Tuning optical absorption in perovskite (K,Na)NbO3 ferroelectrics†

IF 5.2 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY
V. Vetokhina, N. Nepomniashchaia, E. de Prado, O. Pacherova, T. Kocourek, S. S. Anandakrishnan, Y. Bai, A. Dejneka and M. Tyunina
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Abstract

The ability to tailor the electronic band structure and optical absorption by appropriate cationic substitution in perovskite oxide ferroelectrics is essential for many advanced electronic and optoelectronic applications of these materials. Here, we explored weak (Ba,Ni)-doping for reducing optical bandgaps in (K,Na)NbO3 ferroelectric films and ceramics. The optical absorption in the broad spectral range of (0.7–8.8) eV was investigated in polycrystalline doped, pure, and oxygen deficient films, in doped epitaxial films grown on different substrates, and in doped ceramics. By comparing optical properties of all films and ceramics, it was established that 1–2 at% of cationic substitutions or up to 10 at % of oxygen vacancies have no detectable effect on the direct (∼4.5 eV) and indirect (∼3.9 eV) gaps. Concurrently, substantial sub-gap absorption was revealed and ascribed to structural band tailing in epitaxial films and ceramics. It was suggested that owing to fundamental strain-property couplings in perovskite oxide ferroelectrics, inhomogeneities of lattice strain can lead to increased sub-gap absorption. The uncovered structurally induced sub-gap optical absorption can be relevant for other ferroelectric ceramics and thin films as well as for related perovskite oxides.

Abstract Image

调谐包晶(K,Na)NbO3 铁电体的光吸收。
在包晶氧化物铁电材料中通过适当的阳离子取代来定制电子能带结构和光吸收的能力,对于这些材料的许多先进电子和光电应用至关重要。在此,我们探索了掺入弱(Ba,Ni)元素以降低(K,Na)NbO3 铁电薄膜和陶瓷的光带隙。我们研究了多晶掺杂薄膜、纯薄膜和缺氧薄膜、生长在不同基底上的掺杂外延薄膜以及掺杂陶瓷在 (0.7-8.8) eV 宽光谱范围内的光吸收。通过比较所有薄膜和陶瓷的光学特性,可以确定 1-2 at% 的阳离子取代或高达 10 at% 的氧空位对直接间隙(∼4.5 eV)和间接间隙(∼3.9 eV)没有可检测到的影响。与此同时,还发现了大量的隙下吸收,并将其归因于外延薄膜和陶瓷中的结构带尾。研究表明,由于包晶氧化物铁电体中基本的应变-性能耦合,晶格应变的不均匀性会导致亚间隙吸收的增加。所揭示的结构诱导的亚间隙光学吸收可能与其他铁电陶瓷和薄膜以及相关的包晶氧化物有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Materials Advances
Materials Advances MATERIALS SCIENCE, MULTIDISCIPLINARY-
CiteScore
7.60
自引率
2.00%
发文量
665
审稿时长
5 weeks
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