Research on Cs activation mechanism for Ga0.5Al0.5As(0 0 1) and GaN(0 0 0 1) surface
Research on Cs activation mechanism for Ga0.5Al0.5As(0 0 1) and GaN(0 0 0 1) surface
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DOI：
10.1016/j.apsusc.2014.10.088
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发表时间：
2015
影响因子：
6.7
通讯作者：
Yang Shen;Liang Chen;Y. Qian;D. Yanyan;Shuqin Zhang;Meishan Wang
中科院分区：
文献类型：
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作者：
Yang Shen;Liang Chen;Y. Qian;D. Yanyan;Shuqin Zhang;Meishan Wang
基于第一性原理密度泛函理论（DFT），采用平面波超软赝势方法，计算并比较了Ga 0.5Al 0.5As（0 0 1）和GaN（0 0 0 1）表面的Cs激活机制.在本工作中，选择了八个可能的Cs吸附位的Ga 0.5Al 0.5As（001）表面，而在GaN（0001）表面的计算模型中考虑了五个高对称性的网站。结果表明，Cs的吸附降低了表面功函数，有利于获得最稳定的吸附位。然后研究了不同Cs覆盖率下两个表面的偶极矩。随着Cs覆盖度的增加，GaN（0 0 0 1）表面的偶极矩减小，且变化比Ga 0.5Al 0.5As（0 0 1）表面更明显。Cs原子偶极-偶极间的排斥作用增强，使Cs原子去极化，使Cs原子的功函数再次上升。最后，通过激活实验验证了计算结果，GaN光电阴极比Ga_（0.5）Al_（0.5）As光电阴极更早达到最小功函数。
Based on first-principle density functional theory (DFT), plane wave with ultrasoft pseudopotential method was used to calculate and compare the Cs activation mechanism for Ga0.5Al0.5As(0 0 1) surface and GaN(0 0 0 1) surface. In this work, eight possible Cs adsorption sites are chosen for the Ga0.5Al0.5As(0 0 1) surface while five high-symmetry sites are considered in the calculation model of GaN(0 0 0 1) surface. Results show that Cs adsorption lowers the surface work function and benefits to get the most stable adsorption sites. Then dipole moment with different Cs coverage on two surfaces is investigated. The dipole moment decreases with the increase of Cs coverage and GaN(0 0 0 1) surface changes more obviously than Ga0.5Al0.5As(0 0 1) surface. The repulsion between Cs atomic dipole–dipole is enhanced and it causes depolarization and work function rising again. Finally, an activation experiment is performed to verify the result of our calculations, GaN photocathodes gets the minimum work function earlier than Ga0.5Al0.5As photocathodes.