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Mo/Au Transition-Edge Hot-Electron Micro-Bolometers

Mo/Au Transition-Edge Hot-Electron Micro-Bolometers. Shafinaz Ali , S. Malu , D. McCammon , K. L. Nelms , R. Pathak , P. T. Timbie , D. van der Weide University of Wisconsin-Madison, Madison, WI 53706

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Mo/Au Transition-Edge Hot-Electron Micro-Bolometers

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  1. Mo/Au Transition-Edge Hot-Electron Micro-Bolometers Shafinaz Ali , S. Malu , D. McCammon , K. L. Nelms , R. Pathak , P. T. Timbie , D. van der Weide University of Wisconsin-Madison, Madison, WI 53706 C.A.Allen, J. Abrahams, J. Chervenak, W.-T. Hsieh, T. M. Miller, H. Moseley, T.R.Stevenson, E.J. Wollack NASA Goddard Space Flight Center, Greenbelt, MD 20771 Astronomy 2004 SPIE Glasgow

  2. Outline • Motivation • Thermal Model • Fabrication • Thermal test results of Mo/Au THMs • Application • Conclusion

  3. CMB Power Spectra

  4. Advantages of TES bolometers • Background limited sensitivity • Short time constant • Wide spectral range • Immunity to cosmic rays • Low microphonic noise • Simple readout system • Diffraction limited angular resolution

  5. Planar Antenna-Coupled Transition-Edge Hot-Electron Micro-Bolometer (THM)

  6. THM Microwave circuit Thermal Model No cuts in ground plane and Si substrate!!

  7. Mo/Cu THM by wet etch • Cu (170nm) is wet etched to form the TES • The Mo(40 nm) traces are defined by dry plasma etching SEM image of Mo/Cu TES

  8. Mo/Au THM by dry etch • Ion mill Au (150nm) with Argon • Flourine etch underlying Mo(40nm) • Bi/Au absorber ( 500/150 nm) SEM image of THM.

  9. G from thermal model Gep= 5SVT4 GwF= LoT/R

  10. Cold-stage Testing Setup

  11. THM: R vs T

  12. R vs T Curve with constant current Bias

  13. R vs T curves for the same device with different dc currents through the bismuth absorber/heater

  14. Constant Voltage bias

  15. Results &… • Hot electron effect has been demonstrated • Measured G value is 2 x10 -8 W/K • Measured a value is 195 • Measured time constant ~ 30ms • Things to do … • Noise measurement • Different geometry • Coupling to antenna • 90Ghz antenna system under construction • Rf measurements

  16. Millimeter Bolometric Interferometer (MBI) • 8 feedhorns (28 baselines) • 90 GHz (3 mm) • ~1o angular resolution – search for B-mode pol’n • 7o FOV • under construction, first light expected winter 2005 • White Mountain, CA (13,500 ft)

  17. Application Adding Interferometry with bolometers: integrated microwave circuit on a chip

  18. Conclusion • We have fabricated Bi/Au absorbers with contact with Mo/Au bilayer TES. • The measured thermal conductivity and time constant are in good agreement with those expected from the electron-phonon interaction in the metal films. • Devices of this type with either smaller volume or lower values of Tc will be suitable for low background measurements of millimeter waves for astrophysics.

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