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IMPROVEMENT OF AKARI NEP-DEEP 2-24 MICRON IMAGES/CATALOGUES WITH NEW CALIBRATIONS
Murata, Kazumi,Matsuhara, Hideo,Takagi, Toshinobu,Wada, Takehiko,Oyabu, Shinki,Oi, Nagisa The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
We have created new catalogues of AKARI/IRC $2-24{\mu}m$ North Ecliptic Pole Deep survey through new methods of image analysis. In the new catalogues the number of false detection decreased by a factor of 10 and the number of objects detected in multiple bands increased by more than 1,500 compared to the previous work. In this proceedings the new methods of image analysis and the performance of the new catalogues are described.
Optical – near-infrared catalog for the AKARI north ecliptic pole Deep field
Oi, Nagisa,Matsuhara, Hideo,Murata, Kazumi,Goto, Tomotsugu,Wada, Takehiko,Takagi, Toshinobu,Ohyama, Youichi,Malkan, Matthew,Im, Myungshin,Shim, Hyunjin,Serjeant, Stephen,Pearson, Chris Springer-Verlag 2014 Astronomy and astrophysics Vol.566 No.-
Park, Chan-Hyuck,Pan, Han,Ishikawa, Yasuhiko,Wada, Kazumi,Ahn, Donghwan Elsevier 2018 THIN SOLID FILMS - Vol.662 No.-
<P><B>Abstract</B></P> <P>We report an ex-situ phosphorus diffusion doping for germanium integrated photonic devices on silicon chip. Here, phosphorus oxychloride (POCl<SUB>3</SUB>)-based phosphosilicate glass is chosen for n-type diffusion. As an alternative process to the in-situ P doping during Ge epitaxy so far reported for Ge laser prototyping, the presented external P-diffusion method demonstrates photoluminescence (PL) emission enhancement of Ge-on-Si. The PL enhancement, along with the P secondary ion mass spectroscopy profile in Ge, clearly indicates that our ex-situ diffusion method to form n-type Ge has a significant potential for Ge active device fabrication as an enabling technology. It should be also noted that PL quenching is observed at high temperature diffusion processes which is induced by intermixing at the Ge and Si interface. The presented ex-situ P-diffusion process can serve as a template to monolithically integrate Ge devices such as not only light sources but modulators and photodetectors on Si complementary metal-oxde-semiconductor platform, as it may tailor device-specific pn junctions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An ex-situ P diffusion to Ge epilayer on Si using POCl<SUB>3</SUB>-PSG is proposed. </LI> <LI> P diffusion enhanced photoluminescence (PL) emission of Ge film on Si. </LI> <LI> In contrast, PL is quenched after above-800 °C processes due to Si-Ge intermixing. </LI> <LI> Anomalously fast P diffusion through Si capping layer on Ge is observed. </LI> </UL> </P>
High concentration phosphorus doping in Ge for CMOS-integrated laser applications
Park, Chan-Hyuck,Yako, Motoki,Wada, Kazumi,Ishikawa, Yasuhiko,Ahn, Donghwan Elsevier 2019 Solid-state electronics Vol.154 No.-
<P><B>Abstract</B></P> <P>Germanium is a promising material for the laser that can be monolithically integrated on Si complementary metal-oxide-semiconductor platform and has emission wavelength of 1550 nm for optical interconnect. To obtain significant optical gain, it is necessary to achieve high n-type doping concentration level, while avoiding the damage to Ge crystalline quality. In this paper, we report an ex-situ phosphorus diffusion doping of Ge film, based on low-temperature phosphosilicate glass (PSG) pre-deposition process such as spin-on-glass and sub-atmospheric chemical vapor deposition (SACVD) methods. Closely related to optical gain properties of Ge for Ge-on-Si laser application, the photoluminescence characteristics of Ge epitaxial film after P diffusion doping were investigated. In particular, SACVD-processed PSG deposited directly on Ge film without any Si capping layer successfully led to high phosphorus doping concentration of ∼10<SUP>19</SUP> cm<SUP>−3</SUP> deep inside Ge and dramatically enhanced photoluminescence intensity by more than 10 times compared to intrinsic Ge film. By using the SACVD-PSG based P doping process, we developed an inverted-rib Ge waveguide structure for more effective optical gain. In the inverted-rib Ge structure, the mode will be positioned upward and stay relatively away from the Ge-Si interface where many dislocations are located and, as a result, we can expect less optical loss due to scattering and the overall higher mode gain. As a very promising preliminary result, from optical-pumping of the inverted-rib Ge, a threshold-like behavior starting at 18 kW/cm<SUP>2</SUP> and amplified spontaneous emission around 1570 nm were demonstrated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ex-situ P diffusion to Ge with phosphosilicate glass (PSG) source was investigated. </LI> <LI> Sub-atmospheric CVD (SACVD)-based PSG and spin-on-dielectric process were compared. </LI> <LI> Photoluminescence (PL) from Ge increased most, when SACVD but no Si capping used. </LI> <LI> A novel, inverted-rib Ge waveguide structure is proposed for a low-threshold laser. </LI> <LI> Light emission threshold at lower optical pumping than prior reports was observed. </LI> </UL> </P>
Introduction to the Special Issue on Silicon Photonics
Lipson, Michal,Osgood, Richard M.,Shin, Jung H.,Wada, Kazumi IEEE 2010 IEEE journal of selected topics in quantum electro Vol.16 No.1
<P>The 39 papers in this special issue focus on the field of silicon photonics.</P>
HYPER SUPRIME-CAMERA SURVEY OF THE AKARI NEP WIDE FIELD
Tomotsugu Goto,Yoshiki Toba,Yousuke Utsumi,Nagisa Oi,Toshinobu Takagi,Matt Malkan,Youichi Ohayma,Kazumi Murata,Paul Price,Marios Karouzos,Hideo Matsuhara,TAKAO NAKAGAWA,Takehiko Wada,Steve Serjeant,De 한국천문학회 2017 天文學論叢 Vol.32 No.1
The extragalactic background suggests half the energy generated by stars was reprocessed into the infrared (IR) by dust. At z$\sim$1.3, 90\% of star formation is obscured by dust. To fully understand the cosmic star formation history, it is critical to investigate infrared emission. AKARI has made deep mid-IR observation using its continuous 9-band filters in the NEP field (5.4 deg$^2$), using $\sim$10\% of the entire pointed observations available throughout its lifetime. However, there remain 11,000 AKARI infrared sources undetected with the previous CFHT/Megacam imaging ($r\sim$25.9ABmag). Redshift and IR luminosity of these sources are unknown. These sources may contribute significantly to the cosmic star-formation rate density (CSFRD). For example, if they all lie at 1$<z<$2, the CSFRD will be twice as high at the epoch. We are carrying out deep imaging of the NEP field in 5 broad bands ($g,r,i,z,$ and $y$) using Hyper Suprime-Camera (HSC), which has 1.5 deg field of view in diameter on Subaru 8m telescope. This will provide photometric redshift information, and thereby IR luminosity for the previously-undetected 11,000 faint AKARI IR sources. Combined with AKARI's mid-IR AGN/SF diagnosis, and accurate mid-IR luminosity measurement, this will allow a complete census of cosmic star-formation/AGN accretion history obscured by dust.
Su Peter,Stoll Katherine E.,Agarwal Samarth,Maksimov Oleg,Bhattacharya Pijush,Bhandari Harish B.,Wada Kazumi,Kimerling Lionel C.,Agarwal Anuradha 한국물리학회 2022 Current Applied Physics Vol.36 No.-
Oxygen sensitization and incorporation of ternary lead chalcogenide PbSe1-xTex thin films was investigated with two methods: adding oxygen via PbO to the bulk source alloy and post-deposition oxygen annealing. Characterization of the composition, structure, and morphology of these films confirmed that they follow Vegard’s law for lattice parameter, and adding PbO to the source alloy did not impact the lattice parameter. However, adding PbO changed the electrical carrier properties observed in Hall effect measurements without forming any new oxide phase. Conversely, post-deposition annealing increased the lattice parameter due to oxygen incorporation into the lattice via interstitials in samples with appropriate grain boundary orientations. Morphological analysis revealed that PbSe0.8Te0.2 films demonstrated (100) texture, while PbSe0.6Te0.4 films demonstrated (111) texture with resulting grain boundary orientations more favorable to oxygen diffusion and incorporation. This varying oxygen incorporation from PbO source and oxygen annealing methods reveals trends that can lead to improved photodetector performance.
GALAXIES ON DIET: FEEDBACK SIGNATURES IN RADIO-AGN HOST GALAXIES
Marios Karouzos,임명신,Markos Trichas,Tomogotsu Goto,Matthew Malkan,Angel Ruiz,전이슬,김지훈,이형목,김성진,Nagisa Oi,Hideo Matsuhara,Toshinobu Takagi,Kazumi Murata,Takehiko Wada,Kensuke Wada,심현진,Hitoshi Hanami,STEPH 한국천문학회 2017 天文學論叢 Vol.32 No.1
There exists strong evidence supporting the co-evolution of central supermassive black holesand their host galaxies; however it is still under debate how such a relation comes about and whether itis relevant for all or only a subset of galaxies. An important mechanism connecting AGN to their hostgalaxies is AGN feedback, potentially heating up or even expelling gas from galaxies. AGN feedbackmay hence be responsible for the eventual quenching of star formation and halting of galaxy growth. Arich multi-wavelength dataset ranging from the X-ray regime (\textit{Chandra}), to far-IR (\textit{Herschel}), and radio(\textit{WSRT}) is available for the North Ecliptic Pole field, most notably surveyed by the \textit{AKARI} infraredspace telescope, covering a total area on the sky of 5.4 sq. degrees. We investigate the star formationproperties and possible signatures of radio feedback mechanisms in the host galaxies of 237 radiosources below redshift z = 2 and at a radio 1.4 GHz flux density limit of 0.1 mJy. Using broadbandSED modelling, the nuclear and host galaxy components of these sources are studied simultaneously as a function of their radio luminosity. Here we present results concerning the AGN content of the radio sources in this field, while also offering evidence showcasing a link between AGN activity and host galaxy star formation. In particular, we show results supporting a maintenance type of feedback from powerful radio-jets.