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Which salts, of all the binary alkaline earth chalcogenides with a 'rock-salt' structure, can be doped with halogen anions replacing some of the chalcogen, without destroying the lattice? (That is not a solid solution of alkaline earth halogenide in chalcogenide, but a more alkaline earth metal-rich ternary composition with a 1:1 ratio of cations:total anion count.)

What is the maximum achievable dopant concentration?

Is the result also electrically conductive, like n-type extrinsic semiconductors are?

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    $\begingroup$ Somewhat related pubs.acs.org/doi/10.1021/acsnano.2c02116 ncbi.nlm.nih.gov/pmc/articles/PMC10720346 $\endgroup$
    – Mithoron
    Commented Jun 18 at 20:37
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    $\begingroup$ @Mithoron metal chalcogenide halides are totally off-topic, since structure changes and stoichiometry is too anion-rich. $\endgroup$
    – Paul Kolk
    Commented Jun 19 at 12:32
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    $\begingroup$ @PaulKolk - it does give me more specific things to look up, but not until next week… $\endgroup$
    – Jon Custer
    Commented Jun 21 at 18:01
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    $\begingroup$ @PaulKolk - somehow my spare time got eaten by weasels or something. From the searches I was able to do it seems that actual thermodynamic data is pretty thin on the ground for doping these compounds. As opposed to, say Si, Ge, GaAs, etc. But, there isn't Bell Labs anymore to go off and do a bunch of fundamental work like solubility and dopant activation measurements. Sigh. $\endgroup$
    – Jon Custer
    Commented Jul 8 at 14:23

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An example of fluorine doping in a mixed magnesium-zinc oxide is reported in the open-access article by [Liu et al.[1]](https://doi.org/10.1038/srep15516). The excerpt below from the abstract indicates the effectiveness of fluorine as an $n$-type dopant. The oxide actually has a wurtzite rather than a rocksalt crystal structure; presumably the tetrahedral rather than octahedral coordination in the wurtzite structure facilitates diffusion of the large fluoride ions into the crystal.

Fluorine dopants were demonstrated to be effective donors in $\ce{Mg_{0.51}Zn_{0.49}O}$ single crystal film having a solar-blind $4.43$ eV bandgap, with an average concentration of $1.0×10^{19}$ F/cm$^3$. The dramatically increased carrier concentration ($2.85×10^{17}$ cm$^{−3}$ vs $\sim10^{14}$ cm$^{−3}$) and decreased resistivity ($129$ Ω•cm vs $\sim10^6$ Ω•cm) indicate that the electrical properties of semi-insulating $\ce{Mg_{0.51}Zn_{0.49}O}$ film can be delicately regulated by $\ce{F}$ doping.

Reference

1. Lishu Liu, Zengxia Mei, Yaonan Hou, Huili Liang, Alexander Azarov, Vishnukanthan Venkatachalapathy, Andrej Kuznetsov & Xiaolong Du. "Fluorine doping: a feasible solution to enhancing the conductivity of high-resistance wide bandgap $\ce{Mg_{0.51}Zn_{0.49}O}$ active components". Sci Rep 5, 15516 (2015). https://doi.org/10.1038/srep15516

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  • $\begingroup$ BTW, why is it easier to find info about zinc group chalcogenides than alkaline earth chalcogenides? Just because of technological applications of the former? $\endgroup$
    – Paul Kolk
    Commented Jun 21 at 12:54
  • $\begingroup$ Possibly beryllium as tge AEM coukd work as it coordinates tetrahedrally without the inclusion of zinc, but beryllium compounds are not as well studied as those of Mg and Ca. $\endgroup$ Commented Jun 21 at 13:03
  • $\begingroup$ Ion diffusion in the liquid state is no issue anyway. Is it likely that crystallization from the melt of suitable stoichiometry yields a dopant-poor phase with rock salt structure and excess metal (and AEM halogenide) separately? $\endgroup$
    – Paul Kolk
    Commented Jun 21 at 13:40
  • $\begingroup$ The doped material is a thin film grown eputaxialluly at 450°C, not from liquid. See the Methods section. $\endgroup$ Commented Jun 21 at 14:02
  • $\begingroup$ Reposted due to unfortunate typo in the original. This compound overlaps both metal groups. Zinc has the advantage of forming wurtzite structures, which as I said facilitates ion diffusion in the doping process, and although magnesium like most other AEMs prefers the rocksalt structure it can be incorporated into a zinc-bearing wurtzite structure. $\endgroup$ Commented Jun 22 at 10:55

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