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采用Cs源持续、O源断续的交替方法成功激活了GaN光电阴极,原位测试了透射模式下的光谱响应曲线,获得了透射模式下高达13%的量子效率.从一维定态薛定谔方程入手,得到了GaN真空面电子源材料的电子透射系数的表达式.对于一定形状的阴极表面势垒,电子透射系数决定于入射电子能量、表面势垒的高度和宽度.根据具有负电子亲和势(NEA)特性的透射式GaN光电阴极的能带及Cs,O覆盖过程中阴极表面势垒的变化情况,结合双偶极层[CaN(Mg):Cs]:O-Cs表面模型,分析了GaN真空面电子源材料NEA特性的形成原因.研究表明:Cs,O激活过程中形成的双偶极层对电子逸出起促进作用,双偶极层的形成是材料表面真空能级下降的原因.GaN photocathode is fully activated by employing a continuous Cs source and an alternate O source. The quantum efficiency curve of transmission-mode photocathode is tested in situ. The quantum efficiency reaches up to 13% in transmission-mode. According to the one-dimensional Schrdinger equation, the electron transmission coefficient formula of GaN vacuum electron source material is deduced. For a certain profile of photocathode surface potential barrier, the electron transmission coefficient relates to the incident electron energy, the height and the width of the surface potential. The energy band of transmission-mode negative electron affinity (NEA) GaN photocathode and the change of surface barrier in the deposit course of Cs,O are given. Using the double dipole layer surface model [CaN(Mg):Cs]:O-Cs, the NEA property formation of GaN vacuum electron source material is analyzed. The results show that the double dipole layer formed in the activation course of Cs,O is conducible to the escape of electrons, and it is the formation of double dipole layer that causes the drop of vacuum energy level of the material surface.
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Keywords:
- GaN /
- electron source /
- transmission coefficient /
- double dipole layer
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[1] Pierce D T, Meier F 1976 Phys. Rev. B 13 5484
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[10] Li Q, Hao L, Pang W N 2008 Acta Phys. Sin. 57 172 (in Chinese)[李 倩、郝 亮、庞文宁 2008 57 172 ]
[11] [12] Ruan C J 2003 Ph. D. Dissertation (Beijing: Tsinghua University) (in Chinese)[阮存军 2003 博士学位论文(北京:清华大学)]
[13] [14] Spicer W E, Herrera-Gmez A 1993 Proc. SPIE 2022 18
[15] [16] Siegmund O, Vallerga J, McPhate J, Malloy J, Tremsin A, Martin A, Ulmer M, Wessels B 2006 Nucl. Instrum. Meth. Phys. Res. A 567 89
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[24] Wang H M, Zhang Y F 2005 Acta Phys. Sin. 54 2226 (in Chinese) [王洪梅、张亚非 2005 54 2226]
[25] [26] Lui W W, Fukuma M 1986 J. Appl. Phys. 60 1555
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[30] Allen S S, Richardson S L 1996 J. Appl. Phys. 79 886
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[34] [35] Qiao J L, Chang B K, Du X Q, Niu J, Zou J J 2010 Acta Phys. Sin. 59 2855 (in Chinese)[乔建良、常本康、杜晓晴、牛 军、邹继军 2010 59 2855]
[36] [37] Qiao J L, Niu J, Yang Z, Zou J J, Chang B K 2009 Opt. Techn. 35 145 (in Chinese)[乔建良、牛 军、杨 智、邹继军、常本康 2009 光学技术 35 145]
[38] [39] Qiao J L, Chang B K, Qian Y S, Du X Q, Wang X H, Guo X Y 2011 Acta Phys. Sin. 60 017903 (in Chinese)[乔建良、常本康、钱芸生、杜晓晴、王晓晖、郭向阳 2011 60 017903]
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