Growth Behavior Of Cu Research Articles

Design and catalytic performance of Cu/γ-Al2O3 for electrocatalytic methanol oxidation reaction by using density functional theory and molecular dynamics

The electrocatalytic activity of methanol oxidation reaction (MOR) on Cu/γ-Al2O3 and the growth behavior of Cu on γ-Al2O3 are investigated by using density functional theory and molecular dynamics. It is found that the interaction between the Cu3 cluster and γ-Al2O3(110) is stronger than that between the Cu4 cluster and γ-Al2O3(110). Consequently, the d-band center of the Cu3 cluster locates close to the Fermi level compared to the d-band center of the Cu4 cluster, resulting in high electrocatalytic MOR activity on Cu3/γ-Al2O3(110). The electrocatalytic MOR pathway is non-CO pathway on Cu3/γ-Al2O3(110). The highest Gibbs free energy pathway is CH3O* → CH2O*, which the Gibbs free energy is 0.53 eV. To achieve a high proportion of 2D Cu cluster on γ-Al2O3, it is recommended to prepare the catalyst at temperatures below 500 K with Cu loading below 21.78 wt%. These findings provide valuable insights into the design of MOR catalysts.

Solid-state interfacial reaction of Sn-Ag solders with polycrystalline Cu and (0 0 1) Cu substrate

• For sn-Ag solder, the growth of Cu 3 Sn on (0 0 1)Cu is faster than on polycrystalline Cu in aging. • Ag increases the difference in Cu 3 Sn thickness on (0 0 1)Cu and polycrystalline Cu in aging. • Ag is beneficial to maintain the preferred orientation of Cu 6 Sn 5 in aging. The growth of Cu 3 Sn is associated with the formation of Kirkendall voids and is important to the reliability of solder joints. In this paper, the effect of Ag on the growth behavior of Cu 3 Sn on (0 0 1) Cu and polycrystalline Cu during aging was compared. Besides, the orientation evolution of Cu 6 Sn 5 on (0 0 1) Cu during aging was also investigated. Results suggested the growth rate of Cu 3 Sn on (0 0 1) Cu is higher than that of polycrystalline Cu during solid-state aging and the difference in the Cu 3 Sn layer thickness increases with the increases of Ag content in the solder. Moreover, the addition of Ag is beneficial to maintaining the preferred orientation of Cu 6 Sn 5 on (0 0 1) Cu during solid-state aging. The results have great help to deepen the understanding of the difference in growth behavior of intermetallic compounds on (0 0 1) Cu and polycrystalline Cu during aging.

Properties and microstructure evolution of Sn–Cu–Ni/Cu joints bearing carbon nanotubes and graphene nanosheets for solar cell

In this paper, 0.5 wt% carbon nanotubes (CNTs) and 0.05 wt% graphene nanosheets (GNSs) were selected as additives to modify the properties of Sn–Cu–Ni solder joints for solar cell. The mechanical properties of Sn–Cu–Ni solder joints can be improved by 20–25%. The interface growth behavior of Cu–Sn intermetallic compounds at Sn–Cu–Ni/Cu and Sn–Cu–Ni–0.5CNTs–0.05GNSs/Cu couples after 250 °C and 260 °C soldering with 10 min and 20 min. The experimental results indicate that the growth rate of Cu6Sn5 IMC of Sn–Cu–Ni/Cu solder joints is higher than that of Sn–Cu–Ni–0.5CNTs–0.05GNSs/Cu solder joints. That is, adding 0.5 wt% CNTs and 0.05 wt% GNSs can reduce the growth rate of the Cu6Sn5 IMC layer, which can be attributed to the reduction of the element diffusion coefficient. In addition, the stress–strain of the two solder joints were calculated using finite element method, it is found that the Sn–Cu–Ni–0.5CNTs–0.05GNSs/Cu solder joints have significantly less stress–strain than Sn–Cu–Ni/Cu solder joints, due to the reduction of Cu6Sn5 layer thickness, fatigue life of solder joints can be enhanced by three times.

Influence of External Interface Normal Stress on the Growth of Cu–Sn IMC During Aging

A U-shape clamp was designed to apply stress perpendicular to the interface of Cu/Sn/Cu solder joints, and its influence on the growth behavior of Cu–Sn intermetallic compound (IMC) during thermal aging at 150 °C was investigated. The results show that compared with the sample at general stress-free state, the growth rate of IMC under compression is faster, while that under tension is slower. Moreover, the interface between IMC and Sn is smoother under compressive stress, and the corresponding IMC grains are smaller and more uniform than that under tensile stress. According to the growth kinetic analysis, the growth of IMC under general, compressive and tensile states is all controlled by the combination of grain boundary diffusion and volume diffusion with a similar growth exponent (n ≈ 0.4). However, external stress can affect the Ostwald ripening process of grain growth, causing a change of grain size and grain boundary density in the IMC layer. As a result, the IMC growth behavior at the interface of the solder joint will be affected by the applied external normal stress.

The interfacial Cu–Sn intermetallic compounds (IMCs) growth behavior of Cu/Sn/Cu sandwich structure via induction heating method

Forming full IMC solder joint technology has become one of the leading candidates to replace conventional high temperature Pb-based solder for wide bandgap (WBG) power modules (SiC and GaN) due to its excellent thermo-stability and high electrical/thermal conductivity. Few studies were investigated the formation and growth mechanism of interfacial Cu–Sn IMCs layer of Cu/Sn(10 μm)/Cu system during induction heating method. The results showed that the growth behavior of Cu–Sn IMCs of the Cu/Sn interface by induction heating method was different from Cu–Sn IMCs growth behavior of the Cu/Sn interface by conventional soldering method. The Cu6Sn5 thickness increased by Cu/Sn solid–liquid interfacial reaction before the bonding time of 45 s and then decreased by Cu6Sn5/Cu solid–solid interfacial reaction within the bonding time of 60 s. The Cu3Sn thickness increased by solid Cu/liquid Sn interfacial reaction and solid Cu6Sn5/solid Cu interfacial reaction within the bonding time of 60 s. A formation mechanism model of Cu–Sn compounds was also presented. The mathematic model of Cu layer consumption at different temperature was also illustrated, which indicated that higher temperature is in favor of the consumption of Cu layer. By knowing the relationship between the thickness of Cu layer on SiC power device at different temperature could be designed when evaluating the reliability of device by induction heating process.

Growth behavior of Cu, Ni and Cu/Ni electrodeposited microwires within porous Si

In this paper, a systematic growth behavior of Cu, Ni and Cu/Ni microwire arrays in porous silicon (PSi) templates is presented. After preparation of PSi templates via anodizing in HF solution, such microwires are successfully grown into PSi templates by electrodeposition method. Systematic scanning electron microscopy (SEM) imaging reveals that Cu seed nucleation occurs at the bottom and Ni seed nucleation starts on the wall of the silicon pores. The different growth models are explained according to the observed diffusion coefficients of ionic elements in electrodeposition baths. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) were used to further observe the structural characteristics of the grown microwires. We believe that this work can be used in developing microwires with desired structural characteristics.

Effect of microstructure on the fatigue crack growth behavior of Cu–Be–Co–Ni alloy

The fatigue crack growth (FCG) behaviors of Cu–Be–Co–Ni alloy subjected to interrupted aging (IA), normal aging (NA) and overaging (OA) treatment were discussed. The distinctions in microstructure of the alloys after various aging treatments led to different FCG behaviors. In order to understand the different FCG behaviors, a model based on the reversible plastic zone (RPZ) size and microstructural factors was applied in this study. At the relatively low stress intensity factor range (ΔK < 17 MPa m1/2), the RPZ size of each sample was smaller than the corresponding grain size, so the fatigue crack propagated inside the grain and adjacent to the grain boundaries (GBs). For the IA alloy, fine and coherent γ″ precipitates which could be sheared by dislocations promoted the fatigue crack resistance, leading to the decrease of FCG rate. When the value of stress intensity factor range becomes higher (ΔK > 21 MPa m1/2), the RPZ size of each sample was 1–2 times of the corresponding grain size. Consequently, the crack trended to grow along GBs. For the OA alloy, the crack propagated along the interfaces between the discontinuous precipitation (DP) cells and parent phase. The tortuous interfaces hindered the propagation of the fatigue cracks, resulting in the reduction of FCG rate.

In Situ Surface X-Ray Diffraction Studies of the Influence of the PEG-Cl-Complex on Homoepitaxial Electrodeposition on Cu(001)

The influence of polyethylene glycol (PEG) on the atomic-scale interface structure and Cu growth behavior of Cu(001) in chloride-containing electrolyte was investigated by in situ surface X-ray diffraction. Studies in Cu-free solution unambiguously verify the presence of the ordered c(2 × 2) chloride adlayer in the presence of the polymer as well as reversible Cl adsorption/desorption and an order-disorder transition in the adlayer. The partially ordered chloride adlayer is found over a wider potential range as compared to PEG-free electrolyte, indicating stabilization of this adsorbate phase. Crystal truncation and superstructure rod measurements reveal that the polymer interacts more strongly with the partially c(2 × 2) Cl covered surface than with the close-packed c(2 × 2) adlayer at saturation coverage. In Cu-containing electrolyte layer-by-layer growth was observed at potentials ≤ −0.35 V vs. Ag/AgCl. The deposition rate was significantly reduced as compared to PEG-free electrolyte, providing clear evidence of inhibition on the atomic-scale. At more positive potentials a crossover to 3D growth and increasing surface roughness is found.

Properties of Cu(In,Ga)Se2 Thin Film Solar Cells on Ga Temperature Variation

In this paper the effect the Ga/(In+Ga) ratio, which was controlled by Ga cell temperature, on the growth behavior of Cu(In,Ga)Se2 (CIGS) thin film and its photovoltaic performance is presented. It was found that both the grain size and the void density of CIGS layer decreased due to higher incorporation of Ga in CIGS by increasing Ga temperature. It was revealed that the CIGS films satisfying the composition ratio of Ga/(In+Ga) = 0.3∼0.4 and Cu/(In+Ga) = 0.84∼1.04, which were obtained at the Ga temperature of 1033∼1035°C, has the comparable diffraction intensity of (112) and (220) peaks. The (112)/(220) peak ratio of either Cu-rich or heavily Cu-poor CIGS films was found to deviate from unity and the solar cells made at these composition range showed lower photovoltaic performances. The highest efficiency of solar cell obtained by adjusting Ga cell temperature was 8.93% on device area of 0.16 cm2 (fill factor, open circuit voltage, and short circuit current were 50.34%, 576 mV and 30.79 mA/cm2, respectively).

Hollow oxide formation by oxidation of Al and Cu nanoparticles

The formation of hollow metal oxide nanoparticles through the oxidation process at low temperatures from 295 to 423 K has been studied by transmission electron microscopy for Cu, Al, and Pb. For Cu and Al, hollow oxide nanoparticles are obtained as a result of vacancy aggregation in the oxidation processes, resulting from the rapid outward diffusion of metal ions through the oxide layer during the oxidation process. On the other hand, Pb nanoparticles turn to solid PbO because the diffusivity difference DPb&amp;lt;DO in PbO does not lend itself to the formation of vacancy clusters. The oxide growth behavior of Cu and Al nanoparticles of a larger size at 423 K are summarized as follows: (i) for Al, the rapidly forming oxide layer on its surface stops growing once it reaches a critical thickness of about 1.5 nm, (ii) the growth of Cu2O continues until hollow Cu2O of a certain thickness is formed. This suggests the occurrence of two different diffusion processes in the formation of hollow oxides: the rapid outward diffusion of metal ions based on the Cabrera–Mott theory plays an important role in the formation of hollow Al-oxides, whereas the Kirkendall effect at the Cu∕Cu2O interface, where Cu diffuses much faster than oxygen, brings about the formation of hollow Cu2O.

Initial growth behavior of Cu(In,Ga)Se 2 on molybdenum substrates

We study the initial growth stage of Cu(In,Ga)Se 2 on Mo films on glass, as the typical back contact for Cu(In,Ga)Se 2 solar cells. A thermal evaporation process deposits Cu(In,Ga)Se 2 of nominal 3 nm thickness at different rates R and substrate temperatures T Sub. An ultrahigh resolution scanning electron microscope serves to visualize the nucleation behavior. The deposited Cu(In,Ga)Se 2 forms three-dimensional isolated nuclei, known as Volmer–Weber growth mode. Deposition rate R and substrate temperature T Sub control the areal density n of the Cu(In,Ga)Se 2 nuclei. For the growth on polycrystalline Mo substrates fabricated by sputter process, we observe a power law dependence between the island density n and the deposition rate R, and an exponential dependence of the island density n on substrate temperature T Sub. The theory of homogeneous nucleation explains the Cu(In,Ga)Se 2 cluster formation on sputtered Mo substrates and the dependence of the island density on the growth conditions. On electron gun evaporated molybdenum, the cluster growth shows a similar behavior, but the nucleation mechanism deviates from the model of homogeneous nucleation and strong island density fluctuations occur.

Effect of interfacial interactions on the initial growth of Cu on clean SiO2 and 3-mercaptopropyltrimethoxysilane-modified SiO2 substrates

The effect of interfacial interactions on the initial growth of Cu on clean SiO2 and 3-mercaptopropyltrimethoxysilane (MPTMS)-modified SiO2 substrates by sputter deposition was studied using transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. Plasma damage during sputter deposition makes surfaces of MPTMS-modified SiO2 substrates consist of small MPTMS islands several tens of nanometers in diameter and bare SiO2 areas. These MPTMS islands are composed of disordered multilayer MPTMS aggregates. The initial growth behavior of Cu on MPTMS-modified SiO2 substrates differs from that on clean SiO2 substrates, although Cu grows in three-dimensional-island mode on both of them. After a 2.5-monolayer Cu deposition on clean SiO2 substrates, spherical Cu particles were formed at a low number density of 1.3×1016 /m2 and at a long interparticle distance of 5 nm. In contrast, after the same amount of deposition on MPTMS-modified SiO2 substrates, Cu particles preferentially grow on MPTMS islands at a high number density of 3.9×1016 /m2 and at a short interparticle distance of 3 nm, but do not grow on bare SiO2 areas. The increased number density and the decreased interparticle distance indicate that Cu has a lower mobility on MPTMS islands on MPTMS-modified SiO2 substrates than on clean SiO2 substrates. This difference in Cu mobility is attributed to the enhanced interfacial interactions between Cu and S on MPTMS islands on MPTMS-modified SiO2 substrates via the formation of Cu–S bonds, compared with the relatively weak interfacial interactions between Cu and Si or O on clean SiO2 substrates.

Nucleation and growth behavior of Cu–Al precipitates in He implanted and annealed aluminum

The effects of He on the thermal evolution of Cu–Al precipitates produced after Cu + and He + implantation into pure Al foils were analyzed as a function of the implanted He fluence and post-implantation thermal annealing temperature. The profiles of Cu and He were measured via Rutherford backscattering (RBS) and elastic recoil detection analysis (ERDA) techniques. The precipitate and bubble morphology were investigated by transmission electron microscopy (TEM). In comparison to a sample implanted only with Cu +, we observe that the presence of He leads to larger Cu–Al precipitates upon low-temperature annealing. For high-temperature annealing the situation is opposite. This behavior is discussed considering precipitate nucleation and growth processes affected by the reduction in the vacancy field due to the formation of He bubbles.