Chemical Vapor Deposition (CVD) of graphene on copper is one of the most efficient technologies for producing high quality graphene for large areas. Nevertheless, still high pressures and big quantities of precursor gas are currently required. The objective of this work is to deposit graphene using the monolayer-formation-time concept (t) from the kinetic theory of gases, which leads to an economization of the precursor gas, a minimization of the process pressure and the time needed to grow a graphene monolayer. Our process has been designed taking into account the dependence of t on the pressure, the mass particle of the gas, the sticking coefficient, and the growth temperature. Thus, with this alternative method, based on CVD but using very-low pressure instant pulses of precursor gas (~10^-4 Pa), we have reduced the deposition time to the order of 10 s. We carried out the processes at temperatures below 1000 Grad Celsius with methane (CH4) as a precursor gas under High Vacuum (HV) conditions. After Raman spectroscopy and mapping, and Scanning Electron Microscopy (SEM) characterization of the samples, the results point to the formation of high quality monolayer graphene on sputtered copper and silicon substrates covering domain areas of 10^4 micron^2.
Structural, magnetic, and optical properties of zinc- and copper- substituted nickel ferrite nanocrystals
铁氧体纳米晶由于其丰富的物理性质而成为人们感兴趣的材料。在这里，我们将掺杂剂Zn和Cu添加到镍铁氧体纳米晶体Ni 1-xMxFe 2 O 4（0<=x<=1，M{ \in }{Cu，Zn}）中，并表征样品的相关性质如何相应地改变。基本上，这些掺杂导致Fe+3离子重排到两个预先存在的八面体和四面体位置。事实上，这，我们表明，诱导相关的磁性掺杂样品。在Cu掺杂的情况下，Jahn-Teller效应也出现了，我们通过样品的FTIR光谱来识别。此外，我们发现掺杂样品的晶格参数增加，以及掺杂样品的超顺磁性行为，而Jahn-Teller效应排除了CuFe 2 O 4纳米晶体中类似的行为。采用室温光致发光法研究了Zn和Cu掺杂对镍铁氧体纳米晶光学性质的影响。
Incorporation of surface correction and anharmonic correction to vacancy formation energy for nickel and copper: bridging the gap between Density Functional Theory and experiment
Nowadays, there is pressing demand for sustainable energy sources, or clean and 'green' fuel and hydrogen is a perfect candidate. It can be made by dissociating methane with the energy input compensated by metal-hydrogen bond formation. Industry uses Nickel supported on $γ$-alumina for this rate-limiting step. This work shows how to use Quantum Monte Carlo calculations to take (user-guided) information summarising chemistry of heterogeneous catalysis from a generic Jastrow factor, that allows electron correlation to be included in the density. This, in turn, gives accurate values of properties…
Large-Area Synthesis of High-Quality and Uniform Graphene Films on Copper Foils
石墨烯因其独特的能带结构和物理性质而引起人们极大的兴趣。如今，石墨烯仅限于小尺寸，因为它主要通过剥离石墨来生产。我们使用甲烷通过化学气相沉积在铜衬底上生长了厘米级的大面积石墨烯薄膜。该膜主要是单层石墨烯，其中小百分比（小于5%）的面积具有很少的层，并且在铜表面台阶和晶界上是连续的。碳在铜中的低溶解度似乎有助于使这种生长过程自我限制。我们还开发了石墨烯膜转移到任意衬底的工艺，并且在Si/SiO2衬底上制造的双栅场效应晶体管在室温下显示出高达4050 cm 2 V-1 s-1的电子迁移率。
Many applications of molecular layers deposited on metal surfaces, ranging from single-atom catalysis to on-surface magnetochemistry and biosensing, rely on the use of thermal cycles to regenerate the pristine properties of the system. Thus, understanding the microscopic origin behind the thermal stability of organic/metal interfaces is fundamental for engineering reliable organic-based devices. Here, we study nickel porphyrin molecules on a copper surface as an archetypal system containing a metal center whose oxidation state can be controlled through the interaction with the metal substrate.…
Transition metal impurities such as nickel, copper, and iron, in solid-state materials like silicon have a significant impact on the electrical performance of integrated circuits and solar cells. To study the impact of copper impurities inside bulk silicon on the electrical properties of the material, one needs to understand the configurational space of copper atoms incorporated inside the silicon lattice. In this work, we performed ReaxFF reactive force field based molecular dynamics simulations, studying different configurations of individual and crystalline copper atoms inside bulk silicon …
In the present paper, the analysis of polishing, grinding and sand-blasting processes on oxidation behavior of nickel, copper and nickel-copper alloy has been investigated. Surface roughness has been measured using two methods: by contact profilometer and by fractal analysis. It has been proved that sand-blasting process influences the surface roughness the most but also contaminates the surface with alumina particles. The oxidation tests were performed in thermogravimetrical furnace. The obtained mass gain plots, SEM microphotographs of cross-sections and SEM EDS analysis of the samples prove…
通过化学气相沉积的石墨烯生长最近由于可以容易地生长大面积膜而受到了很多关注，但是还没有报道大畴或相当大的晶粒尺寸的生长。在这篇短文中，我们报告了一种CVD工艺，该工艺通过非常低的压力CVD（小于50 mTorr）和非常低的前体流速，在高温（约1000 oC）下，使用甲烷作为铜箔外壳内部的碳源，生产出具有数百微米域的石墨烯。大畴石墨烯膜的载流子迁移率高达21，000 cm 2/Vs。
Moiré in $Γ$-valley square lattice: Copper- and iron-based superconductor simulation in a single device
International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science（物质纳米结构国际中心（WPI-MANA），国立材料研究所）；Department of Physics, Harvard University（哈佛大学物理系）；Department of Physics, University of Connecticut（康涅狄格大学物理系）；School of Physics, Georgia Institute of Technology（佐治亚理工学院物理学院）
Only several compounds bearing Ag(II) cation and other transition metal cation have been known. Herein, we predict stability and crystal structures of hypothetical ternary silver(II) fluorides with copper, nickel and cobalt in 1:1 stoichiometry at pressure range from 0 GPa up to 20 GPa within the frame of Density Functional Theory. Calculations show that AgCoF4 could be synthesized already at ambient conditions but this compound would host diamagnetic Ag(I) and high-spin Co(III). However, at increased pressure ternary fluorides of Ag(II) featuring Cu and Ni could be synthesized, in the pressur…
