Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Current status of the bulk and coating research in Jena SFB TR 7

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz 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

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz time amplitude f0f0 ff frequency amplitude Measuring Technique Determination of the Q-factor via amplitude ringdown … or bandwidth measurement Φ = 1Q1Q

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Measuring Technique Other used read-out techniques: - capacitive - reflective (splitted photodiode) - fiber Capacitive excitation and interferometric read-out

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Environment for Bulk 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

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Environment for Bulk Material Research Experimental Setup Cryostat Ø 300 mm 500 mm 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 Suitable for bulk and cantilever Q-factor measurements !!!

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Dissipation peaks due to impurities in silicon bulk materials impurities/ defects phonon-phonon Silicon, Ø 3” x 12 mm Φ min = 2.2 x K

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz silicon (FZ), Ø 6“ x 96 mm Temperature [K] mechanical Q-factor dips between 100 and 300K “flat” profile at low temperatures

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz st measurements on silicon samples with different doping levels silicon, Ø 4” x 99 mm 5 samples with a resitivity between 10mΩcm…10kΩcm available

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz quartz substrate grating structure (as will be used) 1st layer silica multilayer Coating/grating research on bulk material samples cryst. quartz,  3“  12 mm

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz substrate + grating + grating nm SiO 2 + graing nm SiO 2 + HR cryst. quartz,  3“  12 mm, Hz Coating/grating research on bulk material samples

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Extracted coating/grating losses Nawrodt et al. New J. Phys. 9 (2007) 225 Higher sensitivity using cantilevers? Coating/grating research on bulk material samples

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Cantilever Coating Research

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Cantilever setup for the “large” cryostat 1 massive base plate 2 cantilever clamping blocks 3 excitation structure mount 4 cantilever

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz Measurement procedure: C1 C2 C3 C4 ExcitationWaitRingdown

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz available frequency range: 20 Hz …. 90 kHz losses at the thermoelastic limit

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz st results of tantala coated cantilevers

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz st results of tantala coated cantilevers 500 nm tantala deposited by e-beam evaporation

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz st results of silica coated cantilevers Mechanical loss comparision of two thermal oxide layers (170nm and 400 nm)

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz New cryostat for coating research Probe chamber dimensions: Ø 220 mm x 80 mm T = 5…325 K p < 3x10 -6 mbar LN2 tank LHe tank

Friedrich-Schiller-University Jena Institute of Solid State Physics – Low Temperature Physics Christian Schwarz 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