SIS and bolometer mixers for terahertz frequencies

Gundlach, K. H.; Schicke, M.

doi:10.1088/0953-2048/13/12/202

Cited by 16 publications

(5 citation statements)

References 97 publications

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“…Superconducting hot electron bolometer (HEB) mixers are now used as the most sensitive heterodyne detectors to observe faint THz signals particularly for astronomical and atmospherical studies. [1,2] In the case of the phonon-cooled HEB mixers, [3] a superconducting film should be as thin as a few nm for rapid and efficient cooling of hot electrons caused in the mixing process. As superconducting materials, NbN or NbTiN is usually used.…”

Section: Introductionmentioning

confidence: 99%

Improvement of the critical temperature of superconducting NbTiN and NbN thin films using the AlN buffer layer

Shiino

Shiba

Sakai

et al. 2010

Supercond. Sci. Technol.

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Thin superconducting NbTiN and NbN films with a few nm thickness are used for various device applications including hot electron bolometer mixers. Such thin films have lower critical temperature (T c) and higher resistivity than corresponding bulk materials. To improve them, we have investigated an effect of the AlN buffer layer between the film and the substrate (quartz or soda lime glass). The AlN film is deposited by DC magnetron sputtering, and the process condition is optimized so as that the X-ray diffraction intensity from the 002 surface of Wurtzite AlN becomes highest. By use of this well-characterized buffer layer, T c and resistivity of the NbTiN film with a few nm thickness are remarkably increased and decreased, respectively, in comparison with those without the buffer layer. More importantly, the AlN buffer layer is found to be effective for NbN. With the AlN buffer layer, T c is increased from 7.3 K to 10.5 K for the 8 nm NbN film. The improvement of T c and resistivity originates Improvement of T c of NbTiN and NbN Thin Films Using the AlN Buffer Layer 2 from the good lattice matching between the 002 surface of AlN and the 111 surface of NbTiN or NbN, which makes better crystallization of the NbTiN or NbN film. This is further confirmed by the X-ray diffraction measurement.

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Section: Introductionmentioning

confidence: 99%

Improvement of the critical temperature of superconducting NbTiN and NbN thin films using the AlN buffer layer

Shiino

Shiba

Sakai

et al. 2010

Supercond. Sci. Technol.

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“…Compared with NbN films, NbTiN films possess higher superconducting transition temperature and higher chemical stability, and are potential materials for superconducting single photon detectors [23][24][25]. The defects in NbTiN films (even in epitaxial films), such as nitrogen vacancies, Nb (or Ti) interstitials, and dislocations, are unavoidable [26,27].…”

Section: Introductionmentioning

confidence: 99%

Vortex-glass transition and vortex pinning behavior in three-dimensional NbTiN epitaxial films

Han,

Jing,

Yang

et al. 2024

Supercond. Sci. Technol.

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In the present paper, the vortex dynamics in two NbTiN epitaxial ﬁlms have been explored via analyzing the current-voltage (I-V ) curves measured at diﬀerent temperatures and ﬁelds. The thicknesses of the two ﬁlms are ∼50 and ∼100 nm, respectively, and they are three-dimensional (3D) with respect to superconductivity. The ﬁlms transform from normal state to superconducting state with decreasing temperature at zero ﬁeld, and the values of superconducting transition temperature Tc are 8.73 and 12.03 K for the ∼50- and ∼100-nm-thick films, respectively. When a magnetic ﬁeld with magnitude 0.5 T≤μ0H≤7 T and perpendicular to the ﬁlm plane is applied, the isothermal I-V data show a 3D vortex-glass (VG) scaling collapse at each ﬁeld, suggesting that a 3D vortex-liquid phase to VG phase transition occurs in the NbTiN ﬁlms. By analyzing the critical current density, we found that core pinning is the main pinning mechanism in the ﬁlms. In addition, it is found that the normal point-like pinning dominates the pinning behavior at low ﬁeld regime. While in the high ﬁeld regime, besides the normal point-like pinning, other pinning mechanisms, such as Δκ pinning, also exist in the ﬁlms. Our results not only provide strong experimental support for the occurrence of VG phase transition in conventional superconductors, but also provide fundamental information for the application of NbTiN ﬁlms.

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“…1) The superconductor-insulator-superconductor (SIS) mixer does not show good performance above 1.2 THz owing to the absorption of THz photons by the superconducting material itself, even if NbN or NbTiN is employed as a superconducting material. 2) Hence, HEB mixers have been extensively developed for THz applications, and have been used for some astronomical observations in the last decade. In particular, the THz HEB mixers for the HIFI receiver onboard the Herschel Space Telescope have provided many innovative results for astrophysical and astrochemical studies.…”

Section: Introductionmentioning

confidence: 99%

Low-noise 1.5 THz waveguide-type hot-electron bolometer mixers using relatively thick NbTiN superconducting film

Shiino¹,

Furuya²,

Soma³

et al. 2015

Jpn. J. Appl. Phys.

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We have developed waveguide-type low-noise superconducting hot-electron bolometer (HEB) mixers for astronomical observations in the 1.3–1.5 THz region by using a relatively thick NbTiN superconducting film (10.8 nm). We have achieved a receiver noise temperature of 490 K (DSB: double side band) at 1.475 THz. This noise temperature corresponds to seven times the quantum noise. According to gain bandwidth measurements, the contribution of diffusion cooling is found to be responsible for such a good noise performance.

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SIS and bolometer mixers for terahertz frequencies

Cited by 16 publications

References 97 publications

Improvement of the critical temperature of superconducting NbTiN and NbN thin films using the AlN buffer layer

Improvement of the critical temperature of superconducting NbTiN and NbN thin films using the AlN buffer layer

Vortex-glass transition and vortex pinning behavior in three-dimensional NbTiN epitaxial films

Low-noise 1.5 THz waveguide-type hot-electron bolometer mixers using relatively thick NbTiN superconducting film

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