Effect of a Thin AlOx Layer on Transition-Edge Sensor Properties

Kinnunen, Kimmo; Palosaari, M. R. J.; Maasilta, I. J.

doi:10.1007/s10909-012-0476-z

Cited by 2 publications

(3 citation statements)

References 9 publications

(11 reference statements)

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“…Furthermore, from the high values of C 2 obtained above, and from previous measurements in Ref. 32 , we suspect that the AlOx layer could be responsible for the high value of C 2 . Therefore, we also studied devices where only a quarter "slice" of the full CorTES disk is retained: this way the insulator layer is not required, as the center contact lead can come from the opposite side (see inset Fig.…”

Section: Slice Tessupporting

confidence: 64%

“…This could be because of the 120 nm thick AlOx insulator layer separating the Nb bias lines [1(b)] in the CorTES device, creating unwanted thermal links and heat capacity inside, as shown in Ref. 32 for a different device. Very accurate determination of how the addition of the absorber affected the detector characteristics is unfortunately complicated, because the absorber processing changed also the transition properties, by lowering the T c from 98 mK to 85 mK, and by broadening the transition.…”

Section: Resultsmentioning

confidence: 99%

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Normal metal-superconductor decoupling as a source of thermal fluctuation noise in transition-edge sensors

Kinnunen

Palosaari

Maasilta

2012

Journal of Applied Physics

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We have studied the origin of excess noise in superconducting transition-edge sensors (TES) with several different detector designs. We show that most of the observed noise and complex impedance features can be explained by a thermal model consisting of three bodies. We suggest that one of the thermal blocks and the corresponding thermal fluctuation noise arises due to the high-frequency thermal decoupling of the normal and superconducting phase regions inside the TES film. Our results are also consistent with the prediction that in thin bilayer proximitized superconductors, the jump in heat capacity at the critical temperature is smaller than the universal BCS theory result.

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Section: Slice Tessupporting

confidence: 64%

Section: Resultsmentioning

confidence: 99%

Normal metal-superconductor decoupling as a source of thermal fluctuation noise in transition-edge sensors

Kinnunen

Palosaari

Maasilta

2012

Journal of Applied Physics

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“…The exact processes that roughen the silicon are unclear, but the likely candidates are micro-masking due to non-volatile species in the plasma, and slower etch of native and in-situ NbO x in the fluorine chemistry. The use of an etch stop such as 100 nm thick AlO x was successfully employed in early devices, however, these detectors exhibited very large uncontrolled heat capacity due to the amorphous nature of the etch stop [24]. Test devices were also fabricated with a lift-off process that left the beam surfaces smooth.…”

Section: Diffusive-ballistic Conductancementioning

confidence: 99%

Precision control of thermal transport in cryogenic single-crystal silicon devices

Rostem

Chuss

Colazo

et al. 2014

Journal of Applied Physics

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We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path ℓ is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than ℓ, even when the surface is fairly smooth, 5-10 nm rms, and the peak thermal wavelength is 0.6 µm. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order ℓ, the conductance is dominated by ballistic transport and is effectively set by the beam area. We have demonstrated a uniformity of ±8% in fractional deviation for ballistic beams, and this deviation is largely set by the thermal conductance of diffuse beams that support the micro-electro-mechanical device and electrical leads. In addition, we have found no evidence for excess specific heat in single-crystal silicon membranes. This allows for the precise control of the device heat capacity with normal metal films. We discuss the results in the context of the design and fabrication of large-format arrays of far-infrared and millimeter wavelength cryogenic detectors. * Electronic address: karwan.rostem@nasa.gov

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Effect of a Thin AlOx Layer on Transition-Edge Sensor Properties

Cited by 2 publications

References 9 publications

Normal metal-superconductor decoupling as a source of thermal fluctuation noise in transition-edge sensors

Normal metal-superconductor decoupling as a source of thermal fluctuation noise in transition-edge sensors

Precision control of thermal transport in cryogenic single-crystal silicon devices

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