Room-Temperature Negative Differential Resistance in Amorphous Carbon: The Role of Electron Trapping Defects at Device Interfaces

Hysteresis and NDR have been observed in the room-temperature current–voltage characteristics of lateral devices featuring planar graphitic electrodes separated by a nitrogen-doped amorphous carbon (a-CN
_x
) layer. The devices were fabricated using energetic physical vapor deposition and electron-beam lithography. Devices formed on a-CN
_x
layers deposited with N
₂
pressure of 0.10 mTorr exhibited NDR. This NDR occurred at a well-defined voltage/electric field but only after the voltage of the opposite polarity was applied. Based on this behavior, a model is proposed in which the NDR occurs by field-induced trapping/detrapping at one of the graphite/a-CN
_x
interfaces within the device. The results of this investigation highlight the importance of interfaces and defects in determining the characteristics of a-C memristive devices.