Preparation and characterization of AFM tips with nitrogen-vacancy and nitrogen-vacancy-nitrogen color centers

We demonstrate a simple dip-coating method of covering standard AFM tips with nanodiamonds containing color centers. Such coating enables convenient visualization of AFM tips above transparent samples as well as using the tip for performing spatially resolved magnetometry. Full Text: PDF ReferencesG. Binnig, C. F. Quate, C. Gerber, "Atomic Force Microscope", Phys. Rev. Lett. 56, 930 (1986). CrossRef F .J. Giessibl, "Advances in atomic force microscopy", Rev. Mod. Phys. 75, 949 (2003). CrossRef S. Kasas, G. Dietler, "Probing nanomechanical properties from biomolecules to living cells", Eur. J. Appl. Physiol. 456, 13 (2008). CrossRef C. Roduit et al., "Stiffness Tomography by Atomic Force Microscopy", Biophys. J. 97, 674 (2009). CrossRef L. A. Kolodny et al., "Spatially Correlated Fluorescence/AFM of Individual Nanosized Particles and Biomolecules", Anal. Chem. 73, 1959 (2001). CrossRef L. Rondin et al., "Magnetometry with nitrogen-vacancy defects in diamond", Rep. Prog. Phys. 77, 056503 (2014). CrossRef C. L. Degen, "Scanning magnetic field microscope with a diamond single-spin sensor", Appl. Phys. Lett. 92, 243111 (2008). CrossRef J. M. Taylor et al., "High-sensitivity diamond magnetometer with nanoscale resolution", Nat. Phys. 4, 810 (2008). CrossRef J. R. Maze et al., "Nanoscale magnetic sensing with an individual electronic spin in diamond", Nature 455, 644 (2008). CrossRef L. Rondin et al., "Nanoscale magnetic field mapping with a single spin scanning probe magnetometer", Appl. Phys. Lett. 100, 153118 (2012). CrossRef J. P. Tetienne et al., "Nanoscale imaging and control of domain-wall hopping with a nitrogen-vacancy center microscope", Science 344, 1366 (2014). CrossRef R. Nelz et al., "Color center fluorescence and spin manipulation in single crystal, pyramidal diamond tips", Appl. Phys. Lett. 109, 193105 (2016). CrossRef G. Balasubramanian et al., "Nanoscale imaging magnetometry with diamond spins under ambient conditions", Nature 455, 648 (2008). CrossRef P. Maletinsky et al., "A robust scanning diamond sensor for nanoscale imaging with single nitrogen-vacancy centres", Nat. nanotechnol. 7, 320 (2012). CrossRef L. Thiel et al., "Quantitative nanoscale vortex imaging using a cryogenic quantum magnetometer", Nat. nanotechnol. 11, 677 (2016). CrossRef F. Jelezko et al., "Single spin states in a defect center resolved by optical spectroscopy", Appl. Phys. Lett. 81, 2160 (2002). CrossRef M. W. Doherty et al., "The nitrogen-vacancy colour centre in diamond", Phys. Rep. 528, 1 (2013). CrossRef C. Kurtsiefer, S. Mayer, P. Zarda, H. Weinfurter, "Stable Solid-State Source of Single Photons", Phys. Rev. Lett. 85, 290 (2000). CrossRef A. Gruber, A. Dräbenstedt, C. Tietz, L. Fleury, J. Wrachtrup, C. Von Borczyskowski, "Scanning Confocal Optical Microscopy and Magnetic Resonance on Single Defect Centers", Science 276, 2012 (1997). CrossRef F. Dolde et al., "Electric-field sensing using single diamond spins", Nat. Phys. 7, 459 (2011). CrossRef K. Sasaki et al., "Broadband, large-area microwave antenna for optically detected magnetic resonance of nitrogen-vacancy centers in diamond", Rev. Sci. Instrum. 87, 053904 (2016). CrossRef A. M. Wojciechowski et al., "Optical Magnetometry Based on Nanodiamonds with Nitrogen-Vacancy Color Centers", Materials 12, 2951 (2019). CrossRef I. V. Fedotov et al., "Fiber-optic magnetometry with randomly oriented spins", Opt. Lett. 39, 6755 (2014). CrossRef

Tip Treatment

This chapter discusses various methods for tip treatment. First, a general discussion about the experimental facts of STM and AFM tips is presented, which points to the subtleties and significance of the last few atoms at the tip apex. The standard method of making an STM tip is the electrochemical etching of a tungsten wire. The experimental procedure is described in detail. The study of the tip using field-ion microscopy is outlined. The tungsten tips freshly made from electrochemical etching often do not provide atomic resolution. Ex-situ and in-situ tip treatments are necessary. Several ex-situ tip treatment methods are described, inducing annealing, field evaporation, and annealing with a field. In-situ tip treatment method such as high-field treatment and controlled collision are described. Then, tip treatment for electrochemical STM is described. Tip treatment methods for spin-polarized STM are described. Finally, tip functionalization, especially with Xe atom and CO molecule, is described.

Local, Single-Molecule Oxidative Cleaving of DNA Origami by C60 on an AFM Tip

Spatially controlled single-molecule oxidation of DNA was performed by photocatalytic generation of singlet oxygen on chemically functionalized AFM tips. A waffle-type DNA origami deposited on a mica surface is site-specifically destroyed by generation of reactive oxygen species at the AFM tip, which was modified with C₆₀-tripod photocatalyst. Upon AFM scanning under photoirradiation, DNA morphology changes, corresponding to oxidative damage were clearly observed at the single-molecule level. The DNA cleavage occurred with strict dependence on photoirradiation and the presence of C₆₀on the AFM tip.

Local, Single-Molecule Oxidative Cleaving of DNA Origami by C60 on an AFM Tip

Spatially controlled single-molecule oxidation of DNA was performed by photocatalytic generation of singlet oxygen on chemically functionalized AFM tips. A waffle-type DNA origami deposited on a mica surface is site-specifically destroyed by generation of reactive oxygen species at the AFM tip, which was modified with C₆₀-tripod photocatalyst. Upon AFM scanning under photoirradiation, DNA morphology changes, corresponding to oxidative damage were clearly observed at the single-molecule level. The DNA cleavage occurred with strict dependence on photoirradiation and the presence of C₆₀on the AFM tip.

Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

Surfactant molecules, known as organic friction modifiers (OFMs), are routinely added to lubricants to reduce friction and wear between sliding surfaces. In macroscale experiments, friction generally decreases as the coverage of OFM molecules on the sliding surfaces increases; however, recent nanoscale experiments with sharp atomic force microscopy (AFM) tips have shown increasing friction. To elucidate the origin of these opposite trends, we use nonequilibrium molecular dynamics (NEMD) simulations and study kinetic friction between OFM monolayers and an indenting nanoscale asperity. For this purpose, we investigate various coverages of stearamide OFMs on iron oxide surfaces and silica AFM tips with different radii of curvature. We show that the differences between the friction-coverage relations from macroscale and nanoscale experiments are due to molecular plowing in the latter. For our small tip radii, the friction coefficient and indentation depth both have a non-monotonic dependence on OFM surface coverage, with maxima occurring at intermediate coverage. We rationalise the non-monotonic relations through a competition of two effects (confinement and packing density) that varying the surface coverage has on the effective stiffness of the OFM monolayers. We also show that kinetic friction is not very sensitive to the sliding velocity in the range studied, indicating that it originates from instabilities. Indeed, we find that friction predominately originates from plowing of the monolayers by the leading edge of the tip, where gauche defects are created, while thermal dissipation is mostly localised in molecules towards the trailing edge of the tip, where the chains return to a more extended conformation.<br>

Benchmarking atomically defined AFM tips for chemical-selective imaging

Controlling the identity of the tip-terminating atom or molecule in low-temperature atomic force microscopy has led to ground breaking progress in surface chemistry and nanotechnology. Lacking a comparative tip-performance assessment,...

Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

<div>Surfactant molecules, known as organic friction modi?ers (OFMs), are added to lubricants to reduce friction and wear between sliding surfaces. In macroscale experiments, friction generally decreases as the coverage of OFM molecules on the sliding surfaces increases. However, recent nanoscale experiments with sharp atomic force microscopy (AFM) tips have shown increasing friction. To elucidate the origin of these opposite trends, we use nonequilibrium molecular dynamics (NEMD) simulations and study kinetic friction between OFM monolayers and an indenting nanoscale asperity. For this purpose, we study various coverages of stearamide OFMs on iron oxide surfaces and silica AFM tips with different radii of curvature. For our small tip radii, the friction coefficient and indentation depth both have a non-monotonic dependence on OFM surface coverage, with maxima occurring at intermediate coverage. This suggests that friction is dominated by plowing. We rationalise the non-monotonic relations through</div><div>a competition of two effects (confinement and packing density) that varying the surface coverage has on the effective stiffness of the OFM monolayers. We also show</div><div>that kinetic friction is not very sensitive to the sliding velocity in the range studied, indicating that it originates from instabilities. Indeed, while friction predominately</div><div>originates from the plowing action of the monolayers by the leading edge of the tip, thermal dissipation is mostly localised in molecules towards the trailing edge of the tip.</div>

Scale-Dependent Friction-Coverage Relations and Non-Local Dissipation in Surfactant Monolayers

<div>Surfactant molecules, known as organic friction modi?ers (OFMs), are added to lubricants to reduce friction and wear between sliding surfaces. In macroscale experiments, friction generally decreases as the coverage of OFM molecules on the sliding surfaces increases. However, recent nanoscale experiments with sharp atomic force microscopy (AFM) tips have shown increasing friction. To elucidate the origin of these opposite trends, we use nonequilibrium molecular dynamics (NEMD) simulations and study kinetic friction between OFM monolayers and an indenting nanoscale asperity. For this purpose, we study various coverages of stearamide OFMs on iron oxide surfaces and silica AFM tips with different radii of curvature. For our small tip radii, the friction coefficient and indentation depth both have a non-monotonic dependence on OFM surface coverage, with maxima occurring at intermediate coverage. This suggests that friction is dominated by plowing. We rationalise the non-monotonic relations through</div><div>a competition of two effects (confinement and packing density) that varying the surface coverage has on the effective stiffness of the OFM monolayers. We also show</div><div>that kinetic friction is not very sensitive to the sliding velocity in the range studied, indicating that it originates from instabilities. Indeed, while friction predominately</div><div>originates from the plowing action of the monolayers by the leading edge of the tip, thermal dissipation is mostly localised in molecules towards the trailing edge of the tip.</div>

3D-printed cellular tips for tuning fork atomic force microscopy in shear mode

Conventional atomic force microscopy (AFM) tips have remained largely unchanged in nanomachining processes, constituent materials, and microstructural constructions for decades, which limits the measurement performance based on force-sensing feedbacks. In order to save the scanning images from distortions due to excessive mechanical interactions in the intermittent shear-mode contact between scanning tips and sample, we propose the application of controlled microstructural architectured material to construct AFM tips by exploiting material-related energy-absorbing behavior in response to the tip–sample impact, leading to visual promotions of imaging quality. Evidenced by numerical analysis of compressive responses and practical scanning tests on various samples, the essential scanning functionality and the unique contribution of the cellular buffer layer to imaging optimization are strongly proved. This approach opens new avenues towards the specific applications of cellular solids in the energy-absorption field and sheds light on novel AFM studies based on 3D-printed tips possessing exotic properties.