SINCE its invention in the early 1980s by Binnig and Rohrer1,2, the scanning tunnelling microscope (STM) has provided images of surfaces and adsorbed atoms and molecules with unprecedented resolution The STM has also been used to modify surfaces, for example by locally pinning molecules to a surface3 and by transfer of an atom from the STM tip to the surface4 Here we report the use of the STM at low temperatures (4 K) to position individual xenon atoms on a single-crystal nickel surface with atomic pre-cision This capacity has allowed us to fabricate rudimentary structures of our own design, atom by atom The processes we describe are in principle applicable to molecules also In view of the device-like characteristics reported for single atoms on surfaces5,6, the possibilities for perhaps the ultimate in device miniaturization are evident

Positioning single atoms with a scanning tunnelling microscope

Nanochemistry: Synthesis in diminishing dimensions

The atomic force microscope (AFM) can be used to image the surface of both conductors and nonconductors even if they are covered with water or aqueous solutions. An AFM was used that combines microfabricated cantilevers with a previously described optical lever system to monitor deflection. Images of mica demonstrate that atomic resolution is possible on rigid materials, thus opening the possibility of atomic-scale corrosion experiments on nonconductors. Images of polyalanine, an amino acid polymer, show the potential of the AFM for revealing the structure of molecules important in biology and medicine. Finally, a series of ten images of the polymerization of fibrin, the basic component of blood clots, illustrate the potential of the AFM for revealing subtle details of biological processes as they occur in real time.

https://science.sciencemag.org/content/sci/243/4898/1586.full.pdf

Imaging crystals, polymers, and processes in water with the atomic force microscope.

As their name indicates, liquid crystals simultaneously exhibit some characteristics common to both ordinary isotropic liquids and solid crystals. This ambivalence is also found in the effects of surfaces on these systems which lead to a great diversity of phenomena. These phenomena are reviewed focusing on nematic liquid crystals which have the simplest structure among the many existing types and which have been the most extensively studied. Three main kinds of effects can be distinguished. The first concerns the perturbation of the liquid crystalline structure close to the surface. Beyond this transition region, the bulk liquid crystalline structure is recovered with an orientation which is fixed by the surface: this phenomenon of orientation of liquid crystals by surfaces is the so-called anchoring. Finally, close to bulk phase transitions, critical adsorption or wetting can occur at surfaces as is also seen in isotropic systems.

https://iopscience.iop.org/article/10.1088/0034-4885/54/3/002/pdf

Surface effects and anchoring in liquid crystals

Two-dimensional molecular patterns were obtained by the adsorption of long-chain alkanes, alcohols, fatty acids, and a dialkylbenzene from organic solutions onto the basal plane of graphite. In situ scanning tunneling microscopy (STM) studies revealed that these molecules organize in lamellae with the extended alkyl chains oriented parallel to a lattice axis within the basal plane of graphite. The planes of the carbon skeletons, however, can be oriented either predominantly perpendicular to or predominantly parallel with the substrate surface, causing the lamellar lattice to be either in or near registry with the substrate (alkanes and alcohols) or not in registry (fatty acids and dialkylbenzenes). In the case of the alcohols and the dialkylbenzene the molecular axes are tilted by +30 degrees or -30 degrees with respect to an axis normal to the lamella boundaries, giving rise to molecularly well-defined domain boundaries. Fast STM image recording allowed the spontaneous switch between the two tilt angles to be observed in the alcohol monolayers on a time scale of a few milliseconds.

https://science.sciencemag.org/content/sci/253/5018/424.full.pdf

Commensurability and mobility in two-dimensional molecular patterns on graphite.

THE scanning tunnelling microscope (STM) is now an established tool for the study of ordered metal and semiconductor surfaces on an atomic scale1,2. Here we demonstrate the ability of the STM to image a large class of organic molecular adsorbates with almost atomic resolution3. From the images it is apparent that not only is the STM resolving the individual molecules, but it is also distinguishing between the different functional groups within the molecules. We propose that the contrast mechanism responsible for the well resolved images is modulation of the local work function of the substrate by the polarizable molecular adsorbates.

Contrast mechanism for resolving organic molecules with tunnelling microscopy

In a very short time the scanning tunnelling microscope has become an important tool in surface science, and physics in general. Its primary use has been to obtain atomic-resolution images of surfaces, but recently, efforts have been made to use it to manipulate materials as well as image them. One may now reasonably ask if it is possible to move and alter matter predictably on an atomic scale. Here we report the accomplishment of the smallest yet, purposeful, spatially localized changes in matter, effected on a graphite surface. We believe that the changes result from the pinning of individual organic molecules to the graphite. The reverse manipulation, the removal of pinned molecules, has also been demonstrated. Finally, we have evidence that we can remove a portion of a pinned molecule, effectively performing transformations on single molecules using the tunnelling microscope.

Molecular manipulation using a tunnelling microscope

A micromechanical particle sorting system uses a removable/disposable apparatus which may include a compressible device, a filter apparatus and a cell sorter chip assembly. The chip assembly may include a tubing strain relief manifold and a microfabricated cell sorting chip. The chip assembly may be detachable from the filter apparatus in order to mount the MEMS particle sorting chip adjacent to a force- generating apparatus which resides with the particle sorting system. A disturbance device installed in the particle sorting system may interact with a transducer on the removable/disposable apparatus to reduce clogging of the flow through the system. Using this removable/disposable apparatus, when the sample is changed, the entire apparatus can be thrown away with minimal expense and system down time.

Removable/disposable apparatus for mems particle sorting device

A data recording disk drive has an improved head-disk interface provided by a transducer carrier which is essentially a low-flying air-bearing slider that is also able to be in contact and near contact with the lubricant film on the disk. The slider has a front air-bearing surface in the form of a pair of equally-spaced air-bearing pads, a rear air-bearing pad, and a central nonair-bearing recessed surface which separates the front and rear air-bearing pads. The two front pads have a surface area greater than that of the rear pad and thus provide a positive pitch up of the slider. This causes the rear pad to also be pitched up so that air can flow beneath the rear pad to generate an air bearing in the rear portion of the slider. The presence of the central nonair-bearing region eliminates any lift in the central part of the slider, which allows for the low-flying height. The flying height of the rear pad of the slider above the disk is controlled by the width of the rear air-bearing pad. The rear pad has its leading edge wider than its trailing edge so that it is able to withstand contact with the lubricant film on the disk, typically at the lower disk velocities near the disk inside diameter, without generating unacceptable drag forces or depleting the lubricant from the disk. The rear pad also has a skewed leading edge which compensates for skew of the slider to minimize the flying height variation from the disk inside diameter to outside diameter.

Slider with transverse ridge sections supporting air-bearing pads and disk drive incorporating the slider

A disk file with substantially reduced head-disk spacing and corresponding improvement in recording performance uses a disk coated with a film of conventional high viscosity lubricant, a lubricant reservoir for replenishing the lubricant on the disk over the life of the file, and a transducer carrier with feet which ski on the high viscosity liquid film. The file does not include any means for recirculating the lubricant since the lubricant spins off the disk at a relatively low rate due to its high viscosity. The lubricant reservoir contains a very small amount of lubricant and thus may be maintained inside the substantially sealed disk file. In one embodiment of the invention, the sealed disk file is essentially evacuated. The operation of the disk file in a near vacuum environment is possible because, unlike conventional disk files, air is not required to support an air-bearing head-disk interface and the high vapor pressure of the relatively high molecular weight lubricant prevents its evaporation.

John S. Foster

Papers

Contrast mechanism for resolving organic molecules with tunnelling microscopy

Molecular manipulation using a tunnelling microscope

Removable/disposable apparatus for mems particle sorting device

Slider with transverse ridge sections supporting air-bearing pads and disk drive incorporating the slider

Disk file with liquid film head-disk interface