Open Access Nano Express

Influence of Cobalt Doping on the Physical Properties of Zn0.9Cd0.1S Nanoparticles

Sonal Singhal12, Amit Kumar Chawla1, Hari Om Gupta2 and Ramesh Chandra1*

Author Affiliations

1 Nanoscience Laboratory, Institute Instrumentation Center, Indian Institute of Technology Roorkee, Roorkee, 247667, India

2 Department of Electrical Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, India

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Nanoscale Research Letters 2009, 5:323-331  doi:10.1007/s11671-009-9483-7

Published: 17 November 2009

Abstract

Zn0.9Cd0.1S nanoparticles doped with 0.005–0.24 M cobalt have been prepared by co-precipitation technique in ice bath at 280 K. For the cobalt concentration >0.18 M, XRD pattern shows unidentified phases along with Zn0.9Cd0.1S sphalerite phase. For low cobalt concentration (≤0.05 M) particle size, dXRDis ~3.5 nm, while for high cobalt concentration (>0.05 M) particle size decreases abruptly (~2 nm) as detected by XRD. However, TEM analysis shows the similar particle size (~3.5 nm) irrespective of the cobalt concentration. Local strain in the alloyed nanoparticles with cobalt concentration of 0.18 M increases ~46% in comparison to that of 0.05 M. Direct to indirect energy band-gap transition is obtained when cobalt concentration goes beyond 0.05 M. A red shift in energy band gap is also observed for both the cases. Nanoparticles with low cobalt concentrations were found to have paramagnetic nature with no antiferromagnetic coupling. A negative Curie–Weiss temperature of −75 K with antiferromagnetic coupling was obtained for the high cobalt concentration.

Keywords:
Cobalt doping; Paramagnetism; Quantum confinement