By Patti Koning
Imaging ice only a few nanometers thick as it forms bulk ice was supposed to be impossible. A scanning tunneling microscope (STM) shouldn’t work with ice because STMs create images by relying on conducting current, which runs contrary to one of ice’s basic properties — insulation.
But no one told this to Sandia physicists Norm Bartelt and Konrad Thürmer (both 8756). Actually, everyone did, but they didn’t listen. Experience and a bit of stubbornness resulted in what Konrad describes as the “most important scientific accomplishment of my career.”
The images captured by Norm and Konrad show ice sheets growing one molecular layer at a time. These images also reveal some new truths about ice and solve a decades-old mystery about why ice grows in cubic form at very cold temperatures, as opposed to the expected hexagonal form that leads to the sixfold symmetric snowflake shape. By combining their talents and experience — Norm is the theorist and Konrad is the experimentalist — these two physicists made a discovery they hadn’t dreamed was possible.
Science always builds on past discoveries. Norm’s and Konrad’s research was inspired by Peter Feibelman’s (1130) research in water-solid interactions. In 2002, Peter achieved a major breakthrough in interpreting water-solid interactions (Jan. 25, 2002, Sandia Lab News). His research explained why an initial layer of water molecules lies flat on the precious metal ruthenium.
Peter says that Norm and Konrad’s work shows Sandia research at its best.
“A gifted experimentalist determined to solve a problem as hard — and important — as how ice grows on a metal crystal contrives to make a scanning tunneling microscope take pictures that, because ice is a good insulator, no one imagined could be taken. Then working closely with a theorist known for a deep understanding of the forces that drive film growth, he concludes that the structure of the imaged ice film is not what thermodynamics would favor, but instead reflects the growth process. So, pictures ‘impossible’ to take yielded a lesson no one had imagined,” Peter says.
Norm and Konrad published their work in a paper, “Growth of multilayer ice films and the formation of cubic ice imaged with STM,” that was published in Physical Review B in May. The paper has generated excitement in the physics world and accolades for the researchers.
“How water interacts with solids is extremely important,” says Norm. He points to the design of fuel cells and water purification systems as two areas that could benefit from new STM information. “Getting direct information is difficult, so imaging how small ice crystals grow on solid surfaces is an important advance. This is solid information that allows basic theories to be verified. This was our goal — to provide unambiguous information.”
Ice cubes or snowflakes?
The ice-growth images answer a fundamental mystery about ice: Snowflakes form in the classic six-sided symmetrical shape, but at low temperatures, ice grows in a cubic form. This phenomenon is something that has puzzled scientists for 60 years.
Norm and Konrad discovered that when an ice film is extremely thin, measuring an average of about 1 nanometer thick, the water molecules form little islands of crystalline ice. Once the thickness reaches 4 or 5 nanometers, the ice islands join together and start to form a continuous film.
In the Physical Review B paper, the researchers showed that cubic ice forms when the ice crystals merge. Because of a mismatch in the atomic step heights of the platinum substrate relative to ice, the coalescence often creates screw dislocations in the ice. Further growth occurs by water molecules attaching to the steps that spiral around screw dislocations, creating cubic ice in the process.
“In retrospect, this process might seem obvious, but it was not anticipated. The ability of microscopy to directly observe ice growth allowed us to solve this very old problem,” says Norm.
Pushing the boundaries of STM
The STM is a notoriously finicky piece of scientific equipment, and working with ice only increased the difficulty. An STM functions by positioning a narrow needle tip near the sample and then allowing a tiny electrical current to flow across the gap. As the tip of the STM is scanned across the sample surface, the voltage required to position the scanner is used to form an image of the sample.
“Typically, an STM only works if the substrate is conductive,” says Norm. “Through persistence and patience, Konrad learned that to image ice, one needs a very small current — three orders of magnitude smaller than what had previously been tried.”
It was Konrad’s intuitive decision to change the STM’s parameters, namely those for voltage and current, that made imaging ice crystals feasible. Basically, Konrad found the sweet spot where none was believed to have existed.
The STM was developed in 1981 and earned its inventors, Gerd Binnig and Heinrich Rohr, a Nobel Prize for physics in 1986. “The discovery caused a rebirth of surface science and completely changed the field, but until now, people had not been able to apply it to ice,” says Norm. “The fact that we can apply these same methods to ice is very exciting.”
STM requires artistry and intuition on the part of the scientist. Konrad jokes that he has been working with STM for his entire life (actually, it’s been 15 years).
“STM is an experiment that doesn’t always work. Because you are trying to get atomic resolution, a few atoms on the apex of the tip can completely throw off the experiment,” says Norm. “If you are not getting an image, you don’t know if your tip is bad or you are choosing the wrong parameters.”
This means that experiments have to be repeated over and over. “It’s like fishing in the dark,” says Konrad.
In fact, the two physicists never expected that they could image thick ice films; they were hoping for a few molecules. Konrad explains that even after he began imaging thicker ice films, he didn’t trust the results. Instead, he thought they were just very misleading artifacts of the measurement approach, which have fooled other scientists to the degree of publishing results based on such artifacts.
Because Konrad only expected to see films a few molecules thick, he had the STM tip set too close; it was shaving off the top of the films. “For about a month, we thought the films were not really as high as they seemed. We thought the insulating quality of ice made them appear to be higher,” he explains. “I increased the voltage, and the ice appeared to really pop out. Still, I thought it was just a really striking electronic effect.”
However, the researchers could not come up with another explanation for why the films appeared so high. Konrad then purposely grew very thick films and reversed the polarity on the STM, which resulted in an ice carving that proved the thickness was, in fact, real.
Norm and Konrad credit Peter’s work plus 10 years of basic energy science research at Sandia for laying the foundation for their breakthrough. “Sandia has been studying metal epitaxy for the last 10 years; we’ve gained a thorough understanding of the physics of the very early stages of crystal growth,” says Norm. “We’ve also developed a strong modeling capability, so we could immediately begin working with the images.”
The two Sandians are not resting on their initial success; in fact, they say they are working to build on their breakthrough. Future experiments include putting salts on an ice crystal to see how salts change the crystal’s growth and depositing molecules that react with water, such as atomic oxygen, to determine the exact point on the surface where water dissociates.
“Our ability to image these ice films opens the door to a multitude of exciting new experiments,” says Konrad. -- Patti Koning
In August 2003, approximately 50 million people in the United States and Canada were plunged into darkness as the Northeast coast’s power grid experienced a massive failure. The region’s water supply, transportation, communications, and industry were all directly affected by the power loss, and some areas suffered looting during the blackout.
While the widespread North American blackout of 2003 was the result of human error and not terrorism, it illustrates the kind of disruptions that could be caused by malicious cyberterrorists. That’s why laboratory researchers are partnering with private industry to protect America’s electrical power grid.
The rationale behind the work is that international cyberterrorism remains a highly credible threat to the US and that vulnerability to attack lies in the nation’s increased reliance on automation, information, and communications technologies.
No enemy has yet successfully attacked the US power grid control network, but if it were to happen, it could be catastrophic. North America has more than 211,000 miles of high-voltage electrical transmission lines, carrying a net summer capacity of nearly 830 gigawatts (830,000 megawatts) to the customers of 3,100 electric utilities. These utilities have become more vulnerable as they have become more dependent on open information technology standards for their grid control systems.
Ethernet, TCP/IP, and web technologies are increasingly being used to manage power transmissions through supervisory control and data acquisition (SCADA) systems, many of which were originally designed and installed before modern IT systems were adopted.
These control systems, if not adequately protected, present potential opportunities for cyberterrorists to exploit. An assault on one part of a system will almost surely affect the operation of another part and the problem could propagate across the system.
A growing concern
Cyber attacks on IT systems are becoming increasingly more common. According to one expert estimate, there were 37,000 reported penetrations of government and private systems during fiscal 2007. Others estimate the numbers are much higher depending on the measured magnitude of the attacks, acknowledging that we may not know about all penetrations.
Additionally, information disclosed by a CIA analyst in January 2008 at a conference held by the SANS Institute reported that cyber attacks have successfully disrupted power equipment in several regions outside the US.
When the blackout of 2003 affected eight US states and the province of Ontario, it did so at a cost of $4 billion to $10 billion, which illustrates the importance of anticipating, detecting, and correcting disruptions in energy distribution systems spread across the nation.
Energy security experts point out that the 2003 blackout — one of several that occurred worldwide that year — could be replicated by cyberterrorists. Any system that relies on highly automated control networks can become the target of an intentional attempt to affect the operation of the devices and communication networks required to run the nation’s power system.
Investing in cybersecurity
Without a history of cyber attacks to provide object lessons, it is difficult for utilities to justify investments in additional protective measures. While the need for standardization became evident after the 2003 blackout, it is for the most part yet to be achieved. The slow pace of cybersecurity investment is of considerable concern to DOE and other organizations dedicated to the security of critical infrastructures. One of the goals of the DOE/industry programs is to develop secured interoperability among the various protective systems now on the market, so that as the utility corporations decide to invest in them, the security technology will be ready.
At Sandia, Robert Pollock (5633) is program lead for the National SCADA Test Bed (NSTB), and Ronald Halbgewachs (5633) and Jason Stamp (6332) are analysts for the Open Process Control System Security Architecture for Interoperable Design (OPSAID) part of NSTB. The group is part of a Sandia-based team that is working with colleagues at Pacific Northwest, Idaho, Oak Ridge, and Argonne national laboratories.
The National SCADA Test Bed is charged with identifying and solving SCADA vulnerability issues, testing new and existing equipment, and developing next-generation architectures and technology advances. In accordance with the emphasis on creating interoperability between security services for different vendors/systems, the NSTB program has developed the installation of crypto-security boxes as “bumps in the wire” that protect key components of transmission lines.
The OPSAID project, which began as a Sandia Laboratory Directed Research and Development project, is part of NSTB and provides a design basis for vendors such as Schweitzer Engineering Laboratory to build security devices that can be installed in control system networks.
The addition of these devices can increase the strength of security in older systems, while providing a foundation for the development of secure process control system elements in the future. In contrast to some security solutions, the OPSAID effort is based entirely on open-source software and standardized hardware, using an open architecture. — Darrick Hurst
Leadership demands many things depending on the circumstances: strength, intelligence, persuasiveness, perseverance. High school students attending the second annual Homeland Security Workshop in Roswell this summer learned a bit about leadership and those other qualities in the week-long camp — and perhaps a lot about themselves.
John Taylor (0303), director of the program, says the objective of the workshop, held in late June at the New Mexico Military Institute (NMMI), is to enhance student leadership and complex thinking skills using homeland security and emergency response as a content vehicle.
Last year, the first conference was held over a weekend in Albuquerque. During the weekend, students shared their experiences, visited various homeland security-related projects at Sandia, and worked on problem solving.
“There was little or no formal instruction," says John.
The 2008 workshop built on the experiences students gained in programs they completed at their own schools over the past year. John says the Roswell experience provided a sequential process of learning and applying lessons, both hands-on and in-classroom. In addition, John says, “We built in opportunities to apply the lessons directly in the complex problem-solving, ethics, and tabletop exercises.”
Lori Parrott, who led the discussion on complexity in problem-solving, says, “I wanted to introduce students to the idea that complex systems problems are different than just big and hard problems.”
During the complexity workshop, students were given fact sheets on complex social and environmental issues and were asked to discuss them. Lori says the nation’s educational system, its professional rewards system, and sometimes even our political processes “all drive us to try to jump into solutions too quickly.”
“I wanted students to understand that with really complex problems, like those in homeland security,” Lori says, “it takes discipline to learn to approach the problems with the right mental framework and get the right people, representing diverse areas of expertise, engaged. And it’s vital to identify the right tools that will help you understand the dynamics of a problem before you decide on overly simplistic — and thus usually less than fully effective — solutions.”
Lori says she wanted students to walk away from this camp experience as more intelligent consumers of information about homeland security. She also says she hopes the students will understand the kind of infrastructure the country has in place to prevent or deal with problems. In addition, she says she thinks some of the students may even decide to pursue further study in homeland security-related fields.
Anita Romero, Sandia’s Emergency Public Information program manager, assisted in the emergency scenario where students took the roles of various local and state groups that would be involved in a large-scale emergency incident. Anita says the workshop’s homeland security drill is similar to those done by city officials all over the country.
“They experienced firsthand what it’s like to delve into complex problems that defy simple solution,” Anita says.
“In this day and age,” Anita adds, “it is extremely important that the public becomes aware of emergency preparedness — the sooner the better.” As a result of the workshop, she says, the participating students “are more aware of the dangerous possibilities and as a result will be vigilant members in their communities.”
In addition to intellectual challenges, students were also challenged to solve problems on the ropes course and leadership reaction course at NMMI. The instructors, who typically deal with cadets in these team-building and problem-solving activities, demand each student look past discomfort and shyness and focus on the problem at hand.
Eric Davidson, director of NMMI’s ropes course, says it helps students look beyond their limitations and attempt to solve problems using what they are given. He points to his own childhood as “a skinny guy” as an example of how people have to look for solutions that match their skills and abilities. “I am a skinny guy and a mountain climber. The solutions that a football player might use wouldn’t work for me.”
John says the students came away with a better understanding of themselves as leaders and an appreciation of the complexity of leadership and problem-solving challenges entailed by national security/homeland security problems.
In the future, John says he hopes to accommodate more students and offer a greater variety of experiences. -- Stephanie Holinka