Ion Tracks and Microtechnology. Questo articolo non è disponibile.Ion Tracks and Microtechnology

The penetration of heavy charged particles through matter has been the subject of investigations since the early days of Bohr's atomic model. Much later it was found that the resulting traces have dimensions close to the atomic scale and can be revealed in the form of fme patterns. Quite recently, this characteristic attracts applications in micro­ electronics and -mechanics, biology and medicine, surface and membrane technology, magneto-optics and low temperature physics - applications which require a high subtlety of geometric control on a microscopic scale. Progress in advanced technologies depends crucially on the refinement of the available tools. On the road into the submicron regime, customary lithographies using visible and ultraviolet light, x rays, and electrons are steadily nearing their physical limits. A central point in the search for better tools is the improvement of irradiation technology. Ions have a well-defined range of penetration, a high local confmement of the deposited energy and can be generated conveniently in great quantity. The generated dam­ age zones can be stored indefmitely in many insulators and be used to initiate a phase transformation process that changes, removes, or collects material along the latent tracks. Up to now the most common development process is track etching, which acts as a chemical amplifier that dissolves the damaged zone of the latent tracks preferentially and creates etch pits or channels that can be extremely fine, starting around 10 nm and in­ creasing .linearly with the etching time.

I Principles of track creation.- 1 Irradiation technology.- 1.1 Radioactive sources.- 1.1.1 Nuclear reactors.- 1.1.2 Alpha and fission sources.- 1.2 Ion accelerators.- 1.2.1 Characteristic parameters of accelerators.- 1.2.2 Production of highly charged heavy ions.- 1.2.3 Ion deflection and focussing.- 1.2.4 Acceleration techniques.- 1.2.5 Behavior of ions at relativistic energies.- 1.3 Irradiation targets and equipment.- 1.3.1 Wide-beam irradiation devices.- 1.3.2 Scanning ion microbeams.- 1.4 Radiation safety.- 1.4.1 Handling of radioactive sources.- 1.4.2 Basics of sample activation by accelerated ions.- 2 Energy-loss phenomena.- 2.1 Energy-transfer to target electrons.- 2.1.1 Binary-encounter model.- 2.1.2 Impact parameter and scattering angle.- 2.1.3 Transferred kinetic energy.- 2.1.4 Energy-loss per unit length-of-path.- 2.1.5 Cut-off energy.- 2.1.6 Bohr’s energy-loss relation.- 2.1.7 Charge-state of projectile-ion.- 2.1.8 Charge-corrected energy-loss relation.- 2.2 Secondary energy-loss effects.- 2.2.1 Energy-loss in multi-elemental targets.- 2.2.2 Energy-straggling and angular straggling.- 2.2.3 Energy-transfer to target nuclei.- 2.2.4 Calculation of ion range.- 3 Formation of the latent track.- 3.1 Track core ― atomic defects.- 3.1.1 Coulomb explosion model.- 3.1.2 Atomic collision-cascade.- 3.1.3 Thermal-spike model.- 3.1.4 Resulting primary defects.- 3.1.5 Diffusion and relaxation of defects.- 3.2 Track halo ― electronic defects.- 3.2.1 Electron emission from ion trajectory.- 3.2.2 Secondary-electron collision-cascade.- 3.2.3 Translation of deposited energy into effect.- 4 Development of ion tracks.- 4.1 Nucleation of a new phase.- 4.1.1 Origin of phases.- 4.1.2 Basic theory of interface energy.- 4.1.3 Condition for grain growth.- 4.1.4 Formation of condensation nuclei.- 4.2 Track response function.- 4.2.1 Track etch threshold.- 4.2.2 Track sensitization and annealing.- 4.3 Shape of etched tracks.- 4.3.1 Primary factors in track etching.- 4.3.2 Fick’s first diffusion law.- 4.3.3 Calculation of track shapes.- 4.3.4 Tracks in crystals.- 5 Observation of ion tracks.- 5.1 Microscopic observations.- 5.1.1 Optical microscope.- 5.1.2 Scanning electron microscope.- 5.1.3 Transmission electron microscope.- 5.2 Diffraction techniques.- 5.2.1 Basic principles.- 5.2.2 Small-angle scattering.- 5.2.3 X ray topography.- 5.3 Auxiliary techniques.- 5.3.1 Electron spin resonance.- 5.3.2 Electrical observations.- 5.3.3 Gas-permeation.- 5.3.4 Mechanical observations.- 6 Resulting structures.- 6.1 Fundamental shapes of etched tracks.- 6.1.1 Single-ion tracks.- 6.1.2 Non-overlapping tracks.- 6.1.3 Overlapping tracks.- 6.1.4 Further possibilities.- 6.2 Stochastic track patterns.- 6.2.1 Two-dimensional track overlap.- 6.2.2 Three-dimensional track overlap.- II Track applications.- 7 Single-ion tracks.- 7.1 Number, size, and deformability of particles.- 7.1.1 Basic relations.- 7.1.2 Resistive pulse technique.- 7.1.3 Deformability and interface energy.- 7.1.4 Red blood cell deformability.- 7.1.5 Suggested pore shapes.- 7.2 Single-pores and super fluidity.- 7.2.1 Basic phenomena.- 7.2.2 Basic relations.- 7.2.3 Flow through a single pore.- 7.2.4 Suggested shapes of weak links.- 8 Multiple ion tracks.- 8.1 Enhanced diffusion.- 8.1.1 Diffusion equations.- 8.1.2 Electric analogue of diffusion equations.- 8.1.3 Solution of dynamic diffusion equation.- 8.1.4 Connected-cavity model.- 8.1.5 Gas permeation through latent tracks.- 8.2 Membrane technology.- 8.2.1 Ion track filters.- 8.2.2 Prospects of track membranes.- 9 Bulk properties.- 9.1 Adjusting magnetic properties.- 9.1.1 Magnetic properties of matter.- 9.1.2 Matrix model of magneto-optic films.- 9.1.3 Experimental results.- 9.1.5 Generation of anisotropy.- 10 Growth areas.- 10.1 Ion lithography.- 10.1.1 Basic techniques in lithography.- 10.1.2 Ion lithographic techniques.- 10.2 Surface texture.- 10.2.1 Light scattering devices.- 10.2.2 Antireflection treatment.- 10.2.3 Further possibilities.- Concluding remarks.- Definitions and units.- List of symbols.