Solid State Physics Research Articles

Preface

32nd Joint Seminar DMSRE32 2023 Development of Materials Science in Research and Education 4 – 8 September 2023, hotel IRIS, Pavlov, Czechia The first Joint Seminar “Development of Materials Science in Research and Education” (DMSRE) was held at Gabcíkovo in Czechoslovakia in 1991. On 4 – 8 September 2023, the 32 nd edition of the DMSRE seminar took place at the Iris Hotel in Pavlov, Czechia. The seminar is organized by the Czechoslovak Association for Crystal Growth and the Slovak Expert Group of Solid State Chemistry and Physics under the auspices of the Institute of Physics of the Czech Academy of Sciences, Faculty of Chemical and Food Technology SUT Bratislava, and Slovak Society for Industrial Chemistry every year with one break in 2021 (COVID-19 pandemic).The Seminar brings together a unique combination of scientists across a multidisciplinary spectrum and provides an ideal forum for the presentations and discussions of recent developments and achievements in all theoretical and experimental aspects of preparation processes, characterization and applications of materials in bulk, thin film, nano-crystalline and glassy states.The scientific sessions covered the following topics on materials science:– trends in development of the materials research– results of materials science research– education of materials science at the universities– information on equipment for preparation and characterisation of materials.The ambition of the conference organizers was to prepare a pleasant, open, friendly atmosphere for establishing new contacts, supporting mutual cooperation, spreading new scientific ideas and acquired knowledge, and also supporting education in the field of materials science.At the seminar, 66 participants presented 54 onsite and 4 online talks, of which 27 papers are included in this Proceeding. s of all contributions and seminar program are available on the conference website https://dms.fzu.cz/32/.Mária Behúlová and Zdenek Kožíšek (Editors)List of Organized by, Under the auspicies of, Scientific Committee, Organizing Committee, Sponsors, Editors are available in this pdf.

Observation of interband Berry phase in laser-driven crystals.

Ever since its discovery1, the notion of the Berry phase has permeated all branches of physics and plays an important part in a variety of quantum phenomena2. However, so far all its realizations have been based on a continuous evolution of the quantum state, following a cyclic path. Here we introduce and demonstrate a conceptually new manifestation of the Berry phase in light-driven crystals, in which the electronic wavefunction accumulates a geometric phase during a discrete evolution between different bands, while preserving the coherence of the process. We experimentally reveal this phase by using a strong laser field to engineer an internal interferometer, induced during less than one cycle of the driving field, which maps the phase onto the emission of higher-order harmonics. Our work provides an opportunity for the study of geometric phases, leading to a variety of observations in light-driven topological phenomena and attosecond solid-state physics.

Generalized One-Dimensional Periodic Potential Wells Tending to the Dirac Delta Potential

The solution of a quantum periodic potential in solid state physics is relevant because one can understand how electrons behave in a corresponding crystal. In this paper, the analytical solution of the energy formulation for a one-dimensional periodic potential that meets certain boundary conditions is developed in a didactic and detailed way. In turn, the group speed and effective mass are also calculated from the transcendental energy equation of a potential V=V(x). From this, a comparison is made with periodic potentials with known analytical solutions, such as the Dirac delta, as well as rectangular and triangular potentials. Finally, some limits are proposed in which these periodic potentials of the form V=V(x) approach the periodic Dirac delta potential of positive intensity. Therefore, the calculations described in this paper can be used as the basis for more-complex one-dimensional potentials and related simulations.

Atoms Dressed by Virtual and Real Photons

Specific properties of quantum field theory are described by considering the combination of the system under investigation and the cloud of virtual or real particles associated with the field. Such a structure is called a “dressed system”, in contrast with the bare one in the absence of the interaction with the field. The description of the properties of such clouds in various physical situations is, today, an active research area. Here, we present the main features associated with virtual and real dressings, focusing on photon dressing. In analogy to virtual photon clouds dressing electrons in vacuum, virtual phonon clouds appear in solid-state physics. The interaction between real photons and the schematized two-level structure of an atom paves the way to flexible quantum control. Here, a unifying Floquet engineering approach is applied to describe single- and multiple-dressed atom configurations. Connections with the past and present atomic physics experiments are presented.

Influence of graphene on the electronic and magnetic properties of an iron(III) porphyrin chloride complex.

Although iron-based single atom catalysts are regarded as a promising alternative to precious metal catalysts, their precise electronic structures during catalysis still pose challenges for computational descriptions. A particularly urgent issue to be addressed is the influence of the environment on the electronic structure, and how to describe this accurately using computational methods. Here, we study an iron porphyrin chloride complex adsorbed on a graphene sheet using density functional theory calculations to probe how much the electronic structure is influenced by the presence of a graphene layer. Our results indicate that weak interactions due to van der Waals forces dominate between the porphyrin complex and graphene, and only a small amount of charge is transferred between the two entities. Furthermore, the interplay of the ligand field environment, strong p-d hybridization, and correlation effects within the complex are strongly involved in determining the spin state of the iron ion. By bridging molecular chemistry and solid state physics, this study provides first steps towards a joint analysis of the properties of iron-based catalysts from first principles.

Attosecond science the art of making electron movies

After 22 years since the first experimental demonstration of attosecond pulses, the attosecond science has become a very active field of research, with prominent applications in atomic, molecular and solid-state physics. Experimental advances, in terms of new sources, devices and techniques, are still required, together with new theoretical tools and approaches, but attosecond physics has firmly established as a mature research field.

Squeezing and evolution of single particle by frequency jumping in two-dimensional rotating harmonic

The control of microscopic particle behavior based on a specific external field has always been a research hotspot in the field of physics. Many studies have been exploring various methods to manipulate and control the behavior of particles at a microscopic level. In this work, we investigate the phenomenon of single-particle squeezing induced by frequency jumping in a two-dimensional rotating harmonic oscillator potential. Squeezing, as a quantum mechanical phenomenon, has attracted significant attention due to its potential applications in various fields. It refers to the reduction of fluctuations in certain physical quantities, allowing for more precise measurement results. Squeezing phenomena have been extensively studied in different physical systems, including optics, atomic physics, and solid-state physics. However, there have been few reports on the quantum state squeezing phenomenon induced by frequency jumping in a rotating harmonic oscillator potential. Therefore, our study aims to fill this gap and shed light on this intriguing phenomenon. To explore the squeezing phenomenon induced by frequency jumping, we focus on the fluctuations and squeezing of the single particle’s cyclotron radius coordinate and center-guided coordinate in the two-dimensional rotating harmonic oscillator potential. Through numerical simulations and theoretical analysis, we can understand the influence of frequency jumping on the degree of squeezing and reveal the underlying physical mechanism of squeezing evolution. In this work, we first investigate the influence of frequency jumping on the squeezing evolution of the cyclotron radius mode. By carefully selecting appropriate jumping moments, we analyze the influence of frequency jumping on the degree of squeezing. Our research results show that the degree of squeezing in the cyclotron radius coordinate remains unchanged at the jumping moment. However, we observe a stronger squeezing phenomenon in the subsequent evolution process. This indicates that frequency jumping plays a crucial role in squeezing evolution of the cyclotron radius mode. Furthermore, we focus on the squeezing evolution of the center-guided mode during frequency jumping. By selecting suitable parameters, we analyze the squeezing and evolution of two squeezing modes: the divergent mode and the oscillatory mode. Interestingly, we discover the existence of a critical potential trap aspect ratio, which is determined by the rotation angular velocity of the external potential. When the aspect ratio approaches this critical value, the squeezing mode undergoes a transition, and a significant squeezing phenomenon appears in the oscillatory mode. This finding provides valuable insights into the origin and control of squeezing phenomena. Finally, we discuss the potential applications of these squeezing phenomena. Squeezing has significant implications in the fields of quantum sensing and quantum information processing. Through a deeper understanding of the squeezing evolution process caused by frequency jump, we can better control the microscopic particle behavior through external field. This knowledge opens up new possibilities for future physical research and technical applications.

Synthesis and characterization of O-PDI for futuristic optoelectronic and rectifier applications

A non-fullerene organic semiconductor, N,N′-di(cis-9-octadecen-1-yl)perylene-3,4,9,10-tetracarboxylic diimide (O-PDI), was synthesized and characterized for its optoelectronic and rectifier applications.

Re/Ir@Os-doping induced insulator-to-metal transition in Mott-insulator Ca2FeOsO6: octahedral distortion effects.

Regardless of several investigations to elucidate the ground state of the strongly correlated electron systems in doped Mott-insulators (MIs), the origin of the doping-induced insulator-to-metal transition (IMT) remains a crucial and debatable subject in solid-state physics. Herein, we explore the consequences of Re/Ir-doping at the Os-site (Re/Ir@Os), on the physical properties of the MI ferrimagnetic (FiM) Ca2FeOsO6 double perovskite oxides using density functional theory calculations. The doped structures' solidity is analyzed by computing the defect formation energies in terms of the dopant-rich situation, which confirms their growth credibility at ambient conditions along with mechanical and dynamical stabilities. Various FiM spin-ordering is taken into account in the doped structures to analyze the magnetic ground state, which is FiM-I/FiM-II in the Re/Ir@Os-doped system. Remarkably, an IMT is predicted in the Re/Ir@Os-doped structures, which is due to the admixture of the partially occupied 5d orbitals of these ions. The calculated partial spin magnetic moments (ms) of +4.12, -1.58, -0.75 and +0.88μB on the Fe, Os, Re, and Ir ions, endorse the +3, +5, +5, and +4 states having electronic configurations of t32g↑t02g↓e2g↑e0g↓, t32g↑t02g↓e0g↑e0g↓, t22g↑t02g↓e0g↑e0g↓, t32g↑t22g↓e0g↑e0g↓, respectively. The "+" and "-" signs on the ions ms values, lead the systems into various FiM magnetic ordering. Moreover, the estimated Curie temperature (TC) using the Heisenberg model in the pristine structure is 334 K, which is close to the experimentally observed value of 320 K along with a colossal uniaxial magneto crystalline anisotropy energy constant (K) of 2.95 × 107 erg cm-3 having the easy magnetic axis of the ac-plane ([101]). It is established that TC/K reduces and enhances to 298 K/1.33 × 107 erg cm-3 and 365 K/4.71 × 107 erg cm-3 for the Re@Os and Ir@Os-doped motif due to an increase and decrease in the octahedral distortions compared to that of the pristine system, respectively.

Innovation and Practice of Solid State Physics Teaching Model Based on Quantum ESPRESSO

Innovation and Practice of Solid State Physics Teaching Model Based on Quantum ESPRESSO

Harnessing machine learning for efficient large-scale interatomic potential for sildenafil and pharmaceuticals containing H, C, N, O, and S.

In this study a cutting-edge approach to producing accurate and computationally efficient interatomic potentials using machine learning algorithms is presented. Specifically, the study focuses on the application of Allegro, a novel machine learning algorithm, running on high-performance GPUs for training potentials. The choice of training parameters plays a pivotal role in the quality of the potential functions. To enable this methodology, the "Solvated Protein Fragments" dataset, containing nearly 2.7 million Density Functional Theory (DFT) calculations for many-body intermolecular interactions involving protein fragments and water molecules, encompassing H, C, N, O, and S elements, is considered as the training dataset. The project optimizes computational efficiency by reducing the initial dataset size according to the intended application. To assess the efficacy of the approach, the sildenafil citrate, iso-sildenafil, aspirin, ibuprofen, mebendazole and urea, representing all five relevant elements, serve as the test bed. The results of the Allegro-trained potentials demonstrate outstanding performance, benefiting from the combination of an appropriate training dataset and parameter selection. This notably enhanced computational efficiency when compared to the computationally intensive DFT method aided by GPU acceleration. Validation of the produced interatomic potentials is achieved through Allegro's own evaluation mechanism, yielding exceptional accuracy. Further verification is carried out through LAMMPS molecular dynamics simulations. Structural optimization by energy minimization and NPT Molecular Dynamics simulations are performed for each potential, assessing relaxation processes and energy reduction. Additional structures, including urea, ammonia, uracil, oxalic acid, and acetic acid, are tested, highlighting the potential's versatility in describing systems containing the aforementioned elements. Visualization of the results confirms the scientific accuracy of each structure's relaxation. The findings of this study demonstrate strong scaling and the potential for applications in pharmaceutical research, allowing the exploration of larger molecular structures not previously amenable to computational analysis at this level of accuracy The success of the machine learning approach underscores its potential to revolutionize computational solid-state physics.

Non-resonant inelastic X-ray scattering for discrimination of pigments.

Inelastic X-ray scattering (IXS) spectroscopy has been used in many fields of solid-state physics and theoretical chemistry as an accurate and quantitative probe of elementary excitations. We show that non-resonant IXS spectra in the energy loss range below 100 eV exhibit a strong contrast across a wide range of commercially available pigments, opening new routes for their discrimination. These signatures combine plasmonic transitions, collective excitations and low energy absorption edges. We have performed IXS to discriminate different artists' pigments within complex mixtures and to quantitatively determine rutile and anatase polymorphs of TiO2. The integration of experimental data on pigment powders with suitable ab initio simulations shows a precise fit of the spectroscopic data both in the position of the resonances and in their relative intensity.

Adiabatic connection interaction strength interpolation method made accurate for the uniform electron gas.

The adiabatic connection interaction strength interpolation (ISI)-like method provides a high-level expression for the correlation energy, being, in principle, exact not only in the weak-interaction limit, where it recovers the second-order Görling-Levy perturbation term, but also in the strong-interaction limit that is described by the strictly correlated electron approach. In this work, we construct a genISI functional made accurate for the uniform electron gas, a solid-state physics paradigm that is a very difficult test for ISI-like correlation functionals. We assess the genISI functional for various jellium spheres with the number of electrons Z ≤ 912 and for the non-relativistic noble atoms with Z ≤ 290. For the jellium clusters, the genISI is remarkably accurate, while for the noble atoms, it shows a good performance, similar to other ISI-like methods. Then, the genISI functional can open the path using the ISI-like method in solid-state calculations.

ПІДХІД ДО ОЦІНЮВАННЯ ЕФЕКТИВНОСТІ КОМПЛЕКСНОЇ СИСТЕМИ ОХОРОНИ

Protection and protection of human health, life, habitat, material and intellectual property is an important task at the current stage of society's development. Security and protection systems based on legal, organizational, moral and ethical, hardware and software methods and tools are used to solve this problem. They must meet the legal norms and requirements that are put forward for each category of protection objects. One of the important hardware and software means of protection are elements and devices of electronic equipment, including sensor devices. Their functioning is based on the achievements of solid-state physics, optics, electro-optics, electro-acoustics, etc. Modern electronic technologies make it possible to create effective microelectronic sensor devices for security and protection systems, the functioning of which consists in the use of optical, mechanical, magnetic, piezoelectric, strainometric, capacitive and other types of signal transducers. In the process of building modern safety and security systems, it is necessary, on the one hand, to have information about the capabilities and peculiarities of the functioning of individual components that ensure the fulfillment of the task of protecting the object. On the other hand, it is necessary to have an assessment of the effectiveness of the developed system, which should include both reliability indicators of all elements and channels of information transmission, as well as indicators of the performance of the functional task. The developed mathematical model of the efficiency of the application of the protection system will provide an opportunity to make the correct choice of the constituent elements of the system, the parameters of which most fully ensure the performance of the protection task. This approach ensures the organization of the interaction of security alarm systems, fire alarm systems, access control systems, video surveillance systems and centralized security consoles. Keywords: complex of technical means; security system sensor; centralized security control panel; security system efficiency.

Impact of Oxygen on the Generation of Slip Lines and the Electronic Properties of Si-based Substrates

The impact of oxygen in silicon substrates and the formation of oxide precipitates have been widely investigated in the past, because of deleterious electrical recombination and their impact on yield [1]. The presence of oxygen can also be beneficial, with the so-called internal gettering effect by oxygen precipitates. More recently, researchers pointed out the role of interstitial oxygen on the formation of slip lines and dislocations [1-2]. The impact of interstitial oxygen during thermal treatments has to be distinguished from the one of oxygen precipitates for a better understanding of various phenomena [3]. We show in this paper the combined impact of features such as interstitial oxygen, thermal processes and innovating SOI substrates on slip-line generation after complex device fabrication process flows.We have investigated different kinds of silicon and SOI substrates (with silicon obtained with the Czochralski method) that were submitted to different thermal treatments during a specific 65nm process flow targeting Radio-Frequency devices. We have worked on 300mm patterned and blanket wafers and focused notably on a last stressing oxidizing anneal step used for gate oxide formation. One type of SOI substrates had a poly-silicon layer beneath the buried oxide (named SOI Trap-Rich) specifically for RF applications [4]. We have used two kinds of processes, low and high temperature, in Rapid Thermal Oxidation (RTO) tools. Slip-line counts and cumulated lengths were monitored on blanket SOI and Si wafers after main anneal steps and gate oxide RTO, using a Pattern Wafer Geometry (PWG) tool (figure 1). The post-nitridation anneal for gate oxide formation was performed at temperature above 1000°C in single wafer tools. On Si and SOI with 70nm-thick Si layers, no slip-lines were detected using Process-Of-Record conditions (whatever the process temperature). Meanwhile, high temperatures and above all extreme edge offset temperatures (usually used in single wafer reactors to have processes as uniform as possible) resulted in higher slip-line counts and cumulated lengths on the wafers back-sides. On SOI with TR layers, slip-lines were detected whatever the conditions, although they were less numerous with a low temperature and optimized process.Differences for wafers processed at the same time highlighted the influence of several parameters: the thermal history evidenced by wafer-to-wafer variability for SOI wafers with a Trap-rich layer underneath, the stack (SOI type and nature) and the process temperature used during previous oxidation steps. A typical map obtained by the PWG is shown in Figure 2 [5]. Meanwhile, Figure 3 shows a macro Photoluminescence mapping of a blanket Silicon wafer, pointing out the electrical activity of planar defects at the wafer edges (non-radiative recombination on dislocations). A direct relationship was found between the slip-line origin and contact points coming from ring supports at wafers’ back-side (the origins of slip lines). Figure 4 shows the relationship between the oxygen concentration in bulk Si and the silicon handles of SOI substrates, the slip-line counts and wafer warp. Based on this trend, we have also statistically confirmed on patterned wafers processed in a 65nm RF flow, the direct relationship between substrate deformation, low oxygen concentration in the Si handle (lower at wafer edge in agreement with slip line formation) and lithography overlay (OVL) measurements. When OVL exceeded a certain value, residuals (i.e. misalignments due to shifts between patterns which are symbolized by vectors) could not be corrected any more. It is typically what we have on SOI TR substrates with an extreme offset temperature (intentionally too high). An OVL signature out of our range of specifications is shown in Figure 5 on a patterned wafer processed up to gate oxide level. High numbers of slip lines result in OVL over detection. Meanwhile, wafer deformations and more precisely stresses that are too high increase OVL residuals. Above a given threshold, the built-in stress in the wafer is so high that slip lines are nucleated at the wafer edges to minimize the elastic energy. Above a second threshold, the wafer deformation is irreversible. Finally, the relationship between OVL and electrical failure is not straightforward and more often the consequence of mixed parameters such as substrate composition and nature, annealing steps and etching during Shallow Trench Isolation or gate oxide definition.[1] J. Fujise et al, Japanese J. of Applied Physics, 57 (035501) 2018[2] J. Fujise et al, J. Solid State Science and Techn., 9 (055012) 2020[3] G. Kissinger et al, J. Solid State Science and Techn., 8 (N79) 2019[4] B.K. Esfeh et al, Solid State Electronics, 128 (121) 2017[5] V. Brouzet et al, ASMC conference, april 2019 Figure 1

(Europe Section Heinz Gerischer Award) Endeavours in the Electro-Solar World of Schottky, Mott and Gerischer

The origins of semiconductor electrochemistry lies in the early 20th century with the pioneering work of scientists like Walter H. Schottky, Nevill Mott, and Heinz Gerischer. Schottky and Mott made significant contributions to the understanding of semiconductor physics, while Gerischer is often credited with laying the groundwork for the field of semiconductor electrochemistry. Particularly Gerischer's studies on the kinetics of electron transfer reactions at semiconductor-electrolyte interfaces have been fundamental to our understanding of semiconductor chemistry and photoelectrochemistry. His early work has conceptually created strong links between electrochemistry and solid state physics, has created a close connection to photochemistry, and has profoundly improved the understanding of interfacial reactions. It allowed to exploit the feature of semiconductors to conduct electricity under certain conditions and their conductivity being strongly altered by doping or by the application of an electric field or a photon flux.These findings have stimulated a work in a wide range of science and led to the foundations towards tremendous success of applications across diverse fields such as Photovoltaics (Solar Cells), Photoelectrochemical Cells, Sensors, Catalysis, Batteries and Fuel Cells, Corrosion Protection, Electrochromic Devices or Water Treatment.The presentation will give a personal perception of the principles, their use in the last 20 years. It is focused on TiO2 based semiconductor electrochemistry and its applications. It involves the growth and use of titania nanotubes their properties and applications, as well as – in recent years – the use of single atoms as co-catalysts in the field of semiconductor electrochemistry.

Mixed Ionic Electronic Conduction Caused by Phase Transformation and Interfacial Segregation in an Entropy Stabilized Oxide

Research on entropy-stabilized oxides (ESO) [1] has primarily focused on exploring new single-phase structures with diverse chemistries, or unique properties, such as high Li-ion conductivity, high dielectric constant, low thermal conductivity, good electrochemical cycling stability, and high storage capacity retention [2]. However, few studies discuss the impact of secondary phase formation on functionality such as electrical conductivity [3] despite the fact that annealing this single-phase ESO causes it to undergo a phase transformation leading to the formation of Cu-rich and Co-rich secondary phases [4]. To address this gap, this work [5] investigates the electrical transport mechanisms in the canonical entropy-stabilized oxide (Co,Cu,Mg,Ni,Zn)O as a function of secondary phase content. Here, the structure and composition of single-phase and multiphase ESOs, and their GBs and HIs are probed using atomic-resolution imaging by scanning transmission electron microscopy (STEM) coupled with nanoscale spectroscopy by electron energy-dispersive spectroscopy (EDS) and electron energy-loss spectroscopy (EELS). Our findings suggest that when single-phase, the oxide is an oxygen ion conductor. After 2 h of heat treatment, Cu-rich tenorite particles form at some grain boundaries, turning the grain interior rocksalt oxide into a mixed ionic-electronic conductor via oxygen ions and small hole polaron Co2+/Co3+ and Cu2+/Cu+ pairs. 24 h of heat treatment leads to the full coverage of Cu-rich tenorite particles at all grain boundaries and the formation of anisotropic Cu-rich tenorite and equiaxed Co-rich spinel particles in the grains. While the grain interiors exhibit similar mixed ionic-electronic conduction, Cu-rich tenorite grain boundary phases create a pathway for Cu2+/Cu3+ small hole polarons. The ability to selectively grow secondary phases nucleated at grain boundaries enables tuning of electrical properties in entropy-stabilized and complex concentrated oxides using microstructure design, nanoscale engineering, and heat treatment, paving the way to develop many novel materials.[1] C. M. Rost, J.-P. Maria, Nat Commun, 2015.[2] A. Salian, S. Mandal, Critical Reviews in Solid State and Materials Sciences, 2022.[3] M. Moździerz, K. Świerczek, Acta Materialia, 2021.[4] A. D. Dupuy, J. M. Schoenung, Journal of the European Ceramic Society, 2021.[5] H. Vahidi...W. J. Bowman (submitted). Acknowledgments This research was primarily supported by the National Science Foundation Materials Research Science and Engineering Center program through the UC Irvine Center for Complex and Active Materials (DMR-2011967). WJB and HV acknowledge partial support from the UCI new faculty startup funding. The authors acknowledge the use of facilities and instrumentation at the UC Irvine Materials Research Institute (IMRI) supported in part by the National Science Foundation Materials Research Science and Engineering Center program through the UC Irvine Center for Complex and Active Materials (DMR-2011967).

Understanding LiNiO2 Electronic Structure and Redox Mechanism by Raman and X-Ray Techniques

LiNiO2 (LNO) is considered a very promising and high energy density alternative to Co-containing Li-ion battery cathodes. It is also the benchmarked cathode material of the European BIGMAP project, which aim is to combine advance operando characterization, computational modelling and artificial intelligence in order to accelerate the research and development of new generation batteries.However, the material suffers from several degradation issues resulting in fading cell performance. In particular, the presence of highly reactive Ni4+ species at the electrode/electrolyte interface1, Ni dissolution from the cathode leading to the loss of active material 2, and O2 release at high voltage are the major drawbacks precluding commercial applications. A recent in situ study1 has shown that O2 release compromises the structural stability and triggers reactions with ethylene carbonate (EC), prompting CO2evolution3,4.In parallel, solid state physics community is also largely interested into LiNiO2 in the framework of a larger investigation around the electronic and atomic structure of nickelates, in particular rare-earth nickelates. This interest rises from the fact that there is still no consensus on the atomic/electronic structure of LiNiO2, while different descriptions exist in literature. Local probe techniques demonstrate the distortion of NiO6 octahedra, and there are two on-going theories for explaining the presence of this distortion: (i) Ni3+ (t2g6 eg1) Jahn-Teller (JT) distortion, (ii) 2 Ni3+ → Ni2+ + Ni4+ bond disproportionation (BD)5. Surprisingly, the local order distortion does not result in the long-range distortion, the mechanism behind this phenomenon is not completely understood.In this contribution we present a detailed study of LNO cathode material by operando Raman and X-ray absorption spectroscopy (XAS) at the Ni K-edge, ex situ X-ray emission spectroscopy (XES) and resonant Inelastic X-ray scattering (RIXS). Distinguishing between JT and BD models is challenging, and therefore NaNiO2 reference is used, which is isoelectronic material to LiNiO2, and is known to feature long-range JT distortion.While XAS is widely established technique to probe local structure and transition metal oxidation state, RIXS is useful for assessing d-d transitions and bond disproportionation. Operando Raman spectroscopy is an excellent tool for studying phase transitions in Li-ion battery cathodes and is therefore complementary to the employed X-ray techniques6. It provides information on two characteristic for layered oxides crystalline phonon modes A1g and Eg, and sheds light on both short-range order and cationic/anionic redox. The penetration depth is estimated as top few hundred nanometers of around five micrometres sized secondary particle, therefore near-surface area is probed. The results show a complex behaviour of band positions and intensities during cycling (figure 1), corresponding to four phases transformations. Notably the peaks intensities increase considerably, while the widths are decreased, which is evidence of increased order upon material delithiation, and is in agreement with the Extended X-ray Absorption Fine Structure (EXAFS). Raman is also used to evaluate the contribution of anionic redox, since all the reduced oxygen species (superoxide, peroxide and molecular oxygen) have well-known Raman-active modes.To conclude, we demonstrate how a combination of multiple vibrational and X-rays based spectroscopies provides a better understanding of both LNO ground state electronic structure and redox mechanism. This increased fundamental understanding will stimulate the design of better strategies for prevention of the material degradation and improved cycle retention.

Nanosecond Laser Irradiation for Interface Bonding Characterization

Hydrophilic direct bonding is nowadays widely used in microelectronics for SOI substrate fabrication and 3D integration. Trapped water at the bonding interface plays a key role in the adhesion and adherence mechanisms [1]. Previous studies also reported that water could penetrate the bonding interface. This may modify the radial inhomogeneity of water [2]. However, this reported technique requires specific Silicon-to-Silicon bonding, lacks precision and needs additional characterizations (XRR, FTIR) to quantify the amount of trapped water at the bonding interface. In this work, we present an original methodology that can both accurately characterize and quantify water imbibition.Pulsed nanosecond laser annealing enables to reach extremely high temperatures, above the silicon melting point (1414°C), for very short durations (from a few tens of ns to a few hundred ns). These annealing conditions result in silicon surface melt. The beginning of melting is heterogeneous and leads to a particular surface topology with the formation of molten islands during laser annealing [3]. Recrystallization of these molten islands results in a localized increase of roughness (see fig. 1a). This roughness can exceed the direct bonding critical roughness. Non-bonded areas, i.e. bonding defects, can then be intentionally and precisely placed at the direct bonding interface.In a first step, bonding defects were thus formed along a wafer diameter with a 2 mm pitch. Then, using high-resolution acoustic microscopy, the bonding defects radii evolution was measured over time after direct bonding and without annealing (see fig. 1b). A progressive growth of defect radii was evidenced when getting closer and closer to the wafer edge. An additional water amount coming from the clean room atmosphere resulted in silicon oxidation at room temperature and di-hydrogen generation. Di-hydrogen was then trapped by bonding defects. In other words, bonding defects acted as humidity sensors. We could then record the penetration length and plot it as a function of the square root of time (fig. 1c). The penetration rate is the equivalent of a diffusion coefficient that could be calculated for both Silicon-to-Silicon and Silicon-to-Oxide bonding. We noted a very good agreement with Tedjini’s results for Silicon-to-Silicon bonding [2]. Meanwhile the calculated diffusion coefficient for Silicon-to-Oxide bonding was surprisingly about twice higher.Second, a bonding defect network with the same 2 mm pitch in both X and Y direction was created. After direct bonding, various duration 500°C temperature anneals were performed. The defects radii evolution was once again measured. As it increased over time, we could write the Griffith equilibrium between elastic (due to defect pressure) and surface (γ) energies. Describing defects as circular blisters, the amount of di-hydrogen trapped molecules could then be calculated. Plotting this number of H2 molecules, N, as a function of the annealing time (fig. 1d), we observe that a plateau was reached, meaning that all the di-hydrogen produced in the network was collected in the bonding defects. The water amount responsible for this di-hydrogen generation could then be evaluated and compared to data from other measurements. REFERENCES [1] F. Fournel, C. Martin-Cocher, D. Radisson, V. Larrey, E. Beche, C. Morales, P. A. Delean, F. Rieutord, and H. Moriceau, “Water Stress Corrosion in Bonded Structures”, ECS Journal of Solid State Science and Technology, 4 (5) P124-P130 (2015)[2] Tedjini M, Fournel F, Moriceau H, Larrey V, Landru D, Kononchuk O, et al. Interface water diffusion in silicon direct bonding. Appl Phys Lett. 12 sept 2016;109(11):111603.[3] L. Dagault, S. Kerdilès, P. Acosta Alba, J.-M. Hartmann, J.-P. Barnes, P. Gergaud, E. Scheid, and F. Cristiano, Investigation of Recrystallization and Stress Relaxation in Nanosecond Laser Annealed Si1−xGex/Si Epilayers, Appl. Surf. Sci. 527, 146752 (2020). Figure 1

A Comprehensive Study on Chemical Bonding and Open Spaces with Silicon Carbon Nitride Films for Direct Bonding

Wafer-to-wafer (W2W) direct bonding has been extensively developed as a key unit process for BS-PDN, CFET and advanced chiplet. As a bonding dielectric layer, CVD-SiO2 has been comprehensively studied for direct/hybrid bonding. SiCN is emerging dielectric bonding layer due to its unique properties such as high bonding strength at low annealing temperatures, suppressing void formation after Post Bond Annealing (PBA) and barrier properties against Cu diffusion [1][2]. However, the bonding mechanism for SiCN has not yet been clearly described. In this study, we investigated the mechanism from several kinds of perspectives by analyzing the properties of different films under various conditions. From those results, SiCN is characterized and compared to SiO2.SiO2 and SiCN films were deposited on 300mm Si wafers using plasma-enhanced chemical vapor deposition (PECVD). Subsequently, the wafers were polished and bonded.Atomic level open spaces in dielectric films were analyzed by positron annihilation spectroscopy (PAS). For the SiO2 samples after plasma activation, the S parameter did not show significant changes. This indicates the open spaces in SiO2 were not significantly influenced by plasma. On the contrary, the S parameter of SiCN samples increased after post deposition annealing (PDA) and decreased after plasma activation. This atomic level open spaces might be contributed the unique properties of SiCN for direct bonding.Since the analysis by PAS is one of the examples, we will report the overall results of the analysis on SiCN, e.g. TDS, XPS, AFM, and so on, then discuss the bonding mechanism for SiCN-SiCN.[1] F. Inoue, et. al., ECS Journal of Solid State Science and Technology 8(6), P346(2019)[2] F. Nagano, et. al., ECS Journal of Solid State Science and Technology 9 123011(2020) Figure 1