Sankaran Kamatchi Jothiramalingam, Yeh Chien-Jui, Hsieh Ping-Yen, Pobedinskas Paulius, Kunuku Srinivasu, Leou Keh-Chyang, Tai Nyan-Hwa, Lin I-Nan, Haenen Ken
Institute for Materials Research (IMO) , Hasselt University , Diepenbeek 3590 , Belgium.
IMOMEC, IMEC vzw , Diepenbeek 3590 , Belgium.
ACS Appl Mater Interfaces. 2019 Jul 17;11(28):25388-25398. doi: 10.1021/acsami.9b05469. Epub 2019 Jul 1.
Microstructural evolution of nanocrystalline diamond (NCD) nanoneedles owing to the addition of methane and nitrogen in the reactant gases is systematically addressed. It has been determined that varying the concentration of CH in the CH/H/N plasma is significant to tailor the morphology and microstructure of NCD films. While NCD films grown with 1% CH in a CH/H/N (3%) plasma contain large diamond grains, the microstructure changed considerably for NCD films grown using 5% (or 10%) CH, ensuing in nanosized diamond grains. For 15% CH-grown NCD films, a well-defined nanoneedle structure evolves. These NCD nanoneedle films contain sp phase diamond, sheathed with sp-bonded graphitic phases, achieving a low resistivity of 90 Ω cm and enhanced field electron emission (FEE) properties, namely, a low turn-on field of 4.3 V/μm with a high FEE current density of 3.3 mA/cm (at an applied field of 8.6 V/μm) and a significant field enhancement factor of 3865. Furthermore, a microplasma device utilizing NCD nanoneedle films as cathodes can trigger a gas breakdown at a low threshold field of 3600 V/cm attaining a high plasma illumination current density of 1.14 mA/cm at an applied voltage of 500 V, and a high plasma lifetime stability of 881 min is evidenced. The optical emission spectroscopy studies suggest that the C, CN, and CH species in the growing plasma are the major causes for the observed microstructural evolution in the NCD films. However, the increase in substrate temperature to ∼780 °C due to the incorporation of 15% CH in the CH/H/N plasma is the key driver resulting in the origin of nanoneedles in NCD films. The outstanding optoelectronic characteristics of these nanoneedle films make them suitable as cathodes in high-brightness display panels.
系统地研究了由于在反应气体中添加甲烷和氮气而导致的纳米晶金刚石（NCD）纳米针的微观结构演变。已确定在CH₄/H₂/N₂等离子体中改变CH₄的浓度对于调整NCD薄膜的形貌和微观结构具有重要意义。当在CH₄/H₂/N₂（3%）等离子体中使用1% CH₄生长NCD薄膜时，包含大的金刚石晶粒，而对于使用5%（或10%）CH₄生长的NCD薄膜，微观结构发生了显著变化，形成了纳米尺寸的金刚石晶粒。对于15% CH₄生长的NCD薄膜，形成了明确的纳米针结构。这些NCD纳米针薄膜包含sp³相金刚石，被sp²键合的石墨相包裹，实现了90 Ω·cm的低电阻率和增强的场电子发射（FEE）特性，即4.3 V/μm的低开启场，在8.6 V/μm的施加场下具有3.3 mA/cm²的高FEE电流密度以及3865的显著场增强因子。此外，一种利用NCD纳米针薄膜作为阴极的微等离子体装置能够在3600 V/cm的低阈值场下引发气体击穿，在500 V的施加电压下获得1.14 mA/cm²的高等离子体照明电流密度，并且证明具有881分钟的高等离子体寿命稳定性。光发射光谱研究表明，生长等离子体中的C、CN和CH物种是观察到的NCD薄膜微观结构演变的主要原因。然而，由于在CH₄/H₂/N₂等离子体中加入15% CH₄导致衬底温度升高至约780 °C是导致NCD薄膜中纳米针形成的关键驱动因素。这些纳米针薄膜出色的光电特性使其适合作为高亮度显示面板中的阴极。
