bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Surface Pretreatment to Reduce the Incubation Period of Iridium Thin Films Grown by ALD on the Oxide Surface
Authors: Jung Myung Jin , Kwon Se-Hun 
Published: February 2024

Iridium (Ir) has low figure of merit(×λ) and high melting temperature properties, so it has been recently spotlighted as a very important copper (Cu) alternative interconnect material in next-generation semiconductor devices. In particular, in the case of depositing a thin film using atomic layer deposition (ALD) technology, it can be expected to deposit extremely thin film with conformal, uniform and excellent step coverage characteristics even in a very complex structure or a trench structure of several nm dimension due to the inherent self-limiting characteristic of ALD. In this regard, ALD-Ir is considered as one of the most suitable metallization process for the application of advanced semiconductor interconnects. Therefore, considerable efforts have been conducted to develop a reliable ALD-Ir process having improved film qualities. And, ALD-Ir process with excellent thin film properties such as low electrical resistivity and negligible oxygen impurities was recently reported using Tricarbonyl (1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl iridium (C18H27IrO3 or TICP) precursor and oxygen [1]. However, in the case of this TICP precursor, it was difficult to deposit extremely thin and continuous Ir films on the hydroxyl-terminated oxide layer due to its long incubation delay.
Therefore, in this study, a method for depositing a very thin, uniform and continuous ALD-Ir thin film with low resistivity even on oxide materials was explored by reducing the incubation period and promoting nucleation using various surface pretreatment conditions. In addition, the nucleation behavior as well as film properties of ALD-Ir on the oxide material were systemically compared and analyzed according to the surface pretreatment conditions, and finally, ALD-Ir thin film with excellent properties on the oxide surface was obtained.
Plasma Anneal As a Stress Control Method in Low Temperature Al2O3 ALD Coatings
Authors: Kools Jacques , Zakhster Alter , Caries Pierre , Hill John 
Published: February 2024

The control of mechanical physical stress is an important requirement in a variety of applications, such as flexible electronics or thick optical coatings where film stress can cause delamination. Traditionally, in thermal ALD it has been difficult to control the stress. Al2O3 deposited at low temperature is consistently found to have a tensile stress level in the range of a 300 to 450 MPa ( refs 1-3). It is well established that In magnetron sputtering , film stress can be controlled straightforwardly using the Argon pressure during deposition, as this affects the level of bombardment of the growing film with energetic particles.
Paranjpe et al ( ref 1) have demonstrated that the use of a plasma anneal leads to densification and transition of the stress from tensile to compressive. The process consists of a sequence of deposition of a thin layer ( e.g. 5 nm) by thermal ALD, followed by exposure to a low energy plasma. The atomic displacements caused by low energy ions from the plasma tend to lead to filling of nanoscopic voids and point defects, thus releasing tensile stress.
In this presentation, we will review an in depth study of the effect of various process parameters on the ability of a capacitively coupled in-situ plasma anneal to control stress. The following parameters will be reviewed:

Gas composition: Argon plasmas, Oxygen plasmas and Argon oxygen mixtures are compared.

Gas Pressure: The effect of gas pressure on plasma characteristics and the resulting modification of the coating is studied

RF Power: RF Power was varied between 0 and 300 W ( 1.32 W/cm2)

Plasma duration
: The duration of the plasma treatment was varied from 0 to 60 seconds.
A process window was identified where the plasma anneal can be used as an effective, controllable tool to reduce stress in the coatings. This is illustrated in fig. 1, which shows the substrate warpage (“bow”) observed in 75 mm thick PET foils with a 50 nm Al2O3 coating deposited at 90 °C. It can be seen that the untreated coating (0 sec plasma) has a bow corresponding to a tensile stress of 370 MPa, in accordance with literature values. As the plasma anneal time increases, the stress value decreases. Applying a 60 sec plasma every 5 nm allows to deposit a virtually stress free coating. Simultaneously with the stress reduction, an increase of the optical index and a slight reduction of the thickness are observed, consistent with a densification of the coating.

References:

Ajit Paranjpe et al, “ Atomic Layer Deposition of AlOx for Thin Film Head Gap Applications” Journal of The Electrochemical Society, 148 (9) G465-G471 (2001)

David C. Miller et al “Thermo-mechanical properties of alumina films created using the atomic layer deposition technique” Sensors and Actuators A 164 58–67 (2010)

L. Puurunen et al “Implementing ALD Layers in MEMS processing” ECS Transactions, 11 (7) 3-14 (2007)

Figure 1
(Invited) Role of Heterojunctions in Metal Oxide Heterostructures for Energy and Environmental Applications
Authors: Pinna Nicola , Raza Muhammad Hamid 
Published: February 2024

Heterostructures made from metal oxide semiconductors are fundamental for the development of high-performance gas sensors and electrocatalysts, for examples. Here, I will introduce hierarchical heterostructures composed of p-, n-type and insulating metal oxide shells.
Precisely controlled films of alternating metal oxides can be uniformly deposited onto the inner and outer walls of the CNTs and onto mesoporous substrates by atomic layer deposition. The morphological, microstructural and electrical characteristics of the heterostructures were thoroughly investigated. Electrical resistance measurements highlighted the large influence of the metal oxides thickness and charge carriers types, suggesting that the conductivity of the electrodes are dominated by Schottky barrier junctions across the heterojunctions.
The behavior of the heterostructured electrodes in sensors and in electrocatalysis applications was investigated for low concentrations of volatile organic compounds and pollutants, and the oxygen evolution reaction in acidic media, respectively. For examples, the gas sensing response of the heterostructures showed a strong dependence on the thickness of the metal oxide shell layers and the type of heterostructures formed. On the other hand, the electrocatalytic performances are strongly related to the surface catalyst/stabilization layer and the electrical conductivity of the heterostructured electrode.
On the basis of the morphological, microstructural and electrical characterization, and electrode performances, the mechanisms which account for the performances of our heterostructured electrodes will be correlated and discussed.
Heat Generation Mechanisms of 18650 Lithium-Ion Battery Cells: An in-Depth Analysis
Authors: Maher Kenza , Zakaria Yahya 
Published: February 2024

Lithium-ion batteries are known for their exceptional properties such as high energy density and long-life cycle, making them popular in various applications, including electric vehicles and energy storage systems. However, the growing concern over the safety of lithium-ion batteries in hot environments with limited cooling has prompted an in-depth analysis of their heat generation mechanisms.
To address this concern, it is important to understand the heat generation mechanisms of lithium-ion batteries. In this study, we conducted an in-depth analysis of the heat generation mechanisms of 18650 lithium-ion battery cells. We investigated the impact of temperature on the primary aging mechanisms of the batteries, such as capacity fade and impedance growth. We also studied the thermal behavior of the batteries, including the heat generation and thermal stability.
Our analysis involved the disassembly of both fresh and aged 18650 lithium-ion battery cells, followed by a physico-chemical analysis on the electrodes at the microscale level to investigate the chemical and physical changes in the electrodes. We used advanced techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) to analyze the cells.
Our results showed that high temperatures can accelerate the chemical reactions within the battery, leading to an increase in heat generation. We also found that the aged battery cells had a higher degree of degradation in the electrodes compared to the fresh cells, which affected the battery's overall performance. Our analysis revealed changes in the surface morphology of the electrodes, which could impact the thermal behavior of the battery.
During the presentation, I will delve into the specific findings of our analysis of the 18650 lithium-ion battery cells. I will provide a more detailed explanation of the state of health, capacity fade, and impedance growth of the batteries, including how these aging mechanisms were affected by the high temperatures. Additionally, I will discuss the specific changes observed in the electrodes, such as the changes in the surface morphology, and how they impacted the battery's overall performance.
Overall, the presentation will provide a comprehensive overview of our study's findings and their significance for the future of lithium-ion batteries in high-temperature environments.
(Invited) Switching Characteristics of GaN Power Transistors
Authors: Shur Michael , Liu Xueqing , Ytterdal Trond 
Published: February 2024

A shorter switching time is one of the key advantages of GaN power devices over Si IGBTs. [1] In this paper, we report on the simulation of GaN power transistor switching and investigate the effect on the switching time novel design approaches ranging from the gate edge engineering (beyond just using field plates [2] for optimizing the voltage distribution in the drain-to-gate spacing to using the quantum well channel designs [3] that lead to the electron wave function penetration into wide band gap cladding layers with the commensurate increase in the breakdown voltage while keeping the advantage of high mobility in the device channel. We also report on the effect of a low conducting passivation for smoothing or even eliminating the sharp maximum of the electric field in the vicinity of the gate and field plate edges on switching time.[4] Additional contacts in the drain-to-gate spacing for the field control and variable doping implants could also decrease the switching time. Further optimization could be achieved with the perforated channel designs [5] decreasing the parasitic series resistance and improving the heat dissipation.
[1] A. Tüysüz, R. Bosshard, and J. W. Kolar, erformance Comparison of a GaN GIT and a Si IGBT for High-Speed Drive Applications, Proceedings of the International Power Electronics Conference - ECCE Asia (IPEC 2014), Hiroshima, Japan, May 18-21, 2014
[2] S. Karmalkar, M. S. Shur, G. Simin and M. A. Khan, Field-Plate Engineering for Heterostructure Field Effect Transistors, IEEE Trans. ED, 52, 12, pp. 2516- 2532, December (2005)
[3] M. Dyakonov and M. S. Shur, Consequences of Space Dependence of Effective Mass in Heterostructures, J. Appl. Phys. Vol. 84, No. 7, pp. 3726-3730, October 1 (1998)
[4] G. Simin, M. Shur and R. Gaska, SETI-0070: Semiconductor device with low-conducting field-controlling element App. No 13/396,059, November 19, 2013 as US Patent No. 8,586,997
[5] G. Simin, M. Gaevski, M. Shur, R. Gaska, Perforated Channel Field Effect Transistor, US patent 9,467,105, October 11, 2016
(Invited) Understanding Mg-Related Defects for Vertical GaN p-n Junction Structures Via p-Type Ion Implantation
Authors: Goorsky Mark S. , Liao Michael Evan , Huynh Kenny , Wang Yekan , Tweedie James , Sitar Zlatko , Collazo Ramon , Sierakowski Kacper , Bockowski Michal , Huang Xianrong 
Published: February 2024

Vertical GaN power devices have emerged to become promising candidates for next-generation high power applications due to superior material properties such as high breakdown voltage, low on-resistance, and high mobility compared to devices based on Si and SiC. GaN-based p-n junction switching devices enable higher voltage power with significantly higher efficiencies with added advantages of systems with reduced size and weight. A technological limitation of GaN, however, has been the inability to achieve high p-type doping in a planar, vertical device. Here, we will focus on recent developments to achieve high p-type efficiency though ion implantation, novel high temperature annealing schemes, and the importance of defects and morphology in native substrates and epitaxial layers.
Mg-implanted homoepitaxial GaN annealed at temperatures at or above 1400 °C eliminates the formation of inversion domains and leads to improved dopant activation efficiency. Extended defects in the form of inversion domains contain electrically inactive Mg after post-implantation annealing at temperatures as high as 1300 °C (one GPa N2 overpressure), which results in a low dopant activation efficiency. While residual defects, such as dislocation loops, still exist after annealing at and above 1400 °C, chemical analysis at multiple dislocation loops shows no sign of Mg segregation. Meanwhile, an overall decreasing trend in the dislocation loop size and density is observed after annealing at the higher temperatures and longer times. Earlier work addressing electrical measurements of these types of samples showed that annealing at ~1400 °C leads to a dopant activation efficiency that is an order of magnitude higher than that observed at 1300 °C. This work complements the earlier work by identifying the microscopic defects (inversion domains) which incorporate Mg, and points to the benefits, in terms of defect density and p-type dopant activation, of using higher temperature (1400 °C) annealing cycles to activate Mg in GaN.
Taking Advantage of the Operating Heterogeneities in PEMFC: Numerical Study with a Pseudo-3D Model
Authors: Cornet Marine , Morin Arnaud , Poirot-Crouvezier Jean-Philippe , Schott Pascal , Bultel Yann 
Published: February 2024

A Proton Exchange Membrane Fuel Cell (PEMFC) is an open system. Its operation is therefore inherently heterogeneous. Indeed, in a cell, electrochemical reactions do not take place homogeneously on the active surface area. It has already been pointed out that operating heterogeneities over a large cell active area can cause a decrease of performance and durability. In fact, studies to date have focused on the relation between operating heterogeneities and local degradation on the active surface area for a small selection of operating conditions.
The objective of our study is to find a way to control the current, temperature and water distributions by adjusting the operating conditions to, hopefully, optimize performance and improve durability. In order to define those control strategies, a better understanding of the heterogeneities for a wide range of operating conditions is necessary. To that end, a first numerical approach seems to be the most appropriate.
This numerical study is based on a pseudo-3D multi-physics and single-phase model of a large cell, developed on COMSOL Multiphysics®. One novelty of our study, from a methodological point of view, is the calibration of the model. Instead of calibrating the model with the electrochemical response of a large cell for some chosen operating conditions as per usual, it has been calibrated with the electrochemical response of a small cell (1.8 cm²), called differential cell, emulating local operating conditions on a larger cell. Three areas of the large cell were emulated for different operating conditions: inlet, middle and outlet. Once calibrated, the pseudo-3D model was used to calculate the distributions for 108 operating conditions, which were chosen from a full factorial design of experiment defined according to the automobile application of PEMFC. The statistical analysis of these simulation results will give the influence of operating conditions (gases pressure, the magnitude and orientation of the thermal gradient of the cooling fluid, gases temperature and relative humidity) on the current density, temperature and water distributions on the active surface area. These results will later be useful for the design of strategies for controlling heterogeneities, which will be finally tested on PEM stack.

Figure 1
In-Situ Spectroscopic Investigation of 3-D Gas Diffusion Electrodes for Fuel Cell Reactions in Half-Cell Setups
Authors: Jalan Rameshwori , Gomes Bruna Ferreira , Roth Christina 
Published: February 2024

Significant work has already been done in understanding proton exchange membrane fuel cells (PEMFC) over the past decades. In-situ visualization of the fuel-cell reactions has developed considerably and has also helped in understanding the challenges which still exist in various steps of electrochemical processing. Gas diffusion electrode half-cells have been widely promoted for fundamental catalysis research and when coupled with techniques like X-ray absorption spectroscopy (XAS) can be used for in-situ/operando studies of the reaction mechanisms in fuel cell reactions. This is particularly important to address the challenges in low temperature PEMFCs (eg. degradation of catalyst during durability tests) as well as high temperature PEMFCs (eg. poisoning of the Pt catalyst and low oxygen solubility in phosphoric acid).
In this presentation, an effort will be made to illuminate the catalytic characteristics during oxygen reduction reaction using in-situ XAS. The co-adsorption of H3PO3 and CO on platinum catalysts will be investigated using the Δµ XANES technique by following the signatures of different species adsorbed on the catalyst surface, and the Efix technique which follows the variation of signal intensity at a fixed energy near to the white line to follow the changes in Pt oxidation. During CO removal through cyclic voltammetry in the presence of 800 µM H3PO3 (as shown in the figure provided) it is possible to see a clear change in signal intensity around the potential of 250 mVAg/AgCl, which was associated with the oxidation of H3PO3 to H3PO4, since CO oxidation takes place at higher potentials (above 600 mVAg/AgCl). It is also interesting to note that when oxidizing H3PO3 to H3PO4, the platinum surface significantly reduced. With these experiments, it can be concluded that the Efix technique has a great potential to better understand what happens to Pt during the oxidation of H3PO3, as well as to identify more clearly the oxidation potential of this species, which is not easy to do based on the electrochemical data alone. Considering that this species is one of the main species responsible for the poisoning of the Pt catalyst during the operation of fuel cells, it is extremely important to understand the life cycle of this compound so that the operating conditions can be adapted to maximize the performance of the catalyst and develop new catalysts more resistant to poisoning by phosphorous species for HT-PEMFCs.
Acknowledgements:
Prof. Matthias Arenz from University of Bern, Martin Prokopand Tomàs Bystrom from University of Chemistry and Technology Prague, Michael Haumann, Freie Universität Berlin are gratefully thanked for their collaboration. German Research Foundation DFG Project ID RO 2454/19-1, the Bavarian Gender Equality Grant 2019-2021 (for Women in Academia), Petra III DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, P65 beamline (I-20211432) and KMC-3 beamline BESSY (Berlin,Germany).

Figure 1
MRI Study of the Influence of the Catalytic Layer on the Interfacial Water Transfer in PEMFC Membrane-Electrode Assemblies
Authors: Mrad Christine , Perrin Jean-Christophe , El Kaddouri Assma , Guendouz Laouès , Mozet Kévin , Dillet Jérôme , Lottin Olivier 
Published: February 2024

A better understanding of the limitations induced by decreasing platinum content in PEMFC membrane-electrode assemblies, both in terms of operation and aging of the electrodes and ionomer membrane is still needed. More specifically, more information and understanding of water transport across the membrane / electrode interface is required. Few experimental techniques can be used to measure the water interfacial resistance in these sandwiches as the method must be able to measure both the water flux through the assembly and the water content at the membrane interface. Among them, magnetic resonance imaging (MRI) can be effectively exploited by using surface coils to enhance the NMR signal and improve the quality of the measurement [1,2]. In the present study, MRI was used to distinguish the water diffusion resistance within thick Nafion-type PFSA membranes from the water transfer interfacial resistance. Measurement of the water profiles across the membrane allowed for accurate evaluation of the evolution of the diffusion coefficient as a function of water content. The determination of the water content at the interface and of the water flux through the membrane allowed the determination of the interface resistance for different hygrometry conditions imposed on both sides. The experiments were then repeated on membrane / electrode and electrode / membrane / electrode samples to evaluate the impact of the electrode layer. Our results show a strong evolution of the interfacial resistance as a function of the air humidity while the influence of the electrode does not seem to be preponderant.

Figure

(left): NMR experimental cell containing a Nafion N1110 sample fed by two streams of humid air with controlled flow rate and relative humidity (RH).

(right): examples of water content () profiles measured by MRI (6 µm spatial resolution) in different RH conditions.

References

[1] Ouriadov, A. et al. J. Magn. Reson. 169(1), 174–186 (2004)
[2] Klein, M. et al. ECS Transactions, 58(1), 283-289 (2013)

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Impedance Study of the Effect of Cell Compression on PEMFC Under Various Oxygen Supply Conditions
Authors: Tanaka Akihisa , Nagato Keisuke , Weber Andre , Tomizawa Morio , Nakao Masayuki 
Published: February 2024

Cell compression impacts the performance of polymer electrolyte membrane fuel cells (PEMFCs). A previous study has reported a trade-off between mass transport and contact resistances from cell compression [1]. Our study focuses on how the compression pressure affects polarization resistance under various oxygen partial pressure conditions. Without hot pressing the gas diffusion layers, a membrane electrode assembly with an electrode area of 1 cm2 was set in a housing in which the compression pressure could be adjusted [2]. Impedance spectra were measured at 0.7 A/cm2 under various oxygen partial pressure conditions. Figure 1 shows that polarization resistance decreases with increasing compression pressure under low compression pressure conditions, and conversely increases under high compression pressure conditions. The change in polarization resistance is more pronounced under low oxygen partial pressure conditions. In this contribution, the effect of cell compression on the different polarization processes will be discussed, considering the impact of compression pressure on catalyst layer thickness and porosity.
References
[1] N. K. Shrivastava et al., Int. J. Energy Res., 44, 370–385 (2020).
[2] M. Heinzmann et al., J. Power Sources, 402, 24–33 (2018).

Figure 1