Quantum spin nematic phase in a square-lattice iridate.

Spin nematic is a magnetic analogue of classical liquid crystals, a fourth state of matter exhibiting characteristics of both liquid and solid1,2. Particularly intriguing is a valence-bond spin nematic3-5, in which spins are quantum entangled to form a multipolar order without breaking time-reversal symmetry, but its unambiguous experimental realization remains elusive. Here we establish a spin nematic phase in the square-lattice iridate Sr2IrO4, which approximately realizes a pseudospin one-half Heisenberg antiferromagnet in the strong spin-orbit coupling limit6-9. Upon cooling, the transition into the spin nematic phase at TC ≈ 263 K is marked by a divergence in the static spin quadrupole susceptibility extracted from our Raman spectra and concomitant emergence of a collective mode associated with the spontaneous breaking of rotational symmetries. The quadrupolar order persists in the antiferromagnetic phase below TN ≈ 230 K and becomes directly observable through its interference with the antiferromagnetic order in resonant X-ray diffraction, which allows us to uniquely determine its spatial structure. Further, we find using resonant inelastic X-ray scattering a complete breakdown of coherent magnon excitations at short-wavelength scales, suggesting a many-body quantum entanglement in the antiferromagnetic state10,11. Taken together, our results reveal a quantum order underlying the Néel antiferromagnet that is widely believed to be intimately connected to the mechanism of high-temperature superconductivity12,13.

Biosynthesis, biological activities, and structure-activity relationships of decalin-containing tetramic acid derivatives isolated from fungi.

Covering: up to December 2023Decalin-containing tetramic acid derivatives, especially 3-decalinoyltetramic acids (3-DTAs), are commonly found as fungal secondary metabolites. Numerous biological activities of this class of compounds, such as antibiotic, antiviral, antifungal, antiplasmodial, and antiprotozoal properties, have been the subject of ongoing research. For this reason, these molecules have attracted a lot of interest from the scientific community and various efforts including semi-synthesis, co-culturing with bacteria and biosynthetic gene sequencing have been made to obtain more derivatives. In this review, 3-DTAs are classified into four major groups based on the absolute configuration of the bicyclic decalin ring. Their biosynthetic pathways, various biological activities, and structure-activity relationship are then introduced.

Correction: Biosynthesis, biological activities, and structure-activity relationships of decalin-containing tetramic acid derivatives isolated from fungi.

Correction for 'Biosynthesis, biological activities, and structure-activity relationships of decalin-containing tetramic acid derivatives isolated from fungi' by Hyun Woo Kim et al., Nat. Prod. Rep., 2024, https://doi.org/10.1039/d4np00013g.

Exploring the Smoking-Epilepsy Nexus: a systematic review and meta-analysis of observational studies : Smoking and epilepsy.

BACKGROUND: Epilepsy, characterized by recurrent unprovoked seizures, poses significant challenges to affected individuals globally. While several established risk factors for epilepsy exist, the association with cigarette smoking remains debated. This study aims to conduct systematic review and meta-analysis to elucidate the potential association between smoking and the likelihood of epilepsy. METHODS: The search was performed on March 31st, 2023, using the Medline, Embase, Web of Science, Scopus, and ScienceDirect. We included cohort, cross-sectional, and case-control studies in our meta-analysis, conducting subgroup analyses based on smoking history, sex, and epilepsy type to yield specific insights. RESULTS: We identified 2550 studies, of which 17 studies were finally included in this study. The pooled odds ratio of epilepsy was 1.14 (0.96-1.36) in smokers compared to non-smokers. In current smokers compared to non-smokers, the odds ratio was 1.46 (1.13-1.89), while, in former smokers compared to non-smokers, the odds ratio was 1.14 (0.83-1.56). CONCLUSIONS: While the overall association between smoking and epilepsy did not reach statistical significance, a notable association was found among current smokers. The study emphasizes the importance of smoking cessation as a potential preventive measure against epilepsy, especially given the proconvulsive effects of nicotine. Future research should address limitations and explore specific clinical scenarios to enhance our understanding of the complex relationship between cigarette use and epilepsy. SYSTEMATIC REVIEW REGISTRATION: CRD42022342510.

Differences in factors associated with insomnia symptoms between patients with epilepsy with and without depressive symptoms.

OBJECTIVE: To determine if insomnia-related factors differ depending on the presence of depression in patients with epilepsy. METHODS: This cross-sectional multicenter study collected data on depressive symptoms, insomnia symptoms, and excessive daytime sleepiness, which were defined as a Patient Health Questionnaire-9 (PHQ-9) score of ≥ 10, an Insomnia Severity Index (ISI) score of ≥ 15, and an Epworth Sleepiness Scale (ESS) of ≥ 11, respectively. Further, uncontrolled seizures were defined as one or more seizures per month during antiseizure medications treatment. A stepwise logistic regression analysis was conducted, with a logistic regression with interaction terms performed to identify differences in insomnia-related factors depending on depressive symptoms. RESULTS: Of 282 adults with epilepsy (men, 58 %; mean age, 40.4 ± 13.9 years), a PHQ-9 score ≥ 10, an ISI score ≥ 15, an ESS score ≥ 11 were noted in 23.4 % (n = 66), 20.2 % (n = 57), and 12.8 % (n = 36), respectively. More patients with depressive symptoms had an ISI score ≥ 15 (56.1 % vs. 9.3 %; p < 0.001) than those without. In multiple logistic regression, uncontrolled seizures (odds ratio [OR], 4.896; p < 0.01), daytime sleepiness (OR, 5.369; p < 0.05), and a history of psychiatric disorders (OR, 3.971; p < 0.05) were identified as significant factors that were more likely to be associated with an ISI score ≥ 15; however, this was only true in patients without depressive symptoms. In contrast, use of perampanel (OR, 0.282; p < 0.05) was less likely associated, while female sex (OR, 3.178; p < 0.05) was more likely associated with an ISI score ≥ 15 only in patients with depressive symptoms. CONCLUSIONS: Insomnia-related factors in patients with epilepsy may differ between patients with and without depression. Our findings of different insomnia-related factors based on the presence of depression may facilitate the management of patients with epilepsy.

PECAN Predicts Patterns of Cancer Cell Cytostatic Activity of Natural Products Using Deep Learning.

Many machine learning techniques are used as drug discovery tools with the intent to speed characterization by determining relationships between compound structure and biological function. However, particularly in anticancer drug discovery, these models often make only binary decisions about the biological activity for a narrow scope of drug targets. We present a feed-forward neural network, PECAN (Prediction Engine for the Cytostatic Activity of Natural product-like compounds), that simultaneously classifies the potential antiproliferative activity of compounds against 59 cancer cell lines. It predicts the activity to be one of six categories, indicating not only if activity is present but the degree of activity. Using an independent subset of NCI data as a test set, we show that PECAN can reach 60.1% accuracy in a six-way classification and present further evidence that it classifies based on useful structural features of compounds using a "within-one" measure that reaches 93.0% accuracy.

Risk factors for post-polypectomy bleeding in patients with end-stage renal disease undergoing colonoscopic polypectomy.

BACKGROUND AND AIMS: Little is known about the risk factors of bleeding after colonoscopic polypectomy in patients with end-stage renal disease (ESRD). This study investigated the incidence and risk factors of post-polypectomy bleeding (PPB), including immediate and delayed bleeding, in patients with ESRD. METHODS: Ninety-two patients with ESRD who underwent colonoscopic polypectomy between September 2005 and June 2020 at a single tertiary referral center were included. The patients' medical records were retrospectively reviewed. Patient- and polyp-related factors associated with immediate PPB (IPPB) were analyzed using logistic regression analysis. Additionally, the optimal cutoff polyp size related to a significant increase in the risk of IPPB was determined by performing receiver operating characteristic (ROC) analysis and calculating the area under the ROC curve (AUC). RESULTS: In total, 286 polyps were removed. IPPB occurred in 24 (26.1%) patients and 46 (16.1%) polyps and delayed PPB occurred in 2 (2.2%) patients. According to multivariate analysis, the polyp size (> 7 mm), old age (> 70), and endoscopic mucosal resection (EMR) as the polypectomy method (EMR versus non-EMR) were found to be independent risk factors for IPPB. According to the Youden index method, the optimal cutoff polyp size to identify high-risk polyps for IPPB was 7 mm (AUC = 0.755; sensitivity, 76.1%; specificity, 69.6%). CONCLUSIONS: Colonoscopic polypectomy should be performed with caution in patients with ESRD, especially in those with the following risk factors: advanced age (> 70 years), polyp size > 7 mm, and EMR as the polypectomy method.

Effect of Solitary Osteochondroma on Alignment and Length in the Lower Extremities.

BACKGROUND: There is a lack of information about the effects of untreated solitary osteochondroma (SO) on longitudinal growth of the lower extremities in children and adolescents. This study aimed to assess the coronal alignment and length of the lower extremity in patients with SO around the knee and to identify the factors related to the development of deformities. METHODS: We retrospectively reviewed 111 patients diagnosed with SO around the knee. The patients were classified into 2 groups depending on the location of the SO: 51 in the distal femur and 60 in the proximal tibia. Characteristics of the lesions, such as type, location, size, and distance from the joint line, were determined. Radiographic analysis of the lower limbs included mechanical lateral distal femoral angle, mechanical medial proximal tibial angle, whole-leg length, femoral length, and tibial length. RESULTS: The mean age at the time of diagnosis was 12.3±3.4 years. No statistically significant differences were found between the affected and contralateral sides for mechanical lateral distal femoral angle and mechanical medial proximal tibial angle in either the distal femur or the proximal tibia groups. In patients with femoral lesions, the femoral and whole-leg lengths were significantly shorter on the affected side than on the unaffected side ( P <0.001 and 0.002, respectively), and the mean differences were 2.1±3.6 and 2.1±4.4 mm, respectively. Univariate logistic regression analysis did not reveal any factors associated with limb length discrepancy (LLD). In patients with tibial lesions, no statistically significant differences were found in LLD. CONCLUSIONS: SOs around the knee did not cause clinically significant deformity of the lower extremity. However, in contrast to proximal tibia lesions, SO in the distal femur was associated with the shortening of the affected limb. Consideration should be given to the development of LLD in skeletally immature children with SO in the distal femur. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Image Processing Techniques for Improving Quality of 3D Profile in Digital Holographic Microscopy Using Deep Learning Algorithm.

Digital Holographic Microscopy (DHM) is a 3D imaging technology widely applied in biology, microelectronics, and medical research. However, the noise generated during the 3D imaging process can affect the accuracy of medical diagnoses. To solve this problem, we proposed several frequency domain filtering algorithms. However, the filtering algorithms we proposed have a limitation in that they can only be applied when the distance between the direct current (DC) spectrum and sidebands are sufficiently far. To address these limitations, among the proposed filtering algorithms, the HiVA algorithm and deep learning algorithm, which effectively filter by distinguishing between noise and detailed information of the object, are used to enable filtering regardless of the distance between the DC spectrum and sidebands. In this paper, a combination of deep learning technology and traditional image processing methods is proposed, aiming to reduce noise in 3D profile imaging using the Improved Denoising Diffusion Probabilistic Models (IDDPM) algorithm.

Three-Dimensional Image Visualization under Photon-Starved Conditions Using N Observations and Statistical Estimation.

In this paper, we propose a method for the three-dimensional (3D) image visualization of objects under photon-starved conditions using multiple observations and statistical estimation. To visualize 3D objects under these conditions, photon counting integral imaging was used, which can extract photons from 3D objects using the Poisson random process. However, this process may not reconstruct 3D images under severely photon-starved conditions due to a lack of photons. Therefore, to solve this problem, in this paper, we propose N-observation photon-counting integral imaging with statistical estimation. Since photons are extracted randomly using the Poisson distribution, increasing the samples of photons can improve the accuracy of photon extraction. In addition, by using a statistical estimation method, such as maximum likelihood estimation, 3D images can be reconstructed. To prove our proposed method, we implemented the optical experiment and calculated its performance metrics, which included the peak signal-to-noise ratio (PSNR), structural similarity (SSIM), peak-to-correlation energy (PCE), and the peak sidelobe ratio (PSR).

Wafer-Scale Epitaxial Growth of an Atomically Thin Single-Crystal Insulator as a Substrate of Two-Dimensional Material Field-Effect Transistors.

As the electron mobility of two-dimensional (2D) materials is dependent on an insulating substrate, the nonuniform surface charge and morphology of silicon dioxide (SiO2) layers degrade the electron mobility of 2D materials. Here, we demonstrate that an atomically thin single-crystal insulating layer of silicon oxynitride (SiON) can be grown epitaxially on a SiC wafer at a wafer scale and find that the electron mobility of graphene field-effect transistors on the SiON layer is 1.5 times higher than that of graphene field-effect transistors on typical SiO2 films. Microscale and nanoscale void defects caused by heterostructure growth were eliminated for the wafer-scale growth of the single-crystal SiON layer. The single-crystal SiON layer can be grown on a SiC wafer with a single thermal process. This simple fabrication process, compatible with commercial semiconductor fabrication processes, makes the layer an excellent replacement for the SiO2/Si wafer.

8-Prenylgenistein Isoflavone in Cheonggukjang Acts as a Novel AMPK Activator Attenuating Hepatic Steatosis by Enhancing the SIRT1-Mediated Pathway.

8-Prenylgenistein (8PG), a genistein derivative, is present in fermented soybeans (Glycine max), including cheonggukjang (CGJ), and exhibits osteoprotective, osteogenic, and antiadipogenic properties. However, the hepatoprotective effects of 8PG and its underlying molecular mechanisms remain largely unexplored. Here, we identified the high binding affinity of 8PG with AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1), which acts as a potent AMPK activator that counteracts hepatic steatosis. Notably, 8PG exhibited better pharmacokinetics with greater absorption and higher plasma binding than the positive controls for the target proteins. Moreover, 8PG exerted non-carcinogenic activity in rats and significantly increased AMPK phosphorylation. Compound C, an AMPK inhibitor, did not antagonize 8PG-activated AMPK in HepG2 cells. 8PG significantly attenuated palmitate-induced lipid accumulation and enhanced phosphorylated AMPK and its downstream target, acetyl-CoA carboxylase. Further, 8PG activated nuclear SIRT1 at the protein level, which promoted fatty acid oxidation in palmitate-treated HepG2 cells. Overall, 8PG acts as a potent AMPK activator, further attenuating hepatic steatosis via the SIRT1-mediated pathway and providing new avenues for dietary interventions to treat metabolic dysfunction-associated steatotic liver disease (MASLD).

Mitogenomic Architecture of Atlantic Emperor Lethrinus atlanticus (Actinopterygii: Spariformes): Insights into the Lineage Diversification in Atlantic Ocean.

The evolutionary history of emperors, particularly in the Atlantic and Indo-West Pacific Oceans, remains largely unmapped. This study explores the maternal lineage evolution of Lethrinids by examining the complete mitogenome of Lethrinus atlanticus, which is endemic to the Eastern Atlantic Ocean. Utilizing advanced next-generation sequencing, we found that the mitogenome spans 16,789 base pairs and encompasses 37 genes, including 13 protein-coding genes (PCGs), two ribosomal RNAs, 22 transfer RNAs, and an AT-rich control region (CR). Our analysis indicates a preference for AT base pairs in the L. atlanticus mitogenome (53.10%). Most PCGs begin with the ATG codon, except for COI, which starts with GTG. Relative synonymous codon usage reveals high frequencies for alanine, leucine, proline, serine, and threonine. The ratio of nonsynonymous to synonymous substitutions suggests strong negative selection across all PCGs in Lethrinus species. Most transfer RNAs exhibit typical cloverleaf structures, with the exception of tRNA-serine (GCT), which lacks a dihydrouracil stem. Comparative analysis of conserved sequence blocks across the CRs of three Lethrinus species shows notable differences in length and nucleotide composition. Phylogenetic analysis using concatenated PCGs clearly distinguishes all Lethrinus species, including L. atlanticus, and sheds light on the evolutionary relationships among Spariformes species. The estimated divergence time of approximately 20.67 million years between L. atlanticus and its Indo-West Pacific relatives provides insights into their historical separation and colonization during the late Oligocene. The distribution of Lethrinids may be influenced by ocean currents and ecological factors, potentially leading to their speciation across the Eastern Atlantic and Indo-West Pacific. This study enhances our understanding of the genetic diversity and phylogenetic relationships within Lethrinus species. Further exploration of other emperor fish mitogenomes and comprehensive genomic data could provide vital insights into their genetic makeup, evolutionary history, and environmental adaptability in marine ecosystems globally.

The Chronic Toxicity of Endocrine-Disrupting Chemical to Daphnia magna: A Transcriptome and Network Analysis of TNT Exposure.

Endocrine-disrupting chemicals (EDCs) impair growth and development. While EDCs can occur naturally in aquatic ecosystems, they are continuously introduced through anthropogenic activities such as industrial effluents, pharmaceutical production, wastewater, and mining. To elucidate the chronic toxicological effects of endocrine-disrupting chemicals (EDCs) on aquatic organisms, we collected experimental data from a standardized chronic exposure test using Daphnia magna (D. magna), individuals of which were exposed to a potential EDC, trinitrotoluene (TNT). The chronic toxicity effects of this compound were explored through differential gene expression, gene ontology, network construction, and putative adverse outcome pathway (AOP) proposition. Our findings suggest that TNT has detrimental effects on the upstream signaling of Tcf/Lef, potentially adversely impacting oocyte maturation and early development. This study employs diverse bioinformatics approaches to elucidate the gene-level toxicological effects of chronic TNT exposure on aquatic ecosystems. The results provide valuable insights into the molecular mechanisms of the adverse impacts of TNT through network construction and putative AOP proposition.

Mitogenomic Characterization and Phylogenetic Placement of African Hind, Cephalopholis taeniops: Shedding Light on the Evolution of Groupers (Serranidae: Epinephelinae).

The global exploration of evolutionary trends in groupers, based on mitogenomes, is currently underway. This research extensively investigates the structure of and variations in Cephalopholis species mitogenomes, along with their phylogenetic relationships, focusing specifically on Cephalopholis taeniops from the Eastern Atlantic Ocean. The generated mitogenome spans 16,572 base pairs and exhibits a gene order analogous to that of the ancestral teleost's, featuring 13 protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), and an AT-rich control region. The mitogenome of C. taeniops displays an AT bias (54.99%), aligning with related species. The majority of PCGs in the mitogenome initiate with the start codon ATG, with the exceptions being COI (GTG) and atp6 (TTG). The relative synonymous codon usage analysis revealed the maximum abundance of leucine, proline, serine, and threonine. The nonsynonymous/synonymous ratios were <1, which indicates a strong negative selection among all PCGs of the Cephalopholis species. In C. taeniops, the prevalent transfer RNAs display conventional cloverleaf secondary structures, except for tRNA-serine (GCT), which lacks a dihydrouracil (DHU) stem. A comparative examination of conserved domains and sequence blocks across various Cephalopholis species indicates noteworthy variations in length and nucleotide diversity. Maximum likelihood, neighbor-joining, and Bayesian phylogenetic analyses, employing the concatenated PCGs and a combination of PCGs + rRNAs, distinctly separate all Cephalopholis species, including C. taeniops. Overall, these findings deepen our understanding of evolutionary relationships among serranid groupers, emphasizing the significance of structural considerations in mitogenomic analyses.

Blocking screw (pin) technique to achieve an acceptable reduction in intramedullary of subtrochanteric femoral fractures: indications, techniques, and clinical outcomes.

INTRODUCTION: Subtrochanteric femur fractures treated with intramedullary nails present biomechanical benefits, early weight-bearing, and reduced soft tissue damage, promoting bone union. However, improper reduction due to muscular forces and fragmented proximal bone increases nonunion risk. This study evaluates the efficacy of the blocking screw technique in preventing malalignment during intramedullary nailing. MATERIAL AND METHODS: In cases of subtrochanteric femoral fractures where malalignment, such as varus and anterior angulation, was anticipated during intramedullary nailing, proper reduction was ensured using blocking screw technique on the proximal bone fragment from the coronal or sagittal plane. A retrospective analysis was conducted on 25 patients (14 males, 11 females; average age 55.12 years) who were followed up for more than 1 year. The postoperative neck-shaft angle, anterior angulation angle, and limb length discrepancy were compared radiologically with those on the healthy side, and the presence and duration of bone union were measured. The Harris hip score was used for functional evaluation, and complications, including infection, were analyzed. RESULTS: At the final follow-up, primary bone union was achieved in 21/25 patients (84%), with an average bone union time of 21.81 weeks (range, 14-42 weeks). Of the four nonunions, bone union was achieved in three cases through bone grafting and supplemental plating and in the other case through intramedullary exchange, supplemental plating, and bone grafting. The femoral neck-shaft angle and anterior angulation showed no statistically significant differences compared with the healthy side, with averages of - 1.15° and - 1.4°, respectively. The limb length discrepancy was an average of - 2.4 mm. Regarding functional outcomes, the Harris hip score averaged 89.52 points (range 82-94 points). CONCLUSIONS: In subtrochanteric femoral fractures, the blocking screw technique effectively prevents malalignment during intramedullary nailing, ensuring not only appropriate reduction but also high bone union rates.

Elaboration of dimensional quality in 3D-printed food: Key factors in process steps.

Three-dimensional (3D) printing has been applied to produce food products with intricate and fancy shapes. Dimensional quality, such as dimensional stability, surface smoothness, shape fidelity, and resolution, are essential for the attractive appearance of 3D-printed food. Various methods have been extensively studied and proposed to control the dimensional quality of printed foods, but few papers focused on comprehensively and deeply summarizing the key factors of the dimensional quality of printed products at each stage-before, during, and after printing-of the 3D printing process. Therefore, the effects of pretreatment, printing parameters and rheological properties, and cooking and storage on the dimensional quality of the printed foods are summarized, and solutions are also provided for improving the dimensional quality of the printed products at each step. Before printing, incorporating additives or applying physical, chemical, or biological pretreatments can improve the dimensional quality of carbohydrate-based, protein-based, or lipid-based printed food. During printing, controlling the printing parameters and modifying the rheological properties of inks can affect the shape of printed products. Furthermore, post-processing is essential for some printed foods. After printing, changing formulations, incorporating additives, and selecting post-processing methods and conditions may help achieve the desired shape of 3D-printed or 4D-printed products during cooking. Additives help in the storage stability of printed food. Finally, various opportunities have been proposed to regulate the dimensional properties of 3D-printed structures. This review provides detailed guidelines for researchers and users of 3D printers to produce various printed foods with the desired shapes and appearances.

Surgical management of severe planovalgus foot deformity in children with generalised joint hypermobility.

BACKGROUND: This study aimed to evaluate the outcomes of calcaneal lengthening osteotomy (CLO) and double arthrodesis of the talonavicular and calcaneocuboid joints (DA) for correcting planovalgus foot deformity exclusively in patients with generalised joint hypermobility. METHODS: We retrospectively reviewed 29 feet in 17 consecutive patients who underwent either CLO or DA. The mean age at surgery was 11.3 ± 2.3 years, and the mean follow-up duration was 7.7 ± 3.2 years. Preoperative and final follow-up radiographs and dynamic foot-pressure measurements were analysed. RESULTS: Both operations significantly improved the radiographic parameters, except for the lateral talocalcaneal angle in the CLO group. Pedobarographic study demonstrated an elevation of the medial longitudinal arch and an improved foot-pressure distribution after both surgeries. The plantar pressure in the lateral forefoot significantly increased only in the DA group, while the pressures exerted on the medial forefoot and hindfoot and the arch index improved only in the CLO group. CONCLUSIONS: Both CLO and DA effectively improve the foot alignments of the deformity in patients with generalised joint hypermobility. However, differences were observed in the changes in the lateral talocalcaneal angle and plantar pressure distribution between the two procedures. LEVEL OF EVIDENCE: Therapeutic Level III.

Resonant inelastic X-ray scattering endstation at the 1C beamline of Pohang Light Source II.

An endstation for resonant inelastic X-ray scattering (RIXS), dedicated to operations in the hard X-ray regime, has been constructed at the 1C beamline of Pohang Light Source II. At the Ir L3-edge, a total energy resolution of 34.2 meV was achieved, close to the theoretical estimation of 34.0 meV, which considers factors such as the incident energy bandpass, intrinsic analyzer resolution, geometrical broadening of the spectrometer, finite beam-size effect and Johann aberration. The performance of the RIXS instrument is demonstrated by measuring the RIXS spectra of Sr2IrO4. The endstation can be easily reconfigured to measure energy-integrated intensities with very low background for diffuse scattering and diffraction experiments.

Extreme UV Resist Exhibiting Synergism between Chemical and Physical Crosslinking Mechanisms.

Carbon-fluorine bonds in fluorinated molecules can undergo homolytic cleavage reactions when electrons are injected, and the resulting radicals combine to form network structures characterized by reduced solubility. This crosslinking chemistry suggests a new category of patterning materials that function under electron beam (e-beam) and extreme ultraviolet (EUV) lithographic conditions. Although this chemistry enables the production of 50 nm or smaller-sized features of simple fluoroalkylated polymers, it is limited by the need for relatively large amounts of irradiation energy to achieve required solubility changes. Therefore, this study was undertaken to devise a sensitivity-enhancing strategy based on a synergistic combination of radical crosslinking and hydrogen-bonding interactions between highly fluoroalkylated copolymers. An alternating copolymer was synthesized using tert-butoxystyrene and a fluoroalkylated maleimide, the former of which produces active hydrogens through catalytic acidolysis reactions. When the polymer was blended with a catalytic amount of a photoacid generator and subjected to lithographic patterning tests under e-beam and EUV irradiation, the deprotection reactions of tert-butoxy moieties proceeded at room temperature and led to a solubility decrease. We presume the small number of hydroxyl moieties produced formed an intermolecular hydrogen-bonding network, which acted synergistically with the covalent crosslinks generated by C-F bonds. When 30 nm features of copolymer thin films were fabricated by EUV lithography, sensitivity was improved by 25-34% without significant deterioration of pattern quality, especially line-edge roughness. These results demonstrate that EUV resists with improved patterning capabilities can be achieved by combining catalytic acidolysis reactions and noncatalytic crosslinking chemistry.