Electronic Materials Letters

, Volume 14, Issue 2, pp 173–180 | Cite as

Investigation of Electron Transport Across Vertically Grown CNTs Using Combination of Proximity Field Emission Microscopy and Scanning Probe Image Processing Techniques

  • Sadhu Kolekar
  • Shashikant P. Patole
  • Ji-Beom Yoo
  • Chandrakant V. Dharmadhikari


Field emission from nanostructured films is known to be dominated by only small number of localized spots which varies with the voltage, electric field and heat treatment. It is important to develop processing methods which will produce stable and uniform emitting sites. In this paper we report a novel approach which involves analysis of Proximity Field Emission Microscopic (PFEM) images using Scanning Probe Image Processing technique. Vertically aligned carbon nanotube emitters have been deposited on tungsten foil by water assisted chemical vapor deposition. Prior to the field electron emission studies, these films were characterized by scanning electron microscopy, transmission electron microscopy, and Atomic Force Microscopy (AFM). AFM images of the samples show bristle like structure, the size of bristle varying from 80 to 300 nm. The topography images were found to exhibit strong correlation with current images. Current–Voltage (I–V) measurements both from Scanning Tunneling Microscopy and Conducting-AFM mode suggest that electron transport mechanism in imaging vertically grown CNTs is ballistic rather than usual tunneling or field emission with a junction resistance of ~10 kΩ. It was found that I–V curves for field emission mode in PFEM geometry vary initially with number of I–V cycles until reproducible I–V curves are obtained. Even for reasonably stable I–V behavior the number of spots was found to increase with the voltage leading to a modified Fowler–Nordheim (F–N) behavior. A plot of ln(I/V3) versus 1/V was found to be linear. Current versus time data exhibit large fluctuation with the power spectral density obeying 1/f2 law. It is suggested that an analogue of F–N equation of the form ln(I/Vα) versus 1/V may be used for the analysis of field emission data, where α may depend on nanostructure configuration and can be determined from the dependence of emitting spots on the voltage.

Graphical Abstract


Field electron emission Carbon nanotubes Field enhancement factor 



SK would like to acknowledge UGC for Junior Research Fellowship (JRF) and CNQS, Savitribai Phule Pune University for technical assistantship.


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Copyright information

© The Korean Institute of Metals and Materials 2018

Authors and Affiliations

  1. 1.Department of PhysicsSavitribai Phule Pune UniversityPuneIndia
  2. 2.School of Advanced Materials Science and EngineeringSungkyunkwan UniversitySuwonKorea
  3. 3.Department of PhysicsUniversity of South FloridaTampaUSA
  4. 4.Department of Materials Science and EngineeringKing Abdullah University of Science and TechnologyThuwalSaudi Arabia
  5. 5.Indian Institute of Science Education and ResearchPashan, PuneIndia

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