Pub Date : 2024-06-19DOI: 10.1016/j.susc.2024.122537
Amin Mohammadpour , Sarp Kaya
The surface structure and atomic composition can affect the adsorption characteristics of water on metal surfaces. In this study, we investigated the adsorption of water on Cu(211) stepped surfaces decorated with Pt by a combination of infrared reflection absorption spectroscopy (IRRAS) and temperature-programmed desorption (TPD) studies. We have observed that step sites of Cu can increase the strength of the binding of water molecules to the surface and facilitate water partial dissociation and the formation of OH groups on the surface. Step decoration by Pt can change the water adsorption characteristics and eliminate the water dissociation. Water adsorbs molecularly on the fully Pt-decorated steps of the Cu(211) surface. Molecular water and OH adsorbed on Cu(211), which can make a chain structure, are disrupted with Pt atoms.
{"title":"Probing water adsorption characteristics of Pt step-edge decorated Cu(211) surface","authors":"Amin Mohammadpour , Sarp Kaya","doi":"10.1016/j.susc.2024.122537","DOIUrl":"https://doi.org/10.1016/j.susc.2024.122537","url":null,"abstract":"<div><p>The surface structure and atomic composition can affect the adsorption characteristics of water on metal surfaces. In this study, we investigated the adsorption of water on Cu(211) stepped surfaces decorated with Pt by a combination of infrared reflection absorption spectroscopy (IRRAS) and temperature-programmed desorption (TPD) studies. We have observed that step sites of Cu can increase the strength of the binding of water molecules to the surface and facilitate water partial dissociation and the formation of OH groups on the surface. Step decoration by Pt can change the water adsorption characteristics and eliminate the water dissociation. Water adsorbs molecularly on the fully Pt-decorated steps of the Cu(211) surface. Molecular water and OH adsorbed on Cu(211), which can make a chain structure, are disrupted with Pt atoms.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141487217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-17DOI: 10.1016/j.susc.2024.122538
A. Grespi , A. Larsson , G. Abbondanza , J. Eidhagen , D. Gajdek , J. Manidi , A. Tayal , J. Pan , L.R. Merte , E. Lundgren
Traditional methods to study electrochemical (EC) processes, although successful, are based on current/voltage measurements, providing information about performances rather than offering a direct observation of chemical and structural changes occurring at the electrode surface. These processes are localized at the electrode-electrolyte interface, the structure of which is the main determinant of their behavior, but most surface sensitive experimental techniques are limited to ex situ conditions, owing to the need for an ultra-high vacuum environment. In this contribution, we report operando X-ray absorption spectroscopy in total external reflection geometry (Refle-XAFS) at P64 beamline (DESY, Hamburg), using a simple and versatile EC flow cell designed for multimodal surface sensitive studies with hard X-ray scattering and spectroscopy techniques. We show that the Refle-XAFS method can be used to study chemical surface changes of industrial alloys and model electrodes in harsh electrochemical environments, without being limited to thin film samples. The surface passive film development and breakdown of a corrosion-resistant Ni-Cr-Mo alloy and the electro-oxidation of polycrystalline gold (poly-Au), relevant for fundamental studies on water electrolysis, were investigated. Despite the strong attenuation of the beam by the electrolyte and the PEEK walls of the EC cell, nanoscale surface oxide films were detected using beam energies down to 8 keV. The passivity breakdown region of Ni alloy 59 in 1 M NaCl at pH 7 and pH 12 was identified, showing differences in the composition of the surface oxides during anodic polarization. The electro-oxidation of poly-Au in 0.05 M H2SO4 was observed, showing a progression from two-dimensional Au1+/3+ to three-dimensional thick Au3+ surface oxide/hydroxide during OER.
研究电化学(EC)过程的传统方法虽然很成功,但都是基于电流/电压测量,只能提供有关性能的信息,而不能直接观察电极表面发生的化学和结构变化。这些过程都发生在电极-电解质界面,其结构是决定其行为的主要因素,但由于需要超高真空环境,大多数表面敏感实验技术都仅限于原位条件。在这篇论文中,我们报告了在 P64 光束线(汉堡 DESY)使用简单、多功能的 EC 流动池,利用硬 X 射线散射和光谱技术进行多模态表面敏感研究的全外反射几何(Refle-XAFS)操作 X 射线吸收光谱。我们的研究表明,Refle-XAFS 方法可用于研究工业合金和模型电极在恶劣电化学环境下的化学表面变化,而不局限于薄膜样品。我们研究了耐腐蚀镍铬钼合金表面被动膜的发展和破坏,以及多晶金(poly-Au)的电氧化过程,这与水电解的基础研究息息相关。尽管电解质和电解槽的 PEEK 壁对光束有很强的衰减,但使用低至 8 keV 的光束能量仍能检测到纳米级的表面氧化膜。确定了镍合金 59 在 pH 值为 7 和 12 的 1 M NaCl 溶液中的钝性击穿区,显示了阳极极化过程中表面氧化物成分的差异。在 0.05 M H2SO4 中观察了聚金的电氧化过程,显示了在 OER 过程中从二维 Au1+/3+ 到三维厚 Au3+ 表面氧化物/氢氧化物的发展过程。
{"title":"Probing the electrode-liquid interface using operando total-reflection X-ray absorption spectroscopy","authors":"A. Grespi , A. Larsson , G. Abbondanza , J. Eidhagen , D. Gajdek , J. Manidi , A. Tayal , J. Pan , L.R. Merte , E. Lundgren","doi":"10.1016/j.susc.2024.122538","DOIUrl":"https://doi.org/10.1016/j.susc.2024.122538","url":null,"abstract":"<div><p>Traditional methods to study electrochemical (EC) processes, although successful, are based on current/voltage measurements, providing information about performances rather than offering a direct observation of chemical and structural changes occurring at the electrode surface. These processes are localized at the electrode-electrolyte interface, the structure of which is the main determinant of their behavior, but most surface sensitive experimental techniques are limited to <em>ex situ</em> conditions, owing to the need for an ultra-high vacuum environment. In this contribution, we report <em>operando</em> X-ray absorption spectroscopy in total external reflection geometry (Refle-XAFS) at P64 beamline (DESY, Hamburg), using a simple and versatile EC flow cell designed for multimodal surface sensitive studies with hard X-ray scattering and spectroscopy techniques. We show that the Refle-XAFS method can be used to study chemical surface changes of industrial alloys and model electrodes in harsh electrochemical environments, without being limited to thin film samples. The surface passive film development and breakdown of a corrosion-resistant Ni-Cr-Mo alloy and the electro-oxidation of polycrystalline gold (poly-Au), relevant for fundamental studies on water electrolysis, were investigated. Despite the strong attenuation of the beam by the electrolyte and the PEEK walls of the EC cell, nanoscale surface oxide films were detected using beam energies down to 8 keV. The passivity breakdown region of Ni alloy 59 in 1 M NaCl at pH 7 and pH 12 was identified, showing differences in the composition of the surface oxides during anodic polarization. The electro-oxidation of poly-Au in 0.05 M H<sub>2</sub>SO<sub>4</sub> was observed, showing a progression from two-dimensional Au<sup>1+/3+</sup> to three-dimensional thick Au<sup>3+</sup> surface oxide/hydroxide during OER.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S003960282400089X/pdfft?md5=14bb2737a7cfd4a31739ee94897263b5&pid=1-s2.0-S003960282400089X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141429738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-13DOI: 10.1016/j.susc.2024.122536
A.L. Okana-Lomanga , G. Dimitri Ngantso , B.R. Malonda-Boungou , A.T. Raji , B. M'Passi-Mabiala
We report on spin-polarized density-functional theory study of adsorption of dihalogen molecules X2 (X = F, Cl, Br and I) on the Fe/W(110) substrate, i.e., X2/Fe/W(110) systems. We considered different molecular orientations and adsorption sites of the halogens and obtained their corresponding ground-state structures. We obtained initial molecular orientation (IMO) and initial adsorption site (IAS), i.e., IMO-IAS combinations that give the minimum energy configurations for each of the X2/Fe/W(110) systems. Our results shows that all the molecules studied in this work are chemisorbed on the Fe surface. Also, the halogen atoms may be adsorbed dissociatively on the hollow sites in such a way that an X2 separates into two X atoms with each of the atoms located at two nearby hollow sites. Similarly, we found IMO-IAS combinations which resulted in a non-dissociative adsorption. In the latter, the pre-relaxed IMO-IAS is maintained even after the structural relaxation. The most stable configuration for the X2 dihalogen molecule in this case is either the top or bridge site while the halogen is in perpendicular orientation to the Fe surface. We conclude therefore that, the final relaxed configurations of the X2 halogen depends on the IMO through which is deposited on the Fe/W(110) substrate. The trend in the adsorption energy EA for the most stable configurations for the dissociative adsorption is EA (F) > EA (Cl) > EA (Br) > EA (I). The trend of EA for non-dissociative adsorption is similar to that of dissociative adsorption, however, the latter is the more energetically favorable. Electronic structure calculations show hybridization between the p and d orbitals of X and Fe atoms respectively. Furthermore, we have found antiferromagnetic coupling between the interfacial W atoms and the Fe overlayer atoms while ferromagnetic coupling is found between the halogens and the Fe atoms. Our work represents a detailed study of adsorption properties of highly reactive halogens in contact with the Fe/W(100) surface.
我们报告了二卤素分子 X2(X = F、Cl、Br 和 I)在 Fe/W(110)基底(即 X2/Fe/W(110) 系统)上吸附的自旋极化密度泛函理论研究。我们考虑了卤素的不同分子取向和吸附位点,并得到了其相应的基态结构。我们得到了初始分子取向(IMO)和初始吸附位点(IAS),即 IMO-IAS 组合,这些组合给出了每个 X2/Fe/W(110) 系统的最小能量构型。我们的研究结果表明,这项工作中研究的所有分子都在铁表面发生了化学吸附。此外,卤素原子可能以离解的方式吸附在空心位点上,从而使一个 X2 分离成两个 X 原子,每个原子都位于附近的两个空心位点上。同样,我们发现 IMO-IAS 组合也会导致非离解吸附。在后者中,即使在结构松弛后,也能保持预先松弛的 IMO-IAS 结构。在这种情况下,X2 二卤素分子最稳定的构型是顶部位点或桥位点,而卤素则与铁表面垂直。因此我们得出结论,X2 卤素的最终弛豫构型取决于沉积在 Fe/W(110)基底上的 IMO。解离吸附的最稳定构型的吸附能 EA 的趋势是 EA (F) > EA (Cl) > EA (Br) > EA (I)。非解离吸附的 EA 变化趋势与解离吸附相似,但后者在能量上更为有利。电子结构计算显示,X 原子和 Fe 原子的 p 和 d 轨道之间分别存在杂化现象。此外,我们还发现了界面 W 原子和铁覆盖层原子之间的反铁磁耦合,而卤素和铁原子之间则存在铁磁耦合。我们的工作是对与 Fe/W(100)表面接触的高活性卤素吸附特性的详细研究。
{"title":"Adsorption of dihalogen molecules X2 (X = F, Cl, Br and I) on the Fe/W(110) substrate","authors":"A.L. Okana-Lomanga , G. Dimitri Ngantso , B.R. Malonda-Boungou , A.T. Raji , B. M'Passi-Mabiala","doi":"10.1016/j.susc.2024.122536","DOIUrl":"10.1016/j.susc.2024.122536","url":null,"abstract":"<div><p>We report on spin-polarized density-functional theory study of adsorption of dihalogen molecules X<sub>2</sub> (<em>X</em> = <em>F</em>, Cl, Br and I) on the Fe/W(110) substrate, i.e., X<sub>2</sub>/Fe/W(110) systems. We considered different molecular orientations and adsorption sites of the halogens and obtained their corresponding ground-state structures. We obtained initial molecular orientation (IMO) and initial adsorption site (IAS), i.e., IMO-IAS combinations that give the minimum energy configurations for each of the X<sub>2</sub>/Fe/W(110) systems. Our results shows that all the molecules studied in this work are chemisorbed on the Fe surface. Also, the halogen atoms may be adsorbed dissociatively on the <em>hollow</em> sites in such a way that an X<sub>2</sub> separates into two X atoms with each of the atoms located at two nearby <em>hollow</em> sites. Similarly, we found IMO-IAS combinations which resulted in a non-dissociative adsorption. In the latter, the pre-relaxed IMO-IAS is maintained even after the structural relaxation. The most stable configuration for the X<sub>2</sub> dihalogen molecule in this case is either the <em>top</em> or <em>bridge</em> site while the halogen is in perpendicular orientation to the Fe surface. We conclude therefore that, the final relaxed configurations of the X<sub>2</sub> halogen depends on the IMO through which is deposited on the Fe/W(110) substrate. The trend in the adsorption energy E<sub>A</sub> for the most stable configurations for the dissociative adsorption is <em>E<sub>A</sub></em> (F) > <em>E<sub>A</sub></em> (Cl) > <em>E<sub>A</sub></em> (Br) > <em>E<sub>A</sub></em> (I). The trend of <em>E</em><sub>A</sub> for non-dissociative adsorption is similar to that of dissociative adsorption, however, the latter is the more energetically favorable. Electronic structure calculations show hybridization between the <em>p</em> and <em>d</em> orbitals of X and Fe atoms respectively. Furthermore, we have found antiferromagnetic coupling between the interfacial W atoms and the Fe overlayer atoms while ferromagnetic coupling is found between the halogens and the Fe atoms. Our work represents a detailed study of adsorption properties of highly reactive halogens in contact with the Fe/W(100) surface.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141392085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-12DOI: 10.1016/j.susc.2024.122534
Talin Avanesian , Zubin Darbari , Marija Iloska , J. Anibal Boscoboinik , Qin Wu
The stretching frequency of the CO bond is a sensitive probe of the local environment of a surface-bound CO molecule, including the adorption site and density, i.e. surface coverage. In this work, we extend our analysis beyond the frequency shift due to differences in adsorption configurations. Using density functional theory (DFT) calculations, we directly explore the correlations between surface coverage and the stretching frequency of adsorbed CO on Pd surfaces. We also perform constant pressure infrared reflection absorption measurements of CO on Pd(111) and use existing relations between pressure and coverage to derive coverage dependency. Both results are compared to previously reported experimental data. Our derived correlations of peak frequency and area with surface coverage can help interpret experimental IR spectra in real time and extract time-dependent concentration data from transient kinetic experiments.
一氧化碳键的拉伸频率是表面结合的一氧化碳分子局部环境的敏感探测器,包括吸附位点和密度,即表面覆盖率。在这项工作中,我们将分析范围扩展到了因吸附构型不同而产生的频率偏移之外。利用密度泛函理论(DFT)计算,我们直接探索了表面覆盖率与钯表面吸附的 CO 拉伸频率之间的相关性。我们还对钯(111)上的 CO 进行了恒压红外反射吸收测量,并利用压力和覆盖率之间的现有关系得出了覆盖率依赖性。这两个结果都与之前报告的实验数据进行了比较。我们推导出的峰值频率和面积与表面覆盖率的相关性有助于实时解释实验红外光谱,并从瞬态动力学实验中提取随时间变化的浓度数据。
{"title":"Investigation of coverage dependence of the stretching frequency of CO adsorbed on Pd surfaces at low coverage limits","authors":"Talin Avanesian , Zubin Darbari , Marija Iloska , J. Anibal Boscoboinik , Qin Wu","doi":"10.1016/j.susc.2024.122534","DOIUrl":"https://doi.org/10.1016/j.susc.2024.122534","url":null,"abstract":"<div><p>The stretching frequency of the C<img>O bond is a sensitive probe of the local environment of a surface-bound CO molecule, including the adorption site and density, i.e. surface coverage. In this work, we extend our analysis beyond the frequency shift due to differences in adsorption configurations. Using density functional theory (DFT) calculations, we directly explore the correlations between surface coverage and the stretching frequency of adsorbed CO on Pd surfaces. We also perform constant pressure infrared reflection absorption measurements of CO on Pd(111) and use existing relations between pressure and coverage to derive coverage dependency. Both results are compared to previously reported experimental data. Our derived correlations of peak frequency and area with surface coverage can help interpret experimental IR spectra in real time and extract time-dependent concentration data from transient kinetic experiments.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141333373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-08DOI: 10.1016/j.susc.2024.122535
Yathrib Ajaj , Saade Abdalkareem Jasim , Ehab Salam Hussein , Yasir W. Issa , Carlos Alberto Alban Hurtado , Yazen.M. Alawaideh , Mohammed Al-Bahrani , Hamad Almujibah , Rahadian Zainul
Volatile organic compounds (VOCs) cause a considerable risk to human life, and it is vital to introduce highly efficient VOC biosensors. Methanol (CH3OH) was identified as a vital biomarker, showing significant elevation in both lung cancer and COVID-19 patients. Two-dimensional (2D) semiconductor gas sensors offer benefits such as excellent sensitivity, resistance to high temperatures and stability. In the present study, we explored methanol adsorption on the pristine and transition metal (TM)-doped (Sc, Ti, V, Cr, and Mn) C3B 2D flakes with the density functional theory (DFT) technique. Our results revealed that the V-, Cr-, and Mn-doped C3B show larger adsorption energy values as compared to the pristine C3B surface. The change of band gap energy of surfaces after methanol adsorption is obtained between 40 and 400 %. Besides, results show that methanol has a quick recovery at room temperature. The work function variation of studied flakes upon methanol adsorption has been also investigated and results show that V-, Cr-, and Mn-doped C3B systems are sensitive to methanol gas molecule. This work suggests that the C3B-based flakes can be used as a biosensor to identify VOC biomarkers such as methanol.
{"title":"Methanol gas sensing properties of transition metals (V, Cr, and Mn)-doped BC3 flake","authors":"Yathrib Ajaj , Saade Abdalkareem Jasim , Ehab Salam Hussein , Yasir W. Issa , Carlos Alberto Alban Hurtado , Yazen.M. Alawaideh , Mohammed Al-Bahrani , Hamad Almujibah , Rahadian Zainul","doi":"10.1016/j.susc.2024.122535","DOIUrl":"10.1016/j.susc.2024.122535","url":null,"abstract":"<div><p>Volatile organic compounds (VOCs) cause a considerable risk to human life, and it is vital to introduce highly efficient VOC biosensors. Methanol (CH<sub>3</sub>OH) was identified as a vital biomarker, showing significant elevation in both lung cancer and COVID-19 patients. Two-dimensional (2D) semiconductor gas sensors offer benefits such as excellent sensitivity, resistance to high temperatures and stability. In the present study, we explored methanol adsorption on the pristine and transition metal (TM)-doped (<em>Sc</em>, Ti, V, Cr, and Mn) C3B 2D flakes with the density functional theory (DFT) technique. Our results revealed that the V-, Cr-, and Mn-doped C3B show larger adsorption energy values as compared to the pristine C3B surface. The change of band gap energy of surfaces after methanol adsorption is obtained between 40 and 400 %. Besides, results show that methanol has a quick recovery at room temperature. The work function variation of studied flakes upon methanol adsorption has been also investigated and results show that V-, Cr-, and Mn-doped C3B systems are sensitive to methanol gas molecule. This work suggests that the C3B-based flakes can be used as a biosensor to identify VOC biomarkers such as methanol.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141401869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-07DOI: 10.1016/j.susc.2024.122533
David Khayata, Gil M. Repa, Lisa A. Fredin
Localized surface plasmons (LSP) on faceted surfaces of gold nanoparticles enable carbon monoxide disproportionation to be driven at room temperature. In order to expand the known surfaces that catalyze this reaction, we explore the adsorption of carbon monoxide at top, long bridge, short bridge, and hole sites on gold (100), (110), (111), (211), and (311) faceted surfaces, as well as the reaction barriers for disproportionation at the lowest energy adsorption site on each surface and edges between two (311) surfaces and (100) and (110) surfaces. Generally, the less atomically dense, higher index facets promote both good adsorption and reactivity, and the edges show lower barriers for disproportionation. For most of the explored surfaces, adsorption directly on top of a gold atom is most favorable. The lowest activation energy for carbon monoxide disproportionation to amorphous carbon and carbon dioxide is predicted for two carbon monoxides adsorbed on top of atoms on the (311)/(311) edge.
{"title":"Adsorption and disproportionation of carbon monoxide on faceted-gold surfaces and edges","authors":"David Khayata, Gil M. Repa, Lisa A. Fredin","doi":"10.1016/j.susc.2024.122533","DOIUrl":"https://doi.org/10.1016/j.susc.2024.122533","url":null,"abstract":"<div><p>Localized surface plasmons (LSP) on faceted surfaces of gold nanoparticles enable carbon monoxide disproportionation to be driven at room temperature. In order to expand the known surfaces that catalyze this reaction, we explore the adsorption of carbon monoxide at top, long bridge, short bridge, and hole sites on gold (100), (110), (111), (211), and (311) faceted surfaces, as well as the reaction barriers for disproportionation at the lowest energy adsorption site on each surface and edges between two (311) surfaces and (100) and (110) surfaces. Generally, the less atomically dense, higher index facets promote both good adsorption and reactivity, and the edges show lower barriers for disproportionation. For most of the explored surfaces, adsorption directly on top of a gold atom is most favorable. The lowest activation energy for carbon monoxide disproportionation to amorphous carbon and carbon dioxide is predicted for two carbon monoxides adsorbed on top of atoms on the (311)/(311) edge.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141302746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Silicon carbide (SiC) is a promising third-generation semiconductor due to its wide bandgap. However, the high Schottky barrier and metal-induced gap states (MIGS) at the metal/SiC interface present significant challenges for device fabrication, leading to high contact resistance and poor current delivery. This study proposes the use of bismuth (Bi), with its semimetallic properties and gap-state saturation effect, as a contact buffer layer to address these issues. We conducted a systematic investigation of the chemical and electronic characteristics of the Pt/Bi/4H-SiC(0001) system, fabricated via molecular beam epitaxy (MBE), using in situ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Our findings reveal weak bonding between the Bi buffer layer and the 4H-SiC(0001) surface, resulting in a slight downward band bending effect and the formation of a substantial dipole across the Bi/4H-SiC(0001) interface. Moreover, UPS spectra indicate a reduction in the work function of Pt/Bi/4H-SiC(0001), suggesting the potential for achieving low contact resistance. Notably, the Pt/Bi/4H-SiC(0001) system remains stable when exposed to 1.6×109 Langmuir of oxygen at room temperature, while a bare Bi buffer layer undergoes partial oxidation. These results provide a comprehensive understanding of the Pt/Bi/4H-SiC(0001) interfaces and strategies for improving metal/SiC contacts.
{"title":"Bismuth as a buffer layer for metal contact with silicon carbide studied by In situ photoelectron spectroscopy","authors":"Xiangrui Geng , Yishui Ding , Sisheng Duan , Wei Chen","doi":"10.1016/j.susc.2024.122530","DOIUrl":"https://doi.org/10.1016/j.susc.2024.122530","url":null,"abstract":"<div><p>Silicon carbide (SiC) is a promising third-generation semiconductor due to its wide bandgap. However, the high Schottky barrier and metal-induced gap states (MIGS) at the metal/SiC interface present significant challenges for device fabrication, leading to high contact resistance and poor current delivery. This study proposes the use of bismuth (Bi), with its semimetallic properties and gap-state saturation effect, as a contact buffer layer to address these issues. We conducted a systematic investigation of the chemical and electronic characteristics of the Pt/Bi/4H-SiC(0001) system, fabricated via molecular beam epitaxy (MBE), using <em>in situ</em> X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Our findings reveal weak bonding between the Bi buffer layer and the 4H-SiC(0001) surface, resulting in a slight downward band bending effect and the formation of a substantial dipole across the Bi/4H-SiC(0001) interface. Moreover, UPS spectra indicate a reduction in the work function of Pt/Bi/4H-SiC(0001), suggesting the potential for achieving low contact resistance. Notably, the Pt/Bi/4H-SiC(0001) system remains stable when exposed to 1.6×10<sup>9</sup> Langmuir of oxygen at room temperature, while a bare Bi buffer layer undergoes partial oxidation. These results provide a comprehensive understanding of the Pt/Bi/4H-SiC(0001) interfaces and strategies for improving metal/SiC contacts.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141313194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-04DOI: 10.1016/j.susc.2024.122523
E.V. Rut'kov, E.Y. Afanas'eva, N.R. Gall
High-temperature joint adsorption has been studied of three different adsorbates, Si, Be, and P on the Re face. All three adsorbates form surface compounds with the stoichiometry ReX, where X is Si, Be, and P. In joint adsorption, one of the adsorbates is displaced into the bulk, into the dissolved state. The processes are observed at a temperature sufficient for diffusion in the bulk, 1100–1300 K. Displacement occurs in an atom-to-atom mode, and it has a “cyclic nature”: silicon displaces phosphorus, beryllium displaces silicon, and phosphorus - beryllium.
我们研究了三种不同吸附剂 Si、Be 和 P 在 (101¯0) Re 面上的高温联合吸附。在联合吸附过程中,其中一种吸附剂被转移到体液中,进入溶解状态。位移以原子到原子的方式发生,具有 "循环性质":硅位移到磷,铍位移到硅,磷位移到铍。
{"title":"Competition between silicon, beryllium and phosphorus atoms in the formation of surface chemical compounds on (101¯0) Re","authors":"E.V. Rut'kov, E.Y. Afanas'eva, N.R. Gall","doi":"10.1016/j.susc.2024.122523","DOIUrl":"https://doi.org/10.1016/j.susc.2024.122523","url":null,"abstract":"<div><p>High-temperature joint adsorption has been studied of three different adsorbates, Si, Be, and P on the <span><math><mrow><mo>(</mo><mrow><mn>10</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>0</mn></mrow><mo>)</mo></mrow></math></span> Re face. All three adsorbates form surface compounds with the stoichiometry ReX, where X is Si, Be, and P. In joint adsorption, one of the adsorbates is displaced into the bulk, into the dissolved state. The processes are observed at a temperature sufficient for diffusion in the bulk, 1100–1300 K. Displacement occurs in an atom-to-atom mode, and it has a “cyclic nature”: silicon displaces phosphorus, beryllium displaces silicon, and phosphorus - beryllium.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141289435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-22DOI: 10.1016/j.susc.2024.122511
Mengting Ma , Guili Liu , Guoying Zhang
The density functional theory is employed for learning the modulation of the electronic structure and magnetic properties of monolayer SnSe2 by an Mn atom and by co-doping an Mn atom with a halogen atom. It is found that intrinsic SnSe2 is nonmagnetic, which is consistent with the properties of semiconductors. Following Mn atom doping, the doped system is magnetic and the magnetic moments are primarily responsible for the Mn atom. After co-doping the Mn atom with halogen atoms, the doped system's total magnetic moments are decreased. The examination of the electronic structure demonstrates that the doping of the Mn atom and the co-doping of the Mn atom with halogen atoms lead to the introduction of impurity energy levels into the doped system, which appear only in the spin-up part and do not cross the Fermi energy level. There is asymmetry between the spin-up and spin-down energy bands and the doped system exhibits magnetic semiconductor properties. The hybridization of the p-orbitals of the halogen atoms and the 3d orbitals of the Mn atom is primarily responsible for the introduction of impurity energy levels in the energy bands of the doped system. In the Mn-doped system, ionic bonds were shaped between Mn and Se. In the co-doped system, strong ionic bonds were shaped between the Mn atom and F, Cl atoms, and covalent bonds were shaped between the Mn atom and Br, I atoms.
利用密度泛函理论研究了锰原子以及锰原子与卤素原子共掺杂对单层 SnSe2 电子结构和磁性能的调制。研究发现,本征 SnSe2 无磁性,这与半导体的特性相符。掺杂锰原子后,掺杂体系具有磁性,磁矩主要由锰原子产生。在锰原子与卤素原子共掺杂后,掺杂体系的总磁矩减小。对电子结构的研究表明,锰原子的掺杂和锰原子与卤素原子的共掺杂导致在掺杂体系中引入了杂质能级,这些杂质能级只出现在自旋上升部分,不跨越费米能级。自旋上升能带和自旋下降能带之间不对称,掺杂体系表现出磁性半导体特性。卤原子的 p 轨道和锰原子的 3d 轨道的杂化是在掺杂体系能带中引入杂质能级的主要原因。在掺锰体系中,锰和硒之间形成了离子键。在共掺杂体系中,Mn 原子与 F、Cl 原子间形成了强离子键,Mn 原子与 Br、I 原子间形成了共价键。
{"title":"Electronic and magnetic properties of Mn-doped and Mn-X (F, Cl, Br, I) co-doped modulated monolayer SnSe2","authors":"Mengting Ma , Guili Liu , Guoying Zhang","doi":"10.1016/j.susc.2024.122511","DOIUrl":"10.1016/j.susc.2024.122511","url":null,"abstract":"<div><p>The density functional theory is employed for learning the modulation of the electronic structure and magnetic properties of monolayer SnSe<sub>2</sub> by an Mn atom and by co-doping an Mn atom with a halogen atom. It is found that intrinsic SnSe<sub>2</sub> is nonmagnetic, which is consistent with the properties of semiconductors. Following Mn atom doping, the doped system is magnetic and the magnetic moments are primarily responsible for the Mn atom. After co-doping the Mn atom with halogen atoms, the doped system's total magnetic moments are decreased. The examination of the electronic structure demonstrates that the doping of the Mn atom and the co-doping of the Mn atom with halogen atoms lead to the introduction of impurity energy levels into the doped system, which appear only in the spin-up part and do not cross the Fermi energy level. There is asymmetry between the spin-up and spin-down energy bands and the doped system exhibits magnetic semiconductor properties. The hybridization of the p-orbitals of the halogen atoms and the 3d orbitals of the Mn atom is primarily responsible for the introduction of impurity energy levels in the energy bands of the doped system. In the Mn-doped system, ionic bonds were shaped between Mn and Se. In the co-doped system, strong ionic bonds were shaped between the Mn atom and F, Cl atoms, and covalent bonds were shaped between the Mn atom and Br, I atoms.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141139228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-22DOI: 10.1016/j.susc.2024.122522
Dapeng Jing , Yong Han , Marek Kolmer , Michael C. Tringides , James W. Evans
Nucleation and growth of supported 3D metal clusters or crystallites during deposition on MoS2, or on other weakly-adhering layered materials, can potentially produce diverse growth shapes, and even crystal structures differing from the bulk metal. For Fe deposition on MoS2, SEM and AFM observations reveal three distinct crystallite shapes. By comparison with atomistic structure models incorporating realistic Fe-MoS2 interface structures, we conclude that these are: triangular fcc(111) pyramids with sloped {100} side facets; bcc(110) A-frame tents with sloped {100} side facets; and bcc(110) mesas with vertical {100} and {110} side facets. The following picture is proposed for the competitive formation of clusters and crystallites with different structures: (i) small nanoclusters formed at the onset of deposition exhibit facile fluxional dynamics allowing sampling of different crystal structures and shapes; (ii) sufficient fluxionality implies a Boltzmann distribution of sampled structures, and thus coexistence of different structures follows from the demonstrated similar energies for those structures; (iii) growing clusters reach a threshold size above which the characteristic time scale for restructuring exceeds that for cluster growth. Thereafter, clusters are locked-in to a specific crystal structure and shape as revealed by imaging of larger crystallites. Despite a penalty for fcc(111) over bcc(111) pyramids based on bulk energetics, favorable surface and interface energies makes them preferable for smaller sizes.
{"title":"Crystal structure and shape selection in the growth of 3D metallic crystallites on layered materials: Fe on MoS2","authors":"Dapeng Jing , Yong Han , Marek Kolmer , Michael C. Tringides , James W. Evans","doi":"10.1016/j.susc.2024.122522","DOIUrl":"10.1016/j.susc.2024.122522","url":null,"abstract":"<div><p>Nucleation and growth of supported 3D metal clusters or crystallites during deposition on MoS<sub>2</sub>, or on other weakly-adhering layered materials, can potentially produce diverse growth shapes, and even crystal structures differing from the bulk metal. For Fe deposition on MoS<sub>2</sub>, SEM and AFM observations reveal three distinct crystallite shapes. By comparison with atomistic structure models incorporating realistic Fe-MoS<sub>2</sub> interface structures, we conclude that these are: triangular fcc(111) pyramids with sloped {100} side facets; bcc(110) A-frame tents with sloped {100} side facets; and bcc(110) mesas with vertical {100} and {110} side facets. The following picture is proposed for the competitive formation of clusters and crystallites with different structures: (i) small nanoclusters formed at the onset of deposition exhibit facile fluxional dynamics allowing sampling of different crystal structures and shapes; (ii) sufficient fluxionality implies a Boltzmann distribution of sampled structures, and thus coexistence of different structures follows from the demonstrated similar energies for those structures; (iii) growing clusters reach a threshold size above which the characteristic time scale for restructuring exceeds that for cluster growth. Thereafter, clusters are locked-in to a specific crystal structure and shape as revealed by imaging of larger crystallites. Despite a penalty for fcc(111) over bcc(111) pyramids based on bulk energetics, favorable surface and interface energies makes them preferable for smaller sizes.</p></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141135275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}