{
  "abstract": "p-type oxide contact layers such as Cr$_2$O$_3$ and NiO are attracting increasing interest in pn-heterojunctions with n-type monoclinic $β$-Ga$_2$O$_3$ for high-power electronic devices and other extreme environment applications. However, scientific understanding of their epitaxial relationships remains incomplete. In this work we investigate the epitaxial relation of Cr$_2$O$_3$ and NiO layers to (001) and ($\\bar{2}$01) out-of-plane oriented Ga$_2$O$_3$ substrates. Surprisingly, we find that, for the most commercially relevant (001)-orientation of the Ga$_2$O$_3$ substrate, the epitaxial relationships are Cr$_2$O$_3$ (0001) and NiO (111) $\\parallel$ Ga$_2$O$_3$ (101), both at the non-intuitive $χ$ = 22.5 $^\\circ$ angle with respect to the substrate normal. We explain this unusual discovery by the interfacial atomistic bonding dominated by oxygen sublattice equivalence of these Cr$_2$O$_3$ and NiO polar surface orientations to the tilted Ga$_2$O$_3$ (101), rather than Ga$_2$O$_3$ (001) substrate surface planes. Furthermore, we assign the in-plane orientation for Cr$_2$O$_3$ on ($\\bar{2}$01)-oriented Ga$_2$O$_3$ as: Cr$_2$O$_3$ $[12\\bar{3}0]$ $\\parallel$ Ga$_2$O$_3$ $[010]$ with two in-plane rotational domains. Interface modeling confirms the in-plane orientation for Cr$_2$O$_3$/$(\\bar{2}01)$ Ga$_2$O$_3$ and shows that strained O-terminated Ga$_2$O$_3$ $(\\bar{2}01)$ surfaces have the lowest interfacial energy with Cr$_2$O$_3$ (0001). Beyond establishing the specific epitaxial relationships for Cr$_2$O$_3$ and NiO on Ga$_2$O$_3$, this work provides a systematic methodology for the unambiguous structural characterization of heterointerfaces involving materials with markedly different crystal symmetries.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.22472",
  "author_total": 8,
  "authors": [
    {
      "name": "Anna Sacchi"
    },
    {
      "name": "Krishna Acharya"
    },
    {
      "name": "Michelle A. Smeaton"
    },
    {
      "name": "Renae N. Gannon"
    },
    {
      "name": "Vladan Stevanovic"
    },
    {
      "name": "Steven R. Spurgeon"
    },
    {
      "name": "M. Brooks Tellekamp"
    },
    {
      "name": "Andriy Zakutayev"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/e3jw08b11p5eg.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.22472",
  "fulltext_url": null,
  "id": "e3jw08b11p5eg",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.22472",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mtrl-sci"
    ],
    [
      "openalex",
      "2504|Ga2O3 and related materials"
    ]
  ],
  "openalex": "W7214013426",
  "pdf_url": "https://arxiv.org/pdf/2609.22472",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-18",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/e3jw08b11p5eg.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:19Z",
      "native_id": "2609.22472",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.22472"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Revealing epitaxial relationships at Ga$_2$O$_3$ interfaces with p-type oxides",
  "title_text": "Revealing epitaxial relationships at Ga_2O_3 interfaces with p-type oxides",
  "type": "preprint",
  "updated_at": "2026-10-30T12:23:19Z",
  "url": "https://research.draconitic.com/paper/e3jw08b11p5eg",
  "venue": "arXiv",
  "versions": []
}