Charge transport in nanoparticular thin films of zinc oxide and aluminum-doped zinc oxide
Summary (1 min read)
Journal of
- These nanoparticles were produced by ame spray synthesis36–38 and are expected to have high crystallinity and no adverse surface ligands.
- For the synthesis of AZO nanoparticles with a nominal composition of 2 wt% Al2O3 in ZnO, the same Zn-acetate precursor with additional Al-acetylacetonate 2-ethylhexanoic acid under the same process conditions was used.
- Consequently the thermal activation energy for the charge transport is reduced.
Conclusion
- The conduction through nanoparticulate ZnO and AZO thin lms was investigated.
- While the J–V characteristics at low voltage obey Ohm's law, transport in the high voltage data regime is dominated by the Poole–Frenkel effect.
- It is outlined that the occurrence of the Poole–Frenkel effect is related to coulombically bound electrons, which have to overcome a elddependent barrier to the next nanoparticle.
- To the best of their knowledge, this is the rst time that the Poole–Frenkel effect was unambiguously demonstrated as the dominant transport mechanism in a nanoparticulate thin lm.
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Frequently Asked Questions (9)
Q2. What is the effect of the Poole–Frenkel effect in the high voltage data regime?
While the J–V characteristics at low voltage obey Ohm's law, transport in the high voltage data regime is dominated by the Poole–Frenkel effect.
Q3. What is the way to disperse ZnO nanoparticles?
These nanoparticles were produced by ame spray synthesis36–38 and are expected to have high crystallinity and no adverse surface ligands.
Q4. What is the synthesis of AZO nanoparticles?
For the synthesis of AZO nanoparticles with a nominal composition of 2 wt% Al2O3 in ZnO, the same Zn-acetate precursor with additional Al-acetylacetonate 2-ethylhexanoic acid under the same process conditions was used.
Q5. What is the problem of nanoparticulate ZnO deposited at low temperatures?
The problem of nanoparticulate ZnO thin lms deposited at low temperatures is that they hardly reach the electric performance of zinc oxide lms based on sputtering21 or spray pyrolysis.
Q6. What is the main transport mechanism in a nanoparticle?
It is outlined that the occurrence of the Poole–Frenkel effect is related to coulombically bound electrons, which have to overcome a elddependent barrier to the next nanoparticle.
Q7. What is the effect of the PF on the AZO thin lms?
Al is a shallow donor in ZnO (in ref. 59, it was shown that Al is even substitutionally shallow) and by the increased free charge-carrier concentration the Fermi-energy is closer to the “transportband”.
Q8. What is the resulting thickness of the nanoparticles?
A dispersion of ligandstabilized ZnO or AZO nanoparticles was deposited on top of an ITO substrate via multiple doctor blading34,35 steps.
Q9. What is the plot of the trap barrier height?
This plot corresponds to eqn (3). (c) The y-intercepts of the linear fit functions (lns0) in (b) are plotted versus the inverse of temperature to determine the trap barrier height.