Highly conductive nitrogen-doped ultrananocrystalline diamond films with enhanced field emission properties: triethylamine as a new nitrogen source

Abstract

In this study, triethylamine (TEA) dissolved in the methanol was used as a liquid nitrogen source to synthesize nitrogen-doped ultrananocrystalline diamond (N-UNCD) films on silicon substrates via microwave plasma enhanced chemical vapor deposition (MPCVD). High electrical conductivity and superior electron field emission (EFE) properties can be obtained for the N-UNCD films. By simply controlling the substrate temperature (T_S), the microstructure and electrical conductivity, as well as EFE properties of these N-UNCD films can be manipulated. The electrical conductivity of the N-UNCD films grown at T_S = 830 °C reaches 1174 S cm⁻¹ and they exhibit superior EFE properties with low turn-on field of 3.4 V μm⁻¹ and large EFE current density of 8.0 mA cm⁻² at an applied field of 6.2 V μm⁻¹. Further increasing the T_S to 890 °C, the obtained N-UNCD films possess higher electrical conductivity of 1854 S cm⁻¹ but show slightly degraded EFE properties. The possible underlying mechanism for the high conductivity and enhanced EFE properties have been discussed in detail, based on the characterization of morphological, phase, and chemical bonding features. The N-UNCD films with excellent electrical conductivity and superior EFE properties have great potential for application as electron emitters for flat panel displays and other vacuum microelectron devices.