SiGe/Si Multi-Quantum-Well Micro-Bolometer Array Design and Fabrication with Heterogeneous Integration

The micro-bolometer is important in the field of infrared imaging, although improvements in its performance have been limited by traditional materials. SiGe/Si multi-quantum-well materials (SiGe/Si MQWs) are novelty thermal-sensitive materials with a significantly high TCR and a comparably low 1/f noise. The application of such high-performance monocrystalline films in a micro-bolometer has been limited by film integration technology. This paper reports a SiGe/Si MQWs micro-bolometer fabrication with heterogeneous integration. The integration with the SiGe/Si MQWs handle wafer and dummy read-out circuit wafer was achieved based on adhesive wafer bonding. The SiGe/Si MQWs infrared-absorption structure and thermal bridge were calculated and designed. The SiGe/Si MQWs wafer and a 320 × 240 micro-bolometer array of 40 µm pitch L-type pixels were fabricated. The test results for the average absorption efficiency were more than 90% at the wavelength of 8–14 µm. The test pixel was measured to have a thermal capacity of 1.043 × 10−9 J/K, a thermal conductivity of 1.645 × 10−7 W/K, and a thermal time constant of 7.25 ms. Furthermore, the total TCR value of the text pixel was measured as 2.91%/K with a bias voltage of 0.3 V. The SiGe/Si MQWs micro-bolometer can be widely applied in commercial fields, especially in early medical diagnosis and biological detection.

G133.50+9.01: a likely cloud–cloud collision complex triggering the formation of filaments, cores, and a stellar cluster

ABSTRACT We present compelling observational evidence of G133.50+9.01 being a bona fide cloud–cloud collision candidate with signatures of induced filament, core, and cluster formation. The CO molecular line observations reveal that the G133.50+9.01 complex is made of two colliding molecular clouds with systemic velocities, $\rm -16.9$ and $\rm -14.1\, km\, s^{-1}$. The intersection of the clouds is characterized by broad bridging features characteristic of collision. The morphology of the shocked layer at the interaction front resembles an arc-like structure with enhanced excitation temperature and H2 column density. A complex network of filaments is detected in the Submillimeter Common-User Bolometer Array 2 850 $\rm \mu m$ image with 14 embedded dense cores, all well correlated spatially with the shocked layer. A stellar cluster revealed through an overdensity of identified Classes I and II young stellar objects is found located along the arc in the intersection region corroborating with a likely collision induced origin.

A Compact Micro-Bolometer Array for Mid-Infrared Laser Beam Alignment, Diagnostics and Spot-Size Measurement

Knowledge of a lasers beam’s profile throughout a laser system and experiment can help immensely in diagnosing laser problems and assisting in beam alignment and focusing at a sample. Obtaining such profiles is a trivial task in the ultraviolet-visible wavelength range but more challenging with near-infrared to infrared beams. Scientific grade bolometer arrays, suitable for such a task, do exist but are extremely costly, relatively large and have a large pixel size, of the order of 80 μm, which is adequate for profiling larger beams but poses an issue when trying to profile sub 100 μm beams for example at a focal point. This communication identifies a micro-bolometer array for near- to mid-infrared laser beam profiling, which is extremely low cost. In addition, the device is very compact, enabling use in confined spaces, and has a small, 12 μm, pixel size permitting the profiling of focused laser beams. The best scientific grade device identified has a pixel size of 17 μm. This device is a powerful tool for infrared laser spectroscopists, reducing the time required to measure the spot size of beams and to achieve spatial overlap of multiple infrared beams as used in two-dimensional infrared spectroscopy, saving many hours of setup time. The use of the bolometer array as a spectrographic detector and probe of long-term beam drifts is also demonstrated.

Two sub-millimetre bright protoclusters bounding the epoch of peak star-formation activity

ABSTRACT We present James Clerk Maxwell Telescope Submillimetre Common-User Bolometer Array 2 (SCUBA-2) 850 and 450 $\mu$m observations (σ850 ∼ 0.5 mJy, σ450 ∼ 5 mJy) of the HS1549+19 and HS1700+64 survey fields containing two of the largest known galaxy overdensities at z = 2.85 and 2.30, respectively. We detect 56 sub-millimetre galaxies (SMGs) with SNR > 4 over ∼50 arcmin2 at 850 $\mu$m with flux densities of 3–17 mJy. The number counts indicate overdensities in the 3-arcmin diameter core region (∼1.5 Mpc at z = 2.5) of $6^{+4}_{-2}\times$ (HS1549) and $4^{+6}_{-2}\times$ (HS1700) compared to blank field surveys. Within these core regions, we spectroscopically confirm that approximately one-third of the SMGs lie at the protocluster redshifts for both HS1549 and HS1700. We use statistical identifications of other SMGs in the wider fields to constrain an additional four candidate protocluster members in each system. We combine multiwavelength estimates of the star-formation rates (SFRs) from Lyman-break dropout- and narrow-band-selected galaxies, and the SCUBA-2 SMGs, to estimate total SFRs of 12 500 ± 2800 M⊙ yr−1 (4900 ± 1200 M⊙ yr−1) in HS1549 (HS1700), and SFR densities (SFRDs) within the central 1.5-Mpc diameter of each protocluster to be 3000 ± 900 M⊙ yr−1 Mpc−3 (1300 ± 400 M⊙ yr−1 Mpc−3) in the HS1549 (HS1700) protocluster, ∼104 × larger than the global SFRDs found at their respective epochs, due to the concentration of star-forming galaxies in the small volume of the dense cluster cores. Our results suggest centrally concentrated starbursts within protoclusters may be a relatively common scenario for the build-up of mass in rich clusters assembling at z ≳ 2.

Bok globule CB 17: polarization, extinction and distance

In this article, the results obtained from a polarimetric study of Bok globule CB 17 in both optical and submillimetre wavelengths are presented. Optical polarimetric observations in the R band (λ = 630 nm, Δλ = 120 nm) were conducted with the 1.04-m Sampurnanand Telescope, Aryabhatta Research Institute of observational sciencES (ARIES), in Nainital, India on 2016 March 9, while submillimetre polarimetric data are taken from the Submillimetre Common-User bolometer array POLarimeter (SCUPOL) data archive, which has been reanalysed. The contours of Herschel1 Spectral and Photometric Imaging Receiver (SPIRE) 500-μm dust continuum emission of CB 17 (typically a cometary-shaped globule) are overlaid on the Digital Sky Survey (DSS) image of CB 17 along with polarization vectors (optical and submm). The magnetic field strength at the core of the globule is estimated to be 99 μG. Using near-infrared photometric technique and Gaia data, the distance to CB 17 is found to be 253 ± 43 pc. The correlation between the various quantities of the globule is also studied. It is observed that the magnetic field in the cloud core as revealed by polarization measurements of the submillimetre dust emission is found to be almost aligned along the minor axis of the globule, which fits the magnetically regulated star formation model. A misalignment between core-scale magnetic field direction and molecular outflow direction is also found.