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Film
deposition of optical polymers
Poly(9,9-dioctylfluorene) (PF8) thin films have been
deposited by matrix-assisted pulsed laser evaporation (MAPLE) using a KrF
excimer laser, for optoelectronic applications. We studied the influence of
the laser fluence (50÷500mJ/cm2) and the nature of the solvent
(chloroform, toluene, tetrahydrofuran) on the films properties.
We investigate the chemical compositions of the
deposited films by Fourier Transform Infrared (FTIR) spectroscopy and
compared with the one of spin coated films.
Fig. 1:
FTIR transmittance spectra of films deposited by MAPLE with different
solvents (THF, chloroform and toluene). A representative spectrum of a spin
coated film is shown, too
When using THF and
toluene as solvent, the increasing of the laser fluence has no effect on the
peak presence or position, but a decreasing of the signal to noise ratio is
observed due, possibly, to an increase of the films thickness. In Fig. 2,
FTIR spectra in the range 2800-3100 cm-1
of samples
deposited at different laser fluences, from 200 to 500 mJ/cm2,
using PF8 diluted in toluene, are shown.
Fig. 2:
FTIR transmission spectra of MAPLE deposited PF8 films using toluene as
solvent, for different laser fluences.
To investigate the effect of the deposition parameters
on the optical properties of the films we perform photoluminescence
measurements.
Fig. 3:
PL spectra of samples deposited with MAPLE and spin coating techniques. All
the spectra are normalized to their peak value.
The spectra indicated Tetrahydrofuran (THF) as the
best solvent in MAPLE deposition and no damage is present in the polymer
after deposition.
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