Spectroscopic study and structural characterization of a Li-related photoluminescence center in neutron-irradiated Si

Abstract

We report on a new Li-related photoluminescence center with zero-phonon line at 879.3 meV. The center is created at 550-600°C in the final stages of annealing out radiation-induced point defects in float-zone silicon. Isotope and chemical correlation data establish that the center contains Li and C atoms. The isotope shift from 6 Li to 7 Li, ⌬EϭE(7 Li)ϪE(6 Li)ϭ0.18 meV, is similar, per Li atom, to that observed for other Li-related centers in silicon. Uniaxial stress measurements establish the symmetry as monoclinic I, with only small departures from trigonal symmetry. A simple method for the transition is introduced to fit simultaneously the energies, polarizations, and relative intensities of the stress-split components. The transition's dipole is shown to be close to a bonding direction in the plane perpendicular to the characteristic ͗110͘ axis of the monoclinic I center. The vibronic sideband is produced by coupling to modes of 16, 31, and 36 meV, with a Huang-Rhys factor Sϭ1.1. This value can be predicted simply from the uniaxial-stress data. The temperature dependence of the zero-phonon line can be fitted precisely using the spectrum of coupled phonons derived from the vibronic band shape, plus the approximation that the differences in frequencies of the phonons in the ground and excited electronic states are proportional to the phonon frequency. The luminescence from the center is reversibly quenched with increasing temperature, with an activation energy E a ϭ32Ϯ5 meV, however, we show that this result does not arise from the excited state containing a shallow particle. Although the center is created at 600°C, it is rapidly destroyed at room temperature through passivation by the capture of one mobile Li atom.

Time-resolved spectroscopy in LiCaAlF6doped with Cr3+: dynamical Jahn–Teller effect and thermal shifts associated with the4T2excited state

“…for Mn 2+ -fluoroperovskites ABF 3 :Mn 2+ [32], suggesting that both terms contribute significantly to the thermal shift although the explicit contribution is slightly higher than the implicit one. This contrasts with the behaviour of weakly coupled systems as a trapped exciton in semiconductors like silicon, where the thermal shift of the trapped exciton ZPL is fully governed by the explicit contribution [36]. As a general conclusion, present results suggest that the stronger the electron-phonon coupling is, the larger the volume expansion contribution to the thermal shift.…”

Photoluminescence in ZnO:Co2+ (0.01%–5%) Nanoparticles, Nanowires, Thin Films, and Single Crystals as a Function of Pressure and Temperature: Exploring Electron–Phonon Interactions

“…(c) Simulation of the phonon-sideband of the 8 K emission spectrum using the EPDOS depicted in the inset derived from the emission spectra. The simulation was done by convoluting the one-phonon density of sates (red dotted line) to the fifth order coupling, B 5 , with B n being the n -phonon order convoluted DOS, following the procedure given in ref , using a Huang–Rhys parameter of S = 1.35 and the equation for the effective one-phonon DOS, EPDOS = e – S ∑ n = 1 N (( S n B n )/ n ! ).…”