We successfully observed electron emission from hydrogenated diamond pin junction diodes with negative electron affinity during room temperature operation. The emissions started when the applied bias voltage produced flat-band conditions, where the capacitance–voltage characteristics showed carrier injection in the i-layer. In this low current injection region, the electron emission efficiency (η) of the pin junction diodes (p is top layer) was about 5 × 10− 5, while that of the nip diodes (n is top layer) was about 10− 8. With increasing diode current, both diodes showed an increase in η and a nonlinear increase in emission current. In the high current injection region with high diode current of 5–50 mA, both diodes had an emission current of almost 10 μA, where η of a pin junction diode was 0.18%, while that of a nip junction diode was 0.02%.

Note that η, which corresponds to the electron emission mechanism, depended on the diode current level.

This paper was originally published in Diamond and Related Materials (2011) 20, 917-921.

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