1 / 11

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

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

mahina
Télécharger la présentation

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

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mo/Au Transition-Edge Hot-Electron Micro-Bolometers S. 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

  2. Abstract We are developing a new type of detector for observational cosmology and astrophysical research. Incoming radiation from the sky is coupled via a planar antenna and superconducting transmission lines to a thin metal film absorber. At sub-Kelvin temperatures the thermal isolation between the electrons and the lattice causes the radiation to selectively heat the electrons in the small absorber. An adjacent superconducting transition-edge sensor (TES) is thermally coupled to the hot electrons and measures their temperature. The volume of the absorber and TES is a few cubic microns. We call this detector Transition-edge Hot-electron Micro-bolometer (THM). We have constructed and tested a scale model of a planar antenna. We have tested the thermal properties of Mo/Au TES devices.

  3. Bismuth Nb microstrip Z ~ 10W Mo leads Mo/Au bilayer GAndreev GAndreev GWF e Superconducting leads e Superconducting leads Gep IRF from antenna e Lattice Phonons Model of a THM The weak electron –phonon link provides the thermal isolation for the hot electron microbolometer. Absorber

  4. Planar Antenna-Coupled THMs THMs can be easily coupled to lithographically fabricated polarization sensitive slot antennas via superconducting micro-strip lines.

  5. Test Device Fabrication THM devices are fabricated by patterning Mo(40nm) /Au (156.5nm) bilayer. 1) Apply Trench mask. Ion mill gold. RIE Mo. 2) Apply TES mask . Ion mill gold. 3) Apply Mo leads mask. RIE Mo. 4) Evaporate 500 nm Bi absorber/heater and pattern by lift-off.

  6. R vs T Curve with Different Bias Currents The test THM is 10 mm x 20 mm x 196.5nm thick. A 10 mm x 100 mm x 500 nm thick Bi absorber covers the TES. The absorber does not “proximitize’ the TES. The transition curve of a TES with an absorber is very similar to that of one without an absorber. Resistance versus temperature curves measured at constant current for the test device show a steep transition ~ 5mK wide. The measurements are made with a shielded ADR.

  7. R vs T curves for the same device with different dc currents through the bismuth absorber/heater The test device TES was biased with a constant ac bias current (0.6 mA) while the absorber was heated by a dc current. The absorber has a resistance of about 2 ohms. A value for G can be calculated from this data which is consistent with the electron-phonon decoupling model.

  8. Simulation for thermal conductance The internal electron electron thermal conductance in the absorber is given by: Gwf= Lo T/Rabs Where, Lo = Lorentz constant T= temperature Rabs = Resistance of the absorber The electron-phonon thermal conductance is given by Ge-ph = 5SVT4 , where S= constant dependent on the absorber material, V= volume of the absorber, and T= temperature.

  9. Estimation of Alpha The R vs. T curves for the test device were taken with constant current bias. But a TES is actually voltage biased when read out by a SQUID. The constant voltage points calculated from the previous constant current bias curves are plotted versus temperature to estimate alpha.

  10. By comparing our data with the electron-phonon thermal conductance model we conclude that there are two separate paths for the heat to get from the hot electrons in the Bi absorber to the substrate 1)e-p interactions in the Bi absorber 2) e-p interactions in the Mo/Au TES. The data suggests that the dominant conduction path to the lattice is through the TES. Calculated electron-phonon conductance Electrical power dissipated in the absorber as a function of the electron temperature(T_tes) and the phonon temperature (T_bath). In these tests, T_tes is constant at T_tes= Tc.

  11. Conclusion • We have measured the R vs T for a small TES device. • Addition of a thick Bi absorber on top of a small TES device does not seem to affect its electrical properties. • The value of thermal conductance calculated from data is consistent with electron-phonon decoupling in both Bi and Mo/Au films. • We plan to measure the device in voltage bias mode shortly. • We have fabricated some 10mm x 10mm Mo/Cu THM devices with Cu absorbers for comparison.

More Related