Growing The Thinnest Of Semiconductors

For supermodels and semiconductors, it seems that thin is always in. As electronics makers continue to squeeze more components into increasingly smaller spaces, they’re on the lookout for materials that can achieve the ultimate in small—atomic-scale electronic devices. Now, Jiwoong Park and colleagues at Cornell University report an advance toward realizing such materials. They’ve grown sheets of the transition-metal dichalcogenides MoS₂ and WS₂ that are only three atoms thick, but stretch over an area of about 10 sq in (Nature 2015, DOI: 10.1038/nature14417). Park’s team made the monolayer sheets via a new metal-organic chemical vapor deposition process, using Mo(CO)₆ or W(CO)₆ as the transition-metal source and diethylsulfide as the sulfur source. They added hydrogen gas to remove any built-up carbonaceous deposits. The resulting films were of sufficient quality to make field-effect transistors. The method does have some limitations: It takes about 26 hours and requires temperatures of 550 °C. Even so, Park and coworkers note that the technique is “a step toward the realization of atomically thin integrated circuitry” and could find use in the fabrication of flexible electronics, photovoltaics, and displays.