Microscopic origin of lattice contraction and expansion in undoped rutile TiO2 nanostructures
Microscopic origin of lattice contraction and expansion in undoped rutile TiO2 nanostructures
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DOI：
10.1088/0022-3727/47/21/215302
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发表时间：
2014-05-30
影响因子：
3.4
通讯作者：
Fujii, Minoru
中科院分区：
文献类型：
--
作者：
Santara, Batakrushna;Giri, P. K.;Fujii, Minoru
我们研究了晶格膨胀和收缩的微观起源在未掺杂的金红石型TiO 2纳米结构，采用几种结构和光学光谱工具。采用酸水热法合成了金红石型TiO 2纳米结构，根据不同的生长条件，可以得到不同形貌的纳米棒、纳米柱和纳米花。根据生长条件和生长后退火，晶格收缩和膨胀中观察到的纳米结构，它被发现与金红石型TiO 2的本征缺陷的性质和密度。晶格体积的变化与光学带隙能量密切相关。无论生长条件如何，TiO 2纳米结构在1.43 eV处表现出强的近红外（NIR）光致发光（PL）和弱的可见光PL，这分别归因于金红石型TiO 2纳米结构中的Ti空位和O空位。此外，ESR研究揭示了单离子氧空位缺陷的存在。观察到晶格畸变系统地依赖于氧空位和Ti杂质等缺陷的相对浓度和类型。XPS分析表明，在各种生长条件下，Ti 2 p和O 1 s的核心能级光谱的能量下移，这被认为是由于晶格畸变。提出了Ti4+间隙和F+氧空位缺陷是导致晶格膨胀的主要原因，而Ti4+间隙和O2-间隙缺陷之间的静电吸引导致了未掺杂TiO 2纳米结构的晶格收缩。通过本征缺陷控制晶格参数可以提供新的途径，以实现先进材料的新功能，可以为未来的技术应用定制。
We have investigated the microscopic origin of lattice expansion and contraction in undoped rutile TiO2 nanostructures by employing several structural and optical spectroscopic tools. Rutile TiO2 nanostructures with morphologies such as nanorods, nanopillars and nanoflowers, depending upon the growth conditions, are synthesized by an acid-hydrothermal process. Depending on the growth conditions and post-growth annealing, lattice contraction and expansion are observed in the nanostructures and it is found to correlate with the nature and density of intrinsic defects in rutile TiO2. The change in lattice volume correlates well with the optical bandgap energy. Irrespective of growth conditions, the TiO2 nanostructures exhibit strong near infrared (NIR) photoluminescence (PL) at 1.43 eV and a weak visible PL, which are attributed to the Ti interstitials and O vacancies, respectively, in rutile TiO2 nanostructures. Further, ESR study reveals the presence of singly ionized oxygen vacancy defects. It is observed that lattice distortion depends systematically on the relative concentration and type of defects such as oxygen vacancies and Ti interstitials. XPS analyses revealed a downshift in energy for both Ti 2p and O 1s core level spectra for various growth conditions, which is believed to arise from the lattice distortions. It is proposed that the Ti4+ interstitial and F+ oxygen vacancy defects are primarily responsible for lattice expansion, whereas the electrostatic attraction between Ti4+ interstitial and O2- interstitial defects causes the lattice contraction in the undoped TiO2 nanostructures. The control of lattice parameters through the intrinsic defects may provide new routes to achieving novel functionalities in advanced materials that can be tailored for future technological applications.