Time-Resolved Reflection High-Energy Electron Diffraction Monitoring of the Surface Structural Changes of Si{111} during Q-Switched Laser (532 nm) Annealing

Abstract

Nanosecond surface structural changes during Q-switched laser annealing of a Si{111} crystal are studied with two-dimensional, time-resolved reflection of high-energy electron diffraction (RHEED) patterns obtained in real time synchronously with time-resolved optical reflectivity measurements. The detected Debye-Waller effect indicates the existence of a thermal process that results in melting of the surface. A transient crystalline surface phase is observed prior to recrystallization of the initial superstructure.

Ultrafast Electron Diffraction. 4. Molecular Structures and Coherent Dynamics

“…and the position vector is written rtj = iy(sin 0 cos sin £2 sin i/', cos £2) (15) The dot product of these two vectors simplifies to s-ry = s/y[sin(0/2) cos £2 -cos(0/2) sin £2 cos($ -f)] (16) To determine Fy, the scattering function eis''u must be integrated over the surface of the sphere defined by £2 and \p. The anisotropic spatial orientation is included by multiplying the scattering function with an appropriate distribution function, F(£2,^), before integration Fy(s) = Sin £2d^d £2 (17) Mathematical details on the evaluation of this integral for several relevant distribution functions have been consigned to the Appendix, For the case of an isotropic distribution (P(Q,\p) = 1), the results is:…”

“…The final result was an array of internuclear distances ranging in time from 0 to 2 ps. The modified molecular scattering curve was calculated from 0 to 15 A-1 (in 0.02-A-1 steps) at each time interval using eq 31, and the radial distribution curve was calculated from sM{s) with kA = 0.01 A2. In all graphs, the peak intensity at the inner and outer turning points decreases as a function of time, which shows that the classical wave packet is spreading and approaching a static distribution.…”

“…Figure15. Molecular dynamics of B-state iodine excited to 4750 cm-1 above the bottom of the potential well.…”