Reduced Surface Defects Research Articles

Improvement of X-ray response of CZT films by post-annealing

CdZnTe (CZT) epitaxial films are promising for X-ray flat panel detectors due to their ability for large area fabrication, high absorption efficiency, and excellent detective quantum efficiency (DQE). However, challenges like image lag, ghosting, and reduced DQE due to long response times and high dark currents persist. This study introduces a novel post-in-situ annealing technique to enhance CZT film sensitivity and transient response. Results show that a brief 20 s annealing treatment increased surface Zn content, raising detector resistivity from 3.5 × 109 Ω·cm to 3.3 × 1010 Ω·cm while reducing leakage current at high voltages. This treatment also significantly reduced surface defects, improving CZT film detectors’ X-ray response time. Moreover, the electrons mobility-lifetime product (μτ)e improved from 2.30 × 10−5 cm2/V to 2.17 × 10−4 cm2/V, indicating enhanced charge carrier dynamics crucial for high-speed X-ray detection. Notably, the X-ray response sensitivity achieved a commendable 126 μC G−1· cm−2 a bias of 30 V. In conclusion, in-situ annealing represents a remarkable step forward in the development of CZT technology for X-ray flat panel imaging, addressing critical issues and potentially broadening its applications in medical and industrial imaging systems.

Microcrystalline Engineering of Anthracite-Based Carbon Via Salt-Assisted Ball Milling for Enhanced Sodium Storage Performance.

Coal-based carbon material, characterized by abundant resources and low cost, has gained considerable interests as a promising anode candidate for sodium-ion batteries (SIBs). However, the coal-based carbon generally shows inferior Na-storage performance due to its highly-ordered microstructure with narrow interlayer spacing. Herein, a salt-assisted mechanical ball-milling strategy is proposed to disrupt the polycyclic aromatic hydrocarbon structure in anthracite molecules, thereby reducing the microcrystalline regularity of the derived carbon during following pyrolysis process. In addition, the induced C─O─C bonds during ball-milling process can alter the pyrolysis behavior of anthracite and restrain the formation of surface defects. Consequently, in contrast to pristine anthracite-based pyrolytic carbon, which exhibits a Na-storage capacity of 198.4 mAh g-1 with a low initial Coulombic efficiency (ICE) of 65.1%, the ball-milling modified carbon assisted by NaCl salt (NAC), with enhanced structural disordering and reduced surface defects, demonstrate significantly improved Na-storage capacity of 332.1 mAh g-1 and ICE value of 82.0%. The NAC electrode also realizes excellent cycle and rate performance, retaining a capacity of 196.0 mAh g-1 at 1 C after 1000 cycles. Furthermore, when coupled with NaNi1/3Fe1/3Mn1/3O2 cathode, the assembled Na-ion full cell deliveres an exceptional electrochemical performance, highlighting its promising prospect as high-performance anode for SIBs.

Co-molding High Temperature Erosion Coatings for Thermoset Polyimide Composites

High temperature (200-260°C) military composite engine components made of carbon fiber thermoset materials are susceptible to erosion damage. Evidenced by wear seen during operation, erosion protection remains a challenge for composites in the engine air flow path. In this paper, we investigate polyetheretherketone (PEEK), thermoplastic polyimide (TPI), and ceramic fabric (Nextel™) as potential high temperature erosion coatings for thermoset polyimide composite engine components. We evaluate the erosion protection materials for two qualities: (1) co-moldability with thermoset polyimide composite panels, and (2) erosion resistance to a sandblasting test. Autoclave and compression molding were used to test co-moldability with different manufacturing methods. The compression molding process was optimized to reduce surface defects using a pre-imidization step before the erosion protection layer was applied and final cure was completed. Co-molded test panels were cut into small coupons for sandblasting. After 60 s of alumina sandblasting PEEK had negligible mass loss, whereas the TPI and ceramic fabric had roughly the same erosion rate as the uncoated polyimide laminate.

The effect of amino acid addition in CeO2-based slurry on SiO2/Si3N4 CMP: Removal rate selectivity, morphology, and mechanism research

The continuous reduction in feature size of integrated circuits has raised stricter material removal selectivity and surface quality requirements for the chemical mechanical polishing (CMP) process of shallow trench isolation (STI). To reduce surface defects, small-sized CeO2 abrasives are introduced into the CMP of STI. We investigated the impacts of three amino acids and their composites added to a 50 nm-sized CeO2 dispersion (pH maintained at 5) on the polishing of silicon dioxide and silicon nitride. The promoting or inhibitory effects of amino acids first increased and then decreased with increasing concentration. When 0.02 M lysine and 0.02 M glutamic acid were added to 0.5 wt% CeO2 dispersion, the best effect was achieved. At this time, the material removal rate (MRR) of SiO2 and Si3N4 were 2993.4 Å/min and 137.2 Å/min, respectively, with surface roughness of 0.108 nm and 0.142 nm in the 5 μm × 5 μm region. This study shows that amino acids promote the MRR of SiO2 primarily by enhancing the reactivity of Ce4+ by complexing with carboxyl groups. In contrast, amino acids inhibit the MRR of Si3N4 primarily by forming strong hydrogen bonds between the amino group and its surface, resulting in surface adsorption and suppressing the hydrolysis reaction. The CMP mechanisms of the three amino acids are similar, and the differences in their effects are mainly due to the varying numbers of amino and carboxyl groups they carry. The adsorption of three amino acids on SiO2 and Si3N4 surfaces was simulated by Materials Studio software, and the results were consistent with the experimental results. Finally, this paper explained the mechanism of action of amino acids at the microscopic level and provided some guidance on improving the performance of CeO2 slurry.

Removal mechanism and hole quality of SiCp/Al composites by ultrasonic elliptical vibration-assisted helical milling

SiCp/Al composites are widely used in the aerospace field due to their excellent properties. However, the huge difference in the properties of silicon carbide and aluminum matrix materials can easily lead to machining defects. Ultrasonic vibration-assisted machining is an effective method to deal with difficult-to-machine materials. In this study, ultrasonic elliptical vibration is applied to the helical milling of SiCp/Al composites. Firstly, the ultrasonic elliptical vibration-assisted helical milling (UEVHM) cutting-edge trajectory is modeled, and the equation of the UEVHM tool-chip separation condition is established, which lays a foundation for the analysis of the cutting mechanism. Then, the influence of ultrasonic elliptical vibration on the removal mechanism of SiCp/Al composites was investigated by finite element simulation. It was found that UEVHM can reduce the tearing of aluminum matrix and reduce the hole damage by changing the direction of the cutting velocity and the relative position of the cutting edge and particles. Finally, the single-factor experiment was carried out, and the surface morphology and roughness of HM and UEVHM were compared. The influence of process parameters on the surface roughness of UEVHM was analyzed. The experimental results show that compared with HM, UEVHM can reduce surface defects and exit damage, to obtain better surface roughness and exit edge quality. The increase in cutting speed can reduce the roughness, and the increase in pitch and revolution speed will increase the surface roughness.

Positive Effects of Guanidinium Salt Post-Treatment on Multi-Cation Mixed Halide Perovskite Solar Cells.

As one of the most promising photovoltaic technologies, perovskite solar cells (PSCs) exhibit high absorption coefficients, tunable bandgaps, large carrier mobilities, and versatile fabrication techniques. Nevertheless, the commercialization of the technology is hindered by poor material stability, short device lifetimes and the scalability of fabrication techniques. To address these technological drawbacks, various strategies have been explored, with one particularly promising approach involving the formation of a low-dimensional layer on the surface of the three-dimensional perovskite film. In this work, we demonstrate the use of guanidinium tetrafluoroborate, CH6BF4N3, (GATFB) as a post-treatment step to enhance the performance of PSCs. Compared with the control sample, the application of GATFB improves the film surface topology, reduces surface defects, suppresses non-radiative recombination, and optimizes band alignment within the device. These positive effects reduce recombination losses and enhance charge transport in the device, resulting in PSCs with an open-circuit voltage (VOC) of 1.18 V and a power conversion efficiency (PCE) of 19.7%. The results obtained in this work exhibit the potential of integrating low-dimensional structures in PSCs as an effective approach to enhance the overall device performance, providing useful information for further advancement in this rapidly evolving field of photovoltaic technology.

Chemical polishing strategies to improve flexible perovskite solar cells based on dopant-free hole transport layers

For n-i-p typed flexible perovskite solar cells (fPSCs), the doped hole transport layer significantly impacts the devices' long-term stability. Using dopant-free organic hole transport materials (d-HTMs) is promising for stable fPSCs. However, the low conductivity of d-HTMs limited their thickness, making them sensitive to the surface morphology of the perovskite film's upper surface. Here, we report a chemical polishing strategy using 1-hexyl-3-methylimidazolium acetate (HMIM∙Ac) as the polishing reagent to enhance the upper surface of the perovskite film, which could form a smooth and flat surface. Meanwhile, the treatment can reduce surface defects and smaller grains on top of the surface. Then, we deposite an ultra-thin dopant-free PM6 layer, a typical hole transport layer, on top of the polished perovskite film. The PM6 layer shows an improved face-on orientation and then carrier mobility. Moreover, suppressed non-radiative recombination at the perovskite/PM6 interface is also observed, translating into a higher open-circuit voltage and fill factor of the fPSCs. As a result, a champion power conversion efficiency (PCE) of 17.76 ​%, with an open-circuit voltage of 1.025 ​V and fill factor of 78.2 ​%, is obtained, which is one of the highest PCEs among the reported fPSCs based on d-HTMs. Our strategy demonstrates a facile but effective way of developing high-efficiency and stable fPSCs for future applications.

One-Step Hydrothermal Synthesis of Sn-Doped Sb2Se3 for Solar Hydrogen Production.

Antimony selenide (Sb2Se3) has recently been intensively investigated and has achieved significant advancement in photoelectrochemical (PEC) water splitting. In this work, a facile one-step hydrothermal method for the preparation of Sn-doped Sb2Se3 photocathodes with improved PEC performance was investigated. We present an in-depth study of the performance enhancement in Sn-doped Sb2Se3 photocathodes using capacitance-voltage (CV), drive-level capacitance profiling (DLCP), and electrochemical impedance spectroscopy (EIS) techniques. The incorporation of Sn2+ into the Sb2Se3 results in increased carrier density, reduced surface defects, and improved charge separation, thereby leading to improved PEC performance. With a thin Sb2Se3 absorber layer (270 nm thickness), the Sn-doped Sb2Se3 photocathode exhibits an improved photocurrent density of 17.1 mA cm-2 at 0 V versus RHE (V RHE) compared to that of the undoped Sb2Se3 photocathode (14.4 mA cm-2). This work not only highlights the positive influence of Sn doping on Sb2Se3 photocathodes but also showcases a one-step method to synthesize doped Sb2Se3 with improved optoelectronic properties.

Improving perovskite solar cell efficiency and prolonging durability via interface modification with guanidinium iodide by post treatment method

The performance of perovskite solar cells (PSCs) can be significantly compromised by the presence of halide vacancies on the perovskite surface, leading to defects and a decline in stability and efficiency. Effectively addressing this challenge, the application of Guanidinium iodide (GAI) as a post dopant treatment (POST) has demonstrated success. GAI (POST) not only reduces surface defects but also minimizes halide deficiencies and mitigates losses due to interfacial charge recombination. When incorporating a GAI additive at a solution concentration of 1.5 mg/ml in the modification layer with the perovskite composition Cs0.1FA0.8MA0.1PbI3, the PSC showed a notable power conversion efficiency (PCE) of 20.7%, surpassing the 16.3% efficiency of the control device. Moreover, the adapted device demonstrated an impressive fill factor (FF) of 80.1%. Notably, the enhanced film of the modified device maintained over 80% of its initial efficiency for more than 312 h, highlighting the prospect of creating affordable, effective, and durable PSCs.

A study on the effect of the geometric properties and surface defects on silicon chip flexibility for wearable electronics

A study on the effect of the geometric properties and surface defects on silicon chip flexibility for wearable electronics

Ultrathin-Shelled Zn-AgIn5S8/ZnS Quantum Dots with Partially Passivated Trap States for Efficient Hydrogen Production

The manipulation of trap states plays a crucial role in the development of efficient photocatalysts. An ultrathin-shelled Zn-AgIn5S8/ZnS quantum dots (QDs) photocatalyst was synthesized via in situ growth using a low-temperature hydrothermal method. The optical properties of the samples coated with ZnS shell were studied vis UV-vis absorption and fluorescence spectra. The ultrathin ZnS shell plays an important role in the Zn-AgIn5S8/ZnS core–shell heterostructure photocatalytic water splitting system, which could reduce surface defects, prolong the carrier lifetime and improve the photo-generated electron–hole pair separation effectively, resulting in the improved photocatalytic efficiency and enhanced stability of the catalyst. The results provide an effective guideline for shell thickness design in future constructions of the core–shell heterostructure photocatalyst.

Optimizating TiO2 electron transport layer for MAPbBr3 perovskite solar cells by way of Ga doping

The exceptional electron transport performance and high stability of titanium dioxide (TiO2) make it widely used in the electron transport layer (ETL). However, the presence of numerous surface defects in TiO2 layer can lead to unnecessary non-radiative recombination, which reduces carrier mobility and affects the photoelectric conversion efficiency (PCE) of perovskite solar cells (PSCs). Therefore, tremendous researches have been focused on reducing surface defects and improving carrier mobility in TiO2 layer. In this study, we adopted metal gallium (Ga) with high conductivity at room temperature as an optimization strategy to enhance the performance of TiO2 layer. By incorporating metal Ga into the TiO2 precursor solution, we successfully fabricated a TiO2-Ga layer that exhibits reduced surface defects and optimized energy level structure. This provides an efficient pathway for electron transport in perovskite layer. Experimental results demonstrate that (methyl ammonium lead tribromide) MAPbBr3 perovskite solar cell devices based on TiO2-Ga layer achieve nearly 24% higher PCE compared to those based on pure TiO2 layer. This successful optimization strategy utilizing metal Ga offers novel insights and approaches for enhancing the performance of PSCs.

Ultrahigh-performance indoor perovskite quantum dot photovoltaics via ligand-passivation engineering

The advancement of perovskite photovoltaic (PePV) systems for harnessing indoor light energy has been accelerated by the advent of the Internet of Things (IoT). However, the commercialization of these systems is impeded by moisture instability and restricted carrier lifetimes. Perovskite quantum dots (PQDs) offer viable solutions for increasing stability despite the potential effects of their organic ligands on efficiency. In this study, a ligand passivation strategy was employed in PQD photovoltaics (PQDPVs) to enhance the carrier lifetime. The inclusion of 2-phenyl-4-(1,2,2-triphenylvinyl) quinazoline (2PACz) in the PQD film effectively reduced surface defects and suppressed trap-assisted charge recombination, resulting in a prolonged carrier lifetime. The charge carrier lifetimes in passivated PQDPVs increased by 35 %. Additionally, the matching of the energy level of the PQD changed after 2PACz passivation engineering with that of the 2PACz showed an advantage for hole transport. PQDPVs fabricated using 2PACz-passivated PQDs showed an impressive output power density (Pout) of 123.3 µW/cm2 (power conversion efficiency of 41.1 %) under a fluorescent lamp (0.30 mW/cm2; 1000 lx) owing to improved open-circuit voltage and fill factor. Moreover, the device maintained more than 80 % of its initial efficiency for 500 h in an ambient atmosphere. These findings highlight the potential of PQDPVs to compete with conventional PePVs for application in self-powered optoelectronic devices under dim illumination.

Reducing Surface Defects of Continuously Cast 13Cr Steel Billets Caused By “Longitudinal Scabs”

Reducing Surface Defects of Continuously Cast 13Cr Steel Billets Caused By “Longitudinal Scabs”

Застосування ультразвукових технологій поверхневої обробки в адитивному виробництві металевих сплавів

In a modern world, additive manufacturing of metal products has reached significant volumes and variety of applied alloys. 3D-printing technologies make it possible to obtain parts with reduced mass, increased reliability, single products, experimental parts and elements designs with complex geometry and configuration. Disadvantages of metal parts additive manufacturing include anisotropy of chemical composition and properties, non-equilibrium structural-phase state, structural micro- and macrodefects and some other features, that require post-processing of as-printed products. Most often, heat treatment and its combination with microforging or intensive surface plastic deformation are used for this purpose. The manuscript provides an analytical review of the advantages of using ultrasonic technologies to support 3D-printing and post-processing of additively manufactured products. Special attention is paid to ultrasonic impact treatment (UIT). The equipment for providing UIT is compact, energy-saving and easy to use. It is noted, that this technology makes it possible to effectively reduce surface defects of printed parts, increase its hardness and fatigue strength. At the same time, nanostructuring and changes in the structural and phase state of the modified layers are also occured. It is also noted, that UIT may provide surface strengthening to a depth of ~500 μm, saturating it with alloying elements and compounds, and for conventionally produced parts, like as–cast, deformed and powder sintered – it is significantly more effective than most other similar methods. The prospects of using ultrasonic technologies to improve quality and level of operational and mechanical characteristics of additively manufactured metal parts, including the needs of aircraft construction, are outlined. Keywords: additive technologies, 3D-printing, ultrasonic impact treatment, UIT, surface strengthening, cavitation, vibration polishing, fatigue strength, Grade5, AlSi10Mg, Inconel-718.

C/C-HfC-SiC composites with simultaneous the resistance to ultra-high temperature airflow erosion and high temperature oxidation

HfC-SiC modified C/C composites containing in situ formed Si-HfC-HfSi2 ablation resistant layer and SiC oxidation resistant layer were successfully prepared by reactive melt infiltration (RMI) combined with gaseous silicon infiltration (GSI). A comparative study was conducted on the anti-oxidation and anti-ablation performance of the C/C-HfC-SiC composites with GSI (noted as RG-CHS) and without GSI (noted as R-CHS). After oxidation at 1,500 °C for 200 min, the oxide film of RG-CHS remained intact. The mass and linear ablation rates decreased from 1.31 mg/s and 7.36 μm/s to 0.12 mg/s and −0.22 μm/s after GSI process, respectively. The introduction of low melting point phases and reducing surface defects can improve the high temperature oxidation resistance and plasma ablation resistance of the composites.

Facile sulfur-assisted synthesis of GaAs nanowires /si heterojunctions for broadband self-powered photodetector

Nanowires (NWs)-based heterojunction photodetectors (PDs) have been widely applied in the fields of remote sensing, night vision, environmental monitoring, and optical communications with high light absorption coefficient and photoelectric conversion efficiency. Here, S-GaAs NWs/Si heterojunction was developed to form a broadband self-powered PDs by growing GaAs NWs on Si substrate through the sulfur-catalyzed assisted chemical vapor deposition (CVD) technology. Compared with the pure GaAs NWs, the sulfur-assisted catalysts could not only inhibit Ostwald ripening of Au seeds to improve the crystalline quality of NWs but also form a thin Ga–S bond passivation layer to reduce surface defects and enhance the optoelectronic performance of the PDs. The fabricated GaAs NWs/Si heterojunction PDs exhibit excellent performances with the large responsivity of 10.3 mA W−1 and high detectivity of 9.59 × 1012 cm Hz1/2 W−1. Additionally, the designed PDs have the broadband wavelength photoresponse from visible to near infrared and fast response speed (rise/fall time of 3.8/21.8 ms). Importantly, the develop strategy of hybrid heterojunction PDs can be extended to other semiconductor materials for facilitating the practical application of high-performance optoelectronic devices.

Optimizing Surface Passivation of n‐Type Quantum Dots for Efficient PbS Quantum Dot Solar Cells

The n‐type quantum dot (QD) active layer is the core component of lead sulfide QD solar cells (PbS QDSCs). In the state‐of‐the‐art PbS QDSCs, the active layer is commonly obtained through liquid‐phase ligand exchange (LPLE). Due to the intricate chemical state of the ligand exchange solution providing halide ligand, therefore, the PbS‐OAQD solutions is used at concentrations of 20, 30, and 40 mg mL−1 for LPLE, aiming to investigate the reasons for different surface states post‐exchange and their impact on device performance. The results indicate that when the concentration of the PbS‐OA QD solution is 30 mg mL−1, the exchanged QDs exhibit complete removal of surface OA, a higher content of short‐chain ligand PbX2 (X = I, Br), Consequently, devices fabricated using PbS‐PbX2 QD obtained through the exchange of 30 mg mL−1 PbS‐OA QD solution achieve a higher power conversion efficiency (PCE) of 12.53%. This study presents a simple and effective strategy to enhance the performance of PbS QDSCs.

Simulation and Experimental Study of Non-Resonant Vibration-Assisted Lapping of SiCp/Al.

SiCp/Al is a difficult-to-machine material that makes it easy to produce surface defects during machining, and researchers focus on reducing the surface defects. Vibration-assisted machining technology is considered an effective method to reduce surface defects by changing the trajectory and contact mode of the abrasive. Aiming at the problem of SiCp/Al processing technology, a vibration-assisted lapping device (VLD) is designed, and elliptical motion is synthesized by a set of parallel symmetrical displacement output mechanisms. The working parameters of the device were tested by simulation and experiment, and the lapping performance was verified. Then, the effects of removal characteristics and process parameters on surface roughness and lapping force were analyzed by simulation and experiment. Simulation and experimental results show that frequency and amplitude that are too low or too high are not conducive to the advantages of NVL. The best surface quality was 54 nm, obtained at A = 8 μm and f = 850 Hz.

Effect of Ge Contents on Oxidation Resistance of Ni‐15Cr‐5Al Alloy at 1000°C

A Ni‐15Cr‐5Al‐6Ge alloy was prepared using powder metallurgy technology. The effect of Ge on the oxidation resistance of Ni‐Cr‐Al alloy at 1000°C was investigated. The results indicate that the addition of Ge reduces the oxidation rate of the alloy interface in the range of 0 to 6 wt.% Ge. When the Ge content reaches 6 wt.%, a continuous and dense oxide film forms on the surface of the matrix, imparting the alloy with the best oxidation resistance. The addition of Ge improves the selective oxidation of Al and inhibits the diffusion rate of Ni and Cr elements to the alloy surface, resulting in the formation of a single, uniform Al2O3 oxide film on the alloy surface with a thickness of approximately 1.45 micrometers. An appropriate amount of Ge (6 wt.%) reduces surface defects, while an excessive amount of Ge (8 wt.%) increases surface defects, thereby adversely affecting the oxidation resistance of the alloy.