(麻豆淫院)鈥擬icrochips are per颅va颅sive in today's high-鈥嬧€媡ech society, playing inte颅gral roles in the inner work颅ings of your cell phone to your Keurig coffee machine.

A pro颅cessing tech颅nology called CMOS, or com颅ple颅men颅tary metal鈥搊xide鈥搒emiconductor, made microchips eco颅nom颅i颅cally fea颅sible in the 1980s, said Siva颅sub颅ra颅manian Somu, a research sci颅en颅tist in Northeastern's Center for High-鈥嬧€媟ate Nanoman颅u颅fac颅turing.

A crit颅ical ele颅ment in any microchip is some颅thing called an inverter鈥攁n elec颅tronic com颅po颅nent that spits out zeros when you give it ones, and vice versa. "A tran颅sistor [the basic ele颅ment in an inverter] is a simple, extremely fast switch," Somu explained. "You can turn it on and off by elec颅tric signals."

In the early days of com颅puter tech颅nology, mechan颅ical switches were used for com颅pu颅ta颅tional oper颅a颅tions. "You cannot achieve fast com颅pu颅ta颅tions using mechan颅ical switches," Somu said. So CMOS, which used elec颅tric sig颅nals to turn the switches on and off, rep颅re颅sented a sig颅nif颅i颅cant advance in the field.

But despite its rel颅a颅tive economy, a CMOS fab颅ri颅ca颅tion plant still costs about $50 bil颅lion, according to Somu. "We needed an alter颅na颅tive, cost-鈥嬧€媏ffective solu颅tion that still can com颅pete with CMOS at the foundry level," he said.

CHN's pro颅pri颅etary "directed-鈥嬧€媋ssembly" approach is that alter颅na颅tive solu颅tion. Instead of requiring sev颅eral fab颅ri颅ca颅tion steps of adding and removing mate颅rial, as in the case of CMOS, directed assembly is an additive-鈥嬧€媜nly process that can be done at room tem颅per颅a颅ture and pres颅sure. A fab颅ri颅ca颅tion facility based on this tech颅nology, Somu said, could be built for as little as $25 million.

This cost sav颅ings would make nan颅otech颅nology acces颅sible to mil颅lions of new inno颅va颅tors and entre颅pre颅neurs, unleashing a wave of cre颅ativity the same way the PC did for com颅puting, said Ahmed Bus颅naina, the William Lin颅coln Smith Pro颅fessor and Director of the NSF Center for High-鈥嬧€媟ate Nanomanufacturing.

But cre颅ating a nano颅sized inverter is easier said than done, added Jun Huang, a post颅doc颅toral research sci颅en颅tist in the center. Researchers have using mate颅rials like graphene and carbon nan颅otubes for cre颅ating inverters, but none of these has worked well on its own. Cre颅ating a nano颅sized inverter made up of dif颅ferent nano颅ma颅te颅rials with excel颅lent prop颅er颅ties, Huang said, can result in excel颅lent com颅pli颅men颅tary transistors.

Using the directed-鈥嬧€媋ssembly process, the team cre颅ated an effec颅tive com颅pli颅men颅tary inverter using Molyb颅denum disul颅fide and carbon nan颅otubes. "At the nanolevel," said Huang, "molyb颅denum disul颅fide occurs in thin, nanometer-鈥嬧€媡hick sheets." At this scale, he noted, the mate颅rial begins to demon颅strate tran颅sistor char颅ac颅ter颅is颅tics crit颅ical to the con颅struc颅tion of a good inverter.

The suc颅cess rep颅re颅sents a step toward CHN's ulti颅mate goal of enabling small鈥� and medium-鈥嬧€媠ized busi颅nesses to develop new, microchip-鈥嬧€媌ased tech颅nolo颅gies. The results of their research were reported in a recent article in the journal Nanotechnology.