Atomic Force Microscopy Manipulation Research Articles

Atomic, molecular, charge manipulation and application of atomic force microscopy

In this review paper, we introduce representative research work on single atomic/molecular manipulations by atomic force microscopy (AFM), which possesses extraordinary ability to resolve atomic and chemical bonds, and charge density distributions of samples. We first introduce the working principle of AFM, then focus on recent advances in atom manipulation at room temperature, force characterization in the process of atom/molecule manipulation, and charge manipulation on insulating substrates. This review covers the following four aspects: 1) the imaging principle of AFM and the atomic characterization of typical molecules such as pentacene and C<sub>60</sub>; 2) the mechanical manipulation and atomic recognition capability of AFM at room temperature; 3) the characterization of forces in the process of surface isomerization and adsorption configuration changes of the molecules; 4) the manipulation of charge states and the characterization of single and multiple molecules on insulating substrates. The capability of manipulation by AFM in these fields widens the range in atomic/molecular manipulation, which can provide new and well-established schemes for the analysis and precise control of the manipulation process, and can further contribute to the construction of nanoscale devices, such as “molecular switches” and storage components.

In Situ Observation of Surface-Enhanced Raman Scattering from Silver Nanoparticle Dimers and Trimers Fabricated Using Atomic Force Microscopy Manipulation

The generation of surface-enhanced Raman scattering (SERS) was directly observed in situ during the fabrication of Ag nanoparticle (AgNP) dimers and trimers using atomic force microscopy (AFM) manipulation, and the size of the SERS hot spot was estimated using the super-resolution imaging technique. SERS from 4,4’-bipyridine was observed upon the fabrication of the AgNP dimers and trimers using AFM manipulation. Then, the SERS spots were analyzed by fitting with the point spread function for super-resolution imaging. The distribution of the centroid position of the SERS spot from the AgNP dimer was 9 nm along the x-axis and 8 nm along the y-axis, which represent the size of the SERS hot spot. The same technique was applied to the AgNP trimer. The obtained results are important not only for the SERS technique but also for other plasmon enhancement techniques which are useful in a wide range of research areas.

Cellular Shear Adhesion Force Measurement and Simultaneous Imaging by Atomic Force Microscope

This paper presents a sensitive and fast cellular shear adhesion force measurement method that uses atomic force microscopy (AFM). AFM is used both as a tool for imaging cells on the nano-scale and as a force sensor for the measurement of the shear adhesion force between a cell and the substrate. After cell imaging, the measurement of cellular shear adhesion force is made based on the different positions of the cell on the nano-scale. Moreover, various pushing speeds of probe and various locations of cells were used in experiments to study their influences. It was found that the measurement of cell adhesion in the upper portion of the cell is different from that in the lower portion. This may reveal that cancer cells have high metastasis tendency after culture for 16–20 h, which is significant for preventing metastasis in patients diagnosed with early cancer lesions. Furthermore, the cellular shear adhesion forces of two types of living cancer cell were obtained based on the measurements of AFM cantilever deflections in the torsional and vertical directions. The results demonstrate that the shear adhesion force of cancer cells is twice as much as that of the same type of cancer cells with tumor-necrosis-factor-related apoptosis-inducing ligand. The proposed method can also be used to measure the cellular shear adhesion force between a cell and the substrate, and for the simultaneous exploration of cells using AFM imaging and manipulation.

Graphene: Graphene Nanoribbons Under Mechanical Strain (Adv. Mater. 2/2015)

On page 303, C. Chen, J. Guo, H. Dai, and co-workers introduce uniaxial strains (0-6%) into individual graphene nanoribbons (GNRs) with highly smooth edges for the first time by atomic force microscopy manipulation and investigate strain effects on GNRs. It is found that uniaxial strain downshifts the Raman G-band frequency of GNRs linearly and tunes their bandgap significantly in a non-monotonic manner. Strain engineering of GNRs is demonstrated to be promising for modulating the properties of GNRs toward potential device applications.

Long Jumps of an Organic Molecule Induced by Atomic Force Microscopy Manipulation

Non‐contact atomic force microscopy at cryogenic temperatures is used for the controlled lateral manipulation of individual 3,4,9,10‐perylene‐tetracarboxylicacid‐dianhydride (PTCDA) molecules on the Ag(111) surface. The molecules are moved along the [‐110] direction of the Ag lattice in the regime of repulsive tip‐molecule forces performing discrete jumps that span distances from single to multiple lattice spacings. The analysis of the two‐dimensional force field measured before and during the manipulation reveals that the displacement beyond nearest neighbor sites cannot be explained by long range tip‐molecule forces but instead has to involve an energy transfer to translational modes of the molecule. Combined with the results of the simultaneous measurement of the energy dissipation, these findings allow to identify a likely manipulation mechanism and provide insight into the process of energy transfer between excited large molecules and metal surfaces. Furthermore, implications for the theoretical treatment of NC‐AFM based molecule manipulation are discussed.

Different tips for high-resolution atomic force microscopy and scanning tunneling microscopy of single molecules

We explore different tip functionalizations for atomic force microscopy (AFM), scanning tunneling microscopy (STM), and Kelvin probe force microscopy (KPFM) of organic molecules on thin insulating films. We describe in detail how tips terminated with single Br and Xe atoms can be created. The performance of these tips in AFM, STM, and KPFM imaging of single molecules is compared to other tip terminations, and the advantages and disadvantages of the different tips are discussed. The Br tip was found to be particularly useful for AFM and lateral manipulation, whereas the Xe tip excelled in STM and KPFM.

Bending manipulation and measurements of fracture strength of silicon and oxidized silicon nanowires by atomic force microscopy

Abstract

Friction Measurements of InAs Nanowires on Silicon Nitride by AFM Manipulation

A study was conducted to perform friction measurements of InAs nanowires (NW) on silicon nitride (Si 3N 4) through atomic force microscopy (AFM) manipulation. The investigations revealed the friction force per unit length for sliding and static friction over a range of nanowire diameters. It was found that there is a significant difference between the coefficients of the two sliding modes for large wires. It was also found that the difference between the two sliding modes disappears at smaller diameters and the sliding friction becomes equal with the static friction. The AFM investigations were performed on a Nanoscope IIIa Dimension 3100, using rectangular cantilevers, with a nominal spring constant of 30 N m -1. The nanowires were manipulated, using the 'Retrace Lift' mode of the AFM controller. The friction force per unit length was gathered from the local curvature of the NWs, using standard elasticity theory.

Synthesis, Characterization, and Manipulation of Nitrogen-Doped Carbon Nanotube Cups

Isolated, carbon nanotube cups with diameters of 12-40 nm have been synthesized by chemical vapor deposition through incorporation of nitrogen atoms into graphitic carbon structure and subsequent mechanical separation. Incorporation of nitrogen affords carbon nanotube cups with a unique composition comprising multiwalled, graphitic lattice with nitrogen groups on the exterior rim and hollow interior cavities. These nanostructures demonstrate the ability to participate in hydrogen bonding because of nitrogen functionalities on their open edges. Furthermore, reaction with these nitrogen functionalities results in the coupling of gold nanoparticles (GNPs) to the open rim of carbon nanotube cups. Through atomic force microscopy manipulation and adhesion force measurements, we compare the mobility of these structures on a hydrophilic surface before and after GNP coupling. Understanding of these forces will aid in useful nanostructure assembly for energy and biomedical applications.

Fabrication of Carbon Nanotube Diode with Atomic Force Microscopy Manipulation

We presented a controllable yet simple approach for fabricating an air-stable single-walled carbon nanotube (SWNT) diode with the atomic force microscopy (AFM) manipulation technique. The AFM tip w...

Atomic force microscopy manipulation with ultrasonic excitation

The exposure of nanostructures to ultrasound renders the opportunity to explore novel methods to control their assembly. In the presence of surface ultrasonic vibration, large Sb nanoparticles on MoS2 substrates can be laterally displaced using the tip of a compliant AFM cantilever by just increasing the ultrasonic excitation amplitude. Magnetic nanoparticles of about 10–2 nm in diameter are swept by the tip when scanning in contact mode in the absence of ultrasound, but remain undisturbed in the presence of low amplitude ultrasonic vibration. In Atomic Force Microscopy-assisted manipulation of nanoparticles, ultrasonic vibration affects both tip-particle and particle-surface frictional properties.

Sorting out Semiconducting Single-Walled Carbon Nanotube Arrays by Preferential Destruction of Metallic Tubes Using Xenon-Lamp Irradiation

We report herein a simple and reliable approach to prepare densely packed, well-aligned individual semiconducting single-walled carbon nanotube (s-SWNT) arrays using long-arc xenon-lamp (Xe-lamp) irradiation. The densely packed, well-aligned individual SWNT arrays (the mean density was ∼20 tubes/μm) were first grown on a-plane sapphire using ethanol containing 3 wt % water as the carbon source. It is found that water plays a key role in the improvement of the density and the alignment of the SWNT arrays. The densely packed aligned SWNT arrays were then irradiated by a long-arc Xe lamp. Atomic force microscopy manipulation, Raman spectroscopy, and electrical transport measurement revealed that the SWNTs with small diameters (d < 1 nm) and the metallic SWNTs (m-SWNTs) in the arrays can be preferentially destroyed, thus leaving s-SWNT arrays on the surface. In general, for the SWNTs with diameters in the region of 1.15−1.55 nm, the percentage of s-SWNTs increased from ca. 50% to 95% after 60 min of irradiati...

Optimization of specimen preparation of thin cell section for AFM observation

High resolution imaging of intracellular structures of ultrathin cell section samples is critical to the performance of precise manipulation by atomic force microscopy (AFM). Here, we test the effect of multiple factors during section sample preparation on the quality of the AFM image. These factors include the embedding materials, the annealing process of the specimen block, section thickness, and section side. We found that neither the embedding materials nor the temperature and speed of the annealing process has any effect on AFM image resolution. However, the section thickness and section side significantly affect the surface topography and AFM image resolution. By systematically testing the image quality of both sides of cell sections over a wide range of thickness (40–1000 nm), we found that the best resolution was obtained with upper-side sections approximately 50–100 nm thick. With these samples, we could observe precise structure details of the cell, including its membrane, nucleoli, and other organelles. Similar results were obtained for other cell types, including Tca8113, C6, and ECV-304. In brief, by optimizing the condition of ultrathin cell section preparation, we were able to obtain high resolution intracellular AFM images, which provide an essential basis for further AFM manipulation.

Open micro-fluidic system for atomic force microscopy-guided in situ electrochemical probing of a single cell

Ultra-sharp nano-probes and customized atomic force microscopy (AFM) have previously been developed in our laboratory for in situ sub-cellular probing of electrochemical phenomena in living plant cells during their photosynthesis. However, this AFM-based electrochemical probing still has numerous engineering challenges such as immobilization of the live cells, compatibility of the immobilization procedure with AFM manipulation of the probe, maintenance of biological activity of the cells for an extended time while performing the measurements, and minimization of electrochemical noise. Thus, we have developed an open micro-fluidic channel system (OMFC) in which individual cells can be immobilized in micro-traps by capillary flow. This system affords easy AFM access and allows for maintenance of the cells in a well-defined chemical environment, which sustains their biological activity. The use of micro-channels for making the electrochemical measurements significantly reduces parasitic electrical capacitances and allows for current detection in the sub-pico-ampere range at high signal bandwidths. The OMFC was further studied using simulation packages for optimal design conditions. This system was successfully used to measure light-dependent oxidation currents of a few pico-amperes from the green alga Chlamydomonas reinhardtii.

Resonant Raman Spectroscopy of Individual Strained Single-Wall Carbon Nanotubes

Resonance Raman spectra of individual strained ultralong single-wall carbon nanotubes (SWNTs) are studied. Torsional and uniaxial strains are introduced by atomic force microscopy manipulation. Torsional strain strongly affects the Raman spectra, inducing a large downshift in the E2 symmetry mode in the G+ band, but a slight upshift for the rest of the G modes and also an upshift in the radial breathing mode (RBM). Whereas uniaxial strain has no effect on the frequency of either the E2 symmetry mode in the G+ band or the RBM, it downshifts the rest of the G modes. The Raman intensity change reflects the effect of these strains on the SWNT electronic band structure.

Nanomanipulation of sections of human tongue squamous cell carcinoma by atomic force microscopy

To investigate the appropriate nanomanipulation of slides of human tongue squamous cell carcinoma tissue and cultured cells by atomic force microscopy (AFM), and develop methods to improve the resolution and contrast of AFM images. Human tongue squamous carcinoma cells of the line Tca8113 were cultured. Cell masses were isolated and collected, and sectioned. Then the white lead and silvery white sections were transferred on mica slides, dried. Eighty slides were used and divided into 2 groups to be immersed into hydrogen dioxide of the concentrations 20% and 30% for 0, 5, 10, 15, 20, 25, 30, and 40 min respectively. Samples of human tongue squamous carcinoma were collected from 15 cases. Every sample was divided into 2 halves. Half of every sample underwent routine paraffin preparation of slide and adhered onto glass, dissolving of paraffin with dimethylbenzene for 0, 10, 15, 30, 45, or 60 min; and half of the sample underwent routine preparation of slides for electron microscopy, the white lead and silvery white sections were transferred on mica slides, dried. The slides were observed by contact mode AFM in air. In the ultrathin sections the metastructure of the cell such as the cell membrane, nuclear membrane and nucleolus could be distinct from each other clearly. The profile of the cell and the nucleus inside could be revealed by AFM after the paraffin sections were treated in dimethylbenzene for 15-30 min. AFM manipulation could be achieved within nanometer range by precise modulation of scanning force, area, angle and so on. The appropriate needle point should contain elastic coefficient > 5.0 N/m. The force exerted on the needle point should be within the range 50-300 nN. After location the scanning direction should be within the range of 20 nm-1 microm. A series of modified techniques of preparing and treating AFM samples, such as adhering the sections onto mica slide, dissolving of epoxy resin by hydrogen dioxide and removal of paraffin by dimethylbenzene, were developed, thus realizing high resolving power AFM imaging, especially for nuclear membrane, and nucleolus, and providing a base of AFM location, dissection, isolation and obtainment at nanometer scale.

Controlled synthesis and manipulation of ZnO nanorings and nanobows

An experimental procedure is presented for the controlled synthesis and manipulation of ZnO nanorings and nanobows at high purity and large yield. Atomic force microscopy manipulation of the nanostructures demonstrates their mechanical toughness and flexibility. Extensive bending of the nanorings and nanobows suggests an extremely high deformation limit with the potential for building ultrasensitive electromechanical coupled nanoscale sensors, transducers, and resonators.

Single-electron tunneling effects in a metallic double dot device

We report on differential conductance measurements on a gold double-dot structure at 4.2 K. The two dots were connected in series by tunnel junctions formed by atomic force microscopy manipulation of nanodisks. The tunnel junctions were made strongly asymmetric. The characteristic honeycomb-shaped charging diagram separating different Coulomb blockade regions of well-defined occupancy of electrons was observed and the cells in the charging diagram were found to be skewed by the asymmetry of the tunnel junctions. In addition, a double-dot Coulomb staircase structure, with steps of varying width, was observed and was studied for varying gate voltage. The occupancy of electrons on the two dots was determined as a function of both drain source and gate voltages.

Plasmonics-A Route to Nanoscale Optical Devices

The further integration of optical devices will require the fabrication of waveguides for electromagnetic energy below the diffraction limit of light. We investigate the possibility of using arrays of closely spaced metal nanoparticles for this purpose. Coupling between adjacent particles sets up coupled plasmon modes that give rise to coherent propagation of energy along the array. A point dipole analysis predicts group velocities of energy transport that exceed 0.1c along straight arrays and shows that energy transmission and switching through chain networks such as corners (see Figure) and tee structures is possible at high efficiencies. Radiation losses into the far field are expected to be negligible due to the near-field nature of the coupling, and resistive heating leads to transmission losses of about 6 dB/μm for gold and silver particles. We analyze macroscopic analogues operating in the microwave regime consisting of closely spaced metal rods by experiments and full field electrodynamic simulations. The guiding structures show a high confinement of the electromagnetic energy and allow for highly variable geometries and switching. Also, we have fabricated gold nanoparticle arrays using electron beam lithography and atomic force microscopy manipulation. These plasmon waveguides and switches could be the smallest devices with optical functionality.

Carbon nanotubes: nanomechanics, manipulation, and electronic devices

Carbon nanotubes are novel materials with unique electrical and mechanical properties. Here we present results on their atomic structure and mechanical properties in the adsorbed state, on ways to manipulate individual nanotubes, on their electrical properties and, finally, on the fabrication and characteristics of nanotube-based electron devices. Specifically, atomic force microscopy (AFM) and molecular mechanics simulations are used to investigate the effects of van der Waals interactions on the atomic structure of adsorbed nanotubes. Both radial and axial structural deformations are identified and the interaction energy itself is obtained from the observed deformations. The conditions under which the structure of a nanotube will adjust to the topography of the substrate are defined. We show that the strong substrate–nanotube interaction allows the manipulation of both the position and shape of individual nanotubes at inert surfaces using the AFM. AFM manipulation is then utilized to position individual nanotubes on electrical pads so that their electrical characteristics can be evaluated. We demonstrate the operation of a field-effect transistor based on a single semiconducting nanotube and of a single-electron transistor using a nanotube bundle as Coulomb island. Finally, conducting nanotubes are employed as tips for AFM lithography.