Intercalation of hexagonal boron nitride with potassium

We have performed photoluminescence, photoexcitation, and transmission electron microscopy measurements on boron nitride films grown by chemical vapor deposition and later reacted with potassium. After reaction, the potassium atoms were found to intercalate the BN host and to form a (2×2)R0° in-plane structure which is commensurate with the pristine BN lattice. Optical transitions with ∼2.7 eV onsets were found to occur within the ∼5-eV BN band gap and have been interpreted as Γ-point transitions between the K(4s) band and the BN(2p) bands. The absence of an appreciable shift in the E_2g2 phonon frequency of the pristine and reacted films suggests that the charge transfer between the K and BN bands is very small.