PhD thesis defense: Vapor Phase Infiltration (VPI) and Doping of Conducting Polymers
CIC nanoGUNE Seminars
- Speaker
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Weike Wang, Nanomaterials Group, nanoGUNE
- When
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2017/10/26
13:00 - Place
- CFM Auditorium
- Add to calendar
-
iCal
In this thesis, the ¨ Vapor Phase infiltration ¨ (VPI), a vacuum based
process derived from the atomic layer deposition (ALD), is used for the top-
down infiltration and doping of various conducting polymers. In the first part
of this thesis, a single precursor vapor phase infiltration (VPI) process to
dope polyaniline (PANI) is presented. As dopants, the vaporized Lewis acidic
precursors SnCl4 and MoCl5 were used at a process temperature of 150 °C.
After 100 cycles, the MoCl5-infiltrated PANI showed the highest conductivity,
2.93 × 10-4 S/cm, which is a significant enhancement of up to 6 orders of
magnitude in comparison to undoped PANI. SnCl4-infiltrated PANI showed highest
conductivity after 60 cycles with a value of 1.03 × 10-5 S/cm. The doping
process with MoCl5 and SnCl4 results in an oxidation of PANI backbone. As a
result, the electron mobility along the polymer chains is significantly
enhanced and the structure is stabilized even at an elevated temperature in a
vacuum environment. The second part of this thesis describes the single
precursor VPI and doping of poly(3-hexyl)thiophene (P3HT). During the
infiltration processes, the Lewis acid MoCl5 was used as precursor at a
process temperature of 70 °C. The highest values show an increase of 5 orders
of magnitude for the conductivity, namely from 1.44 × 10-5 S/cm in the as
prepared P3HT to 3.01 S/cm after infiltration 100 cycles. In the last part of
this thesis, the multiple pulsed vapor phase infiltration (MPI) process was
applied to dope polyaniline (PANI). For the process, the two typical ALD
precursors diethylzinc (DEZ) and deionized water (H2O) were used at a process
temperature of 155 °C. The room temperature I-V plots show the conductivity
of Zn-infiltrated PANI increasing to 18.42 S/cm, up to three orders of
magnitude higher than obtained upon conventional doping with 1 M HCl in wet-
chemical ways. Infiltration of PANI with Zn from the vapor phase results in a
hybrid or composite material consisting of ZnO and PANI in the subsurface area
of the polymer. Being chemically bound to each other, the inorganic and
organic components mutually dope each other for the benefit of the resulting
conductivity.
**Supervisor** : Mato Knez