Article
Chemistry, Multidisciplinary
Umberto Celano, Hai Zhong, Florin Ciubotaru, Laurentiu Stoleriu, Alexander Stark, Peter Rickhaus, Felipe Favaro de Oliveira, Mathieu Munsch, Paola Favia, Maxim Korytov, Patricia Van Marcke, Patrick Maletinsky, Christoph Adelmann, Paul van der Heide
Summary: In this study, nonperturbative field distribution mapping in ultra-scaled magnetic nanowires with diameters down to 6 nm was achieved using scanning nitrogen-vacancy magnetometry, enabling localized, minimally invasive magnetic imaging with sensitivity down to 3 μT Hz(-1/2). The imaging revealed the presence of weak magnetic inhomogeneities inside in-plane magnetized nanowires, largely undetectable with standard metrology. The strong magnetic field confinement in the nanowires allowed for the study of the interaction between the stray magnetic field and the nitrogen-vacancy sensor, clarifying the formation mechanisms for technologically relevant magnetic nanostructures.
Article
Materials Science, Multidisciplinary
Jerzy Dryzek, Miroslaw Wrobel
Summary: The study found that with increasing annealing temperature, recrystallization of rolled molybdenum sheets occurred along with changes in positron annihilation characteristics. Dislocations and divacancies were observed through positron lifetime spectrum after deformation, while clusters with five vacancies were detected with the start of the recovery process of the deformed material above 200 degrees C. The step-like dependence of mean positron lifetime on temperature above 500 degrees C indicated recrystallization, which was confirmed by XRD measurements.
INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS
(2021)
Review
Materials Science, Ceramics
Vitaly Gurylev, Tsong Pyng Perng
Summary: Defects in zinc oxide (ZnO) play a crucial role in influencing its properties and applications, with potential for improved characteristics through the introduction of oxygen and zinc vacancies. Defective ZnO shows broad application potential in nanoscale devices, yet faces challenges and requires further research for in-depth exploration.
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
(2021)
Article
Electrochemistry
Shaona Chen, Zhangyu Zhou, Binbin Bai, Zhongxu Dai, Jinjin Shi
Summary: A novel heterojunction material with nonuniform charge distribution of rich S and O vacancies was prepared as an excellent electrocatalyst for NRR, showing significantly improved performance by simultaneously improving sulfur and oxygen vacancies on the heterojunction material.
Article
Materials Science, Multidisciplinary
Lukas Razinkovas, Marek Maciaszek, Friedemann Reinhard, Marcus W. Doherty, Audrius Alkauskas
Summary: The study conducted ab initio calculations on the photoionization characteristics of the NV center in diamond, revealing the mechanism of spin polarization induced electron state transition. These findings are crucial for interpreting and designing experiments on photoionization of NV centers.
Article
Physics, Multidisciplinary
M. Perdriat, P. Huillery, C. Pellet-Mary, G. Hetet
Summary: This study predicts and reports the strong diamagnetism of nanodiamonds with embedded NV centers. The ability to control the magnetic susceptibility and crystalline axis direction shows promising potential for various applications.
PHYSICAL REVIEW LETTERS
(2022)
Article
Optics
Zhonghao Li, Yanling Liang, Chong Shen, Zhenrong Shi, Huanfei Wen, Hao Guo, Zongmin Ma, Jun Tang, Jun Liu
Summary: In this study, wide-field tomography imaging of double circuits was performed using nitrogen-vacancy (NV) center ensembles in a diamond. By employing an inversion model and vector magnetic superposition, the magnetic-field distribution on the surface of the lower layer circuit was obtained. The results provide a simple and highly accurate reference for the detection and fault diagnosis of multilayer and integrated circuits.
Article
Chemistry, Multidisciplinary
Yu-Qi Zhou, Lifu Zhang, Hong-Li Suo, Weibo Hua, Sylvio Indris, Yaojie Lei, Wei-Hong Lai, Yun-Xiao Wang, Zhenpeng Hu, Hua-Kun Liu, Shu-Lei Chou, Shi-Xue Dou
Summary: Vacancies on a surface can enhance catalytic activity for hydrogen and oxygen evolution by altering the local electronic structure. Tuning cobalt vacancies to form clusters can increase the d-band level, improve electronic conductivity, and enhance adsorption, leading to highly efficient and stable water splitting reactions with low overpotentials in both acidic and alkaline environments.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Energy & Fuels
Hao Chen, Haishuai Cui, Yang Lv, Pingle Liu, Fang Hao, Wei Xiong, He'an Luo
Summary: Cu/ZnO/ZrO2 catalysts with different ZnO morphologies were prepared and used for CO2 hydrogenation to methanol. The catalyst with flower-like ZnO morphology showed the highest catalytic performance and possess the most oxygen vacancies. The experimental results and DFT calculations suggest that oxygen vacancies play a crucial role in promoting the reaction and reducing the energy barriers.
Article
Optics
Shao-Chun Zhang, Hao-Bin Lin, Yang Dong, Bo Du, Xue-Dong Gao, Cui Yu, Zhi-Hong Feng, Xiang-Dong Chen, Guang-Can Guo, Fang-Wen Sun
Summary: Fiber-based quantum magnetometers are highly sensitive and have wide bandwidth, making them suitable for mapping magnetic fields from different materials and structures. The addition of a silver reflective film improves the sensitivity and bandwidth of the magnetometer.
PHOTONICS RESEARCH
(2022)
Article
Physics, Applied
P. Raecke, L. Pietzonka, J. Meijer, D. Spemann, R. Wunderlich
Summary: NV centers in diamond were engineered by introducing vacancies locally through argon ion implantation in type Ib diamond with subsequent annealing. The number of NV centers created from vacancies of a single implanted argon ion ranges from 0.04 to 0.79 depending on the ion energy. The diffusion of vacancies during annealing plays a significant role in NV yield behavior.
APPLIED PHYSICS LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Chen Qiu, Hui-Xiong Deng, Songyuan Geng, Su-Huai Wei
Summary: Color centers in diamonds, specifically the XV centers, have shown promise for quantum information and computing applications. However, the abnormal trends in their zero-phonon line (ZPL) and local structure are not well understood. Through density-functional theory calculations and symmetry analysis, we find that the large size of X atoms and a competition between p-p coupling and p-d coupling contribute to these abnormal trends.
Article
Physics, Applied
P. Kehayias, E. Levine, L. Basso, J. Henshaw, M. Saleh Ziabari, M. Titze, R. Haltli, J. Okoro, D. R. Tibbetts, D. M. Udoni, E. Bielejec, M. P. Lilly, T-M Lu, P. D. D. Schwindt, A. M. Mounce
Summary: This paper explores the quantum diamond microscope (QDM) magnetic field imaging technique and uses a 555 timer IC as a model system to validate and optimize QDM measurements. The study confirms the consistency between measured and simulated magnetic field images, identifies the magnetic signatures of current paths within the device, and discusses the potential of QDM magnetic imaging as an IC diagnostic tool.
PHYSICAL REVIEW APPLIED
(2022)
Article
Physics, Applied
J. Christinck, F. Hirt, H. Hofer, Z. Liu, M. Etzkorn, T. Dunatov, M. Jaksic, J. Forneris, S. Kueck
Summary: We characterized the emission from a germanium-vacancy center in diamond using a microfabricated solid immersion lens in a confocal laser-scanning microscope setup. The photoluminescence was analyzed in terms of spectral distribution, excited state lifetime, second-order correlation function, and saturation behavior. Residual multi-photon probability was reduced using spectral and temporal filtering. System efficiency of the single-photon source was investigated and found to be consistent with calculated values. The results enable the future usage of the single-photon source in quantum radiometric experiments.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Physical
Jiangwei Chang, Chang Yu, Xuedan Song, Yiwang Ding, Siyi Hou, Shaofeng Li, Zongbin Zhao, Jieshan Qiu
Summary: This study presents an in situ framework reconstruction of g-C3N4 to achieve super nitrogen-doping, enhancing the catalytic activity of carbon materials. The results show the formation of nitrogen-doped graphene nanoribbons using ethene molecules as building blocks, with the nitrogen-doping level and configuration tunable. Using these super nitrogen-doped graphene nanoribbons as counter electrodes in dye-sensitized solar cells, a power conversion efficiency of 8.60% is achieved.
Article
Physics, Applied
Afrina Khanam, Jonatan Slotte, Filip Tuomisto, Subhali Subhechha, Mihaela Popovici, Gouri Sankar Kar
Summary: Positron annihilation signals were used to characterize the differences in open volume defects in TiN/TiO2/a-Si heterostructures grown at different temperatures. The Doppler and coincidence Doppler modes of positron annihilation spectroscopy were employed in this study. The results show that the positron trapping states of the TiO2 epilayers grown at different temperatures exhibit differences, and these differences are not caused by intermixing of the TiO2 and a-Si layers or the formation of thin SiO2 layers at the interface during the growth process.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Yufan Zhou, Gihan Velisa, Saro San, Miguel L. Crespillo, Zhe Fan, Hongbin Bei, William J. Weber, Pengyuan Xiu, Lumin Wang, Filip Tuomisto, Wai-Yim Ching, Yanwen Zhang
Summary: Understanding the defect production and damage evolution in concentrated solid solution alloys (CSAs) is crucial for revealing the underlying mechanisms behind their extraordinary mechanical properties and improved radiation tolerance. In this study, the defect structure in NiFeCoCr under ion irradiation was investigated using ion channeling technique and compared with previous results on Ni crystals. The influence of chemical complexity on defect production and clustering was discussed, and the role of chemical disorder in the CSA was investigated using ab initio calculations. The results provide insights into the impact of chemical complexity on defect structure evolution in CSAs.
JOURNAL OF NUCLEAR MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Piero Mazzolini, Zsolt Fogarassy, Antonella Parisini, Francesco Mezzadri, David Diercks, Matteo Bosi, Luca Seravalli, Anna Sacchi, Giulia Spaggiari, Danilo Bersani, Oliver Bierwagen, Benjamin Moritz Janzen, Marcella Naomi Marggraf, Markus R. Wagner, Ildiko Cora, Bela Pecz, Abbes Tahraoui, Alessio Bosio, Carmine Borelli, Stefano Leone, Roberto Fornari
Summary: Unintentionally doped kappa-Ga2O3 epitaxial films on sapphire substrates exhibit columnar rotational domains that inhibit in-plane electronic conduction. The introduction of silane doping increases the domain size and mobility, improving in-plane conduction. Non-destructive techniques based on X-ray diffraction and Raman spectroscopy can be used to compare domain dimensions.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Syeed E. Ahmed, Violet M. Poole, Jani Jesenovec, Benjamin L. Dutton, John S. McCloy, Matthew D. McCluskey
Summary: Annealing Ba1-xCaxTiO3 (BCTO) under a flowing humid 2% hydrogen-argon gas mixture results in room-temperature persistent photoconductivity (PPC). This is attributed to the presence of substitutional hydrogen impurities that can be photoexcited. The threshold photon energy for PPC in BCTO is lower than that of BaTiO3 and SrTiO3, and the effect is reversible upon annealing in air.
JOURNAL OF ELECTRONIC MATERIALS
(2023)
Article
Chemistry, Inorganic & Nuclear
Franz Kamutzki, Maged F. Bekheet, Soren Selve, Felix Kampmann, Konrad Siemensmeyer, Delf Kober, Roland Gillen, Markus Wagner, Janina Maultzsch, Aleksander Gurlo, Dorian A. H. Hanaor
Summary: A novel sodium gadolinium pyroxene (NaGdSi2O6) was successfully synthesized and its crystal structure was determined. The sodium gadolinium pyroxene showed weak antiferromagnetic coupling, but no long-range magnetic order was observed above 2 K.
JOURNAL OF SOLID STATE CHEMISTRY
(2023)
Review
Physics, Applied
Filip Tuomisto
Summary: The presence of Ga vacancies and their unusual structure in beta-Ga2O3 have been extensively studied, and both experimental techniques and theoretical calculations confirm that the split Ga vacancy configuration has the lowest formation energy. However, the anisotropic signal and lack of a proper reference sample pose challenges for experiments like positron annihilation spectroscopy. Despite these challenges, the majority of data strongly indicates that high concentrations of split Ga vacancies exist in various configurations in beta-Ga2O3 samples. EPR, IR spectroscopy, and scanning transmission electron microscopy experiments all suggest that the split Ga vacancy configuration is the most likely interpretation of the data. However, the exact structure of the split Ga vacancies in terms of complexes with O vacancies and hydrogen still needs further investigation.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2023)
Article
Physics, Applied
M. Ries, E. Poliani, F. Nippert, D. Seidlitz, L. T. H. Greif, I. Koslow, J. Blaesing, M. Auf der Maur, A. Hoffmann, N. Esser, M. R. Wagner
Summary: In this study, the electronic and optical properties of InGaN single quantum wells with thin GaN cap-layers were investigated. A significant spectral shift of quantum well emission was observed for cap-layer thicknesses between 1 and 10 nm. The origin of this shift was explained by calculations and the influence of alloy fluctuations and homogeneity was studied on both the microscale and nanoscale using UV micro-Raman scattering and TERS. The results demonstrated the capabilities of TERS to resolve nanoscale thickness fluctuations and compositional inhomogeneities in ultra-thin semiconductor layers.
JOURNAL OF APPLIED PHYSICS
(2023)
Review
Materials Science, Multidisciplinary
G. Velisa, F. Granberg, E. Levo, Y. Zhou, Z. Fan, H. Bei, F. Tuomisto, K. Nordlund, F. Djurabekova, W. J. Weber, Y. Zhang
Summary: Systematic temperature-effects investigations on damage evolution in ion-irradiated Ni-based concentrated solid-solution alloys are crucial for ensuring their reliability in nuclear applications. By comparing experimental and theoretical data on equiatomic NiFe, NiCoCr, and NiCoFeCr alloys, as well as new ion channeling results on ion-irradiated NiCoFeCr at 500 K, we suggest that the lower migration energy of vacancies in NiCoCr is the reason why it is no longer outperforming NiFe under ion irradiation above 300 K, as supported by independent theoretical calculations and TEM results from the literature.
JOURNAL OF MATERIALS RESEARCH
(2023)
Article
Engineering, Electrical & Electronic
Marta Sawicka, Oliwia Golyga, Natalia Fiuczek, Grzegorz Muziol, Anna Feduniewicz- Zmuda, Marcin Siekacz, Henryk Turski, Robert Czernecki, Ewa Grzanka, Igor Prozheev, Filip Tuomisto, Czeslaw Skierbiszewski
Summary: A method for fabricating buried hollow channels inside GaN structures using selective area doping and electrochemical etching is presented. The channel width is defined by selective area ion implantation mask geometry and the vertical dimension depends on implantation energy and annealing conditions. The proposed technology has potential for integration with device fabrication and processing, as observed by X-ray diffraction for strain removal and surface roughness evaluation.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2023)
Article
Physics, Condensed Matter
Igor Prozheev, Malgorzata Iwinska, Tomasz Sochacki, Michal Bockowski, Rene Bes, Filip Tuomisto
Summary: The results of positron lifetime and X-ray absorption spectroscopy in Si-doped GaN crystals, grown by HVPE, are presented. High Si concentration leads to significant compensation effects. Ga vacancies are insufficient as compensation centers and other acceptor-like impurities are present at much lower concentrations than Si. X-ray absorption shows that the local environment of Si dopants is different in compensated samples. Simulated spectra suggest that Si has a higher presence in the nearest local environment in compensated spectra, indicating autocompensation of Si dopants in high Si content GaN samples grown by HVPE.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Nuclear Science & Technology
T. Vuoriheimo, A. Liski, P. Jalkanen, T. Ahlgren, K. Mizohata, K. Heinola, Y. Zayachuk, K. K. Tseng, C. W. Tsai, J. W. Yeh, F. Tuomisto
Summary: Plasma-facing components in future fusion reactors require high temperature and particle resilience. Tungsten is currently the primary material due to its properties, but better alternatives are being explored. This study investigates the effects of hydrogen isotope exchange in an equiatomic high entropy alloy (HEA), providing insight into its suitability for fusion applications.
NUCLEAR MATERIALS AND ENERGY
(2023)
Article
Chemistry, Physical
P. Jaroszynski, E. Grzanka, M. Grabowski, G. Staszczak, I. Prozheev, R. Jakiela, F. Tuomisto, M. Bockowski
Summary: This study investigated the europium doping of gallium nitride using a novel ultra-high pressure annealing method. Ammonothermal gallium nitride substrates (n-type) were used as targets for europium ion implantation. The implanted samples were annealed at high nitrogen pressure and temperatures ranging from 1473 K to 1753 K. The concentration profiles of europium and the morphology and structural quality of the samples were analyzed. The presence of optically active EuGa-X defect complexes was suggested based on photoluminescence spectra analysis at low temperature (20 K). The limitations of diffusion-based europium doping of ammonothermal gallium nitride are discussed.
APPLIED SURFACE SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
K. A. Simula, J. Haerkonen, I. Zhelezova, N. D. Drummond, F. Tuomisto, I. Makkonen
Summary: The paper presents a variational quantum Monte Carlo method for simulating the momentum densities of annihilating electron-positron pairs in semiconductors and insulators. By comparing experimental data with simulation results, it is demonstrated that direct modeling of electron-positron correlations is important for supporting the theory of positron annihilation spectroscopies.
Article
Chemistry, Multidisciplinary
Maximilian Ries, Felix Nippert, Benjamin Maerz, Manuel Alonso-Orts, Tim Grieb, Rudolfo Hoetzel, Pascal Hille, Pouria Emtenani, Eser Metin Akinoglu, Eugen Speiser, Julian Plaickner, Jorg Schoermann, Matthias Auf Der Maur, Knut Mueller-Caspary, Andreas Rosenauer, Norbert Esser, Martin Eickhoff, Markus R. Wagner
Summary: The emission properties of InGaN/GaN nanowires grown by plasma-assisted molecular beam epitaxy are investigated using various techniques, revealing the roles of inhomogeneous In distribution and radial fields in the emission properties. The radial built-in fields are found to be modest, while variations in the local In content have a greater impact. Two luminescence bands with large positive and moderate negative polarization ratios were observed, associated with In-rich inclusions and spontaneously formed superlattices in the nanowires.
Article
Nanoscience & Nanotechnology
Manuel Alonso-Orts, Rudolfo Hoetzel, Tim Grieb, Matthias Auf Der Maur, Maximilian Ries, Felix Nippert, Benjamin Maerz, Knut Mueller-Caspary, Markus R. R. Wagner, Andreas Rosenauer, Martin Eickhoff
Summary: The influence of self-assembled short-period superlattices (SPSLs) on the structural and optical properties of InGaN/GaN nanowires (NWs) grown by PAMBE on Si (111) was studied. SPSLs were found to self-assemble during growth in most of the studied nanostructures, demonstrating a short-range ordering of In-rich and In-poor InxGa1-xN regions. The polarized photoluminescence analysis revealed that the NWs exhibited parallel polarized red-yellow emission and perpendicular polarized blue emission, attributed to different In-rich regions.