Article
Chemistry, Multidisciplinary
Junxi Yu, Rajiv Giridharagopal, Yuhao Li, Kaichen Xie, Jiangyu Li, Ting Cao, Xiaodong Xu, David S. Ginger
Summary: By studying graphene with ABAB and ABCA stacking, it was found that the surface potential of ABCA regions is approximately 15 mV higher than that of ABAB regions, due to stacking-dependent electronic structure. The moire superlattice visualized by LPFM can change with time, while imaging the surface potential distribution via SKPM appears more stable for mapping ABAB and ABCA regions.
Article
Nanoscience & Nanotechnology
Hesham El-Sherif, Natalie Briggs, Brian Bersch, Minghao Pan, Mahdi Hamidinejad, Siavash Rajabpour, Tobin Filleter, Ki Wook Kim, Joshua Robinson, Nabil D. Bassim
Summary: In this study, the thickness of 2D-Ga heterostructures was resolved and measured using scanning electron microscopy (SEM), with the SEM image contrast directly related to the presence of uniform bilayer Ga at the interface and variation of graphene layers. By utilizing multiple correlative methods, the researchers investigated the origin of SEM contrast and found that a carbon buffer layer detached due to gallium intercalation, increasing the surface potential as an indication of the 2D-Ga presence. The study also successfully scaled up heterostructure characterization over a few-square millimeter area by segmenting SEM images with nanometer-scale in-plane resolution, leveraging the spectroscopic imaging capabilities of SEM for tracking intercalants, identifying relative surface potentials, determining the number of 2D layers, and further characterizing scalability and uniformity of low-dimensional materials.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Physical
Hwi Je Woo, Seongchan Kim, Young-Jin Choi, Jeong Ho Cho, Seong Heon Kim, Young Jae Song
Summary: The work function of graphene devices on SiO2 substrates is studied using Kelvin probe force microscopy, revealing gate voltage-dependent work-function hysteresis. The inhomogeneous distribution of chemical species at the graphene/SiO2 interface leads to varying degrees of hysteresis across different positions on the graphene.
Article
Chemistry, Physical
Sanjeev Kumar, J. Shakya, T. Mahanta, D. Kanjilal, T. Mohanty
Summary: This study investigates the effects of swift heavy ion irradiation on the optical and surface electronic properties of chemical vapor deposited (CVD) graphene sheets. The results show that the sputtered substrate atoms become trapped in the graphene sheet and alter its Fermi level, as confirmed by Raman spectroscopy and scanning Kelvin probe microscopy. Monte Carlo simulations using SRIM and TRIM packages further study the mechanism of ion interaction and its effects on graphene and substrate materials.
SURFACES AND INTERFACES
(2022)
Article
Energy & Fuels
Christian Kameni Boumenou, Amala Elizabeth, Finn Babbe, Alice Debot, Harry Moeenig, Alex Redinger
Summary: The study investigated the buried MoSe2/CuInSe2 interface of stoichiometric absorbers in thin film solar cells, revealing differences in local density of states compared to the front-side properties. This sheds new light on the complex interface formation in CuInSe2-based thin film solar cells grown under Cu-rich conditions.
PROGRESS IN PHOTOVOLTAICS
(2021)
Article
Chemistry, Multidisciplinary
Shangzhi Gu, Wenyu Liu, Shuo Mi, Guoyu Xian, Jiangfeng Guo, Fei Pang, Shanshan Chen, Haitao Yang, Hong-Jun Gao, Zhihai Cheng
Summary: In this study, the twist angle-dependent work functions of twisted bilayer graphene (tBLG) were investigated using Kelvin probe force microscopy (KPFM) and Raman spectroscopy. The surface potentials of Bernal-stacked multilayer graphene were measured to determine the relationship between twist angle and surface potential. It was found that the work function of tBLG decreases and tends to saturate with increasing number of layers. Controlled annealing process showed that tBLG transforms into Bernal-stacked bilayer graphene. This research provides valuable insights into the twist angle-dependent surface potentials and electronic properties of tBLG.
Article
Anatomy & Morphology
Joel Ndikumana, Kunsik An
Summary: We performed local surface potential mapping of pentacene film using scanning kelvin probe microscopy and found that grain boundaries behave as hole traps.
MICROSCOPY RESEARCH AND TECHNIQUE
(2023)
Article
Chemistry, Multidisciplinary
Linghao Yan, Orlando J. Silveira, Benjamin Alldritt, Ondrej Krejci, Adam S. Foster, Peter Liljeroth
Summary: The successful fabrication of a 2D monolayer Cu-dicyanoanthracene MOF on an epitaxial graphene surface with long-range order and the study of its structural and electronic properties using low-temperature scanning tunneling microscopy and spectroscopy, along with density-functional theory calculations, show promise for future applications in electronic devices. The ability to access multiple molecular charge states in the 2D MOF using tip-induced local electric fields suggests potential for fabricating and characterizing 2D MOFs with engineered electronic states.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Yohan Kim, Huijun Han, Da Luo, Rodney S. Ruoff, Hyung-Joon Shin
Summary: The structural and electronic properties of graphene grown on catalytic metal surfaces are significantly modified due to the interaction between graphene and the substrate. To minimize the influence of the metal substrate, NaCl thin films can be introduced as intercalation layers to decouple graphene from the metal substrate, resulting in quasi-freestanding graphene.
Article
Chemistry, Multidisciplinary
Sayanti Samaddar, Jeff Strasdas, Kevin Janssen, Sven Just, Tjorven Johnsen, Zhenxing Wang, Burkay Uzlu, Sha Li, Daniel Neumaier, Marcus Liebmann, Markus Morgenstern
Summary: By studying the current-induced surface potential maps of graphene field-effect transistors, it was discovered that electron-electron scattering dominates in certain areas, exhibiting viscous flow phenomena, even at moderate mobility.
Article
Materials Science, Multidisciplinary
Zhaoxiang Ma, Lin Chen, Zhongli Liu, Yumin Wang, Kunjun Zhu, Yanjing Su
Summary: The behavior of dislocation migration hydrogen was observed through scanning Kelvin probe force microscopy (SKPFM) technique and slow tensile test. The quantitative analysis revealed that dislocation transport of hydrogen did not accelerate hydrogen atom migration, but achieved the uphill transport of hydrogen atoms. In addition, SKPFM has been confirmed as a powerful tool for measuring hydrogen diffusion coefficient in materials with high accuracy.
Article
Chemistry, Physical
Patrick Gruenewald, Niclas Hautz, Christian Motz
Summary: A full understanding of hydrogen embrittlement mechanisms requires knowledge of local hydrogen distribution. Grain boundaries are one of the microstructural features where hydrogen segregates, leading to a transition from transgranular to intergranular fracture. The type of grain boundary affects the segregated hydrogen and its diffusion rates. Scanning Kelvin Probe Force Microscopy (SKPFM) is a tool that can qualitatively measure local hydrogen contents, and potentially quantitatively in the future. This study uses SKPFM to detect hydrogen at grain boundaries in situ in a permeation setup, and investigates the influence of operation mode and atmosphere on the Contact Potential Difference V-CPD.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Chemistry, Physical
E. H. Lock, J. C. Prestigiacomo, P. Dev, A. Nath, R. L. Myers-Ward, T. L. Reinecke, D. K. Gaskill, M. S. Osofsky
Summary: Graphene, as the first isolated two-dimensional material, possesses unique properties that have captivated researchers for the last decade, including large electronic mobilities and tunable electrical properties via electrostatic gating. Functionalization of graphene, both covalent and non-covalent, leads to enhanced mobilities and the observation of quantum transport phenomena previously unseen in unfunctionalized graphene.
Article
Chemistry, Multidisciplinary
Remy Pawlak, Xunshan Liu, Silviya Ninova, Philipp D'Astolfo, Carl Drechsel, Jung-Ching Liu, Robert Haner, Silvio Decurtins, Ulrich Aschauer, Shi-Xia Liu, Ernst Meyer
Summary: In this study, a substrate-assisted reaction on Ag(111) was used to synthesize two-dimensional graphene sheets with a long-range honeycomb Kagome lattice. Low-temperature scanning tunneling microscopy and atomic force microscopy, supported by density functional theory, were employed to scrutinize the structural and electronic properties of N-KG down to the atomic scale. The research demonstrated the semiconducting character of N-KG due to nitrogen doping, as well as the emergence of Kagome flat bands near the Fermi level.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2021)
Article
Engineering, Chemical
Lei Zhan, Yitian Peng, Yao Huang, Kun Zou
Summary: In this study, the friction properties of graphene as a solid lubricant in micro-/nano-electromechanical system components were investigated using atomic force microscopy. It was found that the friction coefficient of graphene changed from positive to negative during the unloading process on different thicknesses of graphene. The turning point of friction coefficient was not affected by the unloading range but increased with the thickness of graphene. Different stick-slip behaviors were observed, indicating that the out-of-plane deformation of graphene is the main reason for these frictional characteristics. The anomalous friction at the contact interface between the microsphere probe and graphene expands the understanding of the frictional properties of graphene.
Article
Chemistry, Analytical
Chi Xiao, Jens Eriksson, Anke Suska, Daniel Filippini, Wing Cheung Mak
Summary: This study presents the design, fabrication, and testing of a smartphone iSPR system integrated with a 3D-printed microfluidic SPR chip. The system demonstrates high resistance to leakages and linear response to 02-microglobulin with a limit of detection of 1.5 nM. The miniaturized and simplified design makes it a promising platform for point-of-use applications.
ANALYTICA CHIMICA ACTA
(2022)
Article
Materials Science, Multidisciplinary
Nikola Koutna, Lukas Loefler, David Holec, Zhuo Chen, Zaoli Zhang, Lars Hultman, Paul H. Mayrhofer, Davide G. Sangiovanni
Summary: This study investigates the plasticity and crack growth mechanisms of B1 AlN(001)/TiN(001) superlattices under mechanical loading. The simulations reveal an anisotropic response of the superlattice in different tensile directions and suggest that controlling the thicknesses of the superlattice components can hinder crack growth.
Article
Materials Science, Multidisciplinary
A. V. Pshyk, A. Vasylenko, B. Bakhit, L. Hultman, P. Schweizer, T. E. J. Edwards, J. Michler, G. Greczynski
Summary: This study systematically investigates the effects of alloying equimolar high-entropy nitride thin films with aluminum. The results demonstrate that the aluminum concentration in the films determines their hardness, yield strength, toughness, and ability to deform plastically.
MATERIALS & DESIGN
(2022)
Editorial Material
Materials Science, Multidisciplinary
O. B. Malyshev, P. H. Mayrhofer, L. G. Hultman, P. Eklund, L. Sabbatini
Article
Chemistry, Physical
Babak Bakhit, Samira Dorri, Ali Kosari, Arjan Mol, Ivan Petrov, Jens Birch, Lars Hultman, Grzegorz Greczynski
Summary: In this study, Zr1-xCrxBy coatings were deposited using hybrid high power impulse/DC magnetron sputtering. The microstructure, mechanical properties, and corrosion resistance of these coatings were investigated. It was found that the dense films can be achieved by controlling the ratio of Cr+-dominated ion flux and (Zr + B) neutral flux. The alloys were categorized into two groups based on the Cr+/(Zr + B) ratios, and the films with higher Cr+/(Zr + B) ratios exhibited smoother surfaces and denser microstructure. The pulsed metal-ion irradiation was more effective in film densification compared to continuous Ar+ bombardment. These coatings showed high hardness, low stress, and low corrosion rates.
APPLIED SURFACE SCIENCE
(2022)
Article
Physics, Applied
Grzegorz Greczynski, Lars Hultman
Summary: There is a growing concern within the surface science community regarding the decline in work quality and meaningless chemical bond assignment in XPS articles. This trend could have disastrous consequences for scientific research. To address this, a comprehensive tutorial is offered, providing a step-by-step guide for experimental planning, data acquisition, spectra analysis, and results presentation, with a focus on improving the quality and reliability of XPS data analysis. The tutorial aims to broaden the application of XPS and enhance practitioners' ability to draw meaningful insights from XPS analysis.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Samira Dorri, Justinas Palisaitis, Grzegorz Greczynski, Ivan Petrov, Jens Birch, Lars Hultman, Babak Bakhit
Summary: We studied the oxidation properties of sputter-deposited TiB2.5 coatings at different temperatures. The results showed that at 600 degrees Celsius, the coating exhibited protective oxidation behavior, and the structure of the oxide layer also changed. Moreover, decreasing the heating rate had a noticeable impact on the oxidation process.
Article
Materials Science, Multidisciplinary
G. Greczynski, L. Hultman
Summary: This study investigates the effects of sample storage environment on the contamination of surfaces for XPS studies. Modeling techniques were used to analyze the types and quantities of surface contaminants under different storage conditions.
Editorial Material
Chemistry, Multidisciplinary
Raffaella Lo Nigro, Patrick Fiorenza, Bela Pecz, Jens Eriksson
Article
Chemistry, Physical
G. Greczynski, L. Hultman
Summary: The peak position of C 1s can be affected by the vacuum level alignment and differential charging. However, recent studies suggest that differential charging may not be the general cause of C 1s peak shifts. Experimental results confirm that the binding energy of C 1s peaks in metal foils is determined by their work function values.
APPLIED SURFACE SCIENCE
(2022)
Article
Materials Science, Coatings & Films
Xiao Li, Ivan Petrov, Lars Hultman, Grzegorz Greczynski
Summary: Hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) with synchronized substrate bias can reduce energy consumption and enable coatings on temperature-sensitive substrates. Direct evidence shows that W+ ion irradiation plays a crucial role in the densification of Ti0.31Al0.60W0.09N films.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Biographical-Item
Materials Science, Multidisciplinary
Ivan Petrov, Patrick Desjardins, Lars Hultman
Article
Physics, Applied
G. Greczynski, L. Hultman, I. Petrov
Summary: The quest for reducing energy consumption during thin film growth is important for sustainable development goals. Metal ion irradiation has been shown to be effective in densifying films grown without external heating. This Perspective provides an overview of the novel film growth method and discusses the role of metal ion mass, energy, momentum, and concentration.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Coatings & Films
Vladyslav Rogoz, Oleksandr Pshyk, Bartosz Wicher, Justinas Palisaitis, Jun Lu, Daniel Primetzhofer, Ivan Petrov, Lars Hultman, Grzegorz Greczynski
Summary: The traditional method for synthesizing high-entropy sublattice nitride (HESN) coatings is expensive and inflexible. This study demonstrates a new approach to grow HESN films using rotating substrates and elemental targets arranged in a multicathode configuration, which reduces costs and achieves compositional uniformity.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Multidisciplinary Sciences
Grzegorz Greczynski, Oleksandr Pshyk, Lars Hultman
Summary: X-ray photoelectron spectroscopy (XPS) spectra of solid samples are usually referenced to the spectrometer Fermi level (FL). However, for insulating samples, this method is not feasible. By depositing insulating amorphous alumina films on conducting substrates, it is found that the alumina energy levels align with the vacuum level, providing a solution to the binding energy reference problem for reliable assessment of chemical bonding.
