from the MnSe. As the power increased the intensity of the samples increases up to a certain power then decreases due to the high impact of the power that.
Power dependent phonon frequency within CdSe and CdMnSe nanosheets Oindrila Halder and S. Rath
Citation: AIP Conference Proceedings 1832, 090048 (2017); doi: 10.1063/1.4980601 View online: http://dx.doi.org/10.1063/1.4980601 View Table of Contents: http://aip.scitation.org/toc/apc/1832/1 Published by the American Institute of Physics
Power dependent Phonon Frequency within CdSe and CdMnSe Nanosheets Oindrila Halder1 and S. Rath1 School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Jatni -752 050, Khurda, India. Abstract. The trend of tuning transitional materials in semiconductors is advancing everyday research. The composite behavior exhibited by doped nanoparticles is governed by many factors. These can either improve or adversely affect the desired electronic properties. In this work we have compared the Raman Scattering study of different power dependent excitations on CdSe nanosheets and manganese doped CdSe nanosheets and delved into the possibilities of their different electronic structures due to the phonon contribution. Keywords: CdSe, Raman Scattering, Power. PACS: 78.40.Fy,
INTRODUCTION
Synthesis of CdSe and Mn Doped Nanosheets
The II-VI semiconductors nanostructures (SNPs) and their unique characteristics have provided diverse of optoelectronic applications throughout decades. Extensive studies have been done on the synthesis and their anisotropic dependent behavior [1]. But synthesizing SNPs are still challenging from the aspect of desired behavior of their electronic states contributing to the phonon couplings. It becomes even interesting when impurities like manganese (Mn) are induced to challenge their excitonic states. As a result of potential applications in spintronics, numerous experiments and theoretical studies suggest that there is induced phonon confinement contributing to the interesting behavior in the lattice structure of different anisotropic system [2]. The strong interaction between the s, p-d exchange band carriers and d-electrons of Mn2+ ions results in a very large splitting of the spin levels under an applied high frequency source. Conversely, Raman scattering is the most important non-destructive tool to study both the lattice structures and their phonon contributions in a system. Thus, reporting the different power dependent excitation study with Raman scattering on Mn doped cadmium selenide nanosheets (CdSe NS).
Atomically thin manganese (Mn) doped cadmium selenide (CdSe) nanosheets (NS) were produced by a chemical growth technique, analogous to that of CdSe NS with a slight modification in the method carried out in reference [3]. Manganese chloride (MnCl2) was used as the source of Mn at the nucleation time of the synthesis. The stoichiometric amount of CdCl2 (1-X) and MnCl2(x) was mixed with the surfactant octylamine, and then heated at 393 K for 2 hrs. Hexane was added to precipitate the concoction and Cd(1X)Mn(x) powder was obtained by centrifuging. Selenium powder was then added to the Cd(1X)Mn(x) powder with the surfactant again and mixed to heat the solution at 423 K for 24 hrs. Finally, to obtain the Cd(1-X)Mn(x)Se (CdMnSe) NS, the solution was washed thoroughly with excess of ethanol containing trioctylphosphine, which is used to eliminate the unreacted Se and collected again by centrifugation.
EXPERIMANTAL
UV-Visible absorption measurements were carried out on an UV-1800, Shimadzu UV-Vis Spectrophotometer with UV Probe software (highest resolution 1nm). Measurements were taken at room temperature dispersed in chloroform.
This section consists of sample preparation and different characterization techniques.
Ultraviolet-Visible Absorption (UV-Vis)
DAE Solid State Physics Symposium 2016 AIP Conf. Proc. 1832, 090048-1–090048-3; doi: 10.1063/1.4980601 Published by AIP Publishing. 978-0-7354-1500-3/$30.00
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with excitation wavelength as 488 nm from Argon ion laser source focusing through 50μ lens. Before measurement, the instrument was calibrated for single crystal Silicon. Samples were dip coated on quartz substrate for the measurements.
RESULTS AND DISCUSSIONS
FIGURE 1. UV-Vis Spectra of CdSe (red), Mn dope CdSe (black).
Raman Spectroscopy
The role of Mn modified electronic structures was also studied by performing optical absorption spectroscopy and x-ray diffraction. Figure 1 shows the UV-Vis absorption spectra of CdSe Ns and Mn dope CdSe. The spectra shows the multivalent contribution of the Mn doping by giving a slight curve around 400nm and also by reducing the tailing effect which is clearly observed in the CdSe absorption spectra.
Raman scattering measurements were obtained using the T64000 Horiba Scientific Raman system
a
b
FIGURE 2. D 5DPDQVSHFWUDRI&G6HQDQRVKHHWVDWȜ QP, power 160mW and 200mW, (b) Raman spectra of Mn doped &G6HQDQRVKHHWVDWȜ QPSRZHUP:, 160mW, 200mW, 240mW.
The vibration properties of the CdSe Ns and Mn dope CdSe Ns were observed from Raman scattering Spectrum shown in fig 1. The excitation wavelength was fixed to 488nm and the power of the Argon ion laser was varied and observed the behavioral change in the lattice structures. The power was varied from 120mW to 240mW. In fig 2(a), the CdSe characteristic longitudinal optical (LO) peaks were observed at ~205cm-1 and their 2LO at ~410cm-1. These are downshifted according to the bulk CdSe Raman modes [3]. The transverse optical (TO) phonon modes ~178cm-1 and ~300cm-1 are comparatively weaker than the LO peaks. Thus, confirming the uniformity and smoothness of the NS crystal lattice. Whereas, in Mn dope CdSe NS in fig 1(b) shows multiple peaks denoting as the two CdSe NS characteristic peaks ~~205cm-1 and ~410cm-1. The
other peaks like ~175cm-1, ~235cm-1, ~300cm-1 are the TO phonon modes which is been shifted from the bulk mode ~171cm-1. This refers to induced strain along the transverse axis which is much confined in nanosheets, confirming the anisotropic effect on the phonons. The peak ~278cm-1 and ~300cm-1 arise from the MnSe. As the power increased the intensity of the samples increases up to a certain power then decreases due to the high impact of the power that might be distressing the lattice crystals to reduce the intensity drastically [4-6]. In conclusion, we report on doping of manganese in atomically thin cadmium selenide nanosheet were successful phenomenon, which practically enhanced the crystallinity and the electronic structure of the
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CdSe NS. These are all evidenced from the optical absorption and most importantly from Raman spectroscopy. Consequently, enlighten the path for future interest in the transition related extensive study within the Mn doped CdSe nanosheets.
ACKNOWLEDGMENTS We would like to thank Director, IIT Bhubaneswar for constant encouragement and advice. This work was supported by the IIT Bhubaneswar Central instrument facility CIF.
REFERENCES 1. V. M.Dzhagana et al, Nanotechnology 19, 305707 (2008). 2. Semiconductor Magnets: The Origin of Ferromagnetism, Kaili Zhang Literature Seminar September 18, (2014). 3. Halder et al, ,Appl. Phys. Lett, 104, 182109 (2014) 4. Bi, Jumon C C, V.Senthil Kuma, IJSTR, 5, 05, (2016) 5. V. S. Vinogradov, PHYSICS OF THE SOLID STATE, 50, 1(2008) 6. A.G. Rolo and M. I. Vasilevskiy, J. Raman Spectrosc., 38, 618(2007).
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