Pulsed–Raman Measurements of Temperature When Large Temperature Variations and Gradients are Present

ABSTRACTPulsed Raman temperature measurements by Lo and Compaan on Si samples have been interpreted as proving that the surface region does not melt during intense pulsed laser irradiation. In this paper, it is shown by detailed calculations with the melting model that the choice of experimental parameters in the Raman measurements can severely compromise a straightforward interpretation of the data. Moreover, it is demonstrated that temperatures extracted from Raman measurements are highly sensitive to the temperature-dependent optical properties of the material. Finally, it is pointed out that the very large temperature gradients present during pulsed laser annealing may entirely invalidate the Stokes/anti-Stokes ratio as an accurate temperature probe.

Download Full-text

Stress Effects on Raman Measurements of Pulsed Laser Annealed Silicon

MRS Proceedings ◽

10.1557/proc-23-153 ◽

1983 ◽

Vol 23 ◽

Cited By ~ 7

Author(s):

G. E. Jellison ◽

R. F. Wood

Keyword(s):

Raman Scattering ◽

Laser Irradiation ◽

Laser Annealing ◽

Phonon Frequency ◽

Pulsed Laser ◽

Front Surface ◽

Surface Region ◽

Pulsed Laser Annealing ◽

Anti Stokes ◽

Pulsed Laser Irradiation

ABSTRACTIt has recently been shown that the front surface region of the silicon lattice is severely strained during pulsed laser irradiation. This uniaxial strain reduces the symmetry of the front surface region, resulting in additional shifts and splittings of the phonon frequency and changes in the Raman scattering tensor. It is shown that, for the case of pulsed laser irradiation, the phonon frequency is increased, and the 3-fold degenerate optical phonon is split into a singlet and a doublet. The changes in the Raman scattering tensor make it non-symmetric, and generally invalidate the technique used by Compaan et al. to determine the cross section experimentally. The complications introduced by the presence of stress during pulsed laser annealing, coupled with the temperature dependence of the optical and Raman tensors, make a simple interpretation of the Stokes to anti-Stokes ratio in terms of lattice temperature extremely unreliable.

Download Full-text

Impurity Activation in N+ Ion-Implanted 6H-SiC with Pulsed Laser Annealing Method

MRS Proceedings ◽

10.1557/proc-640-h5.31 ◽

2000 ◽

Vol 640 ◽

Cited By ~ 2

Author(s):

O. Eryu ◽

K. Aoyama ◽

K. Abe ◽

K. Nakashima

Keyword(s):

Contact Resistance ◽

Laser Irradiation ◽

Carrier Density ◽

Laser Annealing ◽

Pulsed Laser ◽

Surface Region ◽

Near Surface ◽

Pulsed Laser Annealing ◽

Annealing Method ◽

Ion Implanted

ABSTRACTWe have succeeded in pulsed laser annealing of N+ ion-implanted n-type 6H-SiC for increasing the carrier density near surface in order to decrease contact resistance, which induces little redistribution of implanted impurities after laser irradiation. By repeated laser irradiation at low energy density, the ion–implanted impurities were electrically activated without melting the surface region. SiC substrates with impurity concentration of 2×1018 /cm3 were implanted with 30 keV N+ ions with dose of 4.7×1013/cm2. After pulsed laser annealing, a contact resistance was measured to be 5.7×10−5 Ωcm2 using Al electrode on the N+ -implanted layer.

Download Full-text

A Detailed Examination of Time-Resolved Pulsed Raman Temeperature Measurements of Laser Annealed Silicon

MRS Proceedings ◽

10.1557/proc-13-35 ◽

1983 ◽

Vol 13 ◽

Cited By ~ 5

Author(s):

G. E. Jellison ◽

D. H. Lowndes ◽

R. F. Wood

Keyword(s):

Optical Properties ◽

Pulse Width ◽

Laser Annealing ◽

Pulsed Laser ◽

Detailed Examination ◽

Temperature Gradients ◽

Probe Laser ◽

Time Resolved ◽

Pulsed Laser Annealing ◽

Anti Stokes

ABSTRACTRaman temperature measurements during pulsed laser annealing of Si by Compaan and co-workers are critically examined. It has been shown previously that the Stokes to anti-Stokes ratio depends critically upon the optical properties of silicon as a function of temperature. These dependences, coupled with the large spatial and temporal temperature gradients normally found immediately after the high reflectivity phase, result in large variations in the calculated temperature depending upon the probe laser pulse width and the pulse-to-pulse and spatial variations in the annealing pulse energy density.

Download Full-text

Calculations Pertaining to Raman Scattering During Laser Annealing of Ion-Implanted Silicon

MRS Proceedings ◽

10.1557/proc-4-67 ◽

1981 ◽

Vol 4 ◽

Cited By ~ 1

Author(s):

R. F. Wood ◽

D. H. Lowndes ◽

G. E. Giles

Keyword(s):

Laser Annealing ◽

Pulsed Laser ◽

Rapid Onset ◽

Simultaneous Occurrence ◽

Raman Signal ◽

Molten Silicon ◽

Time Resolved ◽

Pulsed Laser Annealing ◽

Anti Stokes ◽

Ion Implanted

ABSTRACTCompaan and co-workers have reported the results of time-resolved optical experiments on ion-implanted silicon which they claim prove the melting model of pulsed laser annealing cannot be correct. These results concern the rapid onset of a Raman signal after a heating laser pulse, the simultaneous occurrence of a Raman signal and the high reflectivity phase characteristic of molten silicon, and the lattice temperature measured by the Raman Stokes/anti-Stokes intensity ratio. In this paper, we show by detailed numerical calculations with the melting model that there is, in fact, excellent agreement between the results of the calculations and the experimental results reported by Compaan and co-workers.

Download Full-text

Electron-Phonon and Phonon-Phonon Interactions Under Laser Annealing Conditions

MRS Proceedings ◽

10.1557/proc-35-65 ◽

1984 ◽

Vol 35 ◽

Cited By ~ 3

Author(s):

Alvin Compaan

Keyword(s):

Laser Annealing ◽

Temperature Dependent ◽

Time Resolved ◽

Resonance Effects ◽

Pulsed Laser Annealing ◽

Annealing Conditions ◽

Silent Phase ◽

High Carrier ◽

Anti Stokes ◽

First Time

ABSTRACTSince the first time-resolved Raman studies of pulsed laser annealing (PLA) effects in Si, a number of cw Raman studies have been performed which provide a much improved basis for understanding the consequences on Raman spectra of temperature-dependent resonance effects, high carrier density effects, phonon anharmonicity, and strain effects. Here we briefly review these effects and then analyze the latest pulsed Raman studies of PLA including Stokes/anti-Stokes ratios, the shift and shape of the first order line, and time-resolved second-order spectra. The Raman data indicate the existence of a Raman-silent phase followed by a rapidly cooling solid which begins within 300 K of the normal melting temperature of Si. The Raman data also give evidence of carrier densities in the recrystallizing solid of ~1−2×l019/cm3 .

Download Full-text