Homogeneous and inhomogeneous contributions to the luminescence
linewidth of point defects in amorphous solids: Quantitative assessment based
on time-resolved emission spectroscopy
The article describes an experimental method that allows to estimate the
inhomogeneous and homogeneous linewidths of the photoluminescence band of a
point defect in an amorphous solid. We performed low temperature time-resolved
luminescence measurements on two defects chosen as model systems for our
analysis: extrinsic Oxygen Deficient Centers (ODC(II)) in amorphous silica and
F+ 3 centers in crystalline Lithium Fluoride. Measurements evidence that only
defects embedded in the amorphous matrix feature a dependence of the radiative
decay lifetime on the emission energy and a time dependence of the first moment
of the emission band. A theoretical model is developed to link these properties
to the structural disorder typical of amorphous solids. Specifically, the
observations on ODC(II) are interpreted by introducing a gaussian statistical
distribution of the zero phonon line energy position. Comparison with the
results obtained on F+ 3 crystalline defects strongly confirms the validity of
the model. By analyzing experimental data within this frame, we obtain separate
estimations of the homogenous and inhomogeneous contributions to the measured
total linewidth of ODC(II), which results to be mostly inhomogeneous.Comment: 8 pages, 4 figure
