General Top-Down Ion Exchange Process for the Growth of Epitaxial Chalcogenide Thin Films and Devices

详细信息    查看全文

• 作者：Chuan XiaPeng Li ; Jun Li ; Qiu Jiang ; Xixiang Zhang ; Husam N. Alshareef
• 刊名：Chemistry of Materials
• 出版年：2017
• 出版时间：January 24, 2017
• 年：2017
• 卷：29
• 期：2
• 页码：690-698
• 全文大小：718K
• ISSN：1520-5002

文摘

We demonstrate a versatile top-down ion exchange process, done at ambient temperature, to form epitaxial chalcogenide films and devices, with nanometer scale thickness control. To demonstrate the versatility of our process we have synthesized (1) epitaxial chalcogenide metallic and semiconducting films and (2) free-standing chalcogenide films and (3) completed in situ formation of atomically sharp heterojunctions by selective ion exchange. Epitaxial NiCo₂S₄ thin films prepared by our process show 115 times higher mobility than NiCo₂S₄ pellets (23 vs 0.2 cm² V^–1 s^–1) prepared by previous reports. By controlling the ion exchange process time, we made free-standing epitaxial films of NiCo₂S₄ and transferred them onto different substrates. We also demonstrate in situ formation of atomically sharp, lateral Schottky diodes based on NiCo₂O₄/NiCo₂S₄ heterojunction, using a single ion exchange step. Additionally, we show that our approach can be easily extended to other chalcogenide semiconductors. Specifically, we used our process to prepare Cu_1.8S thin films with mobility that matches single crystal Cu_1.8S (25 cm² V^–1 s^–1), which is ca. 28 times higher than the previously reported Cu_1.8S thin film mobility (0.58 cm² V^–1 s^–1), thus demonstrating the universal nature of our process. This is the first report in which chalcogenide thin films retain the epitaxial nature of the precursor oxide films, an approach that will be useful in many applications.