Cyclocarbon...

From left to right, precursor molecule C₂₄O₆, intermediates C₂₂O₄ and C₂₀O₂ and the final product cyclo [18]carbon C₁₈ created on surface by dissociating CO masking groups using atom manipulation. The bottom row shows atomic force microscopy (AFM) data using a CO functionalized tip. Credit: IBM Research

Topics: Applied Physics, Atomic Force Microscopy, Chemistry, Nanotechnology, Research

A team of researchers from Oxford University and IBM Research has for the first time successfully synthesized the ring-shaped multi-carbon compound cyclocarbon. In their paper published in the journal Science, the group describes the process they used and what they learned about the bonds that hold a cyclocarbon together.

Carbon is one of the most abundant elements, and has been found to exist in many forms, including diamonds and graphene. The researchers with this new effort note that much research has been conducted into the more familiar forms (allotropes) how they are bonded. They further note that less well-known types of carbon have not received nearly as much attention. One of these, called cyclocarbon, has even been the topic of debate. Are the two-neighbor forms bonded by the same length bonds, or are there alternating bonds of shorter and longer lengths? The answer to this question has been difficult to find due to the high reactivity of such forms. The researchers with this new effort set themselves the task of finding the answer once and for all.

The team's approach involved creating a precursor molecule and then whittling it down to the desired form. To that end, they used atomic force microscopy to create linear lines of carbon atoms atop a copper substrate that was covered with salt to prevent the carbon atoms from bonding with the subsurface. They then joined the lines of atoms to form the carbon oxide precursor C₂₄O₆, a triangle-shaped form. Next, the team applied high voltage through the AFM to shear off one of the corners of the triangle, resulting in a C₂₂O₄ form. They then did the same with the other two corners. The result was a C₁₈ ring—an 18-atom cyclocarbon. After creating the ring, the researchers found that the bonds holding it together were the alternating long- and short-type bonds that had been previously suggested.

Ring-shaped multi-carbon compound cyclocarbon synthesized, Bob Yirka , Phys.org

How We See the Small...

View of cantilever on an atomic force microscope (magnification 1000x).
Credit: SecretDisc GFDL, CC-BY-SA-3.0

Topics: Atomic Force Microscopy, Nanotechnology, Optics, Scanning Electron Microscope

Cell reproduction, disease detection and semiconductor optimization are just some of the areas of research that have exploited the atomic force microscope. First invented by Calvin Quate, Gerd Binnig and Christoph Gerber in the mid 1980s, atomic force microscopy (AFM) brought the atomic resolution recently achieved by the scanning tunnelling microscope to non-conducting samples, and helped to catalyse the avalanche of science and technology based on nanostructures that now permeates all aspects of modern life from smartphones to tennis rackets. On 6 July 2019 Calvin Quate died aged 95 at his home in Menlo Park, California.

Long before the development of AFM, Quate’s research had made waves in microscopy. 1978 had seen the announcement of the scanning acoustic microscope, which achieved the sensitivity of optical microscopy but probed samples so softly that it could image the interiors of living cells without damaging them. The technique uses high frequency sound waves in place of light, which penetrate deep into structures to image internal structures non-destructively. It is widely used in quality control of electronic component assembly among other applications such as printed circuit boards and medical products.

Advanced microscopy pioneer leaves broad ranging legacy
Anna Demming, Physics World

Nanotomography...

A vertical slice of the internal magnetic structure of a sample section. The sample is 0.005 millimetres (5 microns) in diameter and the section shown here is 0.0036 millimetres (3.6 microns) high. The internal magnetic structure is represented by arrows for a vertical slice within it. In addition, the colour of the arrows indicates whether they are pointing towards (orange) or away from the viewer (purple). Graphics and text: Paul Scherrer Institute/Claire Donnelly

Topics: Atomic Force Microscopy, Atomic Physics, Electromagnetism, Optical Physics, Nanotechnology

Thanks to a technique called hard X-ray magnetic tomography, researchers at the Paul Scherrer Institute (PSI) in Switzerland, the ETH Zurich and the University of Glasgow have succeeded in imaging the magnetization in 3D bulk-like magnets and observe features down to just 100 nm. In particular, they have observed structures known as Bloch points, which were predicted theoretically more than 50 years ago but never actually seen in an experiment until now. The new work could help us better understand the relationship between the magnetic structure and the behaviour and performance of bulk magnets, and so improve the everyday applications in which they are employed.

“Although it was possible to image the arrangement of magnetic moments in 3D before now in films of up to around 200 nm thick using soft X-rays and electrons, it was not possible to study the internal micromagnetic structure of larger, bulk, systems,” explains team member Claire Donnelly of the PSI. “In general, it is not possible to slice down a magnet to investigate its structure because the magnetic configuration will change accordingly. Scientists have tried to overcome this problem in the past using neutron magnetic imaging, but they were only able to achieve a spatial resolution of tens to hundreds of microns using this approach.

“In our new work, we are able to study the internal magnetization within a micron-sized system with 100 nm spatial resolution and observe micromagnetic details within the bulk for the first time.”

The researchers, led by Laura Heyderman, imaged the internal magnetic structure of a micron-sized pillar made of the magnetic material gadolinium-cobalt using hard X-ray magnetic tomography, a technique developed at PSI during the course of this study. “We had to make a number of advances in developing this method,” explains Donnelly. ‘First, we developed hard X-ray magnetic imaging with nanoscale magnetic resolution (this work was published last year). Hard X-rays have a much higher energy than soft X-rays and thus a much larger penetration depth, which allows us to study thicker samples with high spatial resolution.

X-ray nanotomography reveals 3D magnetization structures, Belle Dumé, Nanotechweb.org

INFO...

This image shows the NIST logo made from glowing nanowire LEDs. While the color of the nanowires in the image looks blue, they are actually emitting in the ultraviolet with a wavelength of approximately 380 nm. The other two images, from a scanning electron microscope, show the overall structure of the nanowires.

Topics: Atomic Force Microscopy, LEDs, Nanotechnology, Optical Physics

One of the persistent challenges in 21st century metrology is the need to measure ever-more-detailed properties of ever-smaller things, from microchip features to subcomponents of biological cells. That’s why, four years ago, a team of NIST scientists patented (link is external) the design for a nanoscale probe system that can simultaneously measure the shape, electrical characteristics, and optical response of sample regions a few tens of nanometers (nm, billionths of a meter) wide. 100 nm is about one-thousandth the width of a human hair.

Now the researchers from NIST’s Physical Measurement Laboratory are closing in on a working prototype. The newest version of the device, which has a probe tip that functions as an ultra-tiny LED “spotlight,” holds great promise for identifying cancer-prone tissue, testing materials for improved solar cells, and providing a new way to put circuits on microchips, among other uses.

The Integrated Near-Field Optoelectronic (INFO) system has the general configuration of an atomic force microscope (AFM), in which a probe tip on the end of a tiny cantilever beam passes a few nanometers over the surface of a sample, recording exact details of its morphology. But the metal-plated INFO probe also serves as a transmitter that projects microwaves into the sample as well as a receiving antenna that detects the altered microwaves coming back out. The nature of that alteration reveals electrical and chemical properties of the material.

Sub-microscopic LEDs Shed New Light on Advanced Materials, Ben Stein, NIST

Subatomic Motion Detector...

Images Sources: See link below

Topics: Atomic Force Microscopy, Nanotechnology, NEMS, NIST, Thin Films

Scientists at the National Institute of Standards and Technology (NIST) have developed a new device that measures the motion of super-tiny particles traversing distances almost unimaginably small—shorter than the diameter of a hydrogen atom, or less than one-millionth the width of a human hair. Not only can the handheld device sense the atomic-scale motion of its tiny parts with unprecedented precision, but the researchers have devised a method to mass produce the highly sensitive measuring tool.

It’s relatively easy to measure small movements of large objects but much more difficult when the moving parts are on the scale of nanometers, or billionths of a meter. The ability to accurately measure tiny displacements of microscopic bodies has applications in sensing trace amounts of hazardous biological or chemical agents, perfecting the movement of miniature robots, accurately deploying airbags and detecting extremely weak sound waves traveling through thin films.

NIST physicists Brian Roxworthy and Vladimir Aksyuk describe their work (link is external) in the Dec. 6, 2016, Nature Communications.

The researchers measured subatomic-scale motion in a gold nanoparticle. They did this by engineering a small air gap, about 15 nanometers in width, between the gold nanoparticle and a gold sheet. This gap is so small that laser light cannot penetrate it.

However, the light energized surface plasmons—the collective, wave-like motion of groups of electrons confined to travel along the boundary between the gold surface and the air.

The researchers exploited the light’s wavelength, the distance between successive peaks of the light wave. With the right choice of wavelength, or equivalently, its frequency, the laser light causes plasmons of a particular frequency to oscillate back and forth, or resonate, along the gap, like the reverberations of a plucked guitar string. Meanwhile, as the nanoparticle moves, it changes the width of the gap and, like tuning a guitar string, changes the frequency at which the plasmons resonate.

NIST Device for Detecting Subatomic-Scale Motion Has Potential Robotics, Homeland Security Applications
Ben Stein

30 Years of AFM...

Source: Artificial Oxide Nanostructures: Physics of Multiscale Phenomena

Topics: Atomic Force Microscopy, Biology, Cancer, Consumer Electronics, Electrical Engineering, Nanotechnology, Semiconductor Technology

Thirty years since its first inception, the atomic force microscope has proved a hugely versatile tool. Applications range from quantifying dopant distributions in electronics and the analysis of dust particles in space, to characterizing biopsies for cancer diagnostics. More than simply bringing atomic-scale resolution to non-conducting surfaces, modifications of the technology have provided important tools for sensing chemical entities and mechanical properties, with force sensitivities so great they can be used to study and control mitosis in the proliferation of life itself. nanotechweb.org visited Basel in Switzerland, home to some of the pioneers in AFM technologies, to find out how far the field has come in the past three decades.

The development of scanning probe technologies began with the scanning tunnelling microscope (STM), and was driven by the semiconductor industry in the late 1970s. Christoph Gerber, co-inventor of the atomic force microscope, points out that although electronics feature sizes were coming close to the nanometre scale in the 1970s, there was no way of obtaining spectroscopic information of such small features. “We thought that if we established a tip very close – so that due to the proximity there would be tunnelling - we would have an instrument that could do this kind of spectroscopic work.” From there came the idea of scanning the tip and keeping the quantum tunnelling current constant. This would effectively trace a topography of the surface with a lateral resolution that could image atoms. “The big breakthrough for STM came when we were able to image the 7 × 7 reconstruction of silicon (1,1,1),” explains Gerber. As the arrangement of atoms at the surface differs from the bulk, glimpsing this reconstruction in a real image was a powerful demonstration of the instrument’s potential.

Francois Huber, who shares a lab with Hans Peter Lang, highlights how the cantilever arrays have also become useful for identifying single gene mutations from biopsies. Recently introduced cancer drugs have particularly high efficacy for specific cancer genes, such as the HER2 gene for aggressive breast cancer and the BRAF mutation found in 50% of malignant melanoma incidents. “Before we treated cancers with general chemistry or radiation – everybody got the same treatment and either you were lucky or unlucky,” says Huber. “Here we can actually target the cancer directly – it goes towards personalized medicine so that you treat patients according to their genetic predisposition.”

Nanotechweb: Atomic force microscopy – 30 years on

No Compromises on AFM...

JILA's modified AFM probes measuring DNA molecules. The older mod (long cantilever, right) eliminated the usual gold coating to enhance long-term stability. The latest version (left) retains the gold coating where needed to reflect light but maintains excellent stability. Researchers also removed a large section to reduce stiffness and friction near surfaces. The new probe provides precise results much faster than before, while reducing “noise” (colored squiggles).
Credit: Baxley/JILA

JILA researchers have engineered a short, flexible, reusable probe for the atomic force microscope (AFM) that enables state-of-the-art precision and stability in picoscale force measurements. Shorter, softer and more agile than standard and recently enhanced AFM probes, the JILA tips will benefit nanotechnology and studies of folding and stretching in biomolecules such as proteins and DNA.

An AFM probe is a cantilever, shaped like a tiny diving board with a small, atomic-scale point on the free end. To measure forces at the molecular scale in a liquid, the probe attaches its tip to a molecule such as a protein and pulls; the resulting deflection of the cantilever is measured. The forces are in the realm of piconewtons, or trillionths of a newton. One newton is roughly the weight of a small apple.

The new probe design, described in ACS Nano,* is the JILA research group's third recent advance in AFM technology. JILA is jointly operated by the National Institute of Standards and Technology (NIST) and University of Colorado Boulder.

NIST:
No Compromises: JILA’s Short, Flexible, Reusable AFM Probe, Laura Ost

Atomic Friction...

A new experimental method based on atomic force microscopy allows the investigation of friction at the scale of individual atoms.

Everyone learns the basics of friction in high-school physics classes: the friction force experienced by a sliding object is proportional to the normal force that an object exerts on a surface. Remarkably, this extremely simple and empirical relation, known as Amontons’ Law, is still often used in creating the most technologically sophisticated machines and devices, even though friction is known to vary with a large number of other parameters not captured in this relation. For example, at the nanoscale, friction is significantly influenced by adhesion, an example where Amontons’ Law cannot predict the friction force [1]. Likewise, friction can depend on sliding speed, duration of contact, environment, temperature, and the sliding direction [1, 2]. As reported in Physical Review Letters, Jay Weymouth and colleagues at the University of Regensburg in Germany have investigated the friction force at atomic length scales, using an atomic force microscope (AFM) [3] to probe the forces between a tungsten tip coated with a small amount of silicon, sliding on the surface of crystalline silicon. They report an observation never before obtained at the scale of just a few atoms: friction is strongly dependent on the orientation of specific silicon atomic bonds at the surface with respect to the sliding direction of the tip.

A directional dependence of friction, also known as friction anisotropy, has been previously observed on larger scales (at least a few nanometers). For example, a tip was pulled along a molecular layer where the molecules were locally all tilted in the same direction. Sliding along the tilt axis produced lower friction than when sliding perpendicular to it [4]. A similar behavior can be observed in a simple way by pressing one’s hands together (as if in prayer but with the fingers spaced apart). Upon sliding the fingers of the left hand against the fingers of right hand (perpendicular to the long axis of your fingers), the fingers of one hand become stuck in between those of the other. However, if one instead slides the left hand down and the right hand up (parallel to the long axis of your fingers), the hands move smoothly. The relative orientation between the sliding direction and the grooves of one’s fingers influences friction because of the geometry of our hands. Friction anisotropy has been observed by sliding a small tip on atomically flat and well-characterized surfaces [5]. However, in all these cases, the nanometer-size tip was pressed into contact with the surface, meaning that a large number (at least thousands) of atoms were in contact during this experiment.

American Physical Society: Friction at the Atomic Scale