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Researchers Create Scalable Building Blocks for Ultrathin Nanoscale Electronics

Researchers Create Scalable Building Blocks for Ultrathin Nanoscale Electronics

by Giulio PriscoJuly 22, 2015

Researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL) have created arrays of semiconductor junctions – the building blocks of electronics – in arbitrary patterns within a single, nanometer-thick semiconductor crystal.

The research is published in Nature Communications with the title “Patterned Arrays of Lateral Heterojunctions within Monolayer Two-Dimensional Semiconductors.” The paper is freely available online.

“The formation of semiconductor heterojunctions and their high-density integration are foundations of modern electronics and optoelectronics,” state the researchers. “This demonstration of lateral heterojunction arrays within a monolayer crystal is an essential step for the integration of two-dimensional semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin devices.”

Next-generation ultrathin devices for applications ranging from flexible consumer electronics to solar energy

Ultrathin junctionsToday’s technology permits building very small – 10-nanometer – transistors from three-dimensional (3D) crystals . But the ORNL scientists, in a research step that could open the way to future development in electronics, have used two-dimensional (2D) crystals to build ultrathin transistors by lithographically patterning junctions between two different semiconductors within a single nanometer-thick layer.

In the process, the researched transformed selected regions of a single-layer crystal (molybdenum diselenide) into another crystal (molybdenum disulfide) by pulsed laser deposition of sulfur atoms that replaced the original selenium atoms, thus creating a viable junction between different semiconductors. The image shows how the sulfur atoms (green) replaced the selenium atoms (red) in lithographically exposed regions (top) as shown by Raman spectroscopic mapping (bottom).

“We chose pulsed laser deposition of sulfur because of the digital control it gives you over the flux of the material that comes to the surface,” said study co-leader Masoud Mahjouri-Samani. “You can basically make any kind of intermediate alloy. You can just replace, say, 20 percent of the selenium with sulfur, or 30 percent, or 50 percent.”

“The development of a scalable, easily implemented process to lithographically pattern and easily form lateral semiconducting heterojunctions within two-dimensional crystals fulfills a critical need for ‘building blocks’ to enable next-generation ultrathin devices for applications ranging from flexible consumer electronics to solar energy,” said study co-leader David Geohegan, head of ORNL’s Nanomaterials Synthesis and Functional Assembly Group at the Center for Nanophase Materials Sciences. Mahjouri-Samani added that millions of 2D building blocks with numerous patterns may be made concurrently.

We can literally make any kind of pattern that we want.

The researchers plan to study if their pulsed laser vaporization and conversion method will work with atoms other than sulfur and selenium.

Images from Oak Ridge National Laboratory and Wikimedia Commons.

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