Effects of long-term open-air exposure to fluoride, nitrogen compounds and SO

Trees ◽  
1996 ◽  
Vol 10 (3) ◽  
pp. 157 ◽  
Author(s):  
A. Wulff ◽  
Lauri Kärenlampi
Keyword(s):  
Nitrogen Compounds ◽  
Air Exposure

Device Applications of Solution Processed MIR Semiconductor Nanocrystal Thin Films

2021 ◽  
Author(s):  
◽  
Matt Cryer
Keyword(s):  
Thermal Imaging ◽  
Room Temperature ◽  
Spray Deposition ◽  
Low Cost ◽  
Semiconductor Nanocrystals ◽  
Colloidal Synthesis ◽  
Noisy Environment ◽  
Air Exposure ◽  
Solution Processed

<p>Colloidal semiconductor nanocrystals (NCs) with bandgaps less than 1 eV allow the development of mid wave infrared (MIR) sensitive detectors that exploit the benefits of colloidal materials, primarily bandgap selection and solution deposition. Additionally, the electrical behaviour of these films can be examined for characteristics that can increase the functionality of NC based detectors.  The production of devices that are designed to be competitive as ultra-low-cost, room temperature MIR detectors, operating with photonic, rather than thermal detection is detailed. The evolution of the colloidal synthesis, spray deposition methods, substrate materials and post deposition treatments used here lead to highly robust and high performing devices. These devices demonstrate a “colour” sensitivity down to 300 nm in the MIR (≈10 % of scale), with superior responsivities for this class of device, up to 0.9 AW⁻¹, and competitive specific detectivity up to 8 × 10⁹ Jones at 200 Hz and 300 K. Furthermore, these devices utilise a cheap and robust substrate material that allows operation after deformation up to 45 ° without degradation over many cycles. These devices offer a template for ultra-low-cost MIR detectors with performance that rivals microbolometers but with better measurement speed and spectral sensitivity. As such these devices showcase the key advantages of using colloidal NCs in MIR applications.  Planar and fully air processed thin film devices that demonstrate photo-induced memristive behaviour and can be used as a transistors, photode-tectors or memory devices are investigated. Following long term (60 h) air exposure, unpackaged NC films develop reliable memristive characteristics in tandem with temperature, gate and photoresponse. On/off ratios of more than 50 are achieved and the devices show long term stability, producing repeatable metrics over days of measurement. The on/off behaviour is shown to be dependent on previous charge flow and carrier density, implying memristive rather than switching behaviour. These observations are described within a long term trap filling model. This work represents an advance in the integration of NC films into electronic devices, which may lead to the development of multi-functional electronic components.  Building on the previous work the steps taken to move from a planar device, that works well in controlled conditions, to a multi-pixel sensor that can demonstrate MIR video imaging at room temperature in a noisy environment are shown. This is achieved with a 15 pixel detector that consists only of a polymer substrate and solution patterned NC pixels. This device can detect a 373 K object with the device at 298 K in a noisy environment. This performance is enabled by photogain at 5 V bias that reaches a maximum External Quantum Efficiency (EQE) of 1940 ± 290 % for a pixel with a 3.3 µm bandgap. Through the use of four separate bandgaps it is shown that “multicolour” thermal imaging systems can deliver another layer of information, on top of intensity, to the user. The behaviour of the system is examined under use and it is shown that the photoconductive device behaves as expected with regards to bias, and that trap enabled gain is sensitive to total incident flux, more than the spectral energy distribution of the target. Finally, it is shown that solution patterned QD fabrication methods can deliver electrical reproducibility between pixels that is sufficient to allow an imaging plane of multiple pixels.  The somewhat neglected tin chalcogenide semiconductor nanocrystals are investigated and inverse MIR detection at room temperature is demonstrated with planar, solution and airprocessed PbSnTe and SnTe QD devices. The detection mechanism is shown to be mediated by an interaction between MIR radiation and the vibrational stretches of adsorbed hydroxyl species at the oxdised NC surface. Devices are shown to possess mAW⁻¹ responsivity via a reduction in film conductance due to MIR radiation and, unlike classic MIR photoconductors, are unaffected by visible wavelengths. As such these devices offer the possibility of MIR thermal imaging that has an intrinsic solution to the blinding caused by higher energy light sources.  In summary, it is shown that semiconductor NCs with an all ambient fully solution processed deposition and ligand exchange procedure can be used to create simple, robust and cheap devices that are beginning to demonstrate metrics on par with current commercial thermal detector systems. It is also shown that these devices can under certain circumstances demonstrate novel behaviours that offer the prospects of enhanced or novel functionality.</p>

scholarly journals Device Applications of Solution Processed MIR Semiconductor Nanocrystal Thin Films

2021 ◽  
Author(s):  
◽  
Matt Cryer
Keyword(s):  
Thermal Imaging ◽  
Room Temperature ◽  
Spray Deposition ◽  
Low Cost ◽  
Semiconductor Nanocrystals ◽  
Colloidal Synthesis ◽  
Noisy Environment ◽  
Air Exposure ◽  
Solution Processed

<p>Colloidal semiconductor nanocrystals (NCs) with bandgaps less than 1 eV allow the development of mid wave infrared (MIR) sensitive detectors that exploit the benefits of colloidal materials, primarily bandgap selection and solution deposition. Additionally, the electrical behaviour of these films can be examined for characteristics that can increase the functionality of NC based detectors.  The production of devices that are designed to be competitive as ultra-low-cost, room temperature MIR detectors, operating with photonic, rather than thermal detection is detailed. The evolution of the colloidal synthesis, spray deposition methods, substrate materials and post deposition treatments used here lead to highly robust and high performing devices. These devices demonstrate a “colour” sensitivity down to 300 nm in the MIR (≈10 % of scale), with superior responsivities for this class of device, up to 0.9 AW⁻¹, and competitive specific detectivity up to 8 × 10⁹ Jones at 200 Hz and 300 K. Furthermore, these devices utilise a cheap and robust substrate material that allows operation after deformation up to 45 ° without degradation over many cycles. These devices offer a template for ultra-low-cost MIR detectors with performance that rivals microbolometers but with better measurement speed and spectral sensitivity. As such these devices showcase the key advantages of using colloidal NCs in MIR applications.  Planar and fully air processed thin film devices that demonstrate photo-induced memristive behaviour and can be used as a transistors, photode-tectors or memory devices are investigated. Following long term (60 h) air exposure, unpackaged NC films develop reliable memristive characteristics in tandem with temperature, gate and photoresponse. On/off ratios of more than 50 are achieved and the devices show long term stability, producing repeatable metrics over days of measurement. The on/off behaviour is shown to be dependent on previous charge flow and carrier density, implying memristive rather than switching behaviour. These observations are described within a long term trap filling model. This work represents an advance in the integration of NC films into electronic devices, which may lead to the development of multi-functional electronic components.  Building on the previous work the steps taken to move from a planar device, that works well in controlled conditions, to a multi-pixel sensor that can demonstrate MIR video imaging at room temperature in a noisy environment are shown. This is achieved with a 15 pixel detector that consists only of a polymer substrate and solution patterned NC pixels. This device can detect a 373 K object with the device at 298 K in a noisy environment. This performance is enabled by photogain at 5 V bias that reaches a maximum External Quantum Efficiency (EQE) of 1940 ± 290 % for a pixel with a 3.3 µm bandgap. Through the use of four separate bandgaps it is shown that “multicolour” thermal imaging systems can deliver another layer of information, on top of intensity, to the user. The behaviour of the system is examined under use and it is shown that the photoconductive device behaves as expected with regards to bias, and that trap enabled gain is sensitive to total incident flux, more than the spectral energy distribution of the target. Finally, it is shown that solution patterned QD fabrication methods can deliver electrical reproducibility between pixels that is sufficient to allow an imaging plane of multiple pixels.  The somewhat neglected tin chalcogenide semiconductor nanocrystals are investigated and inverse MIR detection at room temperature is demonstrated with planar, solution and airprocessed PbSnTe and SnTe QD devices. The detection mechanism is shown to be mediated by an interaction between MIR radiation and the vibrational stretches of adsorbed hydroxyl species at the oxdised NC surface. Devices are shown to possess mAW⁻¹ responsivity via a reduction in film conductance due to MIR radiation and, unlike classic MIR photoconductors, are unaffected by visible wavelengths. As such these devices offer the possibility of MIR thermal imaging that has an intrinsic solution to the blinding caused by higher energy light sources.  In summary, it is shown that semiconductor NCs with an all ambient fully solution processed deposition and ligand exchange procedure can be used to create simple, robust and cheap devices that are beginning to demonstrate metrics on par with current commercial thermal detector systems. It is also shown that these devices can under certain circumstances demonstrate novel behaviours that offer the prospects of enhanced or novel functionality.</p>

Chemical Vapor Deposition of Tin for Ulsi Applications

1996 ◽  
Vol 427 ◽  
Author(s):  
M. Eizenberg
Keyword(s):  
Thermal Decomposition ◽  
Chemical Vapor ◽  
Barrier Properties ◽  
Rf Plasma ◽  
Air Exposure ◽  
Aspect Ratios ◽  
Deposition Techniques ◽  
Post Deposition ◽  
Excellent Stability

AbstractTiN has been recognized as an excellent barrier material for W as well as Al planarization gap filling of contacts and vias. The need for conformality over extreme topography necessitates the use of CVD rather than sputtering for the deposition of TiN. In this paper we will first review the various deposition techniques of CVD TiN. Then, we will present a recently developed approach: thermal decomposition of TDMAT followed by nitrogen-based rf plasma treatments for resistivity reduction. This approach utilizes the advantages of thermal decomposition: excellent step coverage, good barrier properties, and low particle content. The resistivity reduction of the post deposition plasma treatment is followed by excellent stability upon long term air exposure. Vias and salicide contacts utilizing this unique process exhibit resistance values equivalent to those obtained when sputtered TiN is used. Conformal films as thin as 200Å can be utilized as excellent barriers for deep sub-0.5μm devices with large aspect ratios, where sputtered TiN can not be used any more.

Tribological and chemical effects of long term humid air exposure on sputter-deposited nanocomposite MoS2 coatings

Wear ◽  
2019 ◽  
Vol 432-433 ◽  
pp. 202935 ◽  
Author(s):  
Jeffrey R. Lince ◽  
Stuart H. Loewenthal ◽  
Charles S. Clark
Keyword(s):  
Humid Air ◽  
Air Exposure ◽  
Chemical Effects ◽  
Sputter Deposited

Validation of nitrogen dry deposition modelling above a mixed forest using high-frequency flux measurements

2020 ◽  
Author(s):  
Pascal Wintjen ◽  
Frederik Schrader ◽  
Martijn Schaap ◽  
Burkhard Beudert ◽  
Christian Brümmer
Keyword(s):  
Dry Deposition ◽  
High Frequency ◽  
Transport Model ◽  
Mixed Forest ◽  
Reactive Nitrogen ◽  
Nitrogen Compounds ◽  
Chemical Transport Model ◽  
Flux Measurements ◽  
Deposition Models

&lt;p&gt;Reactive nitrogen (N&lt;sub&gt;r&lt;/sub&gt;) compounds comprise essential nutrients for plants. However, a large supply of nitrogen by fertilization through atmospheric deposition may be harmful for ecosystems such as peatlands and may lead to a loss of biodiversity, soil acidification and eutrophication. In addition, nitrogen compounds may cause adverse human health impacts. Large parts of N&lt;sub&gt;r&lt;/sub&gt; emissions originate from anthropogenic activities. &amp;#160;Emission hotspots of &amp;#931;N&lt;sub&gt;r&lt;/sub&gt;, i.e. the sum of all N&lt;sub&gt;r&lt;/sub&gt; compounds, are related to crop production and livestock farming (mainly through ammonia, NH&lt;sub&gt;3&lt;/sub&gt;) and fossil fuel combustion by transport and industry (mainly through nitrogen oxides, NO&lt;sub&gt;2 &lt;/sub&gt;and NO). Such additional amount of N&lt;sub&gt;r&lt;/sub&gt; will enhance its biosphere-atmosphere exchange, affect plant health and can influence its photosynthetic capacity. Therefore, it is necessary to thoroughly estimate the nitrogen exchange between biosphere and atmosphere.&lt;/p&gt;&lt;p&gt;For measuring the nitrogen mixing ratios a converter for reactive nitrogen (TRANC: Total Reactive Atmospheric Nitrogen Converter) was used. The TRANC converts all reactive nitrogen compounds, except for nitrous oxide (N&lt;sub&gt;2&lt;/sub&gt;O), to nitric oxide (NO) and is coupled to a fast-response chemiluminescence detector (CLD). Due to a low detection limit and a response time of about 0.3s the TRANC-CLD system can be used for flux calculation based on the eddy covariance (EC) technique. Flux losses, which are related to the experimental setup, different response characteristics and the general high reactivity of most N gases and aerosols, occur in the high frequency range. We estimated damping factors of approximately 20% with an empirical cospectral approach.&lt;/p&gt;&lt;p&gt;For getting a reliable prediction of &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; fluxes through deposition models, long-term flux measurements offer the possibility to verify the nitrogen uptake capacity and to investigate exchange characteristics of &amp;#931;N&lt;sub&gt;r &lt;/sub&gt;in different ecosystems.&lt;/p&gt;&lt;p&gt;In this study, we compare modelled dry deposition fluxes using the deposition module DEPAC (DEPosition of Acidifying Compounds) within the chemical transport model LOTOS-EUROS (LOng Term Ozone Simulation &amp;#8211; EURopean Operational Smog) against &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; flux measurements of the TRANC-CLD for a remote mixed forest site with hardly any local anthropogenic emission sources. This procedure allows to determine the background load and the natural exchange characteristics of nitrogen under low atmospheric concentrations. Therefore, the broad-scale dry deposition predicted directly by LOTOS-EUROS was compared to site-specific modelling results obtained using measured meteorological input data as well as the directly measured &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; fluxes. In addition, the influence of land-use weighting in LOTOS-EUROS was examined. We further compare our results to &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; deposition estimates obtained with canopy budget techniques. Measured &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; dry deposition at the site was 4.5 kg N ha&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;, in close agreement with modelled estimates using DEPAC with measured drivers (5.2 kg N ha&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt;) and as integrated in the chemical transport model LOTOS-EUROS (5.2 kg N ha&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; to 6.9 kg N ha&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; yr&lt;sup&gt;-&lt;/sup&gt;&lt;sup&gt;1&lt;/sup&gt; depending on the weighting of land-use classes).&lt;/p&gt;&lt;p&gt;Our study is the first one presenting 2.5 years flux measurements of &amp;#931;N&lt;sub&gt;r&lt;/sub&gt; above a remote mixed forest. Further verifications of long-term flux measurements against deposition models are useful to improve them and result in better understanding of exchange processes of &amp;#931;N&lt;sub&gt;r&lt;/sub&gt;.&lt;/p&gt;

Design and performance of a free-air exposure system to study long-term effects of ozone on grasslands

2003 ◽  
Vol 37 (9-10) ◽  
pp. 1341-1350 ◽  
Author(s):  
M Volk ◽  
M Geissmann ◽  
A Blatter ◽  
F Contat ◽  
J Fuhrer
Keyword(s):  
Long Term Effects ◽  
Air Exposure ◽  
Exposure System ◽  
Free Air ◽  
And Performance
Sign in / Sign up

Export Citation Format

Share Document