Electrostatic Force Microscopy and Spectral Studies of Electron Attachment to Single Quantum Dots on Indium Tin Oxide Substrates

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• 作者：Sibel Ebru Yalcin ; Boqian Yang ; Joelle A. Labastide ; Michael D. Barnes
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：July 26, 2012
• 年：2012
• 卷：116
• 期：29
• 页码：15847-15853
• 全文大小：347K
• 年卷期：v.116,no.29(July 26, 2012)
• ISSN：1932-7455

文摘

We report electrostatic force microscopy (EFM) studies combined with wavelength-resolved photoluminescence imaging of electron attachment to individual CdSe/ZnS quantum dots (QDs) coupled to semiconducting tin-doped indium oxide (ITO) substrates. Quantitative EFM measurements show unambiguous signatures of 2鈥? excess electrons on individual QDs on ITO, while the distribution of measured recombination energies of QDs coupled to ITO shows 鈮?鈭?5 meV red shift (compared to QDs drop-cast on clean glass), the signature of a second-order quantum-confined Stark effect resulting from multiple-electron attachment to the QDs. We also show that the extent of QD charging can be tuned by modulating the ITO bias: EFM measurements show that 鈮? electrons are added to QDs under 鈭? V applied ITO bias, whereas only 鈮? electrons can be removed from the QDs for +2 V applied bias arising from Fermi level mismatch of ITO with respect to the QDs. Voltage-correlated spectral measurements on ITO coupled QDs showed a spectral modulation in their peak fluorescence energies, which can be attributed to addition or removal of electrons from the QDs.