Tuesday January 14, 2014
A mini-monument, made of semiconductor laser material. It looks to me a bit like Devil’s Tower. It’s much, much smaller, though. Scaling this little nano-tower (600nm high) to the height of Devil’s Tower (386m high) would be like scaling up an average-sized human (~1.7m) to about 1.1 billion meters tall. This is, as Wolfram Alpha helpfully informs us, about 3x the distance between the earth and the moon. Every time I do a calculation like this, it still boggles me how tiny these nanostructures are.
So, what is the nanotower doing here? This is an image of a plasma-etched wafer of semiconductor, the sort we like to make lasers out of. I was testing the plasma-etching process, so I was just etching simple structures into this wafer. I did get etching - the top of the tower is where the top surface of the wafer used to be; the tower itself was formed by a tiny dust particle that happened to land on a surface, shielding a bit of the wafer from the plasma. Unfortunately, I also got this strange fluffy surface on the wafer, signs of problems with the etching gases, or possibly contamination in the chamber.