Caesium telluride
Caesium telluride or Caesium telluridocaesium is an inorganic salt with a chemical formula Cs2Te. Caesium telluride is used to make photo cathodes. Caesium telluride is the photoemissive material used in many laser-driven radio frequency (RF) electron guns like in the TESLA Test Facility (TTF). References

Caesium compounds
Tellurides