The Electrochemical Society hereby retracts the above article. Following concerns raised by a member of the scholarly community, the journal conducted a review and determined that this article constitutes redundant publication. The ECS Transactions paper shares an identical title and substantial overlap in content with an earlier article ACS Nano 2017, 11, 2, 2103–2114, which was not cited within the ECS Transactions article. Skorobogatiy, M., et al., “Piezoelectric Micro- and Nanostructured Fibers Fabricated from Thermoplastic Nanocomposites Using a Fiber Drawing Technique: Comparative Study and Potential Applications,” ACS Nano, published February 14, 2017. In accordance with Committee on Publication Ethics (COPE) guidance, this retraction is issued to correct the scholarly record and inform readers of the prior publication. The journal and the corresponding author agree that retraction is in the best interest of the scholarly record.
We fabricated 400°C-annealed TiN/Hf x Zr 1−x O 2 (HZO)/TiN metal–ferroelectric–metal (MFM) capacitors using H 2 O and O 2 plasma as oxidant gases of thermal (TH) and plasma-enhanced atomic layer deposition (PE-ALD), respectively, for HZO films. The PE-ALD film formed a more ferroelectric orthorhombic phase compared with the TH-ALD case. Therefore, the MFM capacitor with the PE-ALD film showed higher remanent polarization and dielectric constant. For the PE-ALD case, moreover, an oxygen-rich interfacial layer (O-rich-IL) was formed between the HZO film and TiN-bottom electrode during the ALD process. Thus, the MFM capacitor with the PE-ALD film showed less degradation of switching polarization during field cycling compared with the TH-ALD case, because an O-rich-IL should prevent the interface reaction and formation of additional oxygen vacancies in the PE-ALD film during field cycling. Based on these results, it is important to consider the selection of an ALD oxidant gas for the fabrication of HZO-based MFM capacitors.
An ionic clathrate hydrate composed of tri-n-butylbenzyl-phosphonium chloride has been investigated from the viewpoint of phase equilibrium (temperature-composition) relations in comparison with an ionic clathrate hydrate with tri-n-butyl(cyclohexylmethyl)phosphonium bromide. The highest dissociation temperature of the ionic clathrate hydrates composed of tri-n-butylbenzylphosphonium chloride and tri-n-butyl(cyclohexyl-methyl)phosphonium bromide were 274.4 ± 0.1 K and 276.0 ± 0.1 K, respectively at the atmospheric pressure. The dissociation enthalpy of tri-n-butylbenzyl-phosphonium chloride ionic clathrate hydrate was 192 ± 3 kJ·kg−1. These results allow us to suggest that controlling steric structures in the guest compounds might be one of the options for tuning the equilibrium temperatures of ionic clathrate hydrates.
This paper investigates surface damage caused by physical cleaning processes during semiconductor manufacturing. The study focuses on various materials, including FDSOI wafers and polymer films, subjected to high-velocity sprays and cryogenic cleans. Thanks to the supplier process performances and quality control, FDSOI films do not present any specific concern linked with this failure mode. This latter can be observed on whatever films exposed to aggressive physical cleans and the wafers are cleverly used as a test vehicle to evidence surface defects with a revelation method using a wet etchant. It enables the detection of nano-cracks and other damages. Same defects are observed in bulk silicon wafers, and solutions exist to avoid these damages. Different spray types are compared, highlighting the impact of droplet energy distribution on surface integrity. Additionally, a direct characterization method using polymer films is developed to assess physical cleaning damage. The findings emphasize the importance of optimizing cleaning processes to balance defect removal efficiency and surface preservation. Emerging cleaning solutions like polymer coat and peel methods are also discussed for their potential to offer high cleaning performance with minimal surface damage.
We investigated the oxygen evolution behavior of nine types of commercially available Ni-containing alloys in a NaOH–KOH hydrate melt. The oxygen overpotential of all Ni-containing alloys was lower than that of the Ni electrode (453 mV) at 500 mA cm–2 and 150°C. The Kovar (Fe–Ni–Co alloy) electrode exhibited the lowest oxygen overpotentials of 280 mV at 150°C and 227 mV at 200°C. The Tafel slope of the Kovar electrode at 150°C was 63 mV dec–1, which was slightly lower than that of the Ni electrode (67 mV dec–1). The upper limit of the Tafel region for the Kovar electrode was extended to a higher current density of 300 mA cm–2 compared to that for the Ni electrode (100 mA cm–2) at 150°C. It further extended to 1000 mA cm–2 at 200°C, indicating that highly efficient water electrolysis can be expected.
The performance of an HBT is primarily influenced by 1D dopant profile obtained by CVD epitaxy. Typically, three epitaxial layers are required to construct an HBT: the collector, the intrinsic base, and the emitter. Collector layer can be grown by either NSEG or selective epitaxy. While the NSEG process is cost effective, it results in autodoping. Switching to selective epitaxy can mitigate autodoping but must be controlled to minimize faceting. The intrinsic base is critical to device performance, with boron positioning being a key factor. Incorporating substitutional carbon atoms into the SiGe lattice significantly reduces boron diffusion. By switching from SiH4 to Si2H6, three times more substitutional carbon incorporation in SiGe without interstitial C atoms at 550 °C is achieved. Below 600 °C, the co-flow approach is ineffective, necessitating a cyclic deposition-etch (CDE) approach to maintain selectivity. Comparisons between CDE and single deposition-etch (DE) approaches show that CDE degrades the monocrystalline SiGeC:B layer, resulting in high RMS roughness and degraded morphology. In contrast, the DE approach shows promising results with lower RMS roughness and no significant morphological degradation. The last epitaxial layer discussed is the emitter. Current fabrication methods involve non-selective Si:As deposition at growth temperatures above 600 °C, resulting in polycrystalline Si:As deposition on dielectrics and monocrystalline Si:As growth on silicon. A novel process developed at 550 °C using Si2H6 as silicon precursor yields monocrystalline emitter by amorphous deposition on dielectrics followed by solid phase epitaxial regrowth. However, this process exhibits TED of arsenic, making it currently not viable.
Spin qubits based on quantum dots built on Si/SiGe heterostructures are a leading contender for achieving large-scale quantum computation. The quality of quantum dots fabricated on these heterostructures is directly connected to the quality of the 2D electron gas (2DEG) confined in the strained Silicon quantum well. The properties of such 2DEG can be readily assessed using Hall bar-shaped field-effect transistors (HB-FETs) and magneto-transport measurements, enabling a faster feedback loop for heterostructure optimization process. In this work, we present our recent progress in enabling silicon-based quantum computation by demonstrating fundamental components for 2DEG characterization, all developed in IHP's 200 mm BiCMOS pilot line. We demonstrate fully functional HB-FETs on Si/SiGe heterostructures grown on 200 mm silicon wafers, showcasing state-of-the-art 2DEG with maximum carrier mobility exceeding 300,000 cm²/Vs and a percolation threshold of 6.3×1010 cm⁻². These results will help advance spin qubit research based on Si/SiGe heterostructures.
In polymer electrolyte fuel cells (PEFCs), Pt catalyst particle growth due to load fluctuation potential cycling, and oxidative corrosion of the carbon support due to start-stop potential cycling are important issues for cathode electrocatalysts affecting their durability. Here, we incorporate tantalum into the electrocatalyst to improve both the catalytic activity and durability. This is achieved via self-assembly of a nanocomposite electrocatalyst via dealloying to form Pt-Co alloy and TaOx support nanoparticles. Half-cell electrochemical measurements confirm that the catalytic activity and durability are significantly improved by the formation of this nanocomposite electrocatalyst.
When assembling a proton exchange membrane fuel cell (PEMFC), a clamping pressure is applied to all the components. The catalyst layer (CL) and gas diffusion layer (GDL) are compressed to the gasket thickness by the clamping during assembly. This compression increases the conductivity of the protons and electrons while reduces the size of the pores, which are the removal channels for the generated water and the diffusion channels for the fuel and air gases. We evaluated the effect of the CL compression prepared with the Marimo-like carbon (MC) regarding the I-V performance. The MC is a higher order structure of carbon fibers. The maximum power density was the highest (237 mW cm-2) at the 22% compression ratio. The excessive compression was suggested to have a higher effect on blocking the diffusion channels of the fuel and air gases than on improving the conductivity.
Since 2000, the increased possibility of nomadizing objects via the Internet of Things has spread to all sectors of society. This field initially experienced exponential growth, which is currently accelerating with the arrival of new applications such as cloud storage or artificial intelligence. All the associated electronics-based equipment needs to be supplied with electrical power. Transparency on the user's side overshadows the real energy consumption, which is growing exponentially, that is not physically acceptable in the long term. After summarizing the background to the challenges of the digital world, this paper examines various proposals for improving electronics, both technologically and architecturally, involving transistors, devices and thin-film circuits. These include stacking techniques, the introduction of wide-bandgap semiconductors, new flexible technologies, and new circuits based on analog and asynchronous approaches. An obvious resulting need concerns human resources with new skills, to which this document pays particular attention in the final section.
The advancement of CMOS technology nodes demands increasingly complex device architectures. In this frame, the epitaxial deposition of complicated SiGe/Si multistacks presents a significant technology challenge required to enable such cutting-edge devices. This work presents the characterization of defect-free multistacks featuring SiGe layers with two possible Ge concentrations and incorporating either two or six stacked Si nanosheets. Our comprehensive analysis reveals good matching with the nominal structures and demonstrates remarkable repeatability of the Si channels. Furthermore, the multistacks exhibit ideal surface morphology, crucial for subsequent processing steps. Notably, the study also highlights optimal wafer-to-wafer repeatability, a key factor in ensuring consistent performance across large-scale production.
The optical properties of the multilayered staggered SiGe nanodots (NDs) embedded in the Si spacers fabricated at varying Si growth temperatures are clarified in conjunction with the effect of strain by Photoluminescence (PL) and Raman spectroscopy. We found that compressive strain is induced in the SiGe NDs, with higher growth temperatures of the Si spacer resulting in stronger compressive strain. PL spectra indicate that the higher growth temperature leads to a wider bandgap. This transition energy behavior is caused by not only the strain in the SiGe NDs but also the Ge segregation. Furthermore, luminescence from the SiGe NDs was observed along with luminescence originated at the Si/SiGe interface in the SiGe NDs with a small dot size. This phenomenon was caused by the small energy difference of the conduction-band minima between the SiGe NDs and the tensile-strained Si spacers and the small volume of the tensile-strained Si spacers.
The crystal phase heterojunction (CPHJ) is essentially a new type of heterojunction without misfit dislocations and lattice relaxation. The transistor structure using the CPHJ could significantly impact the transistor technologies. However, CPHJ has difficulty in fabricating a gate structure that modulates the electric field normal to the the CPHJ. Here, we report on the selective-area growth of WZ-InP NWs for InP NWs and demonstration of vertical gate-all-around transistors using the InP CPHJ.
Studies on “poor” protic ionic liquids, having proton-transfer strength ΔpKa = 0-6, have shown the need to make corrections to the Fuoss equation for prediction of ΔGioniz and Kioniz for ion-pairing equilibria in these systems. Recent work built empirical functions to replace the Fuoss equation for this ΔpKa region, based on ab initio ion-pairing energies, but the functions did not perform well at the higher end of this range. Here, we extend the study to the range ΔpKa = 6-18, examining hypothetical mixtures of trimethylamine (TEA) with acids from weak (CH3COOH) to quite strong (CF3SO3H). Ab initio pairing energies were obtained for these systems, followed by refitting. Preliminary comparisons with experimental ionicities appear to show inaccuracies in the ab initio dataset, not in the fitting function form. Future work is planned to include dataset shifts, empirical or theoretical, to allow the goal of a predictive function for ionicity as a function of ΔpKa and acid:base mixing ratio.
Wet ALE (atomic layer etch) processes are emerging as an important alternative to standard ALE processes in semiconductor manufacturing. Here we present a model for simulating an idealized wet ALE process that includes both chemical reactions and liquid flow in order to predict the amount of material etch, how much of the etching is true ALE vs continuous etch, and its uniformity across the wafer. This model is applied to both a simple test flow cell and flow across a spinning wafer in a typical wet single wafer process. Results show that etch amount and uniformity depends on timing of the dispense steps, flow parameters, and the kinetics of the specific chemical reactions.
We present a metrology for analyzing the spatial distribution and local chemistry of in-situ dopants using Atom Probe Tomography (APT). Our approach integrates a 'local composition method' with a Kolmogorov-Smirnov test on a 3D APT dataset to evaluate spatial inhomogeneity. This methodology was applied to a nanometer scale in-situ highly boron-doped silicon germanium layer. By subdividing the dopant-dopant local composition distribution into three, its influence on the localized chemical environment was determined. Our findings reveal an inhomogeneous spatial distribution for the dopant and the Si/Ge atoms. Our results demonstrate the potential for linking at an atomic-scale the epitaxial growth conditions of dopants and the matrix elements to a device performance.
Since reports in the mid-1990s on metal-induced pitting on a Si surface in microelectronics, much attention has been paid to the positive use of corrosion of a semiconductor surface loaded with a metallic catalyst in solutions, known as metal-assisted chemical etching. This paper describes two novel modes of catalyst-assisted etching. The first involves the formation of nano trenches along the atomic step edges of a Si(111) surface with the help of self-assembled metallic nanowires, enabling the separation of neighboring terraces. The second discusses the science and application of nanocarbon-assisted etching, free from noble metals, of a Ge surface in water.
A selective low-temperature Si:As (LT-SiAs) process is presented which utilizes cyclic deposition-etch (CDE) at <450oC. Selectivity against SiN and SiOx dielectrics and crystallinity are confirmed on gate-all-around (GAA) patterned structures. Hall measurements on blanket wafers show a resistivity minimum of 0.42 mΩ-cm at ~1.7% As for selective LT-SiAs. SIMS profiles of P and As diffusion into intrinsic Si (i-Si) for LT-SiP/LT-SiAs/i-Si and LT-SiP/i-Si stacks show >2× benefit of using LT-SiAs spacers to minimize dopant diffusion for as-deposited, soak-annealed and spike-annealed samples. Improvement is attributed to relatively limited diffusivity of As in Si versus P and the lower As concentration needed for LT-SiAs layer to achieve minimum resistivity relative to LT-SiP (~3%). Lastly, a comparison of LT-SiAs and high-temperature Si:As (HT-SiAs) shows a ~2× reduction of As diffusion into i-Si for LT-SiAs at length scales of >10nm. [1]: E. Rosseel et al. ECS Trans. 98, 37 (2020). Figure 1
Highly porous nitrogen and phosphorus dual-doped carbon (NPC) was synthesized using acetylene black as a carbon source in two steps: (1) solid–gas mechanochemical treatment to prepare nitrogen-doped carbon (NC), (2) heat treatment to dope the NC with phosphorus. X-ray photoelectron spectroscopy and N2 gas adsorption analysis revealed that the solid–gas mechanochemical treatment using a ball mill incorporated nitrogen atoms into the carbon network and increased the pore volume and surface area. Furthermore, the resulting NC exhibited enhanced reactivity with ammonium dihydrogen phosphate, which was used as a phosphorus source, upon heat treatment. The phosphorus content in NPC synthesized by two-step mechanochemical and heat treatments reached 1.91 at%, a 14-fold increase compared to that of phosphorus-doped carbon synthesized by heat treatment. The NPC exhibited higher electrocatalytic activity for the oxygen reduction reaction than NC, suggesting that the additional phosphorus doping into NC can improve its electrocatalytic performance.
