The formation of ultrathin oxide layers on metal surfaces is a non-thermally-activated process which takes place spontaneously at very low temperatures within nanoseconds. This paper reports mechanistic details of the initial oxidation of bare metal surfaces, in particular Al(111) and TiN(001), as obtained by means of first-principles molecular dynamics modelling within the Density-Functional Theory. It is shown that the reactions of bare metal surfaces with O2 molecules take place according to a 'hot-atom' dissociative mechanism which is triggered by the filling of the sigma-star antibonding molecular orbital and is characterised by a sudden release of a large amount of kinetic energy. This released energy provides a driving force for metal/oxygen place-exchange processes which are responsible for the onset of oxide formation at virtually 0 K and at oxygen coverages well below 1 monolayer (ML). Further simulations of the oxidation reactions reveal that a disordered ultrathin oxide forms on Al(111), whereas a rather ordered structure develops on TiN(001) following a selective oxidation process which leaves clusters of Ti vacancies in the TiN lattice underneath the oxide layer.
Proton polarons in HxWO3 by synchrotron photoemission and DFT modelling
用X射线光电子能谱学测量氢引起的过渡金属氧化物电子结构的变化是一项具有挑战性的工作,因为光电子的起源不能明确地归属于氢。氢引起的三氧化钨电子结构的变化已经知道了100多年,但仍然是有争议的争论。争论的根源在于难以将氢化的影响与缺氧的影响分开。使用膜的方法X-射线光电子能谱学,结合可调同步辐射,我们同时测量核心水平和价带高达1000毫巴的氢压力。在氢化时,W $^{5+}$芯能级和接近费米能级的状态的强度遵循体相H $_x$ WO $_3$的压力-组成等温线而增加。结合实验数据和密度泛函理论,证实了质子极化子模型对氢致色的描述。虽然氢是费米边缘附近的电子结构变化的起源,但价带边缘现在由钨轨道而不是氧主导,这与原始氧化物的情况一样,原始氧化物具有作为(光电化学)催化剂的更广泛的应用。
Machine-learned potential for amorphous Indium-Tin-Oxide alloys
Center for Alloy Innovation and Design (CAID), State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University(西安交通大学合金创新与设计中心、材料力学行为国家重点实验室)
First Principles Determination of the Potential-of-Zero-Charge in an Alumina-coated Aluminum/Water Interface Model for Corrosion Applications
大多数浸在水电解质中的金属表面都有几纳米厚的氧化物/氢氧化物表面层。这就导致了两种金属的存在|氧化物和氧化物|液体电解质界面,并且使得将原子长度尺度结构与电化学性质(诸如零电荷电位(PZC))相关联具有挑战性。PZC值已被证明与腐蚀的点蚀起始电位相关。本文采用大尺度密度泛函理论和从头算分子动力学方法计算了Al(111)的PZC| γ-Al(2)O(3)(110)|水双界面模型中的铝腐蚀。通过将涉及的多个界面划分为对总体功函数和电压具有附加贡献的二元组分,我们预测该模型的PZC为-1.53 V vs. SHE。我们还计算了氧化物中氧空位等缺陷的轨道能级,这些缺陷是与点蚀相关的理论中的关键参数。我们预测,费米能级在PZC位于以上的氧空位,因此不带电的PZC的杂质缺陷水平。从PZC的估计,我们预测的电压需要创造净正电荷内的平带近似的氧空位。
Metal-oxide interface reactions and their effect on integrated resistive/threshold switching in NbOx
反应性金属电极(Nb,Ti,Cr,Ta和Hf)被证明在控制金属/Nb 2 O 5/Pt器件的挥发性开关特性中起着重要的作用。特别是,器件显示出稳定的阈值切换下的负偏压,但有一个响应下的正偏压,这取决于金属的选择。具有Nb和Ti顶部电极的器件显示出对于正极性和负极性都具有对称特性的稳定阈值开关;具有Cr顶部电极的器件显示出稳定阈值开关,但是在正极性和负极性下具有不对称的滞后窗口;具有Ta和Hf电极的器件显示出集成阈值存储器(1 S 1 M)响应。基于热力学数据和集总元件建模,这些影响归因于金属氧化物夹层的形成及其对场致氧交换的响应。这些结果提供了重要的洞察到的开关响应的物理起源和工程设备的可靠的开关特性的途径。
Three Dimensionial Surface Modelling: A Novel Analysis Technique for Non-Destructive X-Ray Diffraction Imaging of Semiconductor Die Warpage & Strain in Fully Encapsulated Integrated Circuits
Fingerprints of spin-orbital entanglement in transition metal oxides
介绍了过渡金属氧化物中超交换键的自旋轨道纠缠的概念,并举例说明。结果表明,自旋-轨道纠缠在超交换模型不稳定的长程(自旋和轨道)秩序,并可能导致一个无序的自旋液体状态或新的阶段,在低温下所产生的强烈受挫的相互作用。这种新颖的基态不能在常规使用的平均场论中描述,该平均场论将自旋和轨道自由度分开。即使在基态解纠缠的情况下,自旋-轨道纠缠也发生在激发态中,并且可能对有限温度下物理性质的正确描述至关重要。作为这种行为的一个重要例子,我们提出了$R$ VO $_3$钙钛矿中的自旋轨道纠缠,其中$R$ =La,Pr,.,Yb,Lu,其中这些化合物的这种有限温度特性只能使用纠缠态来理解:($i$)光谱权重的热演化,($ii$)在$R$ VO $_3$钙钛矿的相图中,轨道和磁序开始的转变温度对离子半径的依赖性,和($iii$)二聚化在磁振子谱中观察到的$C$型反铁磁相的YVO $_3$。最后,它表明,联合自旋-轨道激发在一个有序的相位与共存的反铁磁和交替的轨道顺序引入拓扑约束的空穴传播,从而从根本上改变输运性质的掺杂莫特绝缘体中的空穴运动意味着同时自旋和轨道激发。
Electrically induced ferromagnetism in an irradiated complex oxide
University of California, San Diego(加州大学圣迭戈分校);University of Denver(丹佛大学);University of California, Davis(加州大学戴维斯分校);Lawrence Berkeley National Laboratory(劳伦斯伯克利国家实验室)
The alloying of first-principles calculations with quasiparticle methodologies for the converged solution of the quantum many-electron states in the correlated compound Iron monoxide