Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147310
Matthew A. Marcus
The typical output of a STXM (Scanning Transmission X-ray (spectro)Microscopy) measurement is a data cube consisting of a set of images (measurements of X-ray transmission at a grid of pixels) taken at a sequence of incident energies. As with any experimental measurement, this raw data must be reduced to some standard form and interpreted. In this paper, I review the basics of how to go from raw data to information about the sample. I will discuss the fundamentals of X-ray spectromicroscopy, data reduction, descriptive and model-based analysis, and available software, with examples taken from the literature.
{"title":"Data analysis in spectroscopic STXM","authors":"Matthew A. Marcus","doi":"10.1016/j.elspec.2023.147310","DOIUrl":"10.1016/j.elspec.2023.147310","url":null,"abstract":"<div><p>The typical output of a STXM (Scanning Transmission X-ray (spectro)Microscopy) measurement is a data cube consisting of a set of images (measurements of X-ray transmission at a grid of pixels) taken at a sequence of incident energies. As with any experimental measurement, this raw data must be reduced to some standard form and interpreted. In this paper, I review the basics of how to go from raw data to information about the sample. I will discuss the fundamentals of X-ray spectromicroscopy, data reduction, descriptive and model-based analysis, and available software, with examples taken from the literature.</p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42178904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147317
Teresa de los Arcos , Hendrik Müller , Christian Weinberger , Guido Grundmeier
In this work, we discuss the possibility of improving charge neutralization in near ambient pressure X-ray photoelectron spectroscopy by co-irradiating the sample with He I photons of 21.2 eV. This UV-enhanced neutralization of charges is a variation of the so-called environmental charge compensation, which uses the electrons produced by the photoionization of the ambient gas to neutralize the positive charges built at the sample surface. Adding an additional ionization source generates more charges at the sample but also larger amounts of electrons available for neutralization. The final surface charge equilibrium depends on different aspects of the experiment, such as the sample composition and geometry, the total ionization cross sections of the gas compared to the surface materials, the gas used, the luminosity and spot size of the sources used for photoionization, and the energy of the electrons present in the gas phase. Here we illustrate the efficiency of the UV-enhanced neutralization using three different dielectric samples with different geometries (a porous SiO2 monolith with an irregular surface, a flat mica sample, and a thin SiO2 film deposited onto a Si substrate), different X-ray spot sizes, and two different gases (N2 and Ar). The effect of biasing on the efficiency of the sample surface to attract electrons produced in the gas phase is also discussed.
{"title":"UV-enhanced environmental charge compensation in near ambient pressure XPS","authors":"Teresa de los Arcos , Hendrik Müller , Christian Weinberger , Guido Grundmeier","doi":"10.1016/j.elspec.2023.147317","DOIUrl":"10.1016/j.elspec.2023.147317","url":null,"abstract":"<div><p><span>In this work, we discuss the possibility of improving charge neutralization in near ambient pressure X-ray photoelectron spectroscopy by co-irradiating the sample with He I photons of 21.2 eV. This UV-enhanced neutralization of charges is a variation of the so-called environmental charge compensation, which uses the electrons produced by the photoionization<span><span> of the ambient gas to neutralize the positive charges built at the sample surface. Adding an additional ionization source generates more charges at the sample but also larger amounts of electrons available for neutralization. The final surface charge equilibrium depends on different aspects of the experiment, such as the sample composition<span> and geometry, the total ionization cross sections of the gas compared to the surface materials, the gas used, the luminosity and spot size of the sources used for photoionization, and the energy of the electrons present in the gas phase. Here we illustrate the efficiency of the UV-enhanced neutralization using three different </span></span>dielectric samples with different geometries (a porous SiO</span></span><sub>2</sub> monolith with an irregular surface, a flat mica sample, and a thin SiO<sub>2</sub> film deposited onto a Si substrate), different X-ray spot sizes, and two different gases (N<sub>2</sub> and Ar). The effect of biasing on the efficiency of the sample surface to attract electrons produced in the gas phase is also discussed.</p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47467283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The use of carbon nitride-based materials and light to drive catalytic water splitting has enormous potential for the production of hydrogen. Revealing the processes of molecular conjugation, nucleation, and crystallization in crystalline carbon nitride is expected to enhance the photocatalytic activity through the creation of isotype heterojunctions and active sites. In this work, the addition of cobalt salts in ionothermal synthesis was found to promote the phase transition of heptazine-based crystalline carbon nitride (CCN) to triazine-based poly (triazine imide) (PTI), resulting in the formation of a single-atom cobalt-doped coordinated isotype CCN/PTI heterojunction. The new hybrid orbital modulates the atomic/electronic structure and the band gap of the CCN/PTI heterojunction, and synergistically increases the absorption of visible light, accelerating the separation and transfer of photoexcited electrons and holes. Synchrotron-based X-ray spectroscopy and microscopy are used to identify the origin of the improved performance of the single-atom cobalt-doped CCN/PTI heterojunction in the photocatalytic hydrogen evolution reaction. This work demonstrates that synchrotron X-ray spectroscopy is a promising tool for designing materials aimed at enhancing photocatalytic activity in solar energy conversion applications.
{"title":"Single-atom cobalt-incorporating carbon nitride for photocatalytic solar hydrogen conversion: An X-ray spectromicroscopy study","authors":"Yu-Cheng Huang , Jie Chen , Ying-Rui Lu , K. Thanigai Arul , Takuji Ohigashi , Jeng-Lung Chen , Chi-Liang Chen , Shaohua Shen , Wu-Ching Chou , Way-Faung Pong , Chung-Li Dong","doi":"10.1016/j.elspec.2023.147319","DOIUrl":"10.1016/j.elspec.2023.147319","url":null,"abstract":"<div><p><span><span>The use of carbon nitride-based materials and light to drive catalytic water splitting has enormous potential for the production of hydrogen. Revealing the processes of molecular conjugation, nucleation, and crystallization in crystalline carbon nitride is expected to enhance the </span>photocatalytic activity<span> through the creation of isotype heterojunctions and active sites. In this work, the addition of </span></span>cobalt salts<span><span> in ionothermal synthesis was found to promote the phase transition of heptazine-based crystalline carbon nitride (CCN) to triazine-based poly (triazine imide) (PTI), resulting in the formation of a single-atom cobalt-doped coordinated isotype CCN/PTI heterojunction. The new hybrid orbital<span><span> modulates the atomic/electronic structure and the band gap of the CCN/PTI heterojunction, and synergistically increases the absorption of visible light, accelerating the separation and transfer of photoexcited electrons and holes. Synchrotron-based X-ray spectroscopy and microscopy are used to identify the origin of the improved performance of the single-atom cobalt-doped CCN/PTI heterojunction in the photocatalytic </span>hydrogen evolution reaction. This work demonstrates that synchrotron X-ray spectroscopy is a promising tool for designing materials aimed at enhancing photocatalytic activity in </span></span>solar energy conversion applications.</span></p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42129202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147311
David J.H. Cant , Benjamen P. Reed , Ben F. Spencer , Wendy R. Flavell , Alexander G. Shard
The use of higher energy X-ray sources for photoelectron spectroscopy is receiving considerable attention due to the increased availability of laboratory-based instrumentation and an improved insight into the structures and interfacial properties of technological materials. In traditional X-ray photoelectron spectroscopy the design of the instrument often compensates for anisotropy in photoelectron emission through consideration of the angles between the X-ray source and the electron analyser. X-ray polarisation and non-dipole effects in photoemission are usually assumed to be negligible. However, for high energy XPS (HAXPES) both may be significant. Polarisation at synchrotron sources is an important consideration and non-dipole effects are generally more significant at higher photon energies. In this article we demonstrate that, for certain polarisations, ‘magic angle’ geometries exist that minimise the effects of both dipole and non-dipole contributions in photoemission. However, it is not possible to find such geometries for unpolarised X-rays; achieving a ‘magic angle’ geometry in HAXPES requires the X-rays to have a degree of linear polarisation of 1/3 or greater.
{"title":"Magic angle HAXPES","authors":"David J.H. Cant , Benjamen P. Reed , Ben F. Spencer , Wendy R. Flavell , Alexander G. Shard","doi":"10.1016/j.elspec.2023.147311","DOIUrl":"https://doi.org/10.1016/j.elspec.2023.147311","url":null,"abstract":"<div><p><span><span>The use of higher energy X-ray sources for photoelectron spectroscopy is receiving considerable attention due to the increased availability of laboratory-based instrumentation and an improved insight into the structures and </span>interfacial properties<span> of technological materials. In traditional X-ray photoelectron spectroscopy the design of the instrument often compensates for anisotropy in photoelectron emission through consideration of the angles between the X-ray source and the electron analyser. X-ray polarisation and non-dipole effects in </span></span>photoemission<span> are usually assumed to be negligible. However, for high energy XPS (HAXPES) both may be significant. Polarisation at synchrotron<span> sources is an important consideration and non-dipole effects are generally more significant at higher photon energies. In this article we demonstrate that, for certain polarisations, ‘magic angle’ geometries exist that minimise the effects of both dipole and non-dipole contributions in photoemission. However, it is not possible to find such geometries for unpolarised X-rays; achieving a ‘magic angle’ geometry in HAXPES requires the X-rays to have a degree of linear polarisation of 1/3 or greater.</span></span></p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49866397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147295
Fumihiko Matsui , Hiroshi Ota , Ritsuko Eguchi , Hidenori Goto , Kaya Kobayashi , Jun Akimitsu , Hikaru Ozaki , Takumi Nishioka , Koji Kimura , Kouichi Hayashi , Takuya Shimano , Naohisa Happo , Yoshihiro Kubozono
The local structure around Ag atoms in Ag-doped Bi2Se (AgBiSe) was investigated by photoelectron diffraction and X-ray fluorescence holography to understand the manner of Ag atom doping. At a low Ag concentration (), photoelectron diffraction indicated that Ag atoms occupied Bi substitution sites. However, a mere accumulation of holes via Ag substitution for Bi fails to explain the observed variation previously reported in the transport properties of Ag-doped Bi2Se with different values. In particular, simple Ag substitution for Bi fails to explain the pinning of the Fermi level at the bottom of conduction band, as suggested by the observed transport properties. In the case of a high Ag concentration (), photoelectron diffraction suggested that the Ag atoms occupied not only the substitutional Bi site but also multiple interstitial sites, namely, the octahedral site in the van der Waals interlayer and the interstitial site in the Se layer. Ag 3d photoelectron spectra revealed that the Ag atoms had the same oxidation state, , regardless of the type of occupied site. Furthermore, X-ray fluorescence holography was employed for a model-free local structural analysis that refined the exact locations of Ag atoms in the BiSe crystal lattice. The behavioral crossover documented herein from hole doping at the substitutional site to electron doping at multiple sites reasonably explains the dependence of electronic structures and transport properties of Ag-doped BiSe on dopant concentration.
{"title":"Multiple-site Ag doping in Bi2Se3: Compositional crossover from substitution to intercalation as revealed by photoelectron diffraction and X-ray fluorescence holography","authors":"Fumihiko Matsui , Hiroshi Ota , Ritsuko Eguchi , Hidenori Goto , Kaya Kobayashi , Jun Akimitsu , Hikaru Ozaki , Takumi Nishioka , Koji Kimura , Kouichi Hayashi , Takuya Shimano , Naohisa Happo , Yoshihiro Kubozono","doi":"10.1016/j.elspec.2023.147295","DOIUrl":"https://doi.org/10.1016/j.elspec.2023.147295","url":null,"abstract":"<div><p>The local structure around Ag atoms in Ag-doped Bi<sub>2</sub>Se<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> (Ag<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span>Bi<span><math><msub><mrow></mrow><mrow><mn>2</mn><mo>−</mo><mi>y</mi></mrow></msub></math></span>Se<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>) was investigated by photoelectron diffraction and X-ray fluorescence holography to understand the manner of Ag atom doping. At a low Ag concentration (<span><math><mrow><mi>x</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>05</mn></mrow></math></span>), photoelectron diffraction indicated that Ag atoms occupied Bi substitution sites. However, a mere accumulation of holes via Ag substitution for Bi fails to explain the observed variation previously reported in the transport properties of Ag-doped Bi<sub>2</sub>Se<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> with different <span><math><mi>x</mi></math></span> values. In particular, simple Ag substitution for Bi fails to explain the pinning of the Fermi level at the bottom of conduction band, as suggested by the observed transport properties. In the case of a high Ag concentration (<span><math><mrow><mi>x</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>2</mn></mrow></math></span>), photoelectron diffraction suggested that the Ag atoms occupied not only the substitutional Bi site but also multiple interstitial sites, namely, the octahedral site in the van der Waals interlayer and the interstitial site in the Se layer. Ag 3d photoelectron spectra revealed that the Ag atoms had the same oxidation state, <span><math><mrow><mo>+</mo><mn>1</mn></mrow></math></span>, regardless of the type of occupied site. Furthermore, X-ray fluorescence holography was employed for a model-free local structural analysis that refined the exact locations of Ag atoms in the Bi<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Se<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> crystal lattice. The behavioral crossover documented herein from hole doping at the substitutional site to electron doping at multiple sites reasonably explains the dependence of electronic structures and transport properties of Ag-doped Bi<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>Se<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> on dopant concentration.</p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49901162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147318
Guanhua Zhang , Lina Liu , Shengxue Zhou , Yu Liang , Julong Sun , Lei Liu , Chuanyao Zhou , Liying Jiao , Xueming Yang , Zefeng Ren
Ultrathin two-dimensional (2D) materials offer great potential for next-generation integrated circuit and optoelectronic devices. Chemical vapor deposition (CVD)-grown 2D materials provide a way to mass production in industry. However, how to in situ characterize their intrinsic electric/photoelectric properties and carrier dynamics with electron/photoelectron probes is still a problem due to the interference from the conducting substrate. Here, we present a grounding Au grids method to realize in situ characterization of the CVD-grown MoS2 on the insulating thick SiO2 layer covered Si substrate with spectroscopic photoemission and low energy electron microscopy (SPELEEM). Through depositing Au grids afterwards, we have achieved good grounding of MoS2 flakes in the photoemission electron microscopy (PEEM), mirror electron microscopy (MEM), and micro-area low energy electron diffraction (µ-LEED) measurements. We have clarified the false signal caused by stray photoelectrons originated from the Au stripes, and as well as the space charge effects induced by intense photoemission. We have also confirmed that time-resolved PEEM results are not affected by the stray signal, and by adopting a small light spot, both static and time-resolved micro-area photoelectron spectroscopy (µ-PES) can be unaffected by space charge effects. Our results provide a reliable way to in situ investigate 2D materials grown on insulating substrates by probing photoelectrons or backscattered electrons.
{"title":"Development of in situ characterization of two-dimensional materials grown on insulator substrates with spectroscopic photoemission and low energy electron microscopy","authors":"Guanhua Zhang , Lina Liu , Shengxue Zhou , Yu Liang , Julong Sun , Lei Liu , Chuanyao Zhou , Liying Jiao , Xueming Yang , Zefeng Ren","doi":"10.1016/j.elspec.2023.147318","DOIUrl":"10.1016/j.elspec.2023.147318","url":null,"abstract":"<div><p><span>Ultrathin two-dimensional (2D) materials offer great potential for next-generation integrated circuit and optoelectronic<span> devices. Chemical vapor deposition (CVD)-grown 2D materials provide a way to mass production in industry. However, how to </span></span><em>in situ</em> characterize their intrinsic electric/photoelectric properties and carrier dynamics with electron/photoelectron probes is still a problem due to the interference from the conducting substrate. Here, we present a grounding Au grids method to realize <em>in situ</em> characterization of the CVD-grown MoS<sub>2</sub> on the insulating thick SiO<sub>2</sub><span> layer covered Si substrate with spectroscopic photoemission<span> and low energy electron microscopy (SPELEEM). Through depositing Au grids afterwards, we have achieved good grounding of MoS</span></span><sub>2</sub><span><span> flakes in the photoemission electron microscopy (PEEM), mirror electron microscopy (MEM), and micro-area low energy electron diffraction (µ-LEED) measurements. We have clarified the false signal caused by stray photoelectrons originated from the Au stripes, and as well as the space charge effects induced by intense photoemission. We have also confirmed that time-resolved PEEM results are not affected by the stray signal, and by adopting a small light spot, both </span>static<span> and time-resolved micro-area photoelectron spectroscopy (µ-PES) can be unaffected by space charge effects. Our results provide a reliable way to </span></span><em>in situ</em> investigate 2D materials grown on insulating substrates by probing photoelectrons or backscattered electrons.</p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49301995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147312
Arban Uka , Greg O. Sitz
Using electron energy loss spectroscopy (EELS), we show that the surface plasmon loss intensity is highly sensitive to surface contamination. We exploit this property to develop a new variation of temperature programmed desorption (TPD),which we term virtual TPD (VTPD), that is uniquely sensitive to the sample surface. We apply this to a long standing puzzle in the behavior of atomic hydrogen adsorbed on Cu(100). We suggest that bulk absorption of hydrogen under ultra-high vacuum conditions is responsible for observed anomalies in this system. We show additional examples of VTPD to related systems.
{"title":"Electronic spectroscopy studies of Cu(100) following atomic hydrogen exposure","authors":"Arban Uka , Greg O. Sitz","doi":"10.1016/j.elspec.2023.147312","DOIUrl":"10.1016/j.elspec.2023.147312","url":null,"abstract":"<div><p><span>Using electron energy<span> loss spectroscopy (EELS), we show that the surface plasmon loss intensity is highly sensitive to </span></span>surface contamination. We exploit this property to develop a new variation of temperature programmed desorption (TPD),which we term virtual TPD (VTPD), that is uniquely sensitive to the sample surface. We apply this to a long standing puzzle in the behavior of atomic hydrogen adsorbed on Cu(100). We suggest that bulk absorption of hydrogen under ultra-high vacuum conditions is responsible for observed anomalies in this system. We show additional examples of VTPD to related systems.</p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48414110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147296
Z. Hussein , W. Khan , A. Laref , H.R. Alqahtani , Z.I.Y. Booq , R. Alsalamah , A. Ahmed , Fridolin Tchangnwa Nya , Shahariar Chowdhury , Mohammed El Amine Monir , Atul Kumar , H.M. Huang , Y.C. Xiong , J.T. Yang
Two-dimensional (2D) graphene with different forms is a prosperous class of materials beneficial in nano-electronics, and infrared-detector devices. Herein, we analyze the electronic and optical behaviours of electron acceptor (Al)- and isovalent (Si) inserted into graphene sheets, which are computed by utilizing ab-initio simulations. We find that the individual doping impurities of Al or Si atoms onto monolayer graphene result in p-type and semiconducting behaviours, respectively, attributed to the contribution of the valence electrons number of these atoms to the host 2D honeycomb lattice of graphene. Even though the Al atom contributing one less electron to the host lattice, both individual impurities of the Al- or Si-doped materials are found to cause a splitting in the valence states and conduction states at the K-point, leading to the opening of the Dirac cone. In monolayer graphene, doping two Al atoms into the nearest neighbour sites creates a trivial metallic system, while doping two Si atoms into the nearest neighbour sites causes the Dirac cone to re-emerge. Owing to the stark difference in the electronic structure results of mono- and double-atom substitution of Al/Si in graphene single-layers, we find different optical behaviours in these doped systems. Additionally, X-ray absorption spectroscopy simulations are employed to inspect the core-level spectra of pure and substitutional doped graphene single layers. Accordingly, the optical spectral features of graphene single-layers substituted with foreign impurities, such as Al/Si have revealed the tailoring of optical absorption from the infrared to the visible windows. Due to the outstanding characteristics of this 2D dimensional gapless graphene, our simulated results could provide a guidance for future experimental investigations into the fabrication of doped graphene sheets suitable for infrared detectors, photonics, and modern optoelectronic devices integrated into advanced technologies.
{"title":"Al/Si dopants effect on the electronic and optical behaviors of graphene mono-layers useful for infrared detector devices","authors":"Z. Hussein , W. Khan , A. Laref , H.R. Alqahtani , Z.I.Y. Booq , R. Alsalamah , A. Ahmed , Fridolin Tchangnwa Nya , Shahariar Chowdhury , Mohammed El Amine Monir , Atul Kumar , H.M. Huang , Y.C. Xiong , J.T. Yang","doi":"10.1016/j.elspec.2023.147296","DOIUrl":"10.1016/j.elspec.2023.147296","url":null,"abstract":"<div><p><span><span>Two-dimensional (2D) graphene with different forms is a prosperous class of materials beneficial in nano-electronics, and infrared-detector devices. Herein, we analyze the electronic and optical behaviours of electron acceptor (Al)- and isovalent (Si) inserted into graphene sheets, which are computed by utilizing ab-initio simulations. We find that the individual doping impurities of Al or Si atoms onto monolayer graphene result in p-type and semiconducting behaviours, respectively, attributed to the contribution of the valence electrons number of these atoms to the host 2D honeycomb lattice of graphene. Even though the Al atom contributing one less electron to the host lattice, both individual impurities of the Al- or Si-doped materials are found to cause a splitting in the valence states and conduction states at the K-point, leading to the opening of the Dirac cone. In monolayer graphene, doping two Al atoms into the nearest neighbour sites creates a trivial metallic system, while doping two Si atoms into the nearest neighbour sites causes the Dirac cone to re-emerge. Owing to the stark difference in the electronic structure results of mono- and double-atom substitution of Al/Si in graphene single-layers, we find different optical behaviours in these doped systems. Additionally, X-ray </span>absorption spectroscopy<span> simulations are employed to inspect the core-level spectra of pure and substitutional doped graphene single layers. Accordingly, the optical spectral features of graphene single-layers substituted with foreign impurities, such as Al/Si have revealed the tailoring of </span></span>optical absorption<span> from the infrared to the visible windows. Due to the outstanding characteristics of this 2D dimensional gapless graphene, our simulated results could provide a guidance for future experimental investigations into the fabrication of doped graphene sheets suitable for infrared detectors, photonics<span>, and modern optoelectronic devices integrated into advanced technologies.</span></span></p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48518967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147316
V. Karbivskyy , N. Kurgan , M. Huntush , A. Romansky , L. Karbivska , V. Zaika
The evolution of the valence band, the charge states of atoms, and the optical and vibrational spectra in Ca10(PO4)x(VO4)y(AsO4)z(OH)2 (x + y + z = 6) compound with three different types of oxygen tetrahedra have been studied by XPS, IR, and optical spectroscopy with the use of quantum mechanical calculation methods in the DFT approximation. It is shown that the occupied part of the valence band of compounds with three different types of tetrahedra has a pronounced band character with varying lengths of individual subbands. Two structural regions separated by energy are observed: the valence band's upper part and the valence band's lower part (subvalent states). The structure of the valence band's middle part, the region of valence states with energies from ∼ 13.0–19.0 eV, is weakly expressed. The sublattice of oxygen tetrahedra is decisive in forming the shape and the main features of the total density of electronic states of the compounds under study. The vibrations anharmonicity in the crystal lattice of such compounds can vary depending on the concentration of tetrahedra of a specific type. Such changes are local, and with the help of directed substitutions, it is possible to create the required spatial distribution of the anharmonic component over the crystal.
The design of the calcium apatites structure by the method of isomorphic substitutions of (XO4) tetrahedra with tetrahedra of various types and with different ratios makes it possible to control the energy band gap width.
采用DFT近似下的量子力学计算方法,用XPS、IR和光谱学方法研究了Ca10(PO4)x(VO4)y(AsO4)z(OH)2 (x + y + z = 6)三种不同氧四面体化合物的价带演化、原子电荷态以及光学和振动光谱。结果表明,三种不同类型的四面体化合物的价带占据部分具有明显的条带特征,每个子带的长度各不相同。观察到两个被能量分开的结构区域:价带的上部和价带的下部(亚价态)。价带的中间部分,即能在~ 13.0 ~ 19.0 eV之间的价态区域,其结构表达较弱。氧四面体的亚晶格对所研究化合物的形状和电子态总密度的主要特征的形成起决定性作用。这类化合物的晶格振动的非调和性可以根据特定类型的四面体的浓度而变化。这种变化是局部的,并且在定向取代的帮助下,可以在晶体上创建所需的非谐波分量的空间分布。采用(XO4)四面体与不同类型、不同比例的四面体同构取代的方法设计磷灰石钙结构,使能带隙宽度的控制成为可能。
{"title":"Spectral and quantum mechanical investigation of calcium apatites isomorphically substituted in the anionic sublattice","authors":"V. Karbivskyy , N. Kurgan , M. Huntush , A. Romansky , L. Karbivska , V. Zaika","doi":"10.1016/j.elspec.2023.147316","DOIUrl":"10.1016/j.elspec.2023.147316","url":null,"abstract":"<div><p><span><span><span>The evolution of the valence band, the </span>charge states of atoms, and the optical and </span>vibrational spectra in Ca</span><sub>10</sub>(PO<sub>4</sub>)<sub><em>x</em></sub>(VO<sub>4</sub>)<sub><em>y</em></sub>(AsO<sub>4</sub>)<sub><em>z</em></sub>(OH)<sub>2</sub> (<em>x</em> + <em>y</em> + <em>z</em><span><span> = 6) compound with three different types of oxygen tetrahedra have been studied by XPS, IR, and optical spectroscopy<span> with the use of quantum mechanical calculation methods in the DFT<span> approximation. It is shown that the occupied part of the valence band of compounds with three different types of tetrahedra has a pronounced band character with varying lengths of individual subbands<span>. Two structural regions separated by energy are observed: the valence band's upper part and the valence band's lower part (subvalent states). The structure of the valence band's middle part, the region of valence states with energies from ∼ 13.0–19.0 eV, is weakly expressed. The sublattice of oxygen tetrahedra is decisive in forming the shape and the main features of the total density of electronic states of the compounds under study. The vibrations anharmonicity in the </span></span></span></span>crystal lattice of such compounds can vary depending on the concentration of tetrahedra of a specific type. Such changes are local, and with the help of directed substitutions, it is possible to create the required spatial distribution of the anharmonic component over the crystal.</span></p><p><span>The design of the calcium apatites structure by the method of isomorphic substitutions of (XO</span><sub>4</sub><span>) tetrahedra with tetrahedra of various types and with different ratios makes it possible to control the energy band gap width.</span></p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46231649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-01DOI: 10.1016/j.elspec.2023.147313
Hiroyuki Matsuda , Hiroki Momono , László Tóth , Yu Masuda , Koichi Moriguchi , Keiko Ogai , Hiroshi Daimon
A compact wide-acceptance angle (around ± 50°) high-energy-resolution 2D electron analyzer CoDELMA (Compact DELMA) is proposed, constructed and tested. CoDELMA is composed of a recently-proposed variable-deceleration-ratio wide-acceptance-angle electrostatic lens (VD-WAAEL), a cylindrical mirror analyzer (CMA) and a projection lens. After a brief review of VD-WAAEL, the use of a plane grid in the lens is presented as a new design option, which allows keeping the focusing angle almost constant irrespective of the deceleration ratio. A detailed consideration is given to the combination of CMA and a projection lens, which allows simultaneous analysis of wide reciprocal ( ± 8°) and real space ( ± 5 mm) at the entrance of CMA. CoDELMA is the successor to the previously developed DELMA instrument including a concentric hemispherical analyzer. The whole system of CoDELMA becomes much more compact than that of DELMA owing to the use of VD-WAAEL and CMA, and this results in considerable reduction of the production cost. Results of test measurement of energy spectrum and angular distribution using an electron gun as an excitation source confirmed that the energy resolution and the acceptance angle are almost the same as the designed values.
{"title":"Compact 2D electron analyzer CoDELMA: Simultaneous wide reciprocal and real space analysis using wide-angle deceleration lens, CMA and projection lens","authors":"Hiroyuki Matsuda , Hiroki Momono , László Tóth , Yu Masuda , Koichi Moriguchi , Keiko Ogai , Hiroshi Daimon","doi":"10.1016/j.elspec.2023.147313","DOIUrl":"10.1016/j.elspec.2023.147313","url":null,"abstract":"<div><p>A compact wide-acceptance angle (around ± 50°) high-energy-resolution 2D electron analyzer CoDELMA (Compact DELMA) is proposed, constructed and tested. CoDELMA is composed of a recently-proposed variable-deceleration-ratio wide-acceptance-angle electrostatic<span> lens (VD-WAAEL), a cylindrical mirror analyzer (CMA) and a projection lens. After a brief review of VD-WAAEL, the use of a plane grid in the lens is presented as a new design option, which allows keeping the focusing angle almost constant irrespective of the deceleration ratio. A detailed consideration is given to the combination of CMA and a projection lens, which allows simultaneous analysis of wide reciprocal ( ± 8°) and real space ( ± 5 mm) at the entrance of CMA. CoDELMA is the successor to the previously developed DELMA instrument including a concentric hemispherical analyzer. The whole system of CoDELMA becomes much more compact than that of DELMA owing to the use of VD-WAAEL and CMA, and this results in considerable reduction of the production cost. Results of test measurement of energy spectrum and angular distribution using an electron gun as an excitation source confirmed that the energy resolution and the acceptance angle are almost the same as the designed values.</span></p></div>","PeriodicalId":15726,"journal":{"name":"Journal of Electron Spectroscopy and Related Phenomena","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48012486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}