Unique Bond Breaking in Crystalline Phase Change Materials and the Quest for Metavalent Bonding. Issue 18 (23rd March 2018)

• Record Type: Journal Article
• Authors: Zhu, Min; Cojocaru‐Mirédin, Oana; Mio, Antonio M.; Keutgen, Jens; Küpers, Michael; Yu, Yuan; Cho, Ju‐Young; Dronskowski, Richard; Wuttig, Matthias
• Is Part Of: Advanced materials. Volume 30:Issue 18(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-03-23
• Subjects: chemical bonding in solids -- laser‐assisted field evaporation -- metavalentbonding -- phase change materials; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201706735
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Laser‐assisted field evaporation is studied in a large number of compounds, including amorphous and crystalline phase change materials employing atom probe tomography. This study reveals significant differences in field evaporation between amorphous and crystalline phase change materials. High probabilities for multiple events with more than a single ion detected per laser pulse are only found for crystalline phase change materials. The specifics of this unusual field evaporation are unlike any other mechanism shown previously to lead to high probabilities of multiple events. On the contrary, amorphous phase change materials as well as other covalently bonded compounds and metals possess much lower probabilities for multiple events. Hence, laser‐assisted field evaporation in amorphous and crystalline phase change materials reveals striking differences in bond rupture. This is indicative for pronounced differences in bonding. These findings imply that the bonding mechanism in crystalline phase change materials differs substantially from conventional bonding mechanisms such as metallic, ionic, and covalent bonding. Instead, the data reported here confirm a recently developed conjecture, namely that metavalent bonding is a novel bonding mechanism besides those mentioned previously. Abstract : Bond breaking is characterized by laser‐assisted field evaporation in atom probe tomography. This reveals different bond breaking mechanisms, where large numbers of fragments are only observed for crystalline phase change materials (PCMs). This finding is related to the recently conjectured mechanism of metavalent bonding. Instead, amorphous PCMs, other covalently bonded compounds, and metals form much fewer fragments.