Stabilization and heteroepitaxial growth of metastable tetragonal FeS thin films by pulsed laser deposition
Stabilization and heteroepitaxial growth of metastable tetragonal FeS thin films by pulsed laser deposition
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DOI：
10.1088/1361-6668/ab097e
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发表时间：
2019-05-01
影响因子：
3.6
通讯作者：
Hosono, Hideo
中科院分区：
文献类型：
--
作者：
Hanzawa, Kota;Sasase, Masato;Hosono, Hideo
脉冲激光沉积是一种非平衡薄膜生长技术，用于稳定亚稳态四方硫化铁（FeS），其体态被称为临界温度为4 K的超导体。综合实验揭示了稳定四方FeS外延薄膜的四个重要因素。 (i) 300 摄氏度的最佳生长温度，然后进行热淬火，(ii) 类似于 7 nm min(-1) 的最佳生长速率，(iii) 使用高纯度块状靶材，以及 (iv) 使用具有小面内晶格失配 (CaF2) 的单晶衬底。电阻率测量表明没有一个薄膜表现出超导性。尽管利用四方FeS外延膜作为沟道层制备了双电层晶体管结构，实现了高密度载流子掺杂，但没有观察到相变。缺乏超导性的可能原因包括晶格应变、薄膜的非化学计量、栅极偏压下离子液体的电化学蚀刻以及器件制造过程中的表面退化。
Pulsed laser deposition, a non-equilibrium thin-film growth technique, was used to stabilize metastable tetragonal iron sulfide (FeS), the bulk state of which is known as a superconductor with a critical temperature of 4 K. Comprehensive experiments revealed four important factors to stabilize tetragonal FeS epitaxial thin films . (i) an optimum growth temperature of 300 degrees C followed by thermal quenching, (ii) an optimum growth rate of similar to 7 nm min(-1), (iii) use of a high-purity bulk target, and (iv) use of a single-crystal substrate with small in-plane lattice mismatch (CaF2). Electrical resistivity measurements indicated that none of the films exhibited superconductivity. Although an electric double-layer transistor structure was fabricated using the tetragonal FeS epitaxial film as a channel layer to achieve high-density carrier doping, no phase transition was observed. Possible reasons for the lack of superconductivity include lattice strain, off-stoichiometry of the film, electrochemical etching by the ionic liquid under gate bias, and surface degradation during device fabrication.