Abstract
In this work, a detailed field emission study of multi-walled carbon nanotubes (MWCNTs) grown on Si and Al coated Si substrates is reported. Morphological and microstructural studies of the films show higher entanglement of CNTs in the case of CNT/Si film as compared to CNT/Al/Si film. Raman studies show that the defect mediated peak (D) is substantially suppressed as compared to graphitic peak (G) resulting in significant reduction in ID/IG value in CNT/Al/Si film. Field emission (FE) current density of CNT/Al/Si film (∼25 mA/cm2) is significantly higher as compared to that of CNT/Si film (∼1.6 mA/cm2). A substantial improvement in temporal stability is also observed in CNT/Al/Si film. This enhancement in field emission current is attributed to strong adhesion between substrate and CNTs, low work function, high local field enhancement factor at the CNT tips and less entanglement of CNTs grown on Al/Si. The temporally stable CNT/Al/Si cold cathode can be a potential candidate to replace conventional electron sources in prototype devices.
Highlights
This enhancement in field emission current is attributed to strong adhesion between substrate and carbon nanotubes (CNTs), low work function, high local field enhancement factor at the CNT tips and less entanglement of CNTs grown on Al/Si
Due to their exceptionally high aspect ratio, stiffness, electrical conductivity and possibility of growth on various substrates, tremendous efforts have been made for replacing the conventional electron sources by CNT based cold cathodes for applications such as field emission displays (FEDs), field emission microscopes, X-ray tubes, microwave amplifiers etc.[13,14,15,16,17,18]
We report very long time stability measurement (∼16 hr) at higher current densities (∼16 mA/cm2) and high fields (4.6 V/μm) for CNT/Al/Si films
Summary
Carbon nanotubes (CNTs),[1] have attracted considerable attention of the scientific community because of their unique properties like high aspect ratio, good mechanical strength, thermal stability and chemical inertness.[2,3,4,5,6] a days, CNTs are used for electron sources, hydrogen storage, gas sensing, nano electronics, interconnects and solar-cell applications.[7,8,9,10,11,12] Due to their exceptionally high aspect ratio, stiffness, electrical conductivity and possibility of growth on various substrates, tremendous efforts have been made for replacing the conventional electron sources by CNT based cold cathodes for applications such as field emission displays (FEDs), field emission microscopes, X-ray tubes, microwave amplifiers etc.[13,14,15,16,17,18] In general, field emission process is governed by a theoretical model proposed by Fowler and Nordheim, which is based on quantum mechanical tunneling.[19]. (iii) vertically aligned CNT mesh,[23] CNT carpet[24] etc Another approach to improve FE properties is by decoration of CNTs apex by low work function materials[25] and introduction of various interlayers such as, Cr, W, Ti, Al, Au, Pd, Pt and Cu. The interlayers provide strong adhesion between CNTs and the substrates leading to better growth and restriction on formation of insulating silicide layers[26,27,28,29,30,31,32] at elevated temperatures. The current density (J) versus electric field (E) measurements were carried out up to a maximum E value of ∼5 V/μm for 5 cycles and all other field emission parameters of CNTs with and without interlayered Al are reported
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