In situ ellipsometry study of atomic hydrogen etching of extreme ultraviolet induced carbon layers

2011 ◽  
Vol 258 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Juequan Chen ◽  
Eric Louis ◽  
Rob Harmsen ◽  
Tim Tsarfati ◽  
Herbert Wormeester ◽  
...  
Keyword(s):  
Atomic Hydrogen ◽  
Extreme Ultraviolet ◽  
Hydrogen Etching

Preparation and Optical Properties of Ultrathin Silicon Films

1994 ◽  
Vol 358 ◽  
Author(s):  
R. W. Collins ◽  
Hien V. Nguyen ◽  
Ilsin An ◽  
Yiwei Lu ◽  
M. Wakagi
Keyword(s):  
Vapor Deposition ◽  
Atomic Hydrogen ◽  
Quantum Confinement ◽  
Cluster Size ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Mean Free Path ◽  
Hydrogen Etching ◽  
Electron Mean Free Path

ABSTRACTUltrathin crystalline silicon (c-Si) and amorphous silicon (a-Si:H) films have been prepared using plasma-enhanced chemical vapor deposition (PECVD) and atomic hydrogen etching methods. The complex dielectric functions (2 < hv < 4.5 eV) of films consisting of isolated clusters have been measured in situ and in real time using spectroscopic ellipsometry. For 12 Å c-Si cluster films, a sharp absorption onset is observed near 3 eV that blue-shifts with decreasing thickness, in consistency with the quantum confinement of electrons. A much broader absorption onset, observed for ∼13 Å a-Si:H cluster films near 2 eV, is attributed to an electron mean free path that is less than the cluster size, which limits the appearance of confinement effects.

scholarly journals Converting copper sulfide to copper with surface sulfur for electrocatalytic alkyne semi-hydrogenation with water

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yongmeng Wu ◽  
Cuibo Liu ◽  
Changhong Wang ◽  
Yifu Yu ◽  
Yanmei Shi ◽  
...  
Keyword(s):  
Binding Energy ◽  
Noble Metal ◽  
Atomic Hydrogen ◽  
Copper Sulfide ◽  
Low Cost ◽  
Water Electrolysis ◽  
Metal Free ◽  
Copper Nanowire

AbstractElectrocatalytic alkyne semi-hydrogenation to alkenes with water as the hydrogen source using a low-cost noble-metal-free catalyst is highly desirable but challenging because of their over-hydrogenation to undesired alkanes. Here, we propose that an ideal catalyst should have the appropriate binding energy with active atomic hydrogen (H*) from water electrolysis and a weaker adsorption with an alkene, thus promoting alkyne semi-hydrogenation and avoiding over-hydrogenation. So, surface sulfur-doped and -adsorbed low-coordinated copper nanowire sponges are designedly synthesized via in situ electroreduction of copper sulfide and enable electrocatalytic alkyne semi-hydrogenation with over 99% selectivity using water as the hydrogen source, outperforming a copper counterpart without surface sulfur. Sulfur anion-hydrated cation (S2−-K+(H2O)n) networks between the surface adsorbed S2− and K+ in the KOH electrolyte boost the production of active H* from water electrolysis. And the trace doping of sulfur weakens the alkene adsorption, avoiding over-hydrogenation. Our catalyst also shows wide substrate scopes, up to 99% alkenes selectivity, good reducible groups compatibility, and easily synthesized deuterated alkenes, highlighting the promising potential of this method.

scholarly journals Measuring the frequency chirp of extreme-ultraviolet free-electron laser pulses by transient absorption spectroscopy

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Thomas Ding ◽  
Marc Rebholz ◽  
Lennart Aufleger ◽  
Maximilian Hartmann ◽  
Veit Stooß ◽  
...  
Keyword(s):  
Free Electron ◽  
Free Electron Laser ◽  
Transient Absorption ◽  
Extreme Ultraviolet ◽  
Ultrashort Pulses ◽  
Laser Pulses ◽  
Transient Absorption Spectroscopy ◽  
Energy Structure ◽  
Frequency Chirp

AbstractHigh-intensity ultrashort pulses at extreme ultraviolet (XUV) and x-ray photon energies, delivered by state-of-the-art free-electron lasers (FELs), are revolutionizing the field of ultrafast spectroscopy. For crossing the next frontiers of research, precise, reliable and practical photonic tools for the spectro-temporal characterization of the pulses are becoming steadily more important. Here, we experimentally demonstrate a technique for the direct measurement of the frequency chirp of extreme-ultraviolet free-electron laser pulses based on fundamental nonlinear optics. It is implemented in XUV-only pump-probe transient-absorption geometry and provides in-situ information on the time-energy structure of FEL pulses. Using a rate-equation model for the time-dependent absorbance changes of an ionized neon target, we show how the frequency chirp can be directly extracted and quantified from measured data. Since the method does not rely on an additional external field, we expect a widespread implementation at FELs benefiting multiple science fields by in-situ on-target measurement and optimization of FEL-pulse properties.

Fabrication of Polycrystalline Silicon on Glass from Fluorinated Precursors with the Aid of Atomic Hydrogen

1995 ◽  
Vol 403 ◽  
Author(s):  
T. Akasaka ◽  
D. He ◽  
I. Shimizu
Keyword(s):  
Thin Films ◽  
Atomic Hydrogen ◽  
Polycrystalline Silicon ◽  
In Situ Observation ◽  
Layer By Layer ◽  
High Quality ◽  
Deposition Parameters ◽  
Columnar Grains ◽  
Step Growth

AbstractHigh quality polycrystalline silicon was made on glass from fluorinated precursors by two step growth, i.e., (1) formation of seed crystals on glass by layer-by-layer(LL) technique and (2) grain-growth on the seeds. In LL technique, deposition of ultra-thin films and treatment with atomic hydrogen was repeated alternately. Columnar grains with 200 nm dia were grown epitaxy-like on the seeds by optimizing the deposition parameters under in situ observation with spectroscopic ellipsometry.

6H- AND 4H-SiC(0001) Si SURFACE RICHNESS DOSING BY HYDROGEN ETCHING: A WAY TO REDUCE THE FORMATION TEMPERATURE OF RECONSTRUCTIONS

2003 ◽  
Vol 10 (01) ◽  
pp. 55-63 ◽  
Author(s):  
M. DIANI ◽  
J. DIOURI ◽  
L. KUBLER ◽  
L. SIMON ◽  
D. AUBEL ◽  
...  
Keyword(s):  
High Temperature ◽  
Atomic Hydrogen ◽  
Room Temperature ◽  
Binary Systems ◽  
Temperature Treatment ◽  
Heating Time ◽  
High Temperature Treatment ◽  
Formation Temperature ◽  
Hydrogen Etching ◽  
Chemical Surface

In 6H- or 4H-SiC(0001) surface technology, a Si-rich 3 × 3 reconstruction is usually first prepared by heating at 800°C under Si flux, and two other most stable [Formula: see text] or [Formula: see text] reconstructions are obtained by further extensive annealing at higher temperatures ranging between 900 and 1250°C. The 3 × 3 Si excess is thus progressively depleted up to a graphitized C-rich surface. By crystallographic (LEED) and chemical surface characterizations (XPS and UPS), we show that all these reconstructions can be obtained at a unique, low formation temperature of 800°C if the Si richness is controlled before annealing. This control is achieved by exposing the 3 × 3 surface to atomic hydrogen at room temperature. This procedure allows one to etch or partially deplete the (3 × 3)-associated Si excess, and make it more comparable to the final Si coverages, required to form the less Si-rich [Formula: see text] or [Formula: see text] reconstructions. After annealing at 800°C, the latter reconstructions are no longer determined by the heating time or temperature but only by the initial Si coverage set by the H doses inducing the low temperature etching. The high temperature treatment, required to remove by sublimation a significant Si amount associated with the Si-rich 3 × 3 reconstruction, is thus avoided. Such a methodology could be applied to other binary systems in the formation of reconstructions that depends on surface richness.

An atomic hydrogen etching sensor for H2 plasma diagnostics

2021 ◽  
Vol 92 (6) ◽  
pp. 063518
Author(s):  
D. P. J. van Leuken ◽  
C. A. de Meijere ◽  
R. van der Horst ◽  
V. Y. Banine ◽  
E. A. Osorio ◽  
...  
Keyword(s):  
Plasma Diagnostics ◽  
Atomic Hydrogen ◽  
Hydrogen Etching
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