Experimental Revelation of Surface and Bulk Lattices in Faceted Cu2O Crystals
Journal
Small
Journal Volume
19
Journal Issue
44
ISSN
16136810
Date Issued
2023
Author(s)
Chen, Bo-Hao
Kumar, Gautam
Wei, Yu-Jung
Ma, Hsueh-Heng
Kao, Jui-Cheng
Chou, Po-Jung
Chuang, Yu-Chun
Chen, I-Chia
Lo, Yu-Chieh
Huang, Michael H.
Abstract
Semiconductor crystals have generally shown facet-dependent electrical, photocatalytic, and optical properties. These phenomena have been proposed to result from the presence of a surface layer with bond-level deviations. To provide experimental evidence of this structural feature, synchrotron X-ray sources are used to obtain X-ray diffraction (XRD) patterns of polyhedral cuprous oxide crystals. Cu2O rhombic dodecahedra display two distinct cell constants from peak splitting. Peak disappearance during slow Cu2O reduction to Cu with ammonia borane differentiates bulk and surface layer lattices. Cubes and octahedra also show two peak components, while diffraction peaks of cuboctahedra are comprised of three components. Temperature-varying lattice changes in the bulk and surface regions also show shape dependence. From transmission electron microscopy (TEM) images, slight plane spacing deviations in surface and inner crystal regions are measured. Image processing provides visualization of the surface layer with depths of about 1.5–4 nm giving dashed lattice points instead of dots from atomic position deviations. Close TEM examination reveals considerable variation in lattice spot size and shape for different particle morphologies, explaining why facet-dependent properties are emerged. Raman spectrum reflects the large bulk and surface lattice difference in rhombic dodecahedra. Surface lattice difference can change the particle bandgap. © 2023 Wiley-VCH GmbH.
Subjects
cuprous oxide
facet-dependent properties
pseudomorphic conversion
surface layer lattice
synchrotron X-ray diffraction
Publisher
John Wiley and Sons Inc
Type
journal article