Fabrication process and noise properties of antenna-coupled microbolometers based on superconducting YBCO films

Abstract

An analysis of how the detectivity and lifetime depend on the fabrication process of superconducting antenna-coupled microbolometers has been carried out. The temperature dependences of responsivity and noise equivalent power (NEP) have been estimated in terms of the thermal model. To reveal the main degradation mechanism, 1/f-noise characterization has been used. Monte-Carlo simulation of the annealing procedure of YBa 2 Cu 3 O 7 (YBCO) films for the operating ranges of frequency and temperature has shown that prevailing sources of flicker noise in superconducting microstrips are associated with transitions of oxygen atoms situated close to low-angle boundaries of the film blocks. The magnetron sputtering technique has been optimized to reduce the Hooge parameter for flicker noise to a record-breaking low value for YBCO films of about 10 −4 at 93 K. Comparative analysis of chemical, ion and laser etching techniques by low-temperature scanning electron microscopy and magneto-optics allowed the fabrication of microstrips with uniform current distribution characterized by critical current density higher than 10 6 A cm −2 at 77 K and long-time stability. The process of low-energy ion milling of YBCO films with an Ar + beam generated in a duopigatron ion source was used to reach a width resolution at the topology edge better than 0.2 µm. The antenna-coupled bolometers fabricated from the superconducting microstrips were used to register microwave radiation at a frequency of 70.3 GHz and temperature of 93 K. It is demonstrated that the developed technology makes possible the fabrication of long-lived YBCO-based antenna microbolometers with electrical NEP e = 1.5 × 10 −12 W Hz −1/2. The calculated response time of the antenna is about 30-150 ns. Further development is associated with fabrication of coupling microbolometers with immersed lens, with predicted optical detectivity D * = (4 × 10 9 −4 × 10 10) cm Hz 1/2 W −1 in the wavelength range 100-1000 µm.

Temperature dependence of the phase of the response of YBCO edge-transition bolometers: effects of superconductivity transition and thermal parameters

“…where the labels A and B on the sums indicate that all quantities in each sum correspond to phonons incident on the interface from the materials A and B sides, respectively. In equations (5) and (6), ω kj is the phonon frequency, v kj z is the component of the phonon group velocity normal to the interface, n(ω kj , T ) is the Bose-Einstein distribution function, t kj is the probability that a phonon of wave vector k and polarization j will be transmitted across the interface between materials A and B, and V is the volume. The Kapitza conductance can be calculated at low temperatures (hω D /kT 1) analytically taking into account Debye phonon density of states, which can be obtained from…”

“…Since the discovery of high-temperature superconductors, many works have been focused on the application of these materials in different types of bolometers for the near and far infrared wavelength regime [1][2][3][4][5][6]. The physical principle operation of the edge-transition bolometers is based upon the steep drop in their resistance, R, at critical temperature T c .…”

Design and Simulation of an Antenna-Coupled Microbolometer at 30 THz

“…They have been used in astronomical instruments with great success in both ground-based and space-borne telescopes [7][8][9] by using complex and expensive cooling systems that can achieve temperatures between 0.1 K and 0.3 K during their operation. Recent studies [10] demonstrate that bolometers can also be performed at higher temperatures, for example, at 39 K, whose application can be focused towards studies of cold planetary objects in the solar system, and up to temperatures of 93 K for detection of microwave radiation [11], whereas most of civilian applications such as security or defense require uncooled bolometers operating at environment temperatures that can be integrated in compact systems since they must be suitable for mobility [12][13][14].…”