Thickness Of Cu Research Articles

Investigating the effect of Cu underlayer and FTO etching towards photoelectrochemical performance enhancement of Cu2O photoelectrode

Cuprous oxide (Cu2O) exhibits potential as a photoactive material for photoelectrochemical water splitting, owing to its appropriate bandgap, efficient charge carrier separation, and ability to enhance solar-driven hydrogen production. This study investigates the influence of substrate etching, Cu underlayer and Cu2O electrodeposition time, and annealing time on enhancing the photoelectrochemical (PEC) performance. Electrodeposition and thermal oxidation techniques were used to fabricate the Cu2O/Cu/FTOe-A photocathode. It has been observed that FTO etching improves adhesion, light transmission, and efficiency. A Cu underlayer also impacts the PEC performance, wherein an ideal thickness of Cu leads to enhanced PEC performance. This study also focuses on the annealing time that leads to CuO layers and nanowires forming on the Cu2O surface. The structural and chemical changes before and after annealing are confirmed via XRD, XPS, AFM and FESEM analyses. UV–Vis analysis also reveals that the presence of Cu underlayer, FTO etching, and the annealing process affect the electrical properties and light absorption capacities of the Cu2O photoelectrode. Electrochemical impedance analysis (EIS) and Mott-Schottky analysis have provided insights into the enhanced charge transfer properties and band bending in the Cu2O/Cu/FTOe-A, resulting in enhanced PEC performance. Overall, this study provides significant insights into the understanding and enhancement of Cu2O/Cu/FTOe-A photocathodes for potential use in PEC water splitting applications.

Design of Silicon Core Coaxial TSVs to Reduce Crosstalk Effects for 3D IC Applications

This paper presents the effectiveness of the copper (Cu)-based coaxial through silicon vias (CTSVs) to reduce crosstalk noise and propagation delay. In the proposed CTSVs, the polymer liners are used as insulating material which cancels the crosstalk functional failures. The impacts of the proposed CTSVs on the electrical performance are noticed for different parameters and properties of the material. Simulations of the proposed CTSVs are executed using the standard HSPICE and SYMICAD tools. The results indicated that the effects of crosstalk are reduced using the polymer liners instead of silicon dioxide (SiO2) liners in the proposed CTSVs. The electrical performances of the proposed CTSVs are investigated for various thicknesses of Cu and BCB. Furthermore, a comparative study has been carried out for the SiO2 and benzocyclobutene (BCB) liners. It is observed that BCB liner-based CTSVs crosstalk noise and delay values are reduced by up to 25.06% and 27.8% compared to the SiO2 liner-based TSVs.

Efficient Orbitronic Terahertz Emission Based on CoPt Alloy.

Orbitronic devices operate by manipulating orbitally polarized currents. Recent studies have shown that these orbital currents can be excited by femtosecond laser pulses in a ferromagnet such as Ni and converted into ultrafast charge currents via orbital-to-charge conversion. However, the terahertz emission from orbitronic terahertz emitters based on Ni is still much weaker than that of the typical spintronic terahertz emitter. Here, this work reports a more efficient light-induced generation of orbital current from a CoPt alloy, and the terahertz emission from CoPt/Cu/MgO is comparable to that of benchmark spintronic terahertz emitters. By varying the composition of the CoPt alloy, the thickness of Cu, and the capping layer, this work confirms that THz emission primarily originates from the orbital accumulation generated within CoPt, propagating through Cu, followed by subsequent orbital-to-charge conversion due to the inverse orbital Rashba-Edelstein effect at the Cu/MgO interface. This study provides strong evidence for the efficient orbital current generation in CoPt alloy, paving the way for efficient orbital terahertz emitters.

Improvement of microstructure and mechanical properties of laser welded Al-Si coated 22MnB5 steel joints by austenitic element copper

In this experiment, the effects of different copper foil thicknesses on the morphology, structure, and mechanical properties of laser lap welded 22MnB5 steel joints were studied. The aim was to reduce the damage of Al-Si coating and increase the mechanical properties of welded joints. As the thickness of copper foil increases from 0 to 100μm, there was a gradual decrease in the presence of δ-ferrite in the fusion zone (FZ) and fusion boundary (FB), while the copper-rich content of lath martensite (LM) gradually increased. The reason was that Cu is an austenite element which can expand the γ phase area and play a stabilizing and strengthening role. The result of JmatPro software can support it. It found peritectic reaction (L+δ→γ) range expanded from 1414 to 1422°C to 1436–1453°C which led to more γ phases formed during the solid-state phase transition (δ→γ) at high temperature. Based on this phenomenon, as the copper foil increased (0–100μm), the joint tensile strength increased from 361 MPa to 706 MPa. However, after adding too much copper foil (200μm), the microstructure of FZ varied to a copper-rich phase (ε-Cu) with low hardness and brittleness which adhered to the martensite grain boundaries and reduced the bonding force of the crystal boundaries, so the the mechanical properties of the weld joint seriously reduced (232 MPa). When the copper foil was thin or non-existent (0–30μm), there was still more delta ferrite in FB (low strength and brittle), and the fracture type of the joint mainly appeared as a cleavage fracture. When adding 100μm copper foil, the fracture expressed ductile fracture due to the interfacial fracture due to the lack of δ-ferrite in FB. If the thickness of Cu increased to 200μm, the fracture changed back to FB which expressed a quasi-cleavage fracture.

Design and performance investigation of CIGS/SWCNT tandem solar cell for efficiency improvement

This research work demonstrates the design and simulation of highly efficient tandem solar cell by using SCAPS-1D software. This tandem solar cell has been designed with a higher bandgap Copper Indium Gallium Diselenide (CIGS) absorber as a top cell and a lower bandgap Single Wall Carbon Nano Tube (SWCNT) absorber as a bottom cell, which are arranged in the series connection. Firstly, both top and bottom solar cells were analysed under standalone afterward, tandem configuration was developed with the top cell illumined by AM 1.5 spectrum and the bottom cell illumined by AM 1.5 filtered by top cell spectrum. The effects of absorber thickness, doping density, and bandgap on the output characteristics of the solar cell are also investigated. The current matching of both cells is attained by tuning the bandgap and thickness of Cu(In1-xGax)Se2 absorber of the upper cell. The remarkable efficiency of 38.91 % (Voc = 1.3441 V, Jsc = 37.87 mA/cm2 and FF = 76.41 %) is attained of the proposed CIGS/SWCNT tandem device at a thickness of 860 nm and 2000 nm for absorber of top and bottom cell respectively. The results of this research suggest a route for the fabrication of CIGS/SWCNT tandem solar cell with high efficiency.

Micro X-ray fluorescence device based on monocapillary ellipsoidal lens for thin film thickness measurement

X-ray fluorescence (XRF) is a crucial non-destructive technique for determining the thickness of thin films or coating materials to ensure their optimal performance. In order to further expand the application of XRF in thin film thickness analysis, we have developed an inner-wall coated elliptical monocapillary X-ray lens (EMXRL), which has a larger acceptance angle and higher utilization efficiency for light sources compared to traditional inner-wall uncoated EMXRL. In addition, we have built a laboratory micro-X-ray fluorescence (Micro-XRF) thickness measurement device based on coated EMXRL. Compared to common XRF devices, it has a smaller X-ray spot size and higher intensity gain, resulting in smaller spatial resolution and higher detection efficiency in XRF thickness measurement applications. We established a standard curve in the range from 0.85μm to 56.5μm for measuring the thickness of Cu coating on silicon using this Micro-XRF device. The experimental results show that the micro-area thickness measurement device, based on the standard curve method, can measure the thickness of Cu coatings from 0.85μm to about 30.00μm with a relative deviation of about 3%. Within the thickness range from about 30.0μm to 56.5μm, the relative deviation of the measured thickness increased and was larger than 5%. This larger relative deviation mainly resulted from the greater absorption from the thicker coating. Furthermore, We used the device to perform mapping scans on scratched areas of Cu-plated circuit board to verify its usefulness. The results show that the device has the advantages of simplicity and speed, and has potential applications in fields such as semiconductors.

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Copper (Cu) metal nanoparticles were deposited onto FTO glass using the electrodeposition method. The precursor used was CuSO4×5H2O with Na2SO4 as the inorganic additive. The formation of Cu was characterized using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). This study investigated the impacts of the electrodeposition method (direct electrodeposition vs. pulse electrodeposition), voltages (‑0.4 V and ‑0.8 V), electrodeposition time (60s to 900s) and pulse cycles (50 cycles to 300 cycles), and FTO etching (fixed to 20s etching) towards the morphology and adhesion of Cu deposited. The grain size and thickness of Cu deposited vary with deposition time and pulse cycles. The voltage of -0.4 V successfully deposits shiny, metallic brown Cu onto FTO glass. Meanwhile, the voltage of -0.8 V gives powdery brown Cu on the surface. In addition, compared to direct electrodeposition (DD), pulse electrodeposition (PD) provides a more compact and homogeneous coverage of Cu onto FTO glass. The tape-test results also indicate that FTO etching by electrolysis reduction can improve the adhesion strength between deposited thin Cu film and the FTO glass. This work demonstrates a facile electrodeposition technique with substrate etching as an effective deposition of Cu metal with the potential for application in a wide range of fields.

Stress Analysis of Flexible GaInP/GaAs/InGaAs Solar Cells Based on Cu Thin‐Film Substrates

The stress of GaInP/GaAs/InGaAs triple‐junction (3J) solar cells with different thicknesses of Cu thin‐film substrates is analyzed. X‐ray diffractometer and metallographic examination show that the unstable as‐deposited Cu film undergoes room‐temperature self‐annealing, which results in grain growth and changes the internal stress of the Cu film over time. A suitable Cu thickness (18 μm) for 3J solar cells is obtained, whose internal stress can offset the stress caused by the epitaxial mismatch. The flexible 3J solar cell with 18 μm Cu film has the lowest curvature of 8.24 m−1 under the combined effect of thermal stress and lattice mismatch stress. The photovoltaic conversion efficiency reaches 35.02% with the open‐circuit voltage of 3.03 V under AM1.5G spectrum. Cu films with a thickness of 14–28 μm have little effect on the optoelectronic properties of the final device. Reducing the curvature of lattice‐mismatched GaInP/GaAs/InGaAs solar cell devices is beneficial for realizing large‐scale flexible solar cell modules.

Thermally oxidized ultrathin copper film as low-cost hole-transport layer in planar perovskite solar cells

The use of inorganic materials is generally considered a prerequisite for the realization of inexpensive and long-lasting perovskite solar cells (PvSCs). Herein, we have demonstrated a low-cost, inorganic, ultrathin thermally oxidized copper film (Cu_Oxd) as a hole transport layer (HTL) in PvSC in p-i-n geometry with MAPbI3 as the photoactive layer. A highly reproducible technique of vapor deposition (magnetron sputtering) followed by thermal annealing has been used to deposit the Cu_Oxd layer over an ITO-coated glass substrate. The material properties of the Cu_Oxd film have been thoroughly investigated and their effect on photovoltaic properties and the photoactive absorbing layer has been studied in detail and correlated. Photovoltaic performance of the devices fabricated with different Cu_Oxd thicknesses has been measured and a maximum PCE of 11.44% has been obtained with a 5 nm thickness of Cu_Oxd layer as HTL with a pixel area of 0.25 cm2. The devices showed higher stability with T80 lifetime >1000 h without any encapsulation. With the ease of fabrication and compatibility with large-area devices, Cu_Oxd as HTL can be scaled up and also, help in the progress towards large-scale fabrication and commercialization.

Effect of Cu Coating on Microstructure and Properties of Al/Steel Welding–Brazing Joints Obtained by Cold Metal Transfer (CMT)

Adding alloy elements to develop excellent properties in Al alloy/steel welding–brazing joints to realize lightweight vehicle structures has become a feasible task. Here, CMT welding–brazing was used to realize the reliable connection of Al/steel with a Cu coating. Al alloy/steel welding–brazing joints with different thicknesses of Cu coating were designed to study the influence of Cu on microstructure composition, mechanical properties and corrosion resistance. Then, the action rule of the Cu element on the interfacial microstructure evolution was clarified. The results showed that the appropriate Cu coating could effectively inhibit the reaction of Al and Fe and reduce the thickness of interfacial brittle intermetallic compounds (IMCs). Moreover, Cu could react with Al, Fe and Si to promote the formation of the τ5-Al7.2(Cu,Fe)1.8Si phase and control the formation of the brittle θ-Fe(Al,Si)3 phase, which improved the toughness of IMCs. When the thickness of the Cu coating on the surface of steel was 10 μm, the tensile strength of the Al alloy/steel CMT welding–brazing joint reached a maximum of 138.7 MPa and the corrosion resistance of the joint reached the optimum level. However, when the thickness of the Cu coating increased to 20 μm, the IMCs’ thickness at the interface of the joint reached the minimum, but Cu reacted with Al to form a brittle Al2Cu phase under the higher Cu content, which deteriorated the tensile strength and corrosion resistance of joints. This work will provide an experimental and theoretical basis for developing good properties in Al/Cu-coating/steel welding joints.

Microstructure evolution, mechanical properties and tailoring of coefficient of thermal expansion for Cu/Mo/Cu clad sheets fabricated by hot rolling

The law of microstructure evolution and mechanical properties of hot roll bonded Cu/Mo/Cu clad sheets were systematically investigated and the theoretical prediction model of the coefficient of thermal expansion (CTE) of Cu/Mo/Cu clad sheets was established successfully. The results show that the deformation of Cu and Mo layers was gradually coherent with an increase in rolling reduction and temperature and excellent interface bonding was achieved under the condition of a large rolling reduction. The development of the microstructure and texture through the thickness of Cu and Mo layers was inhomogeneous. This phenomenon can be attributed to the friction between the roller and sheet surface and the uncoordinated deformation between Cu and Mo. The tensile strength of the clad sheets increased with increasing rolling reduction and the elongation was gradually decreased. The CTE of Cu/Mo/Cu clad sheets was related to the volume fraction of Mo. The finite element method can simulate the deformation and stress distribution during the thermal expansion process. The simulation result indicates that the terminal face of the clad sheets was sunken inward.

Coexisting lattice contractions and expansions with decreasing thicknesses of Cu (100) nano-films

Lattice parameters are a basic quantity in material characterization, and a slight alteration in lattice parameters directly affects the properties of materials. However, there are still considerable controversies as to whether lattice expansion or contraction occurs in metallic nanomaterials with size reduction. Here, the size dependences of the lattice parameter and surface free energy of clean Cu (100) films are investigated via simulations. Lattice parameters of the exposed surfaces contract, whereas lattice expansion occurs along the direction perpendicular to the surfaces with decreasing film thicknesses. This is striking since the metallic bonds usually lack strong directionality, and it is always regarded that the lattice variations in all directions are consistent. The contraction parallel to the surface is more severe than the expansion perpendicular to the surface in films. The lattices change from cubic to tetragonal with decreasing film thickness. Consequently, common contractions and occasional expansions of the lattice parameters of Cu nanoparticles have been observed in previous experiments. Increasing free energy and surface free energy with decreasing thicknesses is the thermodynamic origin of the lattice variations. Our study therefore provides a comprehensive physical basis for the surface effects on the lattice variations.

Stable lithium metal anode achieved by shortening diffusion path on solid electrolyte interface derived from Cu2O lithiophilic layer

• We found the lithiation of Cu 2 O film would participate in the SEI generation. • The thickness of Cu 2 O film can affect Li + diffusion path in the derived SEI layer. • The oxidation state/thickness of Cu 2 O film can be tuned by oxygen plasma rapidly. The stable operation of lithium metal batteries is crucial for high energy density requirements, but it is plagued by Li dendrite growth and unstable solid electrolyte interphase (SEI). Lithiophilic transition metal oxides (TMOs) have been studied extensively on Cu current collectors to stabilize lithium metal anodes by decreasing the Li nucleation overpotential, yet less is known about the SEI derived from the lithiation reaction of TMOs. Here we report a novel approach to regulate the SEI interface precisely, especially to construct a nanoscale inorganic-dominated SEI with shortened diffusion path by controlling the oxidization state of Cu 2 O film on Cu current collector. The highly stable cyclic performance is achieved by generating the thin SEI that contains dense inorganic inner layer and organic layer. Consequently, the lithium metal anode based on Cu 2 O/Cu current collector exhibits low and stable polarization voltage for an ultralong life-span (∼22.5 mV at 1 mA cm −2 for 3000 h). This work elucidates the relationship between lithiation reaction of oxides modified layer and derived SEI, guiding for constructing stable lithium metal batteries.

Ultra-thin interfacial domain wall less than 1 nm based on TbxCo100−x/Cu/[Co/Pt]2 heterostructures for multi-level magnetic pillar memory

We propose a new pillar type of multi-level memory with TbxCo100−x/Cu/[Co/Pt]2 heterostructures to achieve high storage density and controllable domain wall position in-memory applications. The structure consists of amorphous ferrimagnetic Tb–Co alloy films and ferromagnetic Co/Pt multilayers separated by less than one monolayer of Cu. Here, we observe that the interfacial domain wall energy density can be controlled by changing the interlayer thickness of Cu and Tb–Co composition. We also observe two competing mechanisms, one leading to an increase and the other to a decrease, corresponding to the effect of Tb content on saturation magnetization and coercivity of heterostructures. Theoretical and experimental results show that by tuning the Tb–Co composition, we were able to decrease domain wall (DW) width and precisely control the DW position of the multilayer structure. The interfacial domain wall width is significantly decreased to less than 1 nm compared to other reports. Moreover, controlling the DW position and width offers a novel multi-level magnetic memory with high performance compared to conventional memory applications.

Large Perpendicular Exchange Energy in TbxCo100−x/Cu(t)/[Co/Pt]2 Heterostructures

In order to realize a perpendicular exchange bias for applications, a robust and tunable exchange bias is required for spintronic applications. Here, we show the perpendicular exchange energy (PEE) in the TbxCo100−x/Cu/[Co/Pt]2 heterostructures. The structure consists of amorphous ferrimagnetic Tb–Co alloy films and ferromagnetic Co/Pt multilayers. The dependence of the PEE on the interlayer thickness of Cu and the composition of Tb–Co were analyzed. We demonstrate that the PEE can be controlled by changing the Cu interlayer thickness of 0.2 < tCu < 0.3 (nm). We found that PEE reaches a maximum value (σPw = 1 erg/cm2) at around x = 24%. We, therefore, realize the mechanism of PEE in the TbxCo100−x/Cu/[Co/Pt]2 heterostructures. We observe two competing mechanisms—one leading to an increase and the other to a decrease—which corresponds to the effect of Tb content on saturation magnetization and the coercivity of heterostructures. Sequentially, our findings show possibilities for both pinned layers in spintronics and memory device applications by producing large PEE and controlled PEE by Cu thickness, based on TbxCo100−x/Cu/[Co/Pt]2 heterostructures.

Failure and Recovery Modes of Submicron Cu(In,Ga)Se2 Solar Cells with High Cu Content.

As an emerging route to further lower the production cost, reducing the thickness of Cu(In,Ga)Se2 (CIGS) absorber has drawn substantial attention and has been intensively studied in recent years. However, thickness-induced change still limits the device performance of thin CIGS solar cells. Herein, by examining a series of submicron CIGS solar cells with varied Cu content through their photovoltaic (PV) performance, the optimal Cu content in these submicron CIGS devices is found to be lower than that of the normal thickness CIGS devices. Electrical and compositional characterizations reveal that reduced thickness makes absorber vulnerable to the shunt paths formed with high Cu content. By intentionally lowering the Cu content in submicron CIGS, shunt resistance (Rsh) of the devices is significantly improved and therefore a high fill factor (FF) is achieved. Moreover, RbF postdeposition treatment (PDT) can passivate the shunt paths in the high Cu content samples to a very good extent, manifesting by the significantly improved FF.

Ar/N2 Plasma Induced Metastable CuxNy for Cu-Cu Direct Bonding

Metal-metal bonding is a promising semiconductor bonding technique, which has been widely developed to establish vertically electrical connections, provide mechanical support, and form hermetical sealing. In this work, we report Ar/N2 plasma induced metastable CuxNy for Cu-Cu die-die bonding performed in ambient environment. Surface characterization is performed on the Cu surface both before and after plasma exposure, revealing that the plasma induced CuxNy surface remains in “activated” state for up to 6 hours compared to the regular Cu surface. Subsequently, the dies are bonded. The bonding quality is assessed for mechanical bonding strength, hermeticity, and electrical conduction. The results support successful bonding with the desired properties. This reported bonding technology can be applied for high-throughput 3D integration and CMOS-MEMS packaging. Introduction Microelectromechanical systems (MEMS) packaging requires both mechanical and electrical connections in addition to hermetical sealing, therefore 3D integration is a promising solution [1]. Metal diffusion (thermocompression) bonding, eutectic alloy bonding, and solid-liquid interdiffusion bonding are popular bonding methods [2]. The latter two bonding methods, which are based on solder materials, may be plagued by inter-metallic compound (IMC) reliability issue. On the other hand, metal diffusion bonding, such as Cu-Cu, is absent of IMC issue. However, Cu is prone to rapid oxidation. To overcome this issue, Cu surface treatments such as specialized chemical mechanical polishing (CMP), chemical treatment, surface assembled monolayer (SAM), and plasma activation, have been reported. Among these methods, plasma activation is favorable as the process does not leave behind any residue. In this work, we report on the time-dependent evolution of the Ar/N2 plasma induced CuxNy layer and its application for Cu-Cu die-die bonding performed in ambient environment. Cu-Cu Die-Die Bonding Si wafers were firstly patterned and deposited with 10 nm thickness of Ti as adhesion layer, followed with 100 nm thickness of Cu via electron-beam evaporation. Afterwards, the wafers were diced into small dies with dimensions of 5 mm × 7 mm. Thereafter, the Cu surface of the diced dies was exposed to Ar/N2 plasma. During the plasma process, Ar plasma was firstly applied to remove surface contaminants and copper oxides, N2 plasma was subsequently applied on the Cu surface to form an ultra-thin layer of CuxNy for passivating the Cu surface and achieving low temperature bonding. Finally, the “activated” dies were immediately pre-bonded in ambient environment in clean room (18 ºC and 40% humidity) and were annealed at 300 ºC for a duration of 30 min. Results and Observation The evolution of water contact angle (θ) with time variation for both the non-activated and Ar/N2 plasma activated Cu surface is shown in Figure 1. Compared to that of the non-activated Cu surface (~60º), the water contact angle of the Ar/N2 plasma activated Cu surface (~10º) is lower initially, signifying that the activated surface is more hydrophilic. Subsequently, the water contact angle of the Ar/N2 plasma activated Cu surface increases gradually until it is comparable to that of the non-activated Cu surface. The results show the metastability and degradation of CuxNy layer, revealing that the CuxNy layer remains in an “activated” state for up to 6 hours post plasma exposure. In addition, the mechanical bonding strength, hermeticity, and electrical conduction of the bonded dies are shown in Figures 2(a) and 2(b), 2(c), and 2(d), respectively. The results show that the dies are bonded successfully with the desired properties. Conclusion In this work, Ar/N2 plasma activated Cu-Cu die-die bonding in ambient environment was conducted. Surface analysis revealed that the plasma induced metastable CuxNy surface is more hydrophilic than the non-activated Cu surface and the plasma activated Cu surface remains in an “activated” state for a duration of 6 hours after plasma exposure. In addition, the mechanical bonding strength, hermeticity, and electric conduction of the bonded dies were determined, the results show that the dies were bonded together successfully. This bonding technology can be applied for high-throughput 3D integration and CMOS-MEMS packaging. Acknowledgement Authors acknowledge funding support from A*STAR (A18A4b0055) under the “Nanosystems at the Edge” program.

Flexible and Semi‐Transparent Ultra‐Thin CIGSe Solar Cells Prepared on Ultra‐Thin Glass Substrate: A Key to Flexible Bifacial Photovoltaic Applications

AbstractFor applications to semi‐transparent and/or bifacial solar cells in building‐integrated photovoltaics and building‐applied photovoltaics, studies are underway to reduce the processing cost and time by decreasing the thickness of Cu(In1−x,Gax)Se2 (CIGSe) absorber to the ultra‐thin scale (≤500 nm). To dynamically and affordably meet the growing demand for electric power, daylighting, and architectural aesthetics of buildings in urban area, flexible semi‐transparent ultra‐thin (F‐STUT) CIGSe solar cells are proposed on flexible ultra‐thin glass (UTG) and compared with rigid semi‐transparent ultra‐thin (STUT) CIGSe solar cells fabricated on soda‐lime glass (SLG). At all the tested deposition temperatures of CIGSe, the F‐STUT CIGSe solar cells exhibit superior performance compared to the rigid STUT CIGSe solar cells. Furthermore, through realistic measurement under ≈1.3‐sun illumination, maximum bifacial power conversion efficiency of 11.90% and 13.23% are obtained for SLG and UTG, respectively. The major advantages of using UTG instead of SLG are not only the intrinsic characteristics of UTG, such as flexibility and high transmittance, but also collateral benefits such as the larger CIGSe grain size at the deposition temperature, better CIGSe crystalline quality, more precise controllability of the alkali element, and reduced thickness of the interfacial GaOx layer, which enhance the photovoltaic parameters.

Carburization resistance of cu-coated stainless steel in supercritical carbon dioxide environments

This study investigates the effectiveness of Cu as a corrosion barrier in supercritical carbon dioxide (s−CO2) by coating 316 stainless steel (316) with various thicknesses of Cu. 316 exposed to s−CO2 with 50 ppm CO showed a reduction in oxidation corresponding to the thickness of its Cu barrier coating. Additionally, a continuous Cu layer between the environment and the alloy was found to correlate to an elimination of carburization and corrosion-related mechanical degradation. This Cu coating technique could be applied over a variety of temperatures to improve the corrosion resistance of alloys that are susceptible to carburization.

Fast formation of Cu-Sn intermetallic joints using pre-annealed Sn/Cu/Sn composite preform for high-temperature bonding applications

This paper presents the interfacial reaction and growth rate of Cu-Sn intermetallic compounds (IMCs) for various aging times in a composite preform for a die-attach material at high temperature. The feasibility of the composite preform we fabricated for power electronic applications to reduce the long bonding time of transient liquid phase (TLP) bonding was evaluated in this work. After the plating process, the composite preform was composed of Sn layers at both sides of the Cu core layer and the Cu layer. In terms of the aging treatment, the IMC layer was formed rapidly at the Cu-Sn interface in the composite preform by consuming the Sn layers, and the reduction and growth rates of Cu and Cu3Sn were calculated, respectively. We performed the TLP bonding process at 270 °C using various aged composite preforms. The Cu-Sn IMC was formed rapidly on both sides adjacent to the Cu core layer. The thickness of Cu decreased as the aging time elapsed. Therefore, the amount of Cu3Sn adjacent to the Cu core layer increased and the amount of Cu6Sn5 rapidly increased, simultaneously. We investigated the thicknesses and variations of the phase of the joint in the composite preform during the aging treatment process and sequential TLP bonding process for various times. We fabricated pre-annealed Sn/Cu/Sn preforms and performed fast Cu-Sn TLP bonding for high temperature power electronic applications.