Abstract
A comparative study of electron field emission (FE) property of pristine mutiwalled carbon nanotubes (p-CNTs), zinc (Zn) coated CNTs (Zn-CNT), zinc oxide (ZnO) coated CNTs (ZnO-CNT) is reported. CNTs were synthesized on p-type Si (100) by microwave plasma enhanced chemical vapor deposition (MPECVD) method and the sample was divided into three parts. On two of these parts, a thin layer (~ 4nm) of Zn film was deposited. One of these (Zn-CNT) was kept for analysis and the other one was annealed in oxygen (O2) atmosphere at 520° C for 60 minutes to get ZnO coated CNT film (ZnO-CNT). Scanning electron microscope (SEM) analysis confirmed CNT formation as well as Zn and ZnO coating on the top of p-CNT films. Further, energy-dispersive X-ray spectroscopy (EDX) results confirmed the presence of zinc and oxygen in these two samples. A detailed field emission study performed in these films give following results: (i) lowest turn-on field (electric field required to produce 10 μA/cm 2 current density) and threshold fields (electric field required to produce 100 μA/cm 2 current density) for pristine sample (3.3 V/μm and 5.1 V/μm respectively), followed by ZnO-CNT sample (3.7 V/μm and 6.3 V/μm respectively); (ii) highest temporal stability in current density versus field (J-E characteristics) in ZnO-CNT film as compared to other two, (iii) highest field enhancement factor in ZnO-CNT films as compared to other two. The FE results are correlated with microstructures of the samples as revealed by micro-Raman spectroscopy and transmission electron microscopy (TEM) studies. Copyright © 2013 VBRI press.
Highlights
The unique fundamental physical properties and potentially high-technology application made one dimensional (1D) nanostructured materials in the center of attraction for a long time [1]
In Fig. 3(B) and 3(C) a clear change in morphology is observed after coating of Zn on top of pristine mutiwalled carbon nanotubes (p-carbon nanotubes (CNTs)) films followed by oxidation at high temperature
The results show that the cf is quite low in p-CNT film, whereas in zinc coated on the top of pCNTs (Zn-CNT) cf enhances appreciably indicating deterioration of Field emission (FE) current stability
Summary
The unique fundamental physical properties and potentially high-technology application made one dimensional (1D) nanostructured materials in the center of attraction for a long time [1]. Field emission (FE) is a quantum mechanical process where electrons near the Fermi level can tunnel through the energy barrier and escape to the vacuum level under a high enough electric field. These unique properties of CNTs make them remarkable field emitters. Based on density functional theory (DFT), Zhang et al have reported that ZnO -CNT nanocomposite could be used as a good field emitter (in terms of emission current, enhancement factor and stability) and a potential candidate of FE based devices [24]. There are a numbers of methods to synthesize of CNTs like arc discharge method [2], thermal vapor deposition method [25,26], microwave enhanced plasma chemical vapor deposition (MWPECVD) [27], pulsed laser deposition method (PLD) [28], plasma enhanced chemical vapor deposition method [29] etc
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