silicon nitride

The laser beam in an optical tweezer is not just a spot of light but a force bag. A particle caught in it usually rolls toward the brightest point, like a ball into a dimple.

No one has ever seen dark matter, but it should pass through detectors like wind through leaves. Sometimes, very rarely, a dark matter particle bumps into an atomic nucleus, and then the detector must catch that jolt. The trouble is that light dark matter particles can hardly move heavy nuclei: it's like trying to knock down a bowling pin by throwing a feather at it.

You can make light turn on command, like water in a hose — if you know where to squeeze. That's what electro-optic circuits do: they change the direction of a beam inside a chip using an electric field. The classic material for such tricks is lithium niobate, a crystal that responds to voltage like a string to a pluck.

A smartphone camera captures light with tiny sensors, but by themselves, they can't distinguish colors. So color filters are placed in front of them: red, green, blue, like stained glass in a window. Each sensor sees only its own color, and then software assembles the full picture from these pieces.

In an ordinary room, light vanishes the moment you switch off the lamp. In a tiny silicon nitride cavity, a photon can bounce between the walls 80,000 times before it gets lost. It's like a ball thrown into a room that rebounds off the walls with almost no loss of speed.

A sodium iodide crystal doped with thallium is like photographic film for invisible particles. When a gamma ray or a hypothetical dark matter particle hits it, it flashes with faint light. Two silicon photomultipliers pressed against the crystal's ends catch the flash from both sides.

In the cold Taurus cloud, where stars are born, telescopes have detected molecules with the smell of bitter almonds — aromatic nitriles. On Earth, you can find them in peach pits, but in space they hang in icy dust. What happens to them under the harsh ultraviolet light of young stars? Chemists recreated this process in the lab.

Spectroscopy has always been a way to hear the unheard. Back in the 19th century, Johann Balmer deciphered the elegant lines of hydrogen — a simple numerical harmony that foreshadowed quantum theory.

Two white sheets lie in the sun — one rough, one smooth. Which one heats up less? The rough one scatters light more strongly, so it seems it would stay cooler. But if the coating is made of many transparent glass beads, the logic changes. Light wanders through it like in a thick fog, and at some point it stops noticing individual droplets.

A smartphone camera captures everything indiscriminately, but the eye immediately picks out what matters. The retina doesn't just pass the image to the brain: it highlights contours on the spot, suppresses noise, and adjusts to brightness.

Hot gas settles on a substrate, building up a transparent film layer by layer. But instead of a perfect mirror, the surface sometimes gets covered with tiny bumps, like frost patterns on glass in severe cold. Usually, people try to remove them because they get in the way of making smooth components. Physicists from Oxford and their colleagues did the opposite: they looked inside the bumps.

Quantum networks need a mediator between storage — spin — and carrier — light. No single molecule had ever pulled off such a feat. But now physicists have found a solution. They placed a carbene molecule into a crystal and cooled it to -269°C.

A layered cake of atomic planes of nickel and oxygen: that's how bilayer nickelates are built. Two such planes are separated by a spacer layer. If an oxygen atom sits in that spacer, it acts as a bridge: it links the layers and triggers a state in which electrons move without resistance.

In the basements of four European institutes stood seven devices: each can be compared to a tuning fork of unimaginable precision. But instead of sound, they emit 'ticks' made of light: oscillations of a laser locked to a specific frequency by atoms of strontium, ytterbium, or mercury.

A bridge of aluminum just a few atoms thick is the heart of many quantum devices. Current flows through such a bridge without resistance, and it can be controlled with a magnetic field. These bridges are called Josephson junctions, after the British physicist who described their behavior.

A sheet of paper weighs almost nothing, but stack a hundred sheets and you get a noticeable pile. That's roughly what scientists did with a material that excels at converting one color of light into another, but only when it's just one atom thick. A single layer is like a single sheet: it works beautifully, but it's too thin to produce much light.

A crowd on a narrow street moves slowly because people bump into each other. In silicon, heat is carried by similar 'shoves'—atomic vibrations called phonons. If you cut tiny holes in a silicon film, phonons will bump into them like pedestrians into lampposts, and heat will flow worse.

Table salt makes food taste better in the kitchen, but in the lab it helps grow crystals just a few atoms thick. Scientists took tin selenide and, with the help of salt, grew ultra-thin flakes from it, so thin they're called two-dimensional. The salt acted as a separator: it kept the flakes from clumping together and made them lie flat on the substrate, like pancakes on a griddle.

The compass needle trembles when a truck rumbles by. Similarly, in a tiny gyroscope, a device that senses rotation, any noise drowns out the useful signal. For a long time, engineers couldn't shrink a gyroscope down to fingernail size without sacrificing accuracy. The solution came in a two-loop architecture.

Dirty water laced with antibiotics isn't just waste: it's a hidden energy source. Chemists built a material from two components: titanium oxide nanorods (the white pigment in paints and sunscreens) and carbon nitride nanosheets.

Plain water in a glass is clear and calm. But if you add tiny carbon dots made from sugar and citric acid in an ordinary microwave, the water starts to glow when a charged particle flies through it.

You can launch sound in a crystal at a frequency so high that the human ear can't hear it, and make that sound run in circles, like a train on a loop track. Engineers took a thin film of silicon nitride, deposited it on a lithium niobate substrate, and carved waveguides for sound waves into it.

Microplastics, tiny fragments of synthetic polymers, are now found everywhere, from mountain glaciers to food. The traditional analytical approach, spectroscopy, which relies on light interacting with matter, has long required costly detectors to register invisible infrared radiation.

Tuning a radio to your favorite station is a search for the right frequency amid the noise. The new device does the same, but for waves about three millimeters long. Such waves come from distant galaxies and possibly from dark matter particles. The device is a pattern of superconducting niobium traces on a silicon wafer.

Deep in a cave beneath the Italian Apennines, a tank of gas sits in the dark. Inside, charged particles fly through, leaving faint flashes of light in their wake. These flashes are like the wake of a boat on dark water: they reveal where the particle went and how fast.

Hidden inside a zinc oxide crystal is a quantum duo: a tin atom and a lithium atom sitting side by side. Their bond is so tight that the electron captured by this pair seems to live on the tin, while the lithium merely plays along. This complex was long sought after, but only now has it been deliberately created and identified by its characteristic glow.

A glowing dot the size of a molecule. Run a current through it, and it flashes like a tiny lightbulb. That's what the experiment with dye molecules on a thin salt film looks like. When current enters a molecule, one electron hands it energy. The molecule immediately gives that energy back, as light. It's like a swing: give it one push, and it rocks and then stills.

A factory smokestack releases carbon dioxide into the air, and nearby stands a unit that captures this gas and, under sunlight, assembles ethylene molecules from it — the feedstock for plastic bags and pipes. Materials scientists have brought this scenario closer by modifying a crystal of the semimetal PdSn4 with a small amount of platinum.

An ordinary wire heats up when current flows through it. A superconductor doesn't. But almost all known superconductors require either very low temperatures or enormous pressures, like those deep inside planets. Scientists have long searched for a material that avoids these extremes.

A thin crystal of hexagonal boron nitride is a relative of graphite, but transparent and insulating. Occasionally, single defects appear in its lattice: a boron or nitrogen atom is missing, leaving a trap for electrons. Such a trap can absorb light and re-emit it, like a tiny flashlight.

Sunlight hits a rooftop, and electrons are born in a thin film. They must reach the wires before they cool down and lose their energy. In tin sulfide, a cheap and accessible material for batteries, this sprint and cooldown has now been captured with unprecedented sharpness: frames follow every billionth of a billionth of a second.

A thick slice of tissue under a microscope looks like fogged glass: light scatters and details are lost. Usually, to see cells, you stain them or cut them into very thin slices. But there's a simpler way — make the slice itself transparent, as if you've wiped the glass clean.

A laser beam passes through glass and touches a thin diamond film. At the point of contact, the film turns into a narrow strip that lifts slightly. We place a second strip next to it, and between them remains an empty corridor. That's the channel: its width can be fifty times its height, like a sheet of paper lying on a table.

Sodium is lithium's neighbor on the periodic table, but it's hundreds of times more abundant in the Earth's crust and much cheaper. So sodium batteries could replace lithium ones in electric vehicles and energy storage.

Infrared light with a wavelength of about three micrometers is the working range for identifying molecules: each molecule absorbs light at its own characteristic frequencies, leaving behind "fingerprints." But until now, instruments for this range could not simultaneously provide broad frequency coverage, sufficient power, and…

Imagine blinds that don't just block or let through light but change its color. Light hits the slanted stripes, and some rays come out a different shade, as if a white beam, passing through the slits, turned green. That's exactly how this new surface works: on a thin film of lithium niobate (a material that can transform light), there are slanted stripes of titanium dioxide.

A light pulse, like a lump of clay, keeps its shape when passing through an ordinary material. But if you put a special layer just one atom thick in its path, the pulse starts to spread: its spectrum widens.

Waves in magnets resemble the vibrations of a string: if you pluck a string, it sounds a single note, but with a strong pluck, overtones appear — sounds at multiple frequencies.

In the cold clouds between the stars, where new suns are born, invisible chemical work is underway. Simple molecules collide, swap atoms, and assemble into chains that may later become part of planets. One such chain is the NCCO+ ion, made of nitrogen, two carbons, and oxygen.

Nitinol is a metal with a memory: compressed into a tiny tube, it springs back into shape inside a vessel and keeps it open. But simply inserting a stent isn't enough: it must not clog with clots. To prevent that, a drug is applied, which should be released slowly, like water from a sponge, not all at once.