Grain Size Of Cu Research Articles

Microstructure-dependent oxidation-assisted dealloying of Cu0.7Al0.3 thin films

In this paper, the oxidation-assisted dealloying (OAD) of Cu0.7Al0.3 films with different microstructures which were obtained by high vacuum annealing at different temperatures were studied using powder X-ray diffraction, field-emission scanning electron microscopy and energy dispersive X-ray analysis. It was observed that different microstructures such as eutectic mixture or solid solution, the grain size of Cu or Al component in eutectic-mixture Cu0.7Al0.3 films affected the corrosion morphology greatly. It thus provided a practical route to fabricate flexible CuO porous nanostructure-films (PNFs) with controllable pore size, porosity, block size and shape. Further, the underlying OAD mechanisms for the structure-resultant different corrosion morphologies of Cu0.7Al0.3 films were also explored. In these senses, the study is suggestive and crucial to both the mechanism understanding of OAD process and the technical controlling of PNF fabrication.

Suppression of void nucleation in Sn3.0Ag0.5Cu/CU solder joint by rapid thermal processing

Electrodeposited (ED) Cu was prepared and exhibited a strong voiding propensity at the Cu3Sn/Cu interface in the subsequent Sn3.0Ag0.5Cu/Cu solder joint. However, we found that the rapid thermal processing treatment could significantly reduce the voiding propensity of ED Cu. After rapid annealing, the grain size of Cu was obviously increased, which was found to reduce the amount of effective vacancies and lower the driving force of void formation. Meanwhile, the ED Cu before and after rapid annealing was analyzed using X-ray photoelectron spectroscopy, and it can be found that there did exist additives remained in the Cu layer during electroplating process. However, after rapid annealing treatment, some residuals would evaporate, and the others would decompose and react with Cu, which would change the residuals from the free state to the “deactivated” state and make them lose their acting as the precipitate for the heterogeneous nucleation. Thus, the Cu3Sn/Cu interface with few voids was finally formed.

Effect of Cu grain size on the voiding propensity at the interface of SnAgCu/Cu solder joints

Effect of Cu grain size on void formation at the interface of SAC305 (Sn3.0Ag0.5Cu)/Cu solder joint was studied. The joints with ED CCL (Electrodeposited Copper Clad Laminate) substrates exhibited a strong voiding tendency. But this tendency was significantly reduced after annealing treatment at 150°C for 1000h. At the same time, no voids were found at the interface of SAC305/HPOFC (High Purity Oxygen Free Copper, 99.9999wt%) plate. It was found that the grain size of annealed ED CCL increased by two orders of magnitude than that of ED CCL, but it was just about half of the grain size of HPOFC plate. The smaller grain size of Cu could increase the amount of grain boundaries, thus increasing the amount of effective vacancies (EVs). Under gradient of concentration, these EVs would coalesce to form voids at the interface of Cu3Sn/Cu. Therefore, to lower the tendency of void formation at the interface, increasing the size of grain is an effective way.

Mechanical property evaluation of TSV-Cu micropillar by compression method

A micro-compression test method was presented to evaluate the mechanical property of the TSV-Cu micropillar in this paper. Firstly, the test sample containing TSV-Cu micropillar was prepared by MEMS micromachining technology. Then, the mechanical property of TSV-Cu micropillar was measured by a self-made micro-compression system. Finally, the effect of thermal treatment on the mechanical property of TSV-Cu micropillar was studied. The experimental results showed that the average yield strength (σ0.2) of the TSV-Cu micropillar was 167 MPa. But it decreased to 137 MPa after being thermally treated at 400°C for 1 hour, which was probably due to the increased grain size of Cu.

Effect of pH on the Microstructure and Purity of Copper-Coated Tungsten Composite Powders Prepared by Electroless Plating

High-performance copper-coated tungsten composite powders were successfully prepared using electroless plating at an appropriate pH in the plating bath. The effect of pH value in the plating bath on the microstructure and purity of the coated Cu layer was studied systematically. With the increase of pH in the bath, the surface roughness, particle size and average grain size of coated Cu increased, and the particle shape gradually changed from round into square block. At pH 12–12.5, coated Cu was highly pure with very little oxygen content (less than 0.09 wt.%). The promotion effect of the increased pH on both main electroless plating reaction and side reactions causes the changes of surface morphology, average grain size of Cu and the oxygen content in the composite powders.

Structural and optical study of Li doped CuO thin films on Si (100) substrate deposited by pulsed laser deposition

• Cu 1 − x Li x O ( x = 0.0, 0.05, 0.07 and 0.09) thin films are successfully grown by PLD. • Raman and PL spectra confirm the single-phase formation of CuO thin films. • FESEM and AFM show that the grain size of Cu 1 − x Li x O thin films is ∼35 to 79 nm. • A reduction in optical band gap is observed from 2.99 to 2.76 eV for x = 0 to 0.09. In the present study, we report structural and optical properties of Cu 1 − x Li x O thin films grown on Si (1 0 0) substrates by pulsed laser deposition at different doping concentrations ( x = 0.0, 0.05, 0.07 and 0.09). The XRD spectra indicates the formation of polycrystalline CuO thin films and the crystallite size, calculated through XRD data is found to be increased from 7 to 14 nm for the samples with x = 0 to 0.09, respectively. FESEM analysis shows that the average size of Cu 1 − x Li x O nanostructures increases from 47 to 97 nm and AFM analysis also shows that the average size of Cu 1 − x Li x O nanostructures increases from 35 to 79 nm by increasing the Li doping concentrations from x = 0 to 0.09, respectively. Energy dispersive X-ray analysis with elemental mapping of the Li-doped CuO thin films shows that the Li dopants are incorporated homogeneously into the CuO thin film matrix. Moreover, Raman and photoluminescence spectra also confirm the single-phase formation of CuO thin films. A significant reduction in optical energy band gap is observed from 2.99 to 2.76 eV with an increase of Li concentration from 0 to 9%, respectively.

Tension-induced softening and hardening in gradient nanograined surface layer in copper

With surface mechanical grinding treatment, a gradient nanograined (GNG) surface layer is produced on a bulk coarse-grained (CG) pure Cu, where the grain size increases gradually from 20 nm (topmost surface) to micrometer scale. Microhardness measurements of the GNG/CG sample after tension revealed that tension induces softening for grains smaller than 165 nm and induces hardening above this size. This critical size agrees with the strain-induced saturation grain size of Cu subjected to severe plastic deformation.

Effects of TiB2 on microstructure of nano-grained Cu–Cr–TiB2 composite powders prepared by mechanical alloying

Nano-grained CuCr25 and CuCr25–(2wt%–10wt%)TiB2 composite powders were prepared by mechanical alloying method. The milled powders were characterized by SEM, FSEM, EDS, XRD, TEM and HTEM. The results indicate that average grain size of Cu, Cr and TiB2 are less than 50nm and each component disperses uniformly. The grain size of Cu and Cr decreased and the lattice distortion increased gradually as the TiB2 content increased from 2wt% to 10wt%. The ultrafine TiB2 particles play the role of “micro-milling balls” to compact, micro-etch, micro-frict and micro-cut with Cu and Cr so that the grain refinement and lattice strain are promoted.

The effect of Cu grain size on transition from EHL to BL regime (Stribeck curve)

Abstract Recently friction and wear of copper (Cu) samples (the average grain size, d = 30 μm) rubbed against a hardened steel in steady friction were studied. The effects of load and sliding velocity were interpreted by the Stribeck curve and the transitions from elasto-hydrodynamic lubrication (EHL) to boundary lubrication (BL) region were analyzed. It was shown that the wear rate is proportional to a load both in the EHL and in the BL regions. The hardness of thin surface layers saturates during repeating sliding of Cu that is close to the hardness of nanocrystalline Cu produced by different severe plastic deformation (SPD) processes. The present investigation was initiated with three objectives similar to our previous works with the Cu samples: first, to study the friction and wear behavior of Cu surfaces with different grain sizes under different lubricant conditions; secondly, to examine the structural evolution of Cu subsurface layers under friction in different contact conditions and thirdly, to evaluate the effect of grain refinement by equal channel angular pressing (ECAP) on friction and wear. The Stribeck curves for the Cu-steel pairs with different virgin grain sizes of Cu ( d = 1 μm, 30 μm and 60 μm) are presented. All Stribeck curves have the similar shape and only shifted depending strongly on virgin hardness of the Cu samples. The transitions from one lubricant region to another depend on the virgin grain size. The lesser the grain size of Cu, severe the condition of transition to BL region. Grain refinement by ECAP ( d = 1 μm) shifts the Stribeck curve in the range of severe contact conditions (high loads and low sliding velocities). Preliminary severe plastic deformation of Cu samples leads to remarkable decreasing the wear loss in comparison to coarse grain size samples. The hardness of thin surface layers (∼1 μm) saturates during repeating sliding of Cu and this value is close to the hardness of nanocrystalline Cu produced by different SPD processes. Since plastic deformation and wear occur in ML and BL regions, the known lubrication numbers cannot be used for description of the transitions to these lubrication regions. New parameter, K , as the ratio between the hardness values of tested and annealed samples is introduced in lubrication number in order to take into account the effect of grain size on friction and wear in different contact conditions. Application of K allows a prediction the effect of grain size on the transitions from one lubrication region to another.

Study on Cu-Based Catalysts for Synthesis of Indole

A series of Cu-based catalysts for the synthesis of indole by the reaction of aniline and ethylene glycol were prepared and characterized by ICP-AES and XRD. The results indicated that the activity and stability of Cu/SiO2 catalyst was increased after adding Zn, Mn, Cr and Fe promoters. Mn promoter was favorable for the dispersion of Cu, Zn, Cr, Fe and enlarged the specific surface area of catalysts. It could be seen that the catalysts prepared by impregnation method had better stability and higher activity than the catalysts prepared by co-precipitation method. The catalysts with small grain size of Cu had higher activity than those with big grain size. Some catalysts showed excellent performances in this reaction.

Bulk Nanocrystalline Cu Produced by High-Energy Ball Milling

The preparation, mechanical properties, grain size and thermal property of bulk nanocrystalline Cu (BNC-Cu) were investigated in this paper. BNC-Cu can be produced by in situ consolidation of pure Cu powder with high-energy ball milling at room temperature; the average grain sizes of Cu samples decreased with the increasing of ball milling time before 9 h because the grain refining velocity was bigger than the grain growing velocity in this stage. When the ball milling time was beyond 9 h, the average grain size reached a steady minimum value about 27.5 nm. The microhardness of BNC-Cu samples increased with the extending of ball milling time in the first 9 h because the dominating factor was the hardening effect caused by grain refinement and work hardening rather than softening in this stage. BNC-Cu gained its highest microhardness about 1.59GPa when the ball milling time reached 9 h. Subsequently, the microhardness of BNC-Cu slightly fluctuated around this value. Because there were numerous triple grain boundaries and the interaction among different crystal defects in BNC-Cu, BNC-Cu showed outstanding thermal stability when it was annealed in the range of 100°C to 400°C.

Thermal Stability of Graphite/Copper Nanocrystalline Composite Powders Prepared by High Energy Mechanical Milling

To provide reference for choosing technological parameters of subsequent powder densification, thermal stability of 3 h-milled 3 wt% graphite/copper nanocrystalline composite powders were investigated with such analytical methods as scanning electron microscopy (SEM), back-scattered electron images and X-ray diffraction (XRD). The results show that diffraction peak of graphite in XRD pattern is absent because of too small graphite particle. No major variation of grain size of Cu with annealing temperature is observed. Accumulation and growth of graphite phase aren’t seen. The microhardness is nearly constant for the annealed powders. Therefore, 3 h-milled 3 wt% graphite/copper nanocrystalline composite powders possess good thermal stability.

New function of hydrogen in materials

Useful functions of hydrogen found recently in materials are reviewed with newly obtained results. By hydrogen absorption–desorption heat-treatment, grain size of Cu–Ti alloys are refined to several 10 nm. Simultaneous improvements of electrical conductivity and mechanical strength for Cu–3 mass%Ti alloy were achieved, and the values of 21%IACS and 1100 MPa were obtained, respectively. Hydrogen treatment led to a reduction in the grain size in α- and β-rich α + β type alloys to about 3 and 0.3 μm, respectively. The yield strength of fine-grained α- and β-rich α + β type alloys is greatly improved. Curie temperature of La(Fe x Si 1− x ) 13 compounds is controlled by the content of hydrogen. It is also demonstrated that the La(Fe x Si 1− x ) 13 H y compounds can be applicable as new-type pressure sensing materials. Polymer-coated CuPd nanoparticles were synthesized by chemical reduction method, and B2 phase in CuPd alloy nanoparticles is effectively formed by the hydrogenation treatment.

Estimate of the Hall-Petch and Orowan effects in the nanocrystalline Cu with Al 2O 3 dispersoid

Nanocrystalline (nc) Cu materials with Al 2O 3 dispersoid (Cu-4 vol. % Al 2O 3) were successfully produced by a simple cryo-milling at 210 K with a mixture of Cu 2O, Al, and Cu ingredient powders, followed by hot pressing at 1123 K. The results of microstructural analysis showed that the hot pressed material was comprised of a mixture of Cu matrix (25.1 nm) with a homogeneous size distribution of the Al 2O 3 dispersoid (∼4 nm in radius). Grain size of Cu was measured by XRD (Scherrer's formula); dispersoid size of Al 2O 3 was confirmed by STEM-EDS (Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy) and TEM (Transmission Electron Microscopy). Result of micro hardness tests indicated that the hot pressed materials have a significantly high hardness (265 ± 8, VHN; 2.6 GPa, SI units) at room temperature. Two strengthening mechanisms are considered for high hardness: strengthening by grain refinement and dispersion hardening. An estimate of the individual strengthening effect to total strength of the material at room temperature, based on the Hall-Petch and Orowan equations, is presented.

Mechanical and electrical properties of Cu–Ta nanocomposites prepared by high-energy ball milling

Cu–Ta bulk nanocomposites with varying amounts of Ta were produced by high-energy ball milling followed by compaction and sintering. The final crystallite size of Cu and Ta during the high-energy ball milling depends on the deformation behavior of the Cu–Ta composite rather than the melting point of the elements. The grain size of the nanocomposites after sintering is less than 100nm. The Cu–Ta nanocomposites showed a superior sintering behavior compared with the microcomposites. The hardness and compressive strength of the Cu–Ta nanocomposites are 3.6–3.8 and 3.6–5 times higher than that of the microcomposites, respectively. The electrical resistivity of the nanocomposites is slightly higher than that of the microcomposites. However, the normalized hardness to resistivity ratio of the nanocomposites is higher than that of the microcomposites, which signifies that it is the increase in hardness rather than in resistivity that is predominant. A major contribution to the strength of the nanocomposite comes from the nanocrystalline grain size of Cu, in accordance with the Hall–Petch relation.

Study of fabrication of Cu film on PFA by sputtering

Abstract Currently, chemical pretreatment and electroless plating are used to fabricate Cu films on perfluoroalkoxy vinyl ether (PFA) copolymer. In order to reduce the wastage of water during chemical pretreatment and electroless plating, we have investigated the fabrication of Cu films by a dry process as an alternative. In the present report, we have investigated the fabrication of Cu film on the PFA by using a conventional RF sputter deposition apparatus. An Ar ion sputter-etching pretreatment is performed on the PFA prior to sputter deposition; however, it does not significantly influences the peel strength and grain size. The grain size of Cu influences its resistivity in the present experiments. The resistivity increases with decreasing grain size. This result is explained by considering the scattering of conduction electrons at the grain boundaries. Further, substrate temperatures obviously influence the grain size of Cu and the peel strength between Cu and PFA. In particular, for substrate temperatures above 150 °C, the grain size and peel strength increase drastically. We can use the Cu film fabricated on the PFA substrate above 150 °C as a seed layer for CuSO 4 electroplating.

Magnetic behavior of nanocrystalline Cu–Ni–Co alloys prepared by mechanical alloying and isothermal annealing

The structural and magnetic properties of nanocrystalline Cu–Ni and Cu–Ni–Co alloys prepared by mechanical alloying and subsequent isothermal annealing in the temperature range of 350–650 °C has been investigated systematically. The average grain sizes of Cu–Ni and Cu–Ni–Co alloy systems were found to be in the range of 5–8 nm after 30 h of milling and 21–40 nm after isothermal annealing of as-milled samples. Here, it is shown that the magnetic properties ( H c, M r and M s) of the nanocrystalline alloys undergo changes by the variation in microstructural constituents, grain size and evolution of phases. The alloy containing 10 wt% Co shows notable improvement in the magnetic properties. Phases present in the ball milled samples and the isothermally annealed ball milled product were identified and characterized by X-ray diffraction (XRD) and differential scanning calorimetric (DSC) techniques and the results were correlated with the magnetic properties of the alloys.

Grain size enlargement of Cu(InGa)Se 2 thin films by Hot Filament Melting process

Hot Filament Melting (HFM) process has been newly proposed to enlarge the grain size of Cu(In1–xGax)Se2 (CIGS) films grown by a mechanochemical process (MCP). When the substrate temperature was 500 oC and 600 oC and the current through the hot filament was 15A, we confirmed encouraging the sintering of CIGS grains. Additionally, when the substrate temperature was 700 oC, the melt of the CIGS grains at the surface was observed. The crystal structure of CIGS films after the process were analyzed by X-ray diffraction and Raman spectroscopy, and it was found that the CIGS films kept the chalcopyrite structure and that the formation of hetero-phase was not observed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

On the strain hardening exponent of Cu–26Ni–17Zn alloy

The relationship between strain hardening exponent n and grain size of Cu–26Ni–17Zn alloy was investigated. n is found to be independent of grain size in the range of 15–120 μm. Analysis of constants in Hollomon equation (σ ɛ = Kɛ n ) as a function of grain size was carried out. The results reveal that the constant K follows Hall–Petch relation, i.e. proportional to d −1/2 whereas n is independent of d −1/2.

Filling a Narrow and High Aspect-Ratio Trench with Electro-Cu Plating

Copper electroplating has been used for making interconnections in large-scale integration (LSI). Sub-100-nm-wide, deep trenches with aspect-ratios over 6 were fully filled by optimizing DC and pulse electroplating processes. Grain sizes of Cu of sub-100-nm wide trenches after electroplating were 70 nm for DC electroplating and 58 nm for pulse electroplating. The Cu grain sizes of Cu interconnects by DC plating after electroplating increased with the annealing temperature.