The growth of heteroepitaxially strained semiconductors at the nanoscale enables tailoring of material properties for enhanced device performance. For core/shell nanowires (NWs), theoretical predictions of the coherency limits and the implications they carry remain uncertain without proper identification of the mechanisms by which strains relax. We present here for the Ge/Si core/shell NW system the first experimental measurement of critical shell thickness for strain relaxation in a semiconductor NW heterostructure and the identification of the relaxation mechanisms. Axial and tangential strain relief is initiated by the formation of periodic a/2 ⟨110⟩ perfect dislocations via nucleation and glide on {111} slip-planes. Glide of dislocation segments is directly confirmed by real-time in situ transmission electron microscope observations and by dislocation dynamics simulations. Further shell growth leads to roughening and grain formation which provides additional strain relief. As a consequence of core/shell strain sharing in NWs, a 16 nm radius Ge NW with a 3 nm Si shell is shown to accommodate 3% coherent strain at equilibrium, a factor of 3 increase over the 1 nm equilibrium critical thickness for planar Si/Ge heteroepitaxial growth.

Dayeh, S., Tang, W., Boioli, F., Kavanagh, K., Zheng, H., Wang, J., et al. (2013). Direct measurement of coherency limits for strain relaxation in heteroepitaxial core/shell nanowires. NANO LETTERS, 13(5), 1869-1876 [10.1021/nl3022434].

Direct measurement of coherency limits for strain relaxation in heteroepitaxial core/shell nanowires

BOIOLI, FRANCESCA;MIGLIO, LEONIDA;
2013

Abstract

The growth of heteroepitaxially strained semiconductors at the nanoscale enables tailoring of material properties for enhanced device performance. For core/shell nanowires (NWs), theoretical predictions of the coherency limits and the implications they carry remain uncertain without proper identification of the mechanisms by which strains relax. We present here for the Ge/Si core/shell NW system the first experimental measurement of critical shell thickness for strain relaxation in a semiconductor NW heterostructure and the identification of the relaxation mechanisms. Axial and tangential strain relief is initiated by the formation of periodic a/2 ⟨110⟩ perfect dislocations via nucleation and glide on {111} slip-planes. Glide of dislocation segments is directly confirmed by real-time in situ transmission electron microscope observations and by dislocation dynamics simulations. Further shell growth leads to roughening and grain formation which provides additional strain relief. As a consequence of core/shell strain sharing in NWs, a 16 nm radius Ge NW with a 3 nm Si shell is shown to accommodate 3% coherent strain at equilibrium, a factor of 3 increase over the 1 nm equilibrium critical thickness for planar Si/Ge heteroepitaxial growth.
Articolo in rivista - Articolo scientifico
Nanowires
English
2013
13
5
1869
1876
none
Dayeh, S., Tang, W., Boioli, F., Kavanagh, K., Zheng, H., Wang, J., et al. (2013). Direct measurement of coherency limits for strain relaxation in heteroepitaxial core/shell nanowires. NANO LETTERS, 13(5), 1869-1876 [10.1021/nl3022434].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/44121
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