Tag Archives: letter-pulse-tech

Corning Incorporated (NYSE: GLW) today introduced its latest breakthrough in glass substrates for the semiconductor industry – Advanced Packaging Carriers. This enhanced line of glass carrier wafers is optimized for fan-out processes, a type of cutting-edge semiconductor packaging that enables smaller, faster chips for consumer electronics, automobiles, and other connected devices.

Corning Advanced Packaging Carriers feature three significant improvements:

– Fine granularity in a wide range of available coefficients of thermal expansion (CTE)
– High stiffness composition
– Rapid sampling availability

These attributes are important for customers pursuing fan-out packaging because:

– Fine granularity enables customers to more easily select the optimal CTE needed to minimize in-process warp. Precise CTE offerings thereby help reduce customers’ development cycle time.
– Corning’s high stiffness compositions help further reduce in-process warp. Minimizing warp helps maximize their yield of packaged chips.
– Rapid sampling availability also contributes to reduced development time and enables customers to move to the mass production phase more quickly.

“We created Corning Advanced Packaging Carriers especially for our customers pursuing the most challenging types of chip manufacturing processes,” said Rustom Desai, commercial director of Corning Precision Glass Solutions.

“Our deep technical ties in the semiconductor industry, combined with Corning’s core competencies in glass science and manufacturing, enabled us to create an innovative product that can help customers maximize efficiency throughout their development process and mass production ramp,” Desai said.

Corning’s semiconductor glass carriers are one of several products in Corning’s portfolio of Precision Glass Solutions designed to address the emerging need for glass across microelectronics. This portfolio provides customers with a one-stop shop for world-class capabilities including proprietary glass and ceramic manufacturing platforms, finishing processes, bonding technologies, best-in-class metrology, automated laser glass-processing, and optical design expertise.

The absorption of light in semiconductor crystals without inversion symmetry can generate electric currents. Researchers at the Max Born Institute have now generated directed currents at terahertz (THz) frequencies, much higher than the clock rates of current electronics. They show that electronic charge transfer between neighboring atoms in the crystal lattice represents the underlying mechanism.

Solar cells convert the energy of light into an electric direct current (DC) which is fed into an electric supply grid. Key steps are the separation of charges after light absorption and their transport to the contacts of the device. The electric currents are carried by negative (electrons) and positive charge carriers (holes) performing so called intraband motions in various electronic bands of the semiconductor. From a physics point of view, the following questions are essential: what is the smallest unit in a crystal which can provide a photo-induced direct current (DC)? Up to which maximum frequency can one generate such currents? Which mechanisms at the atomic scale are responsible for such charge transport?

(a) Unit cell of the semiconductor gallium arsenide (GaAs). Chemical bonds (blue) connect every Ga atom to four neighboring As atoms and vice versa. Valence electron density in the grey plane of (a) in the (b) ground state (the electrons are in the valence band) and in the (c) excited state (electrons are in the conduction band). Apart from the valence electrons shown, there are tightly bound electrons near the nuclei. Credit: MBI Berlin

The smallest unit of a crystal is the so-called unit cell, a well-defined arrangement of atoms determined by chemical bonds. The unit cell of the prototype semiconductor GaAs is shown in Figure 1a and represents an arrangement of Ga and As atoms without a center of inversion. In the ground state of the crystal represented by the electronic valence band, the valence electrons are concentrated on the bonds between the Ga and the As atoms (Figure 1b). Upon absorption of near-infrared or visible light, an electron is promoted from the valence band to the next higher band, the conduction band. In the new state, the electron charge is shifted towards the Ga atoms (Figure 1b). This charge transfer corresponds to a local electric current, the interband or shift current, which is fundamentally different from the electron motions in intraband currents. Until recently, there has been a controversial debate among theoreticians whether the experimentally observed photo-induced currents are due to intraband or interband motions.

Researchers at the Max Born Institute in Berlin, Germany, have investigated optically induced shift currents in the semiconductor gallium arsenide (GaAs) for the first time on ultrafast time scales down to 50 femtoseconds (1 fs = 10 to the power of -15 seconds). They report their results in the current issue of the journal Physical Review Letters 121, 266602 (2018) . Using ultrashort, intense light pulses from the near infrared (λ = 900 nm) to the visible (λ = 650 nm, orange color), they generated shift currents in GaAs which oscillate and, thus, emit terahertz radiation with a bandwidth up to 20 THz (Figure 2). The properties of these currents and the underlying electron motions are fully reflected in the emitted THz waves which are detected in amplitude and phase. The THz radiation shows that the ultrashort current bursts of rectified light contain frequencies which are 5000 times higher than the highest clock rate of modern computer technology.

The properties of the observed shift currents definitely exclude an intraband motion of electrons or holes. In contrast, model calculations based on the interband transfer of electrons in a pseudo-potential band structure reproduce the experimental results and show that a real-space transfer of electrons over the distance on the order of a bond length represents the key mechanism. This process is operative within each unit cell of the crystal, i.e., on a sub-nanometer length scale, and causes the rectification of the optical field. The effect can be exploited at even higher frequencies, offering novel interesting applications in high frequency electronics.

LED lights and monitors, and quality solar panels were born of a revolution in semiconductors that efficiently convert energy to light or vice versa. Now, next-generation semiconducting materials are on the horizon, and in a new study, researchers have uncovered eccentric physics behind their potential to transform lighting technology and photovoltaics yet again.

Comparing the quantum properties of these emerging so-called hybrid semiconductors with those of their established predecessors is about like comparing the Bolshoi Ballet to jumping jacks. Twirling troupes of quantum particles undulate through the emerging materials, creating, with ease, highly desirable optoelectronic (light-electronic) properties, according to a team of physical chemists led by researchers at the Georgia Institute of Technology.

Laser light in the visible range is processed for use in the testing of quantum properties in materials in Carlos Silva’s lab at Georgia Tech. Credit: Georgia Tech / Rob Felt

These same properties are impractical to achieve in established semiconductors.

The particles moving through these new materials also engage the material itself in the quantum action, akin to dancers enticing the floor to dance with them. The researchers were able to measure patterns in the material caused by the dancing and relate them to the emerging material’s quantum properties and to energy introduced into the material.

These insights could help engineers work productively with the new class of semiconductors.

Unusually flexible semiconductors

The emerging material’s ability to house diverse, eccentric quantum particle movements, analogous to the dancers, is directly related to its unusual flexibility on a molecular level, analogous to the dancefloor that joins in the dances. By contrast, established semiconductors have rigid, straight-laced molecular structures that leave the dancing to quantum particles.

The class of hybrid semiconductors the researchers examined is called halide organic-inorganic perovskite (HOIP), which will be explained in more detail at bottom along with the “hybrid” semiconductor designation, which combines a crystal lattice — common in semiconductors — with a layer of innovatively flexing material.

Beyond their promise of unique radiance and energy-efficiency, HOIPs are easy to produce and apply.

Paint them on

“One compelling advantage is that HOIPs are made using low temperatures and processed in solution,” said Carlos Silva, a professor in Georgia Tech’s School of Chemistry and Biochemistry. “It takes much less energy to make them, and you can make big batches.” Silva co-led the study alongside Ajay Ram Srimath Kandada from Georgia Tech and the Istituto Italiano di Tecnologia.

It takes high temperatures to make most semiconductors in small quantities, and they are rigid to apply to surfaces, but HOIPs could be painted on to make LEDs, lasers or even window glass that could glow in any color from aquamarine to fuchsia. Lighting with HOIPs may require very little energy, and solar panel makers could boost photovoltaics’ efficiency and slash production costs.

The team led by Georgia Tech included researchers from the Université de Mons in Belgium and the Istituto Italiano di Tecnologia. The results were published on January 14, 2019, in the journal Nature Materials. The work was funded by the U.S. National Science Foundation, EU Horizon 2020, the Natural Sciences and Engineering Research Council of Canada, the Fond Québécois pour la Recherche, and the Belgian Federal Science Policy Office.

Quantum jumping jacks

Semiconductors in optoelectronic devices can either convert light into electricity or electricity into light. The researchers concentrated on processes connected to the latter: light emission.

The trick to getting a material to emit light is, broadly speaking, to apply energy to electrons in the material, so that they take a quantum leap up from their orbits around atoms then emit that energy as light when they hop back down to the orbits they had vacated. Established semiconductors can trap electrons in areas of the material that strictly limit the electrons’ range of motion then apply energy to those areas to make electrons do quantum leaps in unison to emit useful light when they hop back down in unison.

“These are quantum wells, two-dimensional parts of the material that confine these quantum properties to create these particular light emission properties,” Silva said.

Imaginary particle excitement

There is a potentially more attractive way to produce the light, and it is a core strength of the new hybrid semiconductors.

An electron has a negative charge, and an orbit it vacates after having been excited by energy is a positive charge called an electron hole. The electron and the hole can gyrate around each other forming a kind of imaginary particle, or quasiparticle, called an exciton.

“The positive-negative attraction in an exciton is called binding energy, and it’s a very high-energy phenomenon, which makes it great for light emitting,” Silva said.

When the electron and the hole reunite, that releases the binding energy to make light. But usually, excitons are very hard to maintain in a semiconductor.

“The excitonic properties in conventional semiconductors are only stable at extremely cold temperatures,” Silva said. “But in HOIPs the excitonic properties are very stable at room temperature.”

Ornate quasiparticle twirling

Excitons get freed up from their atoms and move around the material. In addition, excitons in an HOIP can whirl around other excitons, forming quasiparticles called biexcitons. And there’s more.

Excitons also spin around atoms in the material lattice. Much the way an electron and an electron hole create an exciton, this twirl of the exciton around an atomic nucleus gives rise to yet another quasiparticle called a polaron. All that action can result in excitons transitioning to polarons back. One can even speak of some excitons taking on a “polaronic” nuance.

Compounding all those dynamics is the fact that HOIPs are full of positively and negatively charged ions. The ornateness of these quantum dances has an overarching effect on the material itself.

Wave patterns resonate

The uncommon participation of atoms of the material in these dances with electrons, excitons, biexcitons and polarons creates repetitive nanoscale indentations in the material that are observable as wave patterns and that shift and flux with the amount of energy added to the material.

“In a ground state, these wave patterns would look a certain way, but with added energy, the excitons do things differently. That changes the wave patterns, and that’s what we measure,” Silva said. “The key observation in the study is that the wave pattern varies with different types of excitons (exciton, biexciton, polaronic/less polaronic).”

The indentations also grip the excitons, slowing their mobility through the material, and all these ornate dynamics may affect the quality of light emission.

Rubber band sandwich

The material, a halide organic-inorganic perovskite, is a sandwich of two inorganic crystal lattice layers with some organic material in between them – making HOIPs an organic-inorganic hybrid material. The quantum action happens in the crystal lattices.

The organic layer in between is like a sheet of rubber bands that makes the crystal lattices into a wobbly but stable dancefloor. Also, HOIPs are put together with many non-covalent bonds, making the material soft.

Individual units of the crystal take a form called perovskite, which is a very even diamond shape, with a metal in the center and halogens such as chlorine or iodine at the points, thus “halide.” For this study, the researchers used a 2D prototype with the formula (PEA)2PbI4.

Light is the most energy-efficient way of moving information. Yet, light shows one big limitation: it is difficult to store. As a matter of fact, data centers rely primarily on magnetic hard drives. However, in these hard drives, information is transferred at an energy cost that is nowadays exploding. Researchers of the Institute of Photonic Integration of the Eindhoven University of Technology (TU/e) have developed a ‘hybrid technology’ which shows the advantages of both light and magnetic hard drives. Ultra-short (femtosecond) light pulses allows data to be directly written in a magnetic memory in a fast and highly energy-efficient way. Moreover, as soon as the information is written (and stored), it moves forward leaving space to empty memory domains to be filled in with new data. This research, published in Nature Communications, promises to revolutionize the process of data storage in future photonic integrated circuits.

Data are stored in hard drives in the form of ‘bits’, tiny magnetic domains with a North and a South pole. The direction of these poles (‘magnetization’), determines whether the bits contain a digital 0 or a 1. Writing the data is achieved by ‘switching’ the direction of the magnetization of the associated bits.

Synthetic ferrimagnets

Conventionally, the switching occurs when an external magnetic field is applied, which would force the direction of the poles either up (1) or down (0). Alternatively, switching can be achieved via the application of a short (femtosecond) laser pulse, which is called all-optical switching, and results in a more efficient and much faster storage of data.

Mark Lalieu, PhD candidate at the Applied Physics Department of TU/e: ‘All-optical switching for data storage has been known for about a decade. When all-optical switching was first observed in ferromagnetic materials – amongst the most promising materials for magnetic memory devices – this research field gained a great boost’. However, the switching of the magnetization in these materials requires multiple laser pulses and, thus, long data writing times.

Storing data a thousand times faster

Lalieu, under the guidance of Reinoud Lavrijsen and Bert Koopmans, was able to achieve all-optical switching in synthetic ferrimagnets – a material system highly suitable for spintronic data applications – using single femtosecond laser pulses, thus exploiting the high velocity of data writing and reduced energy consumption.

So how does all-optical switching compare to modern magnetic storage technologies? Lalieu: “The switching of the magnetization direction using the single-pulse all-optical switching is in the order of picoseconds, which is about a 100 to 1000 times faster than what is possible with today’s technology. Moreover, as the optical information is stored in magnetic bits without the need of energy-costly electronics, it holds enormous potential for future use in photonic integrated circuits.”

‘On-the-fly’ data writing

In addition, Lalieu integrated all-optical switching with the so-called racetrack memory – a magnetic wire through which the data, in the form of magnetic bits, is efficiently transported using an electrical current. In this system, magnetic bits are continuously written using light, and immediately transported along the wire by the electrical current, leaving space to empty magnetic bits and, thus, new data to be stored.

Koopmans: “This ‘on the fly’ copying of information between light and magnetic racetracks, without any intermediate electronic steps, is like jumping out of a moving high-speed train to another one. From a ‘photonic Thalys’ to a ‘magnetic ICE’, without any intermediate stops. You will understand the enormous increase in speed and reduction in energy consumption that can be achieved in this way”.

What’s next? This research was performed on micrometric wires. In the future, smaller devices in the nanometer scale should be designed for better integration on chips. In addition, working towards the final integration of the photonic memory device, the Physics of Nanostructure group is currently also busy with the investigation on the read-out of the (magnetic) data, which can be done all-optically as well.

Researchers from Chalmers University of Technology, Sweden, have discovered a simple new tweak that could double the efficiency of organic electronics. OLED-displays, plastic-based solar cells and bioelectronics are just some of the technologies that could benefit from their new discovery, which deals with “double-doped” polymers.

Double doping could improve the light-harvesting efficiency of flexible organic solar cells (left), the switching speed of electronic paper (center) and the power density of piezoelectric textiles (right). Disclaimer: The image may only be used with referral to Epishine, as supplier of the flexible solar cell. For instance: ‘The solar cell was supplied by Epishine AB.’ Credit: Johan Bodell/Chalmers University of Technology

The majority of our everyday electronics are based on inorganic semiconductors, such as silicon. Crucial to their function is a process called doping, which involves weaving impurities into the semiconductor to enhance its electrical conductivity. It is this that allows various components in solar cells and LED screens to work.

For organic – that is, carbon-based – semiconductors, this doping process is similarly of extreme importance. Since the discovery of electrically conducting plastics and polymers, a field for which a Nobel Prize was awarded in 2000, research and development of organic electronics has accelerated quickly. OLED-displays are one example which are already on the market, for example in the latest generation of smartphones. Other applications have not yet been fully realised, due in part to the fact that organic semiconductors have so far not been efficient enough.

Doping in organic semiconductors operates through what is known as a redox reaction. This means that a dopant molecule receives an electron from the semiconductor, increasing the electrical conductivity of the semiconductor. The more dopant molecules that the semiconductor can react with, the higher the conductivity – at least up to a certain limit, after which the conductivity decreases. Currently, the efficiency limit of doped organic semiconductors has been determined by the fact that the dopant molecules have only been able to exchange one electron each.

But now, in an article in the scientific journal Nature Materials, Professor Christian Müller and his group, together with colleagues from seven other universities demonstrate that it is possible to move two electrons to every dopant molecule.

“Through this ‘double doping’ process, the semiconductor can therefore become twice as effective,” says David Kiefer, PhD student in the group and first author of the article.

According to Christian Müller, this innovation is not built on some great technical achievement. Instead, it is simply a case of seeing what others have not seen.

“The whole research field has been totally focused on studying materials which only allow one redox reaction per molecule. We chose to look at a different type of polymer, with lower ionisation energy. We saw that this material allowed the transfer of two electrons to the dopant molecule. It is actually very simple,” says Christian Müller, Professor of Polymer Science at Chalmers University of Technology.

The discovery could allow further improvements to technologies which today are not competitive enough to make it to market. One problem is that polymers simply do not conduct current well enough, and so making the doping techniques more effective has long been a focus for achieving better polymer-based electronics. Now, this doubling of the conductivity of polymers, while using only the same amount of dopant material, over the same surface area as before, could represent the tipping point needed to allow several emerging technologies to be commercialised.

“With OLED displays, the development has come far enough that they are already on the market. But for other technologies to succeed and make it to market something extra is needed. With organic solar cells, for example, or electronic circuits built of organic material, we need the ability to dope certain components to the same extent as silicon-based electronics. Our approach is a step in the right direction,” says Christian Müller.

The discovery offers fundamental knowledge and could help thousands of researchers to achieve advances in flexible electronics, bioelectronics and thermoelectricity. Christian Müller’s research group themselves are researching several different applied areas, with polymer technology at the centre. Among other things, his group is looking into the development of electrically conducting textiles and organic solar cells.

By Emmy Yi

SEMI Taiwan Testing Committee founded to strengthen the last line of defense to ensure the reliability of advanced semiconductor applications.

Mobile, high-performance computing (HPC), automotive, and IoT – the four future growth drivers of semiconductor industry, plus the additional boost from artificial intelligence (AI) and 5G – will spur exponential demand for multi-function and high-performance chips. Today, a 3D IC semiconductor structure is beginning to integrate multiple chips to extend functionality and performance, making heterogeneous integration an irreversible trend.

As the number of chips integrated in a single package increases, the structural complexity also rises. Not only will this make identifying chip defects harder, but the compatibility and interconnection between components will also introduce uncertainties that can undermine the reliability of the final ICs. Add to these challenges the need for tight cost control and a faster time to market, and it’s clear that semiconductor testing requires disruptive, innovative change. Traditional final-product testing focusing on finished components is now giving way to wafer- and system-level testing.

In addition, the traditional notion of design for testing, an approach that enhances testing controllability and observability, is now coupled with the imperative to test for design, which emphasizes drawing analytics insights from collected test data to help reduce design errors and shorten development cycles. Going forward, the relationship among design, manufacturing, packaging, and testing will no longer be un-directional. Instead, it will be a cycle of continuous improvement.

This paradigm shift in semiconductor testing, however, will also create a need for new industry standards and regulations, elevate visibility and security levels for shared data, require the optimization of testing time and costs, and lead to a shortage of testing professionals. Solving all these issues will require a joint effort by the industry and academia.

“With leading technologies and $4.7 billion in market value, Taiwan still holds the top spot in global semiconductor testing market,” said Terry Tsao, President of SEMI Taiwan. “When testing extends beyond the manufacturing process, it can play a critical role in ensuring quality throughout the entire life cycle from design and manufacturing to system integration while maintaining effective controls on development costs and schedules. Taiwan’s semiconductor industry is in dire need of a common testing platform to enable the cross-disciplinary collaboration necessary for technical breakthroughs.”

The new SEMI Taiwan Testing Committee was formed to meet that need, gathering testing experts and academics from MediaTek, Intel, NXP Semiconductors, TSMC, UMC, ASE Technology, SPIL, KYEC, Teradyne, Advantest, FormFactor, MJC, Synopsys, Cadence, Mentor, and National Tsing Hua University to collaborate in building a complete testing ecosystem. The committee addresses common technical challenges faced by the industry and cultivates next-generation testing professionals to enable Taiwan to maintain its global leadership in semiconductor testing.

The SEMI Taiwan Testing Platform spans communities, expositions, programs, events, networking, business matching, advocacy, and market and technology insights. For more information about the SEMI Taiwan Testing platform, please contact Elaine Lee ([email protected]) or Ana Li ([email protected]).

Emmy Yi is a marketing specialist at SEMI Taiwan.  

This story originally appeared on the SEMI blog.

Intentionally “squashing” colloidal quantum dots during chemical synthesis creates dots capable of stable, “blink-free” light emission that is fully comparable with the light produced by dots made with more complex processes. The squashed dots emit spectrally narrow light with a highly stable intensity and a non-fluctuating emission energy. New research at Los Alamos National Laboratory suggests that the strained colloidal quantum dots represent a viable alternative to presently employed nanoscale light sources, and they deserve exploration as single-particle, nanoscale light sources for optical “quantum” circuits, ultrasensitive sensors, and medical diagnostics.

“In addition to exhibiting greatly improved performance over traditional produced quantum dots, these new strained dots could offer unprecedented flexibility in manipulating their emission color, in combination with the unusually narrow, ‘subthermal’ linewidth,” said Victor Klimov, lead Los Alamos researcher on the project. “The squashed dots also show compatibility with virtually any substrate or embedding medium as well as various chemical and biological environments.”

The new colloidal processing techniques allow for preparation of virtually ideal quantum-dot emitters with nearly 100 percent emission quantum yields shown for a wide range of visible, infrared and ultraviolet wavelengths. These advances have been exploited in a variety of light-emission technologies, resulting in successful commercialization of quantum-dot displays and TV sets.

The next frontier is exploration of colloidal quantum dots as single-particle, nanoscale light sources. Such future “single-dot” technologies would require particles with highly stable, nonfluctuating spectral characteristics. Recently, there has been considerable progress in eliminating random variations in emission intensity by protecting a small emitting core with an especially thick outer layer. However, these thick-shell structures still exhibit strong fluctuations in emission spectra.

In a new publication in the journal Nature Materials, Los Alamos researchers demonstrated that spectral fluctuations in single-dot emission can be nearly completely suppressed by applying a new method of “strain engineering.” The key in this approach is to combine in a core/shell motif two semiconductors with directionally asymmetric lattice mismatch, which results in anisotropic compression of the emitting core.

This modifies the structures of electronic states of a quantum dot and thereby its light emitting properties. One implication of these changes is the realization of the regime of local charge neutrality of the emitting “exciton” state, which greatly reduces its coupling to lattice vibrations and fluctuating electrostatic environment, key to suppressing fluctuations in the emitted spectrum. An additional benefit of the modified electronic structures is dramatic narrowing of the emission linewidth, which becomes smaller than the room-temperature thermal energy.

For the first time, researchers used benzene – a common hydrocarbon – to create a novel kind of molecular nanotube, which could lead to new nanocarbon-based semiconductor applications.

Researchers from the Department of Chemistry have been hard at work in their recently renovated lab in the University of Tokyo’s Graduate School of Science. The pristine environment and smart layout affords them ample opportunities for exciting experiments. Professor Hiroyuki Isobe and colleagues share an appreciation for “beautiful” molecular structures and created something that is not only beautiful but is also a first for chemistry.

Their phenine nanotube (pNT) is beautiful to see for its pleasing symmetry and simplicity, which is a stark contrast to its complex means of coming into being. Chemical synthesis of nanotubes is notoriously difficult and challenging, even more so if you wish to delicately control the structures in question to provide unique properties and functions.

Typical carbon nanotubes are famous for their perfect graphite structures without defects, but they vary widely in length and diameter. Isobe and his team wanted a single type of nanotube, a novel form with controlled defects within its nanometer-sized cylindrical structure allowing for additional molecules to add properties and functions.

The researchers’ novel process of synthesis starts with benzene, a hexagonal ring of six carbon atoms. They use reactions to combine six of these benzenes to make a larger hexagonal ring called a cyclo-meta-phenylene (CMP). Platinum atoms are then used which allow four CMPs to form an open-ended cube. When the platinum is removed, the cube springs into a thick circle and this is furnished with bridging molecules on both ends enabling the tube shape.

It sounds complicated, but amazingly, this complex process successfully bonds the benzenes in the right way over 90 percent of the time. The key also lies in the symmetry of the molecule, which simplifies the process to assemble as many as 40 benzenes. These benzenes, also called phenines, are used as panels to form the nanometer-sized cylinder. The result is a novel nanotube structure with intentional periodic defects. Theoretical investigations show these defects imbue the nanotube with semiconductor characters.

“A crystal of pNT is also interesting: The pNT molecules are aligned and packed in a lattice rich with pores and voids,” Isobe explains. “These nanopores can encapsulate various substances which imbue the pNT crystal with properties useful in electronic applications. One molecule we successfully embedded into pNT was a large carbon molecule called fullerene (C70).”

“A team lead by Kroto/Curl/Smalley discovered fullerenes in 1985. It is said that Sir Harold Kroto fell in love with the beautiful molecule,” continues Isobe. “We feel the same way about pNT. We were shocked to see the molecular structure from crystallographic analysis. A perfect cylindrical structure with fourfold symmetry emerges from our chemical synthesis.”

“After a few decades since the discovery, this beautiful molecule, fullerene, has found various utilities and applications,” adds Isobe. “We hope that the beauty of our molecule is also pointing to unique properties and useful functions waiting to be discovered.”

When German mineralogist Gustav Rose stood on the slopes of Russia’s Ural Mountains in 1839 and picked up a piece of a previously undiscovered mineral, he had never heard of transistors or diodes or had any concept of how conventional electronics would become an integral part of our daily lives. He couldn’t have anticipated that the rock he held in his hand, which he named “perovskite,” could be a key to revolutionizing electronics as we know them.

In 2017, University of Utah physicist Valy Vardeny called perovskite a “miracle material” for an emerging field of next-generation electronics, called spintronics, and he’s standing by that assertion. In a paper published today in Nature Communications, Vardeny, along with Jingying Wang, Dali Sun (now at North Carolina State University) and colleagues present two devices built using perovskite to demonstrate the material’s potential in spintronic systems. Its properties, Vardeny says, bring the dream of a spintronic transistor one step closer to reality.

The full study can be found here.

Spintronics

A conventional digital electronic system conveys a binary signal (think 1s and 0s) through pulses of electrons carried through a conductive wire. Spintronics can convey additional information via another characteristic of electrons, their spin direction (think up or down). Spin is related to magnetism. So spintronics uses magnetism to align electrons of a certain spin, or “inject” spin into a system.

If you’ve ever done the old science experiment of turning a nail into a magnet by repeatedly dragging a magnet along its length, then you’ve already dabbled in spintronics. The magnet transfers information to the nail. The trick is then transporting and manipulating that information, which requires devices and materials with finely tuned properties. Researchers are working toward the milestone of a spin transistor, a spintronics version of the electronic components found in practically all modern electronics. Such a device requires a semiconductor material in which a magnetic field can easily manipulate the direction of electrons’ spin–a property called spin-orbit coupling. It’s not easy to build such a transistor, Wang says. “We keep searching for new materials to see if they’re more suitable for this purpose.”

Here’s where perovskites come into play.

Perovskites

Perovskites are a class of mineral with a particular atomic structure. Their value as a technological material has only became apparent in the past 10 years. Because of that atomic structure, researchers have been developing perovskite into a material for making solar panels. By 2018 they’d achieved an efficiency of up to 23 percent of solar energy converted to electrical energy–a big step up from 3.8 percent in 2009.

In the meantime, Vardeny and his colleagues were exploring the possibilities of spintronics and the various materials that could prove effective in transmitting spin. Because of heavy lead atoms in perovskite, physicists predicted that the mineral may possess strong spin-orbit coupling. In a 2017 paper, Vardeny and physics assistant professor Sarah Li showed that a class of perovskites called organic-inorganic hybrid perovskites do indeed possess large spin-orbit coupling. Also, the lifetime of spin injected into the hybrid materials lasted a relatively long time. Both results suggested that this kind of hybrid perovskite held promise as a spintronics material.

Two spintronic devices

The next step, which Vardeny and Wang accomplished in their recent work, was to incorporate hybrid perovskite into spintronic devices. The first device is a spintronic light-emitting diode, or LED. The semiconductor in a traditional LED contains electrons and holes–places in atoms where electrons should be, but aren’t. When electrons flow through the diode, they fill the holes and emit light.

Wang says that a spintronic LED works much the same way, but with a magnetic electrode, and with electron holes polarized to accommodate electrons of a certain spin.  The LED lit up with circularly polarized electroluminescence, Wang says, showing that the magnetic electrode successfully transferred spin-polarized electrons into the material.

“It’s not self-evident that if you put a semiconductor and a ferromagnet together you get a spin injection,” Vardeny adds. “You have to prove it. And they proved it.”

The second device is a spin valve. Similar devices already exist and are used in devices such as computer hard drives. In a spin valve, an external magnetic field flips the polarity of magnetic materials in the valve between an open, low-resistance state and a closed, high-resistance state.

Wang and Vardeny’s spin valve does more. With hybrid perovskite as the device material, the researchers can inject spin into the device and then cause the spin to precess, or wobble, within the device using magnetic manipulation.

That’s a big deal, the researchers say. “You can develop spintronics that are not only useful for recording information and data storage, but also calculation,” Wang says. “That was an initial goal for the people who started the field of spintronics, and that’s what we are still working on.”

Taken together, these experiments show that perovskite works as a spintronic semiconductor. The ultimate goal of a spin-based transistor is still several steps away, but this study lays important groundwork for the path ahead.

“What we’ve done is to prove that what people thought was possible with perovskite actually happens,” Vardeny says. “That’s a big step.”

Rudolph Technologies, Inc. (NYSE: RTEC) announced today that it has received orders for 12 of its Dragonfly™ G2 system, just months after releasing the product. Several systems were delivered in the fourth quarter to the largest OSAT where the Dragonfly G2 systems displaced incumbent 3D technology and retained the Company’s market leadership in 2D macro inspection. The remaining systems will ship in the first half of 2019 to OSAT, IDM, and Foundry customers who are adopting the Dragonfly G2 platform for its high productivity in two-dimensional (2D) inspection, and its accuracy and repeatability in three-dimensional (3D) inspection of the smallest copper pillars. The Company expects additional adoptions of the Dragonfly G2 system across multiple key market segments in the first half of 2019, which validates Rudolph’s collaborative R&D approach with its key customers.

The new Dragonfly G2 platform delivers up to 150% improvement in productivity over legacy systems as well as exceeds competitive system throughputs. Its modular architecture provides a flexible platform with plug-and-play configurability to combine 2D with 3D Truebump™ Technology for accurate copper pillar/bump height measurements. Clearfind™ Technology detects non-visual residue defects and advanced sensor technology measures 3D features and CD metrology. Additionally, the Dragonfly G2 platform has been specifically architected to allow the measurement, data collection, and analysis of bump interconnects nearing 100 million bumps per wafer using Rudolph’s Discover® software and advanced computing architecture.

“We are pleased that our leading-edge customers across multiple market segments are quickly recognizing the value of the Dragonfly G2 system,” said Michael Plisinski, chief executive officer at Rudolph. “Today’s interconnects for advanced memory are now at or below five microns, which require higher accuracy and repeatability versus standard copper pillar bumps. With approximately 65 wafer-level packages in today’s high-end smartphones, a single weak interconnect or reliability failure can result in a high cost of return, driving our customers’ need for the enhanced process control performance. Defect sensitivity, resolution, and productivity are combined in the Dragonfly G2 system to deliver a capability and cost of ownership that is unparalleled in the competitive space.”