Odesr Studies of a-Si:H with Subgap Excitation

1993 ◽  
Vol 297 ◽  
Author(s):  
D. Mao ◽  
S.Q. Gu ◽  
P.C. Taylor
Keyword(s):  
Magnetic Field ◽  
Excitation Energy ◽  
Signal Intensity ◽  
Sensitive Detection ◽  
Relative Signal Intensity ◽  
Recombination Processes ◽  
Phase Sensitive ◽  
Phase Sensitive Detection ◽  
Optically Detected ◽  
The Magnetic Field

We report studies of the spin-dependent recombination processes in device-quality a-Si:H by optically detected ESR (ODESR) with the excitation energy (Ex) varied from above-gap to sub-gap. The photoluminescence (PL) transients induced by the chopping of the microwaves are recorded as functions of the magnetic field to yield the lineshapes. This scheme, to some extent, circumvents the problem of interferences between "enhancing" and "quenching" signals encountered in conventional phase-sensitive detection. The PL below 1.1 eV is monitored. For Ex above 1.5 eV, we find all the lineshapes are similar: a broad, slightly asymmetric enhancing line peaking at g = 2.008 and an asymmetric quenching line peaking at g = 2.005. Lineshape changes are noticeable for Ex below 1.5 eV. The relative signal intensity AI/I changes dramatically with varying excitation energy. Light-soaking of the sample induces an additional enhancing signal which peaks at g = 2.006.

scholarly journals CO2 Methanation over Rh/CeO2 Studied with Infrared Modulation Excitation Spectroscopy and Phase Sensitive Detection

Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 601
Author(s):  
Felix Hemmingsson ◽  
Andreas Schaefer ◽  
Magnus Skoglundh ◽  
Per-Anders Carlsson
Keyword(s):  
Reaction Pathway ◽  
Sensitive Detection ◽  
Side Reactions ◽  
Co2 Methanation ◽  
Individual Contributions ◽  
Phase Sensitive ◽  
Phase Sensitive Detection ◽  
Modulation Excitation Spectroscopy ◽  
Modulation Excitation

Methane is a well-established fuel molecule whose production from CO 2 through methanation garners increasing interest as an energy storage solution. While often produced with Ni based catalysts, other metals are of interest thanks to higher robustness and activity-selectivity numbers. The Rh/CeO 2 catalyst has shown appreciable properties for CO 2 methanation and its structural dynamics has been studied in situ. However, the reaction pathway is unknown. Here, we present infrared modulation excitation spectroscopy measurements with phase sensitive detection of a Rh/CeO 2 catalyst adsorbate composition during H 2 pulsing (0–2 vol.%) to a constant CO 2 (0.5 vol.%) feed. Various carbonyl (CO) and carbonate (b-CO 3 /p-CO 3 ) ad-species clearly respond to the hydrogen stimulus, making them potential reaction intermediates. The different CO ad-species are likely intermediates for product CO and CH 4 but their individual contributions to the respective formations are not unambiguously ascertained. As for the carbonate dynamics, it might be linked to the reduction/oxidation of the CeO 2 surface upon H 2 pulsing. Formate (HCOO) ad-species are clearly visible but appear to be, if not spectators, linked to slow side reactions possibly also affected by CeO 2 redox processes.

scholarly journals Phase-Sensitive Detection for Optical Sensing With Porous Silicon

2012 ◽  
Vol 4 (3) ◽  
pp. 986-995 ◽  
Author(s):  
J. Alvarez ◽  
N. Kumar ◽  
P. Bettotti ◽  
D. Hill ◽  
J. Martinez-Pastor
Keyword(s):  
Porous Silicon ◽  
Optical Sensing ◽  
Sensitive Detection ◽  
Phase Sensitive ◽  
Phase Sensitive Detection
Sign in / Sign up

Export Citation Format

Share Document