An Investigation of Photo-Induced Degradation by Means of Photothermal Deflection Spectroscopy

1987 ◽  
Vol 95 ◽  
Author(s):  
M. S. Bennett ◽  
S. Wiedeman ◽  
J. L. Newton ◽  
K. Rajan
Keyword(s):  
Optical Absorption ◽  
Fermi Level ◽  
Single Peak ◽  
Defect States ◽  
Hydrogenated Silicon ◽  
Photothermal Deflection Spectroscopy ◽  
Amorphous Hydrogenated Silicon ◽  
Measured Absorption ◽  
Photothermal Deflection

AbstractAbsorption measurements of as deposited and photodegraded intrinsic amorphous hydrogenated silicon films were made using photothermal deflection spectroscopy (PDS). The films were light-soaked in situ using HeNe laser light to simulate AM1 illumination. An increase in subbandgap absorption occurred predominantly near energies of 1.2eV. A simple model was developed in which a density of states function is hypothesized and the resulting optical absorption at subgap energies is calculated. The measured absorption could be well matched in all cases by assuming a single peak of defect states at or slightly below the Fermi level. Further, the observed changes in optical absorption due to degradation could be modeled by increasing the density of the single peak of defect states and moving the Fermi level towards the valence band.

Photothermal Deflection Spectroscopy Investigations of Uranium Electrochemistry - II

1993 ◽  
Vol 333 ◽  
Author(s):  
James D. Rudnicki ◽  
Richard E. Russo
Keyword(s):  
Optical Absorption ◽  
Saturated Calomel Electrode ◽  
Sample Surface ◽  
Oxidation Potential ◽  
Dissolution Mechanism ◽  
Concentration Gradients ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection ◽  
Oxide Electrochemistry

ABSTRACTPhotothermal Deflection Spectroscopy (PDS) has been applied to the study of uranium oxide electrochemistry. PDS measures the optical absorption of the sample surface and concentration gradients formed in the electrolyte. Both of these measurements are performed in situ under dynamic conditions. The combination of these two measurements provides information that can be used to infer the mechanism of the UO2 surface chemistry. These studies of the uranium dissolution mechanism are performed in pH 10.5 sodium sulfate electrolytes at 22°C. The electrolytes are free from oxygen, and complexing species. Our results suggest that dissolution of UO2 can occur at oxidizing potentials as low as -300 mV vs. saturated calomel electrode (SCE). The optical absorption and concentration gradient results provide evidence for a substantial surface change that occurs at an oxidation potential of +300 mV. The results show that the surface layer formed by this change dissolves slowly by a non-electrochemical reaction.

Microstructure and Dangling Bond Defects in Amorphous Hydrogenated Silicon Deposited Near Room Temperature

1992 ◽  
Vol 258 ◽  
Author(s):  
Man Ken Cheung ◽  
Mark A. Petrich
Keyword(s):  
Room Temperature ◽  
Dangling Bond ◽  
Optimum Conditions ◽  
Band Tail ◽  
Hydrogenated Silicon ◽  
Photothermal Deflection Spectroscopy ◽  
Amorphous Hydrogenated Silicon ◽  
Photothermal Deflection ◽  
Substrate Temperatures ◽  
Absorption Measurements

ABSTRACTThe microstructure of high-density amorphous hydrogenated silicon (a-S.i:H) films deposited at 50°C substrate temperature was revealed by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies to be similar to that of “device-quality” a-Si:H films deposited at standard “optimum” conditions. However, optical absorption measurements of these low microstructure 50°C films with photothermal deflection spectroscopy indicate that they have higher densities of gap state defects and localized band tail states than “device-quality” films deposited at standard substrate temperatures. The correlation between the amount of microstructure and electronic properties is not unique. A low amount of microstructure is a necessary, but not sufficient, requirement for high electronic quality a-Si:H films.

Accurate Reconstruction of the Density of States in a-Si:H by Photothermal and Photoconductive Spectra.

1993 ◽  
Vol 297 ◽  
Author(s):  
G. Amato ◽  
F. Giorgis ◽  
C. Manfredotti
Keyword(s):  
Iterative Method ◽  
Absorption Coefficient ◽  
Fermi Level ◽  
Density Of States ◽  
Localized States ◽  
Electronic Transitions ◽  
Photothermal Deflection Spectroscopy ◽  
Derivative Method ◽  
Photothermal Deflection ◽  
Made In

The distribution of occupied states in a-Si:H has been inferred by applying a new self- consisting iterative method to the absorption coefficient spectra. This procedure does not require any assumption about the localized states below the Fermi level, and provides a more accurate insight with respect to the simple derivative method. Numerical simulations have been made in order to probe the reliability of our method. The optical spectra have been obtained by means of Photothermal Deflection Spectroscopy (PDS) and Constant Photocurrent Method (CPM); the comparison between the results as obtained by the two techniques suggests that different sensitivities to electronic transitions are involved; this can be used to infer information about the unoccupied defects.

A study of optical absorption in amorphous hydrogenated silicon thin films of varied thickness

2010 ◽  
Vol 256 (18) ◽  
pp. 5667-5671 ◽  
Author(s):  
J. Müllerová ◽  
L. Prušáková ◽  
M. Netrvalová ◽  
V. Vavruňková ◽  
P. Šutta
Keyword(s):  
Thin Films ◽  
Optical Absorption ◽  
Hydrogenated Silicon ◽  
Silicon Thin Films ◽  
Amorphous Hydrogenated Silicon

scholarly journals Subgap Absorption in Conjugated Polymers

1991 ◽  
Vol 228 ◽  
Author(s):  
M. Sinclair ◽  
C. H. Seager ◽  
D. McBranch ◽  
A. J. Heeger ◽  
G. L. Baker
Keyword(s):  
Optical Absorption ◽  
Conjugated Polymers ◽  
Absorption Edge ◽  
Spectral Region ◽  
Absorption Coefficients ◽  
Photothermal Deflection Spectroscopy ◽  
Integrated Optical ◽  
Integrated Optical Devices ◽  
Photothermal Deflection ◽  
Sample Age

ABSTRACTAlong with χ(3), the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10-5, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of “transparent” materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly[1,4-phenylenevinylene] (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm-1 to 10 cm-1. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration or fluorination.

Sign in / Sign up

Export Citation Format

Share Document