Atom Probe Microscopy

Preface Acknowledgements List of Acronyms and Abbreviations List of Terms List of Non-SI Units and Constant Values PART I Fundamentals 1. Introduction 2. Field Ion Microscopy 2.1 Principles 2.1.1 Theory of field ionisation 2.1.2 'Seeing' atoms - field ion microscopy 2.1.3 Spatial resolution of the FIM 2.2 Instrumentation and Techniques for FIM 2.2.1 FIM instrumentation 2.2.2 eFIM or digital FIM 2.2.3 Tomographic FIM Techniques 2.3 Interpretation of FIM Images 2.3.1 Interpretation of the image in a pure material 2.3.2 Interpretation of the image for alloys 2.3.3 Selected applications of the FIM 2.3.4 Summary 3 From Field Desorption Microscopy to Atom Probe Tomography 3.1 Principles 3.1.1 Theory of field evaporation 3.1.2 'Analysing' atoms one-by-one: atom probe tomography 3.2 Instrumentation and Techniques for APT 3.2.1 Experimental setup 3.2.2 Field desorption microscopy 3.2.3 High voltage pulsing techniques 3.2.4 Laser pulsing techniques 3.2.5 Energy compensation techniques Part II Practical aspects 4. Specimen Preparation 4.1 Introduction 4.1.1 Sampling issues in microscopy for materials science and engineering 4.1.2 Specimen requirements 4.2 Polishing methods 4.2.1 The electropolishing process 4.2.2 Chemical polishing 4.2.3 Safety Considerations 4.2.4 Advantages and limitations 4.3 Broad ion beam techniques 4.4 Focused ion beam techniques 4.4.1 Cut-away methods 4.4.2 Lift-out methods 4.4.3 The final stages of FIB preparation 4.4.4 Understanding and minimising ion beam damage and other artefacts 4.5 Deposition methods 4.6 Methods for organic materials 4.6.1 Polymer microtips 4.6.2 Self-assembled monolayers 4.6.3 Cryopreparation 4.7 Other Methods 4.7.1 Dipping 4.7.2 Direct growth of suitable structures 4.8 Specimen geometry issues 4.8.1 Influence of specimen geometry on atom probe data 4.8.2 Stress states and specimen rupture 4.9 A guide to selecting an appropriate specimen preparation method 5. Experimental protocols in Field Ion Microscopy 5.1 Step-by-step procedures for FIM 5.2 Operational space of the field ion microscope 5.2.1 Imaging gas 5.2.2 Temperature 5.2.3 The best image field 5.2.4 Other parameters 5.2.5 Summary 6. Experimental protocols 6.1 Specimen alignment 6.2 Aspects of mass spectrometry 6.2.1 Detection of the ions 6.2.2 Mass spectra 6.2.3 Formation of the mass spectrum 6.2.4 Mass resolution 6.2.5 Common artefacts 6.2.6 Elemental identification 6.2.7 Measurement of the composition 6.2.8 Detectability 6.3 Operational space 6.3.1 Flight path 6.3.2 Temperature / Pulse fraction 6.3.3 Selecting the pulsing mode 6.3.4 Pulse rate 6.3.5 Detection rate 6.4 Specimen failure 6.5 Data quality assessment 6.5.1 Field desorption map 6.5.2 Mass spectrum 6.5.3 Multiple events 6.5.4 Discussion 7. Tomographic reconstruction 7.1 Projection of the ions 7.1.1 Estimation of the electric field 7.1.2 Field distribution 7.1.3 Ion trajectories 7.1.4 Point projection 7.1.5 Radial projection with angular compression 7.1.6 Discussion 7.2 Reconstruction 7.2.1 General considerations 7.2.2 Bas et al. protocol 7.2.3 Geiser et al. protocol 7.2.4 Gault et al. protocol 7.2.5 Reflectron-fitted instruments 7.2.6 Summary and discussion 7.3 Calibration of the parameters 7.3.2 Discussion 7.3.3 Limitations of the current procedure 7.4 Common artefacts 7.4.2 Correction of the reconstruction 7.5 Perspectives on the reconstruction in atom probe tomography 7.5.1 Advancing the reconstruction by correlative microscopy 7.5.2 In correlation with simulations 7.5.3 Alternative ways to exploit existing data 7.6 Spatial resolution in APT 7.6.1 Introduction 7.6.2 Means of investigation 7.6.3 Definition 7.6.4 On the in-depth resolution 7.6.5 On the lateral resolution 7.6.6 Optimisation of the spatial resolution 7.7 Lattice rectification PART III Applying atom probe techniques for materials science 8. Analysis techniques for atom probe tomography 8.1 Characterising the Mass Spectrum 8.1.1 Noise Reduction 8.1.2 Quantifying Peak Contributions via Isotope Natural Abundances 8.1.3 Spatially dependent identification of mass peaks 8.1.4 Multiple Detector Event Analyses 8.2 Characterising the chemical distribution 8.2.1 Quality of atom probe data 8.2.2 Random comparators 8.3 Grid-based counting statistics 8.3.1 Voxelisation 8.3.2 Density 8.3.3 Concentration analyses 8.3.4 Smoothing by delocalisation 8.3.5 Visualisation techniques based on iso-concentration and iso-density 8.3.6 One-dimensional profiles 8.3.7 Grid-based frequency distribution analyses 8.4 Techniques for describing atomic architecture 8.4.1 Nearest neighbour distributions 8.4.2 Cluster Identification Algorithms 8.4.3 Detection Efficiency Influence on Nanostructural Analyses 8.5 Radial Distribution 8.5.1 Radial distribution and pair correlation functions 8.5.2 Solute Short Range Order Parameters 8.6 Structural Analyses 8.6.1 Fourier Transforms for APT 8.6.2 Spatial Distribution Maps 8.6.3 Hough Transform 9. Atom probe microscopy and materials science 9.1 Compositional analysis 9.2 Defects/ dislocations 9.3 Solid solutions / clustering 9.4 Precipitates 9.5 Ordering reaction 9.6 Spinodal decomposition 9.7 Interface/boundaries/layers 9.8 Amorphous materials 9.9 Atom probe crystallography Appendices A. Appendix - chi2 distribution B. Appendix - Polishing chemicals and conditions C. File formats used in APT POS EPOS RNG RRNG ATO ENV PoSAP Cameca root files - RRAW, RHIT, ROOT D. Appendix - Image Hump Model Predictions E. Appendix - Essential Crystallography for APT Bravais lattices Notation Structure factor (F) rules for BCC, FCC, HCP Interplanar spacings (dhkl) Interplanar angles (phi) F. Stereographic Projections and commonly observed desorption maps Stereographic projection for the most commonly found structures and orientations Face-centred cubic Body-centred cubic Diamond cubic Hexagonal close-packed G. Periodic tables H. Kingham Curves I. List of elements and associated mass to charge ratios J. Possible element identity of peaks as a function of their location in the mass spectrum