Electron field emission from the semimetallic TiO2 nanotube arrays

• Semimetallic TiO2 nanotube arrays are formed by a carbonization treatment.
• Field emission of semimetallic TiO2 nanotube arrays has been first investigated.
• A low turn-on field of 3.0 V/μm and a threshold field of 7.0 V/μm are obtained.
• This turn-on field value is enough for potential use in field emission devices.

To enhance field-emission (FE) properties, as-prepared TiO2 nanotube arrays (TNAs) successfully transformed from semiconductor into semimetal by a carbonization treatment under an argon/acetylene flux at 750 °C. After semimetallic transformation, the TNAs maintain tubular morphology, however, their surface become rougher. Especially, their electronic structures are significantly improved. A low turn-on field of 3.0 V/μm and a threshold field of 7.0 V/μm are obtained. Such improvements of FE properties can be mainly attributed to the enhancements of electrical property and rough surface morphology.