Showing papers on "Silicon oxide published in 2022"

Synthesis, characterization and thermal conductivity of water based graphene oxide–silicon hybrid nanofluids: An experimental approach

Abstract: Hybrid nanofluids are intensively studied in the last years as the new working fluids for many heat transfer applications. In this paper, a new heat transfer fluid is manufactured and investigated. Thus, this paper aims with an experimental study involving the graphene oxide (GO)-silicon (Si)/water hybrid nanofluid. The experiments were conducted taking into account both the mixture ratio between the two components that make up the hybrid nanofluid as well as the temperature effect on the thermal conductivity. Measurements were done within the range of 25–50 °C for every 5 °C. It is found that the thermal conductivity increases both with rising temperature and with increasing graphene oxide content. A comparison of the current results with other studies reported in the open literature was performed, and also a new correlation was proposed.

Vapor-Phase Chemical Etching of Silicon Assisted by Graphene Oxide for Microfabrication and Microcontact Printing

Abstract: Chemical etching of silicon assisted by a number of catalysts is attracting increasing attention in the fabrication of silicon micro–nanostructures. In practical applications, metal-free catalysts, including carbon materials, have been focused on as alternative materials for the assisted etching of silicon. Although this anisotropic etching process is suitable for the fabrication of silicon micro–nanostructures due to its simplicity and cost effectiveness, a number of challenges remain, such as the formation of a porous layer and peeling of the catalyst by the gases produced during the etching process. We herein report vapor-phase etching assisted by graphene oxide and its mechanism in terms of reaction kinetics. By optimizing etching conditions, graphene oxide enhances the etching reaction in the vapor phase without the formation of a porous layer. We also demonstrated the formation of micrometer-sized pores in the desired areas by combining the microcontact printing of graphene oxide with silicon etching in the vapor phase.

Memristor Arrays Formed by Reversible Formation and Breakdown of Nanoscale Silica Layers on Si–H Surfaces

Abstract: Nonvolatile resistive switching, also known as the memristor effect, has emerged as an important concept in the development of neuromorphic computing. Memristive operation shares similarities to the mechanism of biological synapses, making it a promising technology for future artificial intelligence. To date, most memristor platforms are based on the resistive switching of an insulating material separating two metals. For future electrical circuitry that resembles those of synapses and neurons, memristors are likely to be integrated with materials already used in the microelectronics industry such as silicon. Here, we demonstrate a silicon-based memristor array based on creating nanoscale silicon oxide layers on silicon hydride surfaces, followed by a localized and reversible breakdown of the silicon oxide to form conducting channels. The size of an individual memristor is 30 nm, with a conductance ON/OFF ratio greater than 104 at room temperature. This work opens a new platform for realizing neuromorphic systems directly on silicon.

Quasi In Situ XPS on a SiO_xF_y Layer Deposited on Silicon by a Cryogenic Process

Abstract: A silicon oxyfluoride layer was deposited on a-Si samples using SiF 4 /O 2 plasma at different temperatures between −100°C and −40 °C. In situ X-ray photoelectron spectroscopy measurements were then performed to characterize the deposited layer. The sample was then brought back to room temperature and analyzed again. It has been shown that a temperature below −65 °C is needed to significantly enhance the physisorption of SiF x species. Hence, in this condition, a F-rich oxyfluoride layer, stable at low temperature only, is physisorbed. Above this threshold temperature, the native silicon oxide layer is fluorinated and the proportion of O in the deposited layer is higher and remains stable even when the sample is brought back to room temperature.

Low Temperature Silicon Oxide and Fluorinated Silicon Oxide Films Prepared by Plasma-Enhanced Chemical Vapor Deposition Using Disilane as Silicon Precursor.

Abstract: The deposition and characterization of the silicon oxide and fluorinated silicon oxide films, as interlevel dielectrics in microelectronics devices, prepared by plasma enhanced chemical vapor deposition at low substrate temperature using $\rm Si\sb2H\sb6$ as silicon precursor are studied. The film deposition is limited by the mass transport regime, resulting in nearly temperature independent deposition rate. The characteristics for the silicon oxide films deposited at 120$\sp\circ$C show that the film etch rate is comparable to that obtained by TEOS-based PECVD at 400$\sp\circ$C and the leakage current is comparable to that of the films deposited at 350$\sp\circ$C with conventional SiH$\sb4$ precursor. It also shows that the as-deposited silicon oxide films have 9.4% increase in the film density compared to the thermal silicon oxide films, resulting in the Si-O-Si bridging bond angle of 138$\sp\circ$. The post-metallization annealing in forming gas ambient at 400$\sp\circ$C rather than post-deposition annealing at high temperatures in N$\sb2$ is the most effective way to reduce both the oxide charge and interface trap densities, especially for devices fabricated on the native oxide-free surface. For the fluorinated silicon oxide film deposition, the optimum gas flow ratio of CF$\sb4$, as fluorine precursor, to $\rm Si\sb2H\sb6$ is observed to be in the range of 8-10. The films deposited at a flow ratio of 10 give the film a dielectric constant of 4.25 which is 12% lower than 4.88 obtained for the fluorine-free silicon oxide films. The addition of fluorine into Si-O network helps not only in reducing the effective oxide charges to as low as 1/6 of the value for the fluorine-free silicon oxide films, but also improves the breakdown property by significantly reducing early failures, resulting in the average dielectric breakdown field strength of 8.91 MV/cm. These films have a strong potential for the use as interlayer dielectric material making available a low temperature and high quality film deposition process for submicron device fabrication in the microelectronics industry.

Investigation of the RF Sputtering Process and the Properties of Deposited Silicon Oxynitride Layers under Varying Reactive Gas Conditions

Abstract: In a single process run, an amorphous silicon oxynitride layer was grown, which includes the entire transition from oxide to nitride. The variation of the optical properties and the thickness of the layer was characterized by Spectroscopic Ellipsometry (SE) measurements, while the elemental composition was investigated by Energy Dispersive Spectroscopy (EDS). It was revealed that the refractive index of the layer at 632.8 nm is tunable in the 1.48–1.89 range by varying the oxygen partial pressure in the chamber. From the data of the composition of the layer, the typical physical parameters of the process were determined by applying the Berg model valid for reactive sputtering. In our modelling, a new approach was introduced, where the metallic Si target sputtered with a uniform nitrogen and variable oxygen gas flow was considered as an oxygen gas-sputtered SiN target. The layer growth method used in the present work and the revealed correlations between sputtering parameters, layer composition and refractive index, enable both the achievement of the desired optical properties of silicon oxynitride layers and the production of thin films with gradient refractive index for technology applications.

Pinhole‐Free Ultrathin Silicon Oxide Layer by Ozone‐Dissolved Deionized Water

Abstract: The pinhole‐free silicon oxide (SiO x ) layer grown using dissolved ozone in deionized water (DI‐O3) is demonstrated. An ultrathin SiO x layer of thickness 1.53 nm ± 1.5% is grown on silicon wafer using 7 ppm DI‐O3. A four‐step methodology, including 25 wt% aq. tetramethylammonium hydroxide (TMAH) solution at 80 °C, is employed to magnify the pinhole signatures in the underlying silicon and visualized with dark‐field optical microscopy (DFOM) and scanning electron microscopy (SEM). The DFOM images show spots on the surface of wafer that originate from airborne particles, contamination, etc. SEM images reveal the absence of etch pits in silicon even after etching of SiO x /silicon in TMAH for 300 s. The minority carrier lifetime and interface states density in AlO x ‐capped SiO x /Si structure are ≥2 ms at carrier density of 1 × 1015 cm−3 and less than 2 × 1011 cm−2 eV−1, respectively.

Structure and properties of silicon nano- and microparticles obtained by electric-spark dispersion method

Abstract: Abstract Silicon nano- and microparticles obtained using electric-spark dispersion of silicon electrodes and granules in 40 wt% solution of methyl alcohol in water were investigated by ultrasoft X-ray emission spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning and transmission electron microscopies. In addition, the SiLα spectra of obtained silicon particles were modeled by superimposing the spectra of pure silicon and silicon oxide taken in certain weight ratios. It was found that the surfaces of Si nano- and microparticles obtained in 40 wt% solution of methyl alcohol in water are covered with silicon oxide and chemisorbents, while the core consists of crystalline silicon with a cubic face-centered lattice. The silicon nano- and microparticles show potential as an anode material to replace commonly used graphite electrodes. The charge capacity of the electrode based on mixture of Si nano- and microparticles with graphite powder was about 1272 mAh/g after ten cycles.

Comparative Study of Physicochemical Characteristics and Catalytic Activity of Copper Oxide over Synthetic Silicon Oxide and Silicon Oxide from Rice Husk in Non-Oxidative Dehydrogenation of Ethanol

Abstract: The article presents the results of comparative research on the physicochemical characteristics and catalytic activity of copper oxide supported on synthetic SiO2 and SiO2 (RH) from rice husk. SiO2 (RH) is more hydrophobic compared to SiO2, which leads to the concentration of copper oxide on its surface in the form of a “crust”, which is very important in the synthesis of low-percentage catalysts. According to SEM, XRD, and TPR-H2, the use of SiO2 (RH) as a carrier leads to an increase in the dispersion of copper oxide particles, which is the active center of ethanol dehydrogenation.

Selective etching of silicon nitride over silicon oxide using ClF3/H2 remote plasma

Abstract: Precise and selective removal of silicon nitride (SiNx) over silicon oxide (SiOy) in a oxide/nitride stack is crucial for a current three dimensional NOT-AND type flash memory fabrication process. In this study, fast and selective isotropic etching of SiNx over SiOy has been investigated using a ClF3/H2 remote plasma in an inductively coupled plasma system. The SiNx etch rate over 80 nm/min with the etch selectivity (SiNx over SiOy) of ~ 130 was observed under a ClF3 remote plasma at a room temperature. Furthermore, the addition of H2 to the ClF3 resulted in an increase of etching selectivity over 200 while lowering the etch rate of both oxide and nitride due to the reduction of F radicals in the plasma. The time dependent-etch characteristics of ClF3, ClF3 & H2 remote plasma showed little loading effect during the etching of silicon nitride on oxide/nitride stack wafer with similar etch rate with that of blank nitride wafer.

Hygroscopic fluorine‐doped silicon oxide thin‐film‐based large‐area three‐layered moisture barrier using a roll‐to‐roll microwave plasma‐enhanced chemical vapor deposition system

Abstract: In this study, we fabricated an optically transparent and flexible SiNx/SiOF/SiNx (NFN) moisture barrier film using a highly hygroscopic fluorine-doped silicon oxide (SiOF) thin film and a low moisture permeable silicon nitride (SiNx) thin film. The NFN three-layered moisture barrier with SiOF (SiF4/N2O gas ratio, R = 1) was deposited in an in-situ process to eliminate contamination in the atmosphere between the SiNx and SiOF thin films. The NFN moisture barrier achieved a water-vapor transmission rate (WVTR) of approximately 3.94 × 10−4 g m−2 day−1 at R = 1. Additionally, the NFN three-layered thin film showed a very high visible light transmittance of approximately 93.32% that is can be used in optical applications like display, solar cells, and so on.

Large Scale Site-Controlled Fabrication of Single Photon Emitters in Silicon Nitride Nanopillars

Abstract: A high yield (67%) method of creating single photon emitters in annealed silicon nitride on silicon oxide pillars is demonstrated. Furthermore, the SPE emitter placement precision is found to be between ±30nm- ±85nm.

Glass Transition of the Surface Monolayer of Polystyrene Films with Different Film Thicknesses and Supporting Surfaces

Abstract: Surface glass-transition temperature (Tgsurf) and transition width (W) within 1 nm of the surface were measured by monitoring a qualitative change in the contact angle or density of end-groups (by time-of-flight secondary ion mass spectrometry) with temperature. Polystyrene (PS) films with various thicknesses (h) and molecular weights were studied. For unannealed PS supported on oxide-coated silicon or poly(dimethyl siloxane) with h > ∼60 nm, Tgsurf approached a plateau value of ∼25 K below the bulk Tg; below 60 nm, Tgsurf decreased with decreasing h. Separately, W exhibited a stepwise increase when h was decreased below the radius of gyration of the polymer. Upon thermal preannealing or deposition on a PS brush or adsorbed layer, the films ceased to exhibit Tgsurf reductions or stepwise change in W. We discuss how an out-of-equilibrium density profile with a deficit near the substrate and de Gennes’ sliding mode may explain these observations.

P‐11: Effects of Ar Dilution on N 2 O/SiH 4 PECVD for the Growth of Silicon Oxide Thin Films with Improved Breakdown Voltage Characteristics

Abstract: In order to obtain a robust gate dielectric, the nitrogen atom incorporation in the silicon oxide thin film has been investigated in much prior study in recent years. Silicon oxide thin film deposition is mainly performed using SiH4-N2O plasma by the Plasma enhanced chemical vapor deposition (PECVD) system. Reducing the N2O/SiH4 gas flow ratio increases the nitrogen content in the film. However, the film uniformity dramatically deteriorates as the N2O/SiH4 ratio is decreased and this issue makes the low N2O/SiH4 ratio condition a challenging area for the process condition. In this study, to overcome this problem Argon (Ar) addition was employed to the low N2O/SiH4 ratio plasma and we found that Ar not only allows the thin film to be uniformly deposited by increasing the plasma density due to the penning effect, but also increases Si-N bond especially under the ratio of 10:1 condition. Even though the silicon oxide thin film was deposited with low N2O/SiH4 gas flow rate, the film uniformity and breakdown voltage characteristics dramatically improved by Ar dilution. In addition, LTPS p-channel TFT was fabricated by utilizing the improved silicon oxide thin film as a gate dielectric layer and it showed excellent electrical characteristics. This work would be one of the most practical solutions for robust gate dielectric deposition.

The microstructural investigation of continuous-wave laser irradiated silicon rich silicon oxide

Abstract: In this thesis, we systematically studied optical and structural properties of continuous wave laser irradiated silicon rich silicon oxide by a series of characterization methods: AFM, micro-Raman, micro-PL, HCDF, HRTEM, EDX and EELS. And we intend to give one comprehensive understanding on the correlation between properties and structures. In addition, the related kinetics of materials is explored.

Multilayer sensor structure based on porous silicon

Abstract: The work is devoted to the creation of a sensor structure based on a porous silicon membrane. The structure under study integrates a porous layer used as a gas transport layer and a gas sensitive layer of non-stoichiometric tin oxide. The paper investigates the morphology of the structure and shows the gas permeability of the membrane on porous silicon. The gas sensitivity of the test structure obtained by passing a gas-air mixture containing NO2 has been studied. Keywords: porous silicon, membrane, non-stoichiometric tin oxide, thin films, resistive gas sensor.

Maskless Lithography Using Silicon Oxide Etch-Stop Layer Induced by Megahertz Repetition Femtosecond Laser Pulses

Abstract: In this study we report a new method for maskless lithography fabrication process by a combination of direct silicon oxide etch-stop layer patterning and wet alkaline etching. A thin layer of etch-stop silicon oxide of predetermined pattern was first generated by irradiation with high repetition (MHz) ultrafast (femtosecond) laser pulses in air and at atmospheric pressure. The induced thin layer of silicon oxide is used as an etch stop during etching process in alkaline etchants such as KOH. Our proposed method has the potential to enable low-cost, flexible, high quality patterning for a wide variety of application in the field of micro- and nanotechnology, this technique can be leading to a promising solution for maskless lithography technique. A Scanning Electron Microscope (SEM), optical microscopy, Micro-Raman, Energy Dispersive X-ray (EDX) and X-ray diffraction spectroscopy were used to analyze the silicon oxide layer induced by laser pulses.