Silicon at Apple
by Paula Quinterno
July 4, 2023
Have you seen the new artwork called Mirage at the Apple Park Visitor Center in Cupertino?
It is made of more than 400 glass pillars that were made from sand collected from 70 deserts across the world.
The pillars are arranged in a sinuous pattern between olive trees in the park-like setting.
It is impressive and very interesting, but I think visitors would appreciate it more if they understood how
appropriate it is to have it located where it is.
Although the pillars are made from sand from different geographical locations and, therefore,
vary somewhat in chemical composition from desert to desert, the dominant compound of most sand is silicon dioxide (SiO2),
and that is the source material from which Silicon is derived to make computer chips.
Corporate headquarters for Apple, Inc. is a 4-story circular building in Apple Park called The Ring, and is mostly faced of glass.
Eight hundred 45-foot high glass panels connect all the way around the 2.8 million square foot building.
That is a lot of Silicon hugging the building!
I don't know if the creators of Mirage or the people who planned The Ring realized the connection between glass and Silicon, but I think understanding the connection makes the Mirage pillar artwork and the huge building much more enjoyable.
Galena is an ore of lead. Side by side with pure silicon they look very similar. In your hand, the galena will feel much heavier. When impacted silicon will shatter like glass. On the other hand galena will break into little cubes.
Photo Left side: solar cell made of multicrystalline silicon. Photo Right side: polysilicon rod (top) and chunks (bottom). Pure silicon can be made in a form that has many crystals in different orientations. The main application of this form are solar cells. Looking closely at a solar cell you can easily make out the crystal boundaries. In the chunks note the scooped surfaces just like in broken glass (silicon dioxide).
Single crystal silicon is grown using the Czochralski method. The pure silicon is melted in a crucible, seeded with a silicon crystal and pulled slowly out while being rotated. The result is a single crystal ingot or boule in a cylindrical form.
A silicon wafer is sliced out the the ingot/boule polished to be very flat. As the raw material for semiconductor integrated circuits it has no pattern because it is a single crystal with very few defects. That perfection lands up producing a mirror finish. Pure single crystal silicon is very strong, but also brittle and shatters like glass.