A team at the University of California, Riverside Bourns College of Engineering has developed a novel way to build what many see as the next generation memory storage devices for portable electronic devices including smart phones, tablets, laptops and digital cameras.

The device is based on the principles of resistive memory, which can be used to create memory cells that are smaller, operate at a higher speed and offer more storage capacity than flash memory cells, the current industry standard. Terabytes, not gigbytes, will be the norm with resistive memory.

Read more: Crossbar unveils resistive RAM with simple, three-layer structure

The key advancement in the UC Riverside research is the creation of a zinc oxide nano-island on silicon. It eliminates the need for a second element called a selector device, which is often a diode.

"This is a significant step as the electronics industry is considering wide-scale adoption of resistive memory as an alternative for flash memory," said Jianlin Liu, a professor of electrical engineering at UC Riverside who is one of the authors of the paper. "It really simplifies the process and lowers the fabrication cost."

This is a series of images that shows the zinc oxide nano-island on silicon and the three modes of the operation.

The findings were published online this week in the journal Scientific Reports, which is part of Nature Publishing Group. The paper is called "Multimode Resistive Switching in Single ZnO Nanoisland System."

Liu’s co-authors were: Jing Qi, a former visiting scholar in Liu’s lab and now an associate professor at Lanzhou University in China; Mario Olmedo, who earned his Ph.D. from UC Riverside and now works at Intel; and Jian-Guo Zheng, a director of the Laboratory of Electron and X-ray Instrumentation at UC Irvine.

Flash memory has been the standard in the electronics industry for decades. But, as flash continues to get smaller and users want higher storage capacity, it appears to reaching the end of its lifespan, Liu said.

With that in mind, resistive memory is receiving significant attention from academia and the electronics industry because it has a simple structure, high-density integration, fast operation and long endurance.

Researchers have also found that resistive memory can be scaled down in the sub 10-nanometer scale. Current flash memory devices are roughly using a feature size twice as large.

Resistive memory usually has a metal-oxide-metal structure in connection with a selector device. The UC Riverside team has demonstrated a novel alternative way by forming self-assembled zinc oxide nano-islands on silicon. Using a conductive atomic force microscope, the researchers observed three operation modes from the same device structure, essentially eliminating the need for a separate selector device.

Memory devices like disk drives, flash drives and RAM play an important role in our lives. They are an essential component of our computers, phones, electronic appliances and cars. Yet current memory devices have significant drawbacks: dynamic RAM memory has to be refreshed periodically, static RAM data is lost when the power is off, flash memory lacks speed, and all existing memory technologies are challenged when it comes to miniaturization.

Increasingly, memory devices are a bottleneck limiting performance. In order to achieve a substantial improvement in computation speed, scientists are racing to develop smaller and denser memory devices that operate with high speed and low power consumption.

Prof. Yossi Paltiel and research student Oren Ben-Dor at the Hebrew University of Jerusalem’s Harvey M. Krueger Family Center for Nanoscience and Nanotechnology, together with researchers from the Weizmann Institute of Science, have developed a simple magnetization progress that, by eliminating the need for permanent magnets in memory devices, opens the door to many technological applications.

Published in Nature Communications, the research paper, A chiral-based magnetic memory device without a permanent magnet, was written by Prof. Yossi Paltiel, Oren Ben Dor and Shira Yochelis at the Department of Applied Physics, Harvey M. Krueger Family Center for Nanoscience and Nanotechnology, Hebrew University of Jerusalem; and Shinto P. Mathew and Ron Naaman at the Department of Chemical Physics, Weizmann Institute of Science.

The research deals with the flow properties of electron charge carriers in memory devices. According to quantum mechanics, in addition to their electrical charge, electrons also have a degree of internal freedom called spin, which gives them their magnetic properties. The new technique, called magnetless spin memory (MSM), drives a current through chiral material (a kind of abundantly available organic molecule) and selectively transfers electrons to magnetize nano magnetic layers or nano particles. With this technique, the researchers showed it is possible to create a magnetic-based memory device that does not require a permanent magnet, and which could allow for the miniaturization of memory bits down to a single nanoparticle.

The potential benefits of magnetless spin memory are many. The technology has the potential to overcome the limitations of other magnetic-based memory technologies, and could make it possible to create inexpensive, high-density universal memory-on-chip devices that require much less power than existing technologies. Compatible with integrated circuit manufacturing techniques, it could allow for inexpensive, high-density universal memory-on-chip production.

According to the Hebrew University’s Prof. Paltiel, “Now that proof-of-concept devices have been designed and tested, magnetless spin memory has the potential to become the basis of a whole new generation of faster, smaller and less expensive memory technologies.”

The technology transfer companies of the Hebrew University (Yissum) and the Weizmann Institute of Science (Yeda) are working to promote the realization of this technology, by licensing its use and raising funds for further development and commercialization. With many possible applications, it has already attracted the attention of start-up funds.

The Hebrew University’s Center of Nanoscience and Nanotechnology helped with device fabrication and advice. Prof. Paltiel acknowledges the Yessumit internal grant from the Hebrew University, and Ron Naaman and Shinto P. Mathew acknowledge the support of the Minerva Foundation.

Established in 2001, the Center for Nanoscience and Nanotechnology deals with diverse fields of nanoscience such as new materials, molecular and nano-electronics, nano-electrooptics, nanomedicine and nano-biology. The research will enable technological development of new transistors, memory elements, sensors and biosensors, renewable energy sources, directed drug delivery schemes, and more. Operating within the Faculty of Science, the Center aims to create an enabling environment for interdisciplinary research, education, technological development and commercialization of scientific achievements in the field of Nanoscience and Nanotechnology, in order to participate as a leading force in the world nanotechnology revolution and contribute to Israeli academia, industry and society. The Center has almost 70 member groups and is expected to expand further through recruitment of promising young faculty members.