Zulkharnay Ramiz, Fox Neil A, May Paul W
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
School of Physics, H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK.
Small. 2024 Nov;20(48):e2405408. doi: 10.1002/smll.202405408. Epub 2024 Sep 2.
Diamond with negative electron affinity (NEA) and low work function surfaces are suggested as a suitable material for electron-generation applications in vacuum, in particular, as the emitter electrode in thermionic energy converters. Such NEA surfaces can be fabricated by evaporating and then annealing submonolayers of a suitable metal in vacuo onto bare or oxidized diamond. Among the metals studied, scandium termination of bare diamond (100) and (111) surfaces is recently reported to give the largest NEA values reported to date for a metal-diamond system, as well as being thermally stable to 900 °C. It is now shown that preoxidized (100) diamond functionalized with 0.25 monolayers of Sc also produces a large NEA value of -1.02 eV with low work functions (<3.63 eV). Moreover, this surface is thermally stable to 700 °C and can withstand exposure to air for extended periods. Here, the structural and electronic properties of this Sc─O-functionalized diamond surface are characterized in detail using a variety of surface-science techniques. The results suggest that this material may be the ideal candidate for the fabrication of commercial thermionic energy conversion devices, e.g., for solar-power generation, as well as for various other electronic devices that rely upon electron emission.
具有负电子亲和势（NEA）和低功函数表面的金刚石被认为是一种适用于真空电子产生应用的材料，特别是作为热离子能量转换器中的发射电极。这种NEA表面可以通过在真空中将合适金属的亚单层蒸发然后退火到裸露或氧化的金刚石上来制备。在所研究的金属中，最近报道裸露的金刚石（100）和（111）表面的钪终止能给出金属 - 金刚石系统迄今为止报道的最大NEA值，并且在900°C下热稳定。现在表明，用0.25单层钪功能化的预氧化（100）金刚石也能产生-1.02 eV的大NEA值且功函数较低（<3.63 eV）。此外，该表面在700°C下热稳定，并且能够长时间耐受空气暴露。在此，使用各种表面科学技术详细表征了这种钪 - 氧功能化金刚石表面的结构和电子性质。结果表明，这种材料可能是制造商业热离子能量转换装置（例如用于太阳能发电）以及各种其他依赖电子发射的电子器件的理想候选材料。
