Self-assembled indium phosphide nanowires

This thesis deals with the self-assembled vapor-liquid-solid (VLS) growth and properties of InP nanowires, concentrating mainly on the novel catalyst-free growth of InP nanowires using in situ deposited indium droplets as seeds in metalorganic vapor phase epitaxy. The fabricated nanowires were characterized using scanning and transmission electron microscopy and continous-wave and time-resolved photoluminescence spectroscopy. All demonstrated nanowires have potential applications in nanophotonics and electronics. Epitaxial catalyst-free VLS growth of InP nanowires on (111)B InP substrates was demonstrated. The resulting distribution of vertical, freely standing nanowires is fairly homogeneous at an areal density of 109–1010 cm−2. An indium droplet without phosphorus at the nanowire tip indicates VLS growth. The average nanowire diameter (20–40 nm) and length (250–550 nm) as well as tapering can be controlled by adjusting the growth parameters. The same growth method was also shown to work to some extent for nanowire growth on silicon. The growth of ternary InAsP nanowires was briefly examined. The growth direction investigations included nanowire fabrication also on (111)A, (110), and (001) InP substrates. Electron microscopy analyses showed that the nanowire axis is parallel to 〈111〉B on all studied substrate orientations. The crystalline structure is mainly zinc-blende with a large number of twin stacking faults per unit length. Homoepitaxial catalyst-free-grown InP nanowires exhibit room temperature photoluminescence at 1.38 eV, blue shifted by about 30 meV from the band gap energy of cubic InP. Due to the large surface-to-volume ratio of the nanowires, the internal quantum efficiency for radiative carrier recombination is highly sensitive to surface conditions. The nanowires were passivated by hydrofluoric acid treatment which results in a 100-fold increase in the photoluminescence intensity, enabling the measurement of carrier recombination dynamics by means of time-resolved photoluminescence measurements. Double-exponential decay was observed, suggesting surface-related recombination processes. Finally, growth of InP nanowires using gold nanoparticle catalysts was studied. The photoluminescence and x-ray diffraction results suggest that the nanowires can crystallize in both cubic and hexagonal phases, depending on the growth temperature.Väitöskirja käsittelee InP-nanolankojen itseorganisoituvaa kasvua vapor-liquid-solid-menetelmällä (VLS). Tutkimus keskittyy uuteen katalyytittömään VLS-menetelmään, jossa alustakiteen pintaan muodostetaan indiumpisaroita organometallista kaasufaasiepitaksialaitteistoa käyttäen ilman muita prosessivaiheita. Nanolankojen karakterisointi tapahtuu pyyhkäisy- ja läpäisyelektronimikroskopian sekä jatkuvatoimisen ja ajasta riippuvan fotoluminesenssispektroskopian avulla. Tutkituilla nanolangoilla on potentiaalisia käyttökohteita nanofotoniikan ja -elektroniikan sovelluksissa. Työssä valmistettiin epitaksiaalisia InP-nanolankoja (111)B InP -alustakiteille katalyytitöntä VLS-menetelmää käyttäen. Valmistettujen homogeenisten ja pystysuorien nanolankojen pintatiheys on 109-1010 cm-2. Nanolankojen halkaisija (20-40 nm), pituus (250-550 nm) ja muoto on säädettävissä kasvatusparametrien avulla. Samalla menetelmällä valmistettiin myös In(As)P-nanolankoja piialustakiteen päälle. Nanolankojen kasvua tutkittiin myös (111)A, (110) ja (001) InP -alustakiteille. Kasvusuunnaksi havaittiin 〈111〉B alustakiteen orientaatiosta riippumatta. Nanolangat kiteyvät pääosin sinkkivälkehilaan, jossa havaitaan suuri määrä pinousvirheitä. Homoepitaksiaaliset katalyytittömällä VLS-menetelmällä valmistetut InP-nanolangat luminoivat huoneenlämpötilassa suoritetuissa fotoluminesenssimittauksissa energialla 1,38 eV, noin 30 meV kuutiollisen indiumfosfidin kiellettyä energiaväliä suuremmalla energialla. Nanolangan pinta-ala on suuri suhteessa sen tilavuuteen. Tämän takia pinnalla on suuri merkitys säteilevän rekombinaation hyötysuhteeseen. Fluorivetyhappokäsittely passivoi nanolankojen pintatilat, mikä nähtiin fotoluminesenssi-intensiteetin satakertaistumisena ja mikä mahdollisti rekombinaatiodynamiikan tutkimisen ajasta riippuvilla fotoluminesenssimittauksilla. Kaksoiseksponentiaalinen fotoluminesenssisignaalin vaimeneminen osoittaa pintatilojen edelleen vaikuttavan nanolankojen optisiin ominaisuuksiin. Työssä tutkittiin InP-nanolankojen valmistusta VLS-menetelmällä myös kultananopartikkelikatalyytein. Fotoluminesenssi- ja röntgendiffraktiotulosten perusteella nanolangat voivat kiteytyä kuutiolliseen tai heksagonaaliseen hilaan kasvatuslämpötilasta riippuen.reviewe

Imaging the circumstellar envelopes of AGB stars

We report the results of an exploratory program to image the extended circumstellar envelopes of asymptotic giant branch (AGB) stars in dust-scattered galactic light. The goal is to characterize the morphology of the envelopes as a probe of the mass-loss process. The observations consist of short exposures with the VLT and longer exposures with 1-2m telescopes, augmented with archival images from the Hubble Space Telescope. We observed 12 AGB stars and detected the circumstellar envelopes in 7. The detected envelopes have mass loss rates more than about 5 10E-6 solar mass per year, and they can be seen out to distances of about 1 kpc. The observations provide information on the mass loss history on time scales up to about 10,000 years. For the five AGB envelopes in which the circumstellar geometry is well determined by scattered light observations, all except one (OH348.2-19.7) show deviations from spherical symmetry. Two (IRC+10216 and IRC+10011) show roughly spherical envelopes at large radii but asymmetry or bipolarity close to the star; one (AFGL 2514) shows an extended, elliptical envelope, and one (AFGL 3068) shows a spiral pattern. The non-spherical structures are all consistent with the effects of binary interactions. Our observations are in accord with a scenario in which binary companions play a role in shaping planetary nebulae, and show that the circumstellar gas is already partly shaped on the AGB, before evolution to the proto-planetary nebula phase.Comment: Accepted by AA 21 Feb 2006; 18 pages, 14 figs; for high resolution images, contact mauron at graal.univ-montp2.f

MITS: the Multi-Imaging Transient Spectrograph for SOXS

The Son Of X-Shooter (SOXS) is a medium resolution spectrograph R~4500 proposed for the ESO 3.6 m NTT. We present the optical design of the UV-VIS arm of SOXS which employs high efficiency ion-etched gratings used in first order (m=1) as the main dispersers. The spectral band is split into four channels which are directed to individual gratings, and imaged simultaneously by a single three-element catadioptric camera. The expected throughput of our design is >60% including contingency. The SOXS collaboration expects first light in early 2021. This paper is one of several papers presented in these proceedings describing the full SOXS instrument

Optical design of the SOXS spectrograph for ESO NTT

An overview of the optical design for the SOXS spectrograph is presented. SOXS (Son Of X-Shooter) is the new wideband, medium resolution (R>4500) spectrograph for the ESO 3.58m NTT telescope expected to start observations in 2021 at La Silla. The spectroscopic capabilities of SOXS are assured by two different arms. The UV-VIS (350-850 nm) arm is based on a novel concept that adopts the use of 4 ion-etched high efficiency transmission gratings. The NIR (800- 2000 nm) arm adopts the '4C' design (Collimator Correction of Camera Chromatism) successfully applied in X-Shooter. Other optical sub-systems are the imaging Acquisition Camera, the Calibration Unit and a pre-slit Common Path. We describe the optical design of the five sub-systems and report their performance in terms of spectral format, throughput and optical quality. This work is part of a series of contributions describing the SOXS design and properties as it is about to face the Final Design Review.Comment: 9 pages, 9 figures, published in SPIE Proceedings 1070

The VIS detector system of SOXS

SOXS will be a unique spectroscopic facility for the ESO NTT telescope able to cover the optical and NIR bands thanks to two different arms: the UV-VIS (350-850 nm), and the NIR (800-1800 nm). In this article, we describe the design of the visible camera cryostat and the architecture of the acquisition system. The UV-VIS detector system is based on a e2v CCD 44-82, a custom detector head coupled with the ESO continuous ow cryostats (CFC) cooling system and the NGC CCD controller developed by ESO. This paper outlines the status of the system and describes the design of the different parts that made up the UV-VIS arm and is accompanied by a series of contributions describing the SOXS design solutions.Comment: 9 pages, 13 figures, to be published in SPIE Proceedings 1070

The Acquisition Camera System for SOXS at NTT

SOXS (Son of X-Shooter) will be the new medium resolution (R$\sim$4500 for a 1 arcsec slit), high-efficiency, wide band spectrograph for the ESO-NTT telescope on La Silla. It will be able to cover simultaneously optical and NIR bands (350-2000nm) using two different arms and a pre-slit Common Path feeding system. SOXS will provide an unique facility to follow up any kind of transient event with the best possible response time in addition to high efficiency and availability. Furthermore, a Calibration Unit and an Acquisition Camera System with all the necessary relay optics will be connected to the Common Path sub-system. The Acquisition Camera, working in optical regime, will be primarily focused on target acquisition and secondary guiding, but will also provide an imaging mode for scientific photometry. In this work we give an overview of the Acquisition Camera System for SOXS with all the different functionalities. The optical and mechanical design of the system are also presented together with the preliminary performances in terms of optical quality, throughput, magnitude limits and photometric properties.Comment: 9 pages, 7 figures, SPIE conferenc

Broadband laser polarization control with aligned carbon nanotubes

We introduce a simple approach to fabricate aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic property is confirmed with optical and scanning electron microscopy, and with polarized Raman and absorption spectroscopy. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 um) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as material processing, polarization diversity detection in communications), where the linear polarization control is necessary.Comment: 5 pages, 6 figure

Status of the PSF Reconstruction Work Package for MICADO ELT

MICADO is a workhorse instrument for the ESO ELT, allowing first light capability for diffraction limited imaging and long-slit spectroscopy at near-infrared wavelengths. The PSF Reconstruction (PSF-R) Team of MICADO is currently implementing, for the first time within all ESO telescopes, a software service devoted to the blind reconstruction of the PSF. This tool will work independently of the science data, using adaptive optics telemetry data, both for Single Conjugate (SCAO) and Multi-Conjugate Adaptive Optics (MCAO) allowed by the MORFEO module. The PSF-R service will support the state-of-the-art post-processing scientific analysis of the MICADO imaging and spectroscopic data. We provide here an update of the status of the PSF-R service tool of MICADO, after successfully fulfilling the Final Design Review phase, and discuss recent results obtained on simulated and real data gathered on instruments similar to MICADO.Comment: to appear in the Proceedings 12185-149 of the SPIE conference Adaptive Optics Systems VIII, Astronomical Telescopes+Instrumentation 2022 Montreal, Quebec, Canada; 6 pages, 1 figure, 1 table; updated affiliation

Management of Urban Waters with Nature-Based Solutions in Circular Cities—Exemplified through Seven Urban Circularity Challenges

Nature-Based Solutions (NBS) have been proven to effectively mitigate and solve resource depletion and climate-related challenges in urban areas. The COST (Cooperation in Science and Technology) Action CA17133 entitled “Implementing nature-based solutions (NBS) for building a resourceful circular city” has established seven urban circularity challenges (UCC) that can be addressed effectively with NBS. This paper presents the outcomes of five elucidation workshops with more than 20 European experts from different backgrounds. These international workshops were used to examine the effectiveness of NBS to address UCC and foster NBS implementation towards circular urban water management. A major outcome was the identification of the two most relevant challenges for water resources in urban areas: ‘Restoring and maintaining the water cycle’ (UCC1) and ‘Water and waste treatment, recovery, and reuse’ (UCC2). s Moreover, significant synergies with ‘Nutrient recovery and reuse’, ‘Material recovery and reuse’, ‘Food and biomass production’, ‘Energy efficiency and recovery’, and ‘Building system recovery’ were identified. Additionally, the paper presents real-life case studies to demonstrate how different NBS and supporting units can contribute to the UCC. Finally, a case-based semi-quantitative assessment of the presented NBS was performed. Most notably, this paper identifies the most typically employed NBS that enable processes for UCC1 and UCC2. While current consensus is well established by experts in individual NBS, we presently highlight the potential to address UCC by combining different NBS and synergize enabling processes. This study presents a new paradigm and aims to enhance awareness on the ability of NBS to solve multiple urban circularity issues.publishedVersio

Проект системы теплоснабжения рабочего цеха АО "КМЗ" г. Кемерово

Объектом исследования является рабочий цех АО «КМЗ». Цель работы – разработка системы теплоснабжения цеха с подбором отопительного оборудования. Температурный график – 90/70 оС. В процессе исследования проводилось изучении ограждающих конструкций здания, климатические характеристики района строительства. В результате исследования был произведен теплотехнический расчет ограждающих конструкций, расчет тепловых потерь для цеха. На основании произведенных расчетов разработан план и аксонометрическая схема системы отопления, проведен тепловой расчет отопительный приборов и гидравлический расчет системы отопления. Произведен подбор отопительного оборудования, расчет теплового баланса котельного агрегата.The object of the research is the working plant of JSC "KMZ". The work purpose – development of system of a heat supply plant with the selection of heating equipment. Temperature chart – 90/70 operating system. In the process the study was conducted the study of the building envelope, climatic characteristics of the construction area. The study was produced by the thermal design of building envelopes, heat loss calculation for the shop. On the basis of the calculations developed a plan and axonometric scheme of the heating system carried out thermal design of heaters and hydraulic calculation of the heating system. Promoted the selection of heating equipment, the calculation of the heat balance boiler unit