Saravanan Adhimoorthy, Huang Bohr-Ran, Sankaran Kamatchi Jothiramalingam, Kunuku Srinivasu, Dong Chung-Li, Leou Keh-Chyang, Tai Nyan-Hwa, Lin I-Nan
Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology , Taipei 106, Taiwan R.O.C.
ACS Appl Mater Interfaces. 2014 Jul 9;6(13):10566-75. doi: 10.1021/am502231d. Epub 2014 Jun 27.
Microstructural evolution of ultrananocrystalline diamond (UNCD) films in the bias-enhanced nucleation and growth (BEN-BEG) process in CH4/Ar plasma is systematically investigated. The BEN-BEG UNCD films possess higher growth rate and better electron field emission (EFE) and plasma illumination (PI) properties than those of the films grown without bias. Transmission electron microscopy investigation reveals that the diamond grains are formed at the beginning of growth for films grown by applying the bias voltage, whereas the amorphous carbon forms first and needs more than 30 min for the formation of diamond grains for the films grown without bias. Moreover, the application of bias voltage stimulates the formation of the nanographite phases in the grain boundaries of the UNCD films such that the electrons can be transported easily along the graphite phases to the emitting surface, resulting in superior EFE properties and thus leading to better PI behavior. Interestingly, the 10 min grown UNCD films under bias offer the lowest turn-on field of 4.2 V/μm with the highest EFE current density of 2.6 mA/cm(2) at an applied field of 7.85 V/μm. Such superior EFE properties attained for 10 min bias grown UNCD films leads to better plasma illumination (PI) properties, i.e., they show the smallest threshold field of 3300 V/cm with largest PI current density of 2.10 mA/cm(2) at an applied field of 5750 V/cm.
系统研究了超纳米晶金刚石（UNCD）薄膜在CH4/Ar等离子体中偏压增强形核与生长（BEN-BEG）过程中的微观结构演变。与无偏压生长的薄膜相比，BEN-BEG UNCD薄膜具有更高的生长速率、更好的电子场发射（EFE）和等离子体照明（PI）性能。透射电子显微镜研究表明，对于施加偏压电压生长的薄膜，在生长开始时形成金刚石晶粒，而对于无偏压生长的薄膜，首先形成非晶碳，并且需要超过30分钟才能形成金刚石晶粒。此外，施加偏压电压促进了UNCD薄膜晶界中纳米石墨相的形成，使得电子能够沿着石墨相轻松传输到发射表面，从而产生优异的EFE性能，进而导致更好的PI行为。有趣的是，在偏压下生长10分钟的UNCD薄膜在7.85 V/μm的外加电场下具有4.2 V/μm的最低开启场和2.6 mA/cm²的最高EFE电流密度。对于在偏压下生长10分钟的UNCD薄膜所获得的这种优异的EFE性能导致了更好的等离子体照明（PI）性能，即它们在5750 V/cm的外加电场下显示出3300 V/cm的最小阈值场和2.10 mA/cm²的最大PI电流密度。
