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A new, high-pressure technique may allow the production of huge sheets of thin-film silicon semiconductors at low temperatures in simple reactors at a fraction of the size and cost of current technology. A paper describing the research by scientists at Penn State University publishes on May 13, 2016, in the journal Advanced Materials.

“We have developed a new, high-pressure, plasma-free approach to creating large-area, thin-film semiconductors,” said John Badding, professor of chemistry, physics, and materials science and engineering at Penn State and the leader of the research team. “By putting the process under high pressure, our new technique could make it less expensive and easier to create the large, flexible semiconductors that are used in flat-panel monitors and solar cells and are the second most commercially important semiconductors.”

Thin-film silicon semiconductors typically are made by the process of chemical vapor deposition, in which silane — a gas composed of silicon and hydrogen — undergoes a chemical reaction to deposit the silicon and hydrogen atoms in a thin layer to coat a surface. To create a functioning semiconductor, the chemical reaction that deposits the silicon onto the surface must happen at a low enough temperature so that the hydrogen atoms are incorporated into the coating rather than being driven off like steam from boiling water. With current technology, this low temperature is achieved by creating plasma — a state of matter similar to a gas made up of ions and free electrons — in a large volume of gas at low pressure. Massive and expensive reactors so large that they are difficult to ship by air are needed to generate the plasma and to accommodate the large volume of gas required.

“With our new high-pressure chemistry technique, we can create low-temperature reactions in much smaller spaces and with a much smaller volume of gas,” said Badding. “The reduced space necessary allows us, for the first time, to create semiconductors on multiple, stacked surfaces simultaneously, rather than on just a single surface. To maximize the surface area, rolled-up flexible surfaces can be used in a very simple and far more compact reactor. The area of the resulting rolled-up semiconducting material could, upon further development, approach or even exceed a square kilometer.”

The future of movies and manufacturing may be in 3-D, but electronics and photonics are going 2-D; specifically, two-dimensional semiconducting materials.

One of the latest advancements in these fields centers on molybdenum disulfide (MoS2), a two-dimensional semiconductor that, while commonly used in lubricants and steel alloys, is still being explored in optoelectronics.

Recently, engineers placed a single layer of MoS2 molecules on top of a photonic structure called an optical nanocavity made of aluminum oxide and aluminum. (A nanocavity is an arrangement of mirrors that allows beams of light to circulate in closed paths. These cavities help us build things like lasers and optical fibers used for communications.)

The results, described in the paper “MoS2 monolayers on nanocavities: enhancement in light-matter interaction” published in April by the journal 2D Materials, are promising. The MoS2 nanocavity can increase the amount of light that ultrathin semiconducting materials absorb. In turn, this could help industry to continue manufacturing more powerful, efficient and flexible electronic devices.

“The nanocavity we have developed has many potential applications,” says Qiaoqiang Gan, PhD, assistant professor of electrical engineering in the University at Buffalo’s School of Engineering and Applied Sciences. “It could potentially be used to create more efficient and flexible solar panels, and faster photodetectors for video cameras and other devices. It may even be used to produce hydrogen fuel through water splitting more efficiently.”

A single layer of MoS2 is advantageous because unlike another promising two-dimensional material, graphene, its bandgap structure is similar to semiconductors used in LEDs, lasers and solar cells.

“In experiments, the nanocavity was able to absorb nearly 70 percent of the laser we projected on it. Its ability to absorb light and convert that light into available energy could ultimately help industry continue to more energy-efficient electronic devices,” said Haomin Song, a PhD candidate in Gan’s lab and a co-lead researcher on the paper.

Industry has kept pace with the demand for smaller, thinner and more powerful optoelectronic devices, in part, by shrinking the size of the semiconductors used in these devices.

A problem for energy-harvesting optoelectronic devices, however, is that these ultrathin semiconductors do not absorb light as well as conventional bulk semiconductors. Therefore, there is an intrinsic tradeoff between the ultrathin semiconductors’ optical absorption capacity and their thickness.

The nanocavity, described above, is a potential solution to this issue.

A team led by researchers from the National University of Singapore (NUS) has developed a method to enhance the photoluminescence efficiency of tungsten diselenide, a two-dimensional semiconductor, paving the way for the application of such semiconductors in advanced optoelectronic and photonic devices.

Tungsten diselenide is a single-molecule-thick semiconductor that is part of an emerging class of materials called transition metal dichalcogenides (TMDCs), which have the ability to convert light to electricity and vice versa, making them strong potential candidates for optoelectronic devices such as thin film solar cells, photodetectors flexible logic circuits and sensors. However, its atomically thin structure reduces its absorption and photoluminescence properties, thereby limiting its practical applications.

By incorporating monolayers of tungsten diselenide onto gold substrates with nanosized trenches, the research team, led by Professor Andrew Wee of the Department of Physics at the NUS Faculty of Science, successfully enhanced the nanomaterial’s photoluminescence by up to 20,000-fold. This technological breakthrough creates new opportunities of applying tungsten diselenide as a novel semiconductor material for advanced applications.

Ms Wang Zhuo, a PhD candidate from the NUS Graduate School for Integrative Sciences and Engineering (NGS) and first author of the paper, explained, “This is the first work to demonstrate the use of gold plasmonic nanostructures to improve the photoluminescence of tungsten diselenide, and we have managed to achieve an unprecedented enhancement of the light absorption and emission efficiency of this nanomaterial.”

Elaborating on the significance of the novel method, Prof Wee said, “The key to this work is the design of the gold plasmonic nanoarray templates. In our system, the resonances can be tuned to be matched with the pump laser wavelength by varying the pitch of the structures. This is critical for plasmon coupling with light to achieve optimal field confinement.”

The novel research was first published online in the journal Nature Communications on 6 May 2016.

Best of both worlds


May 9, 2016

More, faster, better, cheaper. These are the demands of our device-happy and data-centered world. Meeting these demands requires technologies for processing and storing information. Now, a significant obstacle to the development of next-generation device technologies appears to have been overcome, according to researchers from the University of Tokyo (Japan), Tokyo Institute of Technology (Japan) and Ho Chi Minh University of Pedagogy (Vietnam).

Specializing in the emerging field of semiconductor spintronics, the team has become the first to report growing iron-doped ferromagnetic semiconductors working at room temperature — a longstanding physical constraint. Doping is the practice of adding atoms of impurities to a semiconductor lattice to modify electrical structure and properties. Ferromagnetic semiconductors are valued for their potential to enhance device functionality by utilizing the spin degrees of freedom of electrons in semiconductor devices.

“Bridging semiconductor and magnetism is desirable because it would provide new opportunities of utilizing spin degrees of freedom in semiconductor devices,” explained research leader Masaaki Tanaka, Ph.D., of the Department of Electrical Engineering & Information Systems, and Center for Spintronics Research Network, University of Tokyo. “Our approach is, in fact, against the traditional views of material design for ferromagnetic semiconductors. In our work, we have made a breakthrough by growing an iron-doped semiconductor which shows ferromagnetism up to room temperature for the first time in semiconductors that have good compatibility with modern electronics. Our results open a way to realize semiconductor spintronic devices operating at room temperature.”

The researchers discuss their findings this week in Applied Physics Letters, from AIP Publishing. The researchers’ maverick move challenged the prevailing theory that predicted a type of semiconductor known as “wide band gap” would be strongly ferromagnetic. Most research focuses on the wide band gap approach. “We instead chose narrow-gap semiconductors, such as indium arsenide, or gallium antimonide, as the host semiconductors,” Tanaka said. This choice enabled them to obtain ferromagnetism and conserve it at room temperature by adjusting doping concentrations.

Investigators have long envisioned bridging semiconductors and magnetism to create new opportunities of utilizing spin degrees of freedom and harnessing electron spin in semiconductors. But until now, ferromagnetic semiconductors have only worked under experimental conditions at extremely low, cold temperatures, typically lower than 200 K (-73oC), which is much colder than the freezing point of water, 273.15 K. Here, K (Kelvin) is a temperature scale which, like the Celsius (oC) scale, has 100 degrees between boiling (373.15 K = 100oC) and freezing (273.15 K = 0oC) of water.

Potential applications of ferromagnetic-semiconductors include designing new and improved devices, such as spin transistors.

“Spin transistors are expected to be used as the basic element of low-power-consumption, non-volatile and reconfigurable logic circuits,” Tanaka explained.

In 2012, the team postulated that using iron as magnetic doping agents in semiconductors would produce performance advantages not seen in the more frequently studied manganese class of dopants.

Skeptics doubted this approach, but the team continued and successfully created a ferromagnetic semiconductor known as “n-type.”

“This was thought impossible by almost all leading theorists,” Tanaka noted. “They predicted that such n-type ferromagnetic semiconductors cannot retain ferromagnetism at temperatures higher than 0.1 K. We demonstrated, however, many new functionalities, such as the quantum size effect and the ability to tune ferromagnetism by wave function manipulation.”

On a practical level, the team continues its research with the goal of applying iron-doped ferromagnetic semiconductors to the field of spintronic device innovation. On a theoretical level, the team is interested in re-evaluating conventional theories of magnetism in semiconductors. “Based on the results of many experimental tests, we have proven that ferromagnetism in our iron-doped semiconductor is intrinsic,” Tanaka said.

If using a single atom to capture high-resolution images of nanoscale material sounds like science fiction, think again.

That’s exactly what the Quantum Sensing and Imaging Group at UC Santa Barbara has achieved. Members of physicist Ania Jayich’s lab worked for two years to develop a radically new sensor technology capable of nanometer-scale spatial resolution and exquisite sensitivity. Their findings appear in the journal Nature Nanotechnology.

“This is the first tool of its kind,” said Jayich, UCSB’s Bruker Endowed Chair in Science and Engineering and associate director of the campus’s Materials Research Lab. “It operates from room temperature down to low temperatures where a lot of interesting physics happens. When thermal energy is low enough, the effects of electron interactions, for instance, become observable, leading to new phases of matter. And we can now probe these with unprecedented spatial resolution.”

Under the microscope, the unique single-spin quantum sensor resembles a toothbrush. Each “bristle” contains a single, solid nanofabricated diamond crystal with a special defect, a nitrogen-vacancy (NV) center, located at the tip. Two adjacent atoms are missing in the diamond’s carbon lattice, and one space has been filled with a nitrogen atom, allowing for the sensing of specific material properties, particularly magnetism. These sensors were manufactured in the clean room of UCSB’s Nanofabrication Facility.

The team chose to image a relatively well-studied superconducting material containing magnetic structures called vortices — localized regions of magnetic flux. With their instrument, the researchers were able to image individual vortices.

“Our tool is a quantum sensor because it relies on the bizarreness of quantum mechanics,” Jayich explained. “We put the NV defect into a quantum superposition where it can be one state or another — we don’t know — and then we let the system evolve in the presence of a field and measure it. This superposition uncertainty is what allows that measurement to occur.”

Such quantum behavior is often associated with low-temperature environments. However, the group’s specialized quantum instrument operates at room temperature and all the way down to 6 Kelvin (almost minus 450° Fahrenheit), making it very versatile, unique and capable of studying various phases of matter and the associated phase transitions.

“A lot of other microscopy tools don’t have that temperature range,” Jayich explained. “Further highlights of our tool are its excellent spatial resolution, afforded by the fact that the sensor comprises a single atom. Plus, its size makes it non-invasive, meaning it minimally affects the underlying physics in the materials system.”

The team is currently imaging skyrmions — quasiparticles with magnetic vortex-like configurations — with immense appeal for future data storage and spintronic technologies. Leveraging their instrument’s nanoscale spatial resolution, they aim to determine the relative strengths of competing interactions in the material that give rise to skyrmions. “There are a lot of different interactions between atoms and you need to understand all of them before you can predict how the material will behave,” Jayich said.

“If you can image the size of the material’s magnetic domains and how they evolve on small length scales, that gives you information about the value and strength of these interactions,” she added. “In the future, this tool will aid in understanding the nature and the strength of interactions in materials that then give rise to interesting new states and phases of matter, which are interesting from a fundamental physics perspective but also for technology.”

Quantum information science and technology has emerged as a new paradigm for dramatically faster computation and secure communication in the 21st century. At the heart of any quantum system is the most basic building block, the quantum bit or qbit, which carries the quantum information that can be transferred and processed (this is the quantum analogue of the bit used in current information systems). The most promising carrier qbit for ultimately fast, long distance quantum information transfer is the photon, the quantum unit of light.

The challenge facing scientists is to produce artificial sources of photons for various quantum information tasks. One of the biggest challenges is the development of efficient, scalable photon sources that can be mounted on a chip and operate at room temperature. Most sources used in labs today have to be very cold (at the temperature of liquid Helium, about -270C), which requires large and expensive refrigerators. Many sources also emit photons in undefined directions, making efficient collection a hard problem.

Now, a team of scientists from the Hebrew University of Jerusalem has demonstrated an efficient and compact single photon source that can operate on a chip at ambient temperatures. Using tiny nanocrystals made of semiconducting materials, the scientists developed a method in which a single nanocrystal can be accurately positioned on top of a specially designed and carefully fabricated nano-antenna.

In the same way large antennas on rooftops direct emission of classical radio waves for cellular and satellite transmissions, the nano-antenna efficiently directed the single photons emitted from the nanocrystals into a well-defined direction in space. This combined nanocrystals-nanoantenna device was able to produce a highly directional stream of single photons all flying to the same direction with a record low divergence angle. These photons were then collected with a very simple optical setup, and sent to be detected and analyzed using single photon detectors.

The team demonstrated that this hybrid device enhances the collection efficiency of single photons by more than a factor of 10 compared to a single nanocrystal without the antenna, without the need for complex and bulky optical collection systems used in many other experiments. Experimental results show that almost 40% of the photons are easily collected with a very simple optical apparatus, and over 20% of the photons are emitted into a very low numerical aperture, a 20-fold improvement over a freestanding quantum dot, and with a probability of more than 70% for a single photon emission. The single photon purity is limited only by emission from the metal, an obstacle that can be bypassed with careful design and fabrication.

The antennas were fabricated using simple metallic and dielectric layers using methods that are compatible with current industrial fabrication technologies, and many such devices can be fabricated densely on one small chip. The team is now working on a new generation of improved devices that will allow deterministic production of single photons straight from the chip into optical fibers, without any additional optical components, with a near unity efficiency.

“This research paves a promising route for a high purity, high efficiency, on-chip single photon source operating at room temperature, a concept that can be extended to many types of quantum emitters. A highly directional single photon source could lead to a significant progress in producing compact, cheap, and efficient sources of quantum information bits for future quantum technological applications”, said Prof. Ronen Rapaport, of the Racah Institute of Physics, The Department of Applied Physics, and the Center of Nanoscience and Nanotechnology at the Hebrew University of Jerusalem.

Mechanics know molybdenum disulfide (MoS2) as a useful lubricant in aircraft and motorcycle engines and in the CV and universal joints of trucks and automobiles. Rice University engineering researcher Isabell Thomann knows it as a remarkably light-absorbent substance that holds promise for the development of energy-efficient optoelectronic and photocatalytic devices.

“Basically, we want to understand how much light can be confined in an atomically thin semiconductor monolayer of MoS2,” said Thomann, assistant professor of electrical and computer engineering and of materials science and nanoengineering and of chemistry. “By using simple strategies, we were able to absorb 35 to 37 percent of the incident light in the 400- to 700-nanometer wavelength range, in a layer that is only 0.7 nanometers thick.”

Thomann and Rice graduate students Shah Mohammad Bahauddin and Hossein Robatjazi have recounted their findings in a paper titled “Broadband Absorption Engineering To Enhance Light Absorption in Monolayer MoS2,” which was recently published in the American Chemical Society journal ACS Photonics. The research has many applications, including development of efficient and inexpensive photovoltaic solar panels.

“Squeezing light into these extremely thin layers and extracting the generated charge carriers is an important problem in the field of two-dimensional materials,” she said. “That’s because monolayers of 2-D materials have different electronic and catalytic properties from their bulk or multilayer counterparts.”

Thomann and her team used a combination of numerical simulations, analytical models and experimental optical characterizations. Using three-dimensional electromagnetic simulations, they found that light absorption was enhanced 5.9 times compared with using MoS2 on a sapphire substrate.

“If light absorption in these materials was perfect, we’d be able to create all sorts of energy-efficient optoelectronic and photocatalytic devices. That’s the problem we’re trying to solve,” Thomann said.

She is pleased with her lab’s progress but concedes that much work remains to be done. “The goal, of course, is 100 percent absorption, and we’re not there yet.”

Researchers from the University of Illinois at Urbana-Champaign have developed a one-step, facile method to pattern graphene by using stencil mask and oxygen plasma reactive-ion etching, and subsequent polymer-free direct transfer to flexible substrates.

Graphene, a two-dimensional carbon allotrope, has received immense scientific and technological interest. Combining exceptional mechanical properties, superior carrier mobility, high thermal conductivity, hydrophobicity, and potentially low manufacturing cost, graphene provides a superior base material for next generation bioelectrical, electromechanical, optoelectronic, and thermal management applications.

“Significant progress has been made in the direct synthesis of large-area, uniform, high quality graphene films using chemical vapor deposition (CVD) with various precursors and catalyst substrates,” explained SungWoo Nam, an assistant professor of mechanical science and engineering at Illinois. “However, to date, the infrastructure requirements on post-synthesis processing–patterning and transfer–for creating interconnects, transistor channels, or device terminals have slowed the implementation of graphene in a wider range of applications.”

“In conjunction with the recent evolution of additive and subtractive manufacturing techniques such as 3D printing and computer numerical control milling, we developed a simple and scalable graphene patterning technique using a stencil mask fabricated via a laser cutter,” stated Keong Yong, a graduate student and first author of the paper, “Rapid Stencil Mask Fabrication Enabled One-Step Polymer-Free Graphene Patterning and Direct Transfer for Flexible Graphene Devices appearing in Scientific Reports.

“Our approach to patterning graphene is based on a shadow mask technique that has been employed for contact metal deposition,” Yong added. “Not only are these stencil masks easily and rapidly manufactured for iterative rapid prototyping, they are also reusable, enabling cost-effective pattern replication. And since our approach involves neither a polymeric transfer layer nor organic solvents, we are able to obtain contamination-free graphene patterns directly on various flexible substrates.”

Nam stated that this approach demonstrates a new possibility to overcome limitations imposed by existing post-synthesis processes to achieve graphene micro-patterning. Yong envisions this facile approach to graphene patterning sets forth transformative changes in “do It yourself” (DIY) graphene-based device development for broad applications including flexible circuits/devices and wearable electronics.

“This method allows rapid design iterations and pattern replications, and the polymer-free patterning technique promotes graphene of cleaner quality than other fabrication techniques,” Nam said. “We have shown that graphene can be patterned into varying geometrical shapes and sizes, and we have explored various substrates for the direct transfer of the patterned graphene.”

Tiny units of matter and chemistry that they are, atoms constitute the entire universe. Some rare atoms can store quantum information, an important phenomenon for scientists in their ongoing quest for a quantum Internet.

New research from UC Santa Barbara scientists and their Dutch colleagues exploits a system that has the potential to transfer optical quantum information to a locally stored solid-state quantum format, a requirement of quantum communication. The team’s findings appear in the journal Nature Photonics.

“Our research aims at creating a quantum analog of current fiber optic technology in which light is used to transfer classical information — bits with values zero or one — between computers,” said author Dirk Bouwmeester, a professor in UCSB’s Department of Physics. “The rare earth atoms we’re studying can store the superpositions of zero and one used in quantum computation. In addition, the light by which we communicate with these atoms can also store quantum information.”

Atoms are each composed of a nucleus typically surrounded by inner shells full of electrons and often have a partially filled outer electron shell. The optical and chemical properties of the atoms are mainly determined by the electrons in the outer shell.

Rare earth atoms such as erbium and ytterbium have the opposite composition: a partially filled inner shell surrounded by filled outer shells. This special configuration is what enables these atoms to store quantum information.

However, the unique composition of rare earth atoms leads to electronic transitions so well shielded from the surrounding atoms that optical interactions are extremely weak. Even when implanted in a host material, these atoms maintain those shielded transitions, which in principle can be addressed optically in order to store and retrieve quantum information.

Bouwmeester collaborated with John Bowers, a professor in UCSB’s Department of Electrical and Computer Engineering, and investigators at Leiden University in the Netherlands to strengthen these weak interactions by implanting ytterbium into ultra-high-quality optical storage rings on a silicon chip.

“The presence of the high-quality optical ring resonator — even if no light is injected — changes the fundamental optical properties of the embedded atoms, which leads to an order of magnitude increase in optical interaction strength with the ytterbium,” Bouwmeester said. “This increase, known as the Purcell effect, has an intricate dependence on the geometry of the optical light confinement.”

The team’s findings indicate that new samples currently under development at UCSB can enable optical communication to a single ytterbium atom inside optical circuits on a silicon chip, a phenomenon of significant interest for quantum information storage. The experiments also explore the way in which the Purcell effect enhances optical interaction with an ensemble of a few hundred rare earth atoms. The grouping itself has interesting collective properties that can also be explored for the storage of quantum information.

Key is an effect called a photon echo, the result of two distinct light pulses, the first of which causes atoms in ytterbium to become partially excited.

“The first light pulse creates a set of atoms we ‘talk’ to in a specific state and we call that state ‘in phase’ because all the atoms are created at the same time by this optical pulse,” Bouwmeester explained. “However, the individual atoms have slightly different frequencies because of residual coupling to neighboring atoms, which affects their time evolution and causes decoherence in the system.” Decoherence is the inability to keep track of how the system evolves in all its details.

“The trick is that the second light pulse changes the state of the system so that it evolves backwards, causing the atoms to return to the initial phase,” he continued. “This makes everything coherent and causes the atoms to collectively emit the light they absorbed from the first pulse.”

The strength of the photon echo contains important information about the fundamental properties of the ytterbium in the host material. “By analyzing the strength of these photon echoes, we are learning about the fundamental interactions of ytterbium with its surroundings,” Bouwmeester said. “Now we’re working on strengthening the Purcell effect by making the storage rings we use smaller and smaller.”

According to Bouwmeester, quantum computation needs to be compatible with optical communication for information to be shared and transmitted. “Our ultimate goal is to be able to communicate to a single ytterbium atom; then we can start transferring the quantum state of a single photon to a single ytterbium atom,” he added. “Coupling the quantum state of a photon to a quantum solid state is essential for the existence of a quantum Internet.”

One secret to creating the world’s fastest silicon-based flexible transistors: a very, very tiny knife.

Working in collaboration with colleagues around the country, University of Wisconsin-Madison engineers have pioneered a unique method that could allow manufacturers to easily and cheaply fabricate high-performance transistors with wireless capabilities on huge rolls of flexible plastic.

The researchers — led by Zhenqiang (Jack) Ma, the Lynn H. Matthias Professor in Engineering and Vilas Distinguished Achievement Professor in electrical and computer engineering, and research scientist Jung-Hun Seo — fabricated a transistor that operates at a record 38 gigahertz, though their simulations show it could be capable of operating at a mind-boggling 110 gigahertz. In computing, that translates to lightning-fast processor speeds.

It’s also very useful in wireless applications. The transistor can transmit data or transfer power wirelessly, a capability that could unlock advances in a whole host of applications ranging from wearable electronics to sensors.

The team published details of its advance April 20 in the journal Scientific Reports.

The researchers’ nanoscale fabrication method upends conventional lithographic approaches — which use light and chemicals to pattern flexible transistors — overcoming such limitations as light diffraction, imprecision that leads to short circuits of different contacts, and the need to fabricate the circuitry in multiple passes.

Using low-temperature processes, Ma, Seo and their colleagues patterned the circuitry on their flexible transistor — single-crystalline silicon ultimately placed on a polyethylene terephthalate (more commonly known as PET) substrate — drawing on a simple, low-cost process called nanoimprint lithography.

In a method called selective doping, researchers introduce impurities into materials in precise locations to enhance their properties — in this case, electrical conductivity. But sometimes the dopant merges into areas of the material it shouldn’t, causing what is known as the short channel effect. However, the UW-Madison researchers took an unconventional approach: They blanketed their single crystalline silicon with a dopant, rather than selectively doping it.

Then, they added a light-sensitive material, or photoresist layer, and used a technique called electron-beam lithography — which uses a focused beam of electrons to create shapes as narrow as 10 nanometers wide — on the photoresist to create a reusable mold of the nanoscale patterns they desired. They applied the mold to an ultrathin, very flexible silicon membrane to create a photoresist pattern. Then they finished with a dry-etching process — essentially, a nanoscale knife — that cut precise, nanometer-scale trenches in the silicon following the patterns in the mold, and added wide gates, which function as switches, atop the trenches.

With a unique, three-dimensional current-flow pattern, the high performance transistor consumes less energy and operates more efficiently. And because the researchers’ method enables them to slice much narrower trenches than conventional fabrication processes can, it also could enable semiconductor manufacturers to squeeze an even greater number of transistors onto an electronic device.

Ultimately, says Ma, because the mold can be reused, the method could easily scale for use in a technology called roll-to-roll processing (think of a giant, patterned rolling pin moving across sheets of plastic the size of a tabletop), and that would allow semiconductor manufacturers to repeat their pattern and mass-fabricate many devices on a roll of flexible plastic.

“Nanoimprint lithography addresses future applications for flexible electronics,” says Ma, whose work was supported by the Air Force Office of Scientific Research. “We don’t want to make them the way the semiconductor industry does now. Our step, which is most critical for roll-to-roll printing, is ready.”