We Can Figure This Out.org
Virtual Lab: Quantum-dot Cellular Automata - Memory Cells
University of Virginia
             
 
© 2003-Present, John C. Bean
 
Looking inside our PC of the future, we can see the QCA cells. Each QCA consists of a group of four quantum dots. These dots may be as small as 30 nanometers across (~300 atoms wide). Here we depict dots made of SiGe alloy on top of a wafer of Si.

The key requirement is that electrical charge must naturally be attracted to the dots. For SiGe, dots naturally become positive as they squeeze an electron out into the surrounding Si.

So these dots like to charge positive. But positive charges do not like to get to close to one another (and these dots are very close!). So, charging can stop after only two dots have become positive.

 
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