Pub Date : 2024-12-12DOI: 10.1016/j.susc.2024.122678
Willem Vanmoerkerke, Rasmus Svensson, Henrik Grönbeck
Quantitative modeling of surface reactions relies on accurate potential energy surfaces that include adsorbate–adsorbate interactions. Using density functional theory calculations we introduce an efficient procedure to parameterize adsorbate–adsorbate interactions and present results for interactions between O2, O, OH and H2O on Pt, Ir, Rh and Pd surfaces. The targeted interactions are important when describing, for example, the electrochemical oxygen reduction reaction. However, an accurate representation of both non-directional interactions and directional hydrogen bonds remains challenging. By analyzing the dominant contributions, we find that accurate parameterizations can be constructed by separately considering surface mediated electronic interactions and pairwise hydrogen bonds. Two methods are evaluated to account for interactions beyond nearest-neighbors. Our work provides a general framework to analyze adsorbate–adsorbate interactions and present parameterizations suitable for efficient kinetic Monte Carlo simulations.
{"title":"Efficient parameterization of adsorbate–adsorbate interactions on metal surfaces","authors":"Willem Vanmoerkerke, Rasmus Svensson, Henrik Grönbeck","doi":"10.1016/j.susc.2024.122678","DOIUrl":"10.1016/j.susc.2024.122678","url":null,"abstract":"<div><div>Quantitative modeling of surface reactions relies on accurate potential energy surfaces that include adsorbate–adsorbate interactions. Using density functional theory calculations we introduce an efficient procedure to parameterize adsorbate–adsorbate interactions and present results for interactions between O<sub>2</sub>, O, OH and H<sub>2</sub>O on Pt, Ir, Rh and Pd surfaces. The targeted interactions are important when describing, for example, the electrochemical oxygen reduction reaction. However, an accurate representation of both non-directional interactions and directional hydrogen bonds remains challenging. By analyzing the dominant contributions, we find that accurate parameterizations can be constructed by separately considering surface mediated electronic interactions and pairwise hydrogen bonds. Two methods are evaluated to account for interactions beyond nearest-neighbors. Our work provides a general framework to analyze adsorbate–adsorbate interactions and present parameterizations suitable for efficient kinetic Monte Carlo simulations.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"754 ","pages":"Article 122678"},"PeriodicalIF":2.1,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143151032","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 : 2024-12-03DOI: 10.1016/j.susc.2024.122677
R. Jürgen Behm, Axel Groß
In this contribution, we will review the concepts and principles used to characterize and discuss the structure, stability, adsorption properties and catalytic reactivity of bimetallic surfaces in an atomic-scale picture. Starting from early stages, we will emphasize recent experimental and theoretical findings that resulted in a rapidly improving atomic-scale understanding of adsorption and catalytic surface reactions on these surfaces. While examples are often taken from our own work, the resulting insights are of general validity.
{"title":"The chemistry of bimetallic surfaces – Evolution of an atomic-scale picture","authors":"R. Jürgen Behm, Axel Groß","doi":"10.1016/j.susc.2024.122677","DOIUrl":"10.1016/j.susc.2024.122677","url":null,"abstract":"<div><div>In this contribution, we will review the concepts and principles used to characterize and discuss the structure, stability, adsorption properties and catalytic reactivity of bimetallic surfaces in an atomic-scale picture. Starting from early stages, we will emphasize recent experimental and theoretical findings that resulted in a rapidly improving atomic-scale understanding of adsorption and catalytic surface reactions on these surfaces. While examples are often taken from our own work, the resulting insights are of general validity.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"754 ","pages":"Article 122677"},"PeriodicalIF":2.1,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143151031","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 : 2024-12-01DOI: 10.1016/j.susc.2024.122669
Rabia Hassan , Rehan Hassan , Fei Ma
The slow oxygen evolution reaction (OER) in the water-splitting driven by electricity, significantly impedes the hydrogen evolution reaction (HER). In this paper, density functional theory with D3 correction (DFT-D3) is utilized to explore the electrocatalytic potential of defected mono-layered VSe2 for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Intrinsic point defects, such as, selenium (D1) and vanadium (D2) vacancies, are introduced into 2D-VSe2. Possible sites, like, Se Top, V Top, vacancies and bridge positions are investigated for OER and ORR intermediates (O, OH and OOH). VSe2 monolayer with V vacancy (D2) shows significantly reduced overpotential for OER/ORR (η= 0.19 V/0.46 V), indicating enhanced catalytic activity. The OER performances of VSe2 monolayer with V vacancy (D2) (η= 0.19 V) surpasses those of IrO2 and RuO2 (η= 0.37 V and 0.56 V), and the ORR performances (η= 0.46 V) are comparable to those of precious Pt (η=0.4 V). The Pourbaix diagram further confirms the aqueous stability of VSe2 in various pH environments, establishing its potential as a robust catalyst for OER and ORR. These findings suggest that defect engineering, particularly vanadium vacancies, could significantly improve the electrocatalytic activity of VSe2 monolayers, contributing to the development of high-performance electrocatalysts.
{"title":"Density functional theory study on the electrocatalytic performance of defected monolayer vanadium diselenide for oxygen evolution and reduction reactions","authors":"Rabia Hassan , Rehan Hassan , Fei Ma","doi":"10.1016/j.susc.2024.122669","DOIUrl":"10.1016/j.susc.2024.122669","url":null,"abstract":"<div><div>The slow oxygen evolution reaction (OER) in the water-splitting driven by electricity, significantly impedes the hydrogen evolution reaction (HER). In this paper, density functional theory with D3 correction (DFT-D3) is utilized to explore the electrocatalytic potential of defected mono-layered VSe<sub>2</sub> for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Intrinsic point defects, such as, selenium (D1) and vanadium (D2) vacancies, are introduced into 2D-VSe<sub>2</sub>. Possible sites, like, Se Top, V Top, vacancies and bridge positions are investigated for OER and ORR intermediates (O, OH and OOH). VSe<sub>2</sub> monolayer with V vacancy (D2) shows significantly reduced overpotential for OER/ORR (η= 0.19 V/0.46 V), indicating enhanced catalytic activity. The OER performances of VSe<sub>2</sub> monolayer with V vacancy (D2) (η= 0.19 V) surpasses those of IrO<sub>2</sub> and RuO<sub>2</sub> (η= 0.37 V and 0.56 V), and the ORR performances (η= 0.46 V) are comparable to those of precious Pt (η=0.4 V). The Pourbaix diagram further confirms the aqueous stability of VSe<sub>2</sub> in various pH environments, establishing its potential as a robust catalyst for OER and ORR. These findings suggest that defect engineering, particularly vanadium vacancies, could significantly improve the electrocatalytic activity of VSe<sub>2</sub> monolayers, contributing to the development of high-performance electrocatalysts.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"754 ","pages":"Article 122669"},"PeriodicalIF":2.1,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143150989","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 : 2024-11-28DOI: 10.1016/j.susc.2024.122668
Tinghui Li , Yun Shan , Lizhe Liu
Electrochemical conversion from nitrate to ammonia becomes a feasible technology to improve nitrate pollutants and realize room-temperature ammonia synthesis, but which is limited by multiple competing reaction and low energy conversion efficiency. Herein, we suggest dense and well-defined magnetic metal sites on the M(CN)3 (M = Fe, Co, Ni) surface with spontaneous hydroxyl decoration, which leads to electronic rearrangement at half-filled 3d orbitals due to its tailored coordination environment that optimizes nitrate adsorption and dissociation. The comprehensive calculations associated with density functional theory disclose that the rate-limiting potential barrier effectively reduces and finally leads to a higher nitrogen conversion ability, because the bonding interaction and electron transfer between metal sites and reactants is optimized by decorating hydroxyls. This work provides a new insight into understanding the reaction kinetics for nitrate reduction.
{"title":"Electronic reconfiguration induced by dynamic hydroxyl decoration facilitates electrochemical nitrate reduction to ammonia","authors":"Tinghui Li , Yun Shan , Lizhe Liu","doi":"10.1016/j.susc.2024.122668","DOIUrl":"10.1016/j.susc.2024.122668","url":null,"abstract":"<div><div>Electrochemical conversion from nitrate to ammonia becomes a feasible technology to improve nitrate pollutants and realize room-temperature ammonia synthesis, but which is limited by multiple competing reaction and low energy conversion efficiency. Herein, we suggest dense and well-defined magnetic metal sites on the M(CN)<sub>3</sub> (M = Fe, Co, Ni) surface with spontaneous hydroxyl decoration, which leads to electronic rearrangement at half-filled 3d orbitals due to its tailored coordination environment that optimizes nitrate adsorption and dissociation. The comprehensive calculations associated with density functional theory disclose that the rate-limiting potential barrier effectively reduces and finally leads to a higher nitrogen conversion ability, because the bonding interaction and electron transfer between metal sites and reactants is optimized by decorating hydroxyls. This work provides a new insight into understanding the reaction kinetics for nitrate reduction.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"753 ","pages":"Article 122668"},"PeriodicalIF":2.1,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748420","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 : 2024-11-23DOI: 10.1016/j.susc.2024.122654
Felipe Marinho Fernandes , Neubi Francisco Xavier Jr , Glauco Favilla Bauerfeldt , Márcio Soares Pereira , Clarissa Oliveira da Silva
The search for alternative energy sources with sustained economic viability and minimal pollution is imperative, making hydrogen a promising candidate as a fuel. This work provides important findings on the Oxygen Evolution Reactions (OER) on TiO2, with a focus on elucidating the reaction mechanisms. Density Functional Theory calculations were applied on both the (101) and (100) surfaces of the catalyst. The application of overpotentials was evaluated, with 2.85 and 2.32 eV required for (101) and (100) surface, respectively, for all reaction steps to be exergonic. The 0.53 eV difference suggests a potentially favorable pathway for the OER on the (100) surface. When evaluating the kinetics, an additional barrier of 2.84 eV under the V condition on the (100) surface is found for the formation of the OOH intermediate, suggesting the kinetics preference for the oxygen evolution process on the (101) surface.
{"title":"Thermodynamic and kinetic analysis of the oxygen evolution reaction on TiO2 (100) and (101) surfaces: A DFT study","authors":"Felipe Marinho Fernandes , Neubi Francisco Xavier Jr , Glauco Favilla Bauerfeldt , Márcio Soares Pereira , Clarissa Oliveira da Silva","doi":"10.1016/j.susc.2024.122654","DOIUrl":"10.1016/j.susc.2024.122654","url":null,"abstract":"<div><div>The search for alternative energy sources with sustained economic viability and minimal pollution is imperative, making hydrogen a promising candidate as a fuel. This work provides important findings on the Oxygen Evolution Reactions (OER) on TiO<sub>2</sub>, with a focus on elucidating the reaction mechanisms. Density Functional Theory calculations were applied on both the (101) and (100) surfaces of the catalyst. The application of overpotentials was evaluated, with 2.85 and 2.32 eV required for (101) and (100) surface, respectively, for all reaction steps to be exergonic. The 0.53 eV difference suggests a potentially favorable pathway for the OER on the (100) surface. When evaluating the kinetics, an additional barrier of 2.84 eV under the <span><math><mrow><mi>U</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>00</mn></mrow></math></span> V condition on the (100) surface is found for the formation of the OOH intermediate, suggesting the kinetics preference for the oxygen evolution process on the (101) surface.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"753 ","pages":"Article 122654"},"PeriodicalIF":2.1,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748419","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 : 2024-11-22DOI: 10.1016/j.susc.2024.122665
Konstantinos G. Papanikolaou , Lang Xu , Evangelos Smith , Manos Mavrikakis
The formation of nanoclusters on metal surfaces in the presence of reactive environments is a phenomenon with important implications for catalysis. These nanoclusters are composed of atoms ejected from undercoordinated sites such as step edges, and their presence alters the catalytic properties of solid materials. We perform density functional theory (DFT) and kinetic Monte Carlo (KMC) simulations to investigate the formation and reactivity of copper clusters on Cu(111). Our results indicate a considerably higher reactivity of small copper nanoclusters, with up to seven atoms in size on roughened copper surfaces than on pristine Cu(111) and Cu(211). Regarding the restructuring events that give rise to nanoclusters under CO atmospheres, we determine that the ejection of Cu atoms from step edges and their migration therefrom to adjacent Cu(111) terraces are, by and large, driven by CO coverage effects. By means of KMC simulations, which account for CO–CO lateral interactions and CO–induced surface restructuring, we show that temperature programmed desorption (TPD) holds promise for the detection of highly reactive nanoclusters. Our approach showcases how surface restructuring and surface–adsorbate bond breaking can be combined when modeling surface reactions and contributes to the development of an advanced understanding of the nature of active site under reaction conditions.
{"title":"CO–induced roughening of Cu(111): formation and detection of reactive nanoclusters on metal surfaces","authors":"Konstantinos G. Papanikolaou , Lang Xu , Evangelos Smith , Manos Mavrikakis","doi":"10.1016/j.susc.2024.122665","DOIUrl":"10.1016/j.susc.2024.122665","url":null,"abstract":"<div><div>The formation of nanoclusters on metal surfaces in the presence of reactive environments is a phenomenon with important implications for catalysis. These nanoclusters are composed of atoms ejected from undercoordinated sites such as step edges, and their presence alters the catalytic properties of solid materials. We perform density functional theory (DFT) and kinetic Monte Carlo (KMC) simulations to investigate the formation and reactivity of copper clusters on Cu(111). Our results indicate a considerably higher reactivity of small copper nanoclusters, with up to seven atoms in size on roughened copper surfaces than on pristine Cu(111) and Cu(211). Regarding the restructuring events that give rise to nanoclusters under CO atmospheres, we determine that the ejection of Cu atoms from step edges and their migration therefrom to adjacent Cu(111) terraces are, by and large, driven by CO coverage effects. By means of KMC simulations, which account for CO–CO lateral interactions and CO–induced surface restructuring, we show that temperature programmed desorption (TPD) holds promise for the detection of highly reactive nanoclusters. Our approach showcases how surface restructuring and surface–adsorbate bond breaking can be combined when modeling surface reactions and contributes to the development of an advanced understanding of the nature of active site under reaction conditions.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"754 ","pages":"Article 122665"},"PeriodicalIF":2.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143151722","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 : 2024-11-21DOI: 10.1016/j.susc.2024.122657
Hiroshi Kondoh
This minireview provides an overview of recent advancements in in situ/operando soft X-ray surface spectroscopy, particularly focusing on the development and application of techniques such as near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and soft X-ray absorption spectroscopy (SXAS) conducted at the Photon Factory. These techniques enable us to observe catalytic surfaces under working conditions, which provides new insights into catalytic mechanisms by probing the chemical states of reactive species as well as catalytic surfaces. The review highlights three case studies: the reduction of nitrogen oxide (NO) on rhodium (Rh) catalysts, ethylene epoxidation on silver (Ag) catalysts, and water-splitting photocatalysis using SrTiO3 with co-catalysts. Each study shows how these techniques reveal critical aspects about surface reactions, structures of intermediate species, and photoinduced processes, which contributes to a deeper understanding of reactive species and reaction pathways. I also discuss about the challenges in operando kinetic analyses, structure analyses and extension of applicable catalytic phenomena and suggest future improvements in operando spectroscopy to enhance the capability of these analyses.
本微型视图概述了原位/操作软 X 射线表面光谱学的最新进展,尤其侧重于光子工厂开展的近环境压力 X 射线光电子能谱(NAP-XPS)和软 X 射线吸收光谱(SXAS)等技术的开发和应用。这些技术使我们能够观察工作条件下的催化表面,通过探测反应物和催化表面的化学状态,为催化机制提供新的见解。综述重点介绍了三个案例研究:铑(Rh)催化剂的氧化氮(NO)还原、银(Ag)催化剂的乙烯环氧化以及使用 SrTiO3 与助催化剂的水分离光催化。每项研究都展示了这些技术如何揭示表面反应、中间物种结构和光诱导过程的关键方面,从而有助于加深对反应物种和反应途径的理解。我还讨论了在操作动力学分析、结构分析和适用催化现象的扩展方面所面临的挑战,并提出了操作光谱学的未来改进建议,以提高这些分析的能力。
{"title":"Surface science study on catalytic surfaces under working conditions with soft-X-ray surface spectroscopy at the Photon Factory","authors":"Hiroshi Kondoh","doi":"10.1016/j.susc.2024.122657","DOIUrl":"10.1016/j.susc.2024.122657","url":null,"abstract":"<div><div>This minireview provides an overview of recent advancements in <em>in situ/operando</em> soft X-ray surface spectroscopy, particularly focusing on the development and application of techniques such as near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and soft X-ray absorption spectroscopy (SXAS) conducted at the Photon Factory. These techniques enable us to observe catalytic surfaces under working conditions, which provides new insights into catalytic mechanisms by probing the chemical states of reactive species as well as catalytic surfaces. The review highlights three case studies: the reduction of nitrogen oxide (NO) on rhodium (Rh) catalysts, ethylene epoxidation on silver (Ag) catalysts, and water-splitting photocatalysis using SrTiO<sub>3</sub> with co-catalysts. Each study shows how these techniques reveal critical aspects about surface reactions, structures of intermediate species, and photoinduced processes, which contributes to a deeper understanding of reactive species and reaction pathways. I also discuss about the challenges in <em>operando</em> kinetic analyses, structure analyses and extension of applicable catalytic phenomena and suggest future improvements in <em>operando</em> spectroscopy to enhance the capability of these analyses.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"753 ","pages":"Article 122657"},"PeriodicalIF":2.1,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722420","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 : 2024-11-20DOI: 10.1016/j.susc.2024.122656
Rosemary Jones , Esko Kokkonen , Calley Eads , Ulrike K. Küst , Julia Prumbs , Jan Knudsen , Joachim Schnadt
Today, atomic layer deposition (ALD) has become a firm corner stone of thin film deposition technology. The microelectronics industry, an early adopter of ALD, imposes stringent requirements on ALD to produce films with highly defined physical and chemical properties, which becomes even more important as device and component dimensions decrease. This, in turn, means that our understanding of the chemical processes underlying ALD needs to increase exponentially. Here, we show that one can use synchrotron-based time-resolved ambient pressure x-ray photoelectron spectroscopy (APXPS) to obtain highly detailed operando information on the surface chemistry of ALD, not only, as proven earlier, during the initial ALD cycles, but also for the steady-growth regime reached during the later stages of deposition. Using event averaging and Fourier-transform methods, we show that the ALD of TiO2 from titanium tetraisopropoxide (TTIP) and water precursors in the steady-growth regime follows the suggested ligand-exchange reaction mechanism, with no sign of oxygen transport between the deposited layers and the bulk of the film, as has been observed for other materials systems. Hence, the TiO2 ALD from TTIP and water constitutes a textbook example of metal oxide ALD, as expected for this well-known ALD process. The detailed insight is made possible by computerised control of the precursor pulses that enable the recording of long data sets, which comprise many ALD cycles at highly regular intervals, in combination with an advanced data analysis that allows us to pick out signals undetectable in the raw data. The analysis method also allows to separate oscillating contributions to the signals induced by the ALD pulsing from the overwhelming bulk signal.
{"title":"Time-resolved ambient pressure x-ray photoelectron spectroscopy: Advancing the operando study of ALD chemistry","authors":"Rosemary Jones , Esko Kokkonen , Calley Eads , Ulrike K. Küst , Julia Prumbs , Jan Knudsen , Joachim Schnadt","doi":"10.1016/j.susc.2024.122656","DOIUrl":"10.1016/j.susc.2024.122656","url":null,"abstract":"<div><div>Today, atomic layer deposition (ALD) has become a firm corner stone of thin film deposition technology. The microelectronics industry, an early adopter of ALD, imposes stringent requirements on ALD to produce films with highly defined physical and chemical properties, which becomes even more important as device and component dimensions decrease. This, in turn, means that our understanding of the chemical processes underlying ALD needs to increase exponentially. Here, we show that one can use synchrotron-based time-resolved ambient pressure x-ray photoelectron spectroscopy (APXPS) to obtain highly detailed <em>operando</em> information on the surface chemistry of ALD, not only, as proven earlier, during the initial ALD cycles, but also for the steady-growth regime reached during the later stages of deposition. Using event averaging and Fourier-transform methods, we show that the ALD of TiO<sub>2</sub> from titanium tetraisopropoxide (TTIP) and water precursors in the steady-growth regime follows the suggested ligand-exchange reaction mechanism, with no sign of oxygen transport between the deposited layers and the bulk of the film, as has been observed for other materials systems. Hence, the TiO<sub>2</sub> ALD from TTIP and water constitutes a textbook example of metal oxide ALD, as expected for this well-known ALD process. The detailed insight is made possible by computerised control of the precursor pulses that enable the recording of long data sets, which comprise many ALD cycles at highly regular intervals, in combination with an advanced data analysis that allows us to pick out signals undetectable in the raw data. The analysis method also allows to separate oscillating contributions to the signals induced by the ALD pulsing from the overwhelming bulk signal.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"753 ","pages":"Article 122656"},"PeriodicalIF":2.1,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748421","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}
Enhancing SiN deposition, particularly using NH₃ in atomic layer and chemical vapor deposition, is crucial for improving the performance of Si-based devices. However, while NH₃ nitridation on clean Si surfaces is well understood, its behavior on Cl-terminated Si surfaces remains largely unexplored. In this study, the mechanism of NH3 nitridation on Cl-terminated Si(100)-2 × 1 surfaces is investigated using first-principles calculations and thermodynamic analysis. NH3 reacts with Si–Cl on the surface with low reaction barriers, generating Si–NH2 and gaseous HCl. Subsequently, Si–NH2 forms a Si–NH–Si structure via NH2 insertion into the Si–Si dimer bond and H migration onto the Si-dangling bond. Si–NH–Si formation is more favorable on the Si–Si dimer bond than on the Si–Si back bond. Thermodynamic analyses indicate that NH3 nitridation leads to the Si–NH–Si structure, as Si–NH–Si formation is more thermodynamically stable than Si–NH2 formation. Moreover, it is confirmed that the Si–NH–Si formation reaction is more favorable at higher temperatures and NH3 partial pressures. These findings could potentially be used to improve SiN deposition processes and enhance the performance of Si-based devices.
{"title":"Theoretical investigation of NH3 nitridation on Cl-terminated Si(100)-2 × 1 surfaces","authors":"Tomoya Nagahashi , Hajime Karasawa , Ryota Horiike , Kenji Shiraishi","doi":"10.1016/j.susc.2024.122655","DOIUrl":"10.1016/j.susc.2024.122655","url":null,"abstract":"<div><div>Enhancing SiN deposition, particularly using NH₃ in atomic layer and chemical vapor deposition, is crucial for improving the performance of Si-based devices. However, while NH₃ nitridation on clean Si surfaces is well understood, its behavior on Cl-terminated Si surfaces remains largely unexplored. In this study, the mechanism of NH<sub>3</sub> nitridation on Cl-terminated Si(100)-2 × 1 surfaces is investigated using first-principles calculations and thermodynamic analysis. NH<sub>3</sub> reacts with Si–Cl on the surface with low reaction barriers, generating Si–NH<sub>2</sub> and gaseous HCl. Subsequently, Si–NH<sub>2</sub> forms a Si–NH–Si structure via NH<sub>2</sub> insertion into the Si–Si dimer bond and H migration onto the Si-dangling bond. Si–NH–Si formation is more favorable on the Si–Si dimer bond than on the Si–Si back bond. Thermodynamic analyses indicate that NH<sub>3</sub> nitridation leads to the Si–NH–Si structure, as Si–NH–Si formation is more thermodynamically stable than Si–NH<sub>2</sub> formation. Moreover, it is confirmed that the Si–NH–Si formation reaction is more favorable at higher temperatures and NH<sub>3</sub> partial pressures. These findings could potentially be used to improve SiN deposition processes and enhance the performance of Si-based devices.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"753 ","pages":"Article 122655"},"PeriodicalIF":2.1,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142721968","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 : 2024-11-18DOI: 10.1016/j.susc.2024.122653
Alexandre Pancotti , Diogo Duarte dos Reis , Jerzy T. Sadowski , Alex Sandre Kilian , John Boeckl , Patrick Soukiassian , Christophe Lubin , Ludovic Douillard , Nick Barrett , Tyson Back
We have studied the surface structure of a single crystal β-Ga2O3(010) using quantitative Low Energy Electron Diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). The XPS measurements show spectra typical of stoichiometric Ga2O3 with a clean surface. LEED consistently shows a p(1×1) pattern, free of surface reconstruction. Quantitative LEED I(V) curves are acquired for 41 distinct diffraction spots. The experimental I(V) curves are compared to simulations over the first five layers. The best fits to the experimental LEED I(V) curves acquired at all diffraction spots are then used to calculate the interplanar relaxation and atomic rumpling. Significant atomic rumpling and interplanar relaxation are found over the first 5 atomic layers. As a result of rumpling a polarization of ∼ 2 µC/cm2 develops in the topmost surface layer. The structural results are in good agreement with previous density functional theory calculations and experimental X-ray photoelectron diffraction.
{"title":"Surface structure of Sn doped β-Ga2O3(010) p(1×1) studied by quantitative low energy electron diffraction","authors":"Alexandre Pancotti , Diogo Duarte dos Reis , Jerzy T. Sadowski , Alex Sandre Kilian , John Boeckl , Patrick Soukiassian , Christophe Lubin , Ludovic Douillard , Nick Barrett , Tyson Back","doi":"10.1016/j.susc.2024.122653","DOIUrl":"10.1016/j.susc.2024.122653","url":null,"abstract":"<div><div>We have studied the surface structure of a single crystal β-Ga<sub>2</sub>O<sub>3</sub>(010) using quantitative Low Energy Electron Diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). The XPS measurements show spectra typical of stoichiometric Ga<sub>2</sub>O<sub>3</sub> with a clean surface. LEED consistently shows a p(1×1) pattern, free of surface reconstruction. Quantitative LEED I(V) curves are acquired for 41 distinct diffraction spots. The experimental I(V) curves are compared to simulations over the first five layers. The best fits to the experimental LEED I(V) curves acquired at all diffraction spots are then used to calculate the interplanar relaxation and atomic rumpling. Significant atomic rumpling and interplanar relaxation are found over the first 5 atomic layers. As a result of rumpling a polarization of ∼ 2 µC/cm<sup>2</sup> develops in the topmost surface layer. The structural results are in good agreement with previous density functional theory calculations and experimental X-ray photoelectron diffraction.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"753 ","pages":"Article 122653"},"PeriodicalIF":2.1,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748418","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}