Time-Resolved Ellipsometry and Reflectivity Measurements of the Optical Properties of Silicon During Pulsed Excimer Laser Irradiation

1984 ◽  
Vol 35 ◽  
Author(s):  
G. E. Jellison ◽  
D. H. Lowndes
Keyword(s):  
Optical Properties ◽  
Laser Irradiation ◽  
Crystalline Silicon ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Time Resolved ◽  
High Reflectivity ◽  
Use Of Time ◽  
Before And After ◽  
Melting Threshold

ABSTRACTSeveral advances in time-resolved optical measurement techniques have been made, which allow a more detailed determination of the optical properties of silicon immediately before, during, and after pulsed laser irradiation. It is now possible to follow in detail the time-resolved reflectivity signal near the melting threshold; measurements indicate that melting occurs in a spatially inhomogeneous way. The use of time-resolved ellipsometry allowed us to accurately measure the optical properties of the high reflectivity (molten) phase, and of the hot, solid silicon before and after the laser pulse. We obtain n = 3.8, k = 5.2 (±10.1) at λ = 632.8 nm for the high reflectivity phase, in minor disagreement with the published values of Shvarev et al. for liquid silicon. Before and after the high reflectivity phase, the time-resolved ellipsometry measurements are entirely consistent with the known optical properties of crystalline silicon at temperatures up to its melting point.

scholarly journals Time-resolved reflectivity technique: improvement and applications

1999 ◽  
Vol 1 (2) ◽  
pp. 101-105 ◽  
Author(s):  
K. M. A. EL-Kader
Keyword(s):  
Energy Density ◽  
Laser Irradiation ◽  
Crystalline Silicon ◽  
Threshold Energy ◽  
Time Resolved ◽  
Hydrogenated Silicon ◽  
Maximum Reflectivity ◽  
Amorphous Hydrogenated Silicon ◽  
Melting Threshold ◽  
Constant Energy Density

A new method for determination of the reflectivity of Si in different phase transitions during pulsed laser irradiation is presented in this paper. This method is applied on TRR spectra of crystalline silicon (c-Si) in a medium of oxygen and amorphous hydrogenated silicon (a-Si: H). Time resolved reflectivity (TRR) measurements on silicon has been made during pulsed XeCl excimer laser irradiation (308 nm, 28nm FWHM) in a medium of oxygen. The samples were irradiated in the energy density range400−100mJ/cm2. The reflectivity was measured with a probe He-Ne laser (632.8 nm). Depending on the energy density of the excimer pulse, heating, melting and resolidification of the surface were monitored by TRR spectra. From these measurements we were able to determine the melting threshold energy density for c-Si, depending on the energy densities, time of melting and maximum reflectivity have been measured. TRR spectra of a sample with3μm thick a-Si layer for first shot of measurements were calibrated. A series of a-Si: H samples of the same thickness (0.34μm) irradiated with a constant energy density450mJ/cm2and the three consecutive TRR spectra of the irradiated samples were calibrated.

Laser-Induced Modification of the Surface State and Optical Properties of CdTe Crystals

2011 ◽  
Vol 222 ◽  
pp. 28-31
Author(s):  
Leonid V. Poperenko ◽  
Dmytro V. Gnatyuk ◽  
Volodymyr A. Odarych ◽  
Iryna V. Yurgelevich ◽  
Sergiy N. Levytskyi ◽  
...  
Keyword(s):  
Optical Properties ◽  
Surface State ◽  
Laser Pulses ◽  
Nanosecond Laser ◽  
Treatment Conditions ◽  
Before And After ◽  
Melting Threshold ◽  
Modified Surface ◽  
Nanosecond Laser Pulses ◽  
Modification Of The Surface

Optical properties and surface state of semiconductor CdTe crystals subjected to irradiation with nanosecond laser pulses were studied. Ellipsometric parameters Δ and Ψ were measured on two opposite surfaces of (111) oriented CdTe wafers before. The samples were subjected to polishing chemical etching and laser irradiation with energy densities lower and higher than the melting threshold of CdTe. The morphology and structure of CdTe crystals were monitored before and after treatments. Irradiation formed a thin modified surface layer on the both sides of CdTe crystals (Cd- and Te-terminated) with the similar optical constants n and k, respectively. However, the effective thicknesses of such modified layers differed and depended on the chemical and laser treatment conditions and also on the faces of CdTe(111) crystals.

The Effect of Intrinsic Instabilities on Effective Flame Speeds in Under-Resolved Simulations of Lean Hydrogen–Air Flames

2017 ◽  
Vol 3 (4) ◽  
Author(s):  
Peter Katzy ◽  
Josef Hasslberger ◽  
Lorenz R. Boeck ◽  
Thomas Sattelmayer
Keyword(s):  
Flame Front ◽  
Optical Measurement ◽  
Initial Conditions ◽  
Measurement Techniques ◽  
Evaluation Methods ◽  
Line Of Sight ◽  
Flame Surface ◽  
Validation Data ◽  
Time Resolved ◽  
The Impact

The presented work aims to improve computational fluid dynamics (CFD) explosion modeling for lean hydrogen–air mixtures on under-resolved grids. Validation data are obtained from an entirely closed laboratory-scale explosion channel (GraVent facility). Investigated hydrogen–air concentrations range from 6 to 19 vol %. Initial conditions are p = 0.1 MPa and T = 293 K. Two highly time-resolved optical measurement techniques are applied simultaneously: (1) 10 kHz shadowgraphy captures line-of-sight integrated macroscopic flame propagation and (2) 20 kHz planar laser-induced fluorescence of the OH radical (OH-PLIF) resolves microscopic flame topology without line-of-sight integration. This paper presents the experiment, measurement techniques, data evaluation methods, and simulation results. The evaluation methods encompass the determination of flame tip velocity over distance and a detailed time-resolved quantification of the flame topology based on OH-PLIF images. One parameter is the length of wrinkled flame fronts in the OH-PLIF plane obtained through automated postprocessing. It reveals the expected enlargement of flame surface area by instabilities on a microscopic level. A strong effect of mixture composition is observed. Simulations based on the new model formulation, incorporating the microscopic enlargement of the flame front, show a promising behavior, where the impact of the augmented flame front on the observed flame front velocities can be detected.

scholarly journals The Effect of Annealing on the Structural and Optical Properties of Titanium Dioxide Films Deposited by Electron Beam Assisted PVD

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Yaser M. Abdulraheem ◽  
Sahar Ghoraishi ◽  
Lidia Arockia-Thai ◽  
Suji K. Zachariah ◽  
Moustafa Ghannam
Keyword(s):  
Titanium Dioxide ◽  
Optical Properties ◽  
Electron Beam ◽  
Physical Vapor Deposition ◽  
Crystalline Silicon ◽  
Anatase Phase ◽  
Structural And Optical Properties ◽  
Titanium Dioxide Films ◽  
Before And After ◽  
Titanium Dioxide Thin Films

Titanium dioxide thin films were deposited on crystalline silicon substrates by electron beam physical vapor deposition. The deposition was performed under vacuum ranging from 10−5to 10−6Torr without process gases, resulting in homogeneousTiO2-xlayers with a thickness of around 100 nm. Samples were then annealed at high temperatures ranging from500°C to800°C for 4 hours under nitrogen, and their structural and optical properties along with their chemical structure were characterized before and after annealing. The chemical and structural characterization revealed a substoichiometricTiO2-xfilm with oxygen vacancies, voids, and an interface oxide layer. It was found from X-ray diffraction that the deposited films were amorphous and crystallization to anatase phase occurred for annealed samples and was more pronounced for annealing temperatures above700°C. The refractive index obtained through spectroscopic ellipsometry ranged between 2.09 and 2.37 in the wavelength range, 900 nm to 400 nm for the as-deposited sample, and jumped to the range between 2.23 and 2.65 for samples annealed at800°C. The minimum surface reflectance changed from around 0.6% for the as-deposited samples to 2.5% for the samples annealed at800°C.

scholarly journals Influence of Laser Radiation on Optical Properties of Semiconductor Materials

2019 ◽  
Vol 20 (4) ◽  
pp. 384-390
Author(s):  
P.O. Gentsar ◽  
S.M. Levytskyi
Keyword(s):  
Optical Properties ◽  
Laser Irradiation ◽  
Pulsed Laser ◽  
Semiconductor Materials ◽  
Surface Layers ◽  
Defective Structure ◽  
Before And After ◽  
532 Nm ◽  
Transmission And Reflection ◽  
Pulsed Laser Irradiation

In this paper, the transmission and reflection spectra of n-Si(100) single crystals are measured; n-GaAs(100); solid solutions of Ge1-хSiх (х = 0.85) in the range (0.2 - 1.7)·10-6 m before and after laser irradiation at the wavelength λ = 532 nm. It is established that the main mechanism of influence of pulsed laser irradiation on the optical properties of thin surface layers of the investigated crystals is structural gettering, that is, the absorption due to the presence of sections of semiconductors that have a defective structure and have the ability to actively absorb defects and points.

Optical Properties of Soot Remelted Silica Irradiated with Excimer Lasers

1991 ◽  
Vol 244 ◽  
Author(s):  
Yasutaka Matsumoto ◽  
Nobu Kuzuu ◽  
Masataka Murahara
Keyword(s):  
Optical Properties ◽  
Absorption Band ◽  
Laser Irradiation ◽  
Emission Band ◽  
Excimer Lasers ◽  
Absorption Bands ◽  
Before And After ◽  
Arf Laser

ABSTRACTCharacteristics of ArF laser induced luminescence, and absorption bands in soot remelted silica, before and after annealing in various atmospheres, were investigated. A soot remelted silica containing no OH has an absorption band at 5.1 eV which can be annealed out with H2, but an absorption band at 5.8 eV is induced by subsequent the ArF laser irradiation. In a soot remelted silica containing 50 ppm of OH, an emission band at 1.9 eV was induced by the ArF laser irradiation. The 1.9 eV band can be annealed out with He and H2, but, by annealing in H2, the 5.8 eV absorption band was induced by the ArF laser irradiation as in the case of the silica containing no OH.

Optical Insights into the Internal Electronic and Thermal Behavior of 4H-SiC Bipolar Devices

2010 ◽  
Vol 645-648 ◽  
pp. 1041-1044 ◽  
Author(s):  
Dorothea Werber ◽  
Martin Aigner ◽  
Gerhard Wachutka
Keyword(s):  
Thermal Behavior ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Free Carrier Absorption ◽  
Time Resolved ◽  
Bipolar Devices ◽  
Carrier Absorption ◽  
Optical Probing ◽  
Stationary Conditions ◽  
Yield Time

Two different optical measurement techniques have been combined in one single experimental platform to provide detailed insight into the interior of 4H-SiC bipolar devices with respect to their coupled electronic and thermal behavior: First, free carrier absorption (FCA) measurements yield time-resolved electron and hole densities profiles during turn-on and under stationary conditions; and second, light deflection measurements provide information about the gradients of the electron and hole densities as well as that of the temperature gradient. The full measurement process is also simulated on the computer as “virtual experiment” on the basis of high-fidelity physical device models. Investigations on high-blocking 4H-SiC bipolar diodes exemplify the optical probing methodology and the numerical simulation.

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