Determination of density of states, conduction mechanisms and dielectric properties of nickel disulfide nanoparticles

F Sher,M A Rafiq,S S Batool,Arifa Jamil

doi:10.1063/1.4952966

Abstract

Temperature and frequency dependent ac electrical measurements were used to explore density of states, conduction mechanisms and dielectric properties of nickel disulfide (NiS2) nanoparticles. The NiS2 nanoparticles were prepared by conventional one step solid state reaction method at 250 °C. X-ray diffraction (XRD) confirmed cubic phase of prepared nanoparticles. Scanning electron microscope (SEM) images revealed presence of irregular shaped nanoparticles as small as 50 nm. The ac electrical measurements were carried out from 300 K to 413 K. Two depressed semicircular arcs from 20 Hz to 2 MHz showed presence of bulk and grain boundary phases in NiS2 nanoparticles at all temperatures. Small polaron hopping conduction from 300 K to 393 K and correlated barrier hopping conduction mechanism at temperatures higher than 393 K was observed. High value of density of states (of the order of 1024 eV−1cm−3) was calculated from ac conductivity. At low frequencies high values (of the order of 104-107) of real part of dielectric constant (ε′) were observed at different temperatures. These observations suggest that NiS2 nanoparticles may find applications in electronic devices.

Highlights

Fabrication of nanoscale inorganic materials are of great interest and importance due to their significance in basic scientific research and prospective technological applications.[1,2] Nickel sulfide has attracted considerable attention because of its unique optical, magnetic, electrical and catalytic properties.[3,4] Nickel sulfide can be prepared by different methods, such as vapor phase reaction,[5] hydrothermal,[6] ultrasonic irradiation[7] and solvothermal.[8]
At low frequencies high values of real part of dielectric constant (ε′) were observed at different temperatures. These observations suggest that NiS2 nanoparticles may find applications in electronic devices
Temperature and frequency dependent ac electrical measurements were carried out to determine the density of states, conduction mechanism and dielectric properties of NiS2 nanoparticles

Summary

INTRODUCTION

Fabrication of nanoscale inorganic materials are of great interest and importance due to their significance in basic scientific research and prospective technological applications.[1,2] Nickel sulfide has attracted considerable attention because of its unique optical, magnetic, electrical and catalytic properties.[3,4] Nickel sulfide can be prepared by different methods, such as vapor phase reaction,[5] hydrothermal,[6] ultrasonic irradiation[7] and solvothermal.[8] A variety of compositions including NiS, NiS2, Ni3+xS2, Ni4S3+x, Ni6S5, Ni9S8, Ni7S6, Ni3S4 and Ni3S2 can be obtained by varying synthesis process.[3] Having long-term stability and abundant presence in earth, metal dichalcogenides with structure MX2 (where M = Fe, Mo, Co, Ni, and X = Se, S) are interesting materials to examine as well. Temperature and frequency dependent ac electrical measurements were carried out to determine the density of states, conduction mechanism and dielectric properties of NiS2 nanoparticles

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSION