Gautier L-A, Le Borgne V, Delegan N, Pandiyan R, El Khakani M A
Institut National de la Recherche Scientifique, Centre Énergie, Matériaux et Télécommunications, 1650 Blvd. Lionel-Boulet, Varennes, Quebec J3X-1S2, Canada.
Nanotechnology. 2015 Jan 30;26(4):045706. doi: 10.1088/0957-4484/26/4/045706. Epub 2015 Jan 8.
A plasma-enhanced chemical vapor deposition (PECVD) process was adapted to alter the growth of multiwall carbon nanotubes (MWCNTs) so that graphene sheets grow out of their tips. Gold nanoparticle (Au-NP) decoration of graphenated MWCNTs (g-MWCNTs) was obtained by subsequent decoration by a pulsed laser deposition (PLD) process. By varying the number of laser ablation pulses (N(Lp)) in the PLD process, we were able to control the size of the gold nanoparticles and the surface coverage of the decorated g-MWCNTs. The presence of Au-NPs, preferentially located at the tip of the g-MWCNTs emitters, is shown to significantly improve the field electron emission (FEE) properties of the global g-MWCNT/Au-NP nanohybrid films. Indeed, the electric field needed to extract a current density of 0.1 μA cm(-)(2) from the g-MWCNT/Au-NP films was decreased from 2.68 V μm(-1) to a value as low as 0.96 V μm(-1). On the other hand, UV photoelectron spectroscopy (UPS) characterization revealed a decrease in the global work function of the Au-decorated g-MWCNT nanohybrids compared to that of bare g-MWCNT emitters. Surprisingly, the work function of g-MWCNT was found to decrease from 4.9 to 4.7 eV with the addition of Au-NPs-a value lower than the work function of both materials worth 5.2 and 4.9 eV for gold and g-MWCNT, respectively. Our results show that the N(Lp) dependence of the FEE characteristics of the g-MWCNT/Au-NP emitters correlates well with their work function changes. Fowler-Nordheim-theory-based calculations suggest that the significant FEE enhancement of the emitters is also caused by the Au-NPs acting as nanoscale electric field enhancers.
采用等离子体增强化学气相沉积（PECVD）工艺来改变多壁碳纳米管（MWCNT）的生长方式，以使石墨烯片从其尖端生长出来。通过随后的脉冲激光沉积（PLD）工艺对石墨烯化的MWCNT（g-MWCNT）进行金纳米颗粒（Au-NP）修饰。通过改变PLD工艺中的激光烧蚀脉冲数（N(Lp)），我们能够控制金纳米颗粒的尺寸以及修饰后的g-MWCNT的表面覆盖率。结果表明，优先位于g-MWCNT发射体尖端的Au-NP的存在显著改善了整体g-MWCNT/Au-NP纳米杂化膜的场电子发射（FEE）特性。实际上，从g-MWCNT/Au-NP膜中提取0.1 μA cm⁻²电流密度所需的电场从2.68 V μm⁻¹降低到了低至0.96 V μm⁻¹的值。另一方面，紫外光电子能谱（UPS）表征显示，与未修饰的g-MWCNT发射体相比，Au修饰的g-MWCNT纳米杂化物的整体功函数降低。令人惊讶的是，发现添加Au-NP后g-MWCNT的功函数从4.9 eV降至4.7 eV——该值分别低于金和g-MWCNT这两种材料的功函数5.2 eV和4.9 eV。我们的结果表明，g-MWCNT/Au-NP发射体的FEE特性对N(Lp)的依赖性与其功函数变化密切相关。基于福勒-诺德海姆理论的计算表明，发射体FEE的显著增强也是由作为纳米级电场增强剂的Au-NP引起的。
