Vacuum Deposition onto Webs, Films and Foils

 
 
William Andrew (Verlag)
  • 3. Auflage
  • |
  • erschienen am 15. August 2015
  • |
  • 602 Seiten
 
E-Book | ePUB mit Adobe DRM | Systemvoraussetzungen
E-Book | PDF mit Adobe DRM | Systemvoraussetzungen
978-0-323-29690-8 (ISBN)
 

Vacuum Deposition onto Webs: Films and Foils, Third Edition, provides the latest information on vacuum deposition, the technology that applies an even coating to a flexible material that can be held on a roll, thereby offering a much faster and cheaper method of bulk coating than deposition onto single pieces or non-flexible surfaces such as glass.

This technology has been used in industrial-scale applications for some time, including a wide range of metalized packaging. Its potential as a high-speed, scalable process has seen an increasing range of new products emerging that employ this cost-effective technology, including solar energy products that are moving from rigid panels onto cheaper and more versatile flexible substrates, flexible electronic circuit 'boards', and flexible displays.

In this third edition, all chapters are thoroughly revised with a significant amount of new information added, including newly developed barrier measurement techniques, improved in-vacuum monitoring technologies, and the latest developments in Atomic Layer Deposition (ALD).


  • Provides the know-how to maximize productivity of vacuum coating systems
  • Thoroughly revised with a significant amount of new information added, including newly developed barrier measurement techniques, improved in-vacuum monitoring technologies, and the latest on Atomic Layer Deposition (ALD)
  • Presents the latest information on vacuum deposition, the technology that applies an even coating to a flexible material that can be held on a roll, thereby offering a much faster and cheaper method of bulk coating
  • Enables engineers to specify systems more effectively and enhances dialogue between non-specialists and suppliers/engineers
  • Empowers those in rapidly expanding fields such as solar energy, display panels, and flexible electronics to unlock the potential of vacuum coating to transform their processes and products


Charles started his working life as an apprentice in mechanical engineering finishing as a toolmaker. He has a degree in Materials Engineering and Masters and Doctorate Degrees by research in vacuum deposition onto polymer webs. He now has accumulated over 35 years experience in vacuum deposition onto webs with the last 15 spent running his own consultancy business. He has published over 85 technical articles and papers, has 5 patents & has run training courses in Asia, Europe and USA. He has written two books 'A guide to roll-to-roll vacuum deposition of barrier coatings' and 'Vacuum Deposition onto Webs, Films & Foils', now into the 2nd edition and contributed chapters on transparent conducting coatings and packaging coatings in two other books. Charles is a Blog editor on behalf of AIMCAL and has a regular column in Converting Quarterly.
  • Englisch
  • USA
Elsevier Science
  • 41,61 MB
978-0-323-29690-8 (9780323296908)
0323296904 (0323296904)
weitere Ausgaben werden ermittelt
  • Front Cover
  • Vacuum Deposition onto Webs, Films and Foils
  • Copyright Page
  • Contents
  • Introduction
  • Section 1
  • 1 What Is a Vacuum?
  • 1.1 Introduction
  • 1.2 What Is a Gas?
  • 1.3 Pressure
  • 1.4 Partial Pressure
  • 1.5 Vapor Pressure
  • 1.6 Saturated Vapor Pressure
  • 1.7 Why Do We Need a Vacuum?
  • 1.8 Mean Free Path (mfp)
  • Further Reading
  • 2 Products Using Vacuum Deposited Coatings
  • 2.1 Introduction
  • 2.2 Metalized Packaging Film
  • 2.2.1 Other Metalized Products
  • 2.3 Capacitor Films
  • 2.3.1 Supercapacitors
  • 2.4 Optical Data Storage (ODS) Tapes
  • 2.5 Holographic Coatings
  • 2.5.1 Bright Metallic Holograms
  • 2.5.2 Semitransparent Holograms
  • 2.5.3 De-Metalized Holograms
  • 2.5.4 Transparent High-Refractive Index Holograms
  • 2.6 Flake Pigments
  • 2.7 Barrier Coatings
  • 2.7.1 Transparent Barrier Coatings
  • 2.8 Transparent Conducting Oxides (TCOs)
  • 2.8.1 Gas Sensors
  • 2.9 Energy Conservation Windows
  • 2.9.1 Solar Gain
  • 2.9.2 Solar Rejection
  • 2.10 Solar Cells
  • 2.11 Solar Absorbers
  • 2.12 Flexible Circuits
  • 2.13 Optical Variable Devices (OVDs)
  • 2.14 Magnetic Electronic Article Surveillance (EAS) Tags
  • 2.15 Pyrotechnics
  • 2.16 Thin-Film Batteries
  • 2.17 Flexible Piezoelectric Films
  • 2.18 Coated Metal Substrates
  • 2.19 Medical Applications
  • 2.20 Carbon Nanotubes and Graphene Films
  • References
  • 3 Pressure Measurement
  • 3.1 Introduction
  • 3.2 Bourdon Gauge
  • 3.3 Pirani and Thermocouple Gauges
  • 3.4 Capacitance Manometer
  • 3.5 Penning or Cold Cathode Ionization Gauge
  • 3.6 Ion or Hot-Cathode Ionization Gauge
  • Further Reading
  • 4 Pumping
  • 4.1 Introduction
  • 4.2 Rotary or Roughing Pumps
  • 4.2.1 Piston Pumps
  • 4.2.2 Dry Pumps
  • 4.3 Roots Pumps or Blowers
  • 4.4 Diffusion Pumps
  • 4.5 Turbomolecular Pumps
  • 4.6 Getter or Sputter Ion Pump
  • 4.7 Cryopumps
  • 4.8 Cryopanels
  • 4.9 Pumping Strategy
  • 4.10 System Pumping
  • 4.11 Filtering
  • 4.12 Conclusions
  • References
  • Further Reading
  • 5 Process Diagnostics and Coating Characteristics
  • 5.1 Introduction
  • 5.2 Reflectance (R), Transmittance (T), and Absorbtance (A) Measurements
  • 5.3 Optical Density
  • 5.4 Conductivity/Resistivity
  • 5.4.1 Sheet Resistance and Calculating Resistivity or Thickness
  • 5.5 Online Resistance Monitoring
  • 5.6 Transparent Conducting Coatings
  • 5.7 Residual Gas Analyzers (RGA)
  • 5.8 Plasma Emission Monitors (PEM)
  • 5.9 Thickness
  • 5.9.1 Stylus Techniques
  • 5.9.2 Ellipsometry
  • 5.9.3 Weight Loss Measurement
  • 5.9.4 Electron Microscopy
  • 5.9.5 Quartz Crystal Monitor
  • 5.10 Barrier
  • 5.11 Pinholes
  • 5.12 Artificial Intelligence and Neural Network Control Systems
  • 5.13 Chemometrics
  • 5.14 Surface Energy Measurements
  • 5.15 Emissivity
  • 5.16 Lambda Probe/Sensor/Gauge
  • 5.17 X-Ray Fluorescence Sensor
  • 5.18 Atomic Absorption Spectroscopy
  • References
  • 6 Leaks, Water Vapor, and Leak Testing
  • 6.1 Introduction
  • 6.2 Real Leaks
  • 6.3 Imaginary Leaks
  • 6.4 Outgassing and Water Vapor
  • 6.4.1 Outgassing from Film
  • 6.5 Leak Detection
  • 6.5.1 Leak Testing Using Helium
  • References
  • 7 Mass Spectrometers, Helium Leak Detectors, and Residual Gas Analyzers
  • 7.1 Introduction
  • 7.2 Mass Spectrometers
  • 7.3 Residual Gas Analyzers
  • References
  • Section 2
  • 8 Substrates - Surface Quality, Cleaning - Adhesion, and Adhesion Testing
  • 8.1 Introduction
  • 8.2 Polymer Substrates
  • 8.2.1 Polymer Roll Quality
  • 8.2.2 Polymer Surface Quality
  • 8.2.3 Oligomers
  • 8.2.4 Additives
  • 8.2.5 Slip Agents
  • 8.2.6 Anti-Block Additives
  • 8.2.6.1 Slip Effect
  • 8.2.6.2 Blocking
  • 8.2.6.3 Anti-Blocking Additives
  • 8.2.6.4 Coefficient of Friction (CoF)
  • 8.3 Polymer Substrate Cleaning
  • 8.4 Polymer Surface Etching
  • 8.5 Higher Specification Polymer Substrates
  • 8.5.1 Metal Web and Surface Quality
  • 8.5.2 Metal Surface Contamination and Cleaning
  • 8.6 Paper
  • 8.7 Foams, Nonwovens, and Textiles
  • 8.8 Flexible Glass
  • 8.9 Cores
  • 8.9.1 Source of Problems
  • 8.10 Packaging
  • 8.11 Cost Benefit
  • References
  • 9 Adhesion and Adhesion Tests
  • 9.1 Introduction
  • 9.2 Adhesion Testing
  • 9.2.1 The "Sellotape" Test
  • 9.2.2 Adhesion Tests
  • 9.2.3 Adhesion and Surface Analysis
  • References
  • 10 Surface Treatment of Webs and Foils
  • 10.1 Introduction
  • 10.2 Cleaning and Sealing
  • 10.2.1 Debris Removal
  • 10.2.2 Polymer Webs
  • 10.2.3 Metal Foils
  • 10.3 Atmospheric Treatments
  • 10.4 Plasma Treatments
  • 10.4.1 Plasma Cleaning
  • 10.4.1.1 Oxidizing Gases
  • 10.4.1.2 Reducing Gases
  • 10.4.1.3 Noble Gases
  • 10.4.1.4 VUV and Ozone Cleaning
  • 10.5 System Design Considerations
  • 10.5.1 Plasma Types
  • 10.5.2 Back Surface Plasma Treatment
  • References
  • 11 Polymer Coating Basic Information
  • 11.1 Introduction
  • 11.2 Polymer Coating Processes
  • 11.2.1 Leveling
  • 11.2.2 Coating Options
  • 11.2.3 Evaporation
  • 11.2.4 In-Vacuum Printing
  • 11.2.4.1 Comment
  • 11.3 Radiation Cured Polymers - Acrylates
  • 11.3.1 Electron Beam Curing
  • 11.3.2 UV Radiation Curing
  • 11.3.3 UV Sources
  • 11.3.4 Chemistry
  • 11.3.4.1 Prepolymers
  • 11.3.4.2 Reactive Diluents
  • Cure Rules of Thumb
  • 11.3.4.3 Additives
  • 11.3.4.4 Photoinitiators
  • 11.3.4.5 Health and Safety Issues
  • 11.3.4.6 Formulation
  • 11.4 Comments
  • References
  • 12 Nucleation, Coalescence, and Film Growth
  • 12.1 Introduction
  • 12.2 Thin Film - Thick Film
  • 12.3 Nucleation
  • 12.4 Coalescence
  • 12.5 Network and Percolation Threshold
  • 12.6 Holes
  • 12.7 Film Growth
  • 12.8 Energy
  • 12.9 Angular Deposition
  • 12.10 Electrical and Optical Performance
  • 12.11 Nodule Formation
  • 12.12 Crystal Structure
  • 12.13 Deposition Rules of Thumb
  • References
  • 13 Pattern Metallization
  • 13.1 Introduction
  • 13.2 Atmospheric Patterning Process
  • 13.3 In-Vacuum Pattering Processes
  • References
  • Section 3
  • 14 The DC Glow Discharge or Plasma
  • 14.1 Introduction
  • 14.2 The Townsend Discharge
  • 14.3 The Breakdown Voltage
  • 14.4 The Transition Region
  • 14.5 The Normal Glow Discharge
  • 14.6 The Abnormal Glow Discharge
  • 14.7 The Arc
  • 14.8 Triodes and Magnetically Enhanced Plasmas
  • 14.9 Hollow Cathode Plasma Source
  • 14.10 Ion Sources
  • References
  • 15 Electron Beam (E-Beam) Evaporation
  • 15.1 Introduction
  • 15.2 Filaments and Electron Emission
  • 15.3 E-beam Control
  • 15.4 Power Supply
  • 15.5 Crucibles and Feed Systems
  • 15.6 System Design
  • References
  • 16 Thermal Evaporation
  • 16.1 Introduction
  • 16.2 Boats
  • 16.3 Wire Feeding
  • 16.4 Wire
  • 16.5 Spitting and Pinholes
  • 16.6 Thin Film Measurement
  • 16.6.1 Optical Density
  • 16.6.2 Resistance Monitoring
  • 16.6.3 Errors in OD and Eddy Current Measurements Used for Coating Thickness
  • 16.7 Power Supplies and Control
  • 16.8 Coating Uniformity
  • 16.9 Coating Strategy
  • 16.10 Reactive Thermal Evaporation of Aluminum Oxide
  • References
  • 17 Radiant Heated, Induction Heated, and Other Sources
  • 17.1 Introduction
  • 17.2 Radiant-Heated Sources
  • 17.2.1 Polymer Sources
  • 17.3 Radiation Shields
  • 17.4 Induction-Heated Sources
  • 17.5 Magnetic Levitation Aluminum Deposition Source
  • 17.6 Jet Vapor Sources
  • 17.7 Molecular Beam Epitaxy (MBE) Sources
  • References
  • 18 Chemical Vapor Deposition/Polymerization onto Webs
  • 18.1 Introduction
  • 18.2 Substrate Temperature
  • 18.3 Power
  • 18.4 Pressure
  • 18.5 Substrate Bias
  • 18.6 Fluorinated Plasma Polymerization
  • 18.6.1 Power
  • 18.6.2 Substrate Bias
  • 18.6.3 Substrate Temperature
  • 18.7 Carbon-Fluorine Plasmas
  • 18.8 CVD of Barrier Coatings
  • 18.9 Atmospheric Plasma Deposition
  • References
  • 19 Atomic Layer Deposition (ALD)
  • 19.1 Introduction
  • 19.2 The process
  • 19.3 Roll-to-Roll ALD
  • References
  • 20 Magnetron Sputtering Source Design and Operation
  • 20.1 Introduction
  • 20.2 DC Planar Magnetron Sputtering Source
  • 20.3 Balanced and Unbalanced Magnetron Sputtering
  • 20.4 Anodes
  • 20.5 Radio Frequency (RF) Sputtering
  • 20.6 HiPIMS - High Power Impulse Magnetron Sputtering
  • 20.7 Arcing and Control of Arcs
  • 20.8 Water Cooling
  • 20.9 End Effects
  • 20.10 Troubleshooting Magnetron Sputtering Sources
  • 20.10.1 Failures in Service
  • 20.10.2 Failures Following Servicing
  • References
  • 21 Magnetron Sputtering Source Design Options
  • 21.1 Introduction
  • 21.2 Single or Dual Magnetron Sputtering Source
  • 21.3 Anode Included or Not?
  • 21.4 Balanced or Unbalanced Magnetic Fields
  • 21.5 Fixed or Variable Magnetic Performance
  • 21.6 Internal or External Fitting
  • 21.7 Direct or Indirect Cooling
  • 21.8 Single or Multiple Materials
  • 21.9 Linked or Isolated Cathodes
  • 21.10 Cost Implications
  • 21.11 Coating Uniformity
  • 21.12 Magnets
  • 21.13 Planar or Rotatable?
  • 21.14 Power Supply Choices
  • References
  • 22 Reactive Sputter Deposition - Setup and Control
  • 22.1 Introduction
  • 22.2 Target Preconditioning
  • 22.3 Control Options
  • 22.4 Hysteresis Loop
  • 22.4.1 Constant Metal Rate, Variable Reactive Gas Flow
  • 22.4.2 Constant Reactive Gas Flow, Variable Metal Rate
  • 22.5 Monitors
  • 22.6 Time Constants
  • 22.7 Pumping
  • 22.8 Gas Input
  • 22.9 Control of Arcs
  • 22.10 RF Sputtering
  • 22.11 Other Processes
  • References
  • Section 4
  • 23 Machine Specification and Build Issues - Risk Analysis - Process
  • 23.1 Introduction
  • 23.2 Risk Analysis - Process
  • 23.3 Mistake Proofing or Fool Proofing
  • 23.4 Project Management
  • 23.5 Safety
  • 23.6 Costs
  • 23.7 Machine Specification
  • 23.8 Maintenance and Spares
  • References
  • 24 Heat Load on the Webs/Foils
  • 24.1 Introduction
  • 24.2 Cooling Webs
  • 24.3 Heat Load Modeling
  • 24.4 Free Span Deposition
  • 24.5 Heated Substrates
  • 24.6 Potential Winding Problems
  • 24.7 Characteristic Winding Problems Associated with Too Much Heat
  • 24.7.1 Tramlines
  • 24.7.2 Ballooning
  • 24.7.3 Shrinking
  • 24.7.4 Polymer Melting and Web Breaks
  • 24.8 Heating Webs
  • 24.8.1 Outgassing
  • References
  • 25 Process Variables
  • 25.1 Introduction
  • 25.2 Drum Surface Roughness
  • 25.3 Polymer Surface Roughness
  • 25.4 Material Properties
  • 25.5 Deposition Rate and Winding Speed
  • 25.6 Water Content of Polymer
  • 25.7 Drum Temperature
  • 25.8 Single or Double Side Coating
  • 25.9 Source Type
  • 25.10 Heat Load Calculations
  • 25.10.1 The Energetic Particle Heat Load
  • 25.10.2 The Chemical Reaction Heat Load
  • 25.10.3 Web Temperature
  • 25.11 Heat Transfer Coefficient
  • 25.12 Cooling Webs
  • 25.13 Electrostatic Pinning
  • References
  • 26 Mechanical Design
  • 26.1 Introduction
  • 26.2 Pumping
  • 26.3 Nonuniform Pumping
  • 26.4 Shields
  • 26.4.1 Deposition Shields
  • 26.4.2 Protective Shields
  • 26.4.3 Conductance Shields
  • 26.4.4 Profile Shields
  • References
  • 27 Winding Webs in Vacuum
  • 27.1 Introduction
  • 27.2 System Design
  • 27.3 Tension Measurement - Load Cells
  • 27.4 Alignment and Spacing
  • 27.5 Materials
  • 27.6 Other Related Items and Materials
  • 27.7 Substrates - Thermally and Dimensionally Variable
  • 27.7.1 Wrinkles
  • 27.8 Safety
  • 27.9 Key Points on Winding
  • References
  • 28 Machine-Building Trends
  • 28.1 Introduction
  • 28.2 Metallizers
  • 28.3 Specialty Vacuum Coaters
  • References
  • 29 System Design
  • 29.1 Introduction
  • 29.2 System Choices
  • 29.3 Batch versus Air-to-Air Processing
  • 29.4 Source Choices
  • 29.5 Summary
  • References
  • 30 Hazards
  • 30.1 Introduction
  • 30.2 Risk Assessment
  • 30.3 Mechanical
  • 30.4 Electrical
  • 30.5 Thermal
  • 30.6 Chemical
  • 30.7 Material Interactions
  • 30.8 Deposition Material and By-Products
  • 30.9 Hazardous Gases
  • 30.10 Cold Traps and Cryopumps
  • 30.11 Cleaning Hazards
  • 30.12 Ergonomic and Miscellaneous
  • References
  • 31 Troubleshooting
  • 31.1 Introduction
  • 31.2 Troubleshooting Vacuum
  • 31.3 Troubleshooting Process
  • 31.4 Troubleshooting Winding Problems
  • 31.4.1 Electrostatic Charge
  • 31.5 Troubleshooting Adhesion
  • 31.6 Troubleshooting - Loss of Barrier
  • 31.7 Troubleshooting - Common Problems and Diagnostic Tools
  • 31.8 Thermal Evaporation by Resistance-Heated Boats
  • 31.8.1 Uniformity
  • 31.9 Electron Beam Deposition
  • 31.10 Magnetron Sputtering
  • 31.10.1 Magnetron Plasma Does Not Light Up
  • 31.10.2 Falling Deposition Rate or Large Voltage Drift During Deposition Cycle
  • 31.10.3 Arcing
  • References
  • 32 Final Thoughts
  • Index
Chapter 1

What Is a Vacuum?


This chapter provides the reader with the basic details of a vacuum. This gives an appreciation of why as the pressure falls the evaporation rate of materials will increase. Also, as the amount of gas is reduced (low pressure or increasing vacuum) the number of gas collisions is reduced and so the distance vapor will travel before being scattered is increased. This line of sight deposition helps to maximize the material collection on the substrate as fewer atoms are scattered away before they reach the substrate.

Keywords


Vacuum; pressure; partial pressure; vapor pressure; saturated vapor pressure; mean free path; monolayer; line of sight; gas collisions

1.1 Introduction


The word vacuum is derived from the Latin word 'vacua' meaning empty. If we empty the chamber of gas we produce a vacuum.

A vacuum could be described as where within an enclosed volume there is less gas per unit volume than is present in a similar volume in the atmosphere surrounding the enclosed volume. This is something that can be used to our advantage.

Those of us who drink tea have all heard tales of not being able to brew a good cup of tea when on the higher slopes of Mount Everest because of the lower pressure and the problem of boiling water at a lower temperature. This effect of reducing the boiling point of materials when under vacuum is one advantage that can be used to good effect.

Many materials, particularly when raised in temperature to the boiling point, are prone to oxidation. Thus another advantage of operating in a vacuum is that materials that would normally be excessively affected by oxidation can have oxygen and water vapor kept away. This is achieved by being within a volume where there are few gas molecules, that is, a vacuum.

1.2 What Is a Gas?


If we look at materials in general they can be in the form of a solid, liquid, or gas. The structure changes with each form. Solids have atoms closely spaced and in fixed positions. Heating the material, the form changes to a liquid where the atoms are disordered and the distance between atoms is greater. With further heating the disorder is still greater and the spacing also much greater. The speed of motion of the atoms also increases with temperature. So let us look at a few facts and figures about gases.

A gas is where atoms or molecules are free to move in any direction and are in constant motion. Typically, these particles are traveling at speeds of approximately 1650 kph (1000 mph).

In air, gas molecules occupy approximately 0.01% of the space as compared to a solid where the molecules occupy approximately 74% of the space. The particles collide with each other or surfaces at a rate of 10,000,000,000 per second. These collisions mean that the gas particles have random motion and will rapidly expand to fill the whole volume. If the number of collisions looks to be large bear in mind that there will be around 20,000,000,000,000,000,000 particles per cubic centimeter and the mean free path (mfp) (the average distance a particle has to travel before it hits another particle) is only 100 nm.

1.3 Pressure


All atoms or molecules have mass and when they hit and bounce off a surface they exert a force on that surface. This force per unit area is known as pressure.

=ForceArea

All atoms or molecules in the atmosphere with their mass are subjected to the gravitational pull of the earth and are attracted to the earth. Thus at high altitudes the pressure is lower because the density of gas is lower.

At the top of Everest, the pressure is less than one-third than that found at sea level. A simple rule of thumb is that the pressure is halved every 5 km away from the earth surface (sea level).

Atmospheric pressure taken at sea level and 45°N latitude is 14.69 pounds per square inch (psi) or 1 kilogram force per square centimeter. If the pressure is taken at a temperature of 0°C the pressure is said to be 1 standard atmosphere (1 std atm)

Atmospheric pressure as a value is often rounded up for convenience.

psi~15psi15psi~760Torr~1stdatm~101325pascal(N/m2)~1.01325bar101.325kPa~1013.25mbar

There is an issue regarding the units used to designate pressure that can be problematic. As long ago as 1978 the Pascal replaced Torr as the acceptable measure of pressure. However, many vacuum systems that were built before this time are still in regular use and also old habits die slowly and so it is still common to find systems using Torr as the measure of pressure.

The Italian, Torricelli, in 1644 made a measurement of pressure using a mercury manometer. His measurement of 760 mm Hg for atmospheric pressure is the basis of the Torr scale used today.

mmHg=1Torr(anabbreviationofTorricelliinhonorofhiswork)1micronHg=1/1000mmHg=0.001mmHg=0.001Torr=1mTorr(mT)

The European preferred unit of pressure is the Pascal or the Newton per square meter. As ever, the Europeans have adopted a unit of measure of pressure that does not quite conform because of not being related to the SI unit by a factor of 103. The unit is the bar where the base unit of 1 bar equals 100000 Pa.

bar=1000mbar=750Torr

Vacuums are often categorized as one of four main types low, medium, high, or ultrahigh vacuum. There are other descriptors that are used that may not always be recognized.

=soft=poor=roughvacuum=1-1013mbarMedium=moderatevacuum=10-3-1mbarHigh=hard=goodvacuum=10-7-10-3mbarUltrahigh=below10-7mbar

It is worth noting that another confusion comes from the changing between describing a vacuum as a high vacuum and then changing to talking about a low-pressure system. Both are correct, a system having a low pressure does have a high vacuum, but it helps to be consistent in the terminology used.

1.4 Partial Pressure


The total pressure of a system is the sum of all the individual gas pressures of the gases present in the system. Each of the gases exerts a pressure and individually they are known as the partial pressures.

A common example is of a chamber open to atmosphere. The air around us is composed of a mixture of gases. Table 1.1 lists the gases present, their relative volumes, and the partial pressure of each. The partial pressure of each gas is relative to its percentage of the total volume; hence the partial pressure is the volume times the percentage present. Thus for oxygen it is 20.95% × 101325 pascal = 21227 pascal.

Table 1.1

The Composition of Air

Nitrogen N2 78.08 79115 593.4 Oxygen O2 20.95 21227 159.2 Argon Ar 0.93 942 7.07 Carbon dioxide CO2 0.03 30.4 0.23 Neon Ne 0.0018 1.82 0.0137 Helium He 0.0005 0.51 0.0038 Methane CH4 0.0002 0.2 0.00152 Krypton Kr 0.0001 0.1 0.00076 Hydrogen H2 0.00005 0.051 0.00038 Xenon Xe 0.0000087 0.0088 0.000066 Water H2O 0.6 to 6.0 607 to 6079.5 4.56 to 45.6

The most common gas pumped to produce a vacuum is air and Table 1.1 shows the most common constituents of air. It is important to note there is one omission from the table that has a big impact on vacuum systems and that is water vapor. Depending upon the local weather and temperature the water vapor content of the atmosphere can be between 0.6 and 6.0 weight percent. Hence in the table the figures are for a basic dry air and then the water vapor, as it is a variable, is given a range of values. If the water vapor present is at the upper end value, the other gases will have a slightly lower percentage volume and hence a slightly lower partial pressure than shown.

1.5 Vapor Pressure


A vapor is a gas that has a tendency to turn back into liquid. In the same way that gases hitting a surface produce a pressure, a vapor likewise bombards the surfaces and exerts a pressure. This is referred to as the vapor pressure.

If we take a pool of liquid such as water and leave it for some time it can be seen to have lost some water by evaporation. If we raised the temperature of the water this would be seen to happen more quickly. If we took the temperature up to the boiling point of the water, the water vapor would be seen as a cloud above the water and the water level would be seen to fall rapidly. So the vapor pressure gives an indication of the rate of evaporation of a material. Solids also have a vapor pressure but, as you would expect, they are tiny by comparison with liquids.

The vapor pressure of all gases is the same at the boiling point in atmosphere, 760 Torr, although the temperature at which they boil is different.

This becomes of practical interest when working with liquid precursors for chemical vapor deposition processes and also for physical...

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Das Dateiformat PDF zeigt auf jeder Hardware eine Buchseite stets identisch an. Daher ist eine PDF auch für ein komplexes Layout geeignet, wie es bei Lehr- und Fachbüchern verwendet wird (Bilder, Tabellen, Spalten, Fußnoten). Bei kleinen Displays von E-Readern oder Smartphones sind PDF leider eher nervig, weil zu viel Scrollen notwendig ist. Mit Adobe-DRM wird hier ein "harter" Kopierschutz verwendet. Wenn die notwendigen Voraussetzungen nicht vorliegen, können Sie das E-Book leider nicht öffnen. Daher müssen Sie bereits vor dem Download Ihre Lese-Hardware vorbereiten.

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