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Current status of the bulk and coating research in Jena

This article provides an overview of the current status of the bulk and coating research in Jena, including cryogenic Q-factor measurement setup, temperature dependence of Q-factor in silicon bulk materials, and investigations on multilayer coatings. The effects of different doping levels, impurities, and crystal orientations are also discussed.

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Current status of the bulk and coating research in Jena

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  1. Current status of the bulk and coating research in Jena SFB TR 7

  2. Overview • - Cryogenic Q-factor measurement setup • - Temperature dependence of the Q-factor / loss of silicon bulk materials • + different doping levels • + impurities • + crystals orientations • - Single and multilayer loss dependence on crystalline quartz bulk material • - Cantilever setup and first coating investigantions

  3. 1 Q Φ = f0 amplitude amplitude Df time frequency Measuring Technique Determination of the Q-factor via amplitude ringdown … or bandwidth measurement

  4. Measuring Technique Capacitive excitation and interferometric read-out Other used read-out techniques: - capacitive - reflective (splitted photodiode) - fiber

  5. Environment forBulk Material Research Requirements for cryogenic Q-measurements - low pressure to avoid pressure damping - wide temperature range - long term stability in: > temperature (± 0.2K for hours) > seismic isolation - low external damping due to the suspension

  6. Ø 300 mm 5 1 500 mm 2 3 4 Suitable for bulk and cantilever Q-factor measurements !!! Environment forBulk Material Research Experimental Setup Cryostat 1 probe chamber 2 experimental platform 3 LHe tank (49 l) 4 LN2 tank (62 l) 5 heat radiation shields > T = 5…325 K ΔT = ± 0.1 K > p < 3x10-6 mbar > LHe hold time of 36 h

  7. Dissipation peaks due to impurities in silicon bulk materials phonon-phonon Φmin = 2.2 x 10-9 @ 5.8 K impurities/ defects Silicon, Ø 3” x 12 mm

  8. mechanical Q-factor Temperature [K] “flat” profile at low temperatures silicon (FZ), Ø 6“ x 96 mm dips between 100 and 300K

  9. 1st measurements on silicon samples with different doping levels • 5 samples with a resitivity between 10mΩcm…10kΩcm available silicon, Ø 4” x 99 mm

  10. Coating/grating research on bulk material samples • quartz substrate • grating structure (as will be used) • 1st layer silica • multilayer cryst. quartz,  3“  12 mm

  11. Coating/grating research on bulk material samples substrate + grating + grating + 200 nm SiO2 + graing + 200 nm SiO2 + HR cryst. quartz,  3“  12 mm, 11670 Hz

  12. Coating/grating research on bulk material samples Extracted coating/grating losses Nawrodt et al. New J. Phys. 9 (2007) 225 Higher sensitivity using cantilevers?

  13. Cantilever Coating Research

  14. Cantilever setup for the “large” cryostat 4 3 2 1 1 massive base plate 2 cantilever clamping blocks 3 excitation structure mount 4 cantilever

  15. Excitation Wait Ringdown Measurementprocedure: C1 C2 C3 C4

  16. • available frequency range: 20 Hz …. 90 kHz • losses at the thermoelastic limit

  17. 1st results of tantala coated cantilevers

  18. 1st results of tantala coated cantilevers 500 nm tantala deposited by e-beam evaporation

  19. 1st results of silica coated cantilevers Mechanical loss comparision of two thermal oxide layers (170nm and 400 nm)

  20. New cryostat for coating research • Probe chamber dimensions: Ø 220 mm x 80 mm • T = 5…325 K • p < 3x10-6 mbar • 7,5l @ LN2 tank • 6,5l @ LHe tank

  21. Conclusions - 2 independent cryostats for Q-factor measurements on bulk materials and cantilevers - 1st of 5 different doped silicon bulk samples is almost finished - the influence to the Q-factor of grating and a multilayer stack on cryst. quartz substrate was shown

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