Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, USA.
Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106, USA.
Nat Nanotechnol. 2016 May;11(5):465-71. doi: 10.1038/nnano.2015.323. Epub 2016 Feb 1.
Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid-base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti(4+) to form planar p-type [Ti(4+)n(InSe)] coordination complexes. Using this strategy, we fabricate planar p-n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B(3+), Al(3+) and Sn(4+)) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid-base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device.
精确控制二维（2D）材料的电子表面态可以提高其多功能性，并拓宽其在电子学和传感领域的应用。为此，已经使用化学表面功能化来调整 2D 材料的电子性质。然而，到目前为止，化学功能化依赖于晶格缺陷和物理吸附方法，这些方法不可避免地会改变原子层的拓扑特征。在这里，我们利用大多数 2D 金属硫属化物中存在的孤对电子，报告了一种通过路易斯酸碱反应进行功能化的方法，该方法不会改变主体结构。n 型 InSe 的原子层与 Ti(4+)反应形成平面 p 型[Ti(4+)n(InSe)]配位配合物。使用这种策略，我们在 2D InSe 上制造了具有改进整流和光伏性能的平面 p-n 结，而无需异质结构生长程序或器件制造工艺。我们还表明，这种功能化方法适用于其他路易斯酸（如 B(3+)、Al(3+)和 Sn(4+)），并且可以应用于其他 2D 材料（例如 MoS2、MoSe2）。最后，我们表明，使用路易斯酸碱化学作为桥梁将分子连接到 2D 原子层上，并制造出一个原理验证的染料敏化光感应器件是可能的。
