N1005 IBM Research: Nature

IBM scientists use the STM to image molecules in liquid

<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://farm6.staticflickr.com/5558/15030498715_07a6f97660_n.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="200" src="https://farm6.staticflickr.com/5558/15030498715_07a6f97660_n.jpg" width="183" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Nirmalraj in the Noise Free Lab</td></tr></tbody></table>Since the first microscope was invented, researchers and scientists around the world have searched for new ways to stretch their understanding of the microscopic world. In 1981, two IBM researchers, Gerd Binnig and Heinrich Rohrer, broke new ground in the science of the very, very small with their invention of the scanning tunneling microscope (STM). Like no instrument before it, Binnig and Rohrer’s invention enabled scientists to visualize the world all the way down to its molecules and atoms. The STM was recognized with the Nobel Prize in Physics in 1986 and is widely regarded as the instrument that opened the door to nanotechnology and a wide range of explorations in fields as diverse as electrochemistry, semiconductor science, and molecular biology. <a name="more"></a> In a new paper appearing today titled "<a href="http://www.nature.com/srep/2015/150511/srep10116/full/srep10116.html">Capturing the embryonic stages of self-assembly - design rules for molecular computation</a>" in <a href="http://www.nature.com/srep/2015/150511/srep10116/full/srep10116.html" target="_blank">Nature Scientific Reports</a>, IBM scientists in Zurich are adding a new chapter to the STM's legacy by reporting on a new methodology for the reliable extraction of incredibly high resolution images of the swarming behavior of molecules in situ or which translates to "on site". I spoke with the lead author of the paper <a href="http://researcher.ibm.com/researcher/view.php?person=zurich-PNI">Dr. Peter Nirmalraj</a> about his research and what's next. <div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIoUvr2UVXCrjEOIMRs1nsUKp7lRLt7DzuTPx2EYM5fUOeHF-iryKpqWlsNLuqV6XcIL-xBOcyLbwc4YiDsxRA4A9wf5SqMTOQy_z8kPPmabF4TOucltptDf3GdNuePyXiKlZaZd2ZON0/s1600/Table+of+contents+graphic.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIoUvr2UVXCrjEOIMRs1nsUKp7lRLt7DzuTPx2EYM5fUOeHF-iryKpqWlsNLuqV6XcIL-xBOcyLbwc4YiDsxRA4A9wf5SqMTOQy_z8kPPmabF4TOucltptDf3GdNuePyXiKlZaZd2ZON0/s320/Table+of+contents+graphic.jpg" width="208" /></a></div> Q. Why has it taken so long to use the STM for in situ imaging in liquid?  Peter Nirmalraj (PN): In situ STM imaging (imaging in liquids at room-temperature) has been around for the last 20 years, however extracting high resolution data comparable to UHV STM standards has remained a challenge, mainly due to the electrochemical congestion and external noise interference occurring when performing such measurements in liquids at room temperature. Q. How did you come up with the idea to make it work? PN: We have <a href="http://www.nature.com/nmat/journal/v13/n10/full/nmat4060.html">previously demonstrated</a> how to control molecular motion for stable electrical readouts.  In the current work we employ the same STM tool capable of measuring dynamics of individual molecules at the liquid-solid interface, with excellent spatio-temporal sensitivity. In particular we chose electrically inert and low vapor pressure liquids as the medium, that does not interfere with the tunneling mechanism. The entire setup is located within our state-of-the-art noise free laboratories located in the <a href="http://www.zurich.ibm.com/nanocenter/">Binnig and Rohrer Nanotechnology Center</a> which immensely aids such nanoscopic measurements in liquids. The question we asked ourselves, can we record in real-time the evolution of an organic molecular layer and in particular capture the very early-stages of self-assembly rather than only imaging a fully packed thermodynamically stable molecular matrix?  <div class="separator" style="clear: both; text-align: center;"></div><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPF3EXRkC8Jmqpaxa2GTg_Gn0TeOJxfODtkx-8I5wPveOBvYmbsIT4DRl3e6l3a-Bnq78e5VhEPTR7mPT5JYo6gbjeabECIrc7nGLI4lLv14IAjW_vhzBb8lna6B2mFIUqCqwzlkwtkvk/s1600/STM.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="195" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPF3EXRkC8Jmqpaxa2GTg_Gn0TeOJxfODtkx-8I5wPveOBvYmbsIT4DRl3e6l3a-Bnq78e5VhEPTR7mPT5JYo6gbjeabECIrc7nGLI4lLv14IAjW_vhzBb8lna6B2mFIUqCqwzlkwtkvk/s200/STM.jpg" width="200" /></a>Information obtained from such carefully designed experiments can and have provided deeper insights on the fundamentals of molecular self assembly, which is central in molecular computation and in refining step-by-step equilibration rules for agent-based algorithms (algorithmic self-assembly). Q. Why did you choose C60 molecules for the molecular solution? PN: Fullerenes are a well studied class of molecules. This makes it easier to calibrate our STM tool as the dimensions and intermolecular packing arrangements of this system is known from both theory and previous STM studies. More importantly fullerenes are compatible with our solvent of choice, n-tetradecane and form a stable molecular solution (molecules are well dispersed with minimal treatment and does not aggregate in solution). Currently we are exploring other molecules with different dimensions from porphyrins to ferrocene. Q. Could this technique be used for healthcare, to image bacteria and and viruses for example? PN: Yes, biomolecules which are generally not highly rigid and less conductive in nature can be imaged using STM when drop casted from a liquid-phase onto conductive metal surfaces. However, the solvents that generally support biomolecules are polar which necessitates an additional step for insulating the STM probe, minus the apex, to minimize parasitic currents during tunneling. Such measurements also need to be performed under closed-liquid cells with larger volume to contain rapid solvent evaporation. Q. What's next for your research? PN: The next step would be to investigate naturally occurring pattern formation and understand better the local structural dynamics of organic molecules such as porphyrins as they evolve from a disordered phase to an energetically stable stage and verify their internal response to external electrical pulses.  Large data sets generated from such studies will then be directed towards constructing predictive algorithms for assembly of new 2D and 3D molecular configurations and for testing basic logic gate operations in molecular layers. Follow the authors on Twitter at <a href="https://twitter.com/stm_pnn">@stm_pnn</a> and <a href="https://twitter.com/HeikeRiel">@HeikeRiel </a> This research is partly funded by the Marie Curie Actions-Intra-European Fellowship (IEF-PHY) under grant agreement N° 275074 “To Come” within the 7th European Community Framework Programme.

nano Nature STM IBM scientists use the STM to image molecules in liquid

Nirmalraj in the Noise Free Lab Since the first microscope was invented, researchers and scientists around the world have searched for new ...

40+ Year Old Challenge Solved for Phase Change Materials

<a href="https://en.wikipedia.org/wiki/Phase-change_material">Phase change materials</a>, were first considered for storing data in the 1970s, where the two metastable states or phases of these materials, are used to store data in the form of millions of lines of binary code made of up billions of 0s and 1s.  The concept eventually reached the consumer market, and today the most common use of these materials is in optical storage, where the phase transition is induced by heating the material with a laser beam - this is how a Blue-ray disk stores a video. <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://farm9.staticflickr.com/8022/7562150148_79d2b3d2ec_m.jpg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="https://farm9.staticflickr.com/8022/7562150148_79d2b3d2ec_m.jpg" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The cross-sectional tunneling electron microscopy (TEM) image of a mushroom-type PCM cell is shown in this photo.</td></tr></tbody></table>In addition to a laser, it is also possible to heat the phase change material through electrical means by placing it between two electrically conducting electrodes. This forms the basis for a novel concept called <a href="http://www.research.ibm.com/labs/zurich/sto/pcm/">phase-change memory</a>(PCM), a nonvolatile memory technology that promises to bridge the performance gap between the main memory and storage electronics, spaning from mobile phones to cloud data centers. The nanometric volume of phase change material in the PCM cell can be reversible switched from the amorphous phase (logic “0”) and the crystalline phase (logic “1”) by the application of suitable voltage pulses. The resulting data can be read out by applying a much lower read voltage. But for more than 40 years scientists have never measured the temperature dependence of crystal growth, due to the difficulties associated with the measurements which are taken at both a nanometer length and a nanosecond time scale. That was until earlier this year when, for the first time, IBM scientists in Zurich were able to take the measurements, which is today being reported in the peer-review journal <a href="http://www.nature.com/ncomms/2014/140707/ncomms5314/full/ncomms5314.html">Nature Communications</a>. On the eve of the publication of this important result, the authors answered a few questions from their lab in the <a href="http://www.zurich.ibm.com/nanocenter/">Binnig and Rohrer Nanotechnology Center</a> at IBM. <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/AVvXsEjLa7zfglb4cS12SuM2vNlTCu26ZZNiKohmem4n96x0p-AH-qcmsVOiCwFge1soWubTgW5JgDIuBu7uI3j8t4LNZE8L6jiKMP32xmiweeHr45Ez0ncPkGhM-2AE3a-gDMUchMRUZExEsI_n/s1600/PCMteam.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="265" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLa7zfglb4cS12SuM2vNlTCu26ZZNiKohmem4n96x0p-AH-qcmsVOiCwFge1soWubTgW5JgDIuBu7uI3j8t4LNZE8L6jiKMP32xmiweeHr45Ez0ncPkGhM-2AE3a-gDMUchMRUZExEsI_n/s1600/PCMteam.jpg" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">IBM scientists Abu Sebastian, Manuel Le Gallo and Daniel Krebs</td></tr></tbody></table> Let’s start with the obvious decades old question, what is the temperature corresponding to maximum crystal growth? <a href="http://researcher.watson.ibm.com/researcher/view.php?person=zurich-DKR" target="_blank">Daniel Krebs:</a> The optimum crystal growth temperature is 477 degrees Celcius (750 Kelvin), but that it really just one point on the chart (<a href="https://www.flickr.com/gp/ibm_research_zurich/39a0W8">figure B</a>) – holistically it gets much more interesting.  What is more useful to scientists studying phase change materials is that we were able to model the entire growth velocity curve in addition to this maximum. Prior to this paper, scientists knew some of the points, but not across such a wide temperature and time scale. It is also worth noting that we took these measurements within the cell. Typically, experiments took place outside the cell, which then had to be extrapolated. Now scientists have an excellent reference point. Can you describe the eureka moment? <a href="http://researcher.watson.ibm.com/researcher/view.php?person=zurich-ASE" target="_blank">Abu Sebastian</a>: Let me start by saying that these phase change materials are very fascinating and possess unconventional crystallization kinetics. Just by changing the temperature by a few hundred degrees, you change the crystal growth rate by 17 orders of magnitude (that is beyond a trillion). This is why it  has been so difficult to probe experimentally. Only in the last 18-24 months have scientists begun to probe the crystallization rate within a reasonable temperature range, until this point the measurements were at very low temperatures (close to room temperature). Our key insight was in exploiting the nanoscale dimensions and the fast thermal dynamics of the phase change memory cell to expand the temperature range all the way up to the point at which the material melts – more than 600 degrees Celsius. Daniel: It’s called the time-temperature dilemma. At room temperature you want stability of the material to retain the data for at least 10 years, but when you want to write to the material it needs to crystallize in nanoseconds. And that is what makes this material so interesting, but it’s also what makes it challenging – particularly in how it can be accurately measured. Manuel Le Gallo: I came to IBM to do my Masters thesis work on electrical transport in phase change materials. One of the requirements was to achieve the same amorphous volume at all temperatures. This involved a deeper understanding of melting and crystallization in the PCM cells. As we delved more into the subject, the focus of the thesis gradually shifted, culminating in the fascinating results we present in the paper. What inherent challenges in phase change memory does this achievement address and what are the potential applications? Daniel: If we break down the challenges of PCM into read and write operations, in this work, we are addressing the write operation. Our measurements will help devise ways to write data faster and with better retention.   Abu: In the context of PCM, this research will help us in estimating how fast we can write, how much power is required and what the real retention time is. Going beyond memory, yet another emerging application of phase change materials is in neuromorphic engineering,  creating chips based on the biological architectures of the nervous system. So understanding the phase change mechanism is critically important for a number of applications. Manuel: Crystal growth and subsequent change in electrical conductance has the potential to emulate the biophysics of neurons and synapses. This will also form part of my doctoral thesis work which I am currently pursuing jointly with the Institute of Neuroinformatics at ETH Zurich. What will you study next? Abu: It will be interesting to look at different materials and compare the temperature dependence of crystal growth. We also discovered that the crystal growth rate reduces over time, which we want to expand on further. Daniel: The reduction in growth over time is actually very interesting for me. In the amorphous phase the materials are a glass. Like a glass window becomes thicker when it is at rest over a long period of time, like 100 years, also our amorphous material will change. In fact, it changes in such a way that it becomes more viscous. This viscosity is one of the characteristics which determines how fast the material can crystalize. Therefore it effects the write operation. It cannot crystallize as fast anymore, which is a good thing for data retention. On the other hand the glassy nature also causes the inherent problem of resistance drift in phase change memory. <div class="MsoNormal"> </div>

IBM Research - Zurich Nature PCM phase change memory 40+ Year Old Challenge Solved for Phase Change Materials

Phase change materials , were first considered for storing data in the 1970s, where the two metastable states or phases of these materials, ...