Qiangfei Xia of the Electrical and Computer Engineering (ECE) Department at the University of Massachusetts Amherst has been issued a five-year, $400,000 grant from the prestigious National Science Foundation (NSF) Faculty Early Career Development (CAREER) Program to develop emerging nanoelectronic devices. The title of his project is “CAREER: Scaling of Memristive Nanodevices and Arrays." Xia’s NSF research addresses the biggest obstacle for the continued operation of Moore’s Law, which states that the number of transistors on integrated circuits doubles approximately every two years. The law is named after Intel co-founder Gordon E. Moore, who first predicted the trend in his 1965 paper.

“It worked perfectly for more than 40 years, but now we’re reaching its fundamental limit, due to the quantum effects related to electron flow,” says Xia. “So we absolutely need new devices that can do a better job than transistors.”

The transistor is the fundamental building block of modern electronic devices and is ubiquitous in modern electronic systems. Following its development in the late 1940s, the transistor revolutionized the field of electronics and paved the way for smaller and cheaper radios, calculators, and computers, among many other things.

Xia’s memristive devices, or resistive switches, are two-terminal, passive, electronic devices that use high and low resistance states instead of charge storage to represent logic 1’s and 0’s. As a result, the device scalability is not limited by the quantum effect, which restricts transistors, but mainly dependent on how small the device can be made. Some of the beneficial characteristics of memristive devices are that they have fast switch speed, overwrite ability without erase, low power consumption, high endurance, and long data-retention time. They are promising for applications in non-volatile memory, non-volatile logic, reconfigurable circuits, and neuromorphic networks.

“Basically, the goals of my CAREER research will be to fabricate these new memristive nano-devices, test them, and understand them at a length scale that is yet to be achieved,” says Xia. “Ultimately, the research promises to advance transformative device technologies for the integrated circuit industry, sustaining U.S. competitiveness in high-technology areas.”

Xia explains that the limiting factor in these new memristive devices is how small we can make the nanowire electrodes and how densely we can pack them, which will mean using new technological processes. Xia’s research team will be scaling down memristive nanodevices using a new set of lithographic technologies: nanoimprint lithography, electron beam lithography, directed self-assembly of block copolymers, and the combination of these next-generation nanolithography technologies.

Xia’s team has already made a working array of memristive devices that are smaller than 10 nanometers, and he is confident that 3 nanometers is approachable, although very challenging.

The CAREER Program offers the NSF's most prestigious awards in support of junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education, and the integration of education and research. As such, the educational aspects are also very important. Xia is a dedicated and creative instructor in the classroom. He was a nominee for the Distinguished Teaching Award, a campus-wide highest honor to recognize exemplary teaching at UMass Amherst, in the first year of his teaching career.

In his CAREER project, Xia has developed a senior-level ECE course in semiconductors and nanotechnology, in which students actually construct computer chips in a “clean room.” Another educational initiative is Xia’s “Art in Nanoengineering” exhibit, which opened last February at Smith College and will be moved to the 1350 Gallery in Springfield to educate K-12 students there. One example is a dust particle half the size of a human hair that looks uncannily like an “Easter Bonnet,” which is the title of this photo in the exhibit. A third enterprise is coursework Xia will present in the Nanotechnology Summer Institute at UMass Amherst for K-12 teachers.

In addition to the NSF CAREER, Xia has also received a DARPA Young Faculty Award for studying all-silicon-based resistive random access memories and is a co-PI on an AFOSR MURI project for building hybrid integrated circuits for advanced information processing. (January 2013)