Time-dependent heat flow calculation of cw laser-induced melting of silicon

Schván, P.; Thomas, R.E.

doi:10.1063/1.335337

Cited by 38 publications

(6 citation statements)

References 13 publications

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“…The percentage of differences between the predictions and measured values in Figure is higher at lower laser powers. Schvan and Thomas in consideration of the CW laser-induced melting of silicon have also reported such a deviation in comparison of calculated with measured melt depths. This was attributed to the fact that the spatial gradient of the temperature is lower near the peak of the temperature profile, which is the important region at lower incident powers.…”

Section: Resultsmentioning

confidence: 90%

Direct Patterning of Self-Assembled Monolayers on Gold Using a Laser Beam

et al. 2004

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The development of a methodology to manipulate surface properties of a self-assembled monolayer (SAM) of alkanethiol on a gold film using direct laser patterning is the objective of this paper. The present study demonstrates proof of the concept for the feasibility of laser patterning monolayers and outlines theoretical modeling of the process to predict the resulting feature size. This approach is unique in that it eliminates the need for photolithography, is noncontact, and can be extended to other systems such as SAMs on silicon wafers or potentially polymeric substrates. A homogeneous SAM made of 1-hexadecanethiol is formed on a 300-A sputtered film of gold (supported by a soda lime glass substrate). Localized regions are then desorbed by scanning the focal spot of a 488-nm continuous-wave argon ion laser beam under a nitrogen atmosphere. The desorption occurs as a result of a high substrate temperature produced by the moving laser beam with a Gaussian spatial profile at a constant speed of 200 microm/s. After completing the scans, the sample is dipped into a dilute solution of 16-mercaptohexadecanoic acid and a hydrophilic monolayer self-assembles along the previously irradiated regions. The resultant lines are viewed, and line widths are measured using both wetting with tridecane under a light microscope and scanning electron microscopy. Using the direct laser patterning method, we have produced straight line patterns with widths of 28-170 microm. A thermal model was constructed to predict the line width of the desorbed monolayer. The effect of the laser power, beam waist, and temperature dependence of the substrate conductivity on the theoretical predictions is considered. It is shown that the theoretical predictions are in good agreement with the experimental results, and, thus, the model can effectively be used to predict experimental results.

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Section: Resultsmentioning

confidence: 90%

Direct Patterning of Self-Assembled Monolayers on Gold Using a Laser Beam

et al. 2004

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“…We also note that there is significant modification of the region around the focal point of the laser, extending to several hundred microns ( Figure 2 b). We expect that exposure of the CW laser generates heat at the focal point, and its accumulation causes significant oxidation and modification on the sample surface [ 14 , 15 , 16 ]. In contrast, the femtosecond laser demonstrates a clean cut and minimal darkening on the sample ( Figure 2 c).…”

Section: Resultsmentioning

confidence: 99%

Obtaining Cross-Sections of Paint Layers in Cultural Artifacts Using Femtosecond Pulsed Lasers

et al. 2017

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Recently, ultrafast lasers exhibiting high peak powers and extremely short pulse durations have created a new paradigm in materials processing. The precision and minimal thermal damage provided by ultrafast lasers in the machining of metals and dielectrics also suggests a novel application in obtaining precise cross-sections of fragile, combustible paint layers in artwork and cultural heritage property. Cross-sections of paint and other decorative layers on artwork provide critical information into its history and authenticity. However, the current methodology which uses a scalpel to obtain a cross-section can cause further damage, including crumbling, delamination, and paint compression. Here, we demonstrate the ability to make controlled cross-sections of paint layers with a femtosecond pulsed laser, with minimal damage to the surrounding artwork. The femtosecond laser cutting overcomes challenges such as fragile paint disintegrating under scalpel pressure, or oxidation by the continuous-wave (CW) laser. Variations in laser power and translational speed of the laser while cutting exhibit different benefits for cross-section sampling. The use of femtosecond lasers in studying artwork also presents new possibilities in analyzing, sampling, and cleaning of artwork with minimal destructive effects.

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“…The transient heat conduction equation governing the heat flow in the wafer may be written as follows:

\frac{\partial}{\partial t} true(ρ C_{p} T true) = \nabla true(K \nabla T true) + ρ C_{p} v \frac{\partial T}{\partial x} + Q_{l},

where

ρ

is the density, C p is the specific heat capacity, K is the thermal conductivity, and v is the scanning speed of the laser beam. The variable Q l is the volumetric heat source representing the energy flow from laser beam into the material, and may be expressed as

Q_{l} = true(1 - R true) α I_{0} e x p true(- \frac{x^{2}}{σ_{s \tan d}^{2}} true) e x p true(\int_{0}^{y} - α true(y true) d y true),

where

α

is the absorption coefficient, I 0 is the maximum laser beam intensity, R is the reflection coefficient, and σ stand is the standard deviation of the laser beam. The initial and boundary conditions for the problem may be written as

T true(x, y, 0 true) = T_{i},

- K \frac{\partial T}{\partial x} = h true(T - T_{\infty} true) + ϵ true(σ T^{4} - {T_{\infty}}^{4} true), at X = - L / 2 and X = L / 2,

…”

Section: Modelling Approachmentioning

confidence: 99%

“…where ρ is the density, C p is the specific heat capacity, K is the thermal conductivity, and v is the scanning speed of the laser beam. The variable Q l is the volumetric heat source representing the energy flow from laser beam into the material, and may be expressed as [28,30]…”

Section: Modelling Approachmentioning

confidence: 99%

Thermal Effects on the Hydrogen Passivation of Silicon Wafers During Diode Laser Annealing

Ahmmed

Song

Huda

2018

Physica Status Solidi (a)

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This paper presents a study of the laser induced thermal effects on the hydrogen passivation of silicon wafers. Thermal treatment, due to laser annealing, can be responsible for the release of atomic hydrogen from the dielectric layers, the diffusion of hydrogen into the silicon wafers and the passivation of defects. The whole process results in a reduction of active defects, and hence an increase of the minority carrier lifetime of the silicon wafers. Understanding of the mechanisms of heat transfer during the laser annealing is essential for obtaining an optimal hydrogenation effect. In this paper, a numerical model for evaluation of temporal and spatial temperature distributions in a silicon wafer during laser annealing is developed. The model is developed using the open‐source C + + framework known as OpenFOAM. A continuous wave (CW) diode laser of 808 nm wavelength is used for laser annealing of the silicon wafers containing dielectric layers of hydrogenated silicon nitride. The simulations are carried out at the experimental conditions and the impact of key laser annealing parameters, such as scanning speeds, laser power densities and substrates initial temperatures, are carefully investigated. The simulated results are then correlated with the experimental results of photoluminescene (PL) imaging and injection level dependent effective lifetime data. Our results show that the localized hydrogen passivation of the silicon wafers using laser annealing depends on the peak temperature and duration of heat. Additionally, it is found that the preheating of the wafer has a substantial effect on the reduction of thermal stress, while leading to a good degree of localized hydrogen passivation of the wafers. A correlation is also developed for the maximum spot temperature which will serve as a guideline for selecting optimum operating conditions.

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Time-dependent heat flow calculation of cw laser-induced melting of silicon

Cited by 38 publications

References 13 publications

Direct Patterning of Self-Assembled Monolayers on Gold Using a Laser Beam

Direct Patterning of Self-Assembled Monolayers on Gold Using a Laser Beam

Obtaining Cross-Sections of Paint Layers in Cultural Artifacts Using Femtosecond Pulsed Lasers

Thermal Effects on the Hydrogen Passivation of Silicon Wafers During Diode Laser Annealing

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