Synthesis of a room temperature stable 12CaO•7Al2O3 electride from the melt and its application as an electron field emitter
Synthesis of a room temperature stable 12CaO•7Al2O3 electride from the melt and its application as an electron field emitter
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DOI：
10.1021/cm052367e
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发表时间：
2006-04-04
影响因子：
8.6
通讯作者：
Hosono, H
中科院分区：
文献类型：
--
作者：
Kim, SW;Toda, Y;Hosono, H
通过在金属钙蒸气中对绝缘的12CaO中心点7Al(2)O(3) （C12A7）单晶进行热退火，制备了室温稳定的电极。本文报道了一种简单直接的合成多晶C12A7电化物（C12A7:e(-)）的方法；熔体在还原气氛中凝固，真空中含缺氧成分的玻璃结晶。碳相关阴离子（C-2-(2)）可能在凝固过程中作为C12A7相形成的模板，在冷却过程中可能自发地从晶格中释放出来，在晶格中留下可移动的电子。此外，在结晶过程中，玻璃中的C-2-(2)离子可能在C12A7:e-的形成中起重要作用。在300 K时，多晶C12A7:e（-）的电导率高达5 S中心点cm(-1)，对应于3 × 10(19) cm（-3）的电子浓度和0.1 cm(2)中心点V-1中心点S-1的迁移率，与单晶C12A7:e（-）的迁移率几乎相等。在电场强度为2.4 x 10(5) V中心点cm（-1）的情况下，从多晶C12A7:e（-）的平坦表面发射出的电子场密度为12 μ A中心点cm（-2）的大电流，功函数为0.6 eV。这些简单的合成方法使得大量高效地生产该电极成为可能，这将促进C12A7:e（-）的研究，为包括冷电子发射在内的各种应用铺平道路。
A room temperature (RT) stable electride was realized by thermally annealing an insulating 12CaO center dot 7Al(2)O(3) (C12A7) single crystal in a calcium metal vapor. Here we report a simple and direct method for synthesizing polycrystalline C12A7 electride (C12A7:e(-)); the solidification of a "melt" in a reducing atmosphere and the crystallization of a "glass" with an oxygen-deficient composition in a vacuum. The carbon-related anion (C-2-(2)) presumably serves as the template for the formation of the C12A7 phase in the solidification process and may be spontaneously released from the lattice during the cooling process, leaving mobile electrons in the lattice. Also the C-2-(2) ions accommodated in the glass may play a significant role in the formation of C12A7:e- during the crystallization. The polycrystalline C12A7:e(-) exhibits an electrical conductivity up to 5 S center dot cm(-1) at 300 K, which corresponds to an electron concentration of similar to 3 x 10(19) cm(-3) and a nearly equal mobility of similar to 0.1 cm(2)center dot V-1 center dot S-1 to that of the single crystalline C12A7:e(-). A large current density of similar to 12 mu A center dot cm(-2) is obtained in the electron field emission from a flat surface of the polycrystalline C12A7:e(-) with a work function of similar to 0.6 eV for an applied electric field of 2.4 x 10(5) V center dot cm(-1). These simple synthetic methods make it possible to produce efficiently the electride in large volume, which will facilitate the C12A7:e(-) research, paving a way for various applications including cold electron emission.