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Gizmorama - Metamaterials empower semiconductor-free microelectronics
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Gizmorama - November 14, 2016
According to our first story, "scientists have designed and built the world's first semiconductor-free, optically-controlled microelectronic device." Okay. I have no idea what any of that means, but I can't help but get excited when I hear "world's first..."
Learn about this and more interesting stories from the scientific community in today's issue.
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* Metamaterials empower semiconductor-free microelectronics *
SAN DIEGO - Using metamaterials, scientists have designed and built the world's first semiconductor-free, optically-controlled microelectronic device.
The new device is 1,000 percent more conductive and boasts a much smaller band gap, meaning its conductivity can be triggered by a very low voltage and laser pulse.
Technology wouldn't be what it is today without semiconductors. But like most materials, the benefits of semiconductors are accompanied by constraints.
Semiconductors put up varying levels of resistance, which constrains electron velocity. Also, their relatively large band gaps require initial bolts of energy to trigger conductivity.
For some microelectronic components, like transistors, these pitfalls are especially problematic.
In large electronic devices with sizable semiconductor components, large jolts of energy, strong laser pulses or high temperatures can lessen these impediments and get electrons flowing freely. But these strategies don't work in smaller components.
Scientists at the University of California, San Diego sidestepped these problems by abandoning semiconductor materials in favor of metamaterials. The metamaterial is empowered by a metasurface, gold mushroom-like nanostructures etched onto an array of parallel gold strips. The metasurface is affixed to a silicon wafer, buffered by a layer of silicon dioxide.
When a small amount of power -- less than 10 volts -- and a low-power infrared laser are applied to the metasurface, the gold nanostructures generate "hot spots," intense electric fields strong enough to decouple electrons from the material. The electrons are pulled from the underlying material and allowed to move uninhibited.
"This certainly won't replace all semiconductor devices, but it may be the best approach for certain specialty applications, such as very high frequencies or high power devices," electrical engineering professor Dan Sievenpiper said in a news release.
Researchers described their breakthrough device in a new paper published this week in the journal Nature Communications.
"Next we need to understand how far these devices can be scaled and the limits of their performance," Sievenpiper concluded.
*-- Super-cooled electrons reveal their quantum nature --*
STUTTGART, Germany - When scientists cooled their scanning tunnelling microscope to temperatures approaching absolute zero, they discovered electrons moving at a snail's pace. Electric current failed to flow. Instead, it trickled.
At these extreme temperatures, scientists found, electrons reveal their quantum state. A quantum state is the understanding of a single entity within an isolated quantum system. In this instance, it is the understanding or approximation of an individual electron.
A scanning tunnelling microscope works by allowing a narrow electric current to flow across its tip onto the surface under examination. Perturbations in the flow allow scientists to glean information about the atomic structures found on the surface of the studied object or material.
But even at extremely low temperatures, the flow is still too fast to observe the movement of individual electrons. That is until the temperature approaches fifteen thousandth of a degree above absolute zero, or negative 273.135 degrees Celsius. At that point, electrons begin to trickle one by one like grains of sand falling through an hourglass.
The phenomenon yields new anomalies in the electric feedback recorded by the microscope -- new structures.
"We could explain these new structures only by assuming that the tunnelling current is a granular medium and no longer homogeneous," Christian Ast, a scientist at the Max Planck Institute for Solid State Research, said in a news release.
Researchers described their quantum experiments in a new paper, published this week in the journal Nature Communications. Their findings confirm theoretical hypothesis offered by scientist some two decades ago.
"The theory on which this is based was developed back at the beginning of the 1990s," said study co-author Joachim Ankerhold, a researcher from the University of Ulm. "Now that conceptual and practical issues relating to its application to scanning tunnelling microscopes have been solved, it is nice to see how consistently theory and experiment fit together."
It's not the first time electrons have revealed their quantum nature, but it is the first time a scanning tunneling microscope has been shown to have reached its quantum limit. Researchers are hopeful their findings will lead to new and unexpected quantum insights.
"These extremely low temperatures open up an unexpected richness of detail which allows us to understand superconductivity and light-matter interactions much better," concluded Ast.
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