Study of thermal-field emission properties and investigation of temperature dependent noise in the field emission current from vertical carbon nanotube emitters

摘要

We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well-defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The realtime field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD) in order to understand the effect of temperature on distribution of electron emission spots and ring like structures in Field Emission Microscope (FEM) image. The FEM images could be used to calculate the total number of emitters per cm(2) for electron emission. The calculated number of emitters per cm(2) from FEM image is typically, 4.5 x 10(7) and the actual number emitters per cm(2) present as per Atomic Force Microscopy (AFM) data is 1.2 x 10(12). The measured Current-Voltage (I -V) characteristics exhibit non linear Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current were recorded at different temperatures and Fast Fourier transformed into temperature dependent power spectral density. The latter was found to obey power law relation S(f) = A(I-delta/f(xi)), where delta and xi are temperature dependent current and frequency exponents respectively. (C) 2017 Published by Elsevier B.V.