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Hans-werner Schock - One of the best experts on this subject based on the ideXlab platform.

  • Surface Off-Stoichiometry of CuInS Thin-Film Solar Cell Absorbers
    IEEE Journal of Photovoltaics, 2013
    Co-Authors: Marcus Bär, Lothar Weinhardt, Roberto Félix, R. G. Wilks, N. Barreau, Clemens Heske, Joachim Klaer, Hans-werner Schock
    Abstract:

    In this paper, X-ray photoelectron and X-ray-excited Auger electron spectroscopy was used to investigate the chemical Surface structure of CuInS2 thin-film solar cell absorbers. We find that the [In]/[Cu] Surface composition can vary between 1.6 (± 0.4) and 3.7 (± 0.7), depending on relatively minor variations in the absorber formation process and/or whether additional wet-chemical treatments are performed. These variations are primarily due to differences in the Cu Surface concentration. The corresponding change of the modified In Auger parameter is interpreted as being indicative of a change in the chemical environment of In as a function of Cu off-stoichiometry.

  • Surface Off-Stoichiometry of CuInS$_{2}$ Thin-Film Solar Cell Absorbers
    IEEE Journal of Photovoltaics, 2013
    Co-Authors: Joachim Klaer, Lothar Weinhardt, Roberto Félix, R. G. Wilks, N. Barreau, Clemens Heske, Hans-werner Schock
    Abstract:

    In this paper, X-ray photoelectron and X-ray-excited Auger electron spectroscopy was used to investigate the chemical Surface structure of CuInS2 thin-film solar cell absorbers. We find that the [In]/[Cu] Surface composition can vary between 1.6 (± 0.4) and 3.7 (± 0.7), depending on relatively minor variations in the absorber formation process and/or whether additional wet-chemical treatments are performed. These variations are primarily due to differences in the Cu Surface concentration. The corresponding change of the modified In Auger parameter is interpreted as being indicative of a change in the chemical environment of In as a function of Cu off-stoichiometry.

  • Surface off-stoichiometry of CuInS2 thin-film solar cell absorbers
    2012 IEEE 38th Photovoltaic Specialists Conference (PVSC) PART 2, 2012
    Co-Authors: Joachim Klaer, Lothar Weinhardt, Roberto Félix, R. G. Wilks, N. Barreau, Clemens Heske, Hans-werner Schock
    Abstract:

    X-ray photoelectron and x-ray-excited Auger electron spectroscopy was used to investigate the chemical Surface structure of CuInS2 thin-film solar cell absorbers. We find that the [In]/[Cu] Surface composition can vary between 1.6 (± 0.4) and 3.7 (± 0.7), depending on relatively minor variations in the absorber formation process and/or whether additional wet-chemical treatments are performed. These variations are primarily due to differences in the Cu Surface concentration. The corresponding change of the modified In Auger parameter is interpreted as being indicative for a change of the chemical environment of In as a function of Cu off-stoichiometry.

Tahar Laoui - One of the best experts on this subject based on the ideXlab platform.

  • Few-Layers Graphene Film and Copper Surface Morphology for Improved Corrosion Protection of Copper
    Journal of Materials Engineering and Performance, 2019
    Co-Authors: Sultan Akhtar, A. Madhan Kumar, Junaid Ahmed, Tahar Laoui, Ahmed Ibrahim, Ihsan-ul-haq Toor
    Abstract:

    Graphene has shown excellent corrosion protection of copper (Cu). The corrosion protection of Cu is governed by the characteristics of the deposited graphene and Cu Surface morphology underneath. In this work, graphene films (1-2, 4-5 layers) were deposited on Cu using a chemical vapor deposition by changing hydrogen (H_2) concentration during the annealing stage. The chemical structure and Surface microstructural features of graphene/Cu were inspected by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The electrochemical corrosion performance of graphene/Cu was studied in 0.5 M sodium chloride solution using potentiodynamic polarization and electrochemical impedance spectroscopic measurements. The 1-2 layers of graphene and rough Cu Surface were obtained for low H_2 concentrations (0 and 2.5%), whereas high H_2 concentrations, 20 and 50%, resulted in a smooth Cu Surface and 4-5 layers of graphene. Our results showed that Cu with a smooth Surface and multilayer graphene film exhibited the best corrosion resistance against electrochemical degradation. Tafel analysis revealed that Cu with 4-5 layers of graphene coating corroded nearly three orders of magnitude slower than the annealed Cu, without graphene coating. The results of this study can be useful for several applications where Cu is in close contact with salt species.

  • Study of the impact of chemical etching on Cu Surface morphology, graphene growth and transfer on SiO2/Si substrate
    Carbon, 2017
    Co-Authors: Ahmed Ibrahim, Ghaith Nadhreen, Akhtar, Feras M. Kafiah, Tahar Laoui
    Abstract:

    Abstract Cleaning copper (Cu) prior graphene deposition, is a crucial step for removing most Surface impurities and hence ensuring production of monolayer, large area graphene film with good quality. In this study, we investigated the effect of Cu-cleaning using three different etchants (ammonium persulfate (APS), ferric chloride (FeCl3) and nitric acid (HNO3)) for short and long times (30s and 5min) on Cu Surface morphology, graphene growth and subsequent transfer onto SiO2/Si substrate. Our results revealed that 30s-etching gave smoother Cu Surface compared to 5min and hence it promoted formation of more uniform graphene film. Furthermore, among the three chemical etchants, APS-30s-etched Cu exhibited the most continuous, uniform, predominantly monolayer graphene film with low density of bi/few-layered domains. This was associated with relatively smoother Cu Surface containing significantly lower density of Surface particles as compared to other etchants (FeCl3 and HNO3). Consequently, 30s-graphene samples yielded better transfer results compared to 5min samples, which exhibited more wrinkles, tears and cracks upon being transferred onto SiO2/Si substrate. This study highlights the importance of cleaning etchant selection for controlling not only Cu Surface morphology but also the characteristics of grown graphene film and its subsequent transfer onto other substrates.

  • Effects of annealing on copper substrate Surface morphology and graphene growth by chemical vapor deposition
    Carbon, 2015
    Co-Authors: Ahmed Ibrahim, Muataz Atieh, Sultan Akhtar, Rohit Karnik, Tahar Laoui
    Abstract:

    Understanding the mechanism of graphene synthesis by chemical vapor deposition and the effect of process parameters is critical for production of high-quality graphene. In the present work, we investigated the effect of H2 concentration during annealing on evolution of Cu Surface morphology, and on deposited graphene characteristics. Our results revealed that H2 had a smoothening effect on Cu Surface as its Surface roughness was reduced significantly at high H2 concentration along with the formation of Surface facets, dents and nanometer-sized particles. Furthermore, H2 content influenced the graphene morphology and its quality. A low H2 concentration (0% and 2.5%) during annealing promoted uniform and good quality bilayer graphene. In contrast, a high concentration of H2 (20% and 50%) resulted in multilayer, non-uniform and defective graphene. Interestingly, the annealed Cu Surface morphology differed considerably from that obtained after deposition of graphene, indicating that graphene deposition has its own impact on Cu Surface.

  • Evolution of Cu Surface Morphology and its Effect on Graphene Synthesized by Chemical Vapor Deposition
    Advances in Science and Technology, 2014
    Co-Authors: Ahmed Ibrahim, Muataz Atieh, Rohit Karnik, A. Owais, Tahar Laoui
    Abstract:

    Chemical Vapor Deposition (CVD) is generally utilized for producing large area, good quality graphene films on suitable substrates. Copper (Cu) substrate is used mainly as a substrate and catalyst during graphene synthesis process by CVD method. The purpose of the present work is to investigate the evolution of Cu Surface morphology after graphene growth and its influence on grown graphene quality. In this study, graphene was grown using methane as the carbon source at temperature 1040 °C for 5 minutes. Scanning electron microscopy (SEM), Optical Microscopy (OM) and atomic force microscopy (AFM) were utilized to analyze the change of Cu Surface morphology after graphene synthesis. Raman spectroscopy was used to characterize the characteristics of grown graphene. SEM and AFM results showed that copper substrate Surface morphology was modified after graphene growth associated by formation of large size Cu particles located basically on the Surface terraces, resulting in deposition of multilayer, very small graphene domains aligned linearly along rolling marks direction.

Haesung Park - One of the best experts on this subject based on the ideXlab platform.

  • Two-Step Plasma Treatment on Copper Surface for Low-Temperature Cu Thermo-Compression Bonding
    IEEE Transactions on Components Packaging and Manufacturing Technology, 2020
    Co-Authors: Haesung Park
    Abstract:

    The success of wafer-to-wafer or chip-to-chip bonding in 3-D packaging relies on the development of planarized, activated, and oxygen-free Cu Surface. Preventing Cu oxidation is becoming a crucial issue in chip-to-chip bonding processes. In this study, a two-step plasma pretreatment process was demonstrated to prevent copper oxidation by virtue of forming a nitride passivation layer on the Cu Surface. The two-step plasma pretreatment consisted of Ar plasma to activate the Cu Surface, followed by N2 plasma to passivate the Cu Surface. It was found that the pressure in the Ar plasma step had the greatest effect on the formation of nitrate passivation on the Cu Surface, and the lower the pressure in the Ar plasma step, the better the formation of copper nitrate in the N2 plasma step. The two-step plasma pretreatment provided a nitride-passivated Cu Surface and significantly improved the Cu-to-Cu bonding quality. This process may enable Cu-to-Cu bonding in an atmospheric environment.

  • Nitrogen passivation formation on Cu Surface by Ar–N_2 plasma for Cu-to-Cu wafer stacking application
    Microsystem Technologies, 2019
    Co-Authors: Haesung Park, Sarah Eunkyung Kim
    Abstract:

    Wafer stacking technology provides reduced interconnect delay, improved bandwidth, reduced form factor, and decreased cost. Solder-based metallic die bonding is presently utilized in high-volume manufacturing, but Cu-based metallic wafer bonding is quickly becoming a key bonding technique for next generation 3D IC and heterogeneous stacking applications. In this study, Ar–N_2 plasma treatment on Cu Surface was investigated to passivate Cu Surface with nitrogen and to enhance the bonding quality of Cu-to-Cu wafer bonding. The Ar–N_2 plasma treatment was performed by conventional DC sputtering under 5 mTorr working pressure with different Ar–N_2 partial pressures. Then, the effect of Ar–N_2 plasma treatment on Cu Surface was evaluated structurally and electrically. It was observed that the Ar–N_2 plasma treatment with high nitrogen partial pressure over a sufficient plasma treatment time provided activated Cu Surface, reduction of copper oxide and chemisorbed nitrogen, and copper nitride passivation. The Ar–N_2 plasma treatment of Cu Surface was found to be a potential pretreatment method for Cu-to-Cu bonding.

  • 3DIC - Characterization of Nitride Passivated Cu Surface for Low-Temperature Cu-Cu Bonding
    2019 International 3D Systems Integration Conference (3DIC), 2019
    Co-Authors: Haesung Park
    Abstract:

    Copper nitride passivated Surface has been characterized and optimized by the design of experiment (DOE) technique with the aim of low-temperature (300°C) Cu-Cu bonding. In order to generate an oxidation-free Surface prior to Cu-Cu bonding process, N 2 plasma treatment was performed on Cu Surface followed by Cu Surface activation and cleaning by Ar plasma in the same conventional DC sputter chamber. In this study, N 2 plasma treatment conditions were optimized using the response Surface methodology (RSM) based on central composite design (CCD) in DOE. The chemical states of nitride passivated Cu Surface were analyzed by XPS profiles and then, several meaningful peak areas of each element were calCulated by a deconvolution technique. These peak areas and Surface roughness by AFM were used as the input values for the response optimization process. Cu-Cu bonded interface quality using optimized plasma conditions at low-temperature (300°C) has been significantly improved and it shows this research has great potential for Cu-Cu bonding in mass production.

  • 3DIC - Effects of Argon and Nitrogen ion Bombardments on Sputtered and Electroplated Cu Surfaces for Cu Bonding Application
    2019 International 3D Systems Integration Conference (3DIC), 2019
    Co-Authors: Haesung Park
    Abstract:

    This study depicts the comparative research between sputtered and electroplated Cu Surfaces using argon and nitrogen ion bombardments to form copper nitride passivation layers. The thin copper nitride layer is formed in order to prohibit Cu oxidation on copper Surface and to lower bonding temperature in Cu-Cu thermo-compression bonding process. Argon ion bombardment was applied to activate and clean copper Surface. Nitrogen ion bombardment was utilized to passivate the Cu Surface after argon ion bombardment. The sputtered Cu Surface tended to form Cu 4 N layer, while the electroplated Cu Surface tended to form Cu 3 N layer. In comparison with electroplated Cu, the sputtered Cu had a lower roughness and a slightly higher sheet resistance. The bonding quality of the sputtered Cu samples was better than that of the electroplated samples. Further research should improve the roughness and copper nitride properties of the Cu Surface.

  • Effect of Nitride Passivation on Cu Surface for Low Temperature Cu-to-Cu Bonding
    2019 6th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D), 2019
    Co-Authors: Haesung Park
    Abstract:

    For low temperature Cu-to-Cu bonding process, copper nitride passivation on Cu Surface was studied via two-step plasma treatments using argon and nitrogen gases. The two-step plasma treatment of copper nitride passivation was processed in a DC sputtering vaCuum chamber. Cu Surface was activated with Ar ion bombardment in Ar plasma and immediately followed by N2 plasma treatment for Surface passivation. In this study, various parameters of Ar plasma such as RF power, working pressure and treatment time were controlled to find an optimal Cu Surface where nitride passivation was formed. The degree of nitridation and oxidation after the plasma treatments was characterized quantitatively using XPS analysis. Lastly Cu-to-Cu bonding was performed at 300°C and the effect of copper nitride passivation on Cu bonding quality was evaluated by SAT and SEM analysis.

Joachim Klaer - One of the best experts on this subject based on the ideXlab platform.

  • Surface Off-Stoichiometry of CuInS Thin-Film Solar Cell Absorbers
    IEEE Journal of Photovoltaics, 2013
    Co-Authors: Marcus Bär, Lothar Weinhardt, Roberto Félix, R. G. Wilks, N. Barreau, Clemens Heske, Joachim Klaer, Hans-werner Schock
    Abstract:

    In this paper, X-ray photoelectron and X-ray-excited Auger electron spectroscopy was used to investigate the chemical Surface structure of CuInS2 thin-film solar cell absorbers. We find that the [In]/[Cu] Surface composition can vary between 1.6 (± 0.4) and 3.7 (± 0.7), depending on relatively minor variations in the absorber formation process and/or whether additional wet-chemical treatments are performed. These variations are primarily due to differences in the Cu Surface concentration. The corresponding change of the modified In Auger parameter is interpreted as being indicative of a change in the chemical environment of In as a function of Cu off-stoichiometry.

  • Surface Off-Stoichiometry of CuInS$_{2}$ Thin-Film Solar Cell Absorbers
    IEEE Journal of Photovoltaics, 2013
    Co-Authors: Joachim Klaer, Lothar Weinhardt, Roberto Félix, R. G. Wilks, N. Barreau, Clemens Heske, Hans-werner Schock
    Abstract:

    In this paper, X-ray photoelectron and X-ray-excited Auger electron spectroscopy was used to investigate the chemical Surface structure of CuInS2 thin-film solar cell absorbers. We find that the [In]/[Cu] Surface composition can vary between 1.6 (± 0.4) and 3.7 (± 0.7), depending on relatively minor variations in the absorber formation process and/or whether additional wet-chemical treatments are performed. These variations are primarily due to differences in the Cu Surface concentration. The corresponding change of the modified In Auger parameter is interpreted as being indicative of a change in the chemical environment of In as a function of Cu off-stoichiometry.

  • Surface off-stoichiometry of CuInS2 thin-film solar cell absorbers
    2012 IEEE 38th Photovoltaic Specialists Conference (PVSC) PART 2, 2012
    Co-Authors: Joachim Klaer, Lothar Weinhardt, Roberto Félix, R. G. Wilks, N. Barreau, Clemens Heske, Hans-werner Schock
    Abstract:

    X-ray photoelectron and x-ray-excited Auger electron spectroscopy was used to investigate the chemical Surface structure of CuInS2 thin-film solar cell absorbers. We find that the [In]/[Cu] Surface composition can vary between 1.6 (± 0.4) and 3.7 (± 0.7), depending on relatively minor variations in the absorber formation process and/or whether additional wet-chemical treatments are performed. These variations are primarily due to differences in the Cu Surface concentration. The corresponding change of the modified In Auger parameter is interpreted as being indicative for a change of the chemical environment of In as a function of Cu off-stoichiometry.

Ahmed Ibrahim - One of the best experts on this subject based on the ideXlab platform.

  • Few-Layers Graphene Film and Copper Surface Morphology for Improved Corrosion Protection of Copper
    Journal of Materials Engineering and Performance, 2019
    Co-Authors: Sultan Akhtar, A. Madhan Kumar, Junaid Ahmed, Tahar Laoui, Ahmed Ibrahim, Ihsan-ul-haq Toor
    Abstract:

    Graphene has shown excellent corrosion protection of copper (Cu). The corrosion protection of Cu is governed by the characteristics of the deposited graphene and Cu Surface morphology underneath. In this work, graphene films (1-2, 4-5 layers) were deposited on Cu using a chemical vapor deposition by changing hydrogen (H_2) concentration during the annealing stage. The chemical structure and Surface microstructural features of graphene/Cu were inspected by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The electrochemical corrosion performance of graphene/Cu was studied in 0.5 M sodium chloride solution using potentiodynamic polarization and electrochemical impedance spectroscopic measurements. The 1-2 layers of graphene and rough Cu Surface were obtained for low H_2 concentrations (0 and 2.5%), whereas high H_2 concentrations, 20 and 50%, resulted in a smooth Cu Surface and 4-5 layers of graphene. Our results showed that Cu with a smooth Surface and multilayer graphene film exhibited the best corrosion resistance against electrochemical degradation. Tafel analysis revealed that Cu with 4-5 layers of graphene coating corroded nearly three orders of magnitude slower than the annealed Cu, without graphene coating. The results of this study can be useful for several applications where Cu is in close contact with salt species.

  • Study of the impact of chemical etching on Cu Surface morphology, graphene growth and transfer on SiO2/Si substrate
    Carbon, 2017
    Co-Authors: Ahmed Ibrahim, Ghaith Nadhreen, Akhtar, Feras M. Kafiah, Tahar Laoui
    Abstract:

    Abstract Cleaning copper (Cu) prior graphene deposition, is a crucial step for removing most Surface impurities and hence ensuring production of monolayer, large area graphene film with good quality. In this study, we investigated the effect of Cu-cleaning using three different etchants (ammonium persulfate (APS), ferric chloride (FeCl3) and nitric acid (HNO3)) for short and long times (30s and 5min) on Cu Surface morphology, graphene growth and subsequent transfer onto SiO2/Si substrate. Our results revealed that 30s-etching gave smoother Cu Surface compared to 5min and hence it promoted formation of more uniform graphene film. Furthermore, among the three chemical etchants, APS-30s-etched Cu exhibited the most continuous, uniform, predominantly monolayer graphene film with low density of bi/few-layered domains. This was associated with relatively smoother Cu Surface containing significantly lower density of Surface particles as compared to other etchants (FeCl3 and HNO3). Consequently, 30s-graphene samples yielded better transfer results compared to 5min samples, which exhibited more wrinkles, tears and cracks upon being transferred onto SiO2/Si substrate. This study highlights the importance of cleaning etchant selection for controlling not only Cu Surface morphology but also the characteristics of grown graphene film and its subsequent transfer onto other substrates.

  • Effects of annealing on copper substrate Surface morphology and graphene growth by chemical vapor deposition
    Carbon, 2015
    Co-Authors: Ahmed Ibrahim, Muataz Atieh, Sultan Akhtar, Rohit Karnik, Tahar Laoui
    Abstract:

    Understanding the mechanism of graphene synthesis by chemical vapor deposition and the effect of process parameters is critical for production of high-quality graphene. In the present work, we investigated the effect of H2 concentration during annealing on evolution of Cu Surface morphology, and on deposited graphene characteristics. Our results revealed that H2 had a smoothening effect on Cu Surface as its Surface roughness was reduced significantly at high H2 concentration along with the formation of Surface facets, dents and nanometer-sized particles. Furthermore, H2 content influenced the graphene morphology and its quality. A low H2 concentration (0% and 2.5%) during annealing promoted uniform and good quality bilayer graphene. In contrast, a high concentration of H2 (20% and 50%) resulted in multilayer, non-uniform and defective graphene. Interestingly, the annealed Cu Surface morphology differed considerably from that obtained after deposition of graphene, indicating that graphene deposition has its own impact on Cu Surface.

  • Evolution of Cu Surface Morphology and its Effect on Graphene Synthesized by Chemical Vapor Deposition
    Advances in Science and Technology, 2014
    Co-Authors: Ahmed Ibrahim, Muataz Atieh, Rohit Karnik, A. Owais, Tahar Laoui
    Abstract:

    Chemical Vapor Deposition (CVD) is generally utilized for producing large area, good quality graphene films on suitable substrates. Copper (Cu) substrate is used mainly as a substrate and catalyst during graphene synthesis process by CVD method. The purpose of the present work is to investigate the evolution of Cu Surface morphology after graphene growth and its influence on grown graphene quality. In this study, graphene was grown using methane as the carbon source at temperature 1040 °C for 5 minutes. Scanning electron microscopy (SEM), Optical Microscopy (OM) and atomic force microscopy (AFM) were utilized to analyze the change of Cu Surface morphology after graphene synthesis. Raman spectroscopy was used to characterize the characteristics of grown graphene. SEM and AFM results showed that copper substrate Surface morphology was modified after graphene growth associated by formation of large size Cu particles located basically on the Surface terraces, resulting in deposition of multilayer, very small graphene domains aligned linearly along rolling marks direction.