纳米材料和纳米结构第七讲-new-2-PVD.ppt

1、第七讲第七讲第七讲第七讲Physical Vapor Deposition物理气相沉积物理气相沉积纳米材料和纳米结构纳米材料和纳米结构纳米材料和纳米结构纳米材料和纳米结构Physical Vapor Deposition(PVD)wDefinition Deposition of films by condensation from vapor phase is commonly called physical vapor deposition(PVD).wThree Steps of PVDGenerating a vapor phase by evaporation or sublimat

2、ionwElectron-beam evaporation（电子束蒸发）（电子束蒸发）wMolecular-beam epitaxy（分子束外延（分子束外延,MBE）wThermal evaporation（热蒸发）（热蒸发）wSputtering（溅射）（溅射）wCathodic arc plasma deposition（阴极电弧等离子体沉积）（阴极电弧等离子体沉积）wPulsed laser deposition（脉冲激光沉积）（脉冲激光沉积）Transporting the material from the source to the substrateFormation of fi

3、lm by nucleation and diffusionwApplicationIn coatings of electronic materialswInsulatorwSemiconductorwConductorwSuperconductorNanometer scale multilayer structureswAdvanced electronic deviceswAbrasion resistant（抗磨）抗磨）coatingswConcerned Problems and ChallengesContamination at the interfaces or interm

4、ixingMulti-material systems involvedCost of equipment and maintenance Complexion of operationwSystems Described in This SectionSputteringPulsed laser deposition1 Sputtering（溅射）（溅射）1-1 Principle of Sputtering1-2 Sputtering System1-3 Preparing Multilayer Structures by Sputtering1-4 Current Status of S

5、puttering1-1 Principle of SputteringwEjection（喷射）（喷射）of Atoms from the TargetAccomplished by an energetic particle bombarding a target surface with sufficient energy(50 eV 1 000 eV)wTargetCathodeConnected to a negative voltage supplyComposed of the materials to be depositedwSubstrateAnode May be gro

6、unded,floated,or biasedwGlow Discharge Medium in Sputtering ChamberA gas or a mixture of different gases,most commonly Ar or HeIn reactive sputtering:introduce reactive gases such as O2 or N2 Pressure:a few mTorr to several hundreds mTorrwProcedureGeneration of positive ions:ionizing the sputtering

7、gas by glow dischargeBombarding:accelerated positive ions strike the target surface and remove mainly neutral atomsCondensation:neutral atoms leave the target and condense on the substrate surface,and form into thin films wAn Important Concept:Sputtering YieldA measurement of the efficiency of sputt

8、eringRatio of the number of emitted particles to the number of bombarding ones 1-2 Sputtering SystemwTypical Types of Sputtering SystemsDirect current(dc)diode sputteringwUsed for sputtering conducting materialsRadio frequency(rf)diode sputteringwUsed for sputtering insulating materialsMagnetron dio

9、de sputtering wMost commonly used todaywPlasma be confined around the target surface by a magnet fieldwAdvantages of using magnetron sputteringlFeasibility of large cathode sizelHigh sputtering yieldlLess bombardment to the substrate用用于于制制备备TiN/VN 多多层层膜膜的的磁磁控控溅溅射射系系统统氩气氩气流量表流量表流量控制阀流量控制阀压力传感器压力传感器低温

10、泵低温泵低温泵低温泵靶靶1靶靶2旋转衬底支架旋转衬底支架衬底衬底流量表流量表阀门阀门流量表流量表流量控制阀流量控制阀1流量控制阀流量控制阀2主流量控制阀主流量控制阀质谱仪质谱仪阀门阀门锁定装置锁定装置wWays to reduce the damage and resputtering of growing filmDamage caused by negative ion effect and radiation enhanced diffusionImprovement methodwUse high gas pressure:to reduce the energy of the neg

11、ative ionswUse off-axis sputtering:to avoid the substrate directly facing the cathode wDisadvantage of off-axis sputtering:llow deposition ratelsmall deposition areawDeposition of magnetic materials:facing target sputtering systems偏轴溅射系统偏轴溅射系统示意图示意图Schematic of off-axis sputtering system可可360度旋转的衬底支

12、架度旋转的衬底支架陶瓷加热器陶瓷加热器负离子撞击区负离子撞击区衬底衬底靶靶溅射枪溅射枪溅射源溅射源屏蔽闸屏蔽闸空间屏蔽区空间屏蔽区正面溅射正面溅射系统系统示意图示意图Schematic of the facing target sputtering system衬底衬底靶靶磁体磁体冷却水冷却水氩气氩气1-3 Preparing Multilayer Structures by SputteringwTypes and Properties of Multilayer StructuresTypes of architectureswMetal/metalwCeramic/ceramicwMet

13、al/ceramicwSemiconductor/semiconductorPropertieswWith structurally modulated architectureswWith compositionally modulated architectureswHigh interface volume fractionwLarge intrinsic stresswWith structural and/or compositional gradientwExhibiting unique and enhanced electric,dielectric,magnetic,and

14、mechanic propertieswBaTiO3 Nanolayer Ferroelectric Thin Film CapacitorsAdvantage:higher relative dielectric constantDisadvantage:high leakage currentElectrical properties strongly depending upon the processing condition,microcrystal structure,and choice of bottom electrodewAmorphous:low dielectric c

15、onstant(16 at 105 V/cm),low leakage currentwPolycrystalline:high dielectric constant(400 at 105 V/cm),high leakage currentAim of nanolayer structure BaTiO3 film capacitor:high dielectric constant and low leakage currentRealization and effectsuSubstrate:Ru/SiO2/SiuTechnique:rf magnetron sputtering,sp

16、uttering interruption(中中断断）between layers to change the substrate temperatures(680C,60 C)uLayer structure:n-cycle alternate layers of amorphous and polycrystalline BaTiO3(microcrystalline be obtained by annealing amorphous layer)uResults obtainedlLeakage current density be considerably reduced,and the effect becoming better with increasing cycle numberlDielectric constant be two or three times higher than single amorphous layer but lower than a single polycrystalline layer具有纳米多层结构的具有纳米多层结构的BaTiO