A scanning probe microscope

Researchers from Russia developed a new technique of nanolithography for carbon-based materials, involving anodic oxidation by means of a probe of an atomic force microscope.

Probe techniques, which use atomic sharp needles (probes) for exploring various surfaces, are under close attention these days. In nano-world these probes are like fingers, touching various objects. Modern hardware provides highly accurate detection of barely noticeable movements of a probe along the surface, which well correspond to relief of atomic structures. This is how fascinating images of nano-world are born. A star on graphite surface has petals, which are only 5 carbon atoms thick.

Probe microscopy’s extremely high resolution is achieved by very small space for interaction between atoms of the probe’s tip and on the object’s surface. Diffraction limit, essential for optical microscopy, is not a problem here.

Scanning can be performed in various environments – air and even liquid ones. Many cases do not require expensive vacuum devices, like electron or ion microscopy does. Probe microscopes are usually quite small and easily integrated with other devices, if necessary. All abovementioned properties provide a user of a probe microscope with additional features. For instance, molecules coming from environment can be forced to react with surface atoms. For this purpose voltage is applied between a probe and object’s surface – the surface gets positively charged, and a mechanism of local anodic oxidation is realized. As a result of electrochemical reaction surface atoms get oxidized with oxide formation.

When anodic oxidation is performed on a carbon-based material, the probe forms cavities, because carbon oxides (mono- and dioxide) are gases. The original idea was that carbon atoms react with oxygen from the air, however further experiment demonstrated that water, which condensed on the surface from the air, was the primary oxidizer in this case.

Researchers recently found out that graphite oxidation results both in cavities and in mounts, which was explained by formation of graphite oxide. Graphite oxide is known to have the same stratified structure as graphite, but layers of carbon atoms get deformed due to newly formed bonds with oxygen-containing chemical groups. Water molecules also insert themselves into space between layers, which finally ends in formation of mounts. Graphite oxide is a dielectric material, and that is why local oxidation of its surface can lead to formation of various nanostructures with possible applications in electronics, in construction of chemical and biological sensors, and plates for experiments with single living cells. The technique allows creating nanostructures with resolution of not more than 10 nanometers within several minutes.

A unique technique conquered hearts of both scientists and ordinary people keen on beautiful things. Artists frequently use new technologies for implementation of their creative ideas. It turns out that a piece of graphite with 1x1 cm size can provide unrestricted space for creativity with over 100 000 000 tiny pictures, which can be drawn on it.

Source: Science & Technologies