Time Resolved Transmission and Reflectivity of Pulsed Ruby Laser Irradiated Silicon

1981 ◽  
Vol 4 ◽  
Author(s):  
Douglas H. Lowndes ◽  
G. E. Jellison ◽  
R. F. Wood
Keyword(s):  
Ruby Laser ◽  
Crystalline Silicon ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Quantitative Agreement ◽  
Laser Wavelength ◽  
Time Resolved ◽  
Model Calculations ◽  
Thermal Melting ◽  
Apparent Disagreement

ABSTRACTThe time resolved optical transmission, T (atλ = 1152 nm), and reflectivity, R (at 633 nm and 1152 nm), have been measured for n-type single crystalline silicon (c-Si) during and immediately after pulsed ruby laser irradiation (λ = 693 nm, FWHM pulse duration 14 nsec), for a range of pulsed laser energy densities, El. The T is found to go to zero, and to remain at zero, for a period of time that increases with increasing El, in apparent disagreement with earlier measurements elsewhere that used semi-insulating Si and a different pulsed laser wavelength. Measured reflectivities during the high R phase agree within experimental error with reflectivities calculated from the optical constants of molten Si. Quantitative agreement is also found between both our T and R measurements and detailed time– and El-dependent results of thermal melting model calculations.

Pulsed Laser Melting of Amorphous Silicon: Time-Resolved and Post-Irradiation Studies

1983 ◽  
Vol 23 ◽  
Author(s):  
D. H. Lowndes ◽  
R. F. Wood ◽  
C. W. White ◽  
J. Narayan
Keyword(s):  
Pulsed Laser ◽  
Threshold Value ◽  
Dynamical Response ◽  
Cross Sectional ◽  
Time Resolved ◽  
Model Calculations ◽  
Fine Grained ◽  
Transmission Electron ◽  
Incident Laser Pulse ◽  
Thermal Melting

ABSTRACTMeasurements of the time of the onset of melting of self-implantation amorphized (a) Si, during an incident laser pulse, have been combined with modified melting model calculations and measurements of surface melt duration to demonstrate that the thermal conductivity, Ka, of a-Si is very low (≃0.02 W/cm-K). Ka is also shown to be the dominant parameter determining the dynamical response of ionimplanted Si to pulsed laser radiation; the latent heat and melting temperature of a-Si are relatively unimportant. Cross-sectional transmission electron micrographs on implantation-amorphized Si layers of several different thicknesses show that for energy densities less than the threshold value for complete annealing there are usually two distinct regions in the re-solidified a-Si, consisting of fine-grained and large-grained polycrystalline Si, respectively. The presence of the fine-grained poly-Si suggests that bulk nucleation occurs directly from the highly undercooled liquid phase. Thermal melting model calculations suggest that the nucleation temperature, Tn is ≃1200°C.

Time-resolved optical studies of oxide-encapsulated silicon during pulsed laser melting

1988 ◽  
Vol 3 (3) ◽  
pp. 498-505 ◽  
Author(s):  
G. E. Jellison ◽  
D. H. Lowndes ◽  
J. W. Sharp
Keyword(s):  
Laser Annealing ◽  
Laser Energy ◽  
Threshold Energy ◽  
Pulsed Laser ◽  
Silicon Layer ◽  
Oxide Thickness ◽  
Time Resolved ◽  
Model Calculations ◽  
Near Surface ◽  
Surface Profiling

Nanosecond time-resolved reflectivity and ellipsometry experiments have been performed on (100) Si wafers encapsulated by 5.5–76.2 nm thick thermal oxides, using pulsed KrF (248 nm) laser energy densities sufficient to melt the Si beneath the oxide. Post-irradiation nulling ellipsometry, optical microphotography, and surface profiling measurements were carried out. It was found that the threshold energy density required to melt the Si varies with oxide thickness; this is explained primarily by the reflective properties of the oxide overlayer. The time-resolved reflectivity and ellipsometry measurements show that rippling of the SiO2 layer occurs on the 20–40 ns timescale and results in a decrease in specular reflectivity of the rippled silicon surface beneath. Optical model calculations suggest that pulsed laser annealing through a thick oxide layer results in a damaged near-surface silicon layer (∼ 30 nm thick); this layer contains defects that are probably responsible for the degraded performance of devices.

Early Dynamics of a Laser-induced Underwater Shock Wave

2021 ◽  
Author(s):  
Guihua Lai ◽  
Siyuan Geng ◽  
Hanwen Zheng ◽  
Zhifeng Yao ◽  
Qiang Zhong ◽  
...  
Keyword(s):  
Shock Wave ◽  
Numerical Method ◽  
Cavitation Bubble ◽  
Laser Energy ◽  
Optical Breakdown ◽  
Pulsed Laser ◽  
Underwater Shock Wave ◽  
Time Resolved ◽  
High Attenuation ◽  
Nanosecond Pulsed Laser

Abstract The objective of this paper is to observe and investigate the early evolution of the shock wave, induced by a nanosecond pulsed laser in still water. A numerical method is performed to calculate the propagation of the shock wave within 1µs, after optical breakdown, based on the Gilmore model and the Kirkwood-Bethe hypothesis. The input parameters of the numerical method include the laser pulse duration, the size of the plasma and the maximally extended cavitation bubble, which are measured utilizing a high time-resolved shadowgraph system. The calculation results are verified by shock wave observation experiments at the cavitation bubble expansion stage. The relative errors of the radiuses and the velocity of the shock wave front, reach the maximum value of 45% at 5 ns after breakdown and decrease to less than 20% within 20 ns. The high attenuation characteristics of the shock wave after the optical breakdown, are predicted by the numerical method. The quick time and space evolution of the shock wave are carefully analyzed. The normalized shock wave width is found to be independent of the laser energy and duration, and the energy partitions ratio is around 2.0 using the nanosecond pulsed laser.

Synchrotron X-Ray Study of the Structure of Silicon During Pulsed Laser Processing

1981 ◽  
Vol 4 ◽  
Author(s):  
B. C. Larson ◽  
C. W. White ◽  
T. S. Noggle ◽  
J. F. Barhorst ◽  
D. Mills
Keyword(s):  
Laser Annealing ◽  
Pulsed Laser ◽  
Temperature Profiles ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
Near Surface ◽  
X Ray ◽  
Pulsed Laser Annealing ◽  
Pulsed Laser Processing ◽  
Thermal Melting

ABSTRACTSynchrotron x-ray pulses have been used to make nanosecond resolution time-resolved x-ray diffraction measurements on silicon during pulsed laser annealing. Thermal expansion analysis of near-surface strains during annealing has provided depth dependent temperature profiles indicating >1100°C temperatures and diffraction from boron implanted silicon has shown evidence for near-surface melting. These results are in qualitative agreement with the thermal melting model of laser annealing.

Time-Resolved and Nicrostructural Studies of Solidification in Undercooled Liquid Silicon

1988 ◽  
Vol 100 ◽  
Author(s):  
D. H. Lowndes ◽  
S. J. Pennycook ◽  
R. F. Wood ◽  
G. E. Jellison ◽  
S. P. Withrow
Keyword(s):  
Heat Flow ◽  
Near Infrared ◽  
Laser Energy ◽  
Solidification Process ◽  
Sample Surface ◽  
Undercooled Liquid ◽  
Time Resolved ◽  
Plan View ◽  
Model Calculations ◽  
Fine Grained

ABSTRACTNanosecond resolution visible (633 nm) and near-infrared (1152 nm) reflectivity measurements have been used, together with transmission electronmicroscopy (TEM), to study pulsed KrF (248 nm) laser melting and subsequent solidification of thick (190–410 nm) amorphous (a) silicon layers. The measurements cover the entire laser energy density (El) range between the onset of melting (∼ 0.12 J/cm2) and the completion of epitaxial crystallization (∼1.1 J/cm2). Four distinct El-regimes of melting and solidification are found for the 410-nm thick a-Si layers. For El > 0.25 J/cm2, the time of formation, velocity and final depth of “explosively” propagating undercooled liquid layers were measured in specimens that had been uniformly implanted with Si, Ge, or Cu. TEM shows that the “fine-grained polycrystalline Si” produced by explosive crystallization (XC) actually contains large numbers of disk-shaped Si flakes that have largely amorphous centers and are visible only in plan view. The optical and TEM measurements suggest (1) that flakes are the crystallization events that initiate XC, and (2) that lateral heat flow (parallel to the sample surface) must be taken into account in order to understand flake formation. Results of new two-dimensional (2-D) model calculations of heat flow and solidification are presented. These calculations confirm the importance of 2-D heat flow and crystallite growth early in the solidification process. For 0.3 4 < El > 1.0 J/cm2, pronounced changes in both the shape and the duration of the reflectivity signals provide information about the growth of polycrystalline grains; this information can be correlated with post-irradiation plan and cross-section view TEM microstructural measurements.

Low-Energy, Pulsed-Laser Irradiation of Amorphous Silicon: Melting and Resolidification at Two Fronts

1984 ◽  
Vol 35 ◽  
Author(s):  
W. Sinke ◽  
F.W. Saris
Keyword(s):  
Amorphous Silicon ◽  
Laser Irradiation ◽  
Surface Segregation ◽  
Crystalline Silicon ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Surface Region ◽  
Low Energy ◽  
Double Peak Structure ◽  
Pulsed Laser Irradiation

ABSTRACTAfter low-energy pulsed-laser irradiation of Cu-implanted silicon, a double-peak structure is observed in the Cu concentration profile, which results from the occurrence of two melts. From Cu surface segregation we calculate the depth of the surface melt. Cu segregation near the position of the amorphous-crystalline interface gives evidence for a self-propagating melt, moving from the surface region towards the crystalline substrate. Measurements of As-redistribution and of sheet resistance as a function of laser energy density in As-implanted silicon are consistent with the crystallization model which is derived from the effects as observed in Cu-implanted silicon.The results imply a large difference in melting temperature, heat conductivity and heat of melting between amorphous silicon and crystalline silicon.

Transient Surface Temperature Measurement With Micro Sensors for Nanosecond Pulsed Laser Micromachining of Nickel

2006 ◽  
Author(s):  
Hongseok Choi ◽  
Xiaochun Li
Keyword(s):  
Laser Energy ◽  
Numerical Models ◽  
Pulsed Laser ◽  
Laser Micromachining ◽  
Measured Data ◽  
Time Resolved ◽  
Nanosecond Pulsed Laser ◽  
Thin Film Thermocouples ◽  
Transient Thermal ◽  
Thermal Phenomena

In order to investigate and understand the complicated transient thermal phenomena in laser micro processing, it is essential to accurately measure time-resolved temperatures of the workpiece. Micro thin film thermocouples with a micrometer spatial and nanosecond temporal resolution were fabricated on electroplated nickel workpieces to measure transient surface temperatures in nanosecond pulsed laser micromachining by ablation. Transient temperatures were successfully measured, and the effect of laser energy fluences on the peak temperatures was experimentally investigated. This study demonstrates that the micro TFTCs can be useful in measuring the transient temperatures on the workpiece during laser micromachining, and the measured data can be utilized to validate and improve existing analytical and numerical models.

Raman Scattering with Nanosecond Resolution During Pulsed Laser Heating of Silicon

1982 ◽  
Vol 13 ◽  
Author(s):  
D. Von Der Linde ◽  
G. Wartmann ◽  
A. Ozols
Keyword(s):  
Phase Transition ◽  
Raman Scattering ◽  
Laser Heating ◽  
Crystalline Silicon ◽  
Silicon Crystal ◽  
Pulsed Laser ◽  
Lattice Temperature ◽  
Time Resolved ◽  
Pulsed Laser Heating ◽  
Anti Stokes

ABSTRACTWe present time-resolved measurements of spontaneous anti-Stokes and Stokes Raman scattering during pulsed laser heating of crystalline silicon. The time-evolution of the lattice temperature is determined from the measured anti-Stokes/Stokes intensity ratio. In a separate calibration experiment we measure the temperature dependence of the anti-Stokes/Stokes ratio of an oven-heated silicon crystal from 300 K up to 900 K. The phase transition occuring during laser heating is detected by monitoring the changes of the optical reflectivity during laser irradiation. Our data suggest that the phase transition occurs at a lattice temperature of ∼600 K.

scholarly journals Matrix-Assisted Pulsed Laser Thin Film Deposition by Using Nd:YAG Laser

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Francesco Bloisi ◽  
Mario Barra ◽  
Antonio Cassinese ◽  
Luciano Rosario Maria Vicari
Keyword(s):  
Nd:Yag Laser ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Thin Film Deposition ◽  
Laser Wavelength ◽  
Film Deposition ◽  
Laser Evaporation ◽  
Polymeric Thin Films ◽  
Transparent Liquid ◽  
Desorption Mechanism

Matrix-Assisted Pulsed Laser Evaporation (MAPLE) is a deposition technique, developed from Pulsed Laser Deposition (PLD) especially well suited for producing organic/polymeric thin films, which can take advantage from using Nd:YAG laser. Depending on the relative values of light absorption coefficients of the solvent and of the molecules to be deposited, laser energy is directly absorbed by the solvent or is transferred to it, providing a softer desorption mechanism with respect to PLD. In PLD ultraviolet laser radiation is commonly used, but in MAPLE, since easily damaged molecules are usually involved, the use of Nd:YAG laser offers the advantage to allow selecting laser wavelength from ultraviolet (266 nm or 355 nm, corresponding to 4.66 eV or 3.49 eV photon energies, resp.) to visible (532 nm, 2.33 eV) to infrared (1064 nm, 1.17 eV). In this paper, the MAPLE technique is described in details, together with a survey of current and possible future applications for both organic and biomaterial deposition taking into account the advantages of using an Nd:YAG laser. Beside other results, we have experimental confirmation that MAPLE applications are not limited to transparent molecules highly soluble in light absorbing solvent, thus allowing deposition of poorly soluble light absorbing molecules suspended in a light transparent liquid.

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