Electron affinity and field emission characteristics of boron carbon nitride film

Boron nitride (BN) and boron carbon nitride (BCN) films with various carbon composition ratios are synthesized by plasma-assisted chemical vapor deposition (PACVD). The electron affinity is estimated from the difference between the threshold energy of the photoelectron yield and the bandgap energy. The negative electron affinity is observed for the BN film. The electron affinity varies from the negative value of the hexagonal boron nitride (h-BN) to 1.2 eV of the BCN film with increasing carbon (C) composition ratio of 29%. The positive electron affinity is estimated to be as low as 0.7 eV for the BCN film with C composition ratio of 18%. Field emission characteristics of BN and BCN nanofilms are investigated. No degradation of the field emission characteristics occurs for the BCN nanofilms with C composition ratio lower than 18%. On the other hand, the turn-on electric field increases rapidly for the BCN nanofilms with C composition ratio higher than 20%. An increase of turn-on electric field is possibly due to an enhancement of the surface potential barrier height.