Excitation Spectroscopy of Photoluminescence of a-Si:H

1990 ◽  
Vol 192 ◽  
Author(s):  
S. Q. Gu ◽  
P. C. Taylor
Keyword(s):  
Absorption Spectrum ◽  
Room Temperature ◽  
Tunable Laser ◽  
Excitation Source ◽  
Photoluminescence Excitation ◽  
Dangling Bond ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection ◽  
Very High

Photoluminescence excitation (PLE) spectra at 77 K have been measured over the range 1.201.75 eV using the Ti sapphire cw tunable laser as the excitation source. Two undoped a-Si:H samples on rough substrates have been investigated. The first sample has a very high dangling bond (DB) density; the second one has low DB density. The PLE spectrum of photoluminescence (PL) at 0.8 eV for the first sample follows the shape of the absorption spectrum measured by photothermal deflection spectroscopy (PDS) at room temperature. This behavior can be understood within the context of the existing models as due to recombination through defects which produces PL centered around 0.8 eV. However the PLE spectrum of PL at 0.8 eV for the second sample drops very rapidly with decreasing energy for energies less than about 1.3 eV. This behavior, which differs dramatically from that of the absorption spectrum, is consistent with earlier results and suggests that the PL measured at 0.8 eV for the second sample may be largely due to a contribution of the tail of the PL band which peaks near 1.3 eV. The PLE spectra for PL at 1.0 eV and 1.1 eV for the second sample approach the PLE spectrum previously obtained using the integrated PL intensities.

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.

Light-Soaking Effects on Photoconductivity in a-Si:H Thin Films

1997 ◽  
Vol 467 ◽  
Author(s):  
E. Morgado ◽  
M. Rebelo da Silva ◽  
R. T. Henriques
Keyword(s):  
Thin Films ◽  
Defect Density ◽  
Light Exposure ◽  
Dangling Bond ◽  
Photothermal Deflection Spectroscopy ◽  
Spin Resonance ◽  
Photo Conductivity ◽  
Photothermal Deflection ◽  
Gap States ◽  
Induced Defects

ABSTRACTMetastable defects have been created by light exposure in thin films of a-Si:H. The samples have been characterized by Photothermal Deflection Spectroscopy, Electron Spin Resonance, dark- and photo-conductivity. The experimental results are consistent with numerical calculations with a recombination model involving band tails and one class of correlated dangling-bond states. The effects of light-soaking on the ligh intensity and defect density dependences of photoconductivity are reproduced by the calculations. The model allows to explain the experimental trends by changes in the electronic occupation of the gap states produced by light-induced defects.

Collinear Photothermal Deflection Spectroscopy of Liquid Samples at Varying Temperature

1993 ◽  
Vol 47 (10) ◽  
pp. 1580-1584 ◽  
Author(s):  
Jonathan D. Spear ◽  
Robert J. Silva ◽  
Gregory L. Klunder ◽  
Richard E. Russo
Keyword(s):  
Absorption Spectrum ◽  
Physical Properties ◽  
Temperature Dependence ◽  
Beam Deflection ◽  
Photothermal Deflection Spectroscopy ◽  
Liquid Samples ◽  
Photothermal Deflection

The method of photothermal beam deflection was demonstrated for measuring the absorption spectrum of an aqueous Nd3+ solution at temperatures between 25°C and 90°C. Changes in the magnitude of the observed deflection can be correlated with the temperature dependence of both the absorptivity of the Nd3+ ions and the physical properties of the solvent, most notably the thermo-optic coefficient d n/d T.

High Performance Photoluminescence Spectroscopy using Fourier Transform Interferometry

1989 ◽  
Vol 163 ◽  
Author(s):  
M.L.W. Thewalt ◽  
M.K. Nissen ◽  
D.J.S. Beckett ◽  
K.R. Lundgren
Keyword(s):  
Fourier Transform ◽  
Spectral Resolution ◽  
High Performance ◽  
Tunable Laser ◽  
High Sensitivity ◽  
Photoluminescence Spectroscopy ◽  
High Spectral Resolution ◽  
Photoluminescence Excitation ◽  
Laser Sources ◽  
Very High

AbstractWe present recent results on the applications of Fourier transform techniques to photoluminescence spectroscopy as it relates to both basic and characterization-related semiconductor research. The emphasis here is on demonstrating the advantages of these methods in situations requiring very high spectral resolution and/or very high sensitivity. We also provide an example of the utility of interferometry in performing photoluminescence excitation spectroscopy in spectral regions where broadly tunable laser sources are not readily available.

A Discussion of Electronic Optical Absorption Spectra of Nanocrystalline Silicon thin Films

1989 ◽  
Vol 164 ◽  
Author(s):  
Etienne Bustarret ◽  
M.A. Hachicha
Keyword(s):  
Room Temperature ◽  
Nanocrystalline Silicon ◽  
Low Energy ◽  
Similar Data ◽  
Silicon Thin Films ◽  
Photothermal Deflection Spectroscopy ◽  
Energy Part ◽  
Average Grain Size ◽  
Photothermal Deflection ◽  
Hydrogenated Amorphous

AbstractBoth fully crystallized nanocrystalline as-deposited silicon layers with an average grain size ranging between 6 and 80 nm and mixed-phase hydrogenated doped and undoped silicon films are studied at room temperature by Photothermal Deflection Spectroscopy (PDS), Transmission Spectroscopy and Spectroscopic Ellipsometry. The differences with regard to similar data obtained on monocrystalline and hydrogenated amorphous silicon are discussed, with an emphasis on the low-energy part of the 0.6-5.6 eV explored range.

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

Temperature Dependent Line-Shape of the Silicon Dangling Bond EPR-Resonance in Polycrystalline Silicon

1996 ◽  
Vol 452 ◽  
Author(s):  
N. H. Nickel ◽  
E. A. Schiff
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Polycrystalline Silicon ◽  
Room Temperature ◽  
Dangling Bond ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Temperature Electron ◽  
Motional Narrowing ◽  
G Value ◽  
Electron Paramagnetic

AbstractThe temperature dependence of the silicon dangling-bond resonance in polycrystalline (poly-Si) and amorphous silicon (a-Si:H) was measured. At room temperature, electron paramagnetic resonance (EPR) measurements reveal an isotropie g-value of 2.0055 and a line width of 6.5 and 6.1 G for Si dangling-bonds in a-Si:H and poly-Si, respectively. In both materials spin density and g-value are independent of temperature. While in a-Si:H the width of the resonance did not change with temperature, poly-Si exhibits a remarkable T dependence of ΔHpp. In unpassivated poly-Si a pronounced decrease of ΔHpp is observed for temperatures above 300 K. At 384 K ΔHpp reaches a minimum of 5.1 G, then increases to 6.1 G at 460 K, and eventually decreases to 4.6 G at 530 K. In hydrogenated poly-Si ΔHpp decreases monotonically above 425 K. The decrease of ΔHpp is attributed to electron hopping causing motional narrowing. An average hopping distance of 15 and 17.5 Å was estimated for unhydrogenated and H passivated poly-Si, respectively.

Molecule-Based Magnets—An Overview

MRS Bulletin ◽  
2000 ◽  
Vol 25 (11) ◽  
pp. 21-30 ◽  
Author(s):  
Joel S. Miller ◽  
Arthur J. Epstein
Keyword(s):  
Low Temperature ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Low Density ◽  
Materials Properties ◽  
The Common ◽  
New Processing ◽  
Very High

Molecule-based magnets are a broad, emerging class of magnetic materials that expand the materials properties typically associated with magnets to include low density, transparency, electrical insulation, and low-temperature fabrication, as well as combine magnetic ordering with other properties such as photoresponsiveness. Essentially all of the common magnetic phenomena associated with conventional transition-metal and rare-earth-based magnets can be found in molecule-based magnets. Although discovered less than two decades ago, magnets with ordering temperatures exceeding room temperature, very high (∼27.0 kOe or 2.16 MA/m) and very low (several Oe or less) coercivities, and substantial remanent and saturation magnetizations have been achieved. In addition, exotic phenomena including photoresponsiveness have been reported. The advent of molecule-based magnets offers new processing opportunities. For example, thin-film magnets can be prepared by means of low-temperature chemical vapor deposition and electrodeposition methods.

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