MOSCOW, December 2. /TASS/. Researchers from Skoltech, Aalto University, and Peter the Great St. Petersburg Polytechnic University have successfully demonstrated the technique of coating zinc oxide on the surface of single-walled carbon nanotubes, the SPbPU’s press-service said. Based on the new material, ambipolar field transistors have been maintained which may find their applications in logic circuits and memory cells.

Single-walled carbon nanotubes (SWCNTs) represent cylindrical structures (with a diameter of several nanometers and length of several microns) built exclusively of carbon atoms. SWCNTs show unique mechanical, electrical, and optical properties that make them very attractive in various practical applications, including the design of composite materials, supercapacitors, bio-and chemical sensors, as well as transistors.

However, for many other applications, the surface of SWCNTs should be modified with chemical substances.

"Here, we combined SWCNTs treated with ozone and zinc oxide (ZnO) to tune electrical properties of transistors", said a co-author of the study, Albert Nasibulin, a professor at Skoltech.

How was the new material created?

In this study, researchers have initially treated the SWCNTs with a nitrogen technique developed in the Laboratory of Nanomaterials at Skoltech, followed by spraying ZnO on the surface of the carbon nanotubes by means of atomic layer deposition (ALD) yielding SWCNTs uniformly coated with ZnO.

Later, the zinc oxide coated nanotubes were treated with ultraviolet which led to the improvement of their hydrophilic behavior. The nanotubes’ hydrophobicity prevents it from being used in medicine and pharmacology for making various solutions, so their functionalization - making them hydrophilic - solves this issue.

Transistors based the on new material

With the use of thin SWCNT films coated with ZnO, the researchers have made ambipolar transistors (with charge carriers "holes" and electrons) from p-type field-effect transistors (with "holes" as charge carriers).

"Unlike p-type transistors obtained under ambient conditions, our transistors prepared by ALD coating gain ambipolar fraction of about 90%," - commented Nasibulin. - "This unique ambipolar behavior makes our material very promising for the manufacture of semiconductor devices. The demonstrated ambipolar transistors can be applied for creating new logic circuits and memory cells.

The results of the study were published in Nanotechnology.