Russian physicists from several scientific institutions successfully synthesized regular one-dimensional nanostructures, which period didn’t exceed 90 nanometres. For this purpose, researchers treated solid surfaces with multipulse femtosecond laser radiation in air or water environment.

Extremely short pulses of femtosecond laser result (in case of external focusing) in high-intensity local effects of light on matter. Conventionally speaking, femtosecond laser impulse acts like laser sword of Luke Skywalker in extremely short time intervals. The result is simple and evident – matter of solid target evaporates, and the target slowly deteriorates. This process is known as “laser”ablation. However, if exposure times are extremely short, a target is damaged very moderately, and deterioration process can be constructive.

Scientific group consists of research fellows from Physics Institute of Russian Academy of Science, Moscow State University, Belgorod State University and Institute of General Physics of Russian Academy of Science.

Researchers admit that the smallest regular nanostructures can be created by means of molecular-atomic assembly, however, this process takes significant time, and resulting nanostructures cover very small areas. Femtosecond lasers require hours, sometimes even minutes, to create a millimeter-sized nanostructural region on surface of a solid material for further research by physical and chemical techniques. Russian physicists successfully created regular one-dimensional nanostructures with period less than 100 micrometers in water environment – for the first time in the world. In that experiment wavelength of laser radiation was 8 times longer than the period of resulting nanostructures.

 

 

Scientists now can create regular nano-structures on titanium, silicon and aluminum. These materials are carefully studied in order to find some general patterns of nanostructures formation. Titanium appeared to have the most interesting mechanism of nanostructure formation – the denser energy of femtosecond laser radiation is, the smaller nanostructures form on metal surface. This effect is even more interesting, since usual tendency is exactly the opposite of what is observed on titanium’s surface. What usually happens is that if you want to get small nanostructures, you have to decrease surface energy density. Intensity of mass transfer slows down, thus requiring laser radiation exposure to increase, which means appreciation of the whole process, but not for titanium.

The fact of reducing period of nanostructures, which form on dry surface of titanium (wet titanium surface gives even smaller regular nanostructures) under conditions of increasing energy density of femtosecond laser radiation, is extremely valuable for further studies. Titanium is one of basic materials for aerospace technologies and medical industry, implants, for instance, and nano-modifications of its surface can not only change its existing and well-known properties, but also add some new unusual properties to this material.

Source: Physics Institute of Russian Academy of Science

Kizilova Anna