Dependence Of Deposition Rate Research Articles

Effect of SiO2 Interfacial Layer Reduction on MFSFET With 5 nm-Thick Ferroelectric Nondoped HfO2 by Deposition Rate Control

In this research, deposition rate dependence of 5 nm-thick ferroelectric nondoped HfO2 (FeND-HfO2) formed on Si(100) substrate was investigated. The equivalent oxide thickness (EOT) was decreased from 3.2 nm to 2.8 nm by increasing deposition rate of HfO2 from 5.0 nm/min to 6.0 nm/min. The subthreshold swing (SS) of 107 mV/dec. and saturation mobility (μsat) of 150 cm2/(Vs) were obtained with deposition rate of 6.0 nm/min. Furthermore, the threshold voltage (VTH) was controllable as the number of identical erase pulse of 4 V/1 μs, which suggested the VTH control of approximately 10 mV.

Pulsed direct-current reactive sputtering of high Young's modulus [002] oriented aluminum nitride thin films

This work reports a process-parameter optimization of [002] oriented high Young's modulus aluminum nitride (AlN) thin films deposited by pulsed direct current (DC) reactive sputtering method. Properties of deposited AlN films are mainly determined by the material's microstructure and morphology, which can be modulated by the process parameters. Commonly explored process parameters of reactive sputtering of AlN are substrate temperature, process pressure, gas composition, substrate type, etc. Process pressure and nitrogen concentration have the most significant influence on the topography and morphology of the film, deposited by the pulsed DC reactive sputtering method. DC pulse parameters such as pulse frequency and pulse duty cycle also influence the properties of deposited AlN films, which have been addressed in this work. The pulse frequency of 100 kHz and a duty cycle of 80% was found to be the most suitable pulse parameters. This paper also reports the voltage and current behavior and deposition rate dependence under varying process parameters and pulsed properties. Optimization of process parameters is commonly done by characterizing the deposited AlN films’ crystallinity, surface roughness, and residual stress. This work addresses the influences of process and pulse parameters on Young's modulus besides other characteristic properties of the film. The AlN films deposited with the optimized method and pulse parameters yield Young's modulus of up to 335 GPa while dropping the surface roughness to 1.2 nm.

Single-step rapid trench filling with poly-Si using concentration dependence of deposition rate under a SiHCl3–H2 system

A single-step rapid trench filling with poly-Si was demonstrated using SiHCl3, which advantageously has a high decomposition temperature and contains an etching gas. Through elementary reaction rate analysis, we found a unique condition in which the film deposition rate decreased as the source concentration increased. This negative correlation between the concentration and deposition rate is referred to in this study as NCCR. Through cross-sectional observation, we confirmed that under the NCCR condition, the trench was filled without clogging at a rate that was 60 times faster than conventional low-pressure chemical vapor deposition.

Effect of porosity on thickness uniformity of MgF2 films on spherical substrates.

Simulation based on Knudsen's law shows that film thickness uniformity above 99% can be realized on spherical substrates with optimized profiles of shadowing masks. However, a type of optical thickness nonuniformity is revealed when the masks are applied for thickness correction of MgF2 films experimentally. The optical thickness nonuniformity depends on steepness of the spherical surfaces and reaches 5% approximately for surfaces with CA/RoC = 1.22. Porosity of the MgF2 film is superimposed on Knudsen's law to interpret the optical thickness nonuniformity. For theoretical simulation, the influence of porosity on optical thickness distribution is characterized by a new parameter that describes nonlinear dependence of deposition rate on cosine function of molecular injection angles in Knudsen's law. Utilizing the optimized deposition model, optical thickness uniformity of MgF2 films approaching to or above 99% has been achieved for surfaces of different steepness in a single coating run.

Study of Ga_2O-=SUB=-3-=/SUB=- deposition by MOVPE from trimethylgallium and oxygen in a wide temperature range

Study of Ga2O3 deposition by MOVPE using trimethylgallium and oxygen was performed in a wide temperature range. It was found that for Ga2O3 deposition rate vs temperature dependence is very close to the TMGa pyrolysis in nitrogen. Kinetically-limited range for these processes corresponds to 550-700oC, that is 150oC higher, then for GaN deposition in the same reactor. Keywords: gallium oxide, MOVPE

Изучение процесса газофазного осаждения Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- из триметилгаллия и кислорода в широком интервале температур

Study of Ga2O3 deposition by MOVPE using trimethylgallium and oxygen was performed in a wide temperature range. It was found that for Ga2O3 deposition rate vs temperature dependence is very close to the TMGa pyrolysis in nitrogen. Kinetically-limited range for these processes corresponds to 550-700 C, that is 150 C higher, then for GaN deposition in the same reactor.

Influence of substrates and e-beam evaporation parameters on the microstructure of nanocrystalline and epitaxially grown Ti thin films

Titanium thin films were deposited on silicon nitride (SiNx) coated Si, NaCl, and sapphire substrates varying the deposition conditions using e-beam evaporation to investigate thin film growth modes. The microstructure and texture evolution in dependence of substrate, deposition rate, film thickness, and substrate temperature were studied using X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. Thin films obtained on SiNx and NaCl substrates were nanocrystalline, while the films deposited on sapphire transformed from nanocrystalline to single crystalline at deposition temperatures above 200 °C. Predominantly, a surface plane orientation of (0002) was observed for the single crystalline films due to the minimization of surface energy. The orientation relationship of epitaxial single crystalline films grown on C-plane sapphire substrate is found to be (0002)Ti‖(0006)Sapphire,〈112¯0〉Ti‖〈033¯0〉Sapphire. In this orientation relationship, both the total surface and strain energy of the film are minimized. The results were complemented by resistivity measurements using the four-point probe method reporting an increase from ~60 μΩ cm to ~95 μΩ cm for single crystalline and nanocrystalline films, respectively.

Bottom-Up Gold Filling of High Aspect Ratio Trenches

Bottom-up superconformal Au filling of trenches as tall as seventeen micrometers, with aspect ratios of 26, is demonstrated. Deposition is conducted in a near-neutral Na3Au(SO3)2 electrolyte containing a micromolar concentration of Bi3+, known to accelerate the Au deposition and provide void-free, bottom-up filling of smaller trenches. Electroanalytical and X-ray photoelectron spectroscopy (XPS) measurements show that a Bi surface species is responsible for the accelerated Au deposition. The adsorbed Bi has a profound effect on the morphological evolution of the surface at the concentration and potentials of interests, transitioning from the growth of isolated (111) oriented trigonal pyramidal features in its absence to the growth of smooth epitaxial deposits once the fractional coverage of Bi reaches 0.15 ± 0.02 (1σ). A non-linear dependence of Au deposition rate on Bi coverage gives rise to extended incubation prior to the onset of bottom-up feature filling. For higher transport conditions, shearing of the interface limits Bi coverage to a value of approximately 0.05 or less, which correlates with a small leakage or passive current for Au deposition. The unusual correlation of Bi coverage with hydrodynamics is consistent with the inception and localization of deposition to the most recessed, and thereby quiescent, bottom surface of the patterned trench arrays.

Electron-Beam Evaporated Superconducting Titanium Thin Films for Antenna-Coupled Transition Edge Sensors

Superconducting titanium thin films are good candidates for transition edge sensors. In this paper, we deposit titanium thin films on cooled silicon-on-insulator substrates by using electron-beam evaporation. The deposition rate dependence of the film stress, resistivity, and superconducting transition temperature are presented and analyzed. The relationship between film electrical properties and thickness is discussed. For investigating the heating influence on thin Ti films, a depth profile of oxygen diffusion in the films is also analyzed by X-ray photoelectron spectroscopy.

Rapid fabrication of superhydrophobic Al/Fe2O3 nanothermite film with excellent energy-release characteristics and long-term storage stability

One of the challenges for the application of energetic materials is their energy-retaining capabilities after long-term storage. In this study, we report a facile method to fabricate superhydrophobic Al/Fe2O3 nanothermite film by combining electrophoretic deposition and surface modification technologies. Different concentrations of dispersion solvents and additives are investigated to optimize the deposition parameters. Meanwhile, the dependence of deposition rates on nanoparticle concentrations is also studied. The surface morphology and chemical composition are characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. A static contact angles as high as 156° shows the superhydrophobicity of the nanothermite film. Natural and accelerated aging tests are performed and the thermal behavior is analyzed. Thermal analysis shows that the surface modification contributes to significantly improved energy-release characteristics for both fresh and aged samples, which is supposed to be attributed to the preignition reaction between Al2O3 shell and FAS-17. Superhydrophobic Al/Fe2O3 nanothermite film exhibits excellent long-time storage stability with 83.4% of energy left in natural aging test and 60.5% in accelerated aging test. This study is instructive to the practical applications of nanothermites, especially in highly humid environment.

Deposition of Uranium Oxide Following the Reduction in Weak Acid Solution Using Electrochemical Quartz Crystal Microbalance (EQCM)

We investigated the deposition of U(IV) following a valence change of U as electrodeposition using an electrochemical quartz crystal microbalance. When measurements of the reduction of U(VI) in a weak acid solution were performed, deposits of U(IV) were observed on the electrode surface. From deposition rates, pH dependence of deposition rates, and oxidation potentials of deposits, we proposed the following deposition mechanism. The deposition is divided into the three phases; First, in the induction phase, U(IV) produced by the disproportionation forms U(IV) hydroxide nucleus. Next, in the growth phase, U(IV) deposits begin to grow. In this phase, the deposits catalyze the reduction of U(V) to U(IV), resulting an increase in the reduction current. Finally, in the transformation phase, U(IV) hydroxide species transform into UO2 having more stable state.

Kinetic study of a novel electroless Ni[sbnd]P deposition on AZ91D magnesium alloy using nickel hypophosphite as the metal salt

A novel electroless nickel-phosphorus (NiP) process employing tetrasodium pyrophosphate and ammonium citrate as complexing agents and nickel hypophosphite as the nickel source which avoids the use of SO42− and Cl− ions was developed to improve the anti-corrosion properties of AZ91D magnesium alloy. The dependence of the electroless deposition rate on experimental parameters, the morphologies of the electroless deposit and the corrosion resistance of the electroless deposit were studied by the weight-gain method, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS), respectively. An empirical equation was formulated to predict the NiP deposition rate. The results showed that tetrasodium pyrophosphate played a major role in the deposition process, followed by ammonium citrate, nickel hypophosphite, sodium hypophosphite and pH. The NiP coating significantly enhances the corrosion resistance of AZ91D Mg alloy.

High-rate magnetron sputtering with hot target

Chromium films were deposited by cooled and hot target magnetron sputtering techniques with unbalanced magnetic field configuration at equal target power density. The dependence of deposition rates of Cr films by the hot target magnetron sputtering on the power density was a non-linear at 27.5–31.5W/cm2. The optical emission studies indicated the enhancement of deposition rates due to the evaporation of the hot Cr target. The chromium film structure was strongly depended on the factor of «hot target» and the target power density. Cr films were structured to (110) direction in the case of the hot target sputtering, for cooled target configuration – the preferred orientation was changed from (110) to (200) with the power density. Cr+ to Cr ratio and heat flow from the cathode to the substrate influenced on the coating hardness and adhesion. The Cr films with 9.84–12.79GPa and the non-cracking behavior (up to 15N) were obtained.

Flocculation in a decaying shear field and its implications for mud removal in near‐field river mouth discharges

AbstractWe measure the change in floc size in a decaying shear field that mimics the decay found in a river mouth discharge. The primary questions explored are: (1) how far from equilibrium are the flocs during the decay? And, (2) how significant are the changes in size, and hence settling velocity, brought on by the changes in shear when it comes to predicting settling flux? These questions are examined in the laboratory using a camera system that allows for flocs to be sized within a turbulent suspension. We also examine how inclusion of various approaches to account for flocculation impacts the plume concentration and deposition rates in a simple river mouth discharge model. In the experiments, flocs grew from their initial size of 20–50 μm up to 100–200 μm due only to changes in shear over time scales of decay similar to those in a small river mouth discharge. It is estimated that such growth would lead to fourfold or greater fold increase in the mud settling velocity within the first few kilometers from the river mouth, even though floc sizes were only 0.5–0.8 of their equilibrium values. The plume modeling highlights the strong dependence of the mud deposition rate on the method chosen to account for flocs, and the importance of the settling to entrainment velocity ratio in dictating plume concentrations.

On the nucleation and initial film growth of rod-like organic molecules

In this article, some fundamental topics related to the initial steps of organic film growth are reviewed. General conclusions will be drawn based on experimental results obtained for the film formation of oligophenylene and pentacene molecules on gold and mica substrates. Thin films were prepared via physical vapor deposition under ultrahigh-vacuum conditions and characterized in-situ mainly by thermal desorption spectroscopy, and ex-situ by X-ray diffraction and atomic force microscopy. In this short review article the following topics will be discussed: What are the necessary conditions to form island-like films which are either composed of flat-lying or of standing molecules? Does a wetting layer exist below and in between the islands? What is the reason behind the occasionally observed bimodal island size distribution? Can one describe the nucleation process with the diffusion-limited aggregation model? Do the impinging molecules directly adsorb on the surface or rather via a hot-precursor state? Finally, it will be described how the critical island size can be determined by an independent measurement of the deposition rate dependence of the island density and the capture-zone distribution via a universal relationship.

Experimental and numerical investigations into the transient multi-wafer batch atomic layer deposition process with vertical and horizontal wafer arrangements

This paper investigates two types of wafer arrangements, vertical and horizontal, in a multi-wafer atomic layer deposition (ALD) reactor. The growth rate of ALD deposited alumina thin film is characterized and compared experimentally and numerically. It’s found that the wafer layout influences the deposition process significantly. Vertical multi-wafer arrangement is shown superior to the horizontal arrangement in terms of film deposition rate because of the enhanced collisions between precursor molecules and wafer surfaces in vertical arrangement. Studies using three-dimensional transient numerical model of fluid dynamics and surface reaction kinetics in multi-wafer batch ALD reveal the self-limiting details on the physical and chemical nature of ALD process. First, the deposition process is shown highly “self-limited”: surface reactions in ALD are completely terminated once surface species conversion comes to the end. Second, deposition process is found under a joint influence of precursor concentration and surface site saturation status. Before deposition rate reaches its peak, the precursor concentration is dominant in determining the deposition rate, but it is largely confined by the available surface reactive sites after the peak. Position dependence of deposition rate as shown by both experiments and simulations is weak and negligible.

A Semi-Empirical Model for Tilted-Gun Planar Magnetron Sputtering Accounting for Chimney Shadowing

Integrated computational materials engineering (ICME) approaches to composition and thickness profiles of sputtered thin-film samples are the key to expediting materials exploration for these materials. Here, an ICME-based semi-empirical approach to modeling the thickness of thin-film samples deposited via magnetron sputtering is developed. Using Yamamura’s dimensionless differential angular sputtering yield and a measured deposition rate at a point in space for a single experimental condition, the model predicts the deposition profile from planar DC sputtering sources. The model includes corrections for off-center, tilted gun geometries as well as shadowing effects from gun chimneys used in most state-of-the-art sputtering systems. The modeling algorithm was validated by comparing its results with experimental deposition rates obtained from a sputtering system utilizing sources with a multi-piece chimney assembly that consists of a lower ground shield and a removable gas chimney. Simulations were performed for gun-tilts ranging from 0° to 31.3° from the vertical with and without the gas chimney installed. The results for the predicted and experimental angular dependence of the sputtering deposition rate were found to have an average magnitude of relative error of $$ 4.14\% \pm 3.02\% $$ for a 0°–31.3° gun-tilt range without the gas chimney, and $$ 2.12\% \pm 1.71\% $$ for a 17.7°–31.3° gun-tilt range with the gas chimney. The continuum nature of the model renders this approach reverse-optimizable, providing a rapid tool for assisting in the understanding of the synthesis-composition-property space of novel materials.

Deposition-rate dependence of orientation growth and crystallization of Ti thin films prepared by magnetron sputtering

The effect of deposition rate on the microstructure of Ti thin films prepared by magnetron sputtering was investigated. The microstructure of Ti thin films was characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The Ti thin films exhibit a composite structure of amorphous matrix embodied with nanocrystallines. The nanocrystallization is improved with the increase of deposition rate. XRD patterns show that the crystallographic orientation transits from random distribution to (002) preferred orientation, and this crystallographic growth texture is enhanced with increasing deposition rate. Three-dimensional hexagonal particles are formed at the deposition rate of 0.35nm/s, while flaky slices occur at the surface at larger deposition rate. Moreover, the growth process of Ti thin films controlled by the deposition rate is discussed.

In VitroAssessment of Dose Delivery Performance of Dry Powders for Inhalation

The aerosol performance of engineered porous particles (PulmoSphere™) for inhalation as a function of powder properties (particle size and density) was assessed using an idealized replica of the adult human upper respiratory tract (URT) known as the Alberta mouth-throat model. Engineered placebo powders were prepared using the PulmoSphere™ technology, which is based on spray-drying an emulsion feedstock and produces porous particles with well-controlled size and density. These placebo powders are useful surrogates for a class of potent active formulations, and covered a range of particle sizes and densities, representing a particle design space relevant to dry powder inhalers. The Alberta idealized mouth-throat model was used for in vitro measurement of oropharyngeal (mouth and throat) losses and to estimate the total lung dose for different inhalation drug products. The in vitro lung doses measured with the mouth-throat model were compared to predictions of lung dose from semi-empirical numerical models of oropharyngeal deposition. Data from the mouth-throat model and numerical models were used to rank order oropharyngeal losses and flow-rate dependence in the 1–6 kPa pressure drop range. Aerosol performance of the PulmoSphere™ powders was favored by low-particle density and large geometric size, with the oropharyngeal deposition and flow rate dependence being lower for powders with median particle diameter ≥2.5 microns. In comparison, data from lactose-blend formulations showed significantly higher oropharyngeal deposition and flow rate dependence. The idealized mouth-throat model provides a reasonable in vitro estimate of dose delivered to the lungs, and is a useful tool for studying the effect of factors such as drug/device and inhalation airflow.Copyright 2014 American Association for Aerosol Research

Plasma-Facing Material Erosion Products Formed under ITER-Like Transient Loads at QSPA-T Plasma Gun Facility

Edge-localized mode (ELM) simulation experiments were held on the quasi-stationary plasma accelerator QSPA-T to study the formation of plasma-facing material (PFM) erosion products. Parameters of the deuterium plasma heat loads in QSPA-T were close to those expected during transient events in ITER. A diagnostic system for measuring the deposition rate of the erosion products with resolution time of 0.02 ms (pulse duration 0.5 ms) was designed. It allowed defining the deposition rate dependence on time and property changes of the deposited film during the pulse. The average deposition rate in QSPA-T under exposures to ultra-short D plasmas was in the range of (0.1 to 100)×1019 at·cm2·s−1, which was much higher than that for stationary processes. It has been found that deuterium concentration in the deposited W films depends on substrate temperature and deposition rate approximately in the same way as for stationary processes. As the substrate temperature and deposition rate increased, the D/W atomic ratio in the W films decreased. For describing the evolution of the D/W ratio with the substrate temperature and the tungsten deposition rate, an empirical equation proposed by De Temmerman and Doerner (J. Nucl. Mater., 2009), but with alternative parameters, has been used.