Hsiao-Hsuan Wan, Jian-Sian Li, Chao-Ching Chiang, Xinyi Xia, David C. Hays, Fan Ren, Stephen J. Pearton
Two of the most common dielectrics for β-Ga2O3 are SiO2 and Al2O3 because of their large bandgaps, versatility of preparation, and thermal stability. However, because of the anisotropic properties of the β-polytype, it is necessary to understand differences in band alignment for the different crystal orientation. Using x-ray photoelectron spectroscopy, we performed a comparative study of the band alignment of SiO2/β-Ga2O3 and Al2O3/ β-Ga2O3 heterojunctions with different β-Ga2O3 orientations of (001), (010), and (2¯01). The bandgaps were determined to be 4.64, 4.71, and 4.59 eV for the (2¯01), (001), and (010) oriented β-Ga2O3 substrates, respectively. The valence band offsets for SiO2 on these three orientations were 1.4, 1.4, and 1.1 eV, respectively, while for Al2O3, the corresponding values were 0.0, 0.1, and 0.2 eV, respectively. The corresponding conduction band offsets ranged from 2.59 to 3.01 eV for SiO2 and 2.26 to 2.51 eV for Al2O3.
{"title":"β-Ga2O3 orientation dependence of band offsets with SiO2 and Al2O3","authors":"Hsiao-Hsuan Wan, Jian-Sian Li, Chao-Ching Chiang, Xinyi Xia, David C. Hays, Fan Ren, Stephen J. Pearton","doi":"10.1116/6.0003039","DOIUrl":"https://doi.org/10.1116/6.0003039","url":null,"abstract":"Two of the most common dielectrics for β-Ga2O3 are SiO2 and Al2O3 because of their large bandgaps, versatility of preparation, and thermal stability. However, because of the anisotropic properties of the β-polytype, it is necessary to understand differences in band alignment for the different crystal orientation. Using x-ray photoelectron spectroscopy, we performed a comparative study of the band alignment of SiO2/β-Ga2O3 and Al2O3/ β-Ga2O3 heterojunctions with different β-Ga2O3 orientations of (001), (010), and (2¯01). The bandgaps were determined to be 4.64, 4.71, and 4.59 eV for the (2¯01), (001), and (010) oriented β-Ga2O3 substrates, respectively. The valence band offsets for SiO2 on these three orientations were 1.4, 1.4, and 1.1 eV, respectively, while for Al2O3, the corresponding values were 0.0, 0.1, and 0.2 eV, respectively. The corresponding conduction band offsets ranged from 2.59 to 3.01 eV for SiO2 and 2.26 to 2.51 eV for Al2O3.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136060311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lijuan Li, Hongrui Yao, Wenya Bi, Wanlu Fu, Na Wang
Since uniform dispersion and robust interfacial compatibility of nanofiller with epoxy resin are the most critical parameters to improve the corrosion protection property, a new effective anticorrosion nanofiller [polydopamine (PDA)@g-C3N4-CeO2] is designed by stacking PDA modified g-C3N4 and nano-CeO2 with the help of a silane coupling agent. The structure and morphology of PDA@g-C3N4-CeO2 are characterized by FTIR, XRD, XPS, SEM, and TEM. Furthermore, the PDA@g-C3N4-CeO2 nanofiller is loaded within waterborne epoxy coating (WEC) and the corrosion resistance of the prepared nanocomposite coating is studied. It can be inferred from the dispersion test that g-C3N4 modified by PDA and nano-CeO2 exhibits excellent dispersion and compatibility in de-ionized water. The Electrochemical impedance spectroscope (EIS) results indicate that nanocomposite coating with PDA@g-C3N4-CeO2 exhibits the best corrosion resistance, and its low-frequency impedance (Zf=0.01Hz) is 1.78 × 109 Ω cm2, which is two orders of magnitude higher than that of pure WEC (4.27 × 107 Ω cm2). In the salt spray test, PDA@g-C3N4-CeO2/WEC also showed excellent long-term corrosion resistance with few corrosion products even after 600 h, which was consistent with the results of the EIS test. In addition, PDA@g-C3N4-CeO2/WEC also reflects the most fantastic adhesion strength (14.22 MPa), which is improved by 45.40% than that of pure WEC (9.78 MPa). Generally, the excellent protection properties of PDA@g-C3N4-CeO2/WEC are attributed to the presence of PDA and KH-550 modified nano-CeO2 on the surface of g-C3N4, which increase the compatibility and surface interactions between nanofillers and epoxy resin.
{"title":"Anticorrosive coatings made from polydopamine modified graphitic C3N4 composites with synergistic anticorrosion effects","authors":"Lijuan Li, Hongrui Yao, Wenya Bi, Wanlu Fu, Na Wang","doi":"10.1116/6.0002769","DOIUrl":"https://doi.org/10.1116/6.0002769","url":null,"abstract":"Since uniform dispersion and robust interfacial compatibility of nanofiller with epoxy resin are the most critical parameters to improve the corrosion protection property, a new effective anticorrosion nanofiller [polydopamine (PDA)@g-C3N4-CeO2] is designed by stacking PDA modified g-C3N4 and nano-CeO2 with the help of a silane coupling agent. The structure and morphology of PDA@g-C3N4-CeO2 are characterized by FTIR, XRD, XPS, SEM, and TEM. Furthermore, the PDA@g-C3N4-CeO2 nanofiller is loaded within waterborne epoxy coating (WEC) and the corrosion resistance of the prepared nanocomposite coating is studied. It can be inferred from the dispersion test that g-C3N4 modified by PDA and nano-CeO2 exhibits excellent dispersion and compatibility in de-ionized water. The Electrochemical impedance spectroscope (EIS) results indicate that nanocomposite coating with PDA@g-C3N4-CeO2 exhibits the best corrosion resistance, and its low-frequency impedance (Zf=0.01Hz) is 1.78 × 109 Ω cm2, which is two orders of magnitude higher than that of pure WEC (4.27 × 107 Ω cm2). In the salt spray test, PDA@g-C3N4-CeO2/WEC also showed excellent long-term corrosion resistance with few corrosion products even after 600 h, which was consistent with the results of the EIS test. In addition, PDA@g-C3N4-CeO2/WEC also reflects the most fantastic adhesion strength (14.22 MPa), which is improved by 45.40% than that of pure WEC (9.78 MPa). Generally, the excellent protection properties of PDA@g-C3N4-CeO2/WEC are attributed to the presence of PDA and KH-550 modified nano-CeO2 on the surface of g-C3N4, which increase the compatibility and surface interactions between nanofillers and epoxy resin.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136060972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jennifer Stefani Weber, Vanessa Piroli, Michael Cristian Goldbeck, Bruna Louise Perotti, Carla Daniela Boeira, Newton Kiyoshi Fukumasu, Alexandre Fassini Michels, Carlos Alejandro Figueroa
Diamondlike carbon (DLC) coatings provide interesting properties for industrial applications. However, the low adhesion of DLC coatings on any type of ferrous alloy compromises technological applications. One possible solution to this issue is the application of adhesion interlayers. The aim of this study is to investigate the adhesion of DLC films on low-alloy steel through the use of silicon-containing interlayers at different deposition times using tetramethylsilane. The role of time on the physical-chemical, microstructural, and tribological properties of the material system was evaluated. The interlayer thickness linearly increased and greater contributions of silicon bonds were measured as a function of the interlayer deposition time. Nevertheless, longer deposition times increased the roughness and defect ratio in DLC coatings. Although good enough adhesion for decorative applications was acquired, no drastic variation in the average critical load (∼4.2 N) for delamination was observed at different deposition times for the samples that achieved adhesion.
{"title":"Si-containing interlayer using tetramethylsilene for diamondlike carbon film adhesion on low-alloy steel: The role of the interlayer deposition time","authors":"Jennifer Stefani Weber, Vanessa Piroli, Michael Cristian Goldbeck, Bruna Louise Perotti, Carla Daniela Boeira, Newton Kiyoshi Fukumasu, Alexandre Fassini Michels, Carlos Alejandro Figueroa","doi":"10.1116/6.0002911","DOIUrl":"https://doi.org/10.1116/6.0002911","url":null,"abstract":"Diamondlike carbon (DLC) coatings provide interesting properties for industrial applications. However, the low adhesion of DLC coatings on any type of ferrous alloy compromises technological applications. One possible solution to this issue is the application of adhesion interlayers. The aim of this study is to investigate the adhesion of DLC films on low-alloy steel through the use of silicon-containing interlayers at different deposition times using tetramethylsilane. The role of time on the physical-chemical, microstructural, and tribological properties of the material system was evaluated. The interlayer thickness linearly increased and greater contributions of silicon bonds were measured as a function of the interlayer deposition time. Nevertheless, longer deposition times increased the roughness and defect ratio in DLC coatings. Although good enough adhesion for decorative applications was acquired, no drastic variation in the average critical load (∼4.2 N) for delamination was observed at different deposition times for the samples that achieved adhesion.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136060969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We developed an area-selective deposition process for forming protective layers on top of masks generated using a microwave electron-cyclotron-resonance etching system. A deposition layer is formed only on SiO2 masks without forming an unnecessary deposition layer on the Si surfaces in the etching area, such as the bottoms of the patterns and isolated etching area. The protection layers were selectively formed on a SiO2 mask without forming on a Si etching area by using a SiCl4/H2/Cl2 plasma. The pretreatment to clean the Si and SiO2 surfaces before deposition was important for achieving selective deposition because selectivity appeared by nucleation delay on the cleaned Si surface. On the Si surface, adsorbed SiClx easily desorbed again by reacting with the Cl generated from the plasma. However, adsorbed SiClx on SiO2 was more difficult to desorb by reacting with Cl due to Si–O having a larger binding energy than Si–Si. After the deposition layer was selectively formed on the SiO2 mask, the layer was oxidized by using O2 plasma treatment to improve the etching resistance during the subsequent Si etching. We also investigated a Si etching process using selective deposition during the etching of a 25 nm-pitch line-and-space Si pattern with a SiO2 mask. Extremely highly selective etching was achieved using selective deposition without forming an unnecessary deposition on an isolated Si area.
{"title":"Selective mask deposition using SiCl4 plasma for highly selective etching process","authors":"Miyako Matsui, Makoto Miura, Kenichi Kuwahara","doi":"10.1116/6.0002773","DOIUrl":"https://doi.org/10.1116/6.0002773","url":null,"abstract":"We developed an area-selective deposition process for forming protective layers on top of masks generated using a microwave electron-cyclotron-resonance etching system. A deposition layer is formed only on SiO2 masks without forming an unnecessary deposition layer on the Si surfaces in the etching area, such as the bottoms of the patterns and isolated etching area. The protection layers were selectively formed on a SiO2 mask without forming on a Si etching area by using a SiCl4/H2/Cl2 plasma. The pretreatment to clean the Si and SiO2 surfaces before deposition was important for achieving selective deposition because selectivity appeared by nucleation delay on the cleaned Si surface. On the Si surface, adsorbed SiClx easily desorbed again by reacting with the Cl generated from the plasma. However, adsorbed SiClx on SiO2 was more difficult to desorb by reacting with Cl due to Si–O having a larger binding energy than Si–Si. After the deposition layer was selectively formed on the SiO2 mask, the layer was oxidized by using O2 plasma treatment to improve the etching resistance during the subsequent Si etching. We also investigated a Si etching process using selective deposition during the etching of a 25 nm-pitch line-and-space Si pattern with a SiO2 mask. Extremely highly selective etching was achieved using selective deposition without forming an unnecessary deposition on an isolated Si area.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136153201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wil Gardner, David A. Winkler, David L. J. Alexander, Davide Ballabio, Benjamin W. Muir, Paul J. Pigram
The self-organizing map (SOM) is a nonlinear machine learning algorithm that is particularly well suited for visualizing and analyzing high-dimensional, hyperspectral time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging data. Previously, we compared the capabilities of the SOM with more traditional linear techniques using ToF-SIMS imaging data. Although SOMs perform well with minimal data preprocessing and negligible hyperparameter optimization, it is important to understand how different data preprocessing methods and hyperparameter settings influence the performance of SOMs. While these investigations have been reported outside of the ToF-SIMS field, no such study has been reported for hyperspectral MSI data. To address this, we used two labeled ToF-SIMS imaging datasets, one of which was a polymer microarray dataset, while the other was semisynthetic hyperspectral data. The latter was generated using a novel algorithm that we describe here. A grid-search was used to evaluate which data preprocessing methods and SOM hyperparameters had the largest impact on the performance of the SOM. This was assessed using multiple linear regression, whereby performance metrics were regressed onto each variable defining the preprocessing-hyperparameter space. We found that preprocessing was generally more important than hyperparameter selection. We also found statistically significant interactions between several parameters studied, suggesting a complex interplay between preprocessing and hyperparameter selection. Importantly, we identified interesting trends, both dataset specific and dataset agnostic, which we describe and discuss in detail.
{"title":"Effect of data preprocessing and machine learning hyperparameters on mass spectrometry imaging models","authors":"Wil Gardner, David A. Winkler, David L. J. Alexander, Davide Ballabio, Benjamin W. Muir, Paul J. Pigram","doi":"10.1116/6.0002788","DOIUrl":"https://doi.org/10.1116/6.0002788","url":null,"abstract":"The self-organizing map (SOM) is a nonlinear machine learning algorithm that is particularly well suited for visualizing and analyzing high-dimensional, hyperspectral time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging data. Previously, we compared the capabilities of the SOM with more traditional linear techniques using ToF-SIMS imaging data. Although SOMs perform well with minimal data preprocessing and negligible hyperparameter optimization, it is important to understand how different data preprocessing methods and hyperparameter settings influence the performance of SOMs. While these investigations have been reported outside of the ToF-SIMS field, no such study has been reported for hyperspectral MSI data. To address this, we used two labeled ToF-SIMS imaging datasets, one of which was a polymer microarray dataset, while the other was semisynthetic hyperspectral data. The latter was generated using a novel algorithm that we describe here. A grid-search was used to evaluate which data preprocessing methods and SOM hyperparameters had the largest impact on the performance of the SOM. This was assessed using multiple linear regression, whereby performance metrics were regressed onto each variable defining the preprocessing-hyperparameter space. We found that preprocessing was generally more important than hyperparameter selection. We also found statistically significant interactions between several parameters studied, suggesting a complex interplay between preprocessing and hyperparameter selection. Importantly, we identified interesting trends, both dataset specific and dataset agnostic, which we describe and discuss in detail.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136312977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Using plasma solid-state surface metallurgy is a new method for preparing high-entropy alloy (HEA) coatings. In this paper, based on the experience in plasma solid-state surface metallurgy and the HEA, the TiCoCrNiWMo HEA coatings with metallurgical bonding and gradient structure were prepared by five-element co-infiltration of Co–Cr–Ni–W–Mo on the surface of a TC4 substrate for the first time. The tissue morphology evolution and properties of HEA coatings at different holding temperatures were investigated. The results show that the HEA coating at the holding temperature of 1000 °C consists of a deposited layer + diffusion layer. When the temperature exceeds the (α + β)/β transition temperature of TC4, only the deposited layer is formed on the surface of the substrate. Holding temperature does not affect the phase composition of the HEA coating. The best bonding performance of the HEA coating with the substrate was achieved at a holding temperature of 1000 °C, with a bonding force of about 63.81 N. All the HEA coatings showed different degrees of improvement in hardness, wear resistance, and corrosion resistance compared to the substrate. The HEA coatings prepared at 1000 °C had the best performance, with hardness and wear resistance 1.5 and 8.9 times higher than those of the substrate, respectively, and excellent corrosion resistance in acidic, alkaline, and salt solutions. The results show that the new TiCoCrNiWMo HEA coatings prepared by plasma solid-state surface metallurgy have good wear resistance and corrosion resistance and have good application prospects in the fields of automobile manufacturing and shipbuilding.
{"title":"Tissue evolution and properties of plasma solid-state surface metallurgical TiCoCrNiWMo high-entropy alloy coatings","authors":"Xin Li, Zixiang Zhou, Chenglei Wang, Haiqing Qin, Jijie Yang, Weijie Liu, Mulin Liang, Chong Liu, Hong Tan, Zhenjun Zhang","doi":"10.1116/6.0002872","DOIUrl":"https://doi.org/10.1116/6.0002872","url":null,"abstract":"Using plasma solid-state surface metallurgy is a new method for preparing high-entropy alloy (HEA) coatings. In this paper, based on the experience in plasma solid-state surface metallurgy and the HEA, the TiCoCrNiWMo HEA coatings with metallurgical bonding and gradient structure were prepared by five-element co-infiltration of Co–Cr–Ni–W–Mo on the surface of a TC4 substrate for the first time. The tissue morphology evolution and properties of HEA coatings at different holding temperatures were investigated. The results show that the HEA coating at the holding temperature of 1000 °C consists of a deposited layer + diffusion layer. When the temperature exceeds the (α + β)/β transition temperature of TC4, only the deposited layer is formed on the surface of the substrate. Holding temperature does not affect the phase composition of the HEA coating. The best bonding performance of the HEA coating with the substrate was achieved at a holding temperature of 1000 °C, with a bonding force of about 63.81 N. All the HEA coatings showed different degrees of improvement in hardness, wear resistance, and corrosion resistance compared to the substrate. The HEA coatings prepared at 1000 °C had the best performance, with hardness and wear resistance 1.5 and 8.9 times higher than those of the substrate, respectively, and excellent corrosion resistance in acidic, alkaline, and salt solutions. The results show that the new TiCoCrNiWMo HEA coatings prepared by plasma solid-state surface metallurgy have good wear resistance and corrosion resistance and have good application prospects in the fields of automobile manufacturing and shipbuilding.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135014344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, stable and long-term field emission properties that completely follow the Child–Langmuir law were successfully observed. A tungsten tip covered with a liquid gallium metal was used. The current characteristics showed three phases. The electron emission first began below half of the threshold voltage for the emission from a bare W chip, and the current increased by 20 μA. Then, the field emission pattern showed multiple disordered blinking spots, which originated Ga Taylor cones and the emission current value reached several mAs. Then, emission current began to follow the Child–Langmuir law, and a clear field emission pattern from {011}-oriented tungsten was observed. Electrons emitted from the submicrometer sized area that is heated by itself with joule heating of current densities greater than 107 A/cm2.
{"title":"Self-joule heating assisted field emission following the Child–Langmuir law","authors":"Yoichiro Neo, Rikuto Oda, Jonghyun Moon","doi":"10.1116/5.0159964","DOIUrl":"https://doi.org/10.1116/5.0159964","url":null,"abstract":"In this study, stable and long-term field emission properties that completely follow the Child–Langmuir law were successfully observed. A tungsten tip covered with a liquid gallium metal was used. The current characteristics showed three phases. The electron emission first began below half of the threshold voltage for the emission from a bare W chip, and the current increased by 20 μA. Then, the field emission pattern showed multiple disordered blinking spots, which originated Ga Taylor cones and the emission current value reached several mAs. Then, emission current began to follow the Child–Langmuir law, and a clear field emission pattern from {011}-oriented tungsten was observed. Electrons emitted from the submicrometer sized area that is heated by itself with joule heating of current densities greater than 107 A/cm2.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135014338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Faezeh A. F. Lahiji, Samiran Bairagi, Roger Magnusson, Mauricio A. Sortica, Daniel Primetzhofer, Erik Ekström, Biplab Paul, Arnaud le Febvrier, Per Eklund
NiO thin films with varied oxygen contents are grown on Si(100) and c-Al2O3 at a substrate temperature of 300 °C using pulsed dc reactive magnetron sputtering. We characterize the structure and optical properties of NiO changes as functions of the oxygen content. NiO with the cubic structure, single phase, and predominant orientation along (111) is found on both substrates. X-ray diffraction and pole figure analysis further show that NiO on the Si(100) substrate exhibits fiber-textured growth, while twin domain epitaxy was achieved on c-Al2O3, with NiO(111)∥Al2O3(0001) and NiO[11¯0]∥Al2O3[101¯0] or NiO[1¯10]∥Al2O3[21¯1¯0] epitaxial relationship. The oxygen content in NiO films did not have a significant effect on the refractive index, extinction coefficient, and absorption coefficient. This suggests that the optical properties of NiO films remained unaffected by changes in the oxygen content.
{"title":"Growth and optical properties of NiO thin films deposited by pulsed dc reactive magnetron sputtering","authors":"Faezeh A. F. Lahiji, Samiran Bairagi, Roger Magnusson, Mauricio A. Sortica, Daniel Primetzhofer, Erik Ekström, Biplab Paul, Arnaud le Febvrier, Per Eklund","doi":"10.1116/6.0002914","DOIUrl":"https://doi.org/10.1116/6.0002914","url":null,"abstract":"NiO thin films with varied oxygen contents are grown on Si(100) and c-Al2O3 at a substrate temperature of 300 °C using pulsed dc reactive magnetron sputtering. We characterize the structure and optical properties of NiO changes as functions of the oxygen content. NiO with the cubic structure, single phase, and predominant orientation along (111) is found on both substrates. X-ray diffraction and pole figure analysis further show that NiO on the Si(100) substrate exhibits fiber-textured growth, while twin domain epitaxy was achieved on c-Al2O3, with NiO(111)∥Al2O3(0001) and NiO[11¯0]∥Al2O3[101¯0] or NiO[1¯10]∥Al2O3[21¯1¯0] epitaxial relationship. The oxygen content in NiO films did not have a significant effect on the refractive index, extinction coefficient, and absorption coefficient. This suggests that the optical properties of NiO films remained unaffected by changes in the oxygen content.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135154164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Stach, A. Seif, A. Ambrosetti, P. L. Silvestrelli, U. Burghaus
Experimental and theoretical evidence is presented that a sulfur compound dissociates on clean, defect-free epitaxial graphene (Gr) in ultrahigh vacuum (UHV). Together with density functional theory calculations (DFT), experimental kinetics and spectroscopic data suggest an auto-(/self)catalytic process. The results could open a pathway to a carbocatalyst. While adsorbing H2S in UHV at low temperatures on single-layer graphene/ruthenium (Gr/Ru), H2 desorbs and sulfur remains on the surface. Vacancy and grain boundary defects, respectively, can be excluded as active sites. DFT results indicate the importance of the Ru(0001) support in facilitating a reaction pathway with small activation energy for H2S dissociation. Gr becomes reactive due to a complex interplay of structural and electronic effects, including the corrugation of the graphene layer and the hybridization of ruthenium's d orbital with antibonding states of H2S.
{"title":"Enhancing the reactivity of clean, defect-free epitaxial graphene by the substrate—Experiment and theory","authors":"T. Stach, A. Seif, A. Ambrosetti, P. L. Silvestrelli, U. Burghaus","doi":"10.1116/6.0002948","DOIUrl":"https://doi.org/10.1116/6.0002948","url":null,"abstract":"Experimental and theoretical evidence is presented that a sulfur compound dissociates on clean, defect-free epitaxial graphene (Gr) in ultrahigh vacuum (UHV). Together with density functional theory calculations (DFT), experimental kinetics and spectroscopic data suggest an auto-(/self)catalytic process. The results could open a pathway to a carbocatalyst. While adsorbing H2S in UHV at low temperatures on single-layer graphene/ruthenium (Gr/Ru), H2 desorbs and sulfur remains on the surface. Vacancy and grain boundary defects, respectively, can be excluded as active sites. DFT results indicate the importance of the Ru(0001) support in facilitating a reaction pathway with small activation energy for H2S dissociation. Gr becomes reactive due to a complex interplay of structural and electronic effects, including the corrugation of the graphene layer and the hybridization of ruthenium's d orbital with antibonding states of H2S.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135154163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article reports a possible functionalization mechanism of isocyanate (NCO) groups on multiwalled carbon nanotubes (CNTs) with low-temperature plasma. The mechanism was clarified according to the analysis with two plasmas generated with the gas mixture of (1) nitrogen and carbon dioxide and (2) nitrogen and oxygen. We analyzed the mechanism through optical emission spectroscopy from these plasmas and the NCO functionalization ratio measured with the fluorescent method after plasma exposure over CNTs. The optical emission gave us information on the quantitative analysis of the gas species of atomic nitrogen (N), atomic oxygen (O), and carbon monoxide (CO) and the qualitative analysis of carbon nitride (CN) species in the plasma. Compared with our results from the gas species in the plasma and the NCO functionalization ratio on CNTs, CO and CN species in the gas phase in plasma are less likely to contribute to forming NCO groups on CNTs. Rather, the equal densities of atomic nitrogen and oxygen species in the plasma could be effective in forming NCO groups on the CNT surface: the NCO groups should form by N, O, and carbon (C) species on the CNT surface. The groups likely build up gradually by N, O, and C individually reaching a CNT surface, or the NCO radicals form in the gas phase and then attach to the CNT surface.
{"title":"Plasma functionalization mechanism to modify isocyanate groups on multiwalled carbon nanotubes","authors":"Daisuke Ogawa, Keiji Nakamura","doi":"10.1116/6.0002835","DOIUrl":"https://doi.org/10.1116/6.0002835","url":null,"abstract":"This article reports a possible functionalization mechanism of isocyanate (NCO) groups on multiwalled carbon nanotubes (CNTs) with low-temperature plasma. The mechanism was clarified according to the analysis with two plasmas generated with the gas mixture of (1) nitrogen and carbon dioxide and (2) nitrogen and oxygen. We analyzed the mechanism through optical emission spectroscopy from these plasmas and the NCO functionalization ratio measured with the fluorescent method after plasma exposure over CNTs. The optical emission gave us information on the quantitative analysis of the gas species of atomic nitrogen (N), atomic oxygen (O), and carbon monoxide (CO) and the qualitative analysis of carbon nitride (CN) species in the plasma. Compared with our results from the gas species in the plasma and the NCO functionalization ratio on CNTs, CO and CN species in the gas phase in plasma are less likely to contribute to forming NCO groups on CNTs. Rather, the equal densities of atomic nitrogen and oxygen species in the plasma could be effective in forming NCO groups on the CNT surface: the NCO groups should form by N, O, and carbon (C) species on the CNT surface. The groups likely build up gradually by N, O, and C individually reaching a CNT surface, or the NCO radicals form in the gas phase and then attach to the CNT surface.","PeriodicalId":17490,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"205 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135396879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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