Electrodeposited Quantum Dots. 6. Epitaxial Size Control in Cd(Se, Te) Nanocrystals on {111} Gold

Golan, Yuval; Hatzor, Anat; Hutchison, J. L.; Rubinstein, Israel; Hodes, Gary

doi:10.1002/ijch.199700035

Cited by 9 publications

(5 citation statements)

References 20 publications

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“…The resulting 2:√7 supercell is characterized by a lattice mismatch of +0.13%. Similar structures have been observed in the electrodeposition of CdSe nanocrystals on Au(111) surfaces . The crystallites we observe are narrowly dispersed in diameter.…”

Section: Resultssupporting

confidence: 84%

“…Finally, micrometer-scale STM images indicate the formation of nanometer-scale ZnS crystallites which appears to be driven by lattice-mismatch induced strain. Rubinstein and Hodes have observed similar morphologies when CdSe is electrodeposited on Au(111) from a solution of CdSO 4 and elemental Se . In addition, Resch et al reported in situ studies of ZnS grown by the successive ionic layer adsorption and reaction (SILAR) method showing similar islandlike features …”

Section: Introductionmentioning

confidence: 90%

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A Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy Study of Electrochemically Grown ZnS Monolayers on Au(111)

1999

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The structure and chemical composition of electrosynthesized ZnS thin films on Au(111) substrates was studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). The films were grown by alternating underpotential deposition and oxidative adsorption cycles of S and Zn from solution precursors (electrochemical atomic layer epitaxy, EC-ALE). Oxidative adsorption of the first layer of S results in a ( × )R30° adlattice on Au(111). In the initial Zn monolayer, XPS indicates the presence of SO4 2- derived from the supporting electrolyte. The coadsorbed SO4 2- can be chemically or electrochemically displaced by H2S(aq) or HS(aq) -, leading to the formation of ZnS. Atomically resolved STM images show the ZnS/Au(111) monolayer to be 6-fold symmetric with an interatomic spacing of 0.37 ± 0.01 nm. The structure of the deposit on the micrometer scale was also investigated by STM. The first complete EC-ALE cycle results in the formation of nanocrystallites of ZnS randomly distributed across Au(111) terraces. The average diameter of the crystallites is 10 ± 5 nm, and the apparent coverage of ZnS is 0.38.

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Section: Resultssupporting

confidence: 84%

Section: Introductionmentioning

confidence: 90%

A Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy Study of Electrochemically Grown ZnS Monolayers on Au(111)

1999

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“…This is also supported by recent experiments on the control of QD size by "misfit tuning" in Cd(Se,Te) QDs on Au. 47 When the same procedure is repeated with Pd substrate (4.1% mismatch for the same structure), a-CdSe QDs are obtained, with no apparent size limitation. These amorphous QDs exhibit the same short-range-order elements as the crystalline QDs on Au and consist of <2.5 nm ordered domains showing a preferred epitaxial relationship with the Pd substrate.…”

Section: Discussionmentioning

confidence: 97%

Electrodeposited Quantum Dots. 3. Interfacial Factors Controlling the Morphology, Size, and Epitaxy

1996

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Electrodeposition of CdSe from nonaqueous solutions is shown to produce epitaxial, 5 nm diameter quantum dots (QDs) on evaporated {111}Au substrate and diffraction-amorphous QDs on evaporated Pd substrate. The QDs were characterized using bright-field and dark-field transmission electron microscopy (TEM), high-resolution TEM, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. It is shown that similar short-range-order elements are present in both the crystalline QDs on Au and the amorphous QDs on Pd. An epitaxial size-limiting mechanism is proposed for the CdSe QDs on Au, on the basis of growing mismatch-induced strain energy upon increase in the QD size, giving rise to arrays of “self-assembled” QDs. We show that this concept, previously demonstrated using MBE and MOCVD techniques, can be successfully applied to electrochemical deposition, resulting in homogeneous QDs of considerably smaller size.

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“…Increasing the QD lattice parameter by incorporation of small amounts of Te in the CdSe lattice leads to reduced mismatch-induced strain, and hence, to larger QD size, while partial substitution of Cd by Zn had the opposite effect. [4,6] Substituting {111} Au with {111} Pd (d {110} Pd = 0.2752 nm) as the substrate increases the lattice mismatch to 4.1 % (for the 3:2 ratio), resulting in diffraction-amorphous CdSe nanoparticles on top of an ultrathin CdSe film, both comprising extremely small (typically 1 nm) ordered CdSe clusters in an amorphous CdSe matrix. [3,5] Although the model assuming lattice mismatch as the major factor determining QD size has proven successful with most semiconductor/substrate pairs, in some cases, e.g., CdSe on Pd/ Au alloy and CdS on Pd, deviations from the expected behavior were observed.…”

Section: Introductionmentioning

confidence: 99%

Structural Effects in the Electrodeposition of CdSe Quantum Dots on Mechanically Strained Gold

Ruach-Nir¹,

Wagner²,

Rubinstein³

et al. 2003

Adv Funct Materials

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CdSe nanoparticles were electrodeposited on mechanically strained gold, the latter achieved by controlled bending of gold films evaporated on mica. It is shown that the size and bandgap of the electrodeposited CdSe quantum dots (QDs) can be varied by applying mechanical strain to the Au substrate during deposition. This is attributed to change in the lattice spacing of the strained {111} Au and consequently in the lattice mismatch between the Au and the CdSe. Negative mechanical strain promotes the formation of rocksalt (RS) CdSe nanocrystals, normally existing only at high pressures. This is attributed to surface tension compression in the small crystals, together with enhancement of the phase transition by the CdSe/substrate interface.

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Electrodeposited Quantum Dots. 6. Epitaxial Size Control in Cd(Se, Te) Nanocrystals on {111} Gold

Cited by 9 publications

References 20 publications

A Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy Study of Electrochemically Grown ZnS Monolayers on Au(111)

A Scanning Tunneling Microscopy and X-ray Photoelectron Spectroscopy Study of Electrochemically Grown ZnS Monolayers on Au(111)

Electrodeposited Quantum Dots. 3. Interfacial Factors Controlling the Morphology, Size, and Epitaxy

Structural Effects in the Electrodeposition of CdSe Quantum Dots on Mechanically Strained Gold

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