npj: 硫族金属元素化物超级原子体—二维半导体的调控

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载流子的性质和密度以及费米能量的位置决定了半导体的电子、光电子和其他功能粒子。因此，精确调控半导体特性的关键，就在于设计好这些参数的调节策略。然而这种调节策略却难以设计。

来自弗吉尼亚联邦大学的Shiv Khanna教授等，对所选的超原子团簇Co₆Se₈(PEt₃)₆在二维半导体WSe₂表面之间的电荷转移机制，进行了理论研究。他们通过在广义梯度逼近算法中加入色散校正密度泛函理论（DFT）和涉及范德华相互作用的DFT-D2函数计算，发现Co₆Se₈(PEt₃)₆超原子体能够向WSe₂提供多个电子，从而改变其电学性能从p-型半导体转变为n-型半导体，从理论上证实了新近实验的观测结果，即支持Co₆Se₈(PEt₃)₆的WSe₂薄膜从p-型到n-型的性能变化的机制，证明了Co₆Se₈(PEt₃)₆超原子体可以作为原子级薄膜半导体的可调化学掺杂物。他们进一步发现，用CO配体取代PEt₃配体，可以在宽泛范围内调控表面和沉积物质的电子特性。上述结果将有益于设计二维材料的有效掺杂策略。

该文近期发表于npj Computational Materials 4: 33 (2018)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Co₆Se₈(PEt₃)₆ superatoms as tunable chemical dopants for two-dimensional semiconductors（Co₆Se₈(PEt₃)₆

Arthur C. Reber & Shiv N. Khanna 

Electronic, optoelectronic, and other functionalities of semiconductors are controlled by the nature and density of carriers, and the location of the Fermi energy. Developing strategies to tune these parameters holds the key to precise control over semiconductors properties. We propose that ligand exchange on superatoms can offer a systematic strategy to vary these properties. We demonstrate this by considering a WSe2 surface doped with ligated metal chalcogenide Co6Se8(PEt3)6 clusters. These superatoms are characterized by valence quantum states that can readily donate multiple electrons. We find that the WSe2 support binds more strongly to the Co6Se8 cluster than the PEt3 ligand, so ligand exchange between the phosphine ligand and the WSe2 support is energetically favorable. The metal chalcogenide superatoms serves as a donor that may transform the WSe2 p-type film into an n-type semiconductor. The theoretical findings complement recent experiments where WSe2 films with supported Co6Se8(PEt3)6 are indeed found to undergo a change in behavior from p- to n-type. We further show that by replacing the PEt3 ligands by CO ligands, one can control the electronic character of the surface and deposited species.

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