Sunday, December 30, 2007

Nanotechnology - how to get into it, and where it's going

This post is in response to a comment here seeking some advice about nanotechnology, and is relatively brief.

What is nanotechnology? Nanotechnology is a vague, overly broad term. The most commonly accepted definition is something like "nanotechnology is any technology making use of the unique properties of matter structured on length scales smaller than 100 nm." By this definition the semiconductor industry has been doing nanotechnology for a long time now. The point is, in the last ten to twenty years, we've learned a lot about how to engineer materials and structure them in all three dimensions (under the right circumstances) on scales much smaller than 100 nm. This capability has a real chance of having a major impact on a large number of industries, from biomedical sensing and treatment to light strong structural composites to energy generation to waste remediation.

What should I study if I'm interested in nanotechnology? Nanoscale science and engineering is broad and interdisciplinary. The main avenues for getting into cutting edge work at these scales remain condensed matter physics, physical chemistry, and electrical engineering programs, though there are exceptionally good people working at the nanoscale in bio, bioengineering, chemical engineering, and mechanical engineering programs as well. The best approach, in my opinion, is to get a first-rate education in one of these traditional disciplines and focus on the nano, if you want to make scientific or engineering research contributions. Broad nano overview programs right now are better suited to people who want to be scientifically literate for decision-making (e.g. managers or patent lawyers) rather than those who want to do the science and engineering.

Is there really substance behind the hype? Is nanotechnology actually going somewhere? There is definitely substance behind some of the hype. As a very recent example, this new paper in Nature Nanotechnology reports a way of making lithium ion battery electrodes from silicon nanowires. Because it's in nanowire form, the Si can take up huge amounts of Li without the resulting strain pulverizing the Si. Between that and the huge specific surface area of the nanowires, real gains over conventional batteries should be possible. Best of all, industrial scaleup of Si nanowire growth looks achievable.

That's just one example from the past week. There is an awful lot of silliness out there, too, however. We're not going to have nanorobots swimming through our bodies repairing our capillaries. We're not going to have self-reproducing nanomachines assembling rocket engines one atom at a time out of single-crystal diamond. Getting a real science or engineering education gives you the critical skills and knowledge to tell the difference between credible and incredible claims.

Is going into nanotechnology a stable career path relative to alternatives? Another reason to get a solid education in a traditional science or engineering discipline is that you shouldn't be limited to just "nano" stuff. Frankly, I think this would be far more useful in just about any career path (including law or medicine) than an undergrad degree in business. Still, there are no guarantees - learn to be flexible, learn to think critically, and learn to solve problems.

Texas and "creation science"

Is it a coincidence that every state panel staffed with Rick Perry appointees does something to undermine science education and science literacy in this state? The latest ridiculousness comes from an advisory panel to the Texas Higher Education Coordination Board, who have recommended in favor of recognizing Masters of Science Education degrees granted by the Institute for Creation Science Research. Yes, that's right - this isn't even the subtle creationism of "Intelligent Design". This is full-on young Earth creationism, as explained on the ICR's own FAQ page:
All things in the universe were created and made by God in the six literal days of the creation week described in Genesis 1:1-2:3, and confirmed in Exodus 20:8-11. The creation record is factual, historical and perspicuous; thus all theories of origins or development which involve evolution in any form are false. All things which now exist are sustained and ordered by God's providential care. However, a part of the spiritual creation, Satan and his angels, rebelled against God after the creation and are attempting to thwart His divine purposes in creation.
Remember, if you believe in evolution in any form, or that the universe is actually 13 billion years old, according to these folks who want to staff science faculty positions in Texas you have been corrupted by Satan and his agents. Great.

To the arguments of the Houston Chronicle against granting the ICR request, let me add two more (both admittedly self-serving): this seriously hurts our ability to recruit high tech professionals to this state, and this puts Texas science and engineering faculty at a competitive disadvantage for funding. For example, ordinarily it would be a plus for a large center proposal to the NSF to be coupled to the state's education initiatives. In Texas, that's not clear.

Saturday, December 22, 2007

Books on science this holiday season

From his new book, I am America (and so can you!), part of Stephen Colbert's view of science:
" 'Why?' -- The question scientists are always asking. You know who else is always asking 'why?' ? Five year olds! That's the kind of intellectual level we're dealing with here."

That's the best justification for my desire to be a scientist that I've seen since I read Tom Weller's book Science Made Stupid back when I was in high school:
"What is science? Put most simply, science is a way of dealing with the world around us. It is a way of baffling the uninitiated with incomprehensible jargon. It is a way of obtaining fat government grants. It is a way of achieving mastery over the physical world by threatening it with destruction."

I've also been reading Uncertainty, a very well-written book about the birth of quantum mechanics that focuses mostly on the personalities of the major players. It's a compelling story, though there are no major surprises: Heisenberg was ludicrously bright; Bohr was incapable of writing a short, declarative statement; Pauli was a sarcastic bastard who could get away with it because he was brilliant; Einstein was already the grand old man.

I can also recommend American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer. I'm not done with this one yet, but it's extremely interesting. If you thought that socially awkward, neurotic people going into science was a recent phenomenon, think again.

Tuesday, December 18, 2007

Research and corporations

This article from the NY Times is worth reading. Basically it points out something I've said repeatedly in the past: some corporations think that they can substitute university-funded research for what used to get done in big industrial research labs (like Bell Labs, IBM, Xerox, GM, Westinghouse, Ford Scientific, RCA, etc.). I think that there's definitely a place for corporate funding of university research, provided the company goes into this with their eyes open and conscious of the realities of academic work. However, I don't think university research projects will ever be able to approach the total intellectual effort that IBM or Bell could bring to bear on an important problem. If Bell decided that some piece of solid state physics was important, they could put 35 PhDs onto the problem. There just isn't that kind of concentration of expertise at a university - we're all working on different areas, for the most part.

Monday, December 17, 2007


Now that it's been published online, I can talk about our new paper about magnetite. Back in August I wrote a post about the different types of papers that I've been involved with. This one fits the third category that I'd mentioned, the (Well-Motivated) Surprise, and it's been a fun one.

Background: Magnetite is Fe3O4, also known as lodestone. This material is a ferrimagnet, meaning that it has two interpenetrating lattices of magnetic ions with oppositely directed polarizations of different magnitudes. Since one polarization wins, the material acts in many ways like a ferromagnet, which is how it was first used in technology: to make primitive compasses. The magnetic ordering temperature for magnetite is about 860 K. Anyway, at room temperature magnetite has a crystal structure called inverse spinel, with two kinds of lattice sites for iron atoms. The A sites are each in the center of a tetrahedron with oxygen atoms at the corners, and are occupied by Fe(3+). The B sites (there are twice as many as A sites) are each in the center of an oxygen octahedron, and are occupied by a 50/50 mix of Fe(3+) and Fe(2+), according to chemical formal charges.

It's been known for nearly 70 years that the simple single-electron band theory of solids (so good at describing Si, for example) does a lousy job at describing magnetite. Fe3O4 is a classic example of a strongly correlated material, meaning that electron-electron interactions aren't negligible. At room temperature it's moderately conducting, with a resistivity of a few milli-Ohm-cm. That's 1000 times worse than Cu, but still not too bad. When cooled, the resistivity goes weakly up with decreasing temperature (not a standard metal or semiconductor!), and at about 120 K the material goes through the Verwey transition, below which it becomes much more insulating. Verwey first noticed this in 1939, and suggested that conduction at high temperatures was through shifting valence of the B-site irons, while below the transition the B-site irons formed a charge ordered state. People have been arguing about this ever since, sometimes with amusing juxtapositions (hint: look at the titles and publication dates on those links).

Motivation: I'd been interested for a while about trying to do some nanoscale transport measurements in strongly correlated systems. The problem is, most relevant materials are very difficult to work with - not air stable, difficult to prepare, etc. Magnetite is at least a well-defined compound, and the Verwey transition acts as something of a gauge of material quality, at least in bulk. Screw up the oxygen content by a couple of percent, and the transition temperature falls through the floor.

What did we find: In two different kinds of magnetite nanostructures, we found that the I-V characteristics become dramatically hysteretic once the sample is cooled below the Verwey transition. This was completely unexpected! Basically it looks like you can take the system, which wants to be a decent insulator in equilibrium at low temperatures, and kick it back into a conducting state by applying a large enough electric field. Reduce the field back down, and the system remains in the conducting state until you pass a lower threshold, and then the magnetite snaps back into being an insulator. We worked very hard to check that this was not just some weird self-heating problem, and that's all described in the paper. I should point out that other strongly correlated insulators (vanadium oxides; some perovskite oxides) seem to be capable of qualitatively similar transitions. Hopefully we'll be able to use this transition as a way of getting a better handle on the nature of the Verwey transition itself - in particular, the role of structural degrees of freedom as well as electronic correlations.

Tuesday, December 11, 2007

Hahvahd and the burden of financial excess.

As pointed out by Julianne at Cosmic Variance, the president of Harvard had this to say about the combined issue of declining federal science research (in real dollars) and Harvard's soul-crushing dilemma of extreme wealth:
"One thing we all must worry about — I certainly do — is the federal support for scientific research. And are we all going to be chasing increasingly scarce dollars?" says Drew Gilpin Faust, Harvard's new president.

Not that Faust seems worried about Harvard or other top-tier research schools. "They're going to be—we hope, we trust, we assume—the survivors in this race," she says. As for the many lesser universities likely to lose market share, she adds, they would be wise "to really emphasize social science or humanities and have science endeavors that are not as ambitious" as those of Harvard and its peers.

Wow. So much for thinking that Larry Summers' arrogance was anomalous.

Thursday, December 06, 2007

Abstract fun

I spent my day at APS headquarters sorting abstracts for the March Meeting, the big condensed matter gathering that now approaches 7000 talks and posters. This is the second time I've done this, and it's always an interesting experience. When people submit abstracts they are supposed to choose a sorting category so that their talk ends up in an appropriate session - that way the audience will hopefully include people that actually are interested in the subject of the work. The contributed talks at the March Meeting are each 10 minutes, with 2 minutes for questions. Often these talks are the first chance a graduate student gets to present their work in a public forum before other scientists. Unfortunately 10 minutes is very short, so much so that often only near-experts in an area can get much out of such a brief explanation of results. There are also invited talks that are 30 minutes with 6 minutes for questions. These can be arranged in Invited Sessions, where all the talks are invited, and the session theme and potential speakers are nominated and voted upon by the program committee. Alternately, there are mixed Focus Topic sessions that typically have one or two invited talks mixed in with contributed ones.

The first big challenge in sorting the abstracts is that the sorting categories often overlap. For example, there were at least four different categories where people could have submitted abstracts about electronic properties of quantum dots. Surprisingly, about 80 people pushing around 7000 slips of barcoded paper is a reasonably efficient way of sorting. The second major issue in organizing the meeting is that space is very limited, and sessions are highly constrained - you don't want a contributed session to take place at the same time as an invited session on a closely related area, for example.

Helping to put together meetings like this is a bit like the scientific equivalent of jury duty. You want to make sure that it gets done well by people whose judgment you trust, but you don't want to have to do it yourself very often. It is a good way to get meet your fellow physicists, though.

Saturday, December 01, 2007

Texas, you're not making this any easier.

Well, looks like it's time for another of my once-every-few-months occasions to be severely disappointed in public agencies in Texas. This time the director of the state's public school science curriculum has been forced out, apparently because she prefers evolution to "intelligent design". This is just pathetic. While I appreciate Eric Berger's spirited defense of Texas (in short, we're not all antiscience zealots), the steady stream of this stuff from Austin is unquestionably depressing.