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October 22, 2009 – A team of researchers from the US have created a new multiferroic material possessing seemingly contradictory properties of magnetism and polar order, and another group of scientists from the US and the Netherlands say they can control suchmultiferroic properties — achievements that have implications in future electronics and particularly memory devices.

Magnetic ferroelectrics could be used as magnetic switches (by reversing their electric fields) in future memory, sensors, actuators, and multifunction devices. Through their work, researchers from Argonne National Labs, Penn State U., the U. of Chicago, and Cornell U. proved a high-pressure form of polycrystalline FETiO3 possesses the unusual combination of weak ferromagnetism (below 120 Kelvin) and ferroelectric polarization (at and below room temperature). Results, published in July by Physical Review Letters, were obtained by using piezoresponse force microscopy, optical second harmonic generation, and magnetometry. Funding for their research was provided by the US Department of Energy.

Meanwhile, researchers from the U. of Twente, Oakridge National Labs, U. of California/Berkeley, and Penn State say they have used an electrical signal to control both the elastic and magnetic properties of such a nanomaterial "in an orderly way," opening up new possibilities for storage devices with very high data densities.

Their work, published online by Nature Nanotechnology, applied an electrical voltage to the needle of a scanning probe microscopy and moved it over the surface of a bismuth ferrate (BiFeO3) structure to "charge" it with different elastic and magnetic properties "at a very localized level."

From their paper abstract:

The ability to control local elastic, magnetic, and torroidal order parameters with an electric field will make it possible to probe local strain and magnetic ordering, and engineer various magnetoelectric, domain-wall-based, and strain-coupled devices.

 

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Manipulation of the polarization in nanostructures: (a) an artificial star, (b) a diamond pattern. (Source: U. of Twente)

 

October 20, 2009 – IMEC and packaging/assembly firm Terepac are collaborating on development of flexible packages for IMEC’s biomedical heart monitoring device.

Their work centers on IMEC’s wireless electrocardiogram (ECG) patch initially developed in 2007 within the Holst Center’s Human++ Program in Eindhoven, The Netherlands. Under this new partnership, the wireless ECG patch will be a test vehicle for Terepac’s photochemical printing process, which places thin silicon dies and passive components onto flexible substrates at rates >1chip/sec, and "accuracies down to a few microns," the company claims.

For IMEC, the addition of Terepac’s flexible packaging technology advances its work on the wireless ECG patch from lab-scale assembly on a polyimide carrier "to a more production-ready version of its wireless sensor nodes." Initial results are expected by mid-2010. After just a few months of contacts, "it quickly became clear that their expertise would be a valuable addition to the existing competences that we and our partners have on board," noted Julien Penders, program manager for body area networks at IMEC/Holst Centre, in a statement. "Being able to tap into the existing partner network of IMEC and Holst Centre is a great asset to our collaboration," added Terepac CEO Ric Asselstine.

IMEC’s work at the Holst Center also has created a miniaturized eight-channel wireless EEG system for remotely monitoring brainwaves of patients in their daily environment, presumably resulting in more comfortable patients and more natural readings.

October 16, 2009 – What do jazz music and nanotechnology have in common? More than you might think, according to a researcher at the U. of Albany and a concert musician. Exploring those commonalities is one of several activities lined up as part of a collection of events lined up by the school in the next few weeks, collectively dubbed "Nanovember."

Among the activities on tap:

– "Nano in the Mall" at the Crossgates Mall (down the street from the school), where shoppers can learn how nanotech applies to everyday-living energy efficiency;

– "NanoExplorations," giving Girl Scouts a tour of the Albany NanoTech Complex and hands-on activities illustrating nano R&D;

– Biotech Performance Festival, a theatrical perspective on technology;

– A community lecture series highlighting CNSE’s education, research, and economic impact; and

– The aforementioned stylings of UAlbany prof. Robert Brainard and professional musician John Chmaj, to illustrate similarities in composing jazz music and nanotech research — for instance, "looking at theme and variation to wavelengths and working in groups," notes the Albany Times Union.

The "Nanovember" programs are part of an educational collaboration between UAlbany and KeyBank dubbed "NEXSTEP" to "promote greater understanding of the changing economic and business environment in the Capital Region and New York State being driven by nanotechnology," the school says.

October 16, 2009 – Researchers led by a team at Arizona State U. have created a single-molecule diode that could pave the way to creation of new chemical sensors, and ultimately capabilities that complement and extend those in silicon-based electronic devices.

Diodes enable electrical current to flow in one direction around a circuit but not another — they’re critical and ubiquitous components in various electronics applications including power conversion, logic gates, photodetectors, and LEDs. A molecule with this capability needs to be asymmetric, with its ends forming covalent bonds with the anode (negative) and cathode (positive) contacts.

Work on using molecule-based components has been ongoing for decades, but most of it has focused on groups of molecules (e.g., molecular thin films). Challenges include bridging a single molecule to at least two electrodes, and in proper orientation of the molecule in the device, the researchers note.

The group, led by ASU’s N.J. Tao with participation from scientists at the U. of Chicago and U. of South Florida, came up with a technique relying on AC modulation, applying "a little periodically varying mechanical perturbation to the molecule" to tell if there’s a molecule bridged across two electrodes. They used conjugated molecules incorporating alternating single and multiple bonds, which display large electrical conductivity and have asymmetrical ends that can spontaneously form the needed covalent bonds with metal electrodes, they note.

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Schematic for molecular diode. The symmetric molecule (top) allows for two-way current. The asymmetrical molecule (bottom) permits current in one direction only and acts as a single-molecule diode. (Source: ASU Biodesign Institute)

From the abstract of their paper, published in Nature Chemistry:

The diblock molecule exhibits pronounced rectification behaviour compared with its homologous symmetric block, with current flowing from the dipyrimidinyl to the diphenyl moieties. This behaviour is interpreted in terms of localization of the wave function of the hole ground state at one end of the diblock under the applied field. At large forward current, the molecular diode becomes unstable and quantum point contacts between the electrodes form.

Application for a single-molecule diode includes new chemical sensors; eventually they could offer electronic, mechanical, optical, and other properties that complement silicon-based technologies, Tao noted.

October 14, 2009 – SVTC’s efforts to offer more leading-edge MEMS technology for its customers now finds it more formally aligned in a new partnership with the world’s biggest semiconductor foundry.

Under a new alliance, SVTC and TSMC will work with developers to support new products from concept to volume production and commercialization, centering on technologies for applications in "emerging markets" — e.g., MEMS, biochips, and other devices with new materials and structures — "whose ideas or products are based on silicon technologies, but may not necessarily scale with Moore’s Law," noted Joseph Bronson, SVTC CEO, in a statement. "There are a number of promising applications that could inspire entire new industries, but many lack a clear path to commercialization and high-volume manufacturing," and the new ties to TSMC will help "the world’s most promising innovators to develop new products and to bring the best of these new devices into volume production."

Development and early commercialization work on "conceptual or undeveloped" products will be done at SVTC; as demand increases, the processes will be transferred over to TSMC for volume manufacturing, with both firms co-marketing unspecified services.

SVTC and TSMC have been partners going back to a "technology incubation program" announced shortly after SVTC was spun out of Cypress Semiconductor in 2007, fulfilling one of SVTC’s first goals of developing closer ties with foundries as a type of referral service. SVTC now offers a "Fast-Transfer" process to help improve yields for products transferred to TSMC.

In 2008 SVTC started offering 200mm MEMS development, in a bid to leverage synergies with integrating MEMS and logic technology (i.e. base CMOS). There’s a learning curve in such a migration with many tool advances and changed processes to be accounted for, as Scott Marquardt, VP of sales, marketing, and strategic business development, told Small Times: "You can’t just take what you’re doing in 6-inch and send a diagram off to TSMC and say, ‘Please make me 10 million of these.’"

by Steve Liker, business manager, Trident Solar

In the battle for the business of price-sensitive consumers, highly efficient photovoltaic production at reduced processing costs is key to survival. One approach that can generate significant cost savings and greater production efficiencies is use of digital inkjet printing.

Inkjet printing of contacts and bus bars has several key benefits over alternative technologies. The ability to print narrow features with small drop volume and high resolution makes it possible to minimize shadowing on the active layer. Inkjet printing can be used to dispense etchants to controllably produce undercuts or features in PV layers. This high-resolution, direct-write printing method also saves in process steps, speeds set-up time, eliminates waste, reduces cost through automation, and enables non-contact printing for thin, sensitive substrates.

Inkjet printing brings several key advantages to photovoltaic production processes. Lines or holes (50μm × 5-10μm) can be produced without the damage and defects associated with lasers. Digital printing is non-contact so breakage and resulting scrap are eliminated. In addition, inkjet can be used to jet conductive metal inks (such as silver ink) to digitally produce contact lines with thickness down to 50μm, 2×-3× finer than can be produced with silver paste, a squeegee, and screen printing — and at one-fifth the cost. This allows manufacturers to print exactly the amount of material they need exactly where they need it, saving significant time, expense, and waste. It also enhances efficiency, as contact widths can be minimized to ensure that valuable sunlight is not blocked.

Choosing the right inkjet printing system can give companies an important edge in a competitive marketplace. Not all printing systems are created equally. In order to evaluate the quality of an inkjet printing system, take a look under the hood, at the printhead. The printhead is the heart of most inkjet printing systems and its characteristics often determine the cost effectiveness and quality of the inkjet printer. Durability, print quality, and cost-effectiveness are three key elements to look for in an inkjet printhead.

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Figure 1. The printhead is the heart of most inkjet printing systems and its characteristics often determine the cost effectiveness and quality of the inkjet printer. For inkjet printing of etchants for photovoltaic cell production, an inkjet printhead with stainless steel construction can last up to eight times longer than a similar printhead of less inert material construction.

Durability

Inkjet printing systems must be ruggedly designed to work alongside the hustle and bustle of employee and machine activity in a production environment. When producing photovoltaic contacts, very aggressive and potentially damaging materials such as acids, alkaline etchants, and conductive materials are jetted from the inkjet printhead. It is essential that an inkjet printing system be highly inert and robustly designed to provide consistent quality performance even when routinely exposed to extremely challenging materials.

Printheads typically feature orifice plates made of either metallic substances like stainless steel, or polyimide plastic films; each material provides different benefits to end-users. Plastic orifice plates are typically less expensive to produce, while stainless steel orifice plates offer greater scratch resistance, greater inertness, and increased durability.

There are other important questions to be asked about durability before purchasing an inkjet printing system:

— On average how long does the printing system run without requiring service or repair?

— Can the inkjet printhead be repaired or is it a disposable consumable?

— How many years will the printhead last before it needs to be replaced?

Carefully selecting a durable printing system for the most difficult industrial environments and the most aggressive materials can prevent costly production delays and save money on inkjet printhead components. For inkjet printing of etchants for photovoltaic cell production, an inkjet printhead with stainless steel construction can last up to eight times longer than a similar printhead of less inert material construction.

Print quality/resolution

Another key factor to consider when selecting an inkjet printing system is print resolution – typically determined by the minimum drop volume capability. Precision printing of materials is important to produce the typical high tolerance features. When printing solar cell contacts it is necessary to minimize contact widths so that light is not blocked. High-resolution inkjet printing produces the narrowest possible contacts.

Cost

A third important element to study when selecting an inkjet printing system is cost. Three factors are particularly important in cost-effective printing systems: cost-per-system, jettable material cost, and printhead life/repairability.

Depending on the printable area and number of fluids dispensed, a number of inkjet printheads may be required in the manufacturing process. Fluid controls, printhead drivers and other printer system components contribute to the overall capital cost of the system.

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Figure 2. Trident’s new 256Jet-S inkjet printhead featuring a rugged, serviceable design is inert to corrosive etchant materials, offers an industry-leading lifespan and can print conductive metal contacts up to 3× higher resolution than possible with screen printing.

In addition to being very aggressive, the jettable materials used in inkjet printing photovoltaic contacts are often expensive. Inkjet printing is an additive process, so it allows manufacturers to print exactly the amount of material they need exactly where they need it, saving significant time and expense vs. subtractive printing methods that waste valuable printing materials.

Another important factor to look for when searching for a cost-effective inkjet printing system is printhead life/reparability. When the orifice plate becomes clogged with debris, does the entire printhead need to be replaced or can it simply be repaired? A printhead with a repairable design that allows the front chamber and orifice plate to be removed, cleaned, and reassembled can save money on costly product replacements.

Conclusion

Finding the right inkjet printing system is key to enhancing PV production efficiency and identifying cost-saving opportunities. Taking the time to understand the technology within printing systems — especially durability, print-quality, and flexibility — is time well-invested to find the printer that is right for a particular operation.

Steve Liker is business manager at Trident Industrial Inkjet, Brookfield, CT USA; e-mail [email protected].

October 9, 2009 – IMEC’s annual IMEC’s annual Technology Forum this week featured three announcements targeting medical devices: a low-power MEMS actuator for in-vivo biomedical applications, a microfluidics device for faster cancer detection and therapy, and a new wireless EEG system for ambulatory monitoring.

"Inchworm" actuator for in-vivo biomed

An ultralow-power, watertight actuator newly developed by IMEC targets applications requiring long autonomy with small batteries, and is "especially suited" for in-vivo biomedical applications such as brain implants, the R&D consortium says.

The new silicon-on-insulator (SOI)-fabricated device is an "electrostatic inchworm actuator" that converts energy into micromovements — by moving in concert, four arms that selectively latch/unlatch and two for driving can achieve a bidirectional step-like movement. The device has a range of ±50μm and can generate sufficient force (±195μN) to position, for example, in-vivo brain electrodes, with 3× lower operating voltage (11V) than current actuators, and it also consumes just <100nW of power. The device has been integrated with a microneedle encapsulated in a flip-chip package with a glass cap and hydrophobic surface treatment (i.e. it’s watertight).

 

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Figure 1. Schematic (top) and micrograph (bottom) of IMEC’s inchworm actuator, with six pull-in actuators (four for latching and two for driving). By proper latching, unlatching, and driving the shuttle, the actuator can drive a bidirectional step-like movement. (Source: IMEC)

Micro-actuators are already used in medical applications requiring microscopic-scale control of biological objects or environments — e.g. for microsurgery tools, pumps, and needles. One application is to integrate the actuators with microprobes for brain applications, for accurately controlling the position of microneedles, so as to reach and get near the correct groups of neurons for a specific disorder to obtain the best signal/noise ratio. These would be true "implants" in the sense of the word; today’s "implants" using actuators for brain research are actually placed outside the body.

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Figure 2. Schematic (left) and actual photo (right) of the actuator, encapsulated with a micro-needle in a watertight package. (Source: IMEC)


Lab-on-chip targets breast cancer

Under the European Union’s MASCOT ("Multiple-access space-time coding testbed") project which pursues "novel techniques" for multiple user/input/output wireless systems, IMEC and partners have put together a modular platform with autonomous modules which can be used for different medical applications — in this case, detection and therapy evaluation of breast cancer.

This particular device — the first to include many complex sample preparation steps and multiplexed detection, according to IMEC — includes one module for mixing blood samples with magnetic beads that bind to tumor cells, and another module to isolate and count those cells using dielectrophoresis and magnetic sensing. In the third "amplification" module the tumor cells are destroyed and the genetic material extracted using multiplex ligation dependent probe amplification. Specific assays amplify ~20 markers associated with breast carcinoma cells, which are detected using an array of electrochemical sensors.

Having a multifunction lab-on-a-chip device would solve timeliness and cost issues associated with cancer detection, IMEC explains. In the case of breast cancer, only 2-3 tumor cells are found in 5ml of blood; many sample preprocessing steps in different medical instruments are required to make full analysis. A lab-on-a-chip system incorporating the above-described functions would vastly simplify this process, which could be performed in a doctor’s office or near a patient’s bedside.

The system has been validated on "spiked blood samples" and modules are ready for "further hetero-integration into a single lab-on-chip," IMEC notes. Next is to clinically validate it in a breast cancer therapy study in Oslo.

Wireless EEG

IMEC and research affiliate Holst Center have developed a miniaturized wireless EEG system for remote monitoring of patients in their daily environment; the result is seen to be more natural readings and more comfortable patients.

The system incorporates an eight-channel ultralow-power analog readout ASIC, with other electronics including radio and controller integrated onto a 47×27mm printed circuit board, packaged in a "small box" with status LEDs, a switch button, and interfaces for din32 cables. The whole thing requires only 1.8mA of power, meaning about three days of operation on one 160mAh lithium ion battery.

The system can connect to individual electrodes, recording high-quality signals via gel electrodes (R&D on dry electrodes is still ongoing), standard EEG monitoring hats, or other proprietary EEG headsets. Data is wirelessly transmitted in real-time to a receiver up to 10m away. IMEC also has developed algorithms to interpret the brain signals, "linking the brain activity to the degree of relaxation," the group said in a statement.

The new wireless EEG is part of an art expo, dubbed "Staalhemel" ("Steel sky"), at the center STK in Leuven, Belgium, in which visitors wearing a headset with IMEC’s EEG system walk past 80 steel plates suspended above; the brainwaves activate tiny hammers to tap rhythmic patterns on the plates.

October 7, 2009 – Researchers at French R&D institute Leti say they have overcome incompatibilities of metallic catalysts with CMOS manufacturing in order to make silicon nanowires, bridging a gap between CMOS technology and bottom-up growth of nanowires and enabling new functionality to be added to chipmaking processes.

Semiconductor nanowires’ high surface-to-volume ratio makes them excellent candidates for sensors (electrical detection of chemical/biological substances) and solar energy production, and their small mass is valuable for mechanical mass detection. They also have potential for adding functions such as sensing and energy production on top of ICs. A roadblock to their use in IC production, though, has been the issue of CMOS compatibiltiy — many metallic catalysts used for nanowire growth aren’t compatible with standard CMOS fabrication processes, and those metals that are compatible (e.g., aluminum and copper) require temperatures above the maximum allowed temperature (450ºC). Researchers, assuming that oxidized metals are unsuitable for nanowire synthesis, have tried to remove the oxides.

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Figure 1. Silicon nanowires obtained by the new method. (Source: Leti)

In a paper published by Nature Nanotechnology, Leti says it turned to the "unconventional preparation method" of oxidizing a copper catalyst precursor, and using the reaction’s high chemical activity to help reduce the nanowire synthesis temperature to as low as 400ºC — allowing the growth of silicon nanowires with CMOS-compatible catalyst and temperatures. The work can be performed on standard deposition tools, noted Vincent Jousseaume, co-author of the paper, in an e-mail exchange with Small Times.

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Figure 2. Image taken of a tomographic 3D reconstruction illustrating the morphology of the tip of a nanowire (~70nm dia.) after oxidation. Silicon-containing regions appear in blue; copper-rich regions appear in red. (Source: Leti)

What’s the forseen application of synthesized nanowires in IC manufacturing? "There will be first the possibility of introducing logic in the interconnect layers," in principle allowing fabrication of vertical transistors in vias, a step toward reconfigurable interconnect, according Jousseaume. There is also the promise of adding functionality beyond ICs, sucha s chemical or bio sensors to mechanical nano-actuators and embedded solar cells to provide power directly to the circuits, he said.

The next step in the work is to demonstrate applications for the technology, and optimizing the nanowire growth — e.g., better controlling the nanowire orientation with respect to the substrate, Jousseaume said.

October 6, 2009 – Houston, TX-based rock physics firm Ingrain is using an analytical tool from Carl Zeiss to generate ultrahigh-resolution images and analytical capabilities to explore shale rock properties and potential for extracting oil and gas from it.

The Zeiss tool being used, an Auriga CrossBeam FIB-SEM workstation, generates high-resolution 3D images to build the company’s "vRock," a digital capture of a rock sample’s structure, to obtain more detailed and more accurate properties analysis, according to company CEO Henrique Tono. Very thin slices (down to 5nm) of rock are removed by the FIB; the SEM creates high-res 3D images of the structure to reveal and distinguish between voids and minerals. The tool’s charge compensation system allows local application of an inert gas flush, which can neutralize charge buildup on nonconductive samples (like shale rock) and enable detection of secondary and backscattered electrons.

"Our customers, who are world leaders in oil and gas exploration, can now get more detailed, more accurate rock properties analyses. In essence, we are now able to provide more accurate, more complete information to support their decision making needs," stated Tono.

Mapping a quantum dot


October 5, 2009

October 5, 2009 – Researchers from the U. of Michigan have come up with the first atomic-scale maps of quantum dots, seen as a first step to producing and tailoring them for specific applications.

Their work, published online in the journal Nature Nanotechnology, derived sub-ånström resolution maps of quantum dots — clusters of atoms (10-50nm wide) that form semiconducting crystals — crystallized from indium droplets exposed to antimony and the interface with a GaAs (100) substrate. The dots were illuminated with a brilliant X-ray photon beam at Argonne National Laboratory’s Advanced Photon Source. The research was sponsored by a grant from the National Science Foundation; the US Department of Energy supported the work at Argonne.

From the paper abstract:

We find that the QDs form coherently and extend a few unit cells below the substrate surface. This facilitates a droplet–substrate exchange of atoms, resulting in core–shell structures that contain a surprisingly small amount of [indium].

The new maps will push forward the general understanding of quantum dots’ structure and chemical makeup, a first step in figuring out how to control their properties and behavior via directed assembly, according to Roy Clarke, U-M professor of physics and corresponding author of the paper, who likens this quantum-dot-charting work to discovering a new continent. "Initially all you see is the vague outline of something through the mist. Then you land on it and go into the interior and really map it out, square inch by square inch," he said. Similarly, "this is the first time that anybody has been able to map [quantum dots] at the atomic level, to go in and see where the atoms are positioned, as well as their chemical composition. It’s a very significant breakthrough."

Already used for lasers and sensors, quantum dots could be helped along by this work into applications such as quantum computing.

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Atomic-scale map of the interface between an atomic dot and its substrate, sliced through a vertical cross-section of the dot. Each peak represents a single atom. (Source: U. of Michigan)