{
  "abstract": "Where crystal nuclei form in amorphous phase-change materials decides how they switch. We study six successive 4D-STEM scans, with simultaneous HAADF and EDS data, of a magnetron-sputtered Ge-Sb-Te (GST) film, restricted to the GST layer and its interface with the oxide beneath it. Nucleation sites do not differ in composition or number density: the nuclei lie on the same robust HAADF-EDS relation as the matrix, and at fixed HAADF the spread of the summed EDS signal equals its Poisson counting noise (ratio 1.03 +- 0.05). The nuclei are nevertheless crystalline and stand out in the 4D-STEM max-intensity virtual image (median z = 11.0) but not in HAADF (z = 1.3) or EDS (z = 0.3). We classify the film in four ways (HAADF intensity, I(q) phase mapping, PCA of the whole diffraction patterns and a self-supervised SimCLR encoder) and compare the electron pair distribution functions (PDFs) of all classes after calibrating reciprocal space on the Au cap. All bulk classes share one short-range structure (first shell 2.70-2.74 Å); towards the interface the first sharp diffraction peak (FSDP) moves to lower q, and every method isolates a thin interface-edge environment with a shorter or missing first shell. The I(q) classification isolates, in every scan, an interface environment that holds 62-100% of the nucleus pixels (1.2-2.5-fold above depth) and persists when the nucleus pixels are removed before classification. The interface, rather than a distinct composition or density of the nucleating volume, therefore marks where nuclei form. Over 4.7e3 e/Å^2 the HAADF signal falls by 17%, the first shell shortens by 0.03 Å and the FSDP narrows by 9%, apparently ordering the film as it damages it. All analyses used PySTEMLab, an interactive 4D-STEM analysis environment developed for this work.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.15196",
  "author_total": 4,
  "authors": [
    {
      "name": "Mridul Kumar"
    },
    {
      "name": "Kirill Sobolev"
    },
    {
      "name": "Alexander Upcher"
    },
    {
      "name": "Yevgeny Rakita"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ep94nkb5y201w.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.15196",
  "fulltext_url": null,
  "id": "ep94nkb5y201w",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.15196",
  "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",
      "1315|Advanced Electron Microscopy Techniques and Applications"
    ]
  ],
  "openalex": "W7221774944",
  "pdf_url": "https://arxiv.org/pdf/2610.15196",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-10",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ep94nkb5y201w.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:29:06Z",
      "native_id": "2610.15196",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.15196"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Nucleation at the GST--oxide interface and beam-driven ordering in amorphous Ge--Sb--Te: HAADF, EDS and electron pair distribution functions across a 4D-STEM dose series",
  "title_text": "Nucleation at the GST--oxide interface and beam-driven ordering in amorphous Ge--Sb--Te: HAADF, EDS and electron pair distribution functions across a 4D-STEM dose series",
  "type": "preprint",
  "updated_at": "2026-10-30T12:29:06Z",
  "url": "https://research.draconitic.com/paper/ep94nkb5y201w",
  "venue": "arXiv",
  "versions": []
}