1. Atomic Layer Deposition for SCRF RF in the MTA 11/15/10 J. Norem ANL/HEP

2. 2 Atomic Layer Deposition Atomic Layer by Layer Synthesis Method similar to MOCVD Used Industrially –Semiconductor Manufacture for “high K” gate dielectrics “Abrupt” oxide layer interfaces Pinhole free at 1 nm film thicknesses Conformal, flat films with precise thickness control –Electroluminescent displays No line of sight requirement Large area parallel deposition Parallel film growth technique; Inside of large tubes can be done at once.

3. 3 ALD Reaction Scheme ALD involves the use of a pair of reagents. each reacts with the surface completely each will not react with itself This setup eliminates line of site requirments Application of this AB Scheme Reforms the surface Adds precisely 1 monolayer Pulsed Valves allow atomic layer precision in growth Viscous flow (~1 torr) allows rapid growth ~1  m / 1-4 hours 0 500 1000 1500 2000 2500 3000 3500 4000 050010001500200025003000 AB Cycles Thickness (Å) Ellipsometry Atomic Force Microscopy Film growth is linear with AB Cycles RMS Roughness = 4 Å (3000 Cycles) ALD Films Flat, Pinhole free Flat, Pinhole-Free Film Seagate, Stephen Ferro No uniform line of sight requirement! Errors do not accumulate with film thickness. Fast! (  m’s in 1-3 hrs ) and parallel Pinholes seem to be removed. Bulk

4. 4 Apparatus Hot wall reactor (RT-400 C) Always coat the wall – now it will be useful

5. 5 Demonstrated ALD A/B Reactions Oxide Nitride S/Se/Te Ph/AsCF Element

6. 6 Aerogels coated with W Conformal Coating and “sharp” points Aerogels are low density nanoporous materials consisting of bundles of nm scale filaments ALD can be used to deposit W metal atomic layer by layer on this filaments 10 nm filaments 150 nm Overall Reaction: WF 6 + Si 2 H 6 → W + products

7. 7 Aerogel filament diameter increases with ALD W Cycles SEM TEM 80 nm 3 c W 7 c W 80 nm Microscopy of W-Coated Carbon Aerogels

8. 8 Goal of ALD SCRF Build “nanolaminates” of superconducting materials ~ 10- 30 nm layer thicknesses Nb, Pb Insulating layers Higher-T c SC: NbN, Nb 3 Sn, etc

9. 9 Conclusions ALD is an intriguing synthesis technique with many useful properties Conformal coating means increased radius of curvature Parallel (non-line of sight) method –Flat samples directly map to complex shape samples even with high aspect ratios –Layer by layer growth on complex shapes Useful for higher field gradients in SRF and NCRF