Field emission characteristics of carbon nano tubes under varying background pressure conditions

In general, for plasma switches, the initiation of the plasma is critical and this is usually achieved by a ¿trigger¿ scheme. The seed electrons needed to initiate a breakdown can be generated by several means such as thermionic, field or optical emission. While the thermionic emission has been used mainly in vacuum tubes and is a mature technology, field emission (or cold-cathode electron emission) has been the subject of recent studies and technology. The efficiency of these seed electron emission determines how well the plasma switch can close or open. It is known that the carbon nano tubes (CNTs) have excellent field emission characteristic under high vacuum pressure and they have been considered as prima candidates as cold-cathode electron emitters. However, to the authors´ knowledge their electron emission characteristics in elevated pressures higher than vacuum have not been measured. The purpose of this experiment is to observe the field emission characteristics of several CNT samples, namely random Multi-Wall Carbon Nano Tube (MWCNT), Aligned MWCNT and random Single-Wall Carbon Nano Tube (SWCNT) in background pressures ranging from 10^-6 Torr to 1 Torr of He and air. The comparison of SEM images of the samples before and after the experiments is presented to demonstrate that these samples can be operated under these various vacuum conditions.