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Research: Layered 2D nanocrystals to replace CMOS

Posted: 17 Apr 2013 ?? ?Print Version ?Bookmark and Share

Keywords:CMOS? 2D nanocrystal? molybdenum disulfide? transistor?

A team of researchers at Purdue Birck Nanotechnology Centre is developing a type of semiconductor technology for future electronics based on "2D nanocrystals" layered in sheets less than 1nm thick. Seen as a probable replacement for today's transistors, the layered structure is made up of a material called molybdenum disulfide, which belongs to a new class of semiconductors. Metal dichalogenides are emerging as potential candidates to replace today's technology, complementary metal oxide semiconductors, or CMOS, the researchers noted.

New technologies will be needed to allow the semiconductor industry to continue advances in computer performance driven by the ability to create ever-smaller transistors. It is becoming increasingly difficult, however, to continue shrinking electronic devices made of conventional silicon-based semiconductors.

"We are going to reach the fundamental limits of silicon-based CMOS technology very soon, and that means novel materials must be found in order to continue scaling," said Saptarshi Das, who has completed a doctoral degree, working with Joerg Appenzeller, a professor of electrical and computer engineering and scientific director of nanoelectronics at Purdue's Birck Nanotechnology Center. "I don't think silicon can be replaced by a single material, but probably different materials will co-exist in a hybrid technology."

The nanocrystals are called 2D because the materials can exist in the form of extremely thin sheets with a thickness of 0.7nm, or roughly the width of three or four atoms. Findings show that the material performs best when formed into sheets of about 15 layers with a total thickness of 8-12nm. The researchers also have developed a model to explain these experimental observations.

Layered 2D nanocrystals

The material is layered in sheets less than a nanometer thick that could replace today's silicon transistors. Source: Birck Nanotechnology Center, Purdue University.

Molybdenum disulfide is promising in part because it possesses a bandgap, a trait that is needed to switch on and off, which is critical for digital transistors to store information in binary code.

Analysing the material or integrating it into a circuit requires a metal contact. However, one factor limiting the ability to measure the electrical properties of a semiconductor is the electrical resistance in the contact. The researchers eliminated this contact resistance using a metal called scandium, allowing them to determine the true electronic properties of the layered device. Their results have been published in the January issue of the journal Nano Letters with doctoral students Hong-Yan Chen and Ashish Verma Penumatcha as the other co-authors.

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