Fig. 1: Structural characteristics of conventional bonded heterostructure interfaces.

a, Schematic illustrations of bonded heterostructure interfaces: a lattice-matched interface (top) and a lattice-mismatched interface (bottom). b, Cross-sectional image of a lattice-matched interface (STO/LSMO; STO, SrTiO₃; LSMO, La_0.7Sr_0.3MnO₃) grown using pulsed laser deposition, with low interfacial strain and one-to-one chemical bonds. Image adapted from ref. ⁴ with permission from PNAS. c, Cross-sectional image of InAs/AlSb interfaces grown using MBE, with clear interface strains. Image adapted from ref. ⁶ with the permission of AIP Publishing. d, Cross-sectional image of a III-Sb/Si interface grown using MBE. Misfit dislocations are observed owning to the lattice mismatch. Image adapted from ref. ⁷ with permission from Elsevier. e, Cross-sectional image of GaN(AlN)/AlN/Si superlattice grown by MOCVD. Threading dislocations are observed owing to large lattice mismatch. Image adapted from ref. ⁸ with permission from IOP Publishing. f, Cross-sectional image of a HfO₂/Si interface fabricated using ALD. Poor nucleation is observed on the H-terminated silicon surface with discontinuous HfO₂ islands. Image adapted from ref. ⁹ with permission from Elsevier. g, Cross-sectional image of Ti/Si interface fabricated using high vacuum deposition, with a glassy interfacial layer. Image adapted from ref. ¹¹ with permission from Elsevier.