Department of Physics, The George Washington University , 725 21st Street NW, Washington, D.C. 20052, United States.
Euclid TechLabs , 365 Remington Boulevard, Bolingbrook, Illinois 60440, United States.
ACS Appl Mater Interfaces. 2017 Sep 27;9(38):33229-33237. doi: 10.1021/acsami.7b07062. Epub 2017 Sep 13.
In this paper, we study the effect of the actual, locally resolved, field emission area on electron emission characteristics of uniform planar conductive nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) field emitters. High resolution imaging experiments were carried out in a field emission microscope with a specialty imaging anode screen such that electron emission micrographs were taken concurrently with measurements of I-V characteristics. An automated image processing algorithm was applied to process the extensive imaging data sets and calculate the emission area per image. It was routinely found that field emission from as-grown planar (N)UNCD films was always confined to a counted number of discrete emitting centers across the surface, which varied in size and electron emissivity. It was established that the actual field emission area critically depends on the applied electric field and that the field emission area and overall electron emissivity improve with the sp-fraction present in the film, irrespective of the original substrate roughness or morphology. Most importantly, when as-measured I-E characteristics were normalized by the electric field-dependent emission area, the resulting j-E curves demonstrated a strong kink and departed from the Fowler-Nordheim law, finally saturating at a value on the order of 100 mA/cm. This value was nearly identical for all studied films regardless of substrate. It was concluded that the saturation value is specific to the intrinsic fundamental properties of (N)UNCD.
在本文中，我们研究了实际的、局部解析的场发射区域对均匀平面导电掺氮的 ultrananocrystalline 金刚石（(N)UNCD）场发射器电子发射特性的影响。在带有特殊成像阳极屏的场发射显微镜中进行了高分辨率成像实验，使得可以同时进行电子发射显微照片和 I-V 特性测量。应用自动化图像处理算法处理大量成像数据集并计算每个图像的发射面积。通常发现，生长的平面 (N)UNCD 薄膜的场发射总是局限于表面上的离散发射中心的数量，这些中心的大小和电子发射率各不相同。已经确定，实际的场发射区域取决于所施加的电场，并且场发射区域和整体电子发射率随着薄膜中的 sp 分数的增加而提高，而与原始衬底的粗糙度或形态无关。最重要的是，当用依赖于电场的发射面积对实测的 I-E 特性进行归一化时，得到的 j-E 曲线表现出强烈的拐点，并偏离了 Fowler-Nordheim 定律，最终在约 100 mA/cm 的值处饱和。该值对于所有研究的薄膜都几乎相同，而与衬底无关。得出的结论是，饱和值是 (N)UNCD 的固有基本特性所特有的。
