Fast In-diffusion of Hydrogen at the Initial Stage of Hydrogen Plasma Treatment on a-Si:H Films Observed by In-situ ESR Measurements

2000 ◽  
Vol 609 ◽  
Author(s):  
Ujjwal Kr. Das ◽  
Tetsuji Yasuda ◽  
Satoshi Yamasaki
Keyword(s):  
Diffusion Coefficient ◽  
Atomic Hydrogen ◽  
Hydrogen Plasma ◽  
Hydrogen Treatment ◽  
Initial Stage ◽  
Lower Treatment ◽  
Spin Resonance ◽  
High Diffusion Coefficient ◽  
Diffusion Of Hydrogen

ABSTRACTTime evolution of Si dangling bonds (dbs) was monitored during atomic hydrogen treatment of a-Si:H films using an in-situ electron-spin-resonance (ESR) technique. A high diffusion coefficient (>10−10 cm2s−1) of free atomic H in a-Si:H was detected at the very initial stage of H exposure. Atomic H diffuses into the bulk of the film (∼100 nm) and creates additional metastable dbs. The spatial distribution of such metastable dbs becomes deeper at lower treatment temperatures. An activated type of db creation reaction determines the distribution of these dbs.

Si(100) Surface Preparation by In-Situ or in-Vacuo Exposure to Remotely Plasma-Generated Atomic Hydrogen: Applications to Deposited SiO2 and Epitaxial Growth of Si

1990 ◽  
Vol 202 ◽  
Author(s):  
T. Yasuda ◽  
Y. Ma ◽  
S. Habermehl ◽  
S. S. Kim ◽  
G. Lucovsky ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
Atomic Hydrogen ◽  
Hydrogen Plasma ◽  
Surface Preparation ◽  
Surface Cleaning ◽  
Ozone Exposure ◽  
Ex Situ ◽  
Carbon Surface ◽  
Necessary Condition

ABSTRACTThis paper addresses the in-situ/in-vacuo preparation of Si (100) substrates by hydrogen plasma cleaning prior to low temperature deposition of SiO2, or epitaxial growth of Si or Ge. The paper emphasizes the effectiveness of this type of substrate surface preparation following ex-situ wet-cleaning procedures that include: i) conventional RCA cleans; ii) modified RCA cleans, which incorporate exposure of the Si substrate to ozone, O3; and iii) ozone exposure, with all of these terminated by the removal of sacrificial oxides by dilute HF. We conclude: i) all ex-situ surface cleaning of Si (100) substrates leaves behind sub-monolayer oxygen and carbon surface contamination; ii) that virtually all of the carbon can be removed by exposure of the Si surface to atomic hydrogen at a temperature of <300°C; and iii) that a necessary condition for: (a) the formation of Si/SiO2 interfaces with low defect densities, Dit<l−3×1010cm−2-eV−1, and (b) the growth of epitaxial films of Si; is that the processed Si surface exhibit a 2×1 reconstruction, as detected by LEED or RHEED, following the exposure to atomic hydrogen.

Surface Potential Measurements of doping and defects in p-GaN

2003 ◽  
Vol 798 ◽  
Author(s):  
M. Losurdo ◽  
M. M. Giangregorio ◽  
G. Bruno ◽  
A. S. Brown ◽  
W. A. Doolittle ◽  
...  
Keyword(s):  
Real Time ◽  
Surface Potential ◽  
Atomic Hydrogen ◽  
Hydrogen Plasma ◽  
Hydrogen Treatment ◽  
Kelvin Probe ◽  
Kelvin Probe Microscopy ◽  
Surface Potential Measurements ◽  
Si Doped ◽  
Kinetics Of

ABSTRACTThe interaction of Be-, Mg-, and Si- doped GaN epitaxial films with atomic hydrogen, produced by a remote r.f. hydrogen plasma, is investigated. The kinetics of the interaction is monitored in real time by spectroscopic ellipsometry through the measurement of the variation of the GaN pseudodielectric function. The passivation effect of hydrogen is inferred by surface potential measurements using scanning Kelvin probe microscopy (SKPM). It is found that the interaction of GaN with hydrogen is a strong function of both the type and level of the doping. Hydrogen treatment is shown to lead to a strong variation of the surface potential and, hence, of the Fermi level position, which is the result of p-dopant passivation by hydrogen. A different interaction of Mg and Be with atomic hydrogen is also observed and monitored in real time by ellipsometry. SKPM is also used for studying the interaction of defects in GaN with atomic hydrogen.

scholarly journals FORMATION OF LIGHT IMPURITIES IN A HYDROGEN PLASMA AT INITIAL STAGE OF A DISCHARGE

2019 ◽  
pp. 110-112
Author(s):  
V.B. Yuferov ◽  
E.I. Skibenko ◽  
V.I. Tkachov ◽  
V.V. Katrechko ◽  
A.S. Svichkar
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Hydrogen ◽  
Hydrogen Plasma ◽  
Hydrogen Ions ◽  
Hydrogen Atoms ◽  
Impurity Atoms ◽  
Radiation Fluxes ◽  
Start Up ◽  
Initial Stage ◽  
Light Impurities

Analyzing the dynamics of density for atomic and molecular hydrogen ions, the values of atomic hydrogen and UV radiation fluxes to the walls of the plasma chamber were obtained, resulting in light impurities of carbon and oxygen at plasma start-up during the process of desorption from the walls under irradiation. The fluxes of impurity atoms associated with the fluxes of photons and hydrogen atoms in a discharge are determined. Recommendations are given to reduce the amount of impurities at the initial stage of discharge.

Real-Time ESR Observation During Film Growth of a-Si:H

1997 ◽  
Vol 467 ◽  
Author(s):  
S. Yamasaki ◽  
T. Umeda ◽  
J. Isoya ◽  
K. Tanaka
Keyword(s):  
Gas Phase ◽  
Film Growth ◽  
Hydrogen Plasma ◽  
Bulk Region ◽  
Dangling Bond ◽  
Dynamic Changes ◽  
Spin Resonance ◽  
Higher Spin ◽  
Hydrogenated Amorphous

ABSTRACTIn-situ electron-spin-resonance (ESR) measurements of film growth of hydrogenated amorphous silicon (a-Si:H) using a remote hydrogen plasma technique have been performed. The Si dangling-bond signal in a-Si:H during and after deposition has been detected, in addition to the gas-phase ESR signals both of atomic hydrogen and photo-excited SiHx molecules. Dynamic changes of the Si dangling-bond signal intensity were observed when the deposition started and stopped, which has suggested the existence of a subsurface region with higher spin density than that in the bulk region.

Nucleation and initial growth of Pd2Si crystals on Si(111)

1993 ◽  
Vol 51 ◽  
pp. 844-845
Author(s):  
Xianghong Tong ◽  
Oliver Pohland ◽  
J. Murray Gibson
Keyword(s):  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Initial Growth ◽  
Surface And Interface ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Initial Stage ◽  
Effect Of Surface

The nucleation and initial stage of Pd2Si crystals on Si(111) surface is studied in situ using an Ultra-High Vacuum (UHV) Transmission Electron Microscope (TEM). A modified JEOL 200CX TEM is used for the study. The Si(111) sample is prepared by chemical thinning and is cleaned inside the UHV chamber with base pressure of 1x10−9 τ. A Pd film of 20 Å thick is deposited on to the Si(111) sample in situ using a built-in mini evaporator. This room temperature deposited Pd film is thermally annealed subsequently to form Pd2Si crystals. Surface sensitive dark field imaging is used for the study to reveal the effect of surface and interface steps.The initial growth of the Pd2Si has three stages: nucleation, growth of the nuclei and coalescence of the nuclei. Our experiments shows that the nucleation of the Pd2Si crystal occurs randomly and almost instantaneously on the terraces upon thermal annealing or electron irradiation.

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 Au Modified F-TiO2 for Efficient Photocatalytic Synthesis of Hydrogen Peroxide

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3844
Author(s):  
Lijuan Li ◽  
Bingdong Li ◽  
Liwei Feng ◽  
Xiaoqiu Zhang ◽  
Yuqian Zhang ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction System ◽  
Reaction Medium ◽  
Pure Tio2 ◽  
H2o2 Production ◽  
Tio2 Photocatalyst ◽  
H2o2 Decomposition ◽  
Spin Resonance ◽  
Photocatalytic Synthesis

In this work, Au-modified F-TiO2 is developed as a simple and efficient photocatalyst for H2O2 production under ultraviolet light. The Au/F-TiO2 photocatalyst avoids the necessity of adding fluoride into the reaction medium for enhancing H2O2 synthesis, as in a pure TiO2 reaction system. The F− modification inhibits the H2O2 decomposition through the formation of the ≡Ti–F complex. Au is an active cocatalyst for photocatalytic H2O2 production. We compared the activity of TiO2 with F− modification and without F− modification in the presence of Au, and found that the H2O2 production rate over Au/F-TiO2 reaches four times that of Au/TiO2. In situ electron spin resonance studies have shown that H2O2 is produced by stepwise single-electron oxygen reduction on the Au/F-TiO2 photocatalyst.

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