Preparation And Optimization Of Field Emission Cathode Of Carbon Nanotubes

The discovery of carbon nanotubes (CNTs) attracts many scientists' attention. CNTs can be used in many fields due to its excellent properties of mechanics, electricity. CNTs has a high aspect ratio, low work function, good electrical conductivity and nanometer tip, which can emit electrons at low voltage. So CNTs is considered as a good field emission cathode and has been used in electron beam device such as SEM and TEM. It is believed that CNTs will have a widely application in field emission display.In this paper CNT film was deposited on metal substrate by low temperature and low pressure chemical vapor deposition (CVD). Field emission cathode was made by thin-film and thick-film process. By varying deposition and processing conditions, the optimized conditions for field electron emission were found.The major results are listed as follows.1 Field emission properties of CNTs cathode made by screen printing1) Thick CNT film was grown on nickel plate for 60 minutes at a certain condition. CNTs has a large diameter and is grown uniformly and randomly oriented with many defects. Field emission cathode was made by screen printing.2) By varying conditions such as acetylene flow rate, concentration ratio of CNTs and organic binder, CNTs deposited on different surfaces of nickel plate, the optimum condition for electron field emission was found. When acetylene flow rate was 70sccm, concentration ratio was 1g to 8ml, the field emission properties of CNTs deposited on the surface of nickel plate were the best. At this condition, turn-on field of 4.19V/μm, emission current density of 37μA/cm~2 at the field of 5.88V/μm and emission spot density of 10~3/cm~2 were achieved.3) Annealing processing was used to increase the field emission properties of CNT cathode. At the temperature of 300°C for 8 minutes heat treatment in the ambient, the field emission properties of CNT cathode were the best. At this condition, turn-on field of 3.95V/μm, emission current density of 43μA/cm~2 and emission spot density of 2×10~3 /cm~2 were achieved. CNTs density on cathode surface was decreased so as to eliminate screening effect between CNTs. So CNTs density can be changed by annealing processing and the field emission properties of CNT cathode were improved.2 Field emission properties of CNT film on nickel plate as field emission cathode...