. Figure 12b illustrates that the use of the n = 3 instead of the n = 2 demodulation order reduces the apatite resonance halfwidth by 40%. However, this is paid for by a five-fold reduction of the amplitude, as noted with other

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

• dynamic behavior of the oscillator. Briefly speaking, an important element of the FM-AFM experimental apparatus is the frequency detection by demodulation performed with the aid of a phase-locked loop (PLL). This allows measurement of the frequency shift Δf from the fundamental resonance frequency of the

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

• voltage and the sample holder is grounded. NanoSurf EasyPLL is used for the FM demodulation and the Omicron MATRIX control system for the data acquisition. The qPlus sensors were built from commercially available tuning forks from Micro Crystal, originally packed in the SMD package MS1V-T1K. The original

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

• one used for KFM in the non-contact regime [4] with the following variations. LIA-1 is used for both the AM topography servo and the demodulation of the side bands of the drive frequency. In [4] a separate PLL was used for the FM topography servo, and the drive out from the FM controller served as the