The stress-induced lattice changes in a p(1x2) ordered oxygen layer on W(110) are measured by low-energy electron diffraction. We have observed that small oxygen islands show a mismatch with the underlying lattice. Our results indicate that along [1-10] the average mismatch scales inversely with the island size as 1/L for all oxygen coverages up to 0.5 ML, while along [001] it is significant only for the smallest oxygen islands and scales as a higher power of the inverse island size. The behaviour along [1-10] is described by a one-dimensional finite-size Frenkel-Kontorova model. Using this model, together with calculated force constants, we make a quantitative estimate for the change of surface-stress upon oxygen adsorption. The result is consistent with our ab-initio calculations, which give a relative compressive stress of -4.72 N/m along [1-10] and a minute relative tensile stress of 0.15 N/m along [001]. The scaling along [001] is qualitatively explained as an effect induced by the lattice relaxation in the [1-10] direction.
Interplay of Strain Relaxation and Chemically Induced Diffusion Barriers: Nanostructure Formation in 2D Alloys
我们研究了在亚单层异质外延过程中,由本体不混溶的吸附物组成的交替条纹纳米结构的形成。我们评估了文献中考虑的两种机制的影响:(i)交替排列的吸附物物种的应变弛豫,及(ii)由于化学诱导的扩散障碍的动力学偏析。一个模型三元系统的两个吸附物与相反的失配相对于基板,和对称的结合研究的非晶格以及晶格动力学蒙特卡罗模拟。我们发现,机制(i)或(ii)都不能单独解释已知的实验观察。相反,需要两者的结合。我们提出了一个非晶格模型,它允许定性再现的条纹图案以及岛的衍生物与最近的实验观察CoAg/Ru(0001)[R。Q. Hwang,Phys. Rev. Lett. 76,4757(1996)]。的条纹宽度和岛的分歧程度上的错配和两种吸附质类型之间的相互作用强度的定量依赖关系。试图捕捉一个简化的格子气模型的基本特征表明,一个详细的非本地效应的纳入是必要的。
Kinetic Monte Carlo simulation of shape transition in strained quantum dots
采用一种新的结合有效表面重构的多态晶格模型,对Ge $_{x}$ Si $_{1-x}$ on Si(100)中由金字塔量子点上的阶跃聚束引发的量子点到圆顶的转变进行了原子级模拟.结果解释了一个简单的理论基础上的浅岛近似。在给定的沉积条件下,在$d$尺寸,形状的转变被证明发生在岛的大小$n_c$以下$n_c^{1/d} \propto x^{-ζ}$独立的温度和沉积速率,其中$ζ\alt 2$和$x$是实际的锗在岛的浓度。该过渡具有由小面界面能主导的能垒。然而,快速沉积可能超过并延迟向更大岛尺寸的过渡。
Charge doping induced phase transitions in hydrogenated and fluorinated graphene
我们发现,电荷掺杂可以诱导氢化和氟化石墨烯中三种不同的吸附物相之间的转变。通过结合从头算,近似密度泛函理论和紧束缚计算,我们确定了过渡从岛的C $_8$ H $_2$和C $_8$ F $_2$的随机吸附分布周围的掺杂水平$\pm 0.05$ e/C-原子。此外,在具有随机吸附物覆盖的情况下,电荷掺杂被示出为触发有序转变,其中当掺杂水平超过吸附物浓度时,亚晶格对称性自发地被破坏。再杂化能和晶格畸变能使得仅从一侧共价官能化的石墨烯最容易发生这两种相变。与聚集和有序转变相关的能量增益超过室温热能。
Interplay of Quantum Size Effect and Tensile Strain on Surface Morphology of Sn(100) Islands
Shanghai Jiao Tong University(上海交通大学);The Pennsylvania State University(宾夕法尼亚州立大学);University of Utah(犹他大学);Hefei National Laboratory(合肥国家实验室);Shanghai Research Center for Quantum Sciences(上海量子科学研究中心)
Non-monotonic roughness evolution in film growth on weakly interacting substrates
Eberhard Karls Universität Tübingen(蒂宾根大学);International Center of Physics, Institute of Physics, University of Brasília(巴西利亚大学物理学院国际物理中心);Departamento de Física, Universidade Federal de Viçosa(维索萨联邦大学物理系);European Synchrotron Radiation Facility (ESRF)(欧洲同步辐射装置);Instituto de Física, Universidade Federal Fluminense(弗鲁米嫩塞联邦大学物理研究所)
Bismuth-surfactant-induced growth and structure of InAs/GaAs(110) quantum dots
本文研究了分子束外延生长的InAs量子点在GaAs(110)衬底上的自组装和结构。在InAs沉积过程中添加Bi助熔剂将InAs的生长模式从二维(2D)Frank-van der Merwe改变为Stranski-Krastanov,导致在表面上形成三维(3D)InAs岛。此外,将静态InAs 2D层暴露于Bi诱导应变层重排成3D岛。我们探讨了这两种生长方法的InAs厚度和Bi通量的变化的影响,观察在这两种情况下的3D岛形成的临界厚度。用高分辨率透射电子显微镜对(110)InAs量子点的表征表明,通过Stranski-Krastanov模式生长的较大岛屿是塑性弛豫的,而通过按需方法生长的小岛是相干的。沿[1-10]方向的应变弛豫是通过90度纯刃位错实现的,其中位错线沿[001]延伸。相反,沿[001]的应变消除是通过60度错配位错。这种行为与平面(In,Ga)As/GaAs(110)层的观察结果一致。这些结果说明了表面活性剂Bi如何能够在通常不发生量子点形成的地方引发和控制量子点形成。
Sizes of Ferroelectricity Appearance and Disappearence in Nanosized Hafnia-Zirconia:Landau-type Theory
Institute of Physics of the National Academy of Sciences of Ukraine(乌克兰国家科学院物理研究所);Frantsevich Institute for Problems in Materials Science of the National Academy of Sciences of Ukraine(乌克兰国家科学院弗兰采维奇材料科学问题研究所);Department of Materials Science and Engineering, University of Tennessee(田纳西大学材料科学与工程系);Faculty of Radiophysics, Electronics and Computer Systems, Taras Shevchenko National University of Kyiv(基辅塔拉斯舍甫琴科国立大学无线电物理、电子和计算机系统学院);V. Lashkariov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine(乌克兰国家科学院V.拉什卡廖夫半导体物理研究所)
Spatially resolved elastic strain and lattice rotation at threading dislocations in HgCdTe/CdZnTe epilayers by dark-field X-ray microscopy
European Synchrotron Radiation Facility(欧洲同步辐射装置);Université Grenoble Alpes, CEA, LETI(格勒诺布尔阿尔卑斯大学,CEA,LETI);Karlsruhe Institute of Technology(卡尔斯鲁厄理工学院)