http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

Based on fundamental chemistry, biotechnology and materials science have developed over the past three decades into today's powerful disciplines which allow the engineering of advanced technical devices and the industrial production of active substances for pharmaceutical and biomedical applications. This review is focused on current approaches emerging at the intersection of materials research, nanosciences, and molecular biotechnology. This novel and highly interdisciplinary field of chemistry is closely associated with both the physical and chemical properties of organic and inorganic nanoparticles, as well as to the various aspects of molecular cloning, recombinant DNA and protein technology, and immunology. Evolutionary optimized biomolecules such as nucleic acids, proteins, and supramolecular complexes of these components, are utilized in the production of nanostructured and mesoscopic architectures from organic and inorganic materials. The highly developed instruments and techniques of today's materials research are used for basic and applied studies of fundamental biological processes.

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Nanoparticles, Proteins, and Nucleic Acids: Biotechnology Meets Materials Science

This article reviews the progress of atomic force microscopy in ultrahigh vacuum, starting with its invention and covering most of the recent developments. Today, dynamic force microscopy allows us to image surfaces of conductors and insulators in vacuum with atomic resolution. The most widely used technique for atomic-resolution force microscopy in vacuum is frequency-modulation atomic force microscopy (FM-AFM). This technique, as well as other dynamic methods, is explained in detail in this article. In the last few years many groups have expanded the empirical knowledge and deepened our theoretical understanding of frequency-modulation atomic force microscopy. Consequently spatial resolution and ease of use have been increased dramatically. Vacuum atomic force microscopy opens up new classes of experiments, ranging from imaging of insulators with true atomic resolution to the measurement of forces between individual atoms.

https://hep.physics.utoronto.ca/WilliamTrischuk/courses/phy189/AFM_revmodphys.pdf

Advances in atomic force microscopy

Dynamic atomic force microscopy methods

Unencapsulated, exfoliated black phosphorus (BP) flakes are found to chemically degrade upon exposure to ambient conditions. Atomic force microscopy, electrostatic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy are employed to characterize the structure and chemistry of the degradation process, suggesting that O2 saturated H2O irreversibly reacts with BP to form oxidized phosphorus species. This interpretation is further supported by the observation that BP degradation occurs more rapidly on hydrophobic octadecyltrichlorosilane self-assembled monolayers and on H-Si(111) versus hydrophilic SiO2. For unencapsulated BP field-effect transistors, the ambient degradation causes large increases in threshold voltage after 6 h in ambient, followed by a ∼103 decrease in FET current on/off ratio and mobility after 48 h. Atomic layer deposited AlOx overlayers effectively suppress ambient degradation, allowing encapsulated BP FETs to ma...

Effective Passivation of Exfoliated Black Phosphorus Transistors against Ambient Degradation

A method is presented to measure the energy dissipated by the tip–sample interaction in tapping-mode atomic force microscopy (AFM). The results show that if the amplitude of the cantilever is held constant, the sine of the phase angle of the driven vibration is then proportional to changes in the tip–sample energy dissipation. This means that images of the cantilever phase in tapping-mode AFM are closely related to maps of dissipation. The maximum dissipation observed for a 4 N/m cantilever with an initial amplitude of 25 nm tapping on a hard substrate at 74 kHz is about 0.3 pW.

Energy dissipation in tapping-mode atomic force microscopy

How to measure energy dissipation in dynamic mode atomic force microscopy

The conservative and dissipative forces between tip and sample of a dynamic atomic force microscopy (AFM) were investigated using a combination of computer simulations and experimental AFM data obtained by the frequency modulation technique. In this way it became possible to reconstruct complete force versus distance curves and damping coefficient versus distance curves from experimental data without using fit parameters for the interaction force and without using analytical interaction models. A comparison with analytical approaches is given and a way to determine a damping coefficient curve from experimental data is proposed. The results include the determination of the first point of repulsive contact of a vibrating tip when approaching a sample. The capability of quantifying the tip-sample interaction is demonstrated using experimental data obtained with a silicon tip and a mica sample in UHV.

/pdf/conservative-and-dissipative-tip-sample-interaction-forces-4yhgk4xjkx.pdf

Conservative and dissipative tip-sample interaction forces probed with dynamic AFM

The high-amplitude dynamic response of cantilever structures as used in scanning force microscopy was investigated as a function of the probe-sample distance. A computer simulation using the Muller-Yushchenko-Derjaguin/Burgess-Hughes-White (MYD/BHW) method applying realistic surface potentials including adhesion was done. The simulation providing dynamic force-distance curves allows us to attribute discontinuities observed in experimental amplitude-distance curves as the transition points from the purely attractive regime to the repulsive interaction near the lower inflection point of the vibrating probe. \textcopyright{} 1996 The American Physical Society.

Cantilever dynamics in quasinoncontact force microscopy: Spectroscopic aspects

The performance of a scanning force microscope (SFM) operated in the dynamic mode at high oscillation amplitudes is determined by the response of the system to a given set of interaction forces between the probing tip and the sample surface. To clarify the details of the cantilever/tip dynamics two different aspects were investigated in experiment and computer simulation. First, the interaction forces dominating the oscillatory motion of the probe were varied by applying an additional electrostatic force field. It is shown that such variations in the attractive part of the interaction potential can cause a switching between two different oscillation states and thereby significantly contribute to the contrast obtained from phase imaging. Secondly, the interaction forces were kept constant but the system response itself was varied by modifying the effective quality factor of the oscillating cantilever with an active feedback circuit. This provides a means to influence the transition from the attractive to the partly repulsive interaction regime, i.e. the onset of the intermittent contact or tapping mode. Operating an SFM in the dynamic mode at high amplitudes (> 10 nm) offers the possibility of minimizing the contact time of the probing tip with the sample surface and thereby reduce lateral or friction forces involved in the scanning process. It also allows the collection of additional data related to different sample properties by recording the phase shift between the force driving the cantilever and its oscillation. In the last few years these features of operating the SFM in the dynamic mode [1, 2] were shown to be very useful to characterize several different kinds of sample surfaces, e.g. thin organic films, polymers, biological samples or even liquid droplets [3]. Although this has led to a steady increase in the number of possible applications, there are still several details of the interaction process between the tip and the sample that need further clarification. The overall goal must be to relate the experimentally accessible data, such as the amplitude and ∗ Corresponding author phase signal, more or less directly to specific sample properties, such as topography, elasticity and viscoelasticity. Because highly nonlinear interaction forces are involved when the oscillating tip is in close proximity to a solid surface, the analysis of the dynamic system becomes quite complex. Therefore supplementary computer simulations based on proper mathematical models are useful to investigate the details of the interaction process. Basically, the equation of motion describing the dynamic properties of the probing tip has to be solved in such a way that the influence of different parameters characterizing the probe as well as the sample surface can be examined. There have been several reports recently on different approaches to this problem, providing analytical [4] as well as numerical [5–11] solutions. Most of them are based on the point-mass model, but there are also approaches which describe the complete flexural motion of the cantilever beam supporting the probing tip, as this becomes more relevant when the system is driven well above its resonance frequency [12]. Thus by simulating the dynamic system one can gain useful information on the complex interaction process of the oscillating tip and the sample surface. 1 Experimental and simulation methods The simulation results presented here are all based on the point-mass model with the interaction forces being derived from MYD/BHW calculations [11, 13, 14] and applying the Verlet algorithm [15] to solve the equation of motion numerically. All experiments were performed with a NanoScope III MultiMode stage (Digital Instruments) equipped with an additional lock-in amplifier (EG&G Instruments, Princeton Applied Research, Model 5302) to measure the phase lag between the driving force and the cantilever response quantitatively. Rectangular cantilevers made of doped silicon (Nanosensors) with a nominal length of L = 125 μm were used. By analogy with measurements of quasistatic forcedistance curves in contact mode, the amplitude and phase shift as a function of the z-position were quantitatively investigated in the dynamic mode by means of simulation and

B. Anczykowski

Papers

Energy dissipation in tapping-mode atomic force microscopy

How to measure energy dissipation in dynamic mode atomic force microscopy

Conservative and dissipative tip-sample interaction forces probed with dynamic AFM

Cantilever dynamics in quasinoncontact force microscopy: Spectroscopic aspects

Analysis of the interaction mechanisms in dynamic mode SFM by means of experimental data and computer simulation