Reconstructing a solid-solid phase transformation pathway in CdSe nanosheets with associated soft ligands.
Integrated single-crystal-like small and wide-angle X-ray diffraction images of a CdSe nanosheet under pressure provide direct experimental evidence for the detailed pathway of transformation of the CdSe from a wurtzite to a rock-salt structure. Two consecutive planar atomic slips [(001) {110} in parallel and (102) {101}with a distortion angle of ∼40°] convert the wurtzite-based nanosheet into a saw-like rock-salt nanolayer. The transformation pressure is three times that in the bulk CdSe crystal. Theoretical calculations are in accord with the mechanism and the change in transformation pressure, and point to the critical role of the coordinated amines. Soft ligands not only increase the stability of the wurtzite structure, but also improve its elastic strength and fracture toughness. A ligand extension of 2.3 nm appears to be the critical dimension for a turning point in stress distribution, leading to the formation of wurtzite (001)/zinc-blende (111) stacking faults before rock-salt nucleation.
Wang
Zhongwu
Z
Cornell High Energy Synchrotron Source, Wilson Laboratory, Cornell University, Ithaca, NY 14853, USA.
Wen
Xiao-Dong
XD
Hoffmann
Roald
R
Son
Jae Sung
JS
Li
Ruipeng
R
Fang
Chia-Chen
CC
Smilgies
Detlef-M
DM
Hyeon
Taeghwan
T
D019187:Cadmium Compounds / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization; D004548:Elasticity; D008024:Ligands; D008958:Models, Molecular; D008962:Models, Theoretical; D049329:Nanostructures / Q000737:chemistry*; D044367:Phase Transition; D011312:Pressure; D018036:Selenium Compounds / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry
D019187:Cadmium Compounds; D008024:Ligands; D018036:Selenium Compounds; C058667:cadmium selenide; D015032:Zinc