Low-Temperature Halo-Carbon Homoepitaxial Growth of 4H-SiC: Morphology, Doping, and Role of HCl Additive

2007 ◽  
Vol 556-557 ◽  
pp. 133-136 ◽  
Author(s):  
Huang De Lin ◽  
Galyna Melnychuk ◽  
Jeffery L. Wyatt ◽  
Yaroslav Koshka
Keyword(s):  
Low Temperature ◽  
Nitrogen Concentration ◽  
Aluminum Concentration ◽  
Silicon Cluster ◽  
Vapor Species ◽  
Aluminum Doping ◽  
Homoepitaxial Growth ◽  
Order Of Magnitude

Low-temperature epitaxial growth of 4H-SiC with CH3Cl carbon precursor was further developed. In-situ doping with nitrogen and aluminum was investigated. The nitrogen concentration in epitaxial layers grown on the C face was almost two orders of magnitude higher than that in the Si-face epilayers grown in the same growth run at 13000C. The opposite trend was observed for intentional aluminum doping, with more than an order of magnitude higher aluminum concentration incorporated in Si-face epilayers. High values of nitrogen and aluminum doping well in excess of 1020 cm-3 without any obvious epilayer morphology degradation can be achieved on C-face and Siface respectively. Addition of HCl during halo-carbon growth at 13000C resulted in drastic improvement of the surface morphology. Also, a significant increase of the growth rate took place confirming that the improvement in the epilayer morphology during HCl-assisted growth is predominantly related to silicon cluster etching by additional Cl-containing vapor species.

Integrated, Dual-Function Remote Plasma-Enhanced Processing Applied to Low Damage SiO2 Etching and Removal of C-F Polymer Residues

1992 ◽  
Vol 282 ◽  
Author(s):  
T. Yasuda ◽  
G. Lucovsky
Keyword(s):  
Low Temperature ◽  
Plasma Etching ◽  
Etch Rate ◽  
Low Energy ◽  
Rf Plasma ◽  
Dual Function ◽  
Homoepitaxial Growth ◽  
Plasma Excitation ◽  
A New Technique

ABSTRACTWe report a dual-function chamber integrating (a) remote RF plasma-enhanced etching of SiO2 layers on Si(100) surfaces with low energy, <100 eV, ion bombardment and (b) in-situ removal of polymeric C-F residues that are formed on the exposed Si surfaces. Using direct plasma excitation of He and downstream introduction of CF4, an SiO2 etch rate of ̃5 nm/min was obtained at a CF4 partial pressure as low as 0.25 mTorr. An exposure to atomic-H at a substrate temperature of 250°C was effective in removing polymeric residues from the Si surface, while an exposure to reactive O-species was less effective. We achieved a low-temperature, ̃300°C, homoepitaxial growth of Si on the Si(100) surface that was subjected to plasma etching followed by an exposure to atomic-H. The electrical damage of the processed Si surfaces was evaluated by a new technique, where a device-quality SiO2 film was deposited on this surface by remote PECVD and the C-V characteristics of the MOS structure were measured.

Low-Temperature Homoepitaxial Growth of Gan Using Hyperthermal Molecular Beams

1998 ◽  
Vol 512 ◽  
Author(s):  
A. Michel ◽  
E. Chen ◽  
D. Thomson ◽  
O. Nam ◽  
R. F. Davis ◽  
...  
Keyword(s):  
Low Temperature ◽  
Thermal Desorption ◽  
Molecular Beams ◽  
Smooth Surfaces ◽  
Carbon Removal ◽  
Surface Carbon ◽  
Homoepitaxial Growth ◽  
Supersonic Molecular Beams

ABSTRACTIn situ cleaning of MOCVD-grown GaN/AlN/6H-SiC substrates using NH3-seeded supersonic molecular beams was investigated. Removal of surface carbon and oxygen contaminants was achieved by heating at 730°C under a hyperthermal NH 3 beam. Oxygen is removed primarily by thermal desorption; however, carbon removal requires an NH3 flux. Atomically smooth surfaces with regular steps are obtained after NH3 beam cleaning. Homoepitaxial growth of smooth, highly textured GaN films was accomplished at 700°C by employing a 0.61-eV NH3 beam and an effusive Ga source.

scholarly journals Revisiting australian ectocarpus subulatus (phaeophyceae) from the hopkins river: distribution, abiotic environment, and associated microbiota

2019 ◽  
Author(s):  
Simon M. Dittami ◽  
Akira F. Peters ◽  
John West ◽  
Thierry Cariou ◽  
Hetty KleinJan ◽  
...  
Keyword(s):  
Brown Algae ◽  
Laboratory Culture ◽  
Bacterial Strains ◽  
Abiotic Environment ◽  
Low Salinity ◽  
Order Of Magnitude ◽  
Original Laboratory ◽  
Surrounding Areas

AbstractEctocarpus is a genus of common marine brown algae. In 1995 a strain of Ectocarpus was isolated from Hopkins River Falls, Victoria, Australia, constituting one of few available freshwater or nearly freshwater brown algae, and the only one belonging to Ectocarpus. It has since been used as a model to study acclimation and adaptation to low salinities and the role of its microbiota in these processes. However, little is known about the distribution of this strain or whether it represents a stable population. Furthermore, its microbiota may have been impacted by the long period of cultivation.Twenty-two years after the original finding we searched for Ectocarpus in the Hopkins River and surrounding areas. We found individuals with ITS and cox1 sequences identical to the original isolate at three sites upstream of Hopkins River Falls, but none at the original isolation site. The osmolarity of the water at these sites ranged from 74-170 mOsmol, and it was rich in sulfate. The diversity of bacteria associated with the algae in situ was approximately one order of magnitude higher than in previous studies of the original laboratory culture, and 95 alga-associated bacterial strains were isolated from E. subulatus filaments on site. In particular, Planctomycetes were abundant in situ but rare in the laboratory-cultured strain.Our results confirm that E. subulatus has stably colonized the Hopkins River, and the newly isolated algal and bacterial strains offer new possibilities to study the adaptation of Ectocarpus to low salinity and its interactions with its microbiome.

scholarly journals Tools for examining subglacial bed deformation

1992 ◽  
Vol 38 (130) ◽  
pp. 388-396 ◽  
Author(s):  
Erik Blake ◽  
Garry K. C. Clarke ◽  
Marc C. Gérin
Keyword(s):  
Strain Rate ◽  
In Situ Stress ◽  
Yukon Territory ◽  
Strain Rates ◽  
Strain Measurements ◽  
Bed Deformation ◽  
Instantaneous Strain ◽  
Order Of Magnitude

AbstractDeformation beneath soft-bedded glaciers may be a physical mechanism that contributes to flow instabilities such as surging. If the role of bed deformation is to be understood, a rheological description is required, but the development of a rheology is hampered by a lack of in situ stress and strain measurements. In this paper, we describe four techniques for measuring subglacial strain. Three of these give continuous strain measurements, a capability that permits calculation of instantaneous strain rates and allows comparison of strain data with other time series. To demonstrate the practicability of the techniques, sample results from three summers of experimentation beneath Trapridge Glacier. Yukon Territory, are presented. The data show that subglacial strain rate can vary in amplitude and polarity on an hourly time-scale,and that the instantaneous strain rate can exceed the mean strain rale by an order of magnitude. Observed negative strain rates suggest extrusive flow within basal sediments.

scholarly journals Tools for examining subglacial bed deformation

1992 ◽  
Vol 38 (130) ◽  
pp. 388-396 ◽  
Author(s):  
Erik Blake ◽  
Garry K. C. Clarke ◽  
Marc C. Gérin
Keyword(s):  
Strain Rate ◽  
In Situ Stress ◽  
Yukon Territory ◽  
Strain Rates ◽  
Strain Measurements ◽  
Bed Deformation ◽  
Instantaneous Strain ◽  
Order Of Magnitude

Abstract Deformation beneath soft-bedded glaciers may be a physical mechanism that contributes to flow instabilities such as surging. If the role of bed deformation is to be understood, a rheological description is required, but the development of a rheology is hampered by a lack of in situ stress and strain measurements. In this paper, we describe four techniques for measuring subglacial strain. Three of these give continuous strain measurements, a capability that permits calculation of instantaneous strain rates and allows comparison of strain data with other time series. To demonstrate the practicability of the techniques, sample results from three summers of experimentation beneath Trapridge Glacier. Yukon Territory, are presented. The data show that subglacial strain rate can vary in amplitude and polarity on an hourly time-scale,and that the instantaneous strain rate can exceed the mean strain rale by an order of magnitude. Observed negative strain rates suggest extrusive flow within basal sediments.

scholarly journals Norpa Signalling and the Seasonal Circadian Locomotor Phenotype in Drosophila

Biology ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 130
Author(s):  
Carlo Breda ◽  
Ezio Rosato ◽  
Charalambos P. Kyriacou
Keyword(s):  
Drosophila Melanogaster ◽  
Low Temperature ◽  
Circadian Clock ◽  
Significant Role ◽  
In Situ Hybridisation ◽  
Seasonal Effects ◽  
Seasonal Adaptations ◽  
Behavioural Effects

In this paper, we review the role of the norpA-encoded phospholipase C in light and thermal entrainment of the circadian clock in Drosophila melanogaster. We extend our discussion to the role of norpA in the thermo-sensitive splicing of the per 3′ UTR, which has significant implications for seasonal adaptations of circadian behaviour. We use the norpA mutant-generated enhancement of per splicing and the corresponding advance that it produces in the morning (M) and evening (E) locomotor component to dissect out the neurons that are contributing to this norpA phenotype using GAL4/UAS. We initially confirmed, by immunocytochemistry and in situ hybridisation in adult brains, that norpA expression is mostly concentrated in the eyes, but we were unable to unequivocally reveal norpA expression in the canonical clock cells using these methods. In larval brains, we did see some evidence for co-expression of NORPA with PDF in clock neurons. Nevertheless, downregulation of norpA in clock neurons did generate behavioural advances in adults, with the eyes playing a significant role in the norpA seasonal phenotype at high temperatures, whereas the more dorsally located CRYPTOCHROME-positive clock neurons are the likely candidates for generating the norpA behavioural effects in the cold. We further show that knockdown of the related plc21C encoded phospholipase in clock neurons does not alter per splicing nor generate any of the behavioural advances seen with norpA. Our results with downregulating norpA and plc21C implicate the rhodopsins Rh2/Rh3/Rh4 in the eyes as mediating per 3′ UTR splicing at higher temperatures and indicate that the CRY-positive LNds, also known as ‘evening’ cells are likely mediating the low-temperature seasonal effects on behaviour via altering per 3′UTR splicing.

A molecularly defined cardiorespiratory interneuron expressing SDPFLRFamide/GDPFLRFamide in the snail Lymnaea: monosynaptic connections and pharmacology

1993 ◽  
Vol 69 (3) ◽  
pp. 915-927 ◽  
Author(s):  
D. R. Skingsley ◽  
K. Bright ◽  
N. Santama ◽  
J. van Minnen ◽  
M. J. Brierley ◽  
...  
Keyword(s):  
Full Range ◽  
Membrane Conductance ◽  
Excitatory Effect ◽  
Gene Encoding ◽  
Specific Expression ◽  
Giant Neuron ◽  
Order Of Magnitude ◽  
Synaptic Responses

1. Neuron-specific expression of alternately spliced exons of the gene encoding the Phe-Met-Arg-Phe-NH2 (FMRFamide) family of neuropeptides and the role of encoded peptides in synaptic transmission were examined in an identified cardiorespiratory interneuron, the visceral white interneuron (VWI), in the snail Lymnaea. 2. In situ hybridization using exon-specific probes showed VWI cytoplasmic expression of the exon encoding the Lymnaea heptapeptides Gly-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (GDPFLRF amide) Ser-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (SDPFLRF amide) but not the exon encoding the tetrapeptides FMRFamide and Phe-Leu-Arg-Phe-NH2 (FLRFamide). 3. The absence of the tetrapeptides (FMRFamide and FLRFamide) in the VWI was indirectly confirmed by the lack of immunoreactivity to a specific antibody raised against the sequence Leu-Tyr. This sequence is present in the Lymnaea tetrapeptide precursor, but not the heptapeptide precursor. 4. The VWI has monosynaptic connections with many identifiable neurons in the CNS. These were excitatory on three clusters of identified neurons [B group (Bgp), E group (Egp), and F group (Fgp)], inhibitory on another cluster [A group (Agp)] or biphasic (excitation followed by inhibition) on a single giant neuron [right pedal dorsal 1 (RPeD1)]. 5. The role of GDPFLRFamide/SDPFLRFamide as putative neurotransmitters was examined by comparing neuronally evoked postsynaptic responses with the effects of focal peptide application. 6. The heptapeptides closely mimicked the inhibitory responses (threshold pressure pipette concentration 10(-9) M) on the Agp cells and RPeD1, including an increase in membrane conductance. FMRFamide was 1 order of magnitude less potent. GDPFLRFamide/SDPFLRFamide, applied either alone or in “cocktails” (combinations of GDPFLRFamide, SDPFLRFamide, FMRFamide, and FLRFamide), did not reproduce the excitatory effect of the VWI on the Bgp, Egp, and Fgp cells. These peptides, applied either together or separately, inhibited the cells. 7. FMRFamide or FLRFamide, but not GDPFLRFamide or SDPFLRFamide, could reproduce the initial depolarizing component of the biphasic response on RPeD1. This only occurred at concentrations of > or = 10(-4) M (10(-3) M was necessary to get spikes on RPeD1) and may not be physiologically significant. 8. We conclude that at least one so far unidentified co-transmitter must be present in the VWI to account for its full range of synaptic responses.

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