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Identification of surface states in PbS quantum dots by temperature dependent photoluminescence

Rao, K. S. R. Koteswara and Pendyalaa, Naresh Babu (2008) Identification of surface states in PbS quantum dots by temperature dependent photoluminescence. Journal of Luminescence, 128 (11). pp. 1826-1830.

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We report the type and nature of the surface states in PbS quantum dots grown in poly vinyl alcohol by the colloidal technique. Mercaptoethanol (C2H5OSH) capping and the molar ratio of Pb:S were used as parameters to understand the origin of the surface state related photoluminescence. From absorption and photoluminescence measurements, it was observed that increasing Lead concentration resulted in bigger nanoparticles with broad size distribution. However, the increase in sulfur concentration helped in the formation of smaller nanoparticles with narrow size distribution. Passivation studies also revealed that the origin of the bands below 1.1 eV was sulfur related. Thus these experiments indicated that sulfur played an important role, not only in size selectivity, but also in controlling defects in PbS quantum structures. Temperature dependent PL studies on different samples with various Pb:S molar ratios and with mercaptoethanol treated gave an insight into the nature of the surface states. Based on these results, we explain the origin of the surface states and proposed a model for different PL bands. The observed temperature-dependent trends of PL intensity (decreasing in Pb:S::1:1, increasing in S terminated and anomalous behavior in samples with excess of Pb) is attributed to the dominant mid-gap states and the results are consistent with carrier redistribution and recombination statistics involved in the quantum structures.

Item Type:Article
Subjects:Physical Science > Nanophysics
Physical Science > Nano objects
Physical Science > Quantum phenomena
Material Science > Nanostructured materials
Material Science > Nanochemistry
Divisions:Faculty of Engineering, Science and Mathematics > School of Physics
Faculty of Engineering, Science and Mathematics > School of Chemistry
ID Code:5029
Deposited By:JNCASR
Deposited On:27 May 2009 11:02
Last Modified:27 May 2009 11:02

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