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cageymaru
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MIT engineers have developed a cost-effective technique to fabricate ultrathin semiconducting films made from a bevy of exotic materials. It has been known that these materials outperform silicon, but the rarity and expense of using exotic materials has been cost prohibitive. The new method initially used graphene, but it has been found that other materials that exhibit the same atomic electrical charge can be substituted. This opens up the pool of usable materials as they just need to have the same ionic charge. Kim says, "It's similar to the way two magnets can attract, even through a thin sheet of paper."
Scientists discovered that they could create copies of exotic materials by placing a layer of graphene as an atomically thin layer, in a chicken-wire pattern, over a wafer made from a pure and expensive semiconducting material such as gallium arsenide. This allowed the scientists to flow more of the expensive gallium arsenide over the graphene layers, and the gallium arsenide reacted with the wafer as if the graphene layers were invisible. "As a result, the atoms assembled into the precise, single-crystalline pattern of the underlying semiconducting wafer, forming an exact copy that could then easily be peeled away from the graphene layer. The technique, which they call "remote epitaxy," provided an affordable way to fabricate multiple films of gallium arsenide, using just one expensive underlying wafer."
"People have mostly used silicon wafers because they're cheap," Kim says. "Now our method opens up a way to use higher-performing, nonsilicon materials. You can just purchase one expensive wafer and copy it over and over again, and keep reusing the wafer. And now the material library for this technique is totally expanded." Such ultrathin films could potentially be stacked, one on top of the other, to produce tiny, flexible, multifunctional devices, such as wearable sensors, flexible solar cells, and even, in the distant future, "cellphones that attach to your skin."
Scientists discovered that they could create copies of exotic materials by placing a layer of graphene as an atomically thin layer, in a chicken-wire pattern, over a wafer made from a pure and expensive semiconducting material such as gallium arsenide. This allowed the scientists to flow more of the expensive gallium arsenide over the graphene layers, and the gallium arsenide reacted with the wafer as if the graphene layers were invisible. "As a result, the atoms assembled into the precise, single-crystalline pattern of the underlying semiconducting wafer, forming an exact copy that could then easily be peeled away from the graphene layer. The technique, which they call "remote epitaxy," provided an affordable way to fabricate multiple films of gallium arsenide, using just one expensive underlying wafer."
"People have mostly used silicon wafers because they're cheap," Kim says. "Now our method opens up a way to use higher-performing, nonsilicon materials. You can just purchase one expensive wafer and copy it over and over again, and keep reusing the wafer. And now the material library for this technique is totally expanded." Such ultrathin films could potentially be stacked, one on top of the other, to produce tiny, flexible, multifunctional devices, such as wearable sensors, flexible solar cells, and even, in the distant future, "cellphones that attach to your skin."
