The best replacement for silicon is silicone.

The best alternatives to silicon are rated as following:
★★★★★  silicone
★★★  silica
★★  germanium
★★  saline
★★  carbon
★★  saline implants
★  germanium fuzz
  graphene
  gaas
  caulk
  germanium diode
  gallium arsenide
  plumbers putty
  thin film silicon
  poly silicon
  germanium diodes
  thin film
  crystalline
  amorphous silicon
  hard case

Your alternative for silicon is not listed? Suggest!
Speaking about silicon, one probably shouldn't forget about boron.

Other search terms related to silicon and their ratings are:
★★★★★ boron
★ arsenic
germanium
You have in mind a companion for silicon and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of silicon in all years. Click on graph for more.
silicon
silicone
silica