纳米材料和纳米结构P hysical V apor D eposition物理气相沉积第七讲Physical Vapor Deposition (PVD)物理气相沉积一、Definition定义Film deposition by condensation(凝结) from vapor phase(气相)从气相凝结的薄膜沉积二、Three Steps of PVD：(PVD的三个步骤：)1、Generating a vapor phase by evaporation or sublimation(用蒸发或升华生成一个气相)1、Electron-beam evaporation(电子束蒸发)2、Molecular-beam epitaxy(分子束外延)3、Thermal evaporation(热蒸发)4、Sputtering (溅射)5、Cathodic arc plasma deposition(阴极电弧等离子沉积)6、Pulsed laser deposition(脉冲激光沉积)2、Transporting the material from the source to the substrate(把原材料导入基底；)3、Formation of film by nucleation and diffusion(集结和扩散作用形成薄膜；)三、Application(应用)1、Coatings of electronic materials(电子材料的镀膜)Insulator绝缘体Semiconductor半导体Conductor导体Superconductor(超导体)2、Nanometer scale multilayer structures（纳米尺寸的层结构）Advanced electronic devices先进电子设备Abrasion resistant coatings耐磨涂料四、Concerned Problems(关注问题)*Contamination at the interfaces or intermixing(在物质界面和混合下的污染情况) * Multi-material systems involved(相关的复合材质系统；)* Cost of equipment and maintenance(器材和维护费用)* Complexion of operation(运算情况)五、Systems Described in This Section(此节中描述的系统)Sputtering(溅射法)Pulsed laser deposition(脉冲激光沉积法)1 Sputtering（溅射）1-1 Principle of Sputtering(溅射原理)1-2 Sputtering System(溅射系统)1-3 Preparing Multilayer Structures by Sputtering(溅射法备制多分子层结构) 1-4 Current Status of Sputtering(溅射法的近况)1-11-1 Principle of Sputtering(溅射原理)1、Ejection of Atoms from the Target（靶物质原子的喷溅）* Accomplished by an energetic particle bombarding a target surface with sufficient energy (50 eV – 1 000 eV)（在足够电压下（大概50---1000eV）,高能量粒子撞击靶物质表面来完成喷溅。

）2、Target（靶物质）* Cathode, connected to a negative voltage supply（阴极连接到电压负极；）* Composed of the materials to be deposited（堆积组成的材料）3、Substrate（基底材料）* Anode（阳极）* May be grounded, floated, or biased（可能是接地、漂浮或偏移）4、Glow Discharge Medium in Sputtering Chamber（溅射室的散热介质）* A gas or a mixture of different gases, most commonly Ar or He （气体或不同气体的混合物，一般是Ar或He气）*Reactive sputtering: introduce reactive gases such as O2 or N2 （反应溅射：介绍反应气体如O2或N2）*Pressure: a few mTorr to several hundreds mTorr（压强：大概几个毫托到几百个毫托：注：1 torr≈133.322 Pa=1.333mbar（毫巴）=0.001315789473atm）5、Procedure（步骤）*Generation of positive ions: ionizing the sputtering gas by glowDischarge（正离子的产生：辉光放电电离溅射气体）*Bombarding: accelerated positive ions strike the target surface and remove mainly neutral atoms（碰撞：加速后的正离子撞击靶物质表面并带走大量中性原子）*Condensation: neutral atoms leave the target and condense on thesubstrate surface, and form into thin films（凝结：中性原子离开靶物质并在基底材料表面形成薄膜）6、An Important Concept: Sputtering Yield（重要概念：溅射效率）*A measurement of the efficiency of sputtering（溅射效率的测量）*Ratio of the number of emitted particles to the number ofbombarding ones(发散的粒子数与碰撞粒子数的比例)1-2 Sputtering System(溅射系统)1、Typical Types of Sputtering Systems(建设系统的典型类型)* Direct current (dc) diode sputtering（直流电<dc>二极管溅射）Used for sputtering conducting materials（用于溅射导体材料）* Radio frequency (rf) diode sputtering（频射<rf>二极管溅射）Used for sputtering insulating materials（用于溅射绝缘体材料）* Magnetron diode sputtering（二极管磁控溅射）& Most commonly used today（现在最常用的方法）& Plasma being confined around the target surface by a magnet field （等离子体被磁场限制在靶物质周围）& Advantages of using magnetron sputtering（二极管磁控溅射的优势）$ Feasibility of large cathode size（大尺寸阴极的可行性）$ High sputtering yield（溅射效率高）$ Less bombardment to the substrate（对基质更少的撞击）氩气锁定装置流量控制阀1 用于流量表流量控制阀低温泵流量表阀门流量表流量控制阀2主流量控制阀阀门制备TiN/VN多层膜的压力传感器衬底质谱仪磁控溅射低温泵靶1旋转衬底支架靶2 系统2、Ways to reduce the damage and resputtering of growing film(减少对薄膜生长的损害和二次溅射的方法)* Damage caused by negative ion effect and radiation enhanced diffusion （负离子效应和辐射带来的损害回增强扩散）* Improvement method（改进方法）$ Use high gas pressure: to reduce the energy of the negative ions （利用高气压：用以减少负离子的能量）$ Use off-axis sputtering: to avoid the substrate directly facing theCathode（利用偏轴溅射：为了避免基质直接接触阴极）$ Disadvantage of off-axis sputtering:（偏轴溅射的缺点）# Low deposition rate（沉积率低）# Small deposition area（沉积范围窄）3、Deposition of magnetic materials: facing target sputtering systems（磁性材料的沉积：正面溅射系统）溅射枪溅射源可360度旋转的衬底支架偏轴溅射系统陶瓷加热器负离子撞击区屏蔽闸衬底靶空间屏蔽区示意图Schematic of off-axis sputteringsystem磁体靶衬底正面溅射系统示意图Schematic氩气of thefacingtargetsputteringsystem冷却水1-3 Preparing Multilayer Structures by Sputtering（溅射法制备多分子层结构）1、Types and Properties of Multilayer Structures（多层结构的类型和属性）* Types of architectures（体系结构的类型）$Metal/metal（金属和金属）$ Ceramic/ceramic（陶瓷和陶瓷）$ Metal/ceramic（金属和陶瓷）$ Semiconductor/semiconductor（半导体和半导体）* Structural and physical properties（结构和物理性能）$ Structurally modulated architectures（结构性调整体系结构）$ Compositionally modulated architectures$ High interface volume fraction（高界面体积分数）$ Large intrinsic stress（大的内在压力）$ Structural and/or compositional gradient（结构和组合的梯度）$ Unique and enhanced electric, dielectric, magnetic, and mechanicproperties（独特和加强的导电、绝缘、磁性和机械性能）2、BaTiO3 Nanolayer Ferroelectric Thin Film Capacitors(具有纳米多层结构的铁电性BaTiO3薄膜电容器)* Advantage: high relative dielectric constant（优势：较高的相对介电常数）* Disadvantage: high leakage current（劣势：电流泄露高）* Electrical properties strongly depending upon the processingcondition, microcrystal structure, and choice of bottom electrode（电气性能强烈取决于加工工艺条件、微晶结构和电极的选择）$ Amorphous: low dielectric constant (16 at 105 V/cm), low leakageCurrent（非晶的：地介电常数<在105V/cm下为16>，低电流泄露）$ Polycrystalline: high dielectric constant (400 at 105 V/cm), highleakage current（多晶的：高介电常数<在105V/cm为400>，高电流泄露）* Nanolayer structure BaTiO3 film capacitor: high dielectric constantand low leakage current（纳米多层结构的BaTiO3薄膜电容器：高介电常数和低电流泄露）* Realization and effects（实践和影响）$ Substrate: Ru/SiO2/Si（基质：Ru/SiO2/Si）$ Technique: rf magnetron sputtering, sputtering interruption between layers to change the substrate temperatures (680 ︒C, 60 ︒C)（技术：射频磁控溅射，层间溅射中断以改变衬底温度<680度，60度>）$ Layer structure: n-cycle alternate layers of amorphous and polycrystalline BaTiO3 (microcrystalline be obtained by annealing amorphous layer)（层状结构：n重交换层的无定形和非晶态的BaTiO3结构<退火处理无定形层结构得到微晶>.）$ Results obtained（所得结果）# Leakage current density be considerably reduced, and the effect becoming better with increasing cycle number（电流泄露密度大大减小，而且，增加循环数优化了作用效果）# Dielectric constant be two or three times higher than single amorphous layer but lower than a single polycrystalline layer（介电常数比单一非晶层高了2或3倍，但是比单一多晶层低）Polycrystalline（多晶的，多晶质）；amorphous（非晶质）；electrode（电极；电焊条）；microcrystalline（微晶的. 微晶）；具有纳米多层结构的BaTiO3薄膜电容器横截面示意图3、Nanolayer MoSi2/SiC(MoSi2/SiC纳米层)* Substrate: single crystal silicon (sc-Si)（衬底：单晶硅< sc-Si >）* Techniques:（技术）$ Magnetron sputtering for deposition of MoSi2（磁控溅射的MoSi2沉积物）$ rf sputtering for deposition of SiC（射频溅射的SiC沉积物）$ MoSi2/SiC layered composites be prepared by cyclically passing thesamples beneath the two targets with a speed (thickness of 10 nm/3 nm)（在两个靶物质下一同样速度周期性通过样品生成MoSi2/SiC分层复合材料）* Heat treatment or annealing: inducing recrystallization in theMoSi2/SiC multilayered film（热处理或退火处理：包括在MoSi2/SiC多层膜的再结晶）* Properties after annealing:（退火后的性能）$ Superior oxidation resistance（优越的抗氧化性能）$ Significant hardness（显著的硬度）MoSi2/SiC多层膜的剖面透射电镜图片Cross-sectional TEM image of MoSi2/SiC multilayered filmMoSi2/SiC多层膜退火前的电子衍射花样Electron Diffraction Pattern of MoSi2/SiC multilayered film before annealing经过800°C，1h退火处理的MoSi2/SiC多层膜的低放大倍数亮场电镜照片4、Nanolayer Cu/Nb（Cu/Nb纳米层）* Substrate: (100) sc-Si（基质(100) sc-Si）* Techniques: dc magnetron sputtering（技术：直流磁控溅射法）* Layer thickness: (100 nm/100nm)（层厚度：100 nm/100nm）* Properties(性能)$ High strength（高强度）$ Superior thermal conductivity（优越的导热系数）$ Superior electrical conductivity（优越的导电性）通过磁控溅射技术沉积的Cu/Nb多层膜的剖面透射电镜图像Cu/Nb多层膜的电子衍射花样Electron diffraction pattern of Cu/Nb multilayer（Cu/Nb多分子层的电子衍射图）1-4 Current Status of Sputtering（溅射）AdvantagesMost widely used sputtering method（最广泛应用的溅射方法）Well-established coating techniques for microelectronic applications（固定的微电子应用的涂层工艺）Many nanometer multilayer structures be prepared by sputtering（很多毫微米级的多层结构通过溅射制备）ShortcomingsMaterials system limitation: mainly conductors or nitrides（材料体系的局限性：主要是导体或者氮化物）Difficulty in control stoichiometry, low deposition rate etc.（在控制化学计量方面的困境，沉积速率低等）Be questionable to be used as the main coating tool in microelectronicsindustry (although successful for SrTiO3, BaTiO3, and Ba1-x Sr x O3)（被用作微电子产业的主要涂层工具仍然存在问题（尽管对于SrTiO3, BaTiO3, and Ba1-xSrxO3是成功的）2 P ulsed L aser D eposition (PLD，脉冲激光沉积)2-1 Principles of PLD（PLD的原理）2-2 Deposition of Nanoscale Metal Oxide Thin Films（纳米级金属氧化物薄膜的沉积）2-3 Multilayer Structures Prepared by PLD（用PLD制备多层结构）2-4 Current Status of PLD（PLD的现状）2-1 Principles of PLDAdvantages and Properties of PLD（PLD的优点和性能）Simplest deposition technique among all thin film growth techniques（在所有的薄膜生长技术中最简单的沉淀技术）Stoichiometric removal of constituent species from target（靶材种类组成的化学计量迁移）Versatile deposition of a wide variety of materials（各种各样的材料的多样沉积）Metals（金属）Semiconductors（半导体）Nitrides（氮化物）Dielectric materials（介电材料）Oxides（氧化物）Organic compounds/ploymers（有机合成物）Ternary compounds（三元化合物）Technical Description of PLD（PLD技术说明）Based on physical vapor deposition（以物理气相沉积为基础）Impact of high-power short pulsed laser radiation on solid targets（高功率、短脉冲激光辐射对固体靶材的影响）Removal of materials from impact zone（材料从冲击区的迁移）Equipment constituent（设备结构）High power laser: external energy source to vaporize target（高能激光：使靶材蒸发的外部能量源）materials（材料）Vacuum chamber with a quartz window（有石英窗口的真空室）Target holder or multiple target holder（靶材支撑物或者多靶材支撑物）Substrate holder (with a heater)（带加热器的衬底架）Integration with other type of evaporation sources（其他类型蒸发源的集成）激光束脉冲激光沉积系统（示意图）Schematic diagram of a PLD system 加热器衬底喷流靶2-2 Deposition of Nanoscale Metal Oxide Thin Films（纳米级金属氧化物薄膜的沉积物）Importance（重要性）Metal oxides could exhibit versatile properties（金属氧化物能显示多种性能）High temperature superconductivity（高温超导性）Ferroelectricity（铁电性）Colossal magnetoresistivity (CMR)（很大的磁致电阻率）Non-linear optical properties（非线性光学性质）Metal oxides be recognized as possible candidates for next generationelectronic materials due to their diverse properties（由于性能多样，金属氧化物被认为是下一代电子材料可能的候选）Substrates for Metal Oxide Films（金属氧化物薄膜的基底）Importance: proper choice of substrate be essential for accomplishingperfect 2-dimensional epitaxy of metal oxide heterostructures（重要性：选择合适的基底对完美的完成金属氧化物异质结构的二维外延时必不可少的）Requirements for a good substrat（对好基底的要求）Good in plane lattice match（平面晶格匹配很好）Thermal expansion coefficient close to that of film（热胀系数与薄膜相近）Atomically smooth surface（原子级光滑的表面）Good chemical compatibility with the film（与薄膜能有很好的化学兼容）Commonly used single crystal substrates（常用的单晶基底）Yttria-stabilized zirconia (YSZ)（氧化钇稳定的氧化锆/钇稳定氧化锆）MgO（氧化镁）LaAlO3（铝酸镧）SrTiO3（钛酸锶）NdGaO3（镓酸钕（音：女））(LaAlO3)0.3– (Sr2AlTaO6)0.7（拉萨特LSAT）Sapphire（蓝宝石）Surface treatment of substrates（基底表面处理）Ion milling + in situ annealing（离子研磨+原位退火）Ion milling + pre-deposition（离子研磨+预先沉积/前扩散）Chemical etching + annealing（化学腐蚀+退火）Surface terminating（表面终止）Initial Growth of Metal Oxide Films（金属氧化物薄膜的早期生长）Observation and monitor techniques（观察和监控技术）In situ: reflected high energy electron diffraction (RHEED), laserlight scattering, real-time optical diagnosis（原位：反射的高能电子衍射，激光散射，实时光学诊断）Ex situ: scanning tunneling microscope (STM), atomic forcemicroscopy (AFM), cross-sectional transmission electron microscopy(TEM), X-ray diffraction（非原位：扫描隧道显微镜，原子力显微镜，横向透射电子显微镜，X射线衍射）Growth Mode（生长模式）-Highly depending upon the quality of substrate（高度取决于基底的质量）-Stranski-Krastanov mode (layer plus island growth) to Volmer-Webermode (island growth) [at a critical thickness] { Stranski-Krastanov 模式（层加岛状生长）到三维模式（岛状生长）[在一个临界厚度]}Layer plus island growth Island growth(Thickness < Critical Thickness) (Thickness > Critical Thickness)YBCO薄膜的早期生长模式及其转变Characterizing multilayer thickness by X-ray diffraction（通过X射线衍射描述多层厚度）YBCO/PrBCO superlattice: a new man-made periodicity（YBCO/PrBCO超点阵：一种新的人造周期性）The modulation thickness in superlattices is measured by the positionof satellites peaks, （超点阵上的调制厚度是通过卫星峰的位置测定的）given by：D = (⎣/2) /(sin⎝n+1 - sin⎝n)D is the modulation thickness with D = d YBCO +d PrBCO;（D是调制厚度）⎣ is the wavelength of X-ray source;（L是X射线源的波长）⎝n+1 and ⎝n are positions of the nth and the (n+1)th satellite peaks（⎝n+1和 ⎝n是第n和n+1个卫星峰的位置）The satellite peaks up to the fourth order indicate atomically sharpand flat interfaces（直到第四个卫星峰的顺序表明了原子级尺寸和平接口）Nominal Thickness2.4 nm/12 nmCalculated Thickness14.6 nmX-rayθ-2θscan around (001) and (002) peaks of a YBCO/PrBCO superlatticeCharacterizing film thickness by low-angle X-ray diffractionCharactering film thickness by STM, AFM, SEM, and TEMA low-angle X-ray reflection of a nominally 27.6 nm thick YBCO on NdGaO32-3 Examples of Multilayer Structures Prepared by PLD (PLD制备多层结构举例)Superconductivity in a Unit-cell Thick YBCO（一个单胞厚度YBCO的超导电性）Aimed Questions:What is the minimum unit needed for the occurrence ofsuperconductivity?（出现超导电性所需的最小单元是什么？）How essential is the interlayer coupling between Cu-O planes indetermining the transition temperature?（Cu-O平面层间耦合在决定转变温度方面的重要性）Way to the question: using superlattice structures as model system(possible coupling or other parameters can be changed artificially byinterposing other materials in between the Cu-O planes or unit-cells)【Way to the question:用超点阵结构作为模拟体系（可能的耦合或者其他参数能够通过在Cu-O平面或者单胞之间插入其他材料而人为改变）】System Composing:（系统构成）Ultrathin YBCO layers + PrBCO layers (nonsuperconducting)Resistive transition of 1, 2 and 4 unit-cell thick YBCO layers sandwiched between (Y1-x Pr x)Ba2Cu3O7 adjacent layers with x = 1 and 0.6Dependence of transition temperature on the x value of(Y1-x Pr x)Ba2Cu3O7 adjancentThe dependence of critical current density on the magnetic field for1 unit-cell (1.2 nm) and 200 nm thick YBa2Cu3O7 filmsC. Kwon et al., Appl. Phys. Lett. 62 (2004) 1289Superlattice SrTiO3/BaTiO3（SrTiO3/BaTiO3超晶格结构）SrTiO3/BaTiO3 can form solid solution with each other at allcompositions due to their similar structures and the comparable ionic radii of Ba2+ and Sr2+（SrTiO3/BaTiO3能够以任意比例形成固溶体，这是由于他们具有相似的结构，并且Ba2+和Sr2+的离子半径相近）Strained（紧张的；勉强的）SrTiO3/BaTiO3 superlatticeElectric/dielectric behaviour（带电行为和介电行为）Introducing lattice stress at the interface（在表面引进晶格应力）Enhanced dielectric constant（提高介电常数）H. Tabata et al., Appl. Phys. Lett. 65 (2005) 19702-4 Current Status of Pulsed Laser Deposition（PLD目前的地位）Major AdvantagesCongruent evaporation（全等蒸发）Crystallinity（结晶度）Fast response time（快速反应时间）Especially suited for synthesizing high qualified metal oxide thin films（对合成高质量金属氧化物薄膜非常合适）Major technological obstaclesParticulate emission（粒子排放）Large area coating（大面积镀膜）Hard to control down to the atomic scale（当小到原子级别时难以控制）Further optimizing of PLD processing condition and depositiontechniques are needed（仍然需要近一步优化PLG加工条件和沉积）Thank you for your attention。