Rajkumar Patra; Anjali Singh; V. D. Vankar; S. Ghosh
Abstract
We report a simple and detailed simulation based analysis of an experimental field emission (FE) image captured on a phosphor coated indium tin oxide (ITO)/glass plate due to the electron emission from a multiwalled carbon nanotube (MWCNT) film. Emission intensity versus effective emissive area, number ...
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We report a simple and detailed simulation based analysis of an experimental field emission (FE) image captured on a phosphor coated indium tin oxide (ITO)/glass plate due to the electron emission from a multiwalled carbon nanotube (MWCNT) film. Emission intensity versus effective emissive area, number of CNTs present in the film contributing emission process and number density of MWCNTs at high field (during FE process) along with other FE parameters viz. turn on field, threshold field are determined, which agrees well with experimental results. Over estimation of calculated value over experimental results is realized with creation of new emission sites at high electric field due to combined effect of divergence of electron within electrode because of electron-air molecule collision, assumption of evenly placement of emitters during calculation, damages and/or tear-off of emitters at high electric field, contribution of adsorbates of MWCNT walls and the energy loss due to absorption of phosphor atom. This analysis renders a unique way to analyze field emission data and supports the theoretical formulation to evaluate the best possible values of FE parameters.
Deepak Chhikara; K. M. K. Srivatsa; M. Senthil Kumar; Preetam Singh; Sourav Das; O. S. Panwar
Abstract
Vertically well aligned and highly dense ZnO nanowires (NWs) have been grown on biaxially textured Ni substrates by a simple thermal evaporation technique over a large area without using any catalyst. The grown ZnO NWs have crystallized in wurtzite hexagonal structure and have grown along [0001] direction. ...
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Vertically well aligned and highly dense ZnO nanowires (NWs) have been grown on biaxially textured Ni substrates by a simple thermal evaporation technique over a large area without using any catalyst. The grown ZnO NWs have crystallized in wurtzite hexagonal structure and have grown along [0001] direction. It is also observed that the degree of vertical alignment of NWs increases with increasing growth temperature. An intense photoluminescence peak at 383 nm with a negligible deep band emission revealed the good crystalline quality of ZnO NWs. Field emission properties of the grown NWs have been examined and a field enhancement factor of 1573 has been obtained, indicating the suitability of grown nanowires for field emission applications.
Rajkumar Patra; Himani Sharma; Swati Singh; S. Ghosh; V. D. Vankar
Abstract
Designing an efficient field emission source requires theoretical optimization of electron emitters’ geometrical distribution over the surface for its best performance in terms of current density. Seven and nineteen bundles of CNT arrays arranged in different models are analysed in detail using ...
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Designing an efficient field emission source requires theoretical optimization of electron emitters’ geometrical distribution over the surface for its best performance in terms of current density. Seven and nineteen bundles of CNT arrays arranged in different models are analysed in detail using a computational theory in CST studio suite software based on the particle tracking mode. A three dimensional model has been employed to calculate FE properties with high accuracy. Simulations were carried out for a particular number of CNTs of constant height and radius located at fixed distances from each other and arranged in different geometrical patterns. Among all patterns, rectangular arrangement of CNTs is found to produce the maximum current. The edge effect and screening effect are incorporated in calculating total emission current and are found to diminish the contribution of inner rings 10% or less than that of maximum contribution. These findings can be employed as guideline to fabricate pattered CNT structures experimentally for industry applications.
Rajkumar Patra; Santanu Ghosh; Himani Sharma; Vasant D. Vankar
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 ...
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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.
