Characterization of Se-Te Nanostructured chalcogenide prepared by ball milling

Shamshad A. Khan^*,  A. A. Al-Ghamdi

Department of Physics, Faculty of Science

King Abdul Aziz University, Jeddah-21589, K. S. A.

ABSTRACT

Nanoparticles have been under intensive investigation in the past two decades because of their size-dependent properties and the possibility of arranging them in micro and nano assemblies. They are very interesting because of their unique physical and chemical properties and their potential applications in many fields. The nonlinear optical properties of semiconductor nanocrystals have attracted much attention because of their large optical nonlinearity and short response time. The size, shape and surface characteristics have a strong influence on the optical properties of nanocrystals. Therefore, much attention has been paid to controlling these parameters to manipulate the optical properties of nanomaterials. Nanostructure formation has been explored for many kinds of materials, and this becomes an interesting topic also for chalcogenides. Chalcogenide possesses unique characteristics which are different from those in oxide and halide glasses, i.e. molecular structures and semiconductor properties. However, studies on nano-chalcogenides are still at the beginning, and accordingly, overall features have not been discovered.Our present research work is concentrated with structural and optical studies of Se₈₈Te₁₂ chalcogenide nanoparticles. Bulk Se₈₈Te₁₂ chalcogenide material in polycrystalline form was prepared by the melt-quenching technique. The polycrystalline nature of the sample was confirmed by X-ray diffraction. The polycrystalline Se₈₈Te₁₂ chalcogenide material was used as a starting material. The ball milling was performed in a Laboratory 8000M-Mixer/Mill (SPEX) mill using hardened steel balls and a vial with a ball-to-powder weight ratio of 10:1. All handling of the powders during milling was performed in the glove box in an argon atmosphere. After various time of milling, a small amount of material was taken from the container to be characterized by XRD, Transmission Electron Microscopy and optical measurements with in the wavelength region 400-1000 nm. From XRD measurements it was found that polycrystalline stage is also achieved during the milling process. TEM measurements showed that after 30, 40 and 70 hours of milling time, chalcogenide nanoparticles of different sizes were developed. By increasing the milling time, the size of the particles reduces more. The optical band gap and optical constants of the milled materials have been studied as a function of photon energy. Optical absorption measurements indicate that the absorption mechanism is due to indirect transition. It has been observed that the absorption coefficient increases lineally with the increase in photon energy and the optical band gap increases with the increase of milling time. 

Keywords:      Chalcogenides, ball milling, optical band gap, mechanical alloying,

X-ray diffraction, nanoparticles

* Corresponding author:

Dr. shamshad Ahmad Khan

Assistant Professor, Department of Physics, Faculty of Science

King Abdul Aziz University,Jeddah-21589, K. S. A.

e. mail:              shamshad_phys@yahoo.com