The formulation of a standard computerized procedure for the indexing of powder X‐ray diffraction (PXRD) patterns of columnar liquid crystals, with the determination of all structural information extracted from a properly indexed PXRD spectrum and the attribution of the columnar mesophase symmetry, is presented. In particular, the proposed program notably accelerates the identification of columnar mesophases together with the in situ determination of their structural parameters such as mesophase type, space group, cell parameters, cross‐section area, intermolecular stacking distance between consecutive discoids and, in the case of ordered mesophases, the estimation of the number of molecules constituting each discoid.
We propose an explanation for the origin of n-type electrical conductivity in SnO2 based on the results obtained from the DFT+U simulations. Two competitive intrinsic point defects, namely oxygen vacancy and hydrogen impurity, have been considered at different positions within the crystalline lattice in order to find out the equilibrium configurations and to analyze corresponding density of states (DOS) patterns along with the electron localization function (ELF). It has been demonstrated that hydrogen could be solely responsible for the n-type conductivity whereas the oxygen vacancy appears to have not a notable influence upon it. The computational analysis is backed up by some experimental data for undoped tin dioxide.
In
this study, the Al3+–Sn4+ substitution
reaction in the AlN-doped SnO2 thin films is confirmed
by photoluminescence and X-ray photoelectron spectrum analysis. Also,
both Al3+–Sn4+ and N3––O2– substitution reactions are verified
by computational simulation, Vienna ab initio simulation package
(VASP). The computational simulation shows that both Al and N impurity
dopants generate an unoccupied band at the upper valence band maximum,
which produces holes within the upper valence band region. Both Al3+–Sn4+ and N3––O2– substitution reactions contribute to the p-type conversion
of AlN-doped SnO2 thin films. Annealing AlN-doped SnO2 (Al content is 14.65%) thin films at high-temperature (larger
than 350 °C), N outgassing would occur and cause the p-type conduction
of the annealed AlN-doped SnO2 thin films back to n-type
conduction. Yet, in this work, we found that the Al3+–Sn4+ substitution reaction in the high Al-doping concentration
of Al-doped and AlN-doped SnO2 (the Al content is between
29% and 33.2%) thin films would be activated considerably, as they
are annealed at a temperature over 500 °C. With a higher Al-doping
concentration (Al concentration is 33.2%) in the Al-doped SnO2 thin films, we found that the critical annealing temperature
for the n-to-p conduction transition decreases to 500 °C. The
Al dopants in the AlN-doped SnO2 thin films annealed at
high annealing temperature not only stabilize the N3––O2– substitution reactions but also produce
hole carriers by the Al3+–Sn4+ substitution
reactions. The Al3+–Sn4+ substitution
makes the AlN-doped SnO2 retain the p-type conduction
in the high-temperature annealing.
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