Repetition: Ion Plating

Transcription

1 Repetition: Ion Plating Substrate HV (bis ca. 1kV) Optional ionization system Source Ionized filling gas Source material, ionized or neutral

2 Repetition: Ion Plating Ion Species Separated ion source Ions from gas discharge Ions of the coating material

3 Repetition: Ionization Degrees Method Evaporation Electron Gun Sputtering Low Voltage-Arc Discharge Arc-Evaporation Pulsed Magnetron Ionization Degree [%] <0.1 < >50 bis 100 Reason of Ionization Therm. excitation Therm. excitation Collisions High Power density High Power density Average Power density

4 Repetition: Power Densities Method Sputtering Evaporation Electron gun Pulsed Magnetron Low Voltage Arc Discharge Arc-Evaporation Power Density [Wcm -2 ]

5 Repetition: Ion Bombardement and Film Growth Bombardement with foreign ions: Evaporation Electron gun Sputtering Reason: low ionization degree Bombardement with coating ions: Low voltage arc dsischarge Arc discharge Reason: high ionization degree

6 Repetition: CVD Reaction types 1. Chemosynthesis (Reactions with Gases) TiCl 4 (g) 1/2N 2 (g) 2H 2 (g) C mbar 2. Pyrolysis (thermal decomposition) SiH 4 (g) <650 C Si(s) 2H 2 (g) 3. Disproportionation 2GeJ 2 (g) Ge(s) GeJ 4 (g) 4. Photopolymerization TiN(s) 4HCl(g)

7 Repetition: PACVD Reduction of growth temperature

8 Repetition: Plasma Polymerization Monomers: Hexamethyldisiloxane (HMDSO), C 6 H 18 OSi 2 Tetraethylorthosilikate (TEOS) Deposited material: mostly SiO 2

9 Electrochemistry Process types Cathodic deposition Anodic oxidation Electroless deposition

10 Cathodic Deposition (Galvanics) Basic set up Potential curve - U(x) - Me S - - K 300 nm Cathode fall: cathode screened by positive ions A x Basic characteristics: Metallic substrates Mostly aqueous solutions Narrow parameter window in T Large parameter window of chemical additives

11 Cathodic Deposition: Theory Elementary processes in the cathode fall 300 nm Neutralization of metallic ion by cathode electron Detachment of OH - groups by strong potential Hydradized metallic ion - Estimation of field strength: U=4 V d=300 nm E = approx V/m (!)

12 Cathodic Deposition: Special Processes Pulse galvanics: current pulses to influence the granularity of the film Galvanic multilayers by deposition from mixed electrolytes at different cathode voltages Multiple baths Agitation of bath for enhancement of material transport Deposition of dispersion coatings by intermixing of micro- and nanocrystalline particles into the electrolyte (Aluminum oxide, Zirconium oxide,...) Deposition from non-aqueous electrolytes: e. g.: Al: Trialkylaluminum containing electrolyte Deposition directly from the melt of the metallic salt

13 Anodic Oxidation: Fundamentals Chemistry: kJ 2Al 3O Al 2 O 3 Alumina grows to thick films, because pores enable contact to the metallic substrate. The initially porous coating can be infiltrated and colored. Afterwards it is densified. The method is extremely shape conserving. No additional coating is deposited, only the substrate material is transformed.

14 Electroless Deposition Reduction of metal ions by electrons which are supplied by a reagens introduced into the solution. The reaction takes place only at a catalytic surface (metal surface, because electrons can easily be set free). To sustain the deposition process, the deposited material has to be auto-catalytic. If there is no catalytic surface (insulator): activation by PdCl 2 or SnCl 2 ; Pd or Sn are directly deposited on the surface. They act catalytically. Reagences: Natrium-Hypophosphite: Ni, Co Natrium-Boron Hydride: Ni, Au Dimethylaminborane: Ni, Co, Au, Cu, Ag Hydrazine: Ni, Au, Pd Formaldehyde: Cu

15 Applications of Electrocemical Methods Decorative elements Emblems Consumer jewellery All side coating of polymer substrates Micro electronics (Cu-interconnects) Micro magnetism (filling of porous templates)

16 Spray Pyrolysis Spraying of metallic salt solutions or chemical complexes in the form of aerosols (manufactured by inert carrier gases) onto hot (metal) surfaces. The thermal energy of the solid surface is used to detatch the chemical residues of the metallic salts, and to "set free " the coating material. Spray-Pyrolyse von Titanoxid

17 Langmuir Blodgett films D = Dipping L = Lifting Polar group Non-polar part of an organic molecule

18 Atomic Layer Deposition Atomic Layer Deposition can be performd in the liquid as well as in the solid phase. Basis: self-passivating chemical reaction. Process: three repeatable steps Step I: Deposition of a (e. g. metal-organic) precursor onto the surface; The precursor is deposited with exactly one monolayer thickness, because the sticking coefficient of the precursor molecules onto themselves is extremely low. Step II: The ligands of the precursor are removed by a second reactive chemical which is introduced into the reaction chamber. Step III: repeated deposition of the precursor onto the free metal. Again only one ML of the precursor is deposited due to it's self passivation.