scholarly journals Preparative-scale synthesis of nonacene

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Andrej Jančařík ◽  
Jan Holec ◽  
Yuuya Nagata ◽  
Michal Šámal ◽  
Andre Gourdon
Keyword(s):  
Low Temperatures ◽  
High Vacuum ◽  
Bulk Phase ◽  
Ultra High Vacuum ◽  
Time Stability ◽  
Preparative Scale ◽  
Formidable Challenge ◽  
Solid Matrices

AbstractDuring the last years we have witnessed progressive evolution of preparation of acenes with length up to dodecacene by on-surface synthesis in ultra-high vacuum or generation of acenes up to decacene in solid matrices at low temperatures. While these protocols with very specific conditions produce the acenes in amount of few molecules, the strategies leading to the acenes in large quantities dawdle behind. Only recently and after 70 years of synthetic attempts, heptacene has been prepared in bulk phase. However, the preparative scale synthesis of higher homologues still remains a formidable challenge. Here we report the preparation and characterisation of nonacene and show its excellent thermal and in-time stability.

scholarly journals Preparative-Scale Synthesis of Nonacene

2021 ◽  
Author(s):  
Andrej Jancarik ◽  
Jan Holec ◽  
Yuuya Nagata ◽  
Michal Šámal ◽  
Andre Gourdon
Keyword(s):  
Low Temperatures ◽  
Bulk Phase ◽  
Time Stability ◽  
Preparative Scale ◽  
Formidable Challenge ◽  
Solid Matrices

<p>During the last years we have witnessed progressive evolution of preparation of acenes with length up to dodecacene by on-surface synthesis in UHV or generation of acenes up to decacene in solid matrices at low temperatures. While these protocols with very specific conditions produce the acenes in amount of few molecules, the strategies leading to the acenes in large quantities dawdle behind. Only recently and after 70 years of synthetic attempts, heptacene has been prepared in bulk phase. However, the preparative scale synthesis of higher homologues still remains a formidable challenge. Here we report the preparation and characterisation of nonacene and show its excellent thermal and in-time stability. </p>

scholarly journals Preparative-Scale Synthesis of Nonacene

2021 ◽  
Author(s):  
Andrej Jancarik ◽  
Jan Holec ◽  
Yuuya Nagata ◽  
Michal Šámal ◽  
Andre Gourdon
Keyword(s):  
Low Temperatures ◽  
Bulk Phase ◽  
Time Stability ◽  
Preparative Scale ◽  
Formidable Challenge ◽  
Solid Matrices

<p>During the last years we have witnessed progressive evolution of preparation of acenes with length up to dodecacene by on-surface synthesis in UHV or generation of acenes up to decacene in solid matrices at low temperatures. While these protocols with very specific conditions produce the acenes in amount of few molecules, the strategies leading to the acenes in large quantities dawdle behind. Only recently and after 70 years of synthetic attempts, heptacene has been prepared in bulk phase. However, the preparative scale synthesis of higher homologues still remains a formidable challenge. Here we report the preparation and characterisation of nonacene and show its excellent thermal and in-time stability. </p>

Silicon epitaxy using tetrasilane at low temperatures in ultra-high vacuum chemical vapor deposition

2016 ◽  
Vol 444 ◽  
pp. 21-27 ◽  
Author(s):  
Ramsey Hazbun ◽  
John Hart ◽  
Ryan Hickey ◽  
Ayana Ghosh ◽  
Nalin Fernando ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Low Temperatures ◽  
High Vacuum ◽  
Chemical Vapor ◽  
Ultra High Vacuum ◽  
Silicon Epitaxy

An ultra high vacuum system for thin dielectric film deposition at low temperatures

1988 ◽  
Vol 3 (5) ◽  
pp. 951-957
Author(s):  
R. P. H. Chang ◽  
G. Griffiths
Keyword(s):  
Low Temperatures ◽  
High Vacuum ◽  
Oxide Films ◽  
Film Deposition ◽  
Ultra High Vacuum ◽  
Oxide Semiconductor ◽  
Vacuum System ◽  
Phosphorus Oxide ◽  
Electrical Measurements ◽  
Crystal Surfaces

An ultra high vacuum system has been designed and constructed for the purpose of depositing high-quality oxide films on well-characterized crystal surfaces at low temperatures. In particular, aluminum phosphorus oxide films have been deposited on both In P and Ge surfaces for the purpose of device application. Electrical measurements of metal-oxide-semiconductor structures show much improved interfacial properties with little or no hysteresis.

scholarly journals Development of a cryogenic system for a UHV manipulator for a light detection device in a LT-STM.

2019 ◽  
Author(s):  
Ronaldo Rodrigues Fernandes Vieira ◽  
Luiz Fernando Zagonel ◽  
Yves Maia Auad
Keyword(s):  
Low Temperature ◽  
Scanning Tunneling Microscope ◽  
Low Temperatures ◽  
Thermal Instability ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Cryogenic System ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Temperature Scanning

This project aims to develop a cryogenic system for a UHV (Ultra-High Vacuum) manipulator that is currently under development in our group and that will be installed inside a low temperature scanning tunneling microscope (LT-STM). This advice will be used as a light detector to collect the Luminescence in the STM scan, and since the equipment will operate in low temperatures, it is necessary that this advice also operate in low temperatures so that it won't cause thermal instability which would prefent image acquisition due to thermal drifts.

scholarly journals Photodesorption of ices – Releasing organic precursors into the gas phase

2008 ◽  
Vol 4 (S251) ◽  
pp. 449-450 ◽  
Author(s):  
Karin I. Öberg ◽  
Ewine F. van Dishoeck ◽  
Harold Linnartz
Keyword(s):  
Gas Phase ◽  
Low Temperatures ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electronic Transitions ◽  
Interstellar Chemistry ◽  
Reflection Absorption Infrared Spectroscopy ◽  
Organic Precursors ◽  
Cloud Cores ◽  
Standing Problem

AbstractA long-standing problem in interstellar chemistry is how molecules can be maintained in the gas phase at the extremely low temperatures in space. Photodesorption has been suggested to explain the observed cold gas in cloud cores and disk mid-planes. We are studying the UV photodesorption of ices experimentally under ultra high vacuum and at astrochemically relevant temperatures (15 – 27 K) using a hydrogen discharge lamp (7-10.5 eV). The ice desorption during irradiation is monitored using reflection absorption infrared spectroscopy and the desorbed species using mass spectrometry. We find that both the UV photodesorption rates and mechanisms are highly molecule specific. CO photodesorbs without dissocation from the surface layer of the ice. N2, which lacks dipole allowed electronic transitions in the range of the lamp, does not photodesorb. CO2 desorbs through dissociation and subsequent recombination from the top few layers of the ice. At low temperatures (15 – 18 K) the derived photodesorption rates are ~ 10−3 for CO and CO2 and < 2 × 10−4 for N2 ice per incident photon.

Thin Pyrolytic Graphite Films for Electron Microscope Substrates

1971 ◽  
Vol 29 ◽  
pp. 226-227 ◽  
Author(s):  
George H. N. Riddle ◽  
Benjamin M. Siegel
Keyword(s):  
Vacuum Chamber ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Graphite Substrate ◽  
Nickel Substrate ◽  
Routine Procedure ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

A High Voltage Electron Microscopy Study of Sub-Oxide Formation in Vanadium

1971 ◽  
Vol 29 ◽  
pp. 212-213
Author(s):  
R. H. Geiss ◽  
R. L. Ladd ◽  
K. R. Lawless
Keyword(s):  
High Vacuum ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Ultra High Vacuum ◽  
Pure Oxygen ◽  
Pressure Oxidation ◽  
High Voltage Electron Microscopy ◽  
Oxidation Study ◽  
Voltage Electron ◽  
Good Agreement

Detailed electron microscope and diffraction studies of the sub-oxides of vanadium have been reported by Cambini and co-workers, and an oxidation study, possibly complicated by carbon and/or nitrogen, has been published by Edington and Smallman. The results reported by these different authors are not in good agreement. For this study, high purity polycrystalline vanadium samples were electrochemically thinned in a dual jet polisher using a solution of 20% H2SO4, 80% CH3OH, and then oxidized in an ion-pumped ultra-high vacuum reactor system using spectroscopically pure oxygen. Samples were oxidized at 350°C and 100μ oxygen pressure for periods of 30,60,90 and 160 minutes. Since our primary interest is in the mechanism of the low pressure oxidation process, the oxidized samples were cooled rapidly and not homogenized. The specimens were then examined in the HVEM at voltages up to 500 kV, the higher voltages being necessary to examine thick sections for which the oxidation behavior was more characteristic of the bulk.

The High Resolution Scanning Transmission Electron Microscope

1974 ◽  
Vol 32 ◽  
pp. 316-317
Author(s):  
A. V. Crewe
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Vacuum ◽  
Scanning Transmission Electron Microscope ◽  
Ultra High Vacuum ◽  
Resolving Power ◽  
Imaging Characteristics ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
The Moment

The high resolution STEM is now a fact of life. I think that we have, in the last few years, demonstrated that this instrument is capable of the same resolving power as a CEM but is sufficiently different in its imaging characteristics to offer some real advantages.It seems possible to prove in a quite general way that only a field emission source can give adequate intensity for the highest resolution^ and at the moment this means operating at ultra high vacuum levels. Our experience, however, is that neither the source nor the vacuum are difficult to manage and indeed are simpler than many other systems and substantially trouble-free.

Sign in / Sign up

Export Citation Format

Share Document