Rawal Ishpal, Kumar Lalit, Tripathi Ravi Kant, Panwar Omvir Singh
Department of Physics, Kirori Mal College, and Department of Physics, Hindu College, University of Delhi, Delhi 110007, India.
Department of Applied Physics, School of Physical Sciences, B. B. A. University, Lucknow 226025, Uttar Pradesh, India.
ACS Omega. 2017 Nov 1;2(11):7515-7524. doi: 10.1021/acsomega.7b01274. eCollection 2017 Nov 30.
We present a new surface structure-dependent cold cathode material capable of sustaining high electron emission current suitable for next-generation low turn-on field-emission devices. The low turn-on electric field for electron emission in the cathode materials is critical, which facilitates the low-power room-temperature operation, a key factor required by the industrial sector. We demonstrate the facile synthesis of polypyrrole (PPy)/tin oxide (SnO)-based core-shell hybrid cold cathode materials for large area applications. The technique used here is based on a simple and economical method of surfactant-mediated polymerization. The coupled investigation of X-ray diffraction along with electron microscopy reveals the formation of rutile phase SnO nanoparticles of size ∼15 nm. These SnO nanoparticles act as nucleation sites for the growth of PPy nanofibers, resulting in encapsulated SnO nanoparticles in the PPy amorphous matrix. The coupling of spherical-shaped core-shell structures of PPy/SnO resulted into the particle train-like nanostructured form of the hybrid material. These core-shell structures formed the local p-n junction between the n-type SnO (core) and p-type PPy (shell). The long chains of these p-n junctions in nanofibers result in the modification of the electronic band structure of PPy, leading to a reduction in the work function of the electrons. The significant surface structural modification in PPy/SnO causes a prominent reduction in the turn-on electric field for electron emission in PPy/SnO nanocomposite (∼1.5 V/μm) as compared to the pure PPy (∼3.3 V/μm) without significant loss in current density (∼1 mA/cm). The mechanism of improved field-emission behavior and advantages of using such hybrid nanomaterials as compared to other composite nanomaterials have also been discussed in detail.
我们展示了一种新型的表面结构依赖性冷阴极材料，该材料能够维持适用于下一代低开启场发射器件的高电子发射电流。阴极材料中电子发射的低开启电场至关重要，这有利于低功耗室温运行，这是工业部门所需的关键因素。我们展示了用于大面积应用的聚吡咯（PPy）/氧化锡（SnO）基核壳混合冷阴极材料的简便合成方法。这里使用的技术基于一种简单且经济的表面活性剂介导聚合方法。结合X射线衍射和电子显微镜的研究揭示了尺寸约为15nm的金红石相SnO纳米颗粒的形成。这些SnO纳米颗粒充当PPy纳米纤维生长的成核位点，导致SnO纳米颗粒包裹在PPy无定形基质中。PPy/SnO球形核壳结构的耦合产生了混合材料的颗粒链状纳米结构形式。这些核壳结构在n型SnO（核）和p型PPy（壳）之间形成了局部p-n结。纳米纤维中这些p-n结的长链导致PPy电子能带结构的改变，从而导致电子功函数降低。与纯PPy（约3.3V/μm）相比，PPy/SnO中的表面结构显著改变导致PPy/SnO纳米复合材料中电子发射的开启电场显著降低（约1.5V/μm），且电流密度没有显著损失（约1mA/cm）。还详细讨论了场发射行为改善的机制以及与其他复合纳米材料相比使用这种混合纳米材料的优势。
