Surface Defect States Research Articles

Decisive role of organic fluorophore and surface defect state in the photoluminescence of carbon quantum dots

Carbon quantum dots (CQDs) hold significant promise for applications in biological imaging, sensing, and optoelectronic devices owing to their superior photostability and low toxicity. Nevertheless, the elucidation of their photoluminescence mechanism remains an open question, necessitating further comprehensive investigation. In this Letter, CQDs exhibiting ultraviolet (UV) and white fluorescence were isolated through silica gel column chromatography separation of the crude product obtained from a one-step solvothermal synthesis. CQDs with different luminescent properties exhibit the same crystal structure and similar particle size distributions. Both CQDs exhibit orthorhombic structure where C60/C70 molecules are located at lattice points, having average particle sizes of 2.71 and 2.98 nm, respectively. Consequently, the luminescent properties of the synthesized CQDs are predominantly governed by their surface structure. The results of microstructure characterization and spectroscopic analysis demonstrate that the UV emission originates from the C(=O)OH and C–O–C related luminescent moieties within organic fluorophores, and the blue emission band is attributed to defect states related to surface group C–O–C, while the green/yellow emission arises from C(=O)O related surface defect levels. These observations have gained a profound understanding of the luminescent genesis of CQDs, broadened the luminescence coverage wavelength range of CQDs, and enriched the family of CQDs materials.

Gallium-doped titania nanotubes as advanced photocatalysts and biopesticides: a path to water purification and vector control

AbstractThe release of Rose Bengal (RB) dye poses a significant threat to aquatic ecosystems, necessitating sustainable water treatment solutions. This study introduces a novel photocatalytic approach utilizing titania nanotubes (TNTs) doped with varying contents of gallium oxide (Ga₂O₃, 0–5%) via a hydrothermal method. Characterization techniques, including FTIR, XRD, TEM, SEM, EDX, and XPS, confirmed the formation of nanotubular structures with enhanced surface area and defect states. The total organic carbon (TOC) measurement indicated effective mineralization of RB dye. Among the synthesized photocatalysts, the 1% Gallium-doped titania nanotubes (Ga-doped TNTs) achieved optimal RB degradation, decomposing 97% of the dye within 110 min under UV illumination, owing to improved charge separation and synergistic effects between Ga and TNTs. Furthermore, Ga-doped TNTs demonstrated superior efficacy in mosquito control, with 100% larvicidal mortality observed at 400 °C compared with only 57.2% for TNTs. Similarly, the pupicidal mortality rate at 72 h increased from 26.2% (TNTs) to 60.8% (Ga-doped TNTs-400). The findings emphasize the dual functionality of Ga-doped TNTs as efficient photocatalysts for water purification and eco-friendly biopesticides, presenting a promising strategy for environmental remediation and vector control.

Interfacial Engineering‐Assisted Energy Level Modulation Enhances the Photoelectrochemical Water Oxidation Performance of Bismuth Vanadate Photoanodes

AbstractBiVO4 faces significant challenges for widespread application in photoelectrochemical (PEC) water oxidation due to its poor hole transport ability, high surface defect density, and sluggish water oxidation reaction kinetics. Employing interfacial engineering to assist in energy level modulation is an effective strategy to address these challenges. Herein, a CuCrO2 hole transport layer (HTL) is coupled and further grew NiCo‐MOF in situ to prepare a NiCo‐MOF‐CuCrO2‐BiVO4 composite photoanode. The novel composite photoanode not only achieves a photocurrent density of 5.75 mA cm−2 at 1.23 V versus a reversible hydrogen electrode (vs RHE) but also maintains stable operation for over 24 h. Comprehensive physicochemical characterization and density‐functional theory calculations confirm that the built‐in electric field generated by the p–n heterojunction formed between the CuCrO2 HTL and BiVO4 photoanode enhances the hole transport ability. Moreover, the NiCo‐MOF chelated on the photoanode surface not only passivates the surface defect states but also accelerates the kinetics of the water oxidation reaction. Under the synergistic effect of dual modification, the PEC water oxidation performance of the BiVO4 photoanode is dramatically improved. This pioneering work presents a MOF/HTL/BiVO4 configuration that provides a blueprint for the future development of integrated photoanodes for efficient solar energy conversion.

Surface plasmon-mediated photoluminescence boost in graphene-covered CsPbBr3 quantum dots

The optical properties of graphene (Gr)-covered CsPbBr3 quantum dots (QDs) were investigated using micro-photoluminescence spectroscopy, revealing a remarkable three orders of magnitude enhancement in photoluminescence (PL) intensity compared to bare CsPbBr3 QDs. To elucidate the underlying mechanisms, we combined experimental techniques with density functional theory (DFT) calculations. DFT simulations showed that the graphene layer generates interfacial electrostatic potential barriers when in contact with the CsPbBr3 surface, impeding carrier leakage from perovskite to graphene and enhancing radiative recombination. Additionally, graphene passivates CsPbBr3 surface defect states, suppressing nonradiative recombination of photo-generated carriers. Our study also revealed that graphene becomes n-doped upon contact with CsPbBr3 QDs, activating its plasmon mode. This mode resonantly couples with photo-generated excitons in the perovskite. The momentum mismatch between graphene plasmons and free-space photons is resolved through plasmon scattering at Gr/CsPbBr3 interface corrugations, facilitating the observed super-bright emission. These findings highlight the critical role of graphene as a top contact in dramatically enhancing CsPbBr3 QDs’ PL. Our work advances the understanding of graphene-perovskite interfaces and opens new avenues for designing high-efficiency optoelectronic devices. The multifaceted enhancement mechanisms uncovered provide valuable insights for future research in nanophotonics and materials science, potentially leading to breakthroughs in light-emitting technologies.

Magnetron sputtered nickel oxide with suppressed interfacial defect states for efficient inverted perovskite solar cells

Widely used spin-coated nickle oxide (NiOx) based perovskite solar cells often suffer from severe interfacial reactions between the NiOx and adjacent perovskite layers due to surface defect states, which inherently impair device performance in a long-term view, even with surface molecule passivation. In this study, we developed high-quality magnetron-sputtered NiOx thin films through detailed process optimization, and compared systematically sputtered and spin-coated NiOx thin film surfaces from materials to devices. These sputtered NiOx films exhibit improved crystallinity, smoother surfaces, and significantly reduced Ni3+ or Ni vacancies compared to their spin-coated counterparts. Consequently, the interface between the perovskite and sputtered NiOx film shows a substantially reduced density of defect states. Perovskite solar cells (PSCs) fabricated with our optimally sputtered NiOx films achieved a high power conversion efficiency (PCE) of up to 19.93% and demonstrated enhanced stability, maintaining 86.2% efficiency during 500 h of maximum power point tracking under one standard sun illumination. Moreover, with the surface modification using (4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid (DMAcPA), the device PCE was further promoted to 23.07%, which is the highest value reported for sputtered NiOx based PSCs so far.

Hybrid Overlayer of Defective Ni-MOF and NiO Nanoparticles toward Efficient TiO2/CdS Type-II Heterojunction.

The severe photocorrosion of cadmium sulfide (CdS) restricts its practical application for solar hydrogen production. Although remarkable progress has been achieved with an overlayer strategy for isolating the CdS surface, the lifetime of CdS-based photoanodes is still far from the actual requirements. Herein, a hybrid overlayer of defective Ni-MOF and NiO nanoparticles has been developed through the chemical bath deposition method with postannealing. This hybrid overlayer of Ni-MOF-d is coated on the surface of the TiO2/CdS type-II heterojunction. The composite photoanode exhibits a photocurrent density of 4.41 mA cm-2 at 1.23 VRHE, which is 3.47- and 1.32-fold that of CdS and TiO2/CdS, respectively. The Ni-MOF-d overlayer gives rise to a negative shift of the onset potential by 59.51 mV. After a long-term stability test of 11 h, a photocurrent retention of 70% is observed, which is among the most robust CdS-based photoanodes. The kinetics studies reveal that the performance improvements can be attributed to the multiple functions of the Ni-MOF-d hybrid overlayer, including isolating the CdS surface from the electrolyte, cocatalyzing the electrode oxidation processes, passivating the surface defect states of CdS, and facilitating the charge injection from the photoanode to the electrolyte.

Efficient and stable CsPbBr3/Cs4PbBr6 composite powders passivated and encapsulated with a novel silicon-based ligand

The metal halide perovskite have garnered significant attention for their exceptional photoelectric properties. However, their inherent instability and the sharp decrease of photoluminescence quantum yield (PLQY) in the solid-state significantly limit their practical applications. Appropriate heterojunction structures or matrix encapsulation can efficiently improve the PLQY and stability of the metal halide perovskite. Herein, we report a new silicon-based ligand hydrolysis condensation encapsulation to synthesize CsPbBr3/Cs4PbBr6/BTESPA-x (CPB–Si-x) composite powders with improved luminescence properties and enhanced thermal stability. With the increase of BTESPA (from 0 to 150 μL), the efficient hydrolysis condensation process occurs on the surface of CsPbBr3/Cs4PbBr6. Finally, the abundant amino-silane groups in BTESPA bind to undercoordinated Pb2+, thereby suppressing the surface defect states and enhancing the PLQY from 34.3 % for CsPbBr3/Cs4PbBr6 (CPB) to 82.1 % for CPB-Si-5. Simultaneously, the thermal stability of CPB-Si-5 exhibits a 13 % improvement over that of CPB after undergoing thermal cycling. Furthermore, tricolor white light-emitting-diode (WLEDs) with high color rendering index were fabricated using on-chip blue LED with bright green-emissive CPB-Si-5 composite powder and red-emissive K2SiF6:Mn4+ phosphor, demonstrating the potential applicability of these powders in WLED backlight systems.

Doping Up the Light: A Review of A/B-Site Doping in Metal Halide Perovskite Nanocrystals for Next-Generation LEDs.

All-inorganic metal halide perovskite nanocrystals (PeNCs) show great potential for the next generation of perovskite light-emitting diodes (PeLEDs). However, trap-assisted recombination negatively impacts the optoelectronic properties of PeNCs and prevents their widespread adoption for commercial exploitation. To mitigate trap-assisted recombination and further enhance the external quantum efficiency of PeLEDs, A/B-site doping has been widely investigated to tune the bandgap of PeNCs. The bandgap of PeNCs is adjustable within a small range (no more than 0.1 eV) by A-site cation doping, resulting in changes in the bond length of Pb-X and the angle of [PbX6]4. Nevertheless, B-site doping of PeNCs has a more significant impact on the bandgap level through modification of surface defect states. In this perspective, we delve into the synthesis of PeNCs with A/B-site doping and their impacts on the structural and optoelectronic properties, as well as their impacts on the performance of subsequent PeLEDs. Furthermore, we explore the A-site and B-site doping mechanisms and the impact of device architecture on doped PeNCs to maximize the performance and stability of PeLEDs. This work presents a comprehensive overview of the studies on A-site and B-site doping in PeNCs and approaches to unlock their full potential in the next generation of LEDs.

A hybrid MOFs/Ti-Fe2O3 Z-scheme photoanode with enhanced charge separation and transfer for efficient photoelectrochemical water oxidation

The construction of Z-scheme charge transfer pathways simulating natural photosynthesis is considered a promising method for improving reaction driving forces. Here, we modified the surface of titanium doped Fe2O3 (Ti-Fe2O3) nanorods with NH2-MIL-125(Ti) (Ti-MOFs) and a promising organic-inorganic hybrid Z-scheme NH2-MIL-125(Ti)/Ti-Fe2O3 was successfully prepared. At 1.23 V vs. RHE, the photocurrent density of the composite photoanode reaches 2.67 mA/cm2, which is 5 times higher than that of Ti-Fe2O3. The results of surface photovoltage, ESR and fs-TAS indicate that this improvement is mainly due to the effective Z-scheme charge transfer mechanism providing a strong driving force for charge separation and transport, greatly suppressing carrier recombination and allowing carriers with strong oxidation ability to participate in water oxidation. Meanwhile, NH2-MIL-125(Ti) can enhance light absorption and reduce the surface defect state of Ti-Fe2O3. This study not only provides a feasible approach for the photoanode water splitting of traditional inorganic semiconductor/MOF based heterostructures, but also provides rich and effective means for revealing Z-scheme charge transfer mechanism in depth.

Facile Fabrication of SrTiO3/In2O3 on Carbon Fibers via a Self-Assembly Strategy for Enhanced Photocatalytic Hydrogen Production

Photocatalytic water splitting by semiconductors is considered a promising and cost-effective method for achieving sustainable hydrogen production. In this study, a CF/SrTiO3/In2O3 photocatalytic material with a double-layer core–shell structure was developed. The experimental results indicated that the produced CF/SrTiO3/In2O3 composite fiber displayed superior photocatalytic hydrogen production performance, achieving a hydrogen evolution rate of approximately 320.71 μmol/g·h, which is roughly seven times higher than that of the CF/SrTiO3 fiber alone. The enhanced photocatalytic activity of the CF/SrTiO3/In2O3 fiber can be attributed to the heterojunction structure enriched with oxygen vacancies. It was found that these oxygen vacancies created defective states that served as traps for photogenerated electrons, facilitating their migration to the surface defect states and enabling the reduction of H+ in water to produce hydrogen. Furthermore, the synergy between the heterojunction structure and the conductivity of the carbon fiber promoted the generation and migration of photogenerated electrons, reduced the recombination of photogenerated electron–hole pairs, and ultimately improved photocatalytic hydrogen production. This study presents a new approach for designing efficient photocatalysts with surface oxygen vacancies on carbon fibers, providing new insights into the sustainable application of photocatalysts.

Multifunctional buried interface modification of SnO2-based planar perovskite solar cells via phosphorus hetero-phenanthrene flame retardants

Tin dioxide (SnO2) is widely utilized for the cost-effective electron transport layer (ETL) in perovskite solar cells (PSCs) owing to its excellent optoelectronic properties. However, the surface defect states present in SnO2 ETL prepared by conventional solution methods seriously hinder the further improvement of device photovoltaic performance. It is urgently essential to develop a facile strategy to effectively minimize the adverse effects of SnO2 ETL on PSCs. Herein, a phosphorus hetero-phenanthrene flame retardant, DOPO, is introduced as a multifunctional surface modifier to improve the interfacial properties between SnO2 ETL and perovskite. Through systematic characterization analysis, the PO group in DOPO not only passivates the defective states on the surface of SnO2 ETL, but also provides chemical chelation sites for the uncoordinated Pb2+ ions in the upper perovskite structure to improve the film crystalline quality. Eventually, the photoelectric conversion efficiency (PCE) of the optimized device is improved from an initial 19.74 %–22.57 %, along with significantly improved device stability. This work provides an important reference for the development of new multifunctional interface modification materials required for SnO2-based planar PSCs with excellent properties.

Multi‐Wavelength Optoelectronic Synaptic Transistors Based on Transition Metal Telluride‐Sulfide Heterostructures

AbstractNeuromorphic visual systems based on optogenetic techniques have colossal potential for in‐memory computing with prospects of developing artificial intelligence vision systems. However, conventional transistor architectures face formidable challenges in efficient signal processing owing to limitations in the intrinsic properties of active channel materials. In this work, a novel transition metal telluride‐sulfide hybrid heterojunction‐based optoelectronic synaptic phototransistor is proposed, in which UV–vis responsive zinc oxide encapsulated few‐layer tungsten disulfide channel is decorated with near‐infrared sensitive 0D cobalt ditelluride (CoTe2) nanocrystals (NCs), eliciting the ability to sense, store, and process optical signals across a broad range of the electromagnetic spectrum. This meticulously designed three‐layered heterostructure, based on their interfacial band alignments, enables high photoresponsivity up to ≈2.6 × 103 A W−1 at a back‐gate bias of 20 V, leading to the brain‐inspired synaptic applications with an average power consumption as low as 75 pJ for each training process. The device exhibits excitatory postsynaptic current, paired‐pulse facilitation with an index above 150%, as well as light‐modulated synaptic plasticity by mimicking biological synapses, which mainly originate from trapped holes in Co‐vacancy mediated surface defect states of CoTe2 NCs. Hence, this 2D material‐based hybrid phototransistor appears to be a promising candidate for energy‐efficient next‐generation brain‐inspired neuromorphic vision systems.

Magnesium ions enhanced core-shell lattice matching for Narrow-Band green emission indium phosphide QDs

Indium phosphide QDs have emerged as a promising candidate for the next generation optoelectronic applications. However, the optical performance of InP QDs still lags behind that of CdSe-based QDs, partly due to surface traps induced by the lattice mismatch between InP and ZnSe. Herein, based on (DMA)3P, we designed an alloyed inner-shell structure of InP/Zn(Mg)Se/ZnS QDs. The dual-function mechanism of the Zn(Mg)Se was revealed, which effectively mitigates the lattice mismatch between the core and shell toreduce the emission of surface defect states, resulting in narrowed emission peaks (FWHM ∼ 36 nm). While the increased band gap of Zn(Mg)Se confines the exciton delocalization from core to shell, thereby reducing the non-radiative relaxation of carriers at the defect states in the shell. This discovery provides a strategy to improve the color purity and luminescence efficiency of InP QDs. By combining blue LED chips with InP/Zn(Mg)Se/ZnS, a white light-emitting diode (QLED) with a high luminous efficiency of 63 lm/W was obtained. Furthermore, the realization of QDs arrays with 10 μm pixel dots by inkjet printing technology and the fabrication of white-light emitting Micro-LEDs by combining QDs films with Micro-LED chip arrays demonstrate the potential application of InP QDs in high-efficiency optoelectronic devices (LEDs/micro-LEDs).

Crystallization modulation and defect passivation in carbon-based perovskite solar cells using multifunctional group additive

Recently, carbon-based perovskite solar cells have attracted wide attention in academia and industry because of their simple preparation process, low cost, and adaptability to roll-to-roll industrial production. The combination of ternary perovskite composition and carbon electrode configuration is expected to meet the requirements of device performance and stability. However, low grain size, and high density of grain boundary and surface defect states result in serious non-radiative recombination, which is one of the main gaps between the carbon-based perovskite solar cells and metal-electrode-based devices. Based on the consideration of crystal tuning and defect passivation of ternary CsFAMA thin films, the additive molecule 5-(Difluoromethoxy)-2-mercapto-1H-benzimidazole (DMB) with multifunctional groups were introduced into the film. XRD show that the (100) and (200) crystal plane orientation growth directed by the DMB additive lead to the formation of the micro-sized perovskite. XPS suggests that DMB not only modulates the crystallization of the films but also exists at the grain boundaries, and realizes the passivation of undercoordinated Pb2+ defects and inhibits the generation of Pb0. The defect state density is significantly reduced, and the carrier lifetime is greatly improved. The possible mechanism for perovskite crystal growth as well as defect passivation based on Lewis acid-base coordination and hydrogen bond was also proposed. After the introduction of DMB, a power conversion efficiency of 14.40% was achieved, which was 13.4% higher than that of the control device. After nearly 1200 h of environmental stability test, the DMB modified device still retained 95% of the original efficiency. This work emphasizes the feasibility of simultaneously realizing the crystallization modulation and defect passivation of carbon-based perovskite solar cells using the additive with multifunctional groups, and provides a reference for the commercialization of carbon-based perovskite solar cells.

Tuning Surface Defect States in Sputtered Titanium Oxide Electron Transport Layers for Enhanced Stability of Organic Photovoltaics.

Nonfullerene acceptors (NFAs) have dramatically improved the power conversion efficiency (PCE) of organic photovoltaics (OPV) in recent years; however, their device stability currently remains a bottleneck for further technological progress. Photocatalytic decomposition of nonfullerene acceptor molecules at metal oxide electron transport layer (ETL) interfaces has in several recent reports been demonstrated as one of the main degradation mechanisms for these high-performing OPV devices. While some routes for mitigating such degradation effects have been proposed, e.g., through a second layer integrated on the ETL surface, no clear strategy that complies with device scale-up and application requirements has been presented to date. In this work, it is demonstrated that the development of sputtered titanium oxide layers as ETLs in nonfullerene acceptor based OPV can lead to significantly enhanced device lifetimes. This is achieved by tuning the concentration of defect states at the oxide surface, via the reactive sputtering process, to mitigate the photocatalytic decomposition of NFA molecules at the metal oxide interlayers. Reduced defect state formation at the oxide surface is confirmed through X-ray photoelectron spectroscopy (XPS) studies, while the reduced photocatalytic decomposition of nonfullerene acceptor molecules is confirmed via optical spectroscopy investigations. The PBDB-T:ITIC organic solar cells show power conversion efficiencies of around 10% and significantly enhanced photostability. This is achieved through a reactive sputtering process that is fully scalable and industry compatible.

Unraveling Electron Dynamics in p-type Indium Phosphide (100): A Time-Resolved Two-Photon Photoemission Study.

Renewable ("green") hydrogen production through direct photoelectrochemical (PEC) water splitting is a potential key contributor to the sustainable energy mix of the future. We investigate the potential of indium phosphide (InP) as a reference material among III-V semiconductors for PEC and photovoltaic (PV) applications. The p(2 × 2)/c(4 × 2)-reconstructed phosphorus-terminated p-doped InP(100) (P-rich p-InP) surface is the focus of our investigation. We employ time-resolved two-photon photoemission (tr-2PPE) spectroscopy to study electronic states near the band gap with an emphasis on normally unoccupied conduction band states that are inaccessible through conventional single-photon emission methods. The study shows the complexity of the p-InP electronic band structure and reveals the presence of at least nine distinct states between the valence band edge and vacuum energy, including a valence band state, a surface defect state pinning the Fermi level, six unoccupied surface resonances within the conduction band, as well as a cluster of states about 1.6 eV above the CBM, identified as a bulk-to-surface transition. Furthermore, we determined the decay constants of five of the conduction band states, enabling us to track electron relaxation through the bulk and surface conduction bands. This comprehensive understanding of the electron dynamics in p-InP(100) lays the foundation for further exploration and surface engineering to enhance the properties and applications of p-InP-based III-V-compounds for, e.g., efficient and cost-effective PEC hydrogen production and highly efficient PV cells.

Self‐Assembly PbS Quantum Dot‐Conjugated Polymer Hybrid‐Layered Phototransistor Enables SWIR Photodetection with High Detectivity

AbstractLead sulfide colloid quantum dots (PbS QDs) offer great opportunities to revolutionize large‐area short‐wave infrared (SWIR) detection technologies due to high absorption coefficients and spectral selectivity. However, a critical issue for QDs‐based SWIR detectors is high dark current noise due to thermal carriers and the large amounts of surface defect states induced by the ligand exchange process, which hinders the improvement of the room temperature detectivity and linear dynamic range. Herein, it is demonstrated that these dilemmas can be overcome by adopting a novel hybrid‐layered phototransistor device architecture composed of a self‐assembly high‐mobility organic conduction channel and a bulk heterojunction infrared absorber containing PbS QDs as sensitizers. Strong photo absorption in the photoactive layer creates photogenerated charges that are transferred to the conduction channel, where they recirculate many times due to the long trapped‐electron lifetime in the photoactive layer and the high carrier mobility of the channel. Therefore, low dark current noise and high photoconductive gain are achieved by both electrical gating and photodoping for carrier‐density modulation of phototransistors. Finally, an optimized SWIR phototransistor device with a low room‐temperature dark current of 7 pA and a high detectivity of 8 × 1012 Jones under 1650 nm light illumination is demonstrated.

Stimuli-Responsive CeO2 Removal Via Surface Redox Modulation during Shallow Trench Isolation (STI) Post-Chemical Mechanical Planarization (p-CMP)

As transistor miniaturization continues to extend Moore’s Law into the future of technology, the demand for high-efficiency device manufacturing processes has increased drastically in recent years. More specifically, a critical step in preparing integrated circuits (ICs) and logic devices is Chemical Mechanical Planarization (CMP), which relies on a delicate balance of chemical and mechanical parameters to achieve angstrom-level surface uniformity and ultimately allows for increased transistor packing density. A sub-area of CMP that has gained significant attention is Shallow Trench Isolation (STI), which involves the isolation of electrically active components by removing the bulk oxide (i.e., tetraethyl orthosilicate (TEOS)) overburden from the deposition process. During polishing, chemical slurries comprised of CeO2 nanoparticles, rate enhancers, selectivity and rheology modifiers, and pH adjusters are utilized to activate the oxide layer and consequently remove material. The STI removal mechanism, known as the chemical tooth model, involves the nucleophilic attack of CeO2 nanoparticles at surface defect states (i.e., oxygen vacancies (Ovacs)) and resultant dative Ce-O-Si bond formation, which makes the surface redox state of CeO2 (i.e., Ce3+/Ce4+) a key driver for oxide-nanoparticle interactions. It is well known that Ce3+ nanoparticles contain a higher concentration of Ovacs, which enhances the material removal rate (MRR). However, the hard adsorption properties of CeO2 have resulted in the demand for a more efficient post-CMP (p-CMP) cleaning process for TEOS that promotes increased CeO2 removal without inducing secondary defects (i.e., scratching, dishing, corrosion, etc.). Current industry-standard methods involve using a polyvinyl alcohol (PVA) brush to transport harsh chemistries to contaminated surfaces under high shear force (SF). Additionally, the use of megasonic energy is an emerging non-contact cleaning mode that relies on generating reactive oxygen species (ROS) (i.e., cavitations) to induce particle removal. Previous work has shown that supramolecular additives improve overall particle removal efficiency (PRE) when implemented in traditional PVA brush cleaning due to their ability to encapsulate and charge-flip CeO2 nanoparticles while reducing SF. As a result, this research investigates a combinatorial approach to PVA brush cleaning utilizing megasonic energy to release Fenton catalysts from polymer capsules, which aid in the production of ROS through H2O2 decomposition. Initial results have shown that, by increasing the concentration of ROS during cleaning, a Ce3+ à Ce4+ transition occurs on the surface of adsorbed CeO2, enhancing overall PRE.

Near-Infrared Emission of Ag+ Doped CuInSe2 Quantum Dots

Copper-indium-selenide (CISe) quantum dots (QDs) are a class of appealing materials due to their near-infrared (NIR) photoluminescence (PL) and as a non-toxic alternative to lead and cadmium-based QDs. To improve the low photoluminescence quantum yield (PLQY) of CISe core QDs, the zinc sulfide (ZnS) shell was grown to passivate surface defect states on the CISe core. CISe/ZnS core-shell QDs were synthesized with tetrahedral structure and chalcopyrite phase, resulting in an emission wavelength of 992 nm and a PLQY of 90%. Additionally, Ag2+ was doped into the CISe core to redshift the emission wavelength. The combination of electrons in the conduction band and holes in the trap state formed by Ag2+ led to light emission and a red-shifted emission wavelength. By tuning the stoichiometry and shelling time, Ag-doped CISe/ZnS core-shell QDs were successfully synthesized with a PLQY of 18% at an emission wavelength of 1200 nm. This wavelength falls in the NIR-II range, characterized by minimum absorption, biological autofluorescence, reduced scattering, and deep tissue penetration. The tunable emission and high luminescent CISe QDs have great potential in biological labeling, sensing and optoelectronics applications. Figure 1

Synthesis and Characterization of High‐Quality Ta2O5 Nanoparticles for Highly Selective SAW‐Based DUV Sensor and Corona Detection Application

AbstractIn recent times, significant progress is made in the development of solar‐blind deep‐ultraviolet (DUV) photodetectors (200–280 nm) due to their potential applications for military and civil purposes. In this study, the development of a novel solar‐blind DUV photodetector based on tantalum pentoxide (Ta2O5) nanoparticles (NPs) utilizing Surface Acoustic Wave (SAW) sensor integrated with Interface electronics is reported for the first time. The 3‐D Ta2O5 NPs surface morphology, crystallinity, and defect state level is discussed using various analytical techniques, including scanning electron microscope (SEM), X‐ray diffraction (XRD), and spectrophotometer. The developed 3‐D Ta2O5 NPs based photodetector exhibits high sensitivity to 254 nm DUV irradiation (5 µW cm−2), demonstrating excellent photoresponse characteristics. The performance parameters including highest sensitivity, fast response/recovery time are measured as 1621.1 ppm (mW cm−2)−1, 3.7s/19.8s, respectively. Subsequent analysis demonstrates the stability and repeatability of the photodetector, enabling its potential to real time corona discharge detection. With its inherent advantages, the current DUV photodetector utilizing Ta2O5 NPs exhibits great potential for future applications in DUV optoelectronics.