Relying on the obtained theoretical and expenmental results the electron work function from the nanotube carbon film was &mated. It was shown that these structures have a low work function, substantially lower than for graphite. Under estimation we regarded the influence of the film surface relief on its emission ability.Even first investigation results for electron field emission from the thin films containing nanotube carbon structures we developed [l] have shown that these films are promising for emission electronics [l-31. In the present paper we assess the work function of electrons from this material on the base of analyzing the experimentai results for field and thermal emission from the surface of thin nanotube carbon cluster (tubelene) films [4-51 and theoretical calculations.The studies of the nanotube film surface disclose [l-51 that they have an extremely appropriate geometry to construct field emitters when tubelenes are aligned orthogonally to the substrate surface. We have investigated two tubelene types [3-61. The former tubelenes are one-layer tubes of 8 A -1 1 A diameter which are twisted into 100 A -300 A diameter ropes. The letters represent multilayer tubes of 100 A -300 A diameter closed with the cap at the top. We call them, by convention, A and B tubelenes. The mean height of a single tubelene is 100 A .Since the tubelene conductivity is great (about 100 S. cm-1) and the tip radius is very small, a strong electric field arises at the top of the tubelene with applying the potential difference. between the anode and the film under study. This circumstance seems to be one of the factors defining the onset of electron field emission from these carbon films with comparatively low accelerating voltages. Numerical experiments were conducted to study the geometry of the tubelene film. The conductivity of electric field at the emitting surface of the tubelene was calculated using the method of finite elements [7]. So, we estimate, for example, the gain at the tubelene top for a height of a single tubelene of 100 A , its diaqeter of 30 A and an anode-cathode spacing of 20 mkm. With a zero potential at the cathode and the accelerating voltage at the anode U,=lOOO V the maximum field intensity at the top of the tubelene is 0.4 107 V/cm-3. Thus, with a specified geometry of the tubelene film a maximum gain makes up 10. This gain is insufficient to account for the experimentally obtained values of field emission current [4] (in experiment the current was 100 mkm with Ua=lOO V and the anode diameter was 0.6 mkm).Consequently the emission ability of the carbon tubelene film is due to one further factor, and namely, a low work function.In connection with this the Fowler-Nordheim formula was used to calculate the work function versus the number of tubelenes placed at the 0.6 mm diameter cathode. Computation was performed with regard to experimental field emission currents for a theoretically calculated gain at the tubelene tops. Figure 1 presents the work function cp versus Zn (N,JN) where N,, is the maxim...

Mailto: torasoire. renetruField emission from.nanotube film is accompanied by a number of phenomena occumng both inside film and at its surface. Every of them influence on field emission properties and the cathode lifetime. In the present report the peculiarities of electron transport inside nanotube films under the influence of electric and thermal fields are considered.The geometry changes of nanotubes during field emission which lead to nanotube work function variations are estimated. The threshold field value, at which nanotube breakdown has been obtained. The possibility of surface states presence at the fildvacuum interface is examined.Special attention as paid to the fluctuation spectrum analysis of emission current, which come from the relaxation oscillations of separate emission centers. This analysis allows one to study the details of electron transport inside films, and shows the ways to decrease the cathode noises.The main results of investigation of thermal processes that occur during field emission in different carbon macromolecules are also given in the report. Joule heat release from nanotubes, is studied in details, Nottingham and Peltier effects are considered, and heat conduction and radiation of nanotubes were taken in account. Carbon nanotube heat conduction coefficient vs. their diameter, chirality and number of layers is theoretically investigated.-5 1 -0-7803-8437-7/04/$20.00 02004 IEEE.