Superior Room Temperature Compressive Plasticity of Submicron Beta‐Phase Gallium Oxide Single Crystals

Abstract

Bulk‐scale (2¯$\bar{2}$01)‐oriented monoclinic beta‐phase gallium oxide (β‐Ga2O3) single crystals are brittle and fracture at low compressive strains. Here, it is reported that submicron β‐Ga2O3 pillars exhibit an exceptional room temperature plastic strain of up to ≈22% under compression. Deformation is observed in transition from brittle to superior plasticity with reduction of pillar size. The critical diameter for the brittle to ductile transition is ≈800 nm, attributed to the initiation of dislocation slip on the primary (400) slip planes. Below 500 nm, a second transition is reported to superior plastic deformation, achieved through the activation of secondary mechanisms due to both deconfinement and low crystalline symmetry of β‐Ga2O3, differentiating this finding from size‐effected plasticity of other brittle materials where plasticity is attributed to dislocation slip on primary slip planes. Molecular dynamics simulation supports the proposed mechanism of pillar deconfinement where plastic deformation in larger pillars is solely dominated by planar defects on (400) slip planes, while secondary defects are induced for sufficiently small pillars. No plasticity is observed for equally dimensioned pillars tested on a (010)‐oriented surface, highlighting the importance of presenting crystallography on submicron plasticity in this material.

Mechanical tailoring of dislocations in ceramics at room temperature: A perspective

“…Typically, nanoindentation tests 41 and micro‐/nanopillar tests 82 are employed to understand the plastic behavior (very often accompanied by cracking). For instance, quite some studies are published in the last two decades on micro‐/nanopillar compression, addressing the plastic deformation of carbides, 111 oxides, 112,113 and mainstream semiconductors such as Si 114 and GaAs 115 . A common observation is that, once the diameter of the pillars decreases below a critical value (e.g., ∼300 nm for Si 116 and ∼150 nm for dislocation‐free SrTiO 3 117 ]), plasticity sets in without fracturing the pillars and a large plastic strain can be achieved.…”

Low-temperature and flexible strategy to in-situ fabricate ZrSiO 4-based ceramic composites via doping and tuning solid-state reaction

“…The streaking of the diffraction spots in the FFT pattern (Fig. 8e, insert) suggested that a high density of stacking faults (SFs) was also generated within the nanoparticle [30].…”

“…9), abundant lattice ceramic and they thought that the SFs were actually formed at high temperatures due to drastic plastic deformation and the rapid cooling process "froze" the SFs [36]. Wu et al found that a large number of SFs were formed during the compression of single crystal β-Ga2O3, which enabled the material to obtain room temperature plasticity [30].…”

Reshaping Covalent Nanowires by Exploiting an Unexpected Plasticity Mediated by Deformation Twinning

“…al. [5] reported a brittle to plastic transition during compressive deformation at room temperature for monoclinic beta-phase gallium oxide (𝛽-Ga 2 O 3 ) single crystals with reduction of the pillar size below 800 nm. Mignerot et al [6] observed plastic deformation of InSb micronsized pillars during microcompression tests at room temperature and found stress-induced nano-twin formation.…”

“…al. [ 5 ] reported a brittle to plastic transition during compressive deformation at room temperature for monoclinic beta‐phase gallium oxide (β‐Ga 2 O 3 ) single crystals with reduction of the pillar size below 800 nm. Mignerot et al.…”