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Optical and Electrical Properties of CdTe Nanocrystal Quantum Dots Passivated in Amorphous TiO2 Thin Film Matrix

Published online by Cambridge University Press:  09 August 2011

A. C. Rastogi ,
S. N. Sharma  and
Sandeep Kohli
A. C. Rastogi
Affiliation:
alok@csnpl.ren.nic.in
S. N. Sharma
Affiliation:
Division of Electronic Materials, National Physical Laboratory, K. S.Krishnan Road, New Delhi 110 012, INDIA
Sandeep Kohli
Affiliation:
Division of Electronic Materials, National Physical Laboratory, K. S.Krishnan Road, New Delhi 110 012, INDIA
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Abstract

CdTe nanocrystal quantum dots sequestered in TiO2 thin film matrix have been synthesized by r.f. sputtering from a composite CdTe/TiO2 target. CdTe nanocrystal formation is nucleation controlled as their size (11-25 nm), dispersion and volume fraction (0.065-0.2) increases with film thickness, substrate temperature (100°C) and thermal treatment. The optical band gap derived from the onset of absorption coefficient showed blue shifts concurrent with the CdTe nanocrystal size reduction due to quantum size effects. These shifts, not consistent with theoretical models based on strong or weak confinement regimes, are explained on the basis of anisotropic growth and formation of CdTe nanocrystal clusters. TiO2, in addition to being an ideal passivator and providing a barrier for carrier confinement to observe quantum effects, shows O2 vacancy dependent conductivity modulation. Electrical conductivity variation with CdTe nanocrystal size and density is attributed to electrical coupling and tunneling behavior of carriers between CdTe nanocrystallites.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 536: Symposium F – Microcrystalline & Nanocrystalline Semiconductors - 1998 , 1998 , 263
Copyright
Copyright © Materials Research Society 1999

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