Thermal Phase Control of Two-Dimensional Pt-Chalcogenide (Se and Te) Ultrathin Epitaxial Films and Nanocrystals
Thermal Phase Control of Two-Dimensional Pt-Chalcogenide (Se and Te) Ultrathin Epitaxial Films and Nanocrystals
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DOI：
10.1021/acs.chemmater.1c02163
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发表时间：
2021-10-14
影响因子：
8.6
通讯作者：
Batzill, Matthias
中科院分区：
文献类型：
--
作者：
Li, Jingfeng;Kolekar, Sadhu;Batzill, Matthias
层状化合物组成的控制合成和改性是其在电子或化学应用中部署的必要先决条件。铂硫属化合物表现出各种组成相。在这里，我们研究如何铂-硒化物和铂-碲化物相可以获得作为纳米薄膜或支持的纳米晶体通过物理气相沉积和热处理。薄膜的特征在于扫描隧道显微镜和光谱，扫描透射电子显微镜，和光电发射和拉曼光谱。在所有情况下，Pt-二硫属化物通过Pt和硫属元素共沉积在低于300摄氏度的生长温度下获得。这些薄膜可以生长的货车范德华外延在一个层一层的方式，使这些化合物的显着的层依赖的电子特性的表征。在高温（高于400摄氏度）下的铂碲化物生长导致铂单碲化物的形成。有趣的是，薄膜Pt-二硫族化物也可以转化为不同的相具有较低的硫族元素浓度通过生长后的真空退火。退火引起的硫属元素损失导致新的复合材料。利用这种热处理方法，合成了由交替的PtTe 2和PtTe货车德瓦尔斯层组成的Pt 3 Te 4的间歇层状化合物。通过对PtSe 2的热处理，我们获得了纳米晶形式的非层状Pt-单硒化物。PtSe在体相Pt-Se相图中没有报道，但其结构类似于已知的具有四元晶胞的Pt单硫化物。该Pt-Se相是半导体的，具有类似于0.9eV的带隙。然而，纳米晶PtSe相是不稳定的，并且容易损失更多的Se并最终转化为Pt。因此，它表明，生长后的热诱导转化的Pt-二硫族化物薄膜，使新的Pt-硫族化物相的合成作为纳米薄膜或纳米晶体。
The controlled synthesis and modification of the composition of layered compounds are essential prerequisites for their deployment in electronic or chemical applications. Pt-chalcogenides exhibit various compositional phases. Here, we investigate how Pt-selenide and Pt-telluride phases can be obtained as ultrathin films or as supported nanocrystals by physical vapor deposition and thermal treatment. The films are characterized by scanning tunneling microscopy and spectroscopy, scanning transmission electron microscopy, and photoemission and Raman spectroscopy. In all cases, Pt-dichalcogenides are obtained by Pt and chalcogen codeposition at growth temperatures below 300 degrees C. These films can be grown by van der Waals epitaxy in a layer-by-layer fashion, enabling the characterization of the pronounced layer-dependent electronic properties of these compounds. Pt-telluride growth at elevated temperatures (above 400 degrees C) results in the formation of Pt-monotelluride. Interestingly, the thin film Pt-dichalcogenides can also be transformed into different phases with lower chalcogen concentration by post-growth vacuum annealing. Annealing-induced loss of chalcogen results in new composites. With this thermal process, an intermittent layered compound of Pt3Te4 is synthesized, which consists of alternating PtTe2 and PtTe van der Waals layers. By thermal treatment of PtSe2, we obtain a non-layered Pt-monoselenide in nanocrystalline form. PtSe is not reported in the bulk Pt-Se phase diagram, but its structure is analogue to the known Ptmonosulfide with a tetragonal unit cell. This Pt-Se phase is semiconducting with a band gap of similar to 0.9 eV. The nanocrystalline PtSe phase is, however, unstable and easily loses more Se and eventually converts into Pt. Thus, it is demonstrated that post-growth thermally induced transformation of Pt-dichalcogenides films enables the synthesis of new Pt-chalcogenide phases as ultrathin films or nanocrystals.