Thick SiO2 Research Articles

Surface Plasmon Enhanced Strong Exciton-Photon Coupling in Hybrid Inorganic-Organic Perovskite Nanowires.

Manipulating strong light-matter interaction in semiconductor microcavities is crucial for developing high-performance exciton polariton devices with great potential in next-generation all-solid state quantum technologies. In this work, we report surface plasmon enhanced strong exciton-photon interaction in CH3NH3PbBr3 perovskite nanowires. Characteristic anticrossing behaviors, indicating a Rabi splitting energy up to ∼564 meV, are observed near exciton resonance in hybrid perovskite nanowire/SiO2/Ag cavity at room temperature. The exciton-photon coupling strength is enhanced by ∼35% on average, which is mainly attributed to surface plasmon induced localized excitation field redistribution. Further, systematic studies on SiO2 thickness and nanowire dimension dependence of exciton-photon interaction are presented. These results provide new avenues to achieve extremely high coupling strengths and push forward the development of electrically pumped and ultralow threshold small lasers.

Interference‐Enhanced Broadband Absorption of Monolayer MoS2 on Sub‐100 nm Thick SiO2/Si Substrates: Reflection and Transmission Phase Changes at Interfaces

AbstractThe optical characteristics of MoS2 monolayers on SiO2/Si substrates with an SiO2 thickness ranging from 40 to 130 nm are investigated. The measured Raman and optical reflection spectra of the MoS2 monolayers vary considerably depending on the SiO2 thickness. The Raman peak intensity of the MoS2 monolayer on the substrate with an 80 nm thick SiO2 layer is four times larger than those in the cases of 40‐ and 130 nm thick SiO2 layers, indicating a significant difference in the absorption at the excitation wavelength. The incident light undergoes anomalous phase changes upon reflection and transmission at the highly absorbing MoS2/nonabsorbing SiO2 or air interfaces. The phase changes at these interfaces in conjunction with those induced by the propagation of light in the SiO2 layer cause complex interference, which dramatically tunes the absorption spectrum of the MoS2 layer with changing SiO2 thickness. Neither wavelength nor the incident angle of light strongly affects the interface phase change. Thus, the MoS2 monolayers on sub‐100 nm thick SiO2/Si substrates exhibit broadband omnidirectional absorption in the visible range. This work demonstrates that SiO2/Si wafers, which are the most popular substrates, allow the optical responses of MoS2 monolayers to be optimized for optoelectronic applications.

Electrochemical performance of thermally-grown SiO2 as diffusion barrier layer for integrated lithium-ion batteries

Direct integration of lithium-ion battery (LIB) with electronic devices on the same Si substrate can significantly miniaturize autonomous micro systems. For achieving direct integration, a barrier layer is essential to be inserted between LIB and the substrate for blocking Li+ diffusion. In this paper, the feasibility of thermal SiO2 film as the barrier layer is investigated by electrochemical characterization and X-ray photoelectron spectroscopy (XPS). Due to the negligible side reactions of thermal SiO2 with electrolyte, the solid electrolyte interphase (SEI) layer formed on the surface of the barrier layer is thin and the SEI content mainly consists of hydrocarbon together with slight polyethylene oxide (PEO), Li x PO y F z , and Li2CO3. Although 8-nm thermal SiO2 effectively prevents the substrate from alloying with Li+, the whole film changes to Li silicate after electrochemical cycling due to the irreversible chemical reactions of SiO2 with electrolyte. This degrades the performance of the barrier layer against the electrolyte penetration, thus leading to the existence of Li+ (in the form of F-Si-Li) and solvent decompositions (with the products of hydrocarbon and PEO) near the barrier layer/substrate interface. Moreover, it is found that the reaction kinetics of thermal SiO2 with electrolyte decrease significantly with increasing the SiO2 thickness and no reactions are found in the bulk of the 30-nm SiO2 film. Therefore, thermal SiO2 with an appropriate thickness is a promising barrier layer for direct integration.

Silicon Nanowire Based Sensors By Using Nickel-Oxide Membrane for Sarcosine Sensing

Now-a-days different kinds of bio-analytes sensing like creatinine [1], dopamine, uric acid [2], H2O2 [3] and so on using different methods like metal-insulator-metal structure, amperometric, cyclic voltammetry [2], colorimetric, capacitor-voltage [3] method has huge demand in bio-chemical industry. Sarcosine is also one type of bio-analyte that remains in human urine. Sreekumar et al. [4] have marked sarcosine as prostate cancer bio-marker. A lower range of 50 pM sarcosine is reported by Samanta et al. and Z. Heger et al. with GeOx and paramagnetic nanoparticles respectively [5-6]. In presence of sarcosine oxidase (SOx) enzyme, sarcosine produces formaldehyde (HCHO), glycine and H2O2 [5-6]. Sarcosine sensing is realized by detecting this product H2O2. We have detected sarcosine as a prostate cancer bio-marker by fabricating silicon nanowire based sensors in electrolyte-insulator-semiconductor structure (EIS). The silicon nanowires (SiNWs) are etched in chemical etching method (Fig. 1) as it has low cost, quick and easier process among the well known SiNWs growth processes like CVD, laser ablation, MBE [7], and so on. Etching was performed on n-type Si wafer in 0.02 M AgNO3 and 5 M aqueous HF solution. A 10-nm thick SiO2 layer was grown in thermal oxidation method and 300-nm thick back sides Al contact was performed by thermal evaporator. Then, a 2 nm-thick NiOx layer was deposited on it by RF sputtering. Finally, the device was patterned in photolithography and attached to printed circuit board. The SiNWs based sensors with NiOx layer show improvement in sensitivity (̴ 49 mV/pH), linearity (̴ 99.78%), drift (̴ 3.4 mV/hr) and hysteresis (̴ 3.4 mV) characteristics due to increase in surface sites. The NiOx sensing membrane shows novel nature on SiNWs as well as the chemically etched NWs are rough on surface. These results enhance the catalytic activity of the NiOx membrane. In practice planar SiO2 based sensors cannot show H2O2 sensing due to its stoichiometric structure. But the SiNWs sensor is capable of 1 nM H2O2 sensing because the Ni2+oxidation state changes to Ni3+. This sensor is also able to sense sarcosine as a prostate cancer biomarker. In presence of 25 units SOx it has detected 1 nM sarcosine with a higher shift towards negative direction (Fig. 2) because of NiOx work function changes. This novel sensor paves a way to detect prostate cancer at early state of a patient in near future. Acknowledgement: This work was supported by Ministry of Science and Technology (MOST), Taiwan under contract number: 105-2221-E-182-002. References 1) S. Roy et al., J. Alloys Comp., vol. 726, 2017, p. 30-40. 2) G. A. Tiget al., J. Appl.Electrochem., vol. 47, 2017, p. 607. 3) S. Chakrabarti et al., Phys. Chem. Chem. Phys., vol. 19, 2017, p. 25938-25948. 4) A. Sreekumar et al., Nature, vol. 457, 2009, p. 9810-8914. 5) S. Samanta et al., Sci. Rep., vol.7, 2017, p. 11240. 6) Z. Heger et al., Sci. Rep., vol. 5, 2015, p. 8868. 7) V. Schmidt et al., Adv. Mater., vol. 21, 2009, p. 2681-2702. Figure 1

Experimental Demonstration of AlN Heat Spreaders for the Monolithic Integration of Inline Phase-Change Switches

Inline phase-change switch (IPCS) devices were fabricated on top of an AlN heat spreading layer deposited on a thick SiO2 layer. The thick SiO2 emulates the inter-layer dielectric thermal properties that prevent direct integration of IPCS devices at the end of a back-end-of-line CMOS process. The AlN acts as a heat spreading layer, enabling the proper thermal quench rate despite the low thermal conductivity of the oxide underneath. Multiple AlN thicknesses were examined and shown to properly quench the device. Use of this heat spreading layer experimentally demonstrates a substrate agnostic monolithic integration scheme, where IPCS devices can be integrated at the end of any microfabrication process—regardless of the substrate or materials underneath. This is attractive for many CMOS applications, where wafer real-estate is expensive, or in III–V applications, where the wafer thermal properties are poor and vary among different technologies.

A Dual-Band Tunable Metamaterial Near-Unity Absorber Composed of Periodic Cross and Disk Graphene Arrays

A three-dimensional dual-band perfect absorber in the THz range (3–10 THz) is theoretically investigated. The absorber is composed of periodically placed cross- and disk-shaped graphene arrays on the top of a gold layer separated by a thick SiO $_{2}$ dielectric spacer. The simulated results show two absorption peaks with near-unity absorbance ( $99.923\%$ and $99.601\%$ ) at wavelengths 43.747 $\mu$ m and 69.94 $\mu$ m, respectively. Also, the absorber is insensitive to the polarization of the incident light and has a good tolerance to the incident angle whether it is TE or TM waves. Moreover, the peak wavelengths of the absorber can be flexibly modulated by varying the Fermi level $\mu _{C}$ of graphene while no need to refabricate the structure. This paper provides a new perspective for the design of graphene-based tunable multiband perfect THz absorbers, but not limited to THz absorbers, and may also be used in other THz graphene-based photonic devices.

Controlled Hybridization of Plasmonic and Optical Modes for Low-Loss Nano-Scale Optical Confinement With Ultralow Dispersion

A photonic-waveguide at real nano-scales based on the concept of hybridization of plasmonic and photonic modes is designed and fabricated. A high-index layer of silicon to control vertical and lateral confinement is introduced under the nano-confinement layer of thermally grown SiO2, which together with optimized waveguide-width provides low-loss guidance of hybrid-plasmonic-mode. A 11-nm thick SiO2 on silicon provides us an optical-confinement at real nano-scales with an acceptably low loss of 7 dB/cm. Also, the proposed device exhibits ultra-low dispersion on introducing a grating in the silicon layer. In addition, the dispersion value “crosses zero-dispersion” many times over a broad range of wavelength.

Plasmonic Absorption Enhancement in Elliptical Graphene Arrays.

In this paper, we come up with a wavelength tunable absorber which is made up of periodically elliptical graphene arrays in the far-infrared and terahertz regions. Through simulation, we find that we can increase the length of long axis of the ellipse, raise the incidence angles of TM- and TE-polarization (TM- and TE-polarization indicate the direction of the incident electric field along the direction of the x and the y axis, respectively.) within certain limits, and increase the chemical potential of graphene, so as to enhance the absorption of light in the elliptical graphene arrays. We also compare the absorption spectra of the original structure and the complementary structure, and find that the absorption of the original structure is higher than that of the complementary structure. In the end, we study the changes in the absorption rate of the double layer structure of the elliptical array with the increase in the thickness of SiO2. The elliptical array structure can be applied to tunable spectral detectors, filters and sensors at far-infrared and terahertz wavelengths.

Direct-Write Laser Greyscale Lithography for Multi-Layer Lead Zirconate Titanate Thin Films.

Direct-write laser greyscale lithography has been used to facilitate a single step patterning technique for multi-layer lead zirconate titanate (PZT) thin films. A 2.55 μm thick photoresist was patterned with a direct-write laser. The intensity of the laser was varied to create both tiered and sloped structures that are subsequently transferred into multi-layer PZT(52/48) stacks using a single Ar ion mill etch. Traditional processing requires a separate photolithography step and an ion mill etch for each layer of the substrate, which can be costly and time consuming. The novel process allows access to buried electrode layers in the multi-layer stack in a single photolithography step. The greyscale process was demonstrated on three 150 mm diameter Si substrates configured with a 0.5 μm thick SiO2 elastic layer, a base electrode of Pt/TiO2, and a stack of four PZT(52/48) thin films of either 0.25 μm thickness per layer or 0.50 μm thickness per layer, and using either Pt or IrO2 electrodes above and below each layer. Stacked capacitor structures were patterned and results will be reported on the ferroelectric and electromechanical properties using various wiring configurations and compared to comparable single layer PZT configurations.

Enhancement of confined femto-ablation at SiO2/Si interface by embedded metallic nanoparticles

Influence of doping an SiO2/Si interface with metallic nanoparticles (MNPs) on confined laser ablation and resulting structural properties of the crystalline silicon (c-Si) substrate was investigated by irradiating the composed interface with a single, tightly focused femtosecond laser pulse. Confinement ablation regime was enforced by a 10 μm–thick SiO2 layer capping the c-Si substrate. A mixture of gold (Au) and silver (Ag) nanoparticles was placed at the interface to take advantage of the presumed plasmon-induced enhancement of the incident field strength in a broad spectral range. The nanoplasmonic effect is visualised by numerical simulations utilising the mathematical apparatus of the finite-difference time-domain (FDTD) method. The structural transformations at the site of the laser-induced damage were investigated dominantly by the scanning (SEM) and high-resolution transmission (HRTEM) electron microscopes. A comparative analysis of the irradiation effects in the targets containing different combinations of the interface composing elements revealed clear and strong influence of the confinement and doping on the irradiation result. Character of the observed transformations (among others the crystal twinning) suggests dominant role of increased pressure in the process through the locally generated shock waves.

Facile synthesis of Fe-6.5wt%Si/SiO2 soft magnetic composites as an efficient soft magnetic composite material at medium and high frequencies

Fe-6.5wt%Si/SiO2 soft magnetic composites (SMCs) were successfully designed to reduce the core loss and improve the magnetic properties of Fe-6.5wt%Si alloy via the fluidized in-situ chemical vapor deposition method combined with the subsequent spark plasma sintering (SPS) process. Most conductive Fe-6.5wt%Si particles were firstly coated with SiO2 during chemical vapor deposition, and the highly compact and insulated Fe-6.5wt%Si/SiO2 SMCs were then obtained quickly by the spark plasma sintering. A 470 nm thick SiO2 insulating layer was found to exist uniformly and densely around Fe-6.5wt%Si particles in Fe-6.5wt%Si/SiO2 SMCs with the fluidized chemical vapor deposition (FCVD) process. It caused these SMCs to exhibit much higher electrical resistivity, lower core loss, and better frequency stability of permeability than those of raw Fe-6.5wt%Si compacts and Fe-6.5wt%Si/SiO2 SMCs with the conventional chemical vapor deposition (CVD) process. This new method provides a promising way to optimize the magnetic properties of soft magnetic composite materials, which can possess larger energy conversion efficiency for the electric-magnetic switching devices.

In2Ga2ZnO7 oxide semiconductor based charge trap device for NAND flash memory

The programming characteristics of charge trap flash memory device adopting amorphous In2Ga2ZnO7 (a-IGZO) oxide semiconductors as channel layer were evaluated. Metal-organic chemical vapor deposition (MOCVD) and RF-sputtering processes were used to grow a 45 nm thick a-IGZO layer on a 20 nm thick SiO2 (blocking oxide)/p++-Si (control gate) substrate, where 3 nm thick atomic layer deposited Al2O3 (tunneling oxide) and 5 nm thick low-pressure CVD Si3N4 (charge trap) layers were intervened between the a-IGZO and substrate. Despite the identical stoichiometry and other physicochemical properties of the MOCVD and sputtered a-IGZO, a much faster programming speed of MOCVD a-IGZO was observed. A comparable amount of oxygen vacancies was found in both MOCVD and sputtered a-IGZO, confirmed by x-ray photoelectron spectroscopy and bias-illumination-instability test measurements. Ultraviolet photoelectron spectroscopy analysis revealed a higher Fermi level (EF) of the MOCVD a-IGZO (∼0.3 eV) film than that of the sputtered a-IGZO, which could be ascribed to the higher hydrogen concentration in the MOCVD a-IGZO film. Since the programming in a flash memory device is governed by the tunneling of electrons from the channel to charge trapping layer, the faster programming performance could be the result of a higher EF of MOCVD a-IGZO.

Red light emitting nano-PVP fibers that hybrid with Ag@SiO2@Eu(tta)3phen-NPs by electrostatic spinning method

This work demonstrated red light emitting nano-PVP fibers that incorporated with novel three-layer nanostructure of Ag@SiO2@Eu(tta)3phen nanoparticles (Ag@SiO2@Eu(tta)3phen-NPs), and the hybrid nano-PVP fibers were fabricated via a remarkably simple electrostatic spinning method. For Ag@SiO2@Eu(tta)3phen-NPs, the thickness of SiO2 is optimized to obtain the maximum luminescent intensity, as results, the optimized thickness of SiO2 is 20 nm. And the corresponding luminescent intensity (612 nm) of the Ag@SiO2@Eu(tta)3phen-NPs is enhanced up to 10 times compared with the pure Eu(tta)3phen complex, which indicates that with 20 nm SiO2 thickness, the localized surface plasmon resonance (LSPR) effect of Ag@SiO2 exhibits highest performance for enhancing luminescence. Moreover, the luminescent PVP fibers emit bright red light under the fluorescence microscope, which definitely confirms that the microenvironment provided by PVP polymer is absolutely suitable for the fluorescent composites.

Effects of SiO2 film thickness and operating temperature on thermally-induced failures in through-silicon-via structures

In the present study, the experimental results of the thermally induced failure (fracture) time for the components of copper through‑silicon via (TSV) structures and the time for electrical current breakdown (TBD) are obtained to investigate the effects of the thickness of the SiO2 film and the operating temperature. The numerical scheme is also developed to solve the distributions of transient temperature and stress in the specimen and the equivalent stress/strain for the elements in the Ti, SiO2 and Si components of the TSV structure. The equivalent element stress solutions incorporating with the Johnson-Cook (J-C) fracture model are provided to identify the earliest failure element and time in each of these three components and the TBD of the structure via the definition for the D factor. The applied models and numerical scheme are confirmed to be trustworthy from the comparison of the numerically predicted and experimental results for these failure time parameters. The effects of the operating temperature of specimen's bottom surface and the film thickness of SiO2 on these time parameters have been evaluated precisely. The TBD time is elongated by increasing the thickness of either SiO2 or Ti film if the bottom surface is operating at a fixed temperature. The earliest failure time (tfailure) for the components of Ti, SiO2 and Si wafer and the TBD are always reduced by the rise of operating temperature.

Analysis of simplified heat transfer models for thermal property determination of nano-film by TDTR method

Heat transfer in nanostructures is of critical importance for a wide range of applications such as functional materials and thermal management of electronics. Time-domain thermoreflectance (TDTR) has been proved to be a reliable measurement technique for the thermal property determinations of nanoscale structures. However, it is difficult to determine more than three thermal properties at the same time. Heat transfer model simplifications can reduce the fitting variables and provide an alternative way for thermal property determination. In this paper, two simplified models are investigated and analyzed by the transform matrix method and simulations. TDTR measurements are performed on Al–SiO2–Si samples with different SiO2 thickness. Both theoretical and experimental results show that the simplified tri-layer model (STM) is reliable and suitable for thin film samples with a wide range of thickness. Furthermore, the STM can also extract the intrinsic thermal conductivity and interfacial thermal resistance from serial samples with different thickness.

Простой способ оценки толщины нанометровой прозрачной пленки SiO в процессе ее термовакуумного осаждения

Простой способ оценки толщины нанометровой прозрачной пленки SiO в процессе ее термовакуумного осаждения

Multiphysics THz Antenna Simulations

The electrical response of an antenna-coupled nanothermocouple depends on how well the antenna converts incident optical energy to heat, and how this heat is converted to electrical signals by the nanothermocouples. In this paper, we study by COMSOL simulations the heat dissipated in dipole antennas operating at 600 GHz to maximize the temperature at the center of the antenna where the nanothermocouples are attached. We study antennas constructed from all-Au, all-Ni, and Au with Ni center segment. We also study the heat loss into the Si substrate, and use various thicknesses of SiO2 for thermal insulation from the substrate. We also discuss our simulation setup and our symmetric, geometry-independent mesh structure to avoid a variety of simulation errors and artifacts.

Role of Oxygen in Ionic Liquid Gating on Two-Dimensional Cr2Ge2Te6: A Non-oxide Material.

Ionic liquid gating can markedly modulate a material's carrier density so as to induce metallization, superconductivity, and quantum phase transitions. One of the main issues is whether the mechanism of ionic liquid gating is an electrostatic field effect or an electrochemical effect, especially for oxide materials. Recent observation of the suppression of the ionic liquid gate-induced metallization in the presence of oxygen for oxide materials suggests the electrochemical effect. However, in more general scenarios, the role of oxygen in the ionic liquid gating effect is still unclear. Here, we perform ionic liquid gating experiments on a non-oxide material: two-dimensional ferromagnetic Cr2Ge2Te6. Our results demonstrate that despite the large increase of the gate leakage current in the presence of oxygen, the oxygen does not affect the ionic liquid gating effect on the channel resistance of Cr2Ge2Te6 devices (<5% difference), which suggests the electrostatic field effect as the mechanism on non-oxide materials. Moreover, our results show that ionic liquid gating is more effective on the modulation of the channel resistances compared to the back gating across the 300 nm thick SiO2.

Optical constants of SiO2 from 196 to 1688 nm (0.735–6.33 eV) from 20, 40, and 60 nm films of reactively sputtered SiO2 on Eagle XG® glass by spectroscopic ellipsometry

Three thicknesses of reactively sputtered SiO2, nominally 20, 40, and 60 nm, deposited on Corning Eagle XG® (EXG), an important display glass, were analyzed by spectroscopic ellipsometry. Reflection ellipsometry data from the samples were analyzed from 196 to 1688 nm at angles of 55°–60°, inclusive, in 1° increments. These angles were chosen because they bracket the Brewster angles of both EXG glass and SiO2. The backsides of the samples were roughened by sand blasting to suppress backside reflections from the substrates. A total of nine datasets were collected from nine different samples (three for each nominal thickness of SiO2), each at six different angles of incidence (54 spectra). The optical constants for each thickness of SiO2 was determined, as well as a set of constants for all the films (the material in general) via a multisample analysis (MSA). The optical constants of the SiO2 films were modeled using two poles with transparency assumed over the entire spectral range (a Sellmeier model). A Bruggeman effective medium approximation (BEMA) roughness layer was included in the model, which assumed 50/50 volume fractions that corresponded to the modeled SiO2 optical constants and void. The fit did not substantially improve when an interface layer between the Eagle XG® and the sputtered film was included, so it was omitted. Three sets of previously reported optical constants for the substrate over two wavelength ranges were considered in the modeling. The thin SiO2 films analyzed herein have very similar optical properties to those of their EXG substrate—this is a challenging analytical problem involving a transparent film on a transparent substrate. Accordingly, analysis of multiple samples, an MSA that included multiple film thicknesses analyzed at multiple angles, and an exploration of multiple modeling approaches helped ensure that the optical constants reported herein are accurate and the modeling robust. In particular, these measures helped avoid correlation between the optical constants, the layer thicknesses, and the thicknesses of the BEMA layers. Atomic force microscopy roughness measurements were made on the SiO2 films and compared to the roughness values obtained by spectroscopic ellipsometry. In summary, the authors provide here the optical constants and some accompanying physical characterization of sputtered 20–60 nm SiO2 films from 196 to 1688 nm.

Simulations of the breakdown characteristics of n-on-p backside-illumination Silicon Photomultipliers by TCAD

Abstract This paper investigates, using Synopsys Sentaurus TCAD simulation, the dependence of the breakdown voltage of n-on-p backside-illumination Silicon Photomultipliers (BSI-SiPM) on the implantation dose, the implantation energy and the screening SiO2 thickness for implantation in p-enrichment region. The simulation results indicate that the breakdown voltage decreases linearly with the implantation dose and a high implantation energy can minimize the impact of the screening SiO2 thickness on the breakdown voltage. Additionally, some key process parameters implemented in coming fabrication have been obtained.