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

• Published in: Surface science Vol. 664; pp. 76 - 81
• Main Authors: Kolekar, Sadhu, Patole, S.P., Patil, Sumati, Yoo, J.B., Dharmadhikari, C.V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2017; Elsevier BV
• Subjects: Atomic force microscopes; Atomic force microscopy; Atomic properties; Carbon nanotubes; Charge coupled devices; Current voltage characteristics; Electron emission; Electrons; Emission analysis; Emitters; Emitters (electron); Field emission microscopy; Mathematical analysis; Microscopy; Nanotubes; Noise in emission current etc; Spots; Studies; Temperature; Temperature effects; Thermal-field emission; Vertical carbon nanotubes; Vertical carbon nanotubes; Noise in emission current etc; Thermal-field emission
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2017.05.002

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 1500K. The real-time field electron emission images at room temperature and 1500K 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 cm2 for electron emission. The calculated number of emitters per cm2 from FEM image is typically, 4.5 × 107 and the actual number emitters per cm2 present as per Atomic Force Microscopy (AFM) data is 1.2 × 1012. 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(Iδ/fξ), where δ and ξ are temperature dependent current and frequency exponents respectively. Figure: shows strong enhancement in the field emission current as well as new electron emission site due to temperature (a) AFM morphology for vertical CNT, (b) FEM image of vertical CNT at 1500K and applied voltage of 1400V, (c) I-V plots at RT, 1500K, power spectral density versus temperature used for activation energy calculation [Display omitted] •Thermal-field emission investigations from vertical CNT emitters have been carried out using Field Emission Microscopy.•Increase in temperature leads to enhanced electron emission from individual sites as well as opening of new sites.•The temperature dependent power spectral density of emission current was found to obey the power law: S(f)=A(Iδ/fξ).•Estimated noise activation energy of ≈3.4eV from Arrhenius plot of PSD shed light on the mechanism of noise generation.