Growth and characterization of ZnSe nanocrystals synthesized using solvothermal process
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Growth and characterization of ZnSe nanocrystals synthesized using solvothermal process Lalhriat Zuala1 · Pratima Agarwal2 Received: 4 June 2020 / Accepted: 17 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract ZnSe nanocrystals with zinc blende structure are synthesized by solvothermal process at 1-h, 3-h and 5-h reaction times in a mixed solvent of hydrazine hydrate [H6N2O], ammonia [NH3] and de-ionized water. Zinc acetate [(CH3COO)2 Zn; 2H2O] and sodium selenite [Na2SeO3] are, respectively, used as precursors for zinc and selenium ions. X-ray diffraction (XRD) and scanning electron microscope (SEM) study show that the crystallinity and the chemical purity of the compound improve with increase in reaction duration. SEM images show formation of bulk rod-shaped ZnO particles in samples prepared at 1-h and 3-h reaction times, which is absent in the 5-h sample. TGA measurements also show that the ZnSe nanocrystals synthesized in this process have high purity and the nanocrystals prepared for longer duration have improved purity as well as higher thermal stability. In Raman measurements, nanocrystalline nature such as surface phonon (SP) mode and phonon line width broadening are observed. The observed variation of the relative intensities of the phonon modes follows the differences in the size of nanocrystals, in which the relative strength of the transverse optical (TO) phonon mode is found to increase with nanocrystals size and the SP phonon relative strength on the other hand decreases.
1 Introduction ZnSe is a II–VI compound semiconductor with a bulk direct bandgap of 2.7 eV at room temperature [1, 2]. It has attracted considerable attention owing to its wide applications in diode laser [3, 4], green–blue light-emission [5, 6] and solar cells [7–9]. It is also a promising material for optical windows [10], sensors [11], non-linear optical devices [12], etc., due to high refractive index, large photoresistivity, non-toxicity and also due to its low absorptivity in the infrared and visible spectral region [13]. Nanostructured materials are known to exhibit interesting size and morphology-dependent physical properties, which are significantly different from its bulk properties [14]. Due to both higher surface-to-volume ratio and an increase in bandgap energy as a result of the quantum size effect, ZnSe nanostructured materials possess enhance photosensitivity * Lalhriat Zuala [email protected] 1
Physical Sciences Research Centre, Department of Physics, Pachhunga University College, Aizawl, Mizoram 796 001, India
Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781 039, India
2
and it enables the materials to be strong candidates for photovoltaic cells [7, 8], sensors [11], etc. For these reasons, synthesis of high-quality ZnSe nanocrystals and control of its size and morphology is a very important issue that still needs to be investigated for further technological development in implementation of ZnSe nanocrystals. Solvothermal metho
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