Enhancement of silicon vacancy fluorescence intensity in silicon carbide using a dielectric cavity.

Over the past decades, spin qubits in silicon carbide (SiC) have emerged as promising platforms for a wide range of quantum technologies. The fluorescence intensity holds significant importance in the performance of quantum photonics, quantum information process, and sensitivity of quantum sensing. In this work, a dual-layer Au/SiO2 dielectric cavity is employed to enhance the fluorescence intensity of a shallow silicon vacancy ensemble in 4H-SiC. Experimental results demonstrate an effective fourfold augmentation in fluorescence counts at saturating laser power, corroborating our theoretical predictions. Based on this, we further investigate the influence of dielectric cavities on the contrast and linewidth of optically detected magnetic resonance (ODMR). There is a 1.6-fold improvement in magnetic field sensitivity. In spin echo experiments, coherence times remain constant regardless of the thickness of dielectric cavities. These experiments pave the way for broader applications of dielectric cavities in SiC-based quantum technologies.

Adsorption of oxytetracycline on subalpine meadow soil from Zoige Plateau, China: Effects of the coexisting Cu2.

Subalpine meadow soil with high moisture and humus content is a unique soil type in the Zoige Plateau. Oxytetracycline and copper are common soil contaminants which interact to form compound pollution. Oxytetracycline's adsorption on natural subalpine meadow soil and its components (humin and the soil without iron and manganese oxides) was studied in the laboratory with and without the presence of Cu2+. The effects of temperature, pH and Cu2+ concentration were documented in batch experiments, allowing deduction of the main sorption mechanisms. The adsorption process had two phases: one rapid, taking place in the first 6 h, and another slower, reaching equilibrium at around 36 h. The adsorption kinetics were pseudo-second-order, and the adsorption isotherm conformed to the Langmuir model at 25 °C. Higher concentrations oxytetracycline increased the adsorption, but higher temperature did not. The presence of Cu2+ had no effect on the equilibrium time, but the amount and rate adsorbed were much greater with Cu2+ concentration increased (except for the soil without iron and manganese oxides). The amounts adsorbed with/without Cu2+ were in the order the humin from subalpine meadow soil (7621 and 7186 µg/g) > the subalpine meadow soil (7298 and 6925 µg/g) > the soil without iron and manganese oxides (7092 and 6862 µg/g), but the difference among those adsorbents was slight. It indicates that humin is a particularly important adsorbent in the subalpine meadow soil. The amount of oxytetracycline adsorbed was greatest at pH 5-9. In addition, Surface complexation through metal bridging was the most important sorption mechanism. Cu2+ and oxytetracycline formed positively-charged complex that was adsorbed and then formed a ternary complex "adsorbent-Cu(II)-oxytetracycline", in which Cu2+ acted as a bridge. These findings provide a good scientific basis for soil remediation, and for assessing environmental health risks.

High-sensitivity silicon carbide divacancy-based temperature sensing.

Color centers in silicon carbide have become potentially versatile quantum sensors. Particularly, wide temperature-range temperature sensing has been realized in recent years. However, the sensitivity is limited due to the short dephasing time of the color centers. In this work, we developed a high-sensitivity silicon carbide divacancy-based thermometer using the thermal Carr-Purcell-Meiboom-Gill (TCPMG) method. First, the zero-field splitting D of the PL6 divacancy as a function of temperature was measured with a linear slope of -99.7 kHz K-1. The coherence times of TCPMG pulses linearly increased with the pulse number and the longest coherence time was about 21 µs, which was ten times higher than . The corresponding temperature-sensing sensitivity was 13.4 mK Hz-1/2, which was about 15 times higher than previous results. Finally, we monitored the laboratory temperature variations for 24 hours using the TCMPG pulse. The experiments pave the way for the application of silicon carbide-based high-sensitivity thermometers in the semiconductor industry, biology, and materials sciences.

Fabrication of a 100 × 100 mm2 nanometer-thick graphite pellicle for extreme ultraviolet lithography by a peel-off and camphor-supported transfer approach.

An extreme ultraviolet (EUV) lithography pellicle is used to physically protect a mask from contaminants during the EUV exposure process and needs to have a high EUV transmittance. The EUV pellicle should be fabricated using a freestanding thin film with several tens of nanometer thickness in an area of 110 × 142 mm2, which is a challenging task. Here, we propose a peel-off approach to directly detach the nanometer-thick graphite film (NGF)/Ni film from SiO2/Si wafer and significantly shorten the etching time of the Ni film. Combined with the residue-damage-free transfer method that used camphor as a supporting layer, we successfully fabricated a large-area (100 × 100 mm2) NGF pellicle with a thickness of ∼20 nm, and an EUV transmittance of ∼87.2%.

Fabrication of extreme ultraviolet lithography pellicle with nanometer-thick graphite film by sublimation of camphor supporting layer.

An extreme ultraviolet (EUV) pellicle consists of freestanding thin films on a frame; these films are tens of nanometers in thickness and can include Si, SiNX, or graphite. Nanometer-thick graphite films (NGFs), synthesized via chemical vapor deposition on a metal catalyst, are used as a pellicle material. The most common method to transfer NGFs onto a substrate or a frame is to use polymethyl methacrylate (PMMA) as a supporting layer. However, this PMMA-mediated technique involves several disadvantages in term of manufacturing NGF EUV pellicles. When removing the PMMA using acetone or O2plasma, defects or deflections can occur in the NGFs. Furthermore, PMMA residues are generally present on large-area NGFs. In this study, a transfer method using camphor instead of PMMA as the supporting layer was developed to overcome these problems. After the camphor/NGF was formed on the frame, camphor was removed via sublimation in an atmosphere of ethanol vapor. This study investigated the deposition and sublimation of camphor, and confirmed that no residue was present and no deflection or defects were observed in the NGFs. Thus, a large-area NGF pellicle was successfully fabricated using the camphor transfer process.

Stress modulates Ahi1-dependent nuclear localization of ten-eleven translocation protein 2.

Major depression disorder is one of the most common psychiatric diseases. Recent evidence supports that environmental stress affects gene expression and promotes the pathological process of depression through epigenetic mechanisms. Three ten-eleven translocation (Tet) enzymes are epigenetic regulators of gene expression that promote 5-hydroxymethylcytosine (5hmC) modification of genes. Here, we show that the loss of Tet2 can induce depression-like phenotypes in mice. Paradoxically, using the paradigms of chronic stress, such as chronic mild stress and chronic social defeat stress, we found that depressive behaviors were associated with increased Tet2 expression but decreased global 5hmC level in hippocampus. We examined the genome-wide 5hmC profile in the hippocampus of Tet2 knockout mice and identified 651 dynamically hydroxymethylated regions, some of which overlapped with known depression-associated loci. We further showed that chronic stress could induce the abnormal nuclear translocation of Tet2 protein from cytosol. Through Tet2 immunoprecipitation and mass spectrum analyses, we identified a cellular trafficking protein, Abelson helper integration site-1 (Ahi1), which could interact with Tet2 protein. Ahi1 knockout or knockdown caused the accumulation of Tet2 in cytosol. The reduction of Ahi1 protein under chronic stress explained the abnormal Ahi1-dependent nuclear translocation of Tet2. These findings together provide the evidence for a critical role of modulating Tet2 nuclear translocation in regulating stress response.