Last November 7, engineers from the University of California San Diego have created a peculiar chip—it’s the first semiconductor-free, optically-controlled microelectronic device. By using metamaterials, engineers were able to build a microscale device which shows a 1,000 percent increase in the conductivity when it is activated by low voltage as well as a low power laser.
This discovery paves the way for microelectronic devices which are faster and way more capable of controlling more power. Additionally, it can also lead to more efficient solar panels. Their work was published in Nature Communications.
Source: JacobsSchoolNews
According to the researchers, the capabilities of existing microelectronic devices are very limited by the properties of their essential materials like semiconductors.
As an example, semiconductors could set limitations on the conductivity of a device, or its electron flow. Semiconductors have a band gap, which means that they need a boost of external energy in order for the electrons to flow through them. Since electrons are constantly colliding with atoms as they flow through the semiconductor, the electron velocity is therefore limited.
Source: University of California San Diego
The team of researchers in the Applied Electromagnetics Group led by electrical engineering professor Dan Sievenpiper at UC San Diego wanted to remove these hindrances to conductivity by replacing semiconductors with free electrons in space.
However, doing so is not an easy task. Freeing electrons from materials either requires applying high voltages (around at least 100 Volts), high power lasers or extremely high temperature (more than 1,000 degrees Fahrenheit). All these mentioned solutions aren’t practical in micro-and nano-scale electronic devices.
The researchers took on this challenge and were able to fabricate a microscale device that is able to release electrons from a material without the need for extreme requirements. This device consists of a specialized engineered surface called a metasurface, on top of a silicon wafer, with a layer of silicon dioxide in between. The metasurface is made up of an array of gold nanostructures that has a mushroom shape on an array of parallel gold strips.
This gold metasurface has been designed in a way that when low DC voltage (lower than 10 Volts) and a low power infrared laser are both applies, the metasurface generators “hot spots”. Hot spots are spots with a high intensity electric field which provide enough energy to pull electrons out from the metal, and free them into space.
The device has been tested and showed a 1,000 percent change in conductivity! This means that there are more available electrons for manipulation.
“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,” Sievenpiper said.
Source: University of California San Diego
The researchers said that this particular metasurface has been design as a proof of concept. There will be a need for designing and optimizing different metsurfaces for different types of microelectronic devices.
According to Sievenpiper, “Next we need to understand how far these devices can be scaled and the limits of their performance.” The team is also studying other applications for their discovered technology besides electronics. This will open doors to new kinds of photovoltaic devices or environmental applications.
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University of California San Diego
