Si Passivation Research Articles

Study of a Novel W–Si Passivation Process for Lithium Copper Foils: Rational Utilization of the Polyhydroxy Structure Based on Sodium Gluconate

Study of a Novel W–Si Passivation Process for Lithium Copper Foils: Rational Utilization of the Polyhydroxy Structure Based on Sodium Gluconate

Study on the corrosion resistance of new reticulated organic polymerized film on copper foil surface

In response to the policy of energy saving and emission reduction, the field of new energy vehicles is booming, and along with it, the technical requirements for lithium-ion batteries are becoming more and more stringent. Electrolytic copper foil, as the anode collector material of lithium batteries, seriously affects the progress of lithium technology, and electrolytic copper foil with high corrosion and oxidation resistance is the key to ensuring its performance. Experimentally, the BTA-Si passivation film layer was constructed on the surface of electrolytic copper foil by compounding benzotriazole (BTA) and silane coupling agent (JH-M902) with an easy-to-operate chemical impregnation method. The results of electrochemical analysis and characterization showed that JH-M902 hydrolyzed to produce Si-OH and then dehydrated and polymerized with Cu-OH to form Si-O-Cu or partially dehydrated and polymerized with each other to form Si-O-Si, which formed an intertwined organic reticulation film on the electrolytic copper foil. At the same time, BTA and copper oxides form a BTA-Cu complex, which is adsorbed and perpendicular to the copper foil. The combination of the two can not only make up for the gap in the organic mesh layer but also anchor the mesh layer, thus inhibiting its desorption in harsh external environments. Immersed in 3.5 wt% NaCl, the self-corrosion current density (icorr) of BTA-Si passivation film is only 1.115 × 10−7 A/cm2, and the corrosion inhibition rate as high as 99.56 %, which is far better than that of the single BTA and Si passivation film. In addition, the BTA-Si passivation film is smooth, dense, and thin, which significantly improves the corrosion resistance of copper foil without changing its original structure.

Observations of GRB 221009A by the MAVEN-SEP Instrument at Mars

We report on the detection of the Brightest Of All Time (the BOAT) gamma-ray burst (GRB) 221009A by the MAVEN Solar Energetic Particle (SEP) silicon (Si) detectors. The SEP instrument on board the MAVEN spacecraft at Mars is designed to measure charged particle fluxes and energies. In this work, we show that the SEP Si detectors have detected populations of secondary charged particles and low-energy primary photons from the GRB. Our analysis relies on a series of simplified Geant4 Monte Carlo simulations. We show that electromagnetic and hadronic interactions between the GRB photons and the spacecraft’s passive material and Si detectors produced the detected secondary particles.

Crystalline Si Surface Passivation with Nafion for Bulk Defects Detection with Electron Paramagnetic Resonance.

In monocrystalline Si (c-Si) solar cells, identification and mitigation of bulk defects are crucial to achieving a high photoconversion efficiency. To spectroscopically detect defects in the c-Si bulk, it is desirable to passivate the surface defects. Passivation of the c-Si surface with dielectrics such as Al2O3 and SiNx requires deposition at elevated temperatures, which can influence defects in the bulk. Herein, we report on the passivation of different Czochralski (Cz) Si wafer surfaces by an organic copolymer, Nafion. We test the efficacy of the surface passivation at temperatures ranging from 6 to 473 K to detect bulk defects using electron paramagnetic resonance (EPR) spectroscopy. By comparing with state-of-the-art passivation layers, including Al2O3 and liquid HF/HCl, we found that at room temperature, Nafion can provide comparable passivation of n-type Cz Si with an implied open-circuit voltage (iVoc) of 713 mV and a recombination current prefactor J0 of 5 fA/cm2. For p-type Cz Si, we obtained an iVoc of 682 mV with a J0 of 22.4 fA/cm2. Scanning electron microscopy and photoluminescence reveal that Nafion can also be used to passivate the surface of c-Si solar cell fragments scribed from a solar cell module by using a laser. Consistent with previous studies, analysis of the EPR spectroscopy data confirms that the H-terminated surface is necessary, and fixed negative charge in Nafion is responsible for the field-effect passivation. While the surface passivation quality was maintained for almost 24 h, which is sufficient for spectroscopic measurements, the passivation degraded over longer durations, which can be attributed to surface SiOx growth. These results show that Nafion is a promising room-temperature surface passivation technique to study bulk defects in c-Si.

Calibration of second harmonic generation technique to probe the field-effect passivation of Si(100) with Al2O3 dielectric layers

Optical second harmonic generation (SHG) can be employed to characterize the passivation quality of semiconducting material interfaces. The interface electric field (EDC) related to the existing charges at and near the interface, including the fixed oxide charges Qox, gives rise to the electric field induced second harmonic phenomenon. In this paper, we calibrate the SHG response for EDC measurement, using Al2O3/SiO2/Si(100) samples with different Qox. To perform this calibration, SHG and capacitance-voltage measurements (to access the electrical field of the samples) were made. The experimental results match well the simulated calibration curve, proving the potential of the SHG as stand-alone characterization technique for dielectric stacks on Si.

Comparative Passivation of Si(100) by H2 and D2 Atmospheres under Simultaneous Xe+ Bombardment: An X-ray Photoelectron Spectroscopy Analysis.

This study presents a comparison of H2 and D2 passivation on Si(100) under simultaneous Xe+ ion bombardment. The impact of Xe+ ions causes significant damage to the substrate surface, leading to an increase in H2 (D2) retention as Si-H (Si-D) bonds. The ion bombardment conditions are precisely controlled using a Kaufman ion gun. The atomic concentrations on the surface of the sample were investigated by quasi-in situ X-ray photoelectron spectroscopy. A simple methodology is employed to estimate the H (D) chemical concentration and the cover ratio of the sample, with regard to the oxygen concentration through residual water chemisorption present in the vacuum vessel. Differences in passivation are expected when using H2 or D2 atmospheres because their retained scission energies and physisorption properties differ. The results indicate an increase of the sticking coefficient for D2 and H2 under the ion bombardment. It is also found that the flux of H2 (D2) impinging on the surface contributes to play an important role in the whole process. Finally, a model is proposed to describe the phenomenon of the passivation of Si under Xe+ ion bombardment in the presence of H2 (D2).

Chemical contributions to silicon anode calendar aging are dominant over mechanical contributions

Silicon (Si) anodes are a promising candidate for increasing the energy density of lithium (Li)-ion batteries for electric vehicles. However, they have recently been identified as having poor calendar life that is insufficient for commercial needs, in addition to the well-known issue of their poor cycle life resulting from large volume expansion. Here, a specially designed protocol with variable rest periods between intermittent cycling is used to evaluate the impact of the mechanical disruption of Si and solid electrolyte interphase (SEI) from cycling on calendar aging measurements. Si was found to undergo more mechanical degradation during calendar aging with intermittent cycling than graphite. However, Si anode capacity fade was still dominated by time, especially for rest periods greater than or equal to 1 month between cycling. Postmortem dQ/dV half-cell analysis indicated this was mainly due to Li inventory loss and an increase in electrode resistance. Isothermal microcalorimetry further demonstrated that Si passivation is more disrupted than graphite passivation with intermittent cycling and suggested that there may be a chemical buildup of a detrimental species in the electrolyte, leading to a large spike in heat after the Si and SEI are disrupted by cycling.

Fabrication of a self-aligned multi-waveguide-layer passive Si3N4/SiO2 photonic integrated circuit for a 3-D optical phased array device

Most traditional PICs (photonics integrated circuits) are based on a single-waveguide-layer configuration, which takes advantage of the mature fabrication process from the EIC (electronic integrated circuits) industry; but in the meantime, this configuration also limits the performance of PICs in applications such as OPA (optical phased array) devices. We have proposed a multi-waveguide-layer 3-D (3 dimensional) OPA device and demonstrated its unique advantage in broadband high efficiency. In this paper, we present the fabrication process of the proposed 3-D OPA in detail. By developing the fabrication process with a single lithography step, we address the two potential issues in a multi-waveguide-layer PIC: the alignment between layers; and the accurate spacing control between layers. The detailed considerations of processes are also elaborated, especially in the PR (photoresist) exposure and etching.

Structural and tribological behaviours of silicon doped amorphous carbon films

We report on the structural evolution and low-friction behaviour of silicon (Si) doped amorphous carbon (a-C) films. Si-doped a-C films were fabricated by controlling the magnetron Si target currents under an electron cyclotron resonance (ECR) plasma system. Structural analysis indicated that Si atoms doped into the a-C lattice preferentially replaced certain sp3 C atoms, and subsequently formed bonds with other sp3 C atoms. Nanoindentation and nanoscratch tests showed that the Si-doped a-C films had hard surfaces with a hardness of approximately 24 GPa and a scratch depth of 40–60 nm. Ball-on-disk tribological evaluations further showed that these films exhibited low-friction behaviour, with a minimal friction coefficient of 0.02. Detailed transfer film characterisation revealed the formation of rich oxide and graphene structures within the stable contact-sliding interface of the Si-doped a-C film. The low friction mechanism was summarized as H–H interactions from the surface terminal passivation of Si dangling bond with hydroxide (-OH) or hydrogen (-H) groups and π*-π* interactions occurring between the graphene layers co-reducing the friction force. These findings shed light on the significance of doped Si atoms in the structural design and low-friction applications of carbon films.

Silicon surface passivation of industrial n-type CZ Si (111) by Al2O3 layers deposited by thermal ALD process for application in carrier selective contact solar cells

Silicon surface passivation of industrial n-type CZ Si (111) by Al2O3 layers deposited by thermal ALD process for application in carrier selective contact solar cells

Mitigation of shunt in poly-Si/SiO passivated interdigitated back contact monocrystalline Si solar cells by self-aligned etching between doped fingers

Mitigation of shunt in poly-Si/SiO passivated interdigitated back contact monocrystalline Si solar cells by self-aligned etching between doped fingers

The Microstructure of Underdense Hydrogenated Amorphous Silicon and its Application to Silicon Heterojunction Solar Cells

The application of thin underdense hydrogenated amorphous silicon (a‐Si:H) films for passivation of crystalline Si (c‐Si) by avoiding epitaxy in silicon heterojunction (SHJ) solar cell technology has recently been proposed and successfully applied. Herein, the microstructure of such underdense a‐Si:H films, as used in our silicon heterojunction solar cell baseline, is investigated mainly by Raman spectroscopy, effusion, and secondary ion mass spectrometry. In H effusion experiments, a low‐temperature (near 400 °C) effusion peak which has been attributed to the diffusion of molecular H2 through a void network is seen. The dependence of the H effusion peaks on film thickness is similar as observed previously for void rich, low substrate‐temperature a‐Si:H material. Solar cells using underdense a‐Si:H as i1‐layer with a maximum efficiency of 24.1% are produced. The passivation quality of the solar cells saturates with increasing i1‐layer thickness. The fact that with such underdense material combined with a following high‐quality i2‐layer, instead of only high‐quality a‐Si:H with a low defect density direct on the c‐Si substrate, good passivation of c‐Si solar cells is achieved, which demonstrates that in the passivation process, molecular hydrogen plays an important role.

Photovoltaics literature survey (no. 182)

Photovoltaics literature survey (no. 182)

Characteristics of Adults Hospitalized for a Major Depressive Disorder: Results from the Multicenter OASIS-D Study

IntroductionMajor Depressive Disorder (MDD) is one of the most common mental illnesses worldwide and is strongly associated with suicidality. Commonly used treatments for MDD with suicidality include crisis intervention, oral antidepressants (although risk of suicidal behavior is high among non-responders and during the first 10-14 days of the treatment) benzodiazepines and lithium. Although several interventions addressing suicidality exist, only few studies have characterized in detail patients with MDD and suicidality, including treatment, clinical course and outcomes. Patient Characteristics, Validity of Clinical Diagnoses and Outcomes Associated with Suicidality in Inpatients with Symptoms of Depression (OASIS-D)-study is an investigator-initiated trial funded by Janssen-Cilag GmbH.ObjectivesFor population 1 out of 3 OASIS-D populations, to assess the sub-population of patients with suicidality and its correlates in hospitalized individuals with MDD.MethodsThe ongoing OASIS-D study consecutively examines hospitalized patients at 8 German psychiatric university hospitals treated as part of routine clinical care. A sub-group of patients with persistent suicidality after >48 hours post-hospitalization are assessed in detail and a sub-group of those are followed for 6 months to assess course and treatment of suicidality associated with MDD. The present analysis focuses on a preplanned interim analysis of the overall hospitalized population with MDD.ResultsOf 2,049 inpatients (age=42.5±15.9 years, females=53.2%), 68.0% had severe MDD without psychosis and 21.2% had moderately severe MDD, with 16.7% having treatment-resistant MDD. Most inpatients referred themselves (49.4%), followed by referrals by outpatient care providers (14.6%), inpatient care providers (9.0%), family/friends (8.5%), and ambulance (6.8%). Of these admissions, 43.1% represented a psychiatric emergency, with suicidality being the reason in 35.9%. Altogether, 72.4% had at least current passive suicidal ideation (SI, lifetime=87.2%), including passive SI (25.1%), active SI without plan (15.5%), active SI with plan (14.2%), and active SI with plan+intent (14.1%), while 11.5% had attempted suicide ≤2 weeks before admission (lifetime=28.7%). Drug-induced mental and behavioral disorders (19.6%) were the most frequent comorbid disorders, followed by personality disorders (8.2%). Upon admission, 64.5% were receiving psychiatric medications, including antidepressants (46.7%), second-generation antipsychotics (23.0%), anxiolytics (11.4%) antiepileptics (6.0%), and lithium (2.8%). Altogether, 9.8% reported nonadherence to medications within 6 months of admission.ConclusionsIn adults admitted for MDD, suicidality was common, representing a psychiatric emergency in 35.9% of patients. Usual-care treatments and outcomes of suicidality in hospitalized adults with MDD require further study.Disclosure of InterestNone Declared

Photovoltaic Performance of Si and SiGe Surfaces Sonochemically Activated in Dichloromethane

Aims: To activate Si and SiGe surfaces by employing the sonochemical treatment at different operating frequencies in dichloromethane to improve the surface photovoltage signal. Background: To produce integrated electronic devices, one needs to achieve low surface and interface trap densities. In this respect, placing a passivating thin layer on Si and Ge surfaces, which saturates the electronic levels of traps and therefore affects the carrier recombination velocities at the surface, is of great interest. Objective: To demonstrate that the effectiveness of the treatment of Si and SiGe surfaces depends on the ultrasonic frequency used. Methods: Photovoltaic transients, electron microscopy, EDX spectroscopy. Result: The surface photovoltage (SPV) decay curves can be divided into rapid (τ_1) and slow (τ_2) components. The sonication effect on the SPV is different for the treatment done at about 25 and 400 kHz. The SPV signal in Si gradually increases with increasing lower-frequency sonication time, whereas the SPV enhancement on SiGe is somewhat smaller. Increasing the sonication time increases the amplitude of the τ_2 component in Si. In SiGe, the lower-frequency sonication quenches the τ_2 component yielding a nearly single-exponential decay form. This trend is even more pronounced at the higher-frequency sonication. Conclusion: The sonochemical treatments greatly intensify the formation of CxHy–Si and CxHy–Ge bonds on Si and Si1-xGex surfaces, resulting in increased SPV signals and prolonged SPV decay times. These results demonstrate that sonochemical treatment is a more effective technique to obtain stable highly passivated Si and Si1-xGex surfaces in comparison with wet chemical treatments in hydrocarbon solutions.

Passivation of macroporous Si using sputtered TiN coating for on-chip energy storage

Porous silicon is an interesting material for integrated on-chip energy storage in microdevices. But the formation of an efficient and stable porous silicon-based supercapacitor electrode is challenging owing to its poor electrical conductivity and extreme chemical reactivity. To overcome these challenges, we demonstrate the usage of highly conducting and chemically stable TiN coating for surface passivation of macroporous p-type and n-type silicon. For p-type porous silicon having uniformly distributed 9 μm long and 3–4 μm wide cylindrical pores, the sputtered TiN coating enables high areal capacitance of 8.6 mF cm−2 at a current density of 0.1 mA cm−2 along with exceptional cyclic stability. The all-solid-state symmetric supercapacitor based on TiN passivated porous silicon electrodes sandwiched with Na2SO4-PVA hydrogel electrolyte exhibits a wide cell voltage of 2 V. The high energy density of 1.96 μWh cm−2 is evaluated at a power density of 200 μW cm−2 which is promising for integrated energy storage.

Stainless Steel-Like Passivation Inspires Persistent Silicon Anodes for Lithium-Ion Batteries.

Passivation of stainless steel by additives forming mass-transport blocking layers is widely practiced, where Cr element is added into bulk Fe-C forming the Cr2 O3 -rich protective layer. Here we extend the long-practiced passivation concept to Si anodes for lithium-ion batteries, incorporating the passivator of LiF/Li2 CO3 into bulk Si. The passivation mechanism is studied by various ex situ characterizations, redox peak contour maps, thickness evolution tests, and finite element simulations. The results demonstrate that the passivation can enhance the (de)lithiation of Li-Si alloys, induce the formation of F-rich solid electrolyte interphase, stabilize the Si/LiF/Li2 CO3 composite, and mitigate the volume change of Si anodes upon cycling. The 3D passivated Si anode can fully retain a high capacity of 3701 mAh g-1 after 1500 cycles and tolerate high rates up to 50C. This work provides insight into how to construct durable Si anodes through effective passivation.

Stainless Steel‐Like Passivation Inspires Persistent Silicon Anodes for Lithium‐Ion Batteries

AbstractPassivation of stainless steel by additives forming mass‐transport blocking layers is widely practiced, where Cr element is added into bulk Fe−C forming the Cr2O3‐rich protective layer. Here we extend the long‐practiced passivation concept to Si anodes for lithium‐ion batteries, incorporating the passivator of LiF/Li2CO3 into bulk Si. The passivation mechanism is studied by various ex situ characterizations, redox peak contour maps, thickness evolution tests, and finite element simulations. The results demonstrate that the passivation can enhance the (de)lithiation of Li‐Si alloys, induce the formation of F‐rich solid electrolyte interphase, stabilize the Si/LiF/Li2CO3 composite, and mitigate the volume change of Si anodes upon cycling. The 3D passivated Si anode can fully retain a high capacity of 3701 mAh g−1 after 1500 cycles and tolerate high rates up to 50C. This work provides insight into how to construct durable Si anodes through effective passivation.

Dielectric Front Passivation for Cu(In,Ga)Se2Solar Cells: Status and Prospect

Cu(In,Ga)Se2(CIGSe) solar cells are among the most efficient thin‐film solar cells on lab scale. However, this thin‐film technology has relatively large upscaling losses for commercial technology. To tackle this, paradigm shifts are proposed that allow for simpler, cost‐effective, and efficient CIGSe solar cells. Front passivation using dielectric layers is one of the options being investigated as this is widely used in Si technology. Research on front passivation for CIGSe is in an early stage and no improvements are made yet. A close comparison with silicon technology is made to understand why it seems to be more difficult for CIGSe solar cells. In general, chemical passivation is less effective, resulting in higher interface defect densities than seen for Si. Also, field‐effect passivation requires positive charges, which have not been implemented yet on the CIGSe front surface. Finally, for Si passivation, often a high‐temperature annealing step is applied, which is not possible for CIGSe. It is proposed to apply a dielectric tunneling layer with positive fixed charges in combination with an electron transport layer to move forward. A list of potential dielectric layers that could be suitable for CIGSe is provided.

O2 Oxidation and Sublimation Kinetics of Single Silicon Nanoparticles at 1200–2050 K: Variation of Reaction Rates, Evolution of Structural and Optical Properties, and the Active-to-Passive Transition

Sublimation and O2 etching kinetics for a series of individual silicon (Si) nanoparticles (NPs) were studied for NP temperatures (TNP) from 1200 to 2050 K using a single NP mass spectrometry technique. Sublimation was significant for TNP > 1700 K, with rates reasonably well fit to Arrhenius kinetics but evolving, particularly during initial heating. O2 etching efficiencies varied from NP-to-NP and with changing TNP, but they also evolved dramatically over time. For TNP ≤ 1500 K, NPs were observed to passivate after losing 30–50% of the initial NP mass. At higher TNP, etching efficiency decreased over time but never passivated. Interestingly, bulk Si passivation has not been observed for the range of TNP and O2 pressures used here, and a model was developed to test the effects of several NP-specific mechanistic parameters on both the initial and time-dependent etching behavior. The optical properties of the hot NPs were also found to evolve as the NPs etched, particularly during the initial fast mass loss, and correlations between emission intensities and etching kinetics were examined.