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Unipolar N-type Conduction in Black Phosphorus Induced by Atomic Layer Deposited MgO
摘要： Two-dimensional (2D) black phosphorus (BP) holds great promise for future nanoscale field-effect-transistors owing to its finite band gap and expected high carrier mobility. Nevertheless, while most studies have reported unipolar p-type or ambipolar BP transistors with a hole conduction dominance, excellent n-type transport in BP has been a critical challenge. Here, we report unipolar n-type BP transistors realized by an MgO capping layer via atomic layer deposition. By coverage with 20-nm-thick MgO, remarkable electron conduction is obtained in transistors fabricated on BP flakes of thicknesses from 2.6 to 7.6 nm, accompanied by fully suppressed hole transport. Furthermore, the unipolar electron transport is found to retain (or even improve) after a period of 6 months, with the highest extrinsic electron mobility reaching 135.9 cm2/Vs. The effective approach to realizing unipolar n-FETs of BP demonstrated in this work paves the way to the implementation of BP-based CMOS digital logic circuits.
关键词： MgO,Black phosphorus,n-type conduction,ALD,Transistors
更新于2025-09-19 17:15:36
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A query on the Mg 2p binding energy of MgO
摘要： The low Mg 2p value (47.0 eV) of MgO reported in Res Chem Intermed 44(2018)829 is carefully analyzed and discussed based on a series of X-ray photoelectron spectroscopy (XPS) experiments and literature results. Presence of carbon or ferric oxide did not change the binding energy (BE) of Mg 2p of MgO, and the Mg 2p peak of MgO should be above 49.0 eV instead of at 47.0 eV.
关键词： Mg 2p spectrum,XPS experiments,MgO
更新于2025-09-19 17:15:36
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MgO/ZnO microsphere bilayer structure towards enhancing the stability of the self-powered MAPbI3 perovskite photodetectors with high detectivity
摘要： In recent years, organic-inorganic hybrid perovskite photodetectors (PDs) have been regarded as promising next-generation PDs. However, the commercialization of the perovskite PDs still faces signi?cant challenges, one of which is the poor stability. Herein, we demonstrate MgO/ZnO microsphere (MS) bilayer structure for improving the device stability with high detectivity. In this MgO/ZnO MS bilayer, ZnO MS array sca?old can facilitate the penetration of perovskite into nano-arrays and bene?ts the light harvest e?ciency due to the special micro-sphere array structure, which behaves a big gap between aligned nanostructures. MgO passivates the interface between ZnO and perovskite, enhancing the device stability and promoting the carrier transport. Finally, our PDs with the bilayer structure exhibit high performance with the on/o? ratio of up to more than 7.0 × 104, the linear dynamic range of 87.7 dB, and the detectivity of 1.5 × 1012 Jones, all of which are better than those of the device without MgO. More importantly, the device with the bilayer structure shows better stability compared with the device without MgO. Under illumination with the optical power of 314 mW/cm2, the photocurrent of the device with MgO shows almost no attenuation after continuous illumination for 30 min. In addition, after storing in air for 15 days, the performance of the device with MgO exhibits slight attenuation and the on/o? ratio is still as high as 2.3 × 104, indicating that the device has good storage stability.
关键词： MgO passivation,Perovskite photodetector,Self-powered,ZnO microsphere
更新于2025-09-16 10:30:52
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Transition metal ion Co-Doped MgO–MgF2-GeO2:Mn4+ red phosphors for white LEDs with wider color reproduction gamut
摘要： Mn4+-activated non-rare-earth based red phosphors are excellent down conversion materials for phosphor-converted light-emitting diode (pc-LEDs) based solid-state lighting applications. However, the low quantum efficiency of Mn4+ activated red phosphors under InGaN based blue LED excitation hinders their use in phosphor-converted LEDs. To enhance the absorption at an excitation wavelength of around 420 nm in Mn4+-doped MgO-MgF2-GeO2 (MGF: Mn4+), which is a conventional red-emitting lamp phosphor, we doped MGF: Mn4+ phosphors with transition metal oxides (Sc2O3, Lu2O3, Y2O3, and La2O3) replacing MgO. When excited using 420 nm light, the absorption ratio of the synthesized phosphors with Sc2O3 (Sc-MGF:Mn4+) was 58% with an internal quantum efficiency (IQE) of 55% as compared to the 35% IQE of the pristine MGF-Mn4+ phosphor. White LEDs were fabricated using Sc-MGF-Mn4+ (red), and β-SiAlON:Eu2+ (green) on InGaN chips (λem = 450 nm) and their performance was compared to the optical performance of LEDs fabricated using K2SiF6:Mn4+ as the red phosphor. According to the National Television System Committee (NTSC) standard, the color reproduction coverage with an Sc-MGF:Mn4+ phosphor-loaded white LED was 121% by the International Commission on Illumination (CIE) 1976, and 80% by the BT.2020 standard. The coverages are 9% and 6% higher than the coverages of LEDs fabricated using K2SiF6:Mn4+ as the red phosphor according to the NTSC and BT.2020 standards, respectively. Our simple approach to enhance the IQE of Mn4+ activated phosphors by co-doping transition metal oxides can be extended to other Mn4+ activated phosphor systems for applications that require enhanced absorption, higher luminescent emission intensity, and a wider gamut of color reproduction.
关键词： MgO-MgF2-GeO2,Mn4+ activated red phosphors,Solid-state lighting,White LEDs,BT.2020
更新于2025-09-12 10:27:22
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Enhancement of efficiency and CCT uniformity for red phosphor thin films, red LEDs and laminated white LEDs based on near-ultraviolet LEDs using MgO nanoparticles
摘要： Red phosphor thin films (PTFs) with different MgO nanoparticle concentrations for near-ultraviolet (NUV) LEDs were prepared based on their strong scattering effect; red LEDs and laminated white LEDs were packaged further. SEM and XRD showed that CaAlSiN3:Eu2+ (CASN) and MgO nanoparticles were uniformly distributed in silicone resin and their crystal structure remained unchanged. The phosphor conversion efficiency (PCE) had a maximum value of 83.15% when the MgO nanoparticle concentration was 15 wt%. An increase of concentration can improve the spatial distribution uniformity of photonics for 410 nm, 627 nm and 660 nm. Fluorescence lifetime showed that the value is positively correlated with concentration change. The packaged red LED luminous flux reaches a maximum of 20.337 lm at a concentration of 15 wt%. The laminated white LED showed that the MgO nanoparticle concentration can be used to adjust the correlated color temperature (CCT) from 4322 K to 1987 K. Under similar CCT, the red phosphor concentration is only 1.83 wt%, the dosage is reduced by 56.12%, and the corresponding luminous efficiency of radiation (LER) and luminous efficiency (LE) are 296.03 lm W-1 and 73.72 lm W-1 respectively. The increase was 11.42%, the decrease was 10.14%, the color rendering index (CRI) increased from 90.6 to 91.8, and CCT uniformity increased from 82.04% to 89.27% with an increase of 8.81%. Research shows that MgO nanoparticles have potential application value in the preparation of high-quality white LEDs.
关键词： MgO nanoparticles,phosphor conversion efficiency,NUV LEDs,luminous flux,CCT uniformity,red phosphor thin films
更新于2025-09-11 14:15:04
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Preparation of visible-enhanced PbI2/MgO/ Si heterojunction photodetector
摘要： Fabrication and characterization of p-PbI2/MgO/n-Si photodetectors by pulsed laser deposition within (2.7-2.5) eV. The current-voltage and capacitance-voltage properties of PbI2/MgO/Si photodetector were investigated. The best responsivity of p-PbI2/MgO/n-Si photodetectors was ~ investigated using x-ray diffraction XRD, UV-Vis absorption and scanning electron microscope SEM. The XRD results revealed a single crystalline MgO with cubic structure along the (200) PLD under different deposition temperatures Ts were demonstrated for the first time. Structural, optical and morphological properties of nanostructured MgO and PbI2/MgO films were plane, while the PbI2 film deposited on MgO was a single crystalline with hexagonal phase along (001) plane. The optical energy gaps of PbI2 films deposited on MgO film were found to be perovskite solar cells, photodetectors, X-ray detectors, photoconductors, biological labeling and diagnostics, active matrix flat panel imagers, and γ-ray detectors [3, 4]. PbI2 films are usually prepared thermal evaporation, chemical methods, pulsed laser deposition, atomic layer deposition, and electron beam evaporation [5-8]. The wider optical energy gap MgO (7.3 eV at room temperature) is a non-toxic, high specific surface reactivity and cubic crystal structure with Fm-3m space group and transparent at the visible light. MgO films have been used in many [1, 2]. Lead iodide has been used in numerous applications, for example, light emitting diodes, Lead iodide has a hexagonal structure with optical band gap around 2.2eV at room temperature Keywords: PbI2; MgO; PLD; Heterojunction; Silicon; photodetector; Deposition temperature 0.88A/W at 410nm when the photodetector was prepared at Ts = 45°C.
关键词： Silicon,photodetector,MgO,Deposition temperature,PbI2,Heterojunction,PLD
更新于2025-09-11 14:15:04
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Resonant semiconductor laser absorption of atomic Rb in a pulsed Nd:YAG laser-induced plasma
摘要： Reactive MgO (rMgO) and supplementary cementitious materials are promising to formulate sustainable construction binders. This study compares the effect of GGBFS and FA on the properties of mortar systems containing both r-MgO and Portland cement (rMgO-PC) as binder. The experimental results reveal that the incorporation of 10% GGBFS or 10% FA increases the carbonation degree of the rMgO-PC system at rMgO replacement levels of 0%, 30%, 50% and 70%. The incorporation of 10% GGBFS or 10% FA reduces the expansion of mortars with the 0% and 30% rMgO replacement levels during the sulfate exposure. Sulfate exposure not only leads to the formation of ettringite and gypsum in the mortars with the 0% and 30% rMgO replacement levels, but also accelerates the formation of protodolomite in the 50% and 70% rMgO replacement levels. However, only the ettringite and gypsum were found to jeopardize the volume stability of carbonated mortars.
关键词： Carbonation,Volume stability,FA,GGBFS,Sulfate exposure,Reactive MgO
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - High Power, Ultrafast Yellow Laser using Fourth-Harmonic Generation of Ultrafast Mid-IR Cr <sup>2+</sup> :ZnS Laser in MgO:PPLN Crystal
摘要： The ultrafast optical radiation in the yellow spectral region is of great interest for variety of scientific and technological applications including astronomy, spectroscopy and medicine, with potential to revolutionize eye surgeries through exquisite accuracy [1, 2]. However, it is relatively difficult to access the yellow region, especially when good beam quality, high power and high efficiency are required. Till date, various types of yellow lasers have been reported [3, 4] mostly in CW regime and nanosecond timescales. Here, we report on a compact, high- power, high repetition-rate, ultrafast source of yellow radiation. Using an ultrafast Cr2+:ZnS laser of average power of 4.5 W with spectral width of Δλ=138 nm centered at 2.36 μm, producing output pulses of width ~40 fs at a repetition rate of 80 MHz, and two stage single-pass second harmonic generation (SHG), we have generated ultrafast radiation of power 1 W tunable across 577-589 nm. The schematic of the experimental setup is shown in Fig. 1(a). The single-pass SHG of Cr2+:ZnS laser in a 2 mm long 5% mol doped MgO:PPLN multi-grating crystal (Λ=33.15 - 35.25 μm), giving second harmonic (SH) pulses of 90 fs at 1.18 μm, with a maximum average power of 2.3 W at a single-pass efficiency as high as 65%. Further the 1.18 μm radiation is frequency-doubled in a 1 mm long and 0.5×1 mm2 in aperture, MgO:PPLN crystal (Λ=8.9 -9.45 μm) producing yellow radiation. The acceptance bandwidth (FWHM) and temporal walk-off length (LT) of the second crystal are calculated to be 3 nm and 288 μm, respectively. In order to optimize the focusing condition for maximum fourth harmonic generation (FHG) efficiency, we pumped the crystal at constant power of 1.3 W at 1.18 μm and recorded the fourth harmonic (FH) power as a function of focusing parameter, ξ =L/b, where, L is the length of the crystal and b=2πnw0 2/λ, w0 is the beam waist radius, n is the refractive index of the crystal and λ is the input wavelength.
关键词： Cr2+:ZnS laser,MgO:PPLN crystal,fourth-harmonic generation,ultrafast yellow laser
更新于2025-09-11 14:15:04
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Synthesis and Characterization of Li <sup>+</sup> , Ag <sup>2+</sup> and Cu <sup>2+</sup> metals doped MgO nanostructured in Gel Method
摘要： The MgO nano particles doped with alkali, Nobel and transition metals (Li+, Ag2+, Cu2+) were synthesized by gel method. The structures, morphologies and size of synthesized samples were characterized and confirmed by Powder X-ray diffraction (PXRD), Scanning Electron Microscope (SEM) and High Resolution Transmission Electron Microscope (HR-TEM). The antibacterial activity for pure and doped MgO nano particles were studied against S.auerus. Among the results, the Li+ and Cu2+ doped MgO nano particles are best inhibition against the bacterial strains due to the presence of active oxygen species.
关键词： PXRD,Nanoparticles,MgO,Strains
更新于2025-09-10 09:29:36
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Exploration of a MgO cathode for improving the intensity of pulsed discharge plasma at atmosphere
摘要： With regard to the lower density and energy of electrons in pulsed discharge plasma (PDP) at atmosphere, leading to the lower energy utilization of plasma, we propose a MgO cathode to enhance the plasma intensity according to field emission principle. The MgO cathode is prepared by an electro-depositing MgO film on a stainless steel plate. This way, the positive charges come to the cathode and accumulate on the surface of the MgO film, leading to the enhancement of the electric field intensity between the cathode and MgO film, and result in the strong emission of secondary electrons from the MgO cathode. As a result, the intensity of plasma can be enhanced. Herein, the effect of the MgO cathode on the intensity of PDP is investigated. It was shown that the discharge peak current was improved by 20% compared with that of without the MgO cathode. With increasing the MgO film thickness, discharge intensity, including the peak current, transforming charge and spectrum intensity first increased and then decreased. Higher enhancement of peak current, transforming charge and spectrum intensity were acquired with a higher peak voltage. Compared to a cathode without MgO film, the ozone production is higher with MgO cathode employed. The research proposes a novel approach for improving the intensity of discharge plasma, and also provides a reference for further application of PDP.
关键词： discharge intensity,secondary electron emission,pulsed discharge plasma,MgO cathode
更新于2025-09-10 09:29:36