Sidewalls Of Structures Research Articles

Design and Fabrication of Quartz MEMS Based Double-ended Tuning Fork Resonator

This paper presents the design and fabrication of double-ended tuning fork (DETF) resonator based on quartz. DETF resonator was designed with two tines structure, due to this configuration has the advantage of providing dynamic balance. Both surface and side electrode were designed on DETF tines in order to enhance the piezoelectric effect. DETF resonator was fabricated from a quartz substrate by chemical wet etching and photolithography processes, the key feature of fabrication is to create Cr/Au metal films, which should be strong enough to withstand the aggressive quartz etchant, meanwhile, the wet etching parameters was optimized in order to reduce the sidewall structure in +X orientation which can greatly deteriorate vibrating characteristics of DETF tines. Experimental results demonstrated that the Q value would be lowered and motional resistance be increased with the force sensitivity increase of DETF tines.

Neutralizing coffee-ring effect using gradual structures for uniform particle distribution

The coffee-ring effect is a process that takes place when a tiny drop of liquid-containing particles disappears, resulting in a distinct deposit around the edge of the spill resembling a ring. One of the primary causes of this effect is the uneven distribution of particles due to dissimilar evaporation rates on the droplet surface and contact line pinning effects. In this research, a microwell with a gradual structure has been developed to regularize the slippery Wenzel wettability of the surface and control the particle distribution. The mobility and pinning of droplet contact lines during the evaporation process are greatly influenced by this structure. The uniform curvature of the sidewall structure is predisposed to contact line depinning and thus helps the sliding of droplets to further neutralize the coffee-ring effect. Contact line pinning is predominantly observed at the corners of the structure, which are encircled by the ends and bottoms of the microwell's sidewalls. The curvature changes at this point, enhancing van der Waals' forces and resulting in a uniform monolayer of sediment being deposited at the microwell's bottom. The restraining efficacy of microwells of gradual structure on coffee rings with polystyrene spheres was confirmed, and the impact of microwell diameter, particle diameter, and loading efficacy on particle deposition distribution was investigated. The results show that the gradient configuration permits a single layer and even distribution of particles, enabling the sediment's dimensions to be anticipated and evaluated.

Omnidirectional 3-D AFM Integrated With a Rotary Stage for High-Precision Sidewall Structure

Omnidirectional 3-D AFM Integrated With a Rotary Stage for High-Precision Sidewall Structure

Experimental study on vertical temperature of facade fire plume ejected from compartment constrained by adjacent single sidewall

This article presents an experimental investigation about the effect of adjacent single sidewall on temperature profile of window-ejected facade fire plume from a fire compartment. The experiments were conducted using a reduced-scale compartment with a sidewall, and the temperature profile in vertical direction of facade fire plume was recorded for various window dimensions, sidewall distances and heat release rates for a total of 70 test conditions. The experimental results show that the vertical temperature can be divided into three regions, and as vertical height Z-Zn-Z0 increases, the temperature in vertical direction keeps stable at continuous flame region, while decreases rapidly at intermittent flame- and buoyancy plume regions constrained by single sidewall as exhibiting the characteristic (Z-Zn-Z0)−1 and (Z-Zn-Z0)−5/3 variations for the two regions. As the distance between sidewall and window decreases, the flame height increases which results in an increase of the temperature at intermittent flame- and buoyancy plume regions. The facade fire plume entrainment flow field was analyzed through the CFD simulation. As the decreasing of the distance between sidewall and window, the air entrainment at the side of the single sidewall is limited, which increases the flame height. A correction factor as a function of sidewall distance as well as the vertical height was proposed to characterize the effect of sidewall on facade fire plume temperature of various conditions, and the dimensionless temperature was well correlated correspondingly. This paper reveals the effect of building sidewall structure on facade fire plume temperature and provides new data and correlation of temperature on facade of high-rise buildings.

Numerical investigation of an improved deep-hole presplitting method based on notched blasting for deep-buried high sidewall structures

Under high stress conditions, the local stress concentration in the high sidewall structure of a deeply buried powerhouse is obvious, and sidewall presplitting formation is significantly affected. For deep hole presplitting blasting (DHPB) widely used in underground powerhouse, the non-uniform stress characteristics of DHPB were first revealed through three-dimension (3D) numerical simulation, and three crack formation modes were subsequently classified. Afterwards, an improved excavation method of notched blasting fusion to DHPB was proposed to reduce the difficulty and inhomogeneity of DHPB brought by complex stress environment. A single hole 3D model was used to confirm the stronger guiding effect of notched blasting on crack expansion when the maximum principal stress direction is different from its. And the feasibility of the improved presplitting method on high sidewalls is pointed out by 3D numerical simulation. The results show that, for DHPB, the stress concentration at sidewall foot induced by powerhouse excavation causes a gradual change in its stress environment, and the horizontal lateral pressure coefficient (Ratio of transverse to axial) decreases with hole depth basically, while there may be a principal stress direction dividing point with a coefficient of 1.0. The direction of crack formation near the top of presplitting holes tends to be lateral to the powerhouse, whereas that near the bottom of presplitting holes tends to be axial to the powerhouse. This effect is exacerbated further by continuous undercutting of the lower and middle parts, resulting in more uneven pre-cracking of DHPB. The improved excavation method based on notched blasting can ensure that the notched direction is the dominant crack expansion direction among both notch cutting and maximum principal stress direction, weaken the influence of uneven stress environment on the presplitting formation, and re-achieve the good crack formation between holes of DHPB.

Experimental tests and theoretical analysis for mechanical behaviors of side wall opening construction in mined excavation subway station

The connection of subway stations to surrounding underground spaces inevitably involves opening construction in the existing underground structure. The opening construction can strongly impact the existing underground structure when there is no reserved condition. In this study, three-dimensional numerical simulation, model test, and theoretical analysis are used to analyze the mechanical behaviors of side wall opening construction in a mined excavation subway station-Xuanwumen Station of Beijing Subway Line 4. Based on the deformation and stress characteristics of the existing side wall structure, two different reinforcement measures are compared. It is found that the vertical and horizontal deformations of the existing structure caused by opening construction is −1.58 and −1.79 mm, respectively, which are lower than the subway deformation control requirements (3 mm). However, the first and third principal stress increments are 2.14 and −4.62 MPa, respectively, which are markedly higher than the control requirement (10%). A “two-step opening” method is proposed for side wall opening construction in underground structures based on the solution of complex function to the orifice problem. This theoretical method is validated by numerical simulations and model tests, achieving highly consistent results. The allowable ultimate span of side wall opening is 5.75 m without reinforcement. Findings of the present study provide a reference for the design and construction of side wall openings in similar underground spaces.

Overhang Saddle Fin Sidewall Structure for Highly Reliable DRAM Operation

Overhang Saddle Fin Sidewall Structure for Highly Reliable DRAM Operation

A multi-vortex micromixer based on the synergy of acoustics and inertia for nanoparticle synthesis

Mixing is one of the most important steps in chemical reaction, sample preparation and emulsification. However, achieving complete mixing of fluids at high throughput is still a challenge for acoustic micromixers, which are limited by the intensity of the acoustic streaming. In this study, we proposed an acoustic-inertial micromixer based on multi-vortex synergy by introducing inertia into acoustic micromixer. The device contains side-wall sharp-edge structure and contraction-expansion array structure (SCEA) in the microchannel to enhance the acoustic streaming with inertial vortices. The mixing mechanism of SCEA was explored and the mixing process showed three modes: acoustic streaming dominant mode, acoustic-inertial synergy mode and inertial vortex dominant mode. On the basis of the “vortex seed” provided by the contraction-expansion structure, stronger chaotic advection was produced by the synergy of acoustic streaming and inertial vortices (including Dean vortex and horizontal vortex). Rapider mixing (0.20 m s) and wider operating ranges (0–3000 μL/min) were achieved in SCEA at lower driving voltages compared with conventional acoustic micromixers. Finally, more homogeneous and tunable chitosan nanoparticles and shellac nanoparticles were synthesized based on this device. The micromorphology, particle size distribution and drug loading properties of the products were measured and compared. This work provides a platform for control of mixing process in specific application environments with high operational flexibility, indicating potentially wider application of SCEA in multi-functional integration of lab-on-a-chip systems.

Variance-based sensitivity analysis for the influence of residual stress on machining deformation

Sensitivity analysis is widely used in engineering design to illustrate the effect of the variations of input variables on the output response of a system efficiently. The current study proposes a novel method of variance-based sensitivity analysis to evaluate the effects of initial residual stress (IRS) and surface residual stress (SRS) on the uncertainty of machining deformation. This analysis introduced the variance as the uncertainty evaluation index and the variance contribution to reflect the effects of residual stress on machining deformation. The variance contributions were divided into two components: (1) independent contributions due to the variations from the independent portion of a variable and (2) correlated contributions due to the variations from the portion of a variable correlated with other variables. Uncertainty characteristics (variance σ 2 ) of residual stress were extracted and an analytical model for the relationship between residual stress and the bending moment was established. An importance measure matrix consisted of variance contribution of each residual stress variable was constructed. Concerning correlated residual stress variables, the effects of variances and correlation coefficients of residual stress on the variance of machining deformation were studied. Experimental work on a sidewall structure showed that the variance contribution of IRS at the surface layer was 5.3 to 17.8 times greater than SRS. Furthermore, the sensitivity analysis for correlated residual stress variables indicated that decreasing the variances of IRS and SRS (especially IRS) and keeping the values of correlation coefficients between −0.5 to 0.5 are beneficial to reduce the uncertainty of machining deformation. • A variance-based sensitivity analysis method for machining deformation was proposed. • Variance contribution reflected the effects of RS on the machining deformation. • An analytical model between bending moment and RS was proposed. • Standard deviations and correlation coefficients of RS were studied.

Analysis and Optimization of Defect Generation Due to Mechanical Stress in High-Density SRAM

Static random-access memory (SRAM) is an essential component for realizing large-scale integration (LSI). The future transition to a 48 V DC supply in datacenters and electric vehicles acting as mobile edge servers will increase the demand for a bipolar-complementary metal-oxide semiconductor-double diffused metal-oxide semiconductor with high-capacity SRAM. When we scaled and optimized an SRAM cell from 130 nm nodes to 90 nm nodes, we observed the generation of crystal defects induced by mechanical stress in the p-channel MOS active area that cannot be explained by previous models. We performed simulations using the finite element method to identify the mechanism. In our results, the edge of the narrow active area showed a large deformation compared to the middle of the active area, which can be attributed to compressive stress from the gate electrode and sidewall. The cell layout and sidewall structure were optimized to suppress this defect generation while satisfying reliability requirements, and the design can be extended to 65 nm nodes.

Pneumatically tunable optofluidic DFB dye laser using corrugated sidewalls.

Polydimethylsiloxane-based optofluidics provides a powerful platform for a complete analytical lab-on-chip. Here, we report on a novel on-chip laser source that can be integrated with sample preparation and analysis functions. A corrugated sidewall structure is integrated into a microfluidic channel to form a distributed feedback (DFB) laser using rhodamine 6G dissolved in an ethylene glycol and water solution. Lasing is demonstrated with a threshold pump power of 87.9 µW, corresponding to a pump intensity of 52.7mW/cm2. Laser threshold and output power are optimized with respect to rhodamine 6G concentration and core index and found to be in good agreement with a rate equation model. Additionally, the laser can be switched on and off mechanically using a pneumatic cell inducing positive pressure on the grating.

Early-age Shrinkage-induced Cracking Prevention of Cast-in-place Concrete of Subway Station under Marine Environmental Conditions

Early-age cracking and leakage phenomena has became a serious problem for cast-in-place concrete of underground station in marine environment, in the present work, an anti-cracking admixture (HME-V) with temperature rise inhibition and micro-expansion properties were adopted to mitigate shrinkage cracking risk. Results indicated that the usage of HME-V exhibits larger expansion behavior not only at temperature rise period but also at temperature fall period, leading to the compensation of real-time shrinkages in concrete. Meanwhile, the early adiabatic temperature rise rate can be significantly reduced with no influence on final value. As a result, the temperature peak value and average cooling rate of the field concrete were decreased by 21.0% and 24.2% respectively. In addition, the usage of HME-V displays considerable impact on early-age compressive strength and but made no difference to the later ones. As no visible cracks and water leakage were observed in the sidewall structure, this work may prove a feasible approach to prevent early-age shrinkage crack of cast-in-place concrete used for underground station.

Role of defects in the sensing mechanism of CNTFET gas sensors

In nanotechnology, understanding the effect of interfaces and defects becomes critically important in determining a material's properties and device performance. Many one-dimensional and two-dimensional materials exhibit excellent physical, electrical, thermal, and optical properties, making them highly desirable for a wide array of applications. However, their low dimensionality also means their performance can be susceptible to defects in the material and the interfaces they form with other device components. Carbon nanotubes are often used in sensing applications, typically, in a field-effect transistor configuration (CNTFET). The interface between the contact electrode metal and the nanotube forms a Schottky barrier, which plays an important role in both transistor and sensor characteristics. Modifications to this interface by the environment can modulate the barrier and produce a change in device characteristics. Transistor operation can also be modified by the presence of defects in the carbon nanotube sidewall structure. This paper explores how defects in single-wall carbon nanotubes can affect the sensing mechanism of CNTFET gas sensing devices. Gas exposure measurements were performed on as-grown near pristine (low defect) nanotube devices and compared with plasma irradiated, highly defective nanotube devices. By utilizing selective passivation to isolate structural components that contribute to the sensing mechanism, the study shows that the presence of defects, and their relative densities, has a critical role in gas sensing performance. Recognizing the presence of these defects, even in as-grown nanotubes, can help reconcile seemingly contradictory results in the literature regarding the gas sensing mechanism. This work represents an important step toward understanding the effect of both interfaces and defects for carbon nanotube sensor development.

Measurement of internal dark current in a 17 GHz accelerator structure with an elliptical sidewall

A 17 GHz single cell, standing wave, copper accelerator structure with an axisymmetric elliptical central cell sidewall was tested for internal and downstream dark current as a function of gradient up to $93\text{ }\text{ }\mathrm{MV}/\mathrm{m}$. The elliptical sidewall was predicted to suppress the internal dark current and the lower order multipactor modes as compared with a previously tested structure having a straight sidewall. During the conditioning phase of the elliptical sidewall structure, strong internal dark current generated by an $N=1$ multipactor mode was observed at gradients in the 10 to $20\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ range. After conditioning with $2.2\ifmmode\times\else\texttimes\fi{}{10}^{5}$ pulses to $93\text{ }\text{ }\mathrm{MV}/\mathrm{m}$, the $N=1$ mode was completely suppressed and no multipactor resonances were observed. The internal dark current was reduced to a comparatively low level, much smaller than in the previously studied, straight sidewall structure, in good agreement with simulations. The energy spectrum of the electrons colliding with the sidewall was measured using an isolated side dark current monitor and a bias voltage. As the conditioning progressed, the electron energy spectrum showed an increase in the concentration of lower energy electrons, also in good agreement with simulations. Studies of internal dark current may help to understand the rf conditioning and ultimate performance of high gradient accelerator structures.

Directional coupling of surface plasmon polaritons using single nano-slit with asymmetric sidewall structure and material composition.

We report on the performance of the asymmetric nano-slit that we design and fabricated with electron beam lithography (EBL) and glancing angle deposition techniques (GLAD) for directional coupling of surface plasmon polariton (SPP) on Ag surfaces. The slit structure includes asymmetric sidewalls in terms of material composition as well as structural morphology. The overall width of the slit was varied for optimization. We illuminated the slit with a focused 532nm laser beam and characterized the SPP signal on the Ag surface near the slit with nearfield scanning optical microscopy (NSOM). We demonstrate that optimal directional coupling of SPP toward either side of the slit can be achieved by selecting proper slit widths, with the best extinction ratio of 79000 ± 18000. We also carried out numerical calculations to simulate the interaction between the incident light and the slit structure. The results reproduced the experiment qualitatively. Detailed analysis of the distribution of the E-field and the time-averaged Poynting vector indicates that SPP excited on the Ag pad substructure in the slit plays an important role in the directional coupling of SPP.

The demonstration of recessed anodes AlGaN/GaN Schottky barrier diodes using microwave cyclic plasma oxidation/wet etching techniques

This paper presents the recessed anodes AlGaN/GaN Schottky barrier diodes (SBDs) using cyclic microwave plasma oxidation and wet etching techniques which were investigated to reduce the damage and contamination on the recessed GaN-based surface. A wide bandgap Ga-doped MgZnO (GMZO) sidewall layer structure was also conducted to suppress the hard breakdown mechanism at high reserve voltage. The SBD with recessed anodes and GMZO sidewall structure had specific on-resistance (RON_SP) of 1.99 mΩ cm2, turn-on voltage (VON) of 0.40 V, and breakdown voltage of 465 V. The SBDs in this study realized higher RON_SP and lower VON than that of the conventional device. In addition, the reverse recovery and low frequency noise characteristics of a SBD with recessed anode and GMZO sidewall structure were lower than those in the conventional structure because the anode metals are close to a high-density 2DEG by using recessed structure and the leakage current from the etching damages is declined by using a GMZO sidewall structure.

Full filling of mesoporous carbon nanotubes by aqueous solution at room temperature

Carbon nanotubes (CNTs) have the ideal structure to be used as templates for nanomaterials, especially for nanowires, and the tungsten nanowire is an important nanomaterial that is used as a strengthening phase. Therefore, we have proposed to apply mesoporous CNT (mCNT) as a template to prepare tungsten nanowires. However, the tungsten precursor should fill the hollow tube of mCNT firstly, and very few related studies have been reported. In this paper, we have systematically studied the filling process of ammonium metatungstate (AMT) aqueous solution. The results reveal that owing to the mesopores in the mCNT sidewall, the AMT can be encapsulated into the tube at room temperature (RT) and we can fully fill it without destroying the structure. In addition, vibration and solute concentration are also important factors. Besides, the mesoporous sidewall and hollow tubular core structure of mCNT are prerequisites to realize full filling. Furthermore, tungsten nanowires have been obtained after reduction of AMT in mCNTs.

Oxygen vacancy drift controlled three-terminal ReRAM with a reduction in operating gate bias and gate leakage current

Three-terminal structures have an advantage over two-terminal structures in logic applications and neuromorphic circuits, However, three-terminal operation based on Valence Change RAM still requires a larger gate bias to form/dissolve a conductive path between the source and the drain, especially for turning off. Here, reduction in gate bias and gate leakage current in nonvolatile operation of oxygen vacancy drift-controlled three-terminal ReRAM is demonstrated by W/Ti (gate)/TaOx (resistance switching layer)/Pt (source), Pt (drain) structure. Introduction of a Ti thin layer between W and TaOx layers prevents a conductive channel formation between gate and source/drain electrodes. Consequently, as-fabricated high resistance between gate and source/drain is kept, resulting in smaller gate leakage current. We also achieved interface engineering on a sidewall structure of Pt (source)/SiO2 (insulator)/Pt (drain) multi-layer, reducing in an operating bias from 10 V to 4 V or less.

Characterization of a self‐aligned RTD using a SiNx sidewall process for high‐speed applications

AbstractIn this article, an InP‐based self‐aligned resonant‐tunneling‐diode (RTD) using a SiNX sidewall process has been fabricated and characterized for high‐speed microwave applications. A plasma‐enhanced dry‐etch technique has been used to form a vertical emitter mesa. The measured peak currents are almost constant at a peak voltage due to negligible thermionic emission in a wide temperature range up to 125°C. The extracted series resistance of the fabricated self‐aligned RTD is 14.5 Ω, which is reduced by 27% compared with that of the nonself‐aligned RTD by reducing the spacing between emitter mesa and collector metal. To the best of authors’ knowledge, this is the first attempt to characterize a self‐aligned RTD using the dry‐etched mesa and the SiNX sidewall structure.

Chip-scale white flip-chip light-emitting diode containing indium phosphide/zinc selenide quantum dots

A method for preparing a quantum dot (QD)-white light-emitting diode (WLED) is reported. Holes were etched in the SiO2 layer deposited on the sapphire substrate of the flip-chip LED by inductively coupled plasma, and these holes were then filled with QDs. An ultraviolet-curable resin was then spin-coated on top of the QD-containing SiO2 layer, and the resin was cured to act as a protecting layer. The reflective sidewall structure minimized sidelight leakage. The fabrication of the QD-WLED is simple in preparation and compatible with traditional LED processes, which was the minimum size of the WLED chip-scale integrated package. InP/ZnS core-shell QDs were used as the converter in the WLED. A blue light-emitting diode with a flip-chip structure was used as the excitation source. The QD-WLED exhibited color temperatures from 5900 to 6400 K and Commission Internationale De L'Elcairage color coordinates from (0.315, 0.325) to (0.325, 0.317), under drive currents from 100 to 400 mA. The QD-WLED exhibited stable optoelectronic properties.