Kinetic Monte Carlo simulation of growth of BaTiO_3 thin film via pulsed laser deposition

Considering the characteristics of perovskite structure, a kinetic Monte Carlo(KMC) model, in which Born-Mayer- Huggins(BMH) potential was introduced to calculate the interatomic interactions and the bonding ratio was defined to reflect the crystallinity, was developed to simulate the growth of BaTiO3 thin film via pulsed laser deposition(PLD). Not only the atoms deposition and adatoms diffusion, but also the bonding of adatoms were considered distinguishing with the traditional algorithm. The effects of substrate temperature, laser pulse repetition rate and incident kinetic energy on BaTiO3 thin film growth were investigated at submonolayer regime. The results show that the island density decreases and the bonding ratio increases with the increase of substrate temperature from 700 to 850 K. With the laser pulse repetition rate increasing, the island density decreases while the bonding ratio increases. With the incident kinetic energy increasing, the island density decreases except 6.2 eV<Ek<9.6 eV, and the bonding ratio increases at Ek<9.6 eV. The simulation results were discussed compared with the previous experimental results.

SELF ASSEMBLY OF ABC TRIBLOCK COPOLYMER THIN FILMS ON A BRUSH-COATED SUBSTRATE

Self assemblies of ABC triblock copolymer thin films on a densely brush-coated substrate were investigated by using the self-consistent field theory.The middle block B and the coated polymer form one phase and the alternating phase A and phase C occur when the film is very thin either for the neutral or selective hard surface(which is opposite to the brushcoated substrate).The lamellar phase is stable on the hard surface when it is neutral and interestingly,the short block tends to stay on this hard surface...

The multiscale simulation of metal organic chemical vapor deposition growth dynamics of GaInP thin film

As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin film. By combining the computational fluid dynamics (CFD) and the kinetic Monte Carlo (KMC) methods with virtual reality (VR) technology, this paper presents a multiscale simulation of fluid dynamics, thermodynamics, and molecular dynamics to study the growth process of GaInP thin film in a vertical MOCVD reactor. The results of visualization truly and intuitively not only display the distributional properties of the gas’ thermal and flow fields in a MOCVD reactor but also display the process of GaInP thin film growth in a MOCVD reactor. The simulation thus provides us with a fundamental guideline for optimizing GaInP MOCVD growth.

Kinetic Monte Carlo simulation of physical vapor deposition of thin Cu film

A two-dimensional Kinetic Monte Carlo method has been developed for simulating the physical vapor deposition of thin Cu films on Cu substrate. An improved embedded atom method was used to calculate the interatomic potential and determine the diffusion barrier energy and residence time. Parameters, including incident angle,deposition rate and substrate temperature, were investigated and discussed in order to find their influences on the thin film morphology.

Enhanced Property of Thin Cuprous Oxide Film Prepared through Green Synthetic Route

Thin cuprous oxide films have been prepared by chemical vapor deposition(pulsed spray evaporation-chemical vapor deposition)method without post-treatment.The synthesis of cuprous oxide was produced by applying a water strategy effect.Then,the effect of water on the morphology,topology,structure,optical properties and surface composition of the obtained films has been comprehensively investigated.The results reveal that a pure phase of Cu2O was obtained.The introduction of a small quantity of water in the liquid feedstock lowers the band gap energy from 2.16 eV to 2.04 eV.This finding was mainly related to the decrease of crystallite size due to the effect of water.The topology analyses,by using atomic force microscope,also revealed that surface roughness decreases with water addition,namely more uniform covered surface.Moreover,theoretical calculations based on density functional theory method were performed to understand the adsorption and reaction behaviors of water and ethanol on the Cu2O thin film surface.Formation mechanism of the Cu2O thin film was also suggested and discussed.

Numerical investigation of particle deposition on converging slot-hole film-cooled wall

Numerical research on the dilute particles movement and deposition characteristics in the vicinity of converging slot-hole(console) was carried out, and the effect of hole shape on the particle deposition characteristics was investigated. The EI-Batsh deposition model was used to predict the particle deposition characteristics. The results show that the console hole has an obvious advantage in reducing particle deposition in comparison with cylindrical hole, especially under higher blowing ratio. The coolant jet from console holes can cover the wall well. Furthermore, the rotation direction of vortices near console hole is contrary to that near cylindrical hole. For console holes, particle deposition mainly takes place in the upstream area of the holes.

Monte Carlo Simulation of Electron Velocity Distribution and Gas Phase Process in Electron-Assisted Chemical Vapor Deposition

The gas phase process of diamond film deposition from CH4/H2 gas mixture by electron-assisted chemical vapor deposition is simulated by the Monte-Carlo method. The electron velocity distribution under different E/P (the ratio of the electric field to gas pressure) is obtained, and the velocity profile is asymmetric. The variation of the number density of CH3 and H with different CH4 concentrations and gas pressure is investigated, and the optimal experimental parameters are obtained: the gas pressure is in the range of 2.5 kPa - 15 kPa and the CH4 concentration is in the range of 0.5% - 1%. The energy carried by the fragment CH3 as the function of the experiment parameters is investigated to explain the diamond growth at low temperature. These results will be helpful to the selection of optimum experimental conditions for high quality diamond films deposition in EACVD and the modeling of plasma chemical vapor deposition.

Development and Prospect of Process Models and Simulation Methods for Atomic Layer Deposition

Thin film deposition is one of the most important processes in IC manufacturing. In this paper, several typical models and numerical simulation methods for thin film deposition and atomic layer deposition are introduced. Several modeling methods based on the characteristics of atomic layer deposition are introduced, it includes geometric method, cellular automata and multiscale simulation. The principle of each model and simulation method is explained, and their advantages and disadvantages are analyzed. Finally, the development direction of thin film deposition and atomic layer deposition modeling is prospected, and some modeling ideas are also provided.

Study on Simulation and Profile Prediction of Atomic Layer Deposition

The Atomic Layer Deposition process(ALD)is widely used in FinFET,3D-NAND and other important technologies because of its self-limiting signature and low growth temperature.In recent years,the development of computer enables chances for ALD process simulation in order to improve the process R&D efficiency.In this paper,steady state theory and vacuum pump theory are implemented to develop the growth rate algorithm of atomic layer deposition.The dynamic evolution of the deposition profile is realized based on cellular automata method,and fits the relationship between temperature and growth rate in HfO2 deposition.The model accuracy and simulation results are verified with high reliability.Based on the simulation results of this model,the influence of different substrate size and environmental dose on growth rate of pore structure is studied and analyzed.In the case of deep hole,high depth-to-width ratio hole,or when the gas entry time is below saturation,the growth rate decreases at the pore bottom.Meanwhile,the simulation considering the angle-of-inclination of the hole’s tapered sidewall indicates that the greater the angle,the better the distribution of flux.

Preparation and bioactivity of SiO_2 functional films on titanium by PACVD

SiO2 functional films were deposited on the surface of titanium by plasma assisted chemical vapour deposition(PACVD) and the composition of films was studied by XPS. Samples deposited with SiO2 films were immersed in different concentration simulated body fluid(SBF) for biomimetic deposition of hydroxyapatite(HA). The results show that SiO2 functional films deposited on titanium surface with PACVD have good bioactivity. Hydroxyapatite is formed while titanium coated with SiO2 is immersed in simulated body fluid for seven days.

换热管表面的分形表征及积灰特性数值模拟

【目的】模拟换热器管束的实际工况,研究不同粒径飞灰颗粒在粗糙管束表面的沉积特性。【方法】基于分形理论,通过改进的Weierstrass-Mandelbrot函数建立不同粗糙程度的管束表面模型,使用Fluent软件,结合用户自定义函数,分析表面形貌对流体流动的影响以及不同粒径下的颗粒沉积与碰撞特性。【结果】换热器管束表面粗糙度对壁面附近流速和湍流强度影响显著,粗糙表面会使湍流强度增大、流体速度降低,进一步加快颗粒沉积;流体压降随着管束表面粗糙度的增大而增大;相对于光滑管束表面,粗糙表面通过涡流卷吸作用增强对颗粒的捕获效果,导致颗粒具有更高的沉积率和壁面碰撞概率。【结论】飞灰颗粒的沉积与管束粗糙表面的形成具有正反馈效应,揭示表面粗糙度与颗粒沉积特性之间的内在关联。

油井内波纹板表面结垢规律及预测模型

针对油田开发过程中井下抽油泵结垢问题,采用波纹板作为泵前预结垢装置的结垢元件,分析其结垢规律。基于Kern-Seaton结垢速率模型,推导了结垢沉积的半经验公式;运用湍流-化学相互作用模型和DPM模型模拟了CaCO_(3)颗粒在管道内波纹板表面的结垢过程,定量分析了温度、流速和颗粒质量浓度的倍数对结垢速率的影响规律;复配井下产出液,进行了室内结垢试验。试验结果表明:数值模拟和室内试验有着较好的一致性,温度上升颗粒质量浓度增加,对碳酸钙的结垢沉积具有促进作用;而流速的升高则能抑制碳酸钙的结垢沉积。在实际生产过程中,井内温度和结垢离子的质量浓度不可控,可以通过适当降低产出液的流速,增加波纹板表面的结垢量,以此达到减轻抽油泵结垢的目的。所得结论可为油田防垢、除垢提供理论依据和新思路。

MOCVD生长ZnO薄膜的气相寄生反应路径研究

本文利用量子化学的密度泛函理论(DFT),研究了金属有机化学气相沉积(MOCVD)生长ZnO薄膜过程中二乙基锌(DEZn)与叔丁醇(t-BuOH)体系的气相寄生反应机理。通过计算不同温度下反应路径的Gibbs自由能变化,从热力学角度详细分析关键中间产物(HOZnOBut、H(ZnO)_(2)But、HZnOH)的水解及二聚物(Zn_(2)O_(2)H_(4)、Zn_(2)O_(4)H_(4)、Zn_(4)O_(4)H_(4))、三聚物(Zn_(3)O_(6)H_(6))的形成,揭示不利于ZnO薄膜生长的纳米颗粒可能的形成路径和产物。研究发现在高温沉积条件下(673.15 K<T<713.15 K),DEZn热解后的中间产物H(ZnO)_(2)But容易与H_(2)O发生双分子碰撞直接生成有利于ZnO薄膜生长的(ZnOH)_(2)。但是这类中间产物同时会通过聚合消去反应形成二聚物和三聚物,这些聚合物是形成纳米颗粒的重要前体,其中由HOZnOBut聚合产生的聚合物(HOZnOBut)2连续脱去C4 H8,并最终形成Zn_(2)O_(4)H_(4)的反应最容易发生。因此,二聚物Zn_(2)O_(4)H_(4)是最有可能提供纳米颗粒的重要前体。

薄膜沉积机理的计算机模拟应用和发展

薄膜技术作为材料制备的一种新技术,在现代科技领域中有着广泛应用。人们对薄膜的沉积机理通过理论和实验进行了比较深入的研究,其中计算机模拟变得日趋重要。主要阐述目前薄膜沉积机理的计算机模型:LG模型、Eden模型、DLA模型及RLA模型,相应计算机模拟技术的发展以及面临的问题和发展方向。

半球形基底镀膜膜厚均匀性理论分析

对特殊的非平面基片-半球表面上镀制薄膜的膜厚均匀性进行了理论分析研究。首先,推导了半球面静止时球面各点的膜厚方程以及此时半球面能够镀膜的区域。然后推算了半球表面沿通过球心竖直方向的轴转动后球面各位置处的膜厚方程,另外当蒸发源与球心的水平距离小于半球面半径时,存在一定区域无法镀膜,对该区域进行了理论计算。最后通过计算相对膜厚分析了半球表面膜层厚度分布情况。选择合适的蒸发源与基底间的几何配置可获得小范围内相对较为均匀的镀膜区域。该研究工作对半球面这种复杂的非平面基片上镀膜膜厚均匀性研究工作具有理论指导意义,同时对改善此种表面上的膜厚分布研究提供了相关的理论依据。

HFCVD衬底三维温度场有限元法模拟

热丝化学气相沉积(Hot filament chemical vapor deposition,HFCVD)方法制备金刚石薄膜设备简单,成本低廉,适合大面积金刚石膜的产业化生产,其中衬底温度是沉积高质量CVD金刚石膜的重要参数之一。基于此,首先分析大面积HFCVD系统的热交换过程,建立大面积HFCVD系统衬底温度场的三维有限元模型。与传统纯热辐射模型相比,本模型更加接近实际系统,并较好符合试验测定的结果。根据三维有限元模型开展对大面积HFCVD系统衬底温度场的有限元仿真研究,得到HFCVD系统衬底温度场的三维分布规律,并讨论热丝直径、热丝温度、热丝根数、热丝-衬底距离和水冷散热系数等对衬底温度大小及均匀性的影响。仿真结果表明,在适宜金刚石膜生长的参数范围内,热丝参数和衬底接触热阻对衬底温度大小有显著影响,由于衬底内部的三维热传导使得衬底温度场更加均匀,各参数对衬底温度场的均匀性影响不大。研究结果为高质量制备金刚石膜提供理论基础。

太阳模拟器中光谱修正滤光片的研制

在太阳模拟器中,鉴于氙灯的优点及其光谱能量分布与太阳光谱的相近性,通常使用氙灯模拟太阳光谱,但由于氙灯光谱与太阳光谱分布存在差异,所以研制一种滤光片进行氙灯光谱分布的修正。考虑到滤光片工作在强光辐照条件下,所以选用的薄膜材料必须具有低的吸收和高的抗能量阈值。采用电子束和离子辅助沉积技术进行膜层的制备,选择合理的沉积方式并通过优化工艺参数使膜层表面光滑、牢固且通过抗能量测试,最终研制出的光谱修正滤光片满足使用要求。

规整膜系层厚允许误差的研究

提出了一种通过计算机模拟薄膜的淀积过程来计算规整膜系层厚允许误差的方法 ,所计算的层厚允许误差不仅取决于膜系的设计结构 ,还与薄膜的淀积工艺、镀膜设备的监控精度有关 实验结果表明

微波等离子化学气相沉积金刚石膜新型微波谐振腔设计

提出新型微波谐振腔用于化学气相沉积金刚石薄膜,腔体有效体积可以调节,采用环形介质窗口,置于沉积基台的下方,允许产生较大并且温度较高的等离子体。同轴内导体与沉积台相连接,微波从谐振腔底端传输经同轴导体耦合进入腔体。采用有限元的方法优化谐振腔的尺寸,使其能耦合进更大的微波能量,优化后,最大电场区域位于沉积台上方,并且均匀分布,在腔体内其它区域和介质窗口附近电场强度则很小,满足设计要求。采用时域有限差分法模拟了谐振腔在一定微波输入功率下产生等离子体的特性,并对设计的谐振腔进行试验研究,实验观察到的等离子体位置与模拟结果一致。

液滴喷射技术在全聚合物薄膜晶体管制备中的应用

研究液滴喷射技术在全聚合物薄膜晶体管制备中的应用,并着重分析电极材料在预成型基底表面的沉积扩散情况。通过数值模拟,分析隔断材料、液滴与隔断间距、液滴碰撞速度3个因素对沉积的影响。结果发现,只有当这3个要素配置合理时,才能保证液滴的正常沉积,从而保证晶体管的质量。例如,当隔断材料采用聚酰亚胺,沟道宽度为5μm,液滴与隔断间距为30μm,液滴碰撞速度为4m/s时,液滴能够正常沉积,晶体管的质量得到保证。本文结果可为TFTs的制作提供一定的参考。