Tag Archives: optoelectronics

Café Scientifique (Vancouver, Canada) April 25, 2017 talk: No Small Feat: Seeing Atoms and Molecules

I thought I’d been knocked off the list but finally I have a notice for an upcoming Café Scientifique talk that arrived and before the event, at that.  From an April 12, 2017 notice (received via email),

Our next café will happen on TUESDAY APRIL 25TH, 7:30PM in the back
room at YAGGER’S DOWNTOWN (433 W Pender). Our speaker for the
evening will be DR. SARAH BURKE, an Assistant Professor in the
Department of Physics and Astronomy/ Department of Chemistry at UBC [University of British Columbia]. The title of her talk is:

NO SMALL FEAT: SEEING ATOMS AND MOLECULES

From solar cells to superconductivity, the properties of materials and
the devices we make from them arise from the atomic scale structure of
the atoms that make up the material, their electrons, and how they all
interact.  Seeing this takes a microscope, but not like the one you may
have had as a kid or used in a university lab, which are limited to
seeing objects on the scale of the wavelength of visible light: still
thousands of times bigger than the size of an atom.  Scanning probe
microscopes operate more like a nanoscale record player, scanning a very
sharp tip over a surface and measuring interactions between the tip and
surface to create atomically resolved images.  These techniques show us
where atoms and electrons live at surfaces, on nanostructures, and in
molecules.  I will describe how these techniques give us a powerful
glimpse into a tiny world.

I have a little more about Sarah Burke from her webpage in the UBC Physics and Astronomy webspace,

Building an understanding of important electronic and optoelectronic processes in nanoscale materials from the atomic scale up will pave the way for next generation materials and technologies.

My research interests broadly encompass the study of electronic processes where nanoscale structure influences or reveals the underlying physics. Using scanning probe microscopy (SPM) techniques, my group investigates materials for organic electronics and optoelectronics, graphene and other carbon-based nanomaterials, and other materials where a nanoscale view offers the potential for new understanding. We also work to expand the SPM toolbox; developing new methods in order to probe different aspects of materials, and working to understand leading edge techniques.

For the really curious, you can find more information about her research group, UBC Laboratory for Atomic Imaging Research (LAIR) here.

Light-captured energetics (harvesting light for optoelectronics)

Comparing graphene to a tiger is unusual but that’s what researcher Sanfeng Wu does—eventually—in a May 13, 2016 University of Washington news release (also on EurekAlert) about his work,

In the quest to harvest light for electronics, the focal point is the moment when photons — light particles — encounter electrons, those negatively-charged subatomic particles that form the basis of our modern electronic lives. If conditions are right when electrons and photons meet, an exchange of energy can occur. Maximizing that transfer of energy is the key to making efficient light-captured energetics possible.

“This is the ideal, but finding high efficiency is very difficult,” said University of Washington physics doctoral student Sanfeng Wu. “Researchers have been looking for materials that will let them do this — one way is to make each absorbed photon transfer all of its energy to many electrons, instead of just one electron in traditional devices.”

In traditional light-harvesting methods, energy from one photon only excites one electron or none depending on the absorber’s energy gap, transferring just a small portion of light energy into electricity. The remaining energy is lost as heat. But in a paper released May 13 in Science Advances, Wu, UW associate professor Xiaodong Xu and colleagues at four other institutions describe one promising approach to coax photons into stimulating multiple electrons. Their method exploits some surprising quantum-level interactions to give one photon multiple potential electron partners. Wu and Xu, who has appointments in the UW’s Department of Materials Science & Engineering and the Department of Physics, made this surprising discovery using graphene.

There has been intense research on graphene’s electrical properties but the researchers’ discovery adds a new property to be investigated (from the news release),

“Graphene is a substance with many exciting properties,” said Wu, the paper’s lead author. “For our purposes, it shows a very efficient interaction with light.”

Graphene is a two-dimensional hexagonal lattice of carbon atoms bonded to one another, and electrons are able to move easily within graphene. The researchers took a single layer of graphene — just one sheet of carbon atoms thick — and sandwiched it between two thin layers of a material called boron-nitride.

Boron-nitride is a material that has excited a great deal of interest in the last 12 to 18 months (from the news release),

“Boron-nitride has a lattice structure that is very similar to graphene, but has very different chemical properties,” said Wu. “Electrons do not flow easily within boron-nitride; it essentially acts as an insulator.”

Xu and Wu discovered that when the graphene layer’s lattice is aligned with the layers of boron-nitride, a type of “superlattice” is created with properties allowing efficient optoelectronics that researchers had sought. These properties rely on quantum mechanics, the occasionally baffling rules that govern interactions between all known particles of matter. Wu and Xu detected unique quantum regions within the superlattice known as Van Hove singularities.

Here’s an animated .gif illustrating the superlattice in action,

The Moire superlattice they created by aligning graphene and boron-nitride. Credit: Sanfeng Wu.

The Moire superlattice they created by aligning graphene and boron-nitride. Credit: Sanfeng Wu.

The news release goes on to describe the Van Hove singularities within the superlattice and to mention the ‘tiger’,

“These are regions of huge electron density of states, and they were not accessed in either the graphene or boron-nitride alone,” said Wu. “We only created these high electron density regions in an accessible way when both layers were aligned together.”

When Xu and Wu directed energetic photons toward the superlattice, they discovered that those Van Hove singularities were sites where one energized photon could transfer its energy to multiple electrons that are subsequently collected by electrodes— not just one electron or none with the remaining energy lost as heat. By a conservative estimate, Xu and Wu report that within this superlattice one photon could “kick” as many as five electrons to flow as current.

With the discovery of collecting multiple electrons upon the absorption of one photon, researchers may be able to create highly efficient devices that could harvest light with a large energy profit. Future work would need to uncover how to organize the excited electrons into electrical current for optimizing the energy-converting efficiency and remove some of the more cumbersome properties of their superlattice, such as the need for a magnetic field. But they believe this efficient process between photons and electrons represents major progress.

“Graphene is a tiger with great potential for optoelectronics, but locked in a cage,” said Wu. “The singularities in this superlattice are a key to unlocking that cage and releasing graphene’s potential for light harvesting application.”

H/t to a May 13, 2016 news item on phys.org.

Here’s a link to and a citation for the paper,

Multiple hot-carrier collection in photo-excited graphene Moiré superlattices by Sanfeng Wu, Lei Wang, You Lai, Wen-Yu Shan, Grant Aivazian, Xian Zhang, Takashi Taniguchi, Kenji Watanabe, Di Xiao, Cory Dean, James Hone, Zhiqiang Li, and Xiaodong Xu. Science Advances 13 May 2016: Vol. 2, no. 5, e1600002 DOI: 10.1126/sciadv.1600002

This paper is open access.

Dissipating heat with graphene-based film

As the summer approaches here in the Northern Hemisphere I think longingly of frost and snow and so readers may find more than the usual number of stories about ‘cooling’. On that note, Chalmers Technical University (Sweden) is announcing some new research into cooling graphene-based films, from an April 29, 2016 news item on ScienceDaily,

Heat dissipation in electronics and optoelectronics is a severe bottleneck in the further development of systems in these fields. To come to grips with this serious issue, researchers at Chalmers University of Technology have developed an efficient way of cooling electronics by using functionalized graphene nanoflakes. …

“Essentially, we have found a golden key with which to achieve efficient heat transport in electronics and other power devices by using graphene nanoflake-based film. This can open up potential uses of this kind of film in broad areas, and we are getting closer to pilot-scale production based on this discovery,” says Johan Liu, Professor of Electronics Production at Chalmers University of Technology in Sweden.

An April 29, 2016 Chalmers Technical University press release (also on EurekAlert), which originated the news item, describes the work in more detail,

The researchers studied the heat transfer enhancement of the film with different functionalized amino-based and azide-based silane molecules, and found that the heat transfer efficiency of the film can be improved by over 76 percent by introducing functionalization molecules, compared to a reference system without the functional layer. This is mainly because the contact resistance was drastically reduced by introducing the functionalization molecules.

Meanwhile, molecular dynamic simulations and ab initio calculations reveal that the functional layer constrains the cross-plane scattering of low-frequency phonons, which in turn enhances in-plane heat-conduction of the bonded film by recovering the long flexural phonon lifetime. The results suggested potential thermal management solutions for electronic devices.

In the research, scientists studied a number of molecules that were immobilized at the interfaces and at the edge of graphene nanoflake-based sheets forming covalent bonds. They also probed interface thermal resistance by using a photo-thermal reflectance measurement technique to demonstrate an improved thermal coupling due to functionalization.

“This is the first time that such systematic research has been done. The present work is much more extensive than previously published results from several involved partners, and it covers more functionalization molecules and also more extensive direct evidence of the thermal contact resistance measurement,” says Johan Liu.

Here’s a link to and a citation for the paper,

Functionalization mediates heat transport in graphene nanoflakes by Haoxue Han, Yong Zhang, Nan Wang, Majid Kabiri Samani, Yuxiang Ni, Zainelabideen Y. Mijbil, Michael Edwards, Shiyun Xiong, Kimmo Sääskilahti, Murali Murugesan, Yifeng Fu, Lilei Ye, Hatef Sadeghi, Steven Bailey, Yuriy A. Kosevich, Colin J. Lambert, Johan Liu, & Sebastian Volz. Nature Communications 7, Article number: 11281  doi:10.1038/ncomms11281 Published 29 April 2016

This is an open access paper.

Transition metal dichalcogenides (molybdenum disulfide and tungsten diselenide) rock the graphene boat

Anyone who’s read stories about scientific discovery knows that the early stages are characterized by a number of possibilities so the current race to unseat graphene as the wonder material of the nanoworld is a ‘business as usual’ sign although I imagine it can be confusing for investors and others hoping to make their fortunes. As for the contenders to the ‘wonder nanomaterial throne’, they are transition metal dichalcogenides: molybdenum disulfide and tungsten diselenide both of which have garnered some recent attention.

A March 12, 2014 news item on Nanwerk features research on molybdenum disulfide from Poland,

Will one-atom-thick layers of molybdenum disulfide, a compound that occurs naturally in rocks, prove to be better than graphene for electronic applications? There are many signs that might prove to be the case. But physicists from the Faculty of Physics at the University of Warsaw have shown that the nature of the phenomena occurring in layered materials are still ill-understood and require further research.

….

Researchers at the University of Warsaw, Faculty of Physics (FUW) have shown that the phenomena occurring in the crystal network of molybdenum disulfide sheets are of a slightly different nature than previously thought. A report describing the discovery, achieved in collaboration with Laboratoire National des Champs Magnétiques Intenses in Grenoble, has recently been published in Applied Physics Letters.

“It will not become possible to construct complex electronic systems consisting of individual atomic sheets until we have a sufficiently good understanding of the physics involved in the phenomena occurring within the crystal network of those materials. Our research shows, however, that research still has a long way to go in this field”, says Prof. Adam Babinski at the UW Faculty of Physics.

A March 12, 2014 Dept. of Physics University of Warsaw (FUW) news release, which originated the news item, describes the researchers’ ideas about graphene and alternative materials such as molybdenum disulfide,

“It will not become possible to construct complex electronic systems consisting of individual atomic sheets until we have a sufficiently good understanding of the physics involved in the phenomena occurring within the crystal network of those materials. Our research shows, however, that research still has a long way to go in this field”, says Prof. Adam Babiński at the UW Faculty of Physics.

The simplest method of creating graphene is called exfoliation: a piece of scotch tape is first stuck to a piece of graphite, then peeled off. Among the particles that remain stuck to the tape, one can find microscopic layers of graphene. This is because graphite consists of many graphene sheets adjacent to one another. The carbon atoms within each layer are very strongly bound to one another (by covalent bonds, to which graphene owes its legendary resilience), but the individual layers are held together by significantly weaker bonds (van de Walls [van der Waals] bonds). Ordinary scotch tape is strong enough to break the latter and to tear individual graphene sheets away from the graphite crystal.

A few years ago it was noticed that just as graphene can be obtained from graphite, sheets a single atom thick can similarly be obtained from many other crystals. This has been successfully done, for instance, with transition metals chalcogenides (sulfides, selenides, and tellurides). Layers of molybdenum disulfide (MoS2), in particular, have proven to be a very interesting material. This compound exists in nature as molybdenite, a crystal material found in rocks around the world, frequently taking the characteristic form of silver-colored hexagonal plates. For years molybdenite has been used in the manufacturing of lubricants and metal alloys. Like in the case of graphite, the properties of single-atom sheets of MoS2 long went unnoticed.

From the standpoint of applications in electronics, molybdenum disulfide sheets exhibit a significant advantage over graphene: they have an energy gap, an energy range within which no electron states can exist. By applying electric field, the material can be switched between a state that conducts electricity and one that behaves like an insulator. By current calculations, a switched-off molybdenum disulfide transistor would consume even as little as several hundred thousand times less energy than a silicon transistor. Graphene, on the other hand, has no energy gap and transistors made of graphene cannot be fully switched off.

The news release goes on to describe how the researchers refined their understanding of molybdenum disulfide and its properties,

Valuable information about a crystal’s structure and phenomena occurring within it can be obtained by analyzing how light gets scattered within the material. Photons of a given energy are usually absorbed by the atoms and molecules of the material, then reemitted at the same energy. In the spectrum of the scattered light one can then see a distinctive peak, corresponding to that energy. It turns out, however, that one out of many millions of photons is able to use some of its energy otherwise, for instance to alter the vibration or circulation of a molecule. The reverse situation also sometimes occurs: a photon may take away some of the energy of a molecule, and so its own energy slightly increases. In this situation, known as Raman scattering, two smaller peaks are observed to either side of the main peak.

The scientists at the UW Faculty of Physics analyzed the Raman spectra of molybdenum disulfide carrying on low-temperature microscopic measurements. The higher sensitivity of the equipment and detailed analysis methods enabled the team to propose a more precise model of the phenomena occurring in the crystal network of molybdenum disulfide.

“In the case of single-layer materials, the shape of the Raman lines has previously been explained in terms of phenomena involving certain characteristic vibrations of the crystal network. We have shown for molybdenum disulfide sheets that the effects ascribed to those vibrations must actually, at least in part, be due to other network vibrations not previously taken into account”, explains Katarzyna Gołasa, a doctorate student at the UW Faculty of Physics.

The presence of the new type of vibration in single-sheet materials has an impact on how electrons behave. As a consequence, these materials must have somewhat different electronic properties than previously anticipated.

Here’s what the rocks look like,

Molybdenum disulfide occurs in nature as molybdenite, crystalline material that frequently takes the characteristic form of silver-colored hexagonal plates. (Source: FUW)

Molybdenum disulfide occurs in nature as molybdenite, crystalline material that frequently takes the characteristic form of silver-colored hexagonal plates. (Source: FUW)

I am not able to find the published research at this time (March 13, 2014).

The tungsten diselenide story is specifically application-centric. Dexter Johnson in a March 11, 2014 post on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) describes the differing perspectives and potential applications suggested by the three teams that cooperated to produce papers united by a joint theme ,

The three research groups focused on optoelectronics applications of tungsten diselenide, but each with a slightly different emphasis.

The University of Washington scientists highlighted applications of the material for a light emitting diode (LED). The Vienna University of Technology group focused on the material’s photovoltaic applications. And, finally, the MIT [Massachusetts Institute of Technology] group looked at all of the optoelectronic applications for the material that would result from the way it can be switched from being a p-type to a n-type semiconductor.

Here are some details of the research from each of the institutions’ news releases.

A March 10, 2014 University of Washington (state) news release highlights their LED work,

University of Washington [UW] scientists have built the thinnest-known LED that can be used as a source of light energy in electronics. The LED is based off of two-dimensional, flexible semiconductors, making it possible to stack or use in much smaller and more diverse applications than current technology allows.

“We are able to make the thinnest-possible LEDs, only three atoms thick yet mechanically strong. Such thin and foldable LEDs are critical for future portable and integrated electronic devices,” said Xiaodong Xu, a UW assistant professor in materials science and engineering and in physics.

The UW’s LED is made from flat sheets of the molecular semiconductor known as tungsten diselenide, a member of a group of two-dimensional materials that have been recently identified as the thinnest-known semiconductors. Researchers use regular adhesive tape to extract a single sheet of this material from thick, layered pieces in a method inspired by the 2010 Nobel Prize in Physics awarded to the University of Manchester for isolating one-atom-thick flakes of carbon, called graphene, from a piece of graphite.

In addition to light-emitting applications, this technology could open doors for using light as interconnects to run nano-scale computer chips instead of standard devices that operate off the movement of electrons, or electricity. The latter process creates a lot of heat and wastes power, whereas sending light through a chip to achieve the same purpose would be highly efficient.

“A promising solution is to replace the electrical interconnect with optical ones, which will maintain the high bandwidth but consume less energy,” Xu said. “Our work makes it possible to make highly integrated and energy-efficient devices in areas such as lighting, optical communication and nano lasers.”

Here’s a link to and a citation for this team’s paper,

Electrically tunable excitonic light-emitting diodes based on monolayer WSe2 p–n junctions by Jason S. Ross, Philip Klement, Aaron M. Jones, Nirmal J. Ghimire, Jiaqiang Yan, D. G. Mandrus, Takashi Taniguchi, Kenji Watanabe, Kenji Kitamura, Wang Yao, David H. Cobden, & Xiaodong Xu. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.26 Published online 09 March 2014

This paper is behind a paywall.

A March 9, 2014 University of Vienna news release highlights their work on tungsten diselinide and its possible application in solar cells,

… With graphene as a light detector, optical signals can be transformed into electric pulses on extremely short timescales.

For one very similar application, however, graphene is not well suited for building solar cells. “The electronic states in graphene are not very practical for creating photovoltaics”, says Thomas Mueller. Therefore, he and his team started to look for other materials, which, similarly to graphene, can arranged in ultrathin layers, but have even better electronic properties.

The material of choice was tungsten diselenide: It consists of one layer of tungsten atoms, which are connected by selenium atoms above and below the tungsten plane. The material absorbs light, much like graphene, but in tungsten diselenide, this light can be used to create electrical power.

The layer is so thin that 95% of the light just passes through – but a tenth of the remaining five percent, which are absorbed by the material, are converted into electrical power. Therefore, the internal efficiency is quite high. A larger portion of the incident light can be used if several of the ultrathin layers are stacked on top of each other – but sometimes the high transparency can be a useful side effect. “We are envisioning solar cell layers on glass facades, which let part of the light into the building while at the same time creating electricity”, says Thomas Mueller.

Today, standard solar cells are mostly made of silicon, they are rather bulky and inflexible. Organic materials are also used for opto-electronic applications, but they age rather quickly. “A big advantage of two-dimensional structures of single atomic layers is their crystallinity. Crystal structures lend stability”, says Thomas Mueller.

Here’s a link to and a citation for the University of Vienna paper,

Solar-energy conversion and light emission in an atomic monolayer p–n diode by Andreas Pospischil, Marco M. Furchi, & Thomas Mueller. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.14 Published online 09 March 2014

This paper is behind a paywll.

Finally, a March 10, 2014 MIT news release details their work about material able to switch from p-type (p = positive) to a n-type (n = negative) semiconductors,

The material they used, called tungsten diselenide (WSe2), is part of a class of single-molecule-thick materials under investigation for possible use in new optoelectronic devices — ones that can manipulate the interactions of light and electricity. In these experiments, the MIT researchers were able to use the material to produce diodes, the basic building block of modern electronics.

Typically, diodes (which allow electrons to flow in only one direction) are made by “doping,” which is a process of injecting other atoms into the crystal structure of a host material. By using different materials for this irreversible process, it is possible to make either of the two basic kinds of semiconducting materials, p-type or n-type.

But with the new material, either p-type or n-type functions can be obtained just by bringing the vanishingly thin film into very close proximity with an adjacent metal electrode, and tuning the voltage in this electrode from positive to negative. That means the material can easily and instantly be switched from one type to the other, which is rarely the case with conventional semiconductors.

In their experiments, the MIT team produced a device with a sheet of WSe2 material that was electrically doped half n-type and half p-type, creating a working diode that has properties “very close to the ideal,” Jarillo-Herrero says.

By making diodes, it is possible to produce all three basic optoelectronic devices — photodetectors, photovoltaic cells, and LEDs; the MIT team has demonstrated all three, Jarillo-Herrero says. While these are proof-of-concept devices, and not designed for scaling up, the successful demonstration could point the way toward a wide range of potential uses, he says.

“It’s known how to make very large-area materials” of this type, Churchill says. While further work will be required, he says, “there’s no reason you wouldn’t be able to do it on an industrial scale.”

In principle, Jarillo-Herrero says, because this material can be engineered to produce different values of a key property called bandgap, it should be possible to make LEDs that produce any color — something that is difficult to do with conventional materials. And because the material is so thin, transparent, and lightweight, devices such as solar cells or displays could potentially be built into building or vehicle windows, or even incorporated into clothing, he says.

While selenium is not as abundant as silicon or other promising materials for electronics, the thinness of these sheets is a big advantage, Churchill points out: “It’s thousands or tens of thousands of times thinner” than conventional diode materials, “so you’d use thousands of times less material” to make devices of a given size.

Here’s a link to and a citation for the MIT paper,

Optoelectronic devices based on electrically tunable p–n diodes in a monolayer dichalcogenide by Britton W. H. Baugher, Hugh O. H. Churchill, Yafang Yang, & Pablo Jarillo-Herrero. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.25 Published online 09 March 2014

This paper is behind a paywall.

These are very exciting, if not to say, electrifying times. (Couldn’t resist the wordplay.)

Archivists, rejoice! Fused quartz stores data for millions of years at the University of Southampton (UK)

There’s a July 9,  2013 news item on Nanowerk touting nanostructured glass device which is being compared to Superman’s memory crystal (see this Wikipedia essay on Superman’s Fortress of Solitude for a description of Superman’s memory crystals),

Using nanostructured glass, scientists at the University of Southampton have, for the first time, experimentally demonstrated the recording and retrieval processes of five dimensional digital data by femtosecond laser writing. The storage allows unprecedented parameters including 360 TB/disc data capacity, thermal stability up to 1000°C and practically unlimited lifetime.

Coined as the ‘Superman’ memory crystal, as the glass memory has been compared to the “memory crystals” used in the Superman films, the data is recorded via self-assembled nanostructures created in fused quartz, which is able to store vast quantities of data for over a million years. The information encoding is realised in five dimensions: the size and orientation in addition to the three dimensional position of these nanostructures. [emphases mine]

The July 9, 2013 University of Southampton news release, which originated the news item, provides more details,

A 300 kb digital copy of a text file was successfully recorded in 5D using ultrafast laser, producing extremely short and intense pulses of light. The file is written in three layers of nanostructured dots separated by five micrometres (one millionth of a metre).

The self-assembled nanostructures change the way light travels through glass, modifying polarisation of light that can then be read by combination of optical microscope and a polariser, similar to that found in Polaroid sunglasses.

The research is led by Jingyu Zhang from the University’s Optoelectronics Research Centre (ORC) and conducted under a joint project with Eindhoven University of Technology.

“We are developing a very stable and safe form of portable memory using glass, which could be highly useful for organisations with big archives. At the moment companies have to back up their archives every five to ten years because hard-drive memory has a relatively short lifespan,” says Jingyu. [emphasis mine]

“Museums who want to preserve information or places like the national archives where they have huge numbers of documents, would really benefit.”

This work was presented at the CLEO 2013 (Conference on Lasers and Electro-Optics in San Jose [US]). Here’s a link to and a citation for the 2 pp presentation paper,

5D Data Storage by Ultrafast Laser Nanostructuring in Glass by Jingyu Zhang, Mindaugas Gecevičius, Martynas Beresna, and Peter G. Kazansky. Presentation paper for CLEO 2013

© 2013 Optical Society of America OCIS codes (140.3390) Laser materials processing, (210.0210) Optical data storage

This research was conducted as part of the European Union’s Femtoprint project, which is funded under the Framework Programme 7 initiative. Here’s more about Femtoprint from the homepage,

FEMTOPRINT is to develop a printer for microsystems with nano-scale features fabricated out of glass. Our ultimate goal is to provide a large pool of users from industry, research and universities with the capability of producing their own micro-systems, in a rapid-manner without the need for expensive infrastructures and specific expertise. Recent researches have shown that one can form three-dimensional patterns in glass material using low-power femtosecond laser beam. This simple process opens interesting new opportunities for a broad variety of microsystems with feature sizes down to the nano-scale. These patterns can be used to form integrated optics components or be ‘developed’ by chemically etching to form three-dimensional structures like fluidic channels and micro-mechanical components. Worth noticing, sub-micron resolution can be achieved and sub-pattern smaller than the laser wavelength can be formed. Thanks to the low-energy required to pattern the glass, femtosecond laser consisting simply of an oscillator are sufficient to produce such micro- and nano- systems.

These systems are nowadays table-top and cost a fraction of conventional clean-room equipments. It is highly foreseeable that within 3 to 5 years such laser systems will fit in a shoe-box. The project specific objectives are:

1/ Develop a femtosecond laser suitable for glass micro-/nano- manufacturing that fits in a shoe-box

2/ Integrate the laser in a machine similar to a printer that can position and manipulate glass sheets of various thicknesses

3/ Demonstrate the use of the printer to fabricate a variety of micro-/nano-systems with optical, mechanical and fluid-handling capabilities. A clear and measurable outcome of Femtoprint will be to be in a situation to commercialize the ‘femtoprinter’ through the setting-up of a consortium spin-off. The potential economical impact is large and is expected in various industrial sectors.

I think any archivist hearing about data storage that can last a million years will be thrilled although I suspect it’s going to be a long, long time before these 5D ‘memory’ crystals are going to be storing any data for anyone. In the meantime, there are efforts such as the Council of Canadian Academies’ (CCA) Memory Institutions and the Digital Revolution assessment (mentioned 2/3 of the way down in my June 5, 2013 posting).

Vancouver (Canada)-based company, Lumerical Solutions, files patent on new optoelectronic simulation software

I’m not a huge *fan of patents as per various postings (my Oct. 31, 2011 posting is probably my most overt statement) so I’m not entirely thrilled about this news from Lumerical Solutions, Inc. According to the June 14, 2012 news item on Nanowerk,

Lumerical Solutions, Inc., a global provider of optoelectronic design software, announced the filing of a provisional patent application titled, “System and Method for Transforming a Coordinate System to Simulate an Anisotropic Medium.” The patent application, filed with the US Patent and Trademark Office, describes how the optical response of dispersive, spatially varying anisotropic media can be efficiently simulated on a discretized grid like that employed by finite-difference time-domain (FDTD) or finite-element method (FEM) simulators. The invention disclosed is relevant to a wide array of applications including liquid crystal display (LCD) panels, microdisplays, spatial light modulators, integrated components using liquid crystal on silicon (LCOS) technology like LCOS optical switches, and magneto-optical elements in optical communication and sensing systems.

The company’s June 14, 2012 news release includes this comment from the founder and Chief Technical Office (CTO),

According to Dr. James Pond, the inventor and Lumerical’s Chief Technology Officer, “many next generation opto-electronic products combine complicated materials and nano-scale structure, which is beyond the capabilities of existing simulation tools. Lumerical’s enhanced framework allows designers to accurately simulate everything from liquid crystal displays to OLEDs, and silicon photonics to integrated quantum computing components.”

Lumerical’s new methodology for efficiently simulating anisotropic media is part of a larger effort to allow designers the ability to model the optical response of many different types of materials.  In addition to the disclosed invention, Lumerical has added a material plugin capability which will enable external parties to include complicated material models, such as those required for modelling semiconductor lasers or non-linear optical devices, into FDTD-based simulation projects.

…  According to Chris Koo, an engineer with Samsung, “Lumerical’s latest innovation has established them as the clear leader in the field of optoelectronic device modeling.  Their comprehensive material modeling capabilities paves the way for the development of exciting new technologies.”

I wish the company good luck. Despite my reservations about current patent regimes, I do appreciate that in some situations, it’s best to apply for a patent.

For the curious, here’s a little more (from the company’s About Lumerical page),

By empowering research and product development professionals with high performance optical design software that leverages recent advances in computing technology, Lumerical helps optical designers tackle challenging design goals and meet strict deadlines. Lumerical’s design software solutions are employed in more than 30 countries by global technology leaders like Agilent, ASML, Bosch, Canon, Harris, Northrop Grumman, Olympus, Philips, Samsung, and STMicroelectronics, and prominent research institutions including Caltech, Harvard, Max Planck Institute, MIT, NIST and the Chinese Academy of Sciences.

Our Name

Lu.min.ous (loo’me-nes) adj., full of light, illuminated

Nu.mer.i.cal (noo-mer’i-kel) adj., of or relating to a number or series of numbers

Lu.mer.i.cal (loo-mer’i-kel) – A company that delivers inventive, highly accurate and cost effective design solutions resulting in significant improvements in product development costs and speed-to-market.

* June 15, 2012: I found the error this morning (9:20 am PDT) and added the word ‘fan’.

Quantum dots and graphene; a mini roundup

I’ve done very little writing about quantum dots (so much nano, so little time) but there’s been a fair amount of activity lately which has piqued my interest. In the last few days researchers at Kansas State University have been getting noticed for being able to control the size and shape of the graphene quantum dots they produce.  This one has gotten extensive coverage online including this May 17, 2012 news item on physorg.com,

Vikas Berry, William H. Honstead professor of chemical engineering, has developed a novel process that uses a diamond knife to cleave graphite into graphite nanoblocks, which are precursors for graphene quantum dots. These nanoblocks are then exfoliated to produce ultrasmall sheets of carbon atoms of controlled shape and size.

By controlling the size and shape, the researchers can control graphene’s properties over a wide range for varied applications, such as solar cells, electronics, optical dyes, biomarkers, composites and particulate systems. Their work has been published in Nature Communications and supports the university’s vision to become a top 50 public research university by 2025. The article is available online.

Here’s an image of graphene being cut by a diamond knife from the May 16, 2012 posting by jtorline on the K-State News blog,

Molecular dynamics snapshot of stretched graphene being nanotomed via a diamond knife.

Here’s why standardizing the size is so important,

While other researchers have been able to make quantum dots, Berry’s research team can make quantum dots with a controlled structure in large quantities, which may allow these optically active quantum dots to be used in solar cell and other optoelectronic applications. [emphasis mine]

While all this is happening in Kansas, the Econ0mist magazine published a May 12, 2012 article about some important quantum dot optoelectronic developments in Spain (an excellent description for relative beginners is given and, if this area interests you, I’d suggest reading it in full),

Actually converting the wonders of graphene into products has been tough. But Frank Koppens and his colleagues at the Institute of Photonic Sciences in Barcelona think they have found a way to do so. As they describe in Nature Nanotechnology, they believe graphene can be used to make ultra-sensitive, low-cost photodetectors.

A typical photodetector is made of a silicon chip a few millimetres across onto which light is focused by a small lens. Light striking the chip knocks electrons free from some of the silicon atoms, producing a signal that the chip’s electronics convert into a picture or other useful information. …

Silicon photodetectors suffer, though, from a handicap: they are inflexible. Nor are they particularly cheap. And they are not that sensitive. They absorb only 10-20% of the light that falls on to them. For years, therefore, engineers have been on the lookout for a cheap, bendable, sensitive photodetector. …

By itself, graphene is worse than silicon at absorbing light. According to Dr Koppens only 2.7% of the photons falling on it are captured. But he and his colleague Gerasimos Konstantatos have managed to increase this to more than 50% by spraying tiny crystals of lead sulphide onto the surface of the material.

So combining the ability to size quantum dots uniformly with this discovery on how to make graphene more sensitive (and more useful in potential products) with quantum dots suggests some very exciting possibilities including this one mentioned by Dexter Johnson (who’s living in Spain these days) in his May 16, 2012 posting on Nanoclast (on the Institute of Electrical and Electronics Engineers [IEEE] website),

The researchers offer a range of applications for the graphene-and-quantum-dot combination, including digital cameras and sensors.  [emphasis mine] But it seems the researchers seem particularly excited about one application in particular. They expect the material will be used for night-vision technologies in automobiles—an application I have never heard trotted out before in relation to nanotech.

You can get more insights, more precise descriptions if you want to follow up from the Econ0mist article,  and Dexter’s links to more information about the research in his posting.

In my final roundup piece, I received a news release (dated April 24, 2012) about a quantum dot commercialization project at the University of Utah,

One of the biggest challenges for advancing quantum dots is the manufacturing process. Conventional processes are expensive, require high temperatures and produce low yields. However, researchers at the University of Utah believe they have a solution. They recently formed a startup company called Navillum Nanotechnologies, and their efforts are gaining national attention with help from a team of M.B.A. students from the David Eccles School of Business.
The students recently won first place and $100,000 at the regional CU Cleantech New Venture Challenge. The student competition concluded at the University of Colorado in Boulder on Friday, April 20. The student team advances to the national championship, which will be held in June in Washington, D.C. Student teams from six regions will compete for additional prizes and recognition at the prestigious event. Other regional competitions were held at MIT, Cal Tech, the University of Maryland, Clean Energy Trust (Chicago) and Rice University. All the competitions are financed by the U.S. Department of Energy.

The students will be competing in the national Clean Energy Business Plan Competition taking place June 12-13, 2012 in Washington, D.C.  Here are a few more details from the national competition webpage,

Winners of the six regional competitions will represent their home universities and regions as they vie for the honor of presenting the best clean energy business plan before a distinguished panel of expert judges and invited guests from federal agencies, industry, national labs and the venture capital community.

Confirmed Attendees include:

The Honorable Steven Chu
Energy Secretary [US federal government]

Dr. David Danielson
Assistant Secretary, EERE  [US Dept. of Energy, energy efficiency and renewable energy technologies)

Dr. Karina Edmonds
Technology Transfer Coordinator [US Dept. of Energy]

Mr. Todd Park
Chief Technology Officer, White House

Good luck to the students!

A*STAR and University of Washington joint optoelectronics project

At the University of Washington located in Seattle, a joint project with A*STAR, Singapore’s Agency for Science, Technology and Research is about to get underway. From the Sept. 16, 2011 news item on Nanowerk,

A*STAR Institute of Microelectronics (IME) and the University of Washington announce that they will join forces to provide shared Silicon Photonics processes as part of the Optoelectronics Systems Integration in Silicon programme (OpSIS). This will help the research and development (R&D) community significantly reduce the fabrication cost of silicon photonics integrated circuits.

The silicon photonics integrated circuits to be created under this programme will be immediately available to the photonic research community worldwide, and in the process, facilitate technological advancements and proliferate creative ideas for the development of the next generation devices. As the platform will be offered through multi-project wafer (MPW) runs, which allow users from multiple projects to share the costs of a single fabrication run, research costs are lowered significantly for individual projects.

More information at A*STAR’s Institute of Microeletronics (IME) can be found here and about the University of Washington’s OpSIS programme here.