N1005 IBM Research: nanodevices

IBM Scientists Invent a Thermometer for the Nanoscale

The IBM lab responsible for inventing the scanning tunneling microscope and the atomic force microscope has invented another critical tool for helping us understand the nanoworld. Accurately measuring the temperature of objects at the <a href="https://en.wikipedia.org/wiki/Nanoscopic_scale" target="_blank">nanoscale</a> has been challenging scientists for decades. Current techniques are not accurate and they typically generate artifacts, limiting their reliability. Motivated by this challenge and their need to precisely characterize the temperature of new transistor designs <a href="https://www-03.ibm.com/press/us/en/pressrelease/44357.wss" target="_blank">to meet the demand of future cognitive computers</a>, scientists in Switzerland from IBM and ETH Zurich have invented a breakthrough technique to measure the temperature of nano- and macro-sized objects. The patent-pending invention is being disclosed for the first time today in the peer-review journal <a href="http://www.nature.com/ncomms/2016/160303/ncomms10874/full/ncomms10874.html" style="font-size: 12pt;" target="_blank">Nature Communications</a>, "Temperature mapping of operating nanoscale devices by scanning probe thermometry (doi:10.1038/ncomms10874)" <div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0cm; mso-layout-grid-align: none; tab-stops: 28.0pt 56.0pt 84.0pt 112.0pt 140.0pt 168.0pt 196.0pt 224.0pt 252.0pt 280.0pt 308.0pt 336.0pt; text-autospace: none;"> <iframe allowfullscreen="" frameborder="0" height="315" src="https://www.youtube.com/embed/7yjL_TDP_Ss" width="560"></iframe> <a name="more"></a><o:p></o:p></div><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0cm; mso-layout-grid-align: none; tab-stops: 28.0pt 56.0pt 84.0pt 112.0pt 140.0pt 168.0pt 196.0pt 224.0pt 252.0pt 280.0pt 308.0pt 336.0pt; text-autospace: none;"> </div> A History of Invention In the 1980s, IBM scientists Gerd Binnig and the late Heinrich Rohrer wanted to directly explore a surface’s electronic structure and imperfections. The instrument they needed to take such measurements didn’t exist, yet. So they did what any good scientist would do: they invented one. It became known as the <a href="http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/microscope/" target="_blank">scanning tunneling microscope</a> (STM), opening the door to nanotechnology. Just a few years later, the invention was recognized with the highest of honors, the Nobel Prize for Physics in 1986. More than 30 years later IBM scientists continue to follow in the footsteps of Binnig and Rohrer and with their latest invention. Dr. <a href="http://researcher.watson.ibm.com/researcher/view.php?person=zurich-FAM" target="_blank">Fabian Menges</a>, an IBM postdoc and co-inventor of the technique said, “We started back in 2010 and simply never gave up. Previous research was focused on a nanoscale thermometer, but we should have been inventing a thermometer for the nanoscale — an important distinction. This adjustment led us to develop a technique which combines local thermal sensing with the measuring capability of a microscope — we call it <a href="http://e-collection.library.ethz.ch/eserv/eth:47862/eth-47862-02.pdf" target="_blank">scanning probe thermometry</a>.” <div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0cm; mso-layout-grid-align: none; tab-stops: 28.0pt 56.0pt 84.0pt 112.0pt 140.0pt 168.0pt 196.0pt 224.0pt 252.0pt 280.0pt 308.0pt 336.0pt; text-autospace: none;"> </div><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody><tr><td style="text-align: center;"><a href="https://c2.staticflickr.com/2/1609/24533887792_d18d4d3576_z.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="213" src="https://c2.staticflickr.com/2/1609/24533887792_d18d4d3576_z.jpg" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">IBM scientist Fabian Menges with his invention.</td></tr></tbody></table><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0cm; mso-layout-grid-align: none; tab-stops: 28.0pt 56.0pt 84.0pt 112.0pt 140.0pt 168.0pt 196.0pt 224.0pt 252.0pt 280.0pt 308.0pt 336.0pt; text-autospace: none;"> How it Works: A Scanning Probe Thermometry The most common technique to measure temperature on the macroscale is to bring a thermometer into thermal contact with the sample. This is how a fever thermometer works. Once it’s placed under our tongue it equilibrates to our body temperature so that we can determine our temperature at a healthy 37 degrees C. Unfortunately, it gets a little more challenging when using a thermometer to measure a nanoscopic object. For example, it would be impossible to use a typical thermometer to measure the temperature of an individual virus. The size of the virus is too small and the thermometer cannot equilibrate without significantly disturbing the virus temperature.  To solve this challenge, IBM scientists developed a single scan non-equilibrium contact thermometry technique to measure the temperature of nanoscopic objects using a scanning probe. As the scanning probe thermometer and the object cannot thermally equilibrate at the nanoscale, two signals are measured simultaneously: a small heat flux, and its resistance to heat flow. Combining these two signal the temperature of nanoscopic objects can then be quantified for an accurate result. IBM scientist Dr. <a href="http://researcher.watson.ibm.com/researcher/view.php?person=zurich-bgo" target="_blank">Bernd Gotsmann</a> and co-inventor explains, “The technique is analogous to touching a hot plate and inferring its temperature from sensing the heat flux between our own body and the heat source. Essentially, the tip of the probe is our the hand. Our perception to hot and cold can be very helpful to get an idea of an objects temperature, but it can also be misleading if the resistance to heat flow is unknown.” Previously, scientists weren’t accurately including this resistance dependence; but only measuring the rate of the thermal energy transfer through the surface, know as heat flux. In the paper, the authors included the effects of local variations of thermal resistance to measure the temperature of an indium arsenide (InAs) nanowire, and a self-heated gold interconnect with a combination of a few-miliKelvin and few-nanometer spatial resolution. </div><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody><tr><td style="text-align: center;"><a href="https://c2.staticflickr.com/2/1587/24346717690_49899b720d_z.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="212" src="https://c2.staticflickr.com/2/1587/24346717690_49899b720d_z.jpg" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">From left to right, IBM scientists Nico Mosso, Bernd Gotsmann, Fabian Motzfeld and Fabian Menges in the Noise Free Lab with the scanning probe thermometer.</td></tr></tbody></table>Menges adds, "Not only is the scanning probe thermometer accurate, it meets the trifecta for tools: it's easy to operate, simple to build, and very versatile, in that it can be used to measure the temperature of nano- and micro-sized hot spots that can locally effect the physical properties of materials or govern chemical reactions in devices such as transistors, memory cells, thermoelectric energy converters or plasmonic structures. The applications are endless.”  Noise Free Labs It’s no coincidence that the team began to see improvements in the development of the scanning probe thermometer 18 months ago when they moved their research into the new Noise Free Labs -- six meters underground at the <a href="http://www.research.ibm.com/labs/zurich/brnc.html" target="_blank">Binnig and Rohrer Nanotechnology Center</a>on the campus of IBM Research-Zurich. This unique environment, which shields the experiments from vibration, acoustic noise, electromagnetic signals and temperature fluctuations, helped the team achieve sub-milliKelvin precision. “While we had the benefit of this unique room, the technique can also produce reliable results in normal environment,” said Menges. Next Steps  “We hope the paper will produce both a lot of excitement and relief for scientists, who like us, have been searching for such a tool,” said Gotsmann. “Similar to the STM, we hope to license this technique to tool manufacturers who can then bring it to market as an additional function to their microscopy product line.” The scientists would like to thank the 7th Program Framework for its support under the <a href="http://www.nanoheat-project.eu/">NANOHEAT</a> project and the Swiss National Science Foundation. <div class="MsoNormal"> </div><o:p></o:p>

The IBM lab responsible for inventing the scanning tunneling microscope and the atomic force microscope has invented another critical tool ...

Self-assembling nano… whiskers?

9:53 AM N1000 0

<div class="MsoNormal">by Dr. Frances Ross, materials scientist at IBM Research <table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody><tr><td style="text-align: center;"><a href="http://graphics8.nytimes.com/images/2009/08/31/science/01trans2_600.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="176" src="http://graphics8.nytimes.com/images/2009/08/31/science/01trans2_600.jpg" width="320" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Dr. Frances Ross at the IBM Thomas J Watson Research Center. Photo credit: Chris Ramirez for <a href="http://www.nytimes.com/2009/09/01/science/01trans.html?pagewanted=all&_r=1&" target="_blank">The New York Times</a></td></tr></tbody></table>“Whiskers” have been recorded in natural ores since the 1500s. These crystal formations indeed look like a cat’s whiskers, but function as wires. And since Bell Labs in the 1960s began to grow whiskers deliberately out of many different substances, materials scientists have been molding them into everything from photovoltaic devices, transistors, sensors, solid state lighting and batteries. At IBM Research, with colleagues from academia and the Brookhaven National Laboratory, we have developed a way to make these structures grow in an electron microscope. By recording the atoms <a href="http://spectrum.ieee.org/nanoclast/semiconductors/materials/new-selfassembly-technique-embeds-quantum-dots-into-nanowires">self-assembling</a>to form the whiskers – renamed in modern fashion as nanowires – we hope to understand how they grow and how to tune the growth conditions to build nano-devices. <a name="more"></a> The term nanowire describes any crystal that is thin in diameter, down to tens of nanometers, but with a length maybe hundreds or thousands of times greater. The material that the nanowire is made of, and its exact dimensions, determine its performance. For example, how solar energy is absorbed, in the case of photovoltaics. Or how lithium moves along a nanowire, in the case of rechargeable batteries. And how magnetic fields arrange themselves along its length, in the case of IBM’s <a href="http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/racetrack/">racetrack memory</a>. The big bang in these tiny structures comes from the fact that at nanoscale dimensions, even conventional materials can behave in remarkable and unexpected ways. One exciting opportunity for nanowires is as building blocks for transistors in microelectronics. While getting to the <a href="http://asmarterplanet.com/blog/2015/07/a-new-wave-innovation-chips.html">7 nanometer</a> node is heroic, the lithographic process conventionally used to define the circuits is ultimately limited. Using self-assembled nanowires as the cores of the transistors can provide a pathway to smaller circuits, and perhaps even new designs that need less power to perform computations. Our experiments started with the goal of understanding how the atoms spontaneously arrange themselves into the simplest sorts of nanowires, those that are made up of only one material. We chose our favorite element, silicon, the semiconductor that forms the basis of microelectronics. The nanowires grow with the help of a catalyst. So, we start with a flat wafer of silicon, add a couple of layers of gold atoms and heat until the gold and silicon react chemically and form tiny liquid droplets. The reaction takes place at 370oC, and results in something that looks a lot like a pane of glass covered by raindrops – at the nano-scale. <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWCP3D2U4GBbnA4j14-Z57h5LW_PWjWMnynMsovP1BSvCqgWGord3R4X8Pj-TERHdqIrZHdsq8whdj0_-P8B2dM0FX8MoLnHp25Eb5F9Fx2XuzPxOAOXokJPCt1yZS8sALoqzBpVPcTov7/s1600/nanowires_electron_microscope.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="243" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWCP3D2U4GBbnA4j14-Z57h5LW_PWjWMnynMsovP1BSvCqgWGord3R4X8Pj-TERHdqIrZHdsq8whdj0_-P8B2dM0FX8MoLnHp25Eb5F9Fx2XuzPxOAOXokJPCt1yZS8sALoqzBpVPcTov7/s400/nanowires_electron_microscope.jpg" width="500" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">A silicon nanowire at 5nm and 20nm.</td></tr></tbody></table>The trick is then to flow disilane gas, which contains silicon atoms, across the hot, droplet-covered silicon surface. When a molecule touches the surface of the silicon wafer, it bounces off and nothing changes. But when a molecule hits the surface of the gold droplet, it sticks and breaks apart, and its silicon atoms enter the droplet. As more silicon enters a droplet, the excess settles out as solid silicon beneath the droplet. Think of gradually adding spoonfuls of sugar to your coffee: excess sugar eventually settles at the bottom of the cup. In the case of the nanowires, the settling does not form disordered sludge, but instead a perfect layer of silicon atoms. The droplet stays at the top, and the nanowire keeps growing as long as we keep the gas flowing. The photo shows a nanowire during growth: the liquid droplet, labeled Au-Si, sits on top of the nanowire.   Watching this process in our electron microscope, and later in a microscope at Brookhaven National Laboratory with a high-speed (400 frames–per-second) movie camera, was an amazing experience. The video below shows the nanowire and the droplet, where the rows of dots indicate positions of silicon atoms in the nanowire. Layers of silicon atoms add onto the nanowire beneath the liquid droplet.</div><div class="MsoNormal"> <iframe allowfullscreen="" frameborder="0" height="360" src="https://www.youtube.com/embed/AS06F4YwvnM" width="480"></iframe> Watch how a silicon nanowire self-assembles under a gold-silicon droplet, and grows around a nanocrystal of nickel disilicide Droplet size determined the nanowire’s diameter. Temperature determined how long, and how quickly, the nanowire grew. We also tested other important semiconductors – germanium, gallium arsenide and gallium phosphide – and showed that their nanowires grew in a similar way. This finding helps us to understand how to build more complicated structures. So, we watched what happened as we switched from one gas to another, and learned the rules that govern which semiconductors could be stacked layer by layer, within a single nanowire.  Because each layer has different electronic behavior, these complicated nanowires could form versatile nano-devices. And it’s possible to grow even more complicated nanowires. Our most recent experiments show what happens when we add metals, such as nickel or cobalt, to the catalytic droplet. Instead of settling out as a flat layer, the metal forms a single nanocrystal that floats in the droplet. Eventually this nanocrystal settles out, and we can grow the nanowire around it. This sequence of events was completely unexpected to us – imagine if you add that extra spoonful of sugar to your coffee and then find a perfect cube of sugar floating in the liquid! Electron microscope videos help us understand why the atoms assemble in this way, and how to control the resulting nanowire to optimize the shape, size and position of the embedded nanocrystals. Self-assembling nanowires creates new concepts for nanomaterials, helping us build structures that cannot be fabricated using conventional techniques. The self-assembly process is still challenging because every nanowire comes out slightly different – perhaps imperfect for use in a device. We are not yet precise enough to exactly replicate the process across an entire wafer, much less build reliable nano-devices. However, each step forward, such as the nanowires with embedded nanocrystals, suggests new opportunities for electronics and other applications. Self-assembly will succeed when we can harness the spontaneous behavior of atoms. That’s an exciting prospect. We need to change our way of thinking to avoid the need for perfection, but still control how the self-assembled structures behave under certain conditions – allowing us to create wholly unique devices and capabilities. Read <a href="http://www.nature.com/nmat/journal/v14/n8/full/nmat4352.html">Synthesis of nanostructures in nanowires using sequential catalyst reactions</a> in Nature Materials.</div>

materials science nanodevices nanotechnology nanowires Nature Materials Self-assembling nano… whiskers?

by Dr. Frances Ross, materials scientist at IBM Research Dr. Frances Ross at the IBM Thomas J Watson Research Center. Photo credit: Chris Ra...