The Kynix Blog

Scientists often discover interesting things without completely understanding how they work. That has been the case with an experimental memory technology in which temperature and voltage work together to create the conditions for data storage. But precisely how was unknown. But when a Stanford team found a way to untangle the chip’s energy and heat requirements, their tentative findings revealed a pleasant surprise: The process may be more energy efficient than was previously supposed.That’s good news for next-generation mobile devices whose batteries would last longer if they were powering lower energy chips. The group that made this discovery, led by Stanford electrical engineer H.-S. Philip Wong, is presenting the paper when the IEEE International Electron Devices Meeting (IEDM) brings leading researchers to San Francisco Dec. 5.The new technology the team investigated is called resistive random-access memory, or RRAM for short. RRAM is based on a new type of semiconductor material that forms digital zeros and ones by resisting or permitting the flow of electrons.RRAM has the potential to do things that aren’t possible with silicon: for instance, being layered on top of computer transistors in new three-dimensional, high-rise chips that would be faster and more energy efficient than current electronics, which is ideal for smartphones and other mobile devices where energy efficiency is a vital feature.But while engineers can observe that RRAM does store data, they don’t know exactly how these new materials work. “We need much more precise information about the fundamental behavior of RRAM before we can hope to produce reliable devices,” Wong said. So to help engineers understand some of the unknowns, Wong’s team built a tool to measure the basic forces that make RRAM chips work.Graduate student Zizhen Jiang of the Stanford team explained the basics: RRAM materials are insulators, which normally do not allow electricity to flow, she said. But under certain circumstances, insulators can be induced to let electrons flow.Past research had shown how: Jolting RRAM materials with an electric field causes a pathway to form that permitted electron flows. This pathway is called a filament. To break the filament, researchers apply another jolt and the material becomes an insulator again. So each jolt switched the RRAM from zero to one or back, which is what makes the material useful for data storage.But electricity is not the only force at play in RRAM switching. Pumping electrons into any material raises its temperature. That’s the principle behind electric stoves. In the case of RRAM, it was the elevated temperature caused by introducing voltage that induced filaments to form or break. The question was what voltage-induced temperature was needed to cause the switching. No one knew.Before the new Stanford study researchers thought short bursts of voltage, sufficient to generate temperatures of about 1,160ºF – hot enough to melt aluminum – was the switching point. But those were estimates because there was no way to measure the heat generated by an electric jolt. “In order to begin to answer our questions, we had to decouple the effects of voltage and temperature on filament formation,” said Ziwen Wang, another graduate student on the team.Essentially, the Stanford researchers had to heat the RRAM material without using an electric field. So they put an RRAM chip on a micro thermal stage (MTS) device – a sophisticated hot plate capable of generating a wide range of temperatures inside the material.Of course the objective was not merely to heat the material, but also to measure how filaments formed. Here they took advantage of the fact that RRAM materials are insulators in their natural state. That makes them digital zeros. As soon as a filament formed electrons would flow. The digital zero would become a digital one, which the researchers could detect.Using this experimental model, the team put RRAM chips on the burner and cranked up the heat, starting at about 80ºF – roughly the temperature of a warm room – all the way up to 1,520ºF, hot enough to melt a silver coin. Heating the RRAM to various temperatures in between these extremes, the researchers measured precisely if and how RRAM switched from its native zero to a digital one.To their pleasant surprise, the researchers observed that filaments could form more efficiently at ambient temperatures between 80ºF and 260ºF, which is hotter than boiling water – contrary to prior expectation that hotter was better.If confirmed by subsequent research, this would be good news because in a working chip the switching temperature would be created by the voltage and duration of the electric jolt. Efficient switching at lower temperatures would require less electricity and make RRAM more energy efficient and extend battery life when used as the memory in mobile devices.Much work remains to be done to make RRAM memory practical but this research provides the test bed to vary conditions systematically instead of relying on hit-and-miss hunches. “Now we can use voltage and temperature as design inputs in a predictive manner and that is going to enable us to design a better memory device,” Wang said.Reference:MT16JTF51264AZ-1G6M1SDUS5EB-001GMD2202-D192  

Researchers from the Institute for Biomedical Engineering have succeeded in measuring tiny changes in strong magnetic fields. In their experiments, the scientists magnetised a water droplet inside a magnetic resonance imaging (MRI) scanner, a device that is used for medical imaging. The researchers were able to detect even the tiniest variations of the magnetic field strength within the droplet.These changes were up to a trillion times smaller than the seven tesla field strength of the MRI scanner used in the experiment. “Until now, it was possible only to measure such small variations in weak magnetic fields,” says Klaas Prüssmann, Professor of Bioimaging at ETH Zurich and the University of Zurich.An example of a weak magnetic field is that of the Earth, where the field strength is just a few dozen microtesla. For fields of this kind, highly sensitive measurement methods are already able to detect variations of about a trillionth of the field strength, says Prüssmann.“Now, we have a similarly sensitive method for strong fields of more than one tesla, such as those used, inter alia, in medical imaging.” The scientists based the sensing technique on the principle of nuclear magnetic resonance, which also serves as the basis for magnetic resonance imaging and the spectroscopic methods that biologists use to elucidate the 3D structure of molecules.However, to measure the variations, the scientists had to build a new high-precision sensor, part of which is a highly sensitive digital radio receiver. “This allowed us to reduce background noise to an extremely low level during the measurements,” says Simon Gross. Gross wrote his doctoral thesis on this topic in Prüssmann’s group and is lead author of the paper published in the journal Nature Communications.In the case of nuclear magnetic resonance, radio waves are used to excite atomic nuclei in a magnetic field. This causes the nuclei to emit weak radio waves of their own, which are measured using a radio antenna; their exact frequency indicates the strength of the magnetic field.As the scientists emphasise, it was a challenge to construct the sensor in such a way that the radio antenna did not distort the measurements. The scientists have to position it in the immediate vicinity of the water droplet, but as it is made of copper it becomes magnetised in the strong magnetic field, causing a change in the magnetic field inside the droplet.The researchers therefore came up with a trick: they cast the droplet and antenna in a specially prepared polymer; its magnetisability (magnetic susceptibility) exactly matched that of the copper antenna. In this way, the scientists were able to eliminate the detrimental influence of the antenna on the water sample.This measurement technique for very small changes in magnetic fields allows the scientists to now look into the causes of such changes. They expect their technique to find use in various areas of science, some of them in the field of medicine, although the majority of these applications are still in their infancy.“In an MRI scanner, the molecules in body tissue receive minimal magnetisation – in particular, the water molecules that are also present in blood,” explains doctoral student Gross. “The new sensor is so sensitive that we can use it to measure mechanical processes in the body; for example, the contraction of the heart with the heartbeat.”The scientists carried out an experiment in which they positioned their sensor in front of the chest of a volunteer test subject inside an MRI scanner. They were able to detect periodic changes in the magnetic field, which pulsated in time with the heartbeat.The measurement curve is reminiscent of an electrocardiogram (ECG), but unlike the latter measures a mechanical process (the contraction of the heart) rather than electrical conduction.“We are in the process of analysing and refining our magnetometer measurement technique in collaboration with cardiologists and signal processing experts,” says Prüssmann. “Ultimately, we hope that our sensor will be able to provide information on heart disease – and do so non-invasively and in real time.”The new measurement technique could also be used in the development of new contrast agents for magnetic resonance imaging: in MRI, the image contrast is based largely on how quickly a magnetised nuclear spin reverts to its equilibrium state.Experts call this process relaxation. Contrast agents influence the relaxation characteristics of nuclear spins even at low concentrations and are used to highlight certain structures in the body.In strong magnetic fields, sensitivity issues had previously restricted scientists to measurement of just two of the three spatial nuclear spin components and their relaxation.They had to rely on an indirect measurement of relaxation in the important third dimension. For the first time, the new high-precision measurement technique allows the direct measurement of all three dimensions of nuclear spin in strong magnetic fields.Direct measurement of all three nuclear spin components also paves the way for future developments in nuclear magnetic resonance (NMR) spectroscopy for applications in biological and chemical research. 

Tokyo Tech researchers demonstrate operation energy-savings in a low price silicon power transistor structure by scaling down in all three dimensions. In electronics, lower power consumption leads to operation cost savings, environmental benefits and the convenience advantages from longer running devices. While progress in energy efficiencies has been reported with alternative materials such as SiC and GaN, energy-savings in the standard inexpensive and widely used silicon devices are still keenly sought.K Tsutsui at Tokyo Institute of Technology and colleagues in Japan have now shown that by scaling down size parameters in all three dimensions their device they can achieve significant energy savings.Tsutsui and colleagues studied silicon insulated gate bipolar transistors (IGBTs), a fast-operating switch that features in a number of every day appliances. While the efficiency of IGBTs is good, reducing the ON resistance, or the voltage from collector to emitter required for saturation (Vce(sat)), could help increase the energy efficiency of these devices further.Previous investigations have highlighted that increases in the “injection enhancement (IE) effect”, which give rise to more charge carriers, leads to a reduction in Vce(sat). Although this has been achieved by reducing the mesa width in the device structure, the mesa resistance was thereby increased as well.Reducing the mesa height could help counter the increased resistance but is prone to impeding the (IE) effect. Instead the researchers reduced the mesa width, gate length, and the oxide thickness in the MOSFET to increase the IE effect and so reduce Vce(sat) from 1.70 to 1.26 V. With these alterations the researchers also used a reduced gate voltage, which has advantages for CMOS integration.They conclude, “It was experimentally confirmed for the first time that significant Vce(sat) reduction can be achieved by scaling the IGBT both in the lateral and vertical dimensions with a decrease in the gate voltage.”These are three terminal devices used as switches or rectifiers. With simple gate-drive characteristics and high-current and low-saturation-voltage capabilities they combine the benefits of two other types of transistors - metal-oxide-semiconductor field effect transistors (MOSFETs) and bipolar transistors.The researchers reduced the mesa width, gate length, and the oxide thickness in the MOSFET by a factor of 1/k, and compared devices with values of 1 and 3 for k. Because the fabrication of narrow mesas can cause problems they also reduced the trench depth by 1/k.Although this has a slightly negative effect on the IE effect, it has considerable benefits for fabrication ease and cost and the dependence of (Vce(sat)) on the trench depth was deemed to be small. The gate voltage was also decreased by a factor of 1/k, while the cell pitch was maintained at 16 μm.Reference:2SA1987C4706FJA4213RTU

A capacitive touch sensor display that provides a more intuitive interface to ease and accelerate user interactions has been developed by VCC. The LED-based CTH series capacitive touch sensor display combines graphic interactive control with colour identification to make the interface more user-friendly.Utilising sensitive capacitive touch sensing technology, the CTH series simplifies designs and offers cost savings by eliminating the need for a traditional switch.The LED display produces a high-optical clarity, and is offered with or without a wide variety of standard graphic overlays and colours. VCC can also develop custom icons to meet most any application requirement. Offered in a wide variety of colours including red, yellow, blue, pure green and white, the LED back-lit CTH series. The robust design has no moving parts, improving reliability and increasing the operational life.Featuring a through hole design, the capacitive touch sensor display is available in one standard size 15x15x11.0mm with an industry standard pitch of 0.100"."Featuring translucent icons illuminated with different coloured LEDs, the user friendly CTH series display offers superior device interaction by communicating a singular action to users such as on/off, alarm status, and more," said Sannah Vinding, Director of Product Development and Marketing at VCC. "The integrated functionality of the compact CTH series capacitive touch sensor display eliminates the need for designing-in a traditional switch. Unlike mechanical membrane switches or mechanical push buttons, capacitive touch keypads have no moving parts so there is nothing to wear out."The CTH series is used in a wide range of applications including appliances, consumer equipment, gaming devices, industrial control displays, media players, medical devices, mobile communication devices, PDAs, point of sale terminals, portable instruments, touch screen monitors and more.Reference:T141AM61STMPE1208SQTRQT1101-ISGAT42QT2100-AUR  

In an advance that helps pave the way for next-generation electronics and computing technologies—and possibly paper-thin gadgets —scientists with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) developed a way to chemically assemble transistors and circuits that are only a few atoms thick. What's more, their method yields functional structures at a scale large enough to begin thinking about real-world applications and commercial scalability. The scientists controlled the synthesis of a transistor in which narrow channels were etched onto conducting graphene, and a semiconducting material called a transition-metal dichalcogenide, or TMDC, was seeded in the blank channels. Both of these materials are single-layered crystals and atomically thin, so the two-part assembly yielded electronic structures that are essentially two-dimensional. In addition, the synthesis is able to cover an area a few centimeters long and a few millimeters wide. "This is a big step toward a scalable and repeatable way to build atomically thin electronics or pack more computing power in a smaller area," says Xiang Zhang, a senior scientist in Berkeley Lab's Materials Sciences Division who led the study. Zhang also holds the Ernest S. Kuh Endowed Chair at the University of California (UC) Berkeley and is a member of the Kavli Energy NanoSciences Institute at Berkeley. Other scientists who contributed to the research include Mervin Zhao, Yu Ye, Yang Xia, Hanyu Zhu, Siqi Wang, and Yuan Wang from UC Berkeley as well as Yimo Han and David Muller from Cornell University. Their work is part of a new wave of research aimed at keeping pace with Moore's Law, which holds that the number of transistors in an integrated circuit doubles approximately every two years. In order to keep this pace, scientists predict that integrated electronics will soon require transistors that measure less than ten nanometers in length. Transistors are electronic switches, so they need to be able to turn on and off, which is a characteristic of semiconductors. However, at the nanometer scale, silicon transistors likely won't be a good option. That's because silicon is a bulk material, and as electronics made from silicon become smaller and smaller, their performance as switches dramatically decreases, which is a major roadblock for future electronics. Researchers have looked to two-dimensional crystals that are only one molecule thick as alternative materials to keep up with Moore's Law. These crystals aren't subject to the constraints of silicon. In this vein, the Berkeley Lab scientists developed a way to seed a single-layered semiconductor, in this case the TMDC molybdenum disulfide (MoS2), into channels lithographically etched within a sheet of conducting graphene. The two atomic sheets meet to form nanometer-scale junctions that enable graphene to efficiently inject current into the MoS2. These junctions make atomically thin transistors. "This approach allows for the chemical assembly of electronic circuits, using two-dimensional materials, which show improved performance compared to using traditional metals to inject current into TMDCs," says Mervin Zhao, a lead author and Ph.D. student in Zhang's group at Berkeley Lab and UC Berkeley. Optical and electron microscopy images, and spectroscopic mapping, confirmed various aspects related to the successful formation and functionality of the two-dimensional transistors. In addition, the scientists demonstrated the applicability of the structure by assembling it into the logic circuitry of an inverter. This further underscores the technology's ability to lay the foundation for a chemically assembled atomic computer, the scientists say. "Both of these two-dimensional crystals have been synthesized in the wafer scale in a way that is compatible with current semiconductor manufacturing. By integrating our technique with other growth systems, it's possible that future computing can be done completely with atomically thin crystals," says Zhao. Reference: 2N3811 EMX2T2R DMA204020R  

Type 1 diabetes patients may one day be able to monitor their blood glucose levels and even control their insulin infusions via a transparent sensor on a contact lens, a new Oregon State University study suggests.The sensor uses a nanostructured transistor – specifically an amorphous indium gallium oxide field effect transistor, or IGZO FET – that can detect subtle glucose changes in physiological buffer solutions, such as the tear fluid in eyes.Type 1 diabetes, formerly known as juvenile diabetes, can lead to serious health complications unless glucose levels are carefully controlled. Problems can include retinopathy, blindness, neuropathy, kidney and cardiac disease.Researchers in the OSU College of Engineering say sensors they fabricated using the IGZO FET will be able to transmit real-time glucose information to a wearable pump that delivers the hormones needed to regulate blood sugar: insulin and glucagon.The sensor and pump would, in effect, act as an artificial pancreas."We have fully transparent sensors that are working," said Greg Herman, an OSU professor of chemical engineering and corresponding author on this study. "What we want to do next is fully develop the communication aspect, and we want to use the entire contact lens as real estate for sensing and communications electronics."We can integrate an array of sensors into the lens and also test for other things: stress hormones, uric acid, pressure sensing for glaucoma, and things like that. We can monitor many compounds in tears – and since the sensor is transparent, it doesn't obstruct vision; more real estate is available for sensing on the contact lens."The FET's closely packed, hexagonal, nanostructured network resulted from complimentary patterning techniques that have the potential for low-cost fabrication. Those techniques include colloidal nanolithography and electrohydrodynamic printing, or e-jet, which is somewhat like an inkjet printer that creates much finer drop sizes and works with biological materials instead of ink.The findings by postdoctoral scholar Xiaosong Du, visiting scholar Yajuan Li and,Herman were recently published online in the journal Nanoscale. The Juvenile Diabetes Research Foundation provided primary funding for the research.Google has been working on a glucose-monitoring contact lens but its version is not fully transparent."It's an amperometric sensor and you can see the chips—that means it has to be off to the side of the contact lens," Herman said. "Another issue is the signal is dependent on the size of the sensor and you can only make it so small or you won't be able to get a usable signal. With an FET sensor, you can actually make it smaller and enhance the output signal by doing this."This research builds on earlier work by Herman and other OSU engineers that developed a glucose sensor that could be wrapped around a catheter, such as one used to administer insulin from a pump."A lot of type 1 diabetics don't wear a pump," Herman said. "Many are still managing with blood droplets on glucose strips, then using self-injection. Even with the contact lens, someone could still manage their diabetes with self-injection. The sensor could communicate with your phone to warn you if your glucose was high or low."The transparent FET sensors, Herman said, might ultimately be used for cancer detection, by sensing characteristic biomarkers of cancer risk. Their high sensitivity could also measure things such as pulse rate, oxygen levels, and other aspects of health monitoring that require precise control.Reference:OP913SLBPW41NBPW20RFPD204-6C