Ma KeYuan, Lefèvre Robin, Li Qingtian, Lago Jorge, Blacque Olivier, Yang Wanli, von Rohr Fabian O
Department of Chemistry, University of Zurich CH-8057 Zürich Switzerland
Advanced Light Source, Lawrence Berkeley National Laboratory Berkeley California 94720 USA.
Chem Sci. 2021 Oct 5;12(41):13870-13877. doi: 10.1039/d1sc03026d. eCollection 2021 Oct 27.
Pyrite, also known as fool's gold is the thermodynamic stable polymorph of FeS. It is widely considered as a promising d-band semiconductor for various applications due to its intriguing physical properties. Marcasite is the other naturally occurring polymorph of FeS. Measurements on natural crystals have shown that it has similarly promising electronic, mechanical, and optical properties as pyrite. However, it has been only scarcely investigated so far, because the laboratory-based synthesis of phase-pure samples or high quality marcasite single crystal has been a challenge until now. Here, we report the targeted phase formation hydrothermal synthesis of marcasite and pyrite. The formation condition and phase purity of the FeS polymorphs are systematically studied in the form of a comprehensive synthesis map. We, furthermore, report on a detailed analysis of marcasite single crystal growth by a space-separated hydrothermal synthesis. We observe that single phase product of marcasite forms only on the surface under the involvement of HS and sulphur vapor. The availability of high-quality crystals of marcasite allows us to measure the fundamental physical properties, including an allowed direct optical bandgap of 0.76 eV, temperature independent diamagnetism, an electronic transport gap of 0.11 eV, and a room-temperature carrier concentration of 4.14 × 10 cm. X-ray absorption/emission spectroscopy are employed to measure the band gap of the two FeS phases. We find marcasite has a band gap of 0.73 eV, while pyrite has a band gap of 0.87 eV. Our results indicate that marcasite - that is now synthetically available in a straightforward fashion - is as equally promising as pyrite as candidate for various semiconductor applications based on earth abundant elements.
黄铁矿，又称愚人金，是FeS的热力学稳定多晶型物。由于其引人入胜的物理性质，它被广泛认为是一种有前途的用于各种应用的d带半导体。白铁矿是FeS的另一种天然存在的多晶型物。对天然晶体的测量表明，它具有与黄铁矿相似的有前途的电子、机械和光学性质。然而，到目前为止它只得到了很少的研究，因为直到现在基于实验室的相纯样品或高质量白铁矿单晶的合成一直是一个挑战。在这里，我们报道了白铁矿和黄铁矿的靶向相形成水热合成。以综合合成图的形式系统地研究了FeS多晶型物的形成条件和相纯度。此外，我们还报道了通过空间分离水热合成对白铁矿单晶生长的详细分析。我们观察到，在HS和硫蒸气的参与下，白铁矿的单相产物仅在表面形成。高质量白铁矿晶体的可得性使我们能够测量其基本物理性质，包括0.76 eV的允许直接光学带隙、与温度无关的抗磁性、0.11 eV的电子输运带隙以及室温载流子浓度为4.14×10 cm。采用X射线吸收/发射光谱法测量两种FeS相的带隙。我们发现白铁矿的带隙为0.73 eV，而黄铁矿的带隙为0.87 eV。我们的结果表明，现在可以以直接的方式合成得到的白铁矿，作为基于地球上丰富元素的各种半导体应用的候选材料，与黄铁矿同样有前途。
