Lithium aluminum
germanium phosphate of the stoichiometric formula
Li1.5Al0.5Ge1.5(PO4)3 has been studied by means of the femtosecond laser plasma
charge attachment induced transport (fs-plasma CAIT). The technique
is based on attaching polarity selected charge carriers from a plasma
to the front side of a sample, which induces transport of mobile charge
carriers in the bulk of this sample. First, in a conductivity study,
an activation energy of 0.73 eV for lithium ion transport has been
measured by means of proton attachment. Second, a constant-voltage
attachment experiment employing deuterium ions has been performed
and subsequently analyzed by time-of-flight secondary ion mass spectrometry.
The resulting concentration depth profile revealed a replacement of
native lithium ions by deuterons in the first 350 nm of the sample.
A theoretical analysis of the profile by means of the Nernst–Planck–Poisson
equations provides access to the concentration dependent diffusion
coefficient and the unique site energy distribution of the natively
contained lithium ions. A full width at half-maximum of 113 meV for
the SED of the Li+ ions is determined. The approach discussed
can be applied to many more materials, where the potential energy
landscape affects the function.