7.9.2019.

Spent the morning before my lecture to create phase diagrams for one of my master’s projects. Trying to estimate the solid solution strengthening possibilities of all the elements in a system.

Aluminum target for our sputter system. If you look closely you can see individual crystal grains.

Sputtering is a technique used to deposit thin films of material. The material source is called a target because it is bombarded with high energy atoms which remove bits of material that are then redeposited on your sample or wafer. The ring is a result of the magnetic field confining the plasma to that region.

Discarded AFM tips.

Atomic Force Microscopy, or AFM, is a technique by which a small mechanical probe is scanned across a sample to create a height map. This technique has very high resolution, less than a nanometer, depending on what kind of tip is being used, and can be done in ambient conditions (no need for vacuum). AFM is useful for getting roughness data and measuring film thickness, and can be combined with other microscopy techniques to get a complete picture of your device.

AFM probes often get damaged or dirty, resulting in “tip graveyards” like the one shown here.

Sample stage controls for an ion mill, allowing for rotation about two different axes.

Ion milling is a type of dry etch process used to remove parts of a sample by bombarding it with ions, typically argon, in a vacuum chamber. It can be thought of as an atomic sand blaster. Ions (the “grains of sand”) physically expel, or sputter, chunks of material from the surface. The sample is rotated to ensure uniform coverage.

Patterned silicon wafers in the clean room.

Photolithography is a technique similar to photography used to make very small micron (~0.00004 inch) sized features.  Wafers are coated in light sensitive chemicals called photoresist and then certain areas are exposed to light to create a pattern. The processing room is lit with yellow light to avoid exposing the resist. Photolithography is commonly used to make integrated circuits in electronics, but it is also used in basic research in fields such as physics, material science, engineering, and even biology.

Cryopump on a sputter system.

Cryopumps are a common type of high vacuum pump. They operate by condensing or freezing gases in the vacuum chamber onto an array that is typically cooled down to 10-12 kelvin. Compressed helium gas enters a chamber below the condenser array, where a piston (the displacer) allows the gas to expand, removing heat from the system. The piston then pushes the helium out and back into a compressor, and the cycle repeats. The displacer and compressor in a cryopump make a distinctive rhythmic high pitched whistle that is a common sound in clean rooms and condensed matter physics labs.

A sputter system in our lab.

Platinum plasma in our sputter system. 

Plasma is the fourth state of matter (in addition to solids, liquids, and gases) that can be best described as an ionized gas.  It is a high energy state, in which there is sufficient energy to strip electrons from atoms or molecules in a gas.  The plasma glows because when the electrons recombine with atoms, energy is released in the form of light.  The color of the light depends on the composition of the plasma.  The plasma in this picture is purple mainly because of the argon ions used to bombard the platinum.

Surprisingly, even though plasma is probably one of the least known of the states of matter, it is the most common in the universe.  Examples of plasmas encountered in nature include lightning, some types of flames, nebulae, and stars.

we-are-star-stuff:

5 Amazing Scientific Discoveries We Don’t Know What to Do With

Every day, scientists make discoveries that change the way we live. But sometimes, just sometimes, they achieve results that are so extraordinary or unexpected that they literally don’t know what to do with them. Here are five of the most puzzling.

Mind-bending material properties

In January, a team of physicists from Rutgers and MIT published a paper in Nature describing a new property of matter. While fiddling around with a super-cooled Uranium compound, URu₂Si₂, they found that it breaks something called double time-reversal symmetry. Normal time-reversal symmetry states that the motion of particles looks the same running back and forth in time: magnets break that, though, because if you reverse time, the magnetic field they produce reverses direction. You have to reverse time twice to get them back to their original state.

This new material, though, breaks double time-reversal symmetry. That means you need to reverse time four times for the behaviour to get back to its original state. It’s something the scientists have dubbed hastatic order - and if you’re struggling to get your head round it, well, that’s the appropriate reaction. The scientists who discovered the phenomenon can’t explain a good physical example of what it is, how it works, or what it means.

The universe weighs less than we thought

When the world’s best scientists decided to team up and measure the mass of the universe all the way back in the 1970s, they set themselves a pretty tall challenge. Applying their best understanding of gravity and the dynamics of galaxies, though, they came up with an answer - an answer which sadly predicts our universe should be falling apart. We know that the Universe’s matter orbits a single central point and that must mean its own motion generates enough centripetal force to make that happen.

But calculations suggest that there’s not actually enough mass in the galaxies to produce the forces required to keep it moving in the way we’ve observed. So physicists scratched their heads, worried a little, then proudly stated that there must be more stuff out there than we can see. That’s the theory behind what everyone now refers to as Dark Matter. The only problem? In the past 40 years, nobody has confirmed whether it really exists or not - so, effectively, the problem thrown up by those initial calculations remains.

The placebo effect

Feed a sick man a dummy pill that he thinks will cure him and, often, his health will improve in a similar way to someone taking real drugs. In other words, a bunch of nothing can improve your health. In theory, it could be a poweful treatment technique.

But experiments have shown that the kind of nothing you deliver matters: when palcebos are laced with a drug that blocks the effects of morphine, for instance, the effect vanishes. While that proves that the placebo effect is somehow biochemical (and not just a psychological effect) we know practically nothing else about the power of placebo.

It’s real, sure. It can help people get better, agreed. But if we’re ever to make anything of the much-studied but little-understood effect, we’re going to have to unpick how the mind can affect the body’s biochemistry - and, right now, nobody knows.

Temperatures below absolute zero

It used to be that scientists all agreed that it was impossible to achieve temperatures below absolute zero. It was literally the coldest anything could ever get. Late last year, though, a team of scientists from the Max-Planck-Institute in Germany blew that out of the water: finally, they’d cooled a cloud of gas atoms to below −273.15°C. In fact, the result was as much a quirk of the definition of temperature as anything else, and the way it relies on both energy and entropy (the measure of disorder of particles). New Scientist explains:

In principle [it’s] possible to keep heating the particles up, while driving their entropy down. Because this breaks the energy-entropy correlation, it marks the start of the negative temperature scale, where the distribution of energies is reversed – instead of most particles having a low energy and a few having a high, most have a high energy and just a few have a low energy.

It’s this curious logic that allowed the Max-Planck-Institute researchers to cool a variety of atoms in a vacuum, for the the first time ever, to below absolute zero. So far, though, they haven’t managed to work out what to do with the chilled particles.

Cold fusion

Back in 1989, a pair of scientists -Fleischmann and Pons- claimed that they’d achieved a remarkable feat: they’d successfully observed nuclear fusion at room temperatures. Momentarily, the finding was heralded as a revolutinary discovery that could transform energy production around the globe. Sadly their experiments weren’t reproducible, but they did inspire scientists to study cold fusion in more depth.

Turns out, the process is in fact theoretically possible. For two atoms to fuse together, they need to come close enough to each other to overcome their mutual electric repulsion, which is caused by the cloud of electrons that orbit them. Usually that’s made possible by super-high temperatures -like at the center of the sun- but quantum physics suggests that there is at least the possibility that atoms can fuse without the need for energy injection via high tempeatures.

And it’s that hope that means a small band of scientists still work in the shadows, trying to get cold fusion to work. Of course, while occasional results come and go, they tend to be rather dubious. Fundamentally that’s because, even though quantum theory tells us it should be possible, nobody knows how to use that understanding to actually get a fusion reaction going.

The Higgs Boson

Just kiddin’. We’ve known what to do with Higgs since forever.

materialsscienceandengineering:

Upsizing nanostructures into light, flexible 3-D printed metallic materials

For years, scientists and engineers have synthesized materials at the nanoscale level to take advantage of their mechanical, optical, and energy properties, but efforts to scale these materials to larger sizes have resulted in diminished performance and structural integrity.

Now, researchers led by Xiaoyu “Rayne” Zheng, an assistant professor of mechanical engineering at Virginia Tech have published a study in the journal Nature Materials that describes a new process to create lightweight, strong and super elastic 3-D printed metallic nanostructured materials with unprecedented scalability, a full seven orders of magnitude control of arbitrary 3-D architectures.

Strikingly, these multiscale metallic materials have displayed super elasticity because of their designed hierarchical 3-D architectural arrangement and nanoscale hollow tubes, resulting in more than a 400 percent increase of tensile elasticity over conventional lightweight metals and ceramic foams.

Read more.