SiO2 Single Layers Research Articles

Corrosion resistance properties and hydrogen embrittlement protection efficiency of single-layer and multi-layer metal and ceramic films deposited on SS316L substrates

Hydrogen is a promising source of clean energy. However, the tanks used to store hydrogen fuel are prone to hydrogen embrittlement and are thus at risk of stress cracking and catastrophic failure. Accordingly, this study deposited single-layer and double-layer Zr, Al, SiO2, Al2O3, Al@Al2O3, and Al@SiO2 films on 316L stainless steel substrates and examined their feasibility as protective coatings by measuring their anti-corrosion properties and hydrogen permeation currents. The results showed that the single-layer Al2O3 film had a higher corrosion resistance than the single-layer SiO2 film and bare 316L substrate. Among all the coatings, the Al@Al2O3 double-layer coating exhibited the highest protection efficiency of 95%. Moreover, it showed the lowest hydrogen penetration current density (1.08 x 10-3 A/cm2), the longest hydrogen embrittlement time (16000 s), and the lowest hydrogen content (0.008 mol/cm3). In other words, the Al@Al2O3 double-layer coating combined superior corrosion resistance with excellent hydrogen permeation suppression. Consequently, it is a promising material for enhancing the safety and longevity of hydrogen storage tanks in practical applications.

Theoretical Analysis and Simulation of SiO2 and ZrO2 Based Antireflective Coatings to Improve Crystalline Silicon Solar Cell Efficiency

The Solar cell efficiency is crucial, and optical losses can hinder it significantly. Anti-reflective coatings are effective in minimizing these losses. In our study, we used Fresnel equations to calculate reflectance values for single-layer SiO2, ZrO2, a SiO2-ZrO2 mixture, and a double-layer SiO2/ZrO2 configuration. We then assessed their impact on crystalline silicon solar cells using the SCAPS program. The reflectance values of single-layer SiO2, ZrO2 and 10%SiO2-90%ZrO2 mixture were calculated as 19.17%, 13.09% and 13.01%, respectively. Notably, the double-layer SiO2/ZrO2 coating showed a low reflectance of 7.58%, a significant improvement compared to uncoated silicon at 37.45%. Efficiency values for crystalline silicon solar cells were calculated for single layer as 18,95% (SiO2), 20.39% (ZrO2), 20,40% (mixed coating) respectively and 21.68% for the double-layer SiO2/ZrO2 configuration.

Al2O3 Layers Grown by Atomic Layer Deposition as Gate Insulator in 3C-SiC MOS Devices.

Metal-oxide-semiconductor (MOS) capacitors with Al2O3 as a gate insulator are fabricated on cubic silicon carbide (3C-SiC). Al2O3 is deposited both by thermal and plasma-enhanced Atomic Layer Deposition (ALD) on a thermally grown 5 nm SiO2 interlayer to improve the ALD nucleation and guarantee a better band offset with the SiC. The deposited Al2O3/SiO2 stacks show lower negative shifts of the flat band voltage VFB (in the range of about -3 V) compared with the conventional single SiO2 layer (in the range of -9 V). This lower negative shift is due to the combined effect of the Al2O3 higher permittivity (ε = 8) and to the reduced amount of carbon defects generated during the short thermal oxidation process for the thin SiO2. Moreover, the comparison between thermal and plasma-enhanced ALD suggests that this latter approach produces Al2O3 layers possessing better insulating behavior in terms of distribution of the leakage current breakdown. In fact, despite both possessing a breakdown voltage of 26 V, the T-ALD Al2O3 sample is characterised by a higher current density starting from 15 V. This can be attributable to the slightly inferior quality (in terms of density and defects) of Al2O3 obtained by the thermal approach and, which also explains its non-uniform dC/dV distribution arising by SCM maps.

Nanostructured Aluminum Oxyhydroxide-A Prospective Support for Functional Porphyrin-Based Materials.

A method for the grafting of unsymmetrical A2BC-type 5,15-bis(4-butoxyphenyl)-10-(4-carboxyphenyl)-20-(phenanthrenoimidazolyl)-porphyrin onto the surface of nanostructured aluminum oxyhydroxide modified with a single SiO2 layer (NAOM) was successfully developed. A straightforward procedure towards surface modification of NAOM allowed us to prepare a new porphyrin-containing hybrid material. The obtained 3D heterostructure was extensively characterized using XPS, TEM and diffuse reflectance spectroscopy. Structural and morphological peculiarities of the inorganic support before and after the immobilization procedure were studied and discussed in detail. The stability of the material against leaching and the porphyrin immobilization ratio ca. 14% by weight were also revealed.

The impact of multi-layered dielectrics on the electrical performance of ZnO thin-film transistors

The electrical performance of ZnO thin film transistors (TFTs) fabricated on three different dielectric layers is investigated using an inverted staggered bottom gate thin film transistor structure. This work demonstrated the potential of integrating high-k dielectrics in ZnO TFTs in a dielectric multi-layered stack using SiO2 as the support layer for all the hero-dielectrics layers. In order to achieve this, ZnO thin film semiconducting layers were deposited at room temperature by radio frequency (RF) sputtering method and with no post deposition heat treatment, making them suitable candidates for low cost large area electronics on low temperature substrates (such as plastics). The dielectric films investigated were aluminium nitride (AlN), silicon nitride (SiN) and silicon dioxide (SiO2). The effective mobility of SiN devices was about half that observed in AlN devices. However, the dielectric layers exhibited hysteresis of approximately 0 V, 2 V and 7 V for the SiO2, AlN and SiN respectively. In addition, SiO2 TFTs have lowest threshold voltage (VT) and turn-on voltage (Von). The capacitance-voltage measurement for these device show that the flatband and threshold voltage of SiN and AlN MOS capacitors shifted towards more negative voltages instead when compared with the single layer SiO2 devices.

Effect of Laser Conditioning on Surface Modification and Laser Damage Resistance of SiO2 Antireflection Film

SiO2 sol-gel antireflection film coated on fused silica can reduce the reflection loss and improve the transmittance of the optical component, although it is still prone to laser induced damage. Laser conditioning is an effective way to improve the laser induced damage threshold (LIDT) of SiO2 sol-gel antireflection film. In this paper, single-layer SiO2 sol-gel antireflection films pretreated by triple-frequency laser with different parameters are characterized by the macroscopical parameters, such as transmittance, refractive index, and thickness. The law of surface modification and the defect removal mechanism of the SiO2 sol-gel antireflection film by laser conditioning are obtained. It is found that laser conditioning can reduce the thickness of the film and introduce densification. In addition, laser conditioning can eliminate micro-defects, such as vacancies and voids in the preparation of SiO2 sol-gel antireflection films, which is the main reason to improve the laser damage resistance of films. Finally, the laser conditioning process with three step laser energy combinations of (0.2–0.6–1.0) Fth0 (zero damage threshold) is the best one to obtain high transmittance, and excellent effects on structure modification and defect removal of films. The research in this paper provides data support for the engineering application and mechanism research of laser conditioning.

SiO2 Microsphere Array Coated by Ag Nanoparticles as Raman Enhancement Sensor with High Sensitivity and High Stability.

In this paper, a monolayer SiO2 microsphere (MS) array was self-assembled on a silicon substrate, and monolayer dense silver nanoparticles (AgNPs) with different particle sizes were transferred onto the single-layer SiO2 MS array using a liquid–liquid interface method. A double monolayer “Ag@SiO2” with high sensitivity and high uniformity was prepared as a surface-enhanced Raman scattering (SERS) substrate. The electromagnetic distribution on the Ag@SiO2 substrate was analyzed using the Lumerical FDTD (finite difference time domain) Solutions software and the corresponding theoretical enhancement factors were calculated. The experimental results show that a Ag@SiO2 sample with a AgNPs diameter of 30 nm has the maximal electric field value at the AgNPs gap. The limit of detection (LOD) is 10−16 mol/L for Rhodamine 6G (R6G) analytes and the analytical enhancement factor (AEF) can reach ~2.3 × 1013. Our sample also shows high uniformity, with the calculated relative standard deviation (RSD) of ~5.78%.

Effect of annealing on properties and performance of HfO2/SiO2 optical coatings for UV-applications.

The field of ultraviolet (UV)-laser applications is currently experiencing rapid growth in the semiconductor processing, laser micromachining and biomedical markets. Key enablers for these technologies are optical coatings used to manipulate and guide laser beams in a targeted manner. As laser power, laser fluence and pulse frequencies increase, the demands on the physical properties of the coating materials become more stringent. Ion beam sputtering is a technique that allows producing optical coatings with the low losses required in these applications. In this study, we investigate the influence of ion beam sputtering (IBS) parameters on the optical properties of HfO2 and SiO2 single layers as well as the impact of annealing duration at 475 °C for anti-reflective (AR) and highly reflective (HR) optical coatings at 355 nm. For HfO2 sputtered from a metal target the O2 flow during the coating process is a key parameter to reduce absorption. SiO2 single layers exhibit improved transmission in the UV-range as the ion beam energy for the sputtering process is reduced. Furthermore, a complex behavior for film stress, absorption, surface roughness and coating structure was unraveled as a function of annealing duration for AR- and HR-coatings at 355 nm. The reflectance of the HR-mirror after optimized annealing exceeded 99.94% at 355 nm and a high laser induced damage threshold (LIDT) of 6.9 J/cm2 was measured after 2 hours of annealing. For the AR-coating a LIDT-value of 15.7 J/cm2 was observed after 12 hours of annealing.

Characterization of thin Al2O3/SiO2 dielectric stack for CMOS transistors

This paper systematically investigates the electrical properties of thin Al2O3/SiO2 (with a target equivalent oxide thickness of 4.9 nm) as gate dielectric stack in the metal–oxide–semiconductor (MOS) capacitor. Different deposition techniques, i.e. thermal oxidation, thermal atomic layer deposition, and plasma-enhanced atomic layer deposition, are employed in the fabrication of MOS capacitors. The second derivative, Terman and conductance methods are used to extract the fixed oxide charges and interface trap densities in the MOS capacitors. Our results demonstrate that the Al2O3/SiO2 stack presents better performance in terms of negative fixed oxide charges and low interface trap density compared with the single-layer SiO2 with the similar equivalent oxide thickness about 3.9 nm. Furthermore, to evaluate the reliability of the Al2O3/SiO2 gate dielectric stack, the leakage current is analyzed. Contributions from Pool-Frenkel emission, trap-assisted tunneling, and Fowler-Nordheim mechanisms to the leakage current are detailed. Our results indicate that Al2O3/SiO2 gate dielectric stacks fabricated by plasma-enhanced atomic layer deposition Al2O3 and thermal SiO2 feature the lowest leakage current.

Improvement in the Output Power of Near-Ultraviolet LEDs of p-GaN Nanorods through SiO2 Nanosphere Mask Lithography with the Dip-Coating Method.

In this paper, the conditions of the dip-coating method of SiO2 nanospheres are optimized, and a neatly arranged single-layer SiO2 array is obtained. On this basis, a “top-down” inductively coupled plasma (ICP) technique is used to etch the p-GaN layer to prepare a periodic triangular nanopore array. After the etching is completed, the compressive stress in the epitaxial wafer sample is released to a certain extent. Then, die processing is performed on the etched LED epitaxial wafer samples. The LED chip with an etching depth of 150 nm has the highest overall luminous efficiency. Under a 100 mA injection current, the light output power (LOP) of the etched 150 nm sample is 23.61% higher than that of the original unetched sample.

Reducing light scattering of single-layer TiO2 and single-layer SiO2 optical thin films

The interface roughness of optical thin film is responsible for light scattering losses. Light scattering from optical thin films are becoming increasingly important for manufacturing high quality optical film devices. In this paper, the reducing scattering conditions of single layer optical thin films are analyzed by scattering theory. The ranges of the interfacial roughness ratio for reducing light scattering of single layer with high refractive index and low refractive index are given respectively. The optimal values of roughness ratio corresponding to zero backscattering of single layer film are given. The experimental results are in good agreement with theoretical analysis for single-layer TiO2 thin film of optical thickness λ/2 and single-layer SiO2 thin film of optical thickness λ/4.

A one-step mild acid route to fabricate high performance porous anti-reflective optical films from cationic polymeric nanolatex

Porous silica anti-reflection (AR) films are of importance in solar cells’ photon harvest. However, the usual utilized method to fabricate AR films is the two-step method since the formation of porous silica NPs (first step) and silica coating sol (second step) always require chemical systems at distinct pH values. To reduce the complexity of the process, we choose cationic emulsion as an approach to produce the porosity and propose a convenient one-step route to get high-performance antireflective films. A single layer SiO2 anti-reflective (AR) film with high optical transmittance up to 97.5% at 740 nm was fabricated from composite sol that was made from cationic emulsion nanolatex and tetraethylorthosilicate under acid catalysis condition. After calcination, the transmittance of AR coated glasses still held the transmittance of 96% at 550 nm. Composited with SiO2, Al2O3, or TiO2 sol binders, the transmittance of AR coated glasses could be recovered as high as 97.9% at 650 nm and the pencil hardness was further strengthened up to 6H. The composite sol can keep stable at least one month at ambient temperature without any visible precipitation. Therefore, the proposed method is promising for developing high-performance AR films effectively and economically.

Ultraviolet laser damage properties of single-layer SiO2 film grown by atomic layer deposition

Optical properties and ultraviolet laser damage of single-layer atomic layer deposition (ALD) SiO2 films were investigated. ALD SiO2 films of high transparency shows weak absorption at 355nm. The absorption at 355 nm measured by laser calorimeter varies linearly with the film thickness with absorption coefficient of ∼0.76 ppm/nm. Such absorption is considered originating from various point defects in ALD SiO2 film. Fourier transform infrared (FTIR) spectra confirm the presence of point defects in ALD SiO2 films including non-bridging oxygen atoms and residual OH groups. Nanosecond laser-induced damage of ALD SiO2 film at 355 nm was investigated. The damage threshold and damage morphology suggest that laser-induced damage of ALD film is associated with point defect clusters which can absorb enough laser energy to initiate micro-explosion in ALD films. Furthermore, the ALD films were conditioned with sub-nanosecond ultraviolet laser. Significant improvement in damage resistance has been demonstrated after sub-nanosecond laser conditioning. After laser conditioning to 3 J/cm2, the damage threshold of 535 nm thick ALD film increased from 5.5 J/cm2 to 14.9 J/cm2 and improved about 170%. Annealing of point defects by sub-nanosecond ultraviolet laser is supposed to be the reason for the improvement of the damage resistance.

Influence of dry etching on the properties of SiO2 and HfO2 single layers.

A comparative study was performed to investigate how etching methods and parameters affect the properties of SiO2 and HfO2 coatings. SiO2 and HfO2 single layers were prepared by electron-beam evaporation (EBE), ion-beam assisted deposition (IAD), and ion-beam sputtering (IBS). Then, ion-beam etching (IBE), reactive ion etching (RIE), and inductively coupled plasma etching (ICPE) were used to study the influence of ion bombardment energy and chemical reaction on the etching rates and properties of the prepared SiO2 and HfO2 single layers. For SiO2 coatings, chemical reaction plays a dominant role in determining the etching rates, so ICPE that has the strongest CHF3 plasma shows the highest etching rate. Moreover, all three etching methods have barely any influence on the properties of SiO2 coatings. For HfO2 coatings, the etching rates are more dependent on the ion bombardment energy, although the chemical reaction using CHF3 plasma also helps to increase the etching rates to some extent. To our surprise, the ion bombardment with energy as high as 900 V does not change the amorphous microstructure or crystalline states of prepared HfO2 coatings. However, the high-energy ion bombardment in IBE significantly increases the absorption of the HfO2 coatings prepared by all deposition techniques and decreases their laser damage resistance to different extents.

A comprehensive technique for estimation of process-induced fixed charges and effective work function of the metal gate on high- stack

An efficient generalized methodology is proposed for precise estimation of process-induced various fixed charge distributions in the dielectric layer and extraction of the effective work function (EWF) of the metal gate on double layer high-κ/SiO2 stack in metal-oxide-semiconductor (MOS) capacitors. Present technique is equally applicable for devices grown on multiple wafers with varying as well as uniform doping concentrations. The analysis is verified with experimentally obtained high-frequency capacitance–voltage (C–V) results by varying only the physical thickness of the high-κ dielectric layer on an interfacial silicon dioxide (SiO2) film of a fixed thickness in MOS devices fabricated using a wide variety of high-κ metal gate (HKMG) technologies including the recent advanced 28 nm high performance logic technology node. Presence of significant amount of positive bulk charges in the high-κ layer, negative fixed charges at the high-κ/SiO2 interface in addition to fixed oxide charges and interface traps at the Si/SiO2 interface are observed from our analysis. Furthermore, we have observed a negligible amount of bulk positive charges compared to the effective positive charges at the Si/SiO2 interface in TaN/SiO2/ capacitors. The present analysis applied on bi-layer gate stacks with different high-κ materials viz hafnium oxide (HfO2) and aluminum oxide (Al2O3) and also on single layer SiO2 dielectric processed under various conditions, reveals that RTA in N2 results nitrogen related negative oxide charges at the Si/SiO2 interface. However, annealing in N2 has no significant effect on reduction of number of interface traps at the Si/SiO2 interface.

Optical characterization of silicon dioxide thin films prepared by ion-assisted electron beam deposition

A single-layer SiO2 film is deposited using ion-assisted electron beam evaporation technique, and the deposited film is characterized using variable angle spectroscopic ellipsometry, UV–Vis–NIR spectrophotometer, coherence correlation interferometer, and Abbe refractometer as well as image processing techniques to investigate its optical and surface properties. The surface quality of the film in terms of average roughness, kurtosis, skewness, and power spectral density (PSD) is analyzed using interferometer and image processing. The refractive index of the SiO2 film is found to increase from 1.452 to 1.482 at 550 nm with increase in film thickness. This is corroborated by Abbe refractometer findings where the film refractive index is found to be 1.46490 and 1.48226 for a film thickness of 100 and 400 nm, respectively. The SiO2 film also results in reduction in average surface roughness from 35 nm of the uncoated substrate to 0.15 nm of the coated surface. Statistical indicators of surface quality extract from interferometric images such as kurtosis, skewness, and PSD and also exhibit sharp decline in their respective values of the coated surface as compared to the uncoated substrate indicating improvement in the surface quality after coating.

Effect of point defects on electronic and magnetic properties of single-layer SiO

ABSTRACTBased on spin-polarised density functional theory calculations, we investigated the effect of point defects on electronic and magnetic properties of the single-layer (SL) asymmetric washboard silicon oxide (aw-SiO). The SL-aw-SiO is a counterpart of black phosphorene, and a new candidate of two-dimensional material family. This structure is dynamically and thermally stable and is a nonmagnetic semiconductor with a direct band gap. We found that single vacancy and divacancy give rise to significant change in the electronic and magnetic properties of SL-aw-SiO. The band gap of aw-SiO can be tuned by the substitution of Si atom instead of O atom, the antisite defect, the O atom vacancy and two atom vacancies. In addition, impurity states due to the defects can occur in the band continua and hence the band gap of aw-SiO is reduced. Having an integer magnetic moment, SL-aw-SiO upon Si vacancy and by substitution of O atom instead of Si atom may display half-metallic features.

Characterictics of absorption edge of SiO 2 films

Silicon dioxide (SiO2) is one of the most widely used in various optical system as film material. The micro-structure and defects of SiO2 films are of great importance to the functions and performance of these optical systems. In this paper, the absorption edge characteristics of single layer SiO2 films prepared by electron beam evaporation, ion assisted deposition, and magnetron sputtering are investigated in detail via calculating their absorption edge spectrum, which is divided into three regions: the strong absorption, exponential absorption, and weak absorption regions. The bandgap, Urbach tail, and concentration of oxygen deficiency centers (ODC) are obtained by analyzing the measured absorption spectrum. By analyzing the bandgap, Urbach tail, and ODC data of SiO2 films prepared with different deposition techniques and annealed at different temperatures, the atomic arrangement as well as micro-defect information of SiO2 films are obtained and compared. Such information of SiO2 films are important to the preparation of high-performance optical coatings employing SiO2 as the low refractive index material.

Silica single-layer inverse opal films: large-area crack-free fabrication and the regulation of transmittance in the visible region

Crack-free large-area single-layer SiO2 inverse opal (IO) films similar to an inverse “moth's eye” structure, are fabricated. The effects of their porous structure on transmittance in the visible region are investigated.

Thermal Performance of Micro Hotplates with Novel Shapes Based on Single-Layer SiO₂ Suspended Film.

In this paper, two kinds of suspended micro hotplate with novel shapes of multibeam structure and reticular structure are designed. These designs have a reliable mechanical strength, so they can be designed and fabricated on single-layer SiO2 suspended film through a simplified process. Single-layer suspended film helps to reduce power consumption. Based on the new film shapes, different resistance heaters with various widths and thicknesses are designed. Then, the temperature uniformity and power consumption of different micro hotplates are compared to study the effect of these variables and obtain the one with the optimal thermal performance. We report the simulations of temperature uniformity and give the corresponding infrared images in measurement. The experimental temperature differences are larger than those of the simulation. Experimental results show that the lowest power consumption and the minimum temperature difference are 43 mW and 50 °C, respectively, when the highest temperature on the suspended platform (240 × 240 μm2) is 450 °C. Compared to the traditional four-beam micro hotplate, temperature non-uniformity is reduced by about 30–50%.