Flat-surface-assisted and self-regulated oxidation resistance of Cu(111)

The formation of an ultraflat surface on copper thin films is important for suppressing the oxidation process, but the formation of multi-atomic steps and terraces is a result of the basic atomic stacking process and difficult to avoid. Here, we develop an innovative strategy for fabricating copper thin films with a semi-permanently oxidation-resistant surface. Comprehensive atomic-resolution microscopy reveals that our thin film consists mostly of flat surfaces and occasional mono-atomic steps. Our first principles calculations show that a mono-atomic step edge is as impervious as a flat surface to oxygen consistent with our experimental observations. Furthermore, the first principles calculations exhibit self-regulated oxidation resistance at the top surface layer: when the oxygen coverage of fcc sites of the surface exceeds 50%, the adsorbed oxygens on the top layer suppresses further adsorption of additional O atoms and renders the ultraflat Cu surface to be more oxidation resistant.

CHEMICAL MECHANICAL POLISHING AND ITS MECHANISM ON YTTERBIUM-DOPED MIXED SESQUIOXIDES (Yb:LuScO3)

In this paper, Yb:LuScO3 crystal was processed by chemical mechanical polishing (CMP), and the surface roughness of 0.18[Formula: see text]nm was obtained. The atomic step structures of these sesquioxide crystals are successfully characterized by AFM scanning probe technology. Through several CMP experiments, the basic material removal mechanism of a ytterbium-doped LuScO3 crystal during CMP is studied. Based on the findings, a material removal model is established. The results of this study provide ideas for the study of CMP, crystal growth and epitaxy.

Influences of thickness and temperature of low temperature GaAs buffer layer on two-step MOVPE grown GaAs/Ge heterostructures

We investigate influence of GaAs buffer layer (BL) growth parameters such as temperature and thickness on the structural, morphological, crystalline and optical quality of metal organic vapor phase epitaxy (MOVPE) grown heterostructures of GaAs on Ge. It was found that the optimal BL conditions significantly decrease the effects of anti-phase boundaries (APBs) even when grown on offcut Ge substrate by two-step growth technique with AsH3 pre-flow to promote double atomic step formation. It is observed that as the growth temperature increases, the growth rate of the GaAs BL increases, too. Improvement on the structural quality is observed up to BLs temperature of 535 °C, then it decreases. On the other hand, as the different thick BLs, 12, 25, 75 nm are considered, the epilayer grown on the 25 nm thick BL has shown the lowest full width at half maximum (FWHM) value, large photoluminescence peak intensity and internal quantum efficiency (IQE).

Lubricated friction around nanodefects

The lubrication properties of nanoconfined liquids underpin countless natural and industrial processes. However, our current understanding of lubricated friction is still limited, especially for nonideal interfaces exhibiting nanoscale chemical and topographical defects. Here, we use atomic force microscopy to explore the equilibrium and dynamical behavior of a model lubricant, squalane, confined between a diamond tip and graphite in the vicinity of an atomic step. We combine high-resolution imaging of the interface with highly localized shear measurements at different velocities and temperatures to derive a quantitative picture of the lubricated friction around surface defects. We show that defects tend to promote local molecular order and increase friction forces by reducing the number of stable molecular configurations in their immediate vicinity. The effect is general, can propagate over hundreds of nanometers, and can be quantitatively described by a semiempirical model that bridges the molecular details and mesoscale observations.