Novoselov, K. S., Geim, A. K., Morozov, S. V., Jiang, D. E., 
Zhang, Y., Dubonos, S. V., ... & Firsov, A. A. (2004). Electric 
field effect in atomically thin carbon films. science, 306(5696), 
666-669.

Abstract
We describe monocrystalline graphitic films, which are a few 
atoms thick but are nonetheless stable under ambient conditions,
metallic, and of remarkably high quality. The films are found 
to be a two-dimensional semimetal with a tiny overlap between 
valence and conductance bands, and they exhibit a strong ambipolar
electric field effect such that electrons and holes in concentrations 
up to 10^13 per square centimeter and with room-temperature 
mobilities of ~10,000 square centimeters per volt-second can be 
induced by applying gate voltage.