A new discovery could revolutionise the way wearable technology is manufactured and improve the versatility of such devices in the coming years.
Researchers at Missouri S&T have found a way to grow thin layers of gold on single crystal wafers of silicon, and then remove the gold foils to use them as substrates on which to grow other electronic materials. Reported in the March 17 issue of the Science journal, the discovery could transform “flexible” or wearable technology research.
According to lead scientist Jay A. Switzer, up to now most of research into wearable technology has been done using polymer substrates. Because these are made up of multiple crystals, they have what are called grain boundaries which can greatly limit the performance of an electronic device.
“Say you’re making a solar cell or an LED,” he says.
“In a semiconductor, you have electrons and you have holes, which are the opposite of electrons. They can combine at grain boundaries and give off heat. And then you end up losing the light that you get out of an LED, or the current or voltage that you might get out of a solar cell.”
“99.99 percent of electronics are made out of silicon, and there’s a reason – it works great. It’s a single crystal, and the atoms are perfectly aligned. But, when you have a single crystal like that, typically, it’s not flexible.”
Researchers managed to retain all the positive characteristics of silicon but because the foil is made of gold, it is also highly durable and flexible. In tests, they bent it 4,000 times and the resistance did not change. Because the gold foils are so thin (the team managed to peel foils as thin as seven nanometers), they are also transparent.
Switzer says the challenge his research team faced was not in growing gold on the single crystal silicon, but getting it to peel off as such a thin layer of foil. Ultimately they resolved to photo-electrochemically oxidizing the silicon, which resulted in the gold just “sliding off”.
Switzer says thousands of gold foils can be made from a single crystal wafer of silicon.
“This is something that I think a lot of people who are interested in working with highly ordered materials like single crystals would appreciate making really easily,” he added.
“Besides making flexible devices, it’s just going to open up a field for anybody who wants to work with single crystals.”
Source: Missoury S&T
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