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Strategies to facilitate the formation of free standing MoS <sub/>2</sub> nanolayers on SiO <sub/>2</sub> surface by atomic layer deposition: A DFT study
摘要： In this study, we employ density functional theory calculations to investigate the very initial formation of a buffer layer during atomic layer deposition of MoS2 at the SiO2 (001) surface. In our previous study, we described that the self-limiting atomic layer deposition (ALD) reactions using Mo(NMe2)2(NtBu)2 as precursor and H2S as co-reagent terminate in the formation of a so-called building block on the SiO2 (001) surface. This building block consists of Mo which shares bonds with the surface O of SiO2 (001) at the bottom and terminal S at the top. Electronic band structure calculations indicate that the subsequently deposited buffer-layer that is composed of these building blocks has (opto)-electrical properties that are far from the ideal situation. Based on our studies, we propose alternative ALD chemistries which lead to the formation of a so-called underpinned building block. In this cluster, the Mo atoms are underpinned by S atoms, suppressing the formation of a buffer layer. This ultimately facilitates the formation of a free standing conformal 2D-MoS2 nanolayer at the interface. Through the proposed chemistries, the opto-electrical properties of the deposited layers will be preserved.
关键词： opto-electrical properties,MoS2,SiO2,density functional theory,atomic layer deposition
更新于2025-09-10 09:29:36
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Band alignment of atomic layer deposited SiO <sub/>2</sub> on (010) (Al <sub/>0.14</sub> Ga <sub/>0.86</sub> ) <sub/>2</sub> O <sub/>3</sub>
摘要： The (AlxGa1?x)2O3/Ga2O3 system is attracting attention for heterostructure ?eld effect transistors. An important device design parameter is the choice of gate dielectric on the (AlxGa1?x)2O3 and its band alignment at the heterointerface. The valence band offset at the SiO2/(Al0.14Ga0.86)2O3 heterointerface was measured using x-ray photoelectron spectroscopy. The SiO2 was deposited by atomic layer deposition (ALD) onto single-crystal β-(Al0.14Ga0.86)2O3 grown by molecular beam epitaxy. The bandgap of the SiO2 was determined by re?ection electron energy loss spectroscopy as 8.7 eV, while high resolution XPS data of the O 1s peak and onset of elastic losses were used to establish the (Al0.14Ga0.86)2O3 bandgap as 5.0 eV. The valence band offset was determined to be 1.60 ± 0.40 eV (straddling gap, type I alignment) for ALD SiO2 on β-(Al0.14Ga0.86)2O3. The conduction band offset was 2.1 ± 0.08 eV, providing for a strong electron transport restriction.
关键词： x-ray photoelectron spectroscopy,(Al0.14Ga0.86)2O3,SiO2,atomic layer deposition,conduction band offset,band alignment,valence band offset
更新于2025-09-10 09:29:36
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Photocatalytic Studies of Tio2/Sio2 Nanocomposite Xerogels
摘要： The use of titania-silica materials in photocatalytic processes has been proposed as an alternative to the conventional TiO2 catalysts, in order to facilitate the separation of products after the reaction. However, despite the large number of research in this field, the mechanism governing the photocatalytic activity of the mixed TiO2/SiO2 oxides is not clear. Titania-Silica nanocomposite xerogels were prepared by sol-gel method. This work has been used to describe the synthesis and the photocatalytic properties of TiO2-SiO2 nanocomposite xerogel. The nanocomposite xerogels were prepared by keeping the molar ratio of TEOS:TTIP:MtOH:DIW at 1: 1:6:14 respectively and the catalysts used were HCl and NH4OH. After the preparation xerogels were characterized by FTIR, XRD, UV and LLS. All these techniques show the amorphous nature of Titania-silica xerogel.
关键词： UV,FTIR,Photocatalysis,TiO2-SiO2 mixed oxide,LLS,XRD
更新于2025-09-10 09:29:36
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Photopolymerization synthesis of polyacrylic acid dispersant with methoxysilicon end groups and its application in nano-SiO <sub/>2</sub> aqueous system
摘要： In order to improve the dispersity and stability of nano-SiO2 aqueous system with high solid content, a kind of polyacrylic acid dispersant with methoxysilicon end groups (KH590-PAA) was synthesized by photopolymerization of acrylic acid (AA) initiated with (3-mercaptopropyl)trimethoxysilane (KH-590). After adding KH590-PAA into nano-SiO2 aqueous dispersion system (20 wt% solid content), the viscosity and the curing time of the system were measured by rotational viscometer and the inverted bottle method. Moreover, the dispersion mechanism of KH590-PAA for nano-SiO2 aqueous system was researched by measuring the adsorption capacity, the particle size and the zeta potential of nanoparticles with conductivity meter, dynamic light scattering (DLS), scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The results showed that methoxysilicon groups in KH590-PAA could react with hydroxyl groups on the surface of nano-SiO2 in the process of stirring, which enhanced the adsorption capacity of the dispersant and then increased the surface charge of the particles. Therefore, electrostatic repulsion and steric hindrance effects between SiO2 nanoparticles could further be enhanced by adding the KH590-PAA dispersant, and then the nano-SiO2 aqueous system exhibited better dispersity and stability. Besides, the dispersion properties of SiO2 nanoparticles in water were closely related to the addition amount and the molecular weight of the KH590-PAA dispersant.
关键词： Dispersion,Photopolymerization,Silane coupling agent,SiO2 nanoparticle,Polyacrylic acid
更新于2025-09-10 09:29:36
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Reference Module in Materials Science and Materials Engineering || Silicon, Local Oxidation of (LOCOS)
摘要： The use of silicon as the most important semiconductor material for integrated circuits is a direct consequence of its oxidation properties. Silicon dioxide (SiO2) is a stable insulator that is used, among many other applications, for the gate oxide – the heart of the metal–oxide–semiconductor (MOS) device – and for lateral isolation of MOS and bipolar devices. The permittivity of SiO2 is around four times higher than that of air, but the stability, reproducibility, and controllability of this material are excellent, making it the best isolation material in the semiconductor industry.
关键词： Silicon dioxide (SiO2),MOS device,Local Oxidation of (LOCOS),Semiconductor,Isolation material,Silicon
更新于2025-09-10 09:29:36
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Numerical Simulation and Optimization of An a-ITZO TFT Based on a Bi-Layer Gate Dielectrics
摘要： This work is an optimization study by numerical simulation of the performance of a bottom gate amorphous indium tin zinc oxide thin film transistor (a-ITZO TFT) using SILVACO-ATLAS software. The optimization process is focused on the gate dielectric conception, namely, thicknesses, number of layers and materials. The electrical characteristics calculated are the gate capacitance per unit area (Ci), the on-current (Ion), the on–off current (Ion=Ioff ) ratio, the threshold voltage (VT), the field-effect mobility (lFE), the sub-threshold swing (SS) and the resistivity (q) of the a-ITZO channel. The obtained results indicate that using a bi-layer dielectrics (SiO2/HfO2) with a relatively high thickness (BDT ? 70 nm) improves the electrical response compared to TFT based on the mono-layer dielectric, for the same physical thickness, and the optimized outputs obtained are Ci ? 3:45 (cid:2) 10(cid:3)7 F/cm2, Ion ? 4:12 (cid:2) 10(cid:3)5 A, lFE ? 29:34 cm2 V(cid:3)1 s(cid:3)1, Ion=Ioff ? 4:67 (cid:2) 108, VT ? (cid:3) 0:45 V, SS ? 6:42 (cid:2) 10(cid:3)2 V/dec, and q ? 2:60 (cid:2) 10(cid:3)2 X cm.
关键词： Silvaco Atlas,equivalent oxide thickness,SiO2,a-ITZO,HfO2,TFT,high-k
更新于2025-09-10 09:29:36
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Effect of carbon nanotubes and carbon nanotubes - gold nanoparticles composite on the photocatalytic activity of TiO <sub/>2</sub> and TiO <sub/>2</sub> -SiO <sub/>2</sub>
摘要： Carbon nanotube (CNT) - gold (Au) nanoparticle (NP) nanocomposite was synthesized by simultaneously reducing the Au ions and depositing Au NPs on the surface of CNT. The functional groups were investigated with FT-IR spectra. From the Raman spectra, D-band and G-band of CNT were identified. As a result, the deposition of nanometer-sized Au NPs on the CNT sites was observed from the transmission electron microscope (TEM) images. The photodegradation of methylene blue (MB) in aqueous solutions was studied using various photocatalysts, including TiO2, TiO2-SiO2, CNT/TiO2, CNT/TiO2-SiO2, Au/TiO2, CNT-Au/TiO2 and CNT-Au/TiO2-SiO2 composites. The CNT addition (2%) leads to a synergic effect, improving the photoactivity of the catalysts. A possible physically-based mechanism was proposed involving the reduction of electron-hole recombination and fast electron-transfer possibility.
关键词： Gold nanoparticle,TiO2-SiO2,TiO2,Carbon nanotube,nano-photocatalysts
更新于2025-09-10 09:29:36
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Inkjet Printing of SiO2 Hollow Spheres/Polyimide Hybrid Films for Foldable Low-k ILD
摘要： We demonstrate inkjet printing as a viable method for flexible interlayer dielectrics (ILDs) films with a low dielectric constant, excellent mechanical characteristics, and thermal properties in foldable organic light emitting diodes (OLEDs). SiO2 hollow spheres (SHSs)/polyimide (PI) hybrid films were printed by SiO2 coated polystyrene (PS) ink and PI ink. The relative permittivity of the hybrid films decreased from 3.45 to 1.87. The thermally stable PI fims maintained their weight below 500 °C from the TGA result. The dielectric constant and current density retained their properties after 50,000 cycles of bending at a 1 mm bend radius. We propose that the inkjet printing of SHSs/PI hybrid films described herein is a promising approach for flexible ILDs in foldable OLEDs.
关键词： SiO2 hollow sphere,polyimide,foldable OLEDs,low-k material,inkjet printing,interlayer dielectric
更新于2025-09-10 09:29:36
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Crystal structure, microwave dielectric properties and low temperature sintering of (Al0.5Nb0.5)4+ co-substitution for Ti4+ of LiNb0.6Ti0.5O3 ceramics
摘要： The phase composition, microstructure, microwave dielectric properties of (Al0.5Nb0.5)4+ co-substitution for Ti site in LiNb0.6Ti0.5O3 ceramics and the low temperature sintering behaviors of Li2O-B2O3-SiO2 (LBS) glass were systematically discussed. XRD patterns and EDS analysis result confirmed that single phase of Li1.075Nb0.625Ti0.45O3 solid solution was formed in all component. The increase of dielectric constant (εr) is ascribed to the improvement of bulk density. The restricted growth of grain has a negative influence on quality factor (Q×f) value. The τf value could be continuously shifted to near zero as the doping content increases. Great microwave dielectric properties were obtained in LiNb0.6Ti(0.5-x)(Al0.5Nb0.5)xO3 ceramics (x = 0.10) when sintered at 1100℃ for 2 h: εr = 70.34, Q×f = 5144 GHz, τf = 4.8ppm/℃. The sintering aid, LBS glass, can effectively reduce the temperature and remain satisfied microwave performance. Excellent microwave dielectric properties for x = 0.10 were obtained with 1.0 wt. % glass: εr = 70.16, Q×f = 4153 GHz (at 4 GHz), τf = -0.65ppm/℃ when sintered at 925℃ for 2 h.
关键词： LiNb0.6Ti0.5O3 ceramics,low temperature sintering,Li2O-B2O3-SiO2 (LBS) glass,microwave dielectric properties
更新于2025-09-10 09:29:36
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Gamma ray enhanced Vis-NIR photoluminescence and cytotoxicity of biocompatible silica coated Nd3+ doped GdPO4 nanophosphors
摘要： Near infrared (NIR) emitting nanophosphors have a great potential for biomedical applications. Core nanoparticles of Nd3+ doped GdPO4@SiO2 with 3–6 nm sized spheres have been synthesized by solution combustion synthesis. The structure, morphology and luminescence properties of as synthesized nanophosphors have been examined by X-ray diffraction, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Photoluminescence spectra (PL). Upon photoexcitation at 532 nm, GdPO4:Nd3+@SiO2 emits red luminescence at 681 nm and NIR luminescence at 797 nm corresponding to 4F9/2 → 4I9/2 and 4F5/2 → 4I9/2 transitions, respectively. The luminescence intensity of nanophosphor had enhanced 2 folds on increasing the Nd3+ content from 1% to 5%. The luminescence intensity of these nanophosphors had further enhanced 2–3 folds and 8–10 folds after exposed to 150 kGy and 300 kGy of gamma radiation, respectively. In addition, this nanophosphor also exhibits high cytotoxicity against cell lines of PC-3 (Prostate cancer cells) and MCF-7 (Breast cancer cells).
关键词： Cytotoxicity,Gamma radiation,SiO2,Photoluminescence,Nanophosphors
更新于2025-09-10 09:29:36