Modulation Doping in Metastable Heterostructures via Kinetically Controlled Substitution

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• 作者：Suzannah R. WoodDevin R. Merrill ; Gavin Mitchson ; Alexander C. LygoSage R. Bauers ; Danielle M. Hamann ; Duncan R. Sutherland ; Jeffrey Ditto ; David C. Johnson
• 刊名：Chemistry of Materials
• 出版年：2017
• 出版时间：January 24, 2017
• 年：2017
• 卷：29
• 期：2
• 页码：773-779
• 全文大小：571K
• ISSN：1520-5002

文摘

Controlling carrier concentration is critical in many device applications, and both chemical substitution and modulation doping have been used in industry. For most inorganic materials, very low doping efficiencies are observed as site occupancies depend on both thermodynamic and kinetic factors. We demonstrate that we can make kinetically controlled site-specific substitutions in a series of (Bi<sub>xsub>Sn<sub>1–xsub>Se)<sub>1+δsub>TiSe<sub>2sub> compounds using the modulated elemental reactants method. These compounds were characterized using a combination of X-ray diffraction, resistivity and Hall coefficient measurements, and high angle annular dark field scanning transmission electron microscopy (HAADF STEM). For small x, the doping efficiency is 0.7, close to that observed for B in silicon. For higher x values, a structural distortion is observed in X-ray diffraction data in which the symmetry of the in-plane unit cell decreases. HAADF STEM data reveals the presence of antiphase boundaries (Bi–Bi pairs) in the Bi<sub>xsub>Sn<sub>1–xsub>Se layers, which increasingly occur as x increases from 0.48 to 0.71. Electrical measurements show that doping efficiency decreases as x increases, correlated with the structural distortion and the formation of periodic antiphase boundaries containing Bi–Bi pairs.