Materials Engineering, University of California, Santa Barbara, CA 93106, USA.
J Phys Condens Matter. 2014 Apr 16;26(15):155802. doi: 10.1088/0953-8984/26/15/155802. Epub 2014 Mar 27.
The electronic structures of four semiconductor compounds BaCu2S2, BaCu2Se2, BaAg2S2, and BaAg2Se2 are studied by density functional theory using both semi-local and hybrid functionals. The ionization energies and electron affinities were determined by aligning the electronic states with the vacuum level by calculating the electrostatic profile within a supercell slab model. The ionization energy and electron affinity of the compounds were calculated using the Heyd-Scuseria-Ernzerhof functionals and range from 4.5 eV to 5.4 eV and 3.1 eV to 3.4 eV, respectively. The replacement of Cu by Ag slightly increases the ionization energy and electron affinity, while the replacement of S by Se decreases the ionization energy but slightly increases the electron affinity. Overall, the low ionization energies and small electron affinities suggest that these compounds possess good p-type doping propensities. The band gaps are somewhat small to be ideal candidates for transparent semiconducting behavior; however, the replacement of Cu with Ag in the barium sulfide compounds can increase the band gap from 1.62 to 2.01 eV.
采用密度泛函理论，使用半局域和混合泛函研究了四种半导体化合物 BaCu2S2、BaCu2Se2、BaAg2S2 和 BaAg2Se2 的电子结构。通过在超胞薄片模型中计算静电势分布，将电子态与真空能级对齐，从而确定了电离能和电子亲和能。使用 Heyd-Scuseria-Ernzerhof 泛函计算了化合物的电离能和电子亲和能，范围分别为 4.5 eV 至 5.4 eV 和 3.1 eV 至 3.4 eV。Cu 被 Ag 取代会略微增加电离能和电子亲和能，而 S 被 Se 取代会降低电离能，但略微增加电子亲和能。总体而言，这些化合物具有较低的电离能和较小的电子亲和能，表明它们具有良好的 p 型掺杂倾向。这些化合物的带隙有点小，不太适合透明半导体行为；然而，在钡硫化物化合物中用 Ag 取代 Cu 可以将带隙从 1.62 eV 增加到 2.01 eV。
