Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
Proc Natl Acad Sci U S A. 2010 Aug 24;107(34):14968-72. doi: 10.1073/pnas.1009310107. Epub 2010 Aug 2.
Line defects on the surface of rutile TiO(2)(110) form in pairs separated by 1.2 nm creating a quantum well. The well is effectively closed by the presence of two charged structures at both ends separated by a distance in the 10-20 nm range. As expected for quantum confinement a long period oscillatory feature of the local density of states is observed and attributed to the formation of discrete quantum states inside the system. It is at first glance surprising that the lowest energy quantum state of the well can be observed at room temperature. The properties of the quantum state cannot be explained in an independent-electron, band-like theory. Instead, electron-electron correlation must be included to give a satisfactory picture of the spatial distribution of the charge density. Theory predicts charging energies of 1.30 eV and 1.14 eV for quantum well lengths of 14 nm and 16 nm, respectively, in good agreement with a classical calculation and the size dependence of the capacitance. This observation opens up the possibility of experimentally imaging the transition from a Coulomb blockade localized in a zero-dimensional system to an independent-particle or band-like behavior in an extended one-dimensional system.
金红石 TiO(2)(110)表面的线缺陷成对出现，间距为 1.2nm，形成量子阱。由于两端存在两个带电荷的结构，它们之间的距离在 10-20nm 范围内，因此该量子阱实际上是封闭的。正如量子限制所预期的那样，观察到局域态密度的长周期振荡特征，并将其归因于系统内离散量子态的形成。令人惊讶的是，该量子阱的最低能量量子态可以在室温下观察到。量子态的性质不能用独立电子、能带理论来解释。相反，必须包括电子-电子相关，才能给出电荷密度空间分布的满意图像。理论预测，量子阱长度分别为 14nm 和 16nm 时，充电能分别为 1.30eV 和 1.14eV，与经典计算和电容的尺寸依赖性吻合较好。这一观察结果为实验成像从零维系统中的库仑阻塞到扩展一维系统中的独立粒子或能带行为的转变提供了可能性。
