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  • Bhaskarjyoti Bodo, Nabajyoti Talukdar, P K Kalita / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1656-1659 Synthesis of CdS: Cu Nanorods For Application In Photonic Devices Bhaskarjyoti Bodo*, Nabajyoti Talukdar** & P K Kalita** *(Department of Physics, Diphu Govt. College, Diphu-782462, India ** (Nanoscience Research Laboratory, Department of Physics, Guwahati College, Guwahati-781021, IndiaABSTRACT : In our present work undoped CdS and CdS is one of the important electronicCu doped CdS thin films were deposited on glass materials which has a potential to use in thesubstrate by chemical bath method. XRD fabrication of various electronic devices such solaranalysis of the as-prepared sample indicated cell, photo sensor and electronic display screen [9].CdS:Cu nanorods to be mixture of two phases It has band gap 2.4eV and thereby have a tendencynamely hexagonal and cubic. It has been observed to nanostructure if it synthesis in proper matrix [8].that one particular plane (100) has preferentially Although many researchers have synthesized CdSgrown as the maximum intense peak whereas the nanostructure in thin films as well as colloidalother two planes (101) and (102) have powder, yet there has large scope in studying thediminished intensities indicating the highly doping effect on the optical properties of thisoriented growth of the particles. TEM image of material. The problem of doping is yet to be solved.CdS: Cu nanostructure shows the garland like The effects of external and internal doping in thenanorod structures that consist of the mixture of synthesis as well as the physics of doping pattern arecubic and hexagonal particles. Hexagonal yet to be understood. Hence more experimentalparticles confirm the hexagonal phase of the CdS. findings are desirable for modulating future deviceSome particles dispersed in hexagonal form are oriented optical properties. The chemical growth isweakly agglomerated. The size of the hexagonal quite easy and inexpensive for the synthesisstructure is in the range of 75-100nm. The compared to the other method. Keeping the aboveTEM image of the undoped CdS reveals the aspects, an experimental work on the chemicalsimilar hexagonal structure of those CdS synthesis of CdS and Cu doped CdS has been takennanoparticles. The UV_VIS spectra of Cu doped to study their structural and optical properties.CdS show the red shift of quantum confinementover undoped CdS. The additional long 2. SYNTHESIS: MATERIALS ANDwavelength absorptions shows that copper can METHODS:exists as different types of impurities such as The simple chemical both depositionreplacing host Cd in its lattice site as well as (CBD) method was employed to deposit Cu dopedinterstitials within the crystal lattice. CdS thin films on to glass substrates. The undoped CdS deposition was carried out in a matrix solutionKeywords – CdS:Cu, Nanorods, Nanoparticles, of equivolume and equimolar CdSO4 and thioureaTEM. in an alkaline medium. The solution of CdSO4 (0.5M) was prepared by dissolving CdSO4 in1. INTRODUCTION: deionised water. An aqueous solution of 3% Synthesis and characterization of discrete weight of poly-vinyl alcohol (PVA) was preparednanostructure is of significant importance because with constant stirring at constant room temperatureof their fundamental role in basic research and and kept overnight prior to the deposition. Thetechnological application [4]. Nanostructures of PVA solution was mixed with CdSO4 solutionmetal sulfide semiconductor such as CdS, ZnS and under constant stirring to form a well dispersedCuS etc have aroused much attention in recent years PVA capped Cd2+ion solution. Ammonia solutiondue to their unique electronic and optical properties was added slowly to the above matrix solution toand potential applications. [1-5]. It is reported that form the metallic complex. The P H was adjustedmetal doping on such semiconductor results the between 10 and 12. The thiourea as S2- ion sourceformation of the different types of nanostructures was then added to the metallic complex solutionwith novel properties[5] and increase surface to drop by drop to form colloidal solution of CdSvolume ratio in nanoparticles enhances surface and nanoparticles. For Cu doping, CuSO4 solution ofinterface effects resulting in novel phenomena [4-5]. 0.005M was mixed with the host CdSO4 (0.5M)Furthermore luminescence characteristic of metal solution prior to deposition and similar steps weredoping CdS nanocrystals differ markedly from those followed to have final CdS:Cu matrix solution.of the bulk CdS [11]. Commercially available glass slides were cleaned through boiling in chromic acid, rinsed with distilled 1656 | P a g e
  • Bhaskarjyoti Bodo, Nabajyoti Talukdar, P K Kalita / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1656-1659water and dried in air. The glass slides were dipped hexagonal and cubic [6, 8]. Considerablein the final matrix solution for 48-56 hours to cast broadening is evident from the XRD data [6]. It hasthin films. been observed that one particular plane (100) has preferentially grown as the maximum intense peaks3. CHARACTERIZATION: whereas the other two planes (101) and (102) have These thin films were taken for XRD study diminished intensities attributing one dimensionaland the solutions were used for optical as well as growth of CdS nanostructures [6]. For Cu dopedTEM studies. The structural investigation of CdS CdS, Cu and Cu related phases are not detectedand CdS:Cu was carried out using X-ray powder which implies the homogeneity of compound. F.diffractometer (Model: Seifert XRD 3003 T/T) with Atay et al reported that the reasons of suchCuKα radiation (λ =0.15406nm) scanning 2θ in the undetection are the little amount of Cu in the thinrange 200-800. The morphology of the nanoparticles films and the sensitivity of the XRD [8]. Howeverwere characterized by transmission electron the low amount of dopant concentration is enough tomicroscope (TEM) [Model: JEOL JEM 100CX-II] bring noval optical properties [5, 6, 11]. Theoperated with an acceleration potential of 100 kV. crystalline size of the as-synthesised Cu doped CdSThe UV-Visible absorption of the samples was nanostructures have been calculated using therecorded using an automated spectrometer (Model: Scherer equation from FWHM values of the peakHITACI 113210) in the wavelength range 200nm - corresponding to (200) with a 2θ =30.15 0 and is800nm. around 9 nm. Similarly the estimation of crystalline size of CdS nanostructure is around 4nm indicating4. EXPERIMENTAL RESULTS AND DISCUSSION: the formation of quantum dots particles.4.1. XRD STUDY: 4.2 TEM STUDY: The X-ray diffraction (XRD) of The figure 2(a) representing TEMnanocrystallines CdS and of CdS doped with Cu2+ (Transmission Electron Microscope) image of CdSare shown in the figure – 1(a) and 1(b) respectively. nanostructure shows the hexagonal type particlesAnalysis of the XRD indicated CdS nanorods to be which confirm the hexagonal phase of the CdS. Itmixture of two phases namely can be seen that CdS particle are well dispersed in hexagonal form [9]. Some particles are weakly agglomerated due to the large amount of particles presented.Fig 1(a). XRD of CdS (0.5M)PVA . Fig. 2(a). TEM image of CdS (0.5M) PVA Fig. 2(b) and(C).TEM image of CdS :Cu(0.5M) nanorodsFig 1.(b). XRD of CdS;Cu (0.1M) PVA 1657 | P a g e
  • Bhaskarjyoti Bodo, Nabajyoti Talukdar, P K Kalita / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1656-1659in the TEM image. The size of the hexagonal the electronic state in the conduction band and holestructure is in the range of 75-100nm state in the valence band is given in the TABLE-1. From the absorption peaks the optical energy band The figures 2(b) and 2(c) display the TEM gap of CdS and CdS:Cu have been calculated usingimage of Cu doped CdS nanoparticles in different the formulamagnification. In TEM image, the CdS:Cu phosphorexhibits the similar hexagonal structure of those “Egn=hvgn = hc/ λgn” ............. (1)CdS nanoparticles [15] . However, the hexagonalstructure formed a garland like nanorods structures where h = plank’s constant, Egn = enrgyas similar to determined by other report[8]. The band gap of the semiconducting nanoparticles in thenanorods consist of hexagonal particles of optical spectra and the calculated band gap energyindividual size in the range of 100 to 125 nm. The are shown in the TABLE-1. Band gap energy of Cufigure 2(c) in higher resolution shows the formation doped CdS is decreased as compared to that of CdSof fine garland like nanorods structure with nanoparticles attributing the structural and opticalhexagonal arrangement of the individual particles changes. In CdS:Cu film additional absorption lie onwith mixture of cubic structures. These particles are the long wavelength 526nm, 615nm and 725nm.uniform with side chain agglomeration and the This is attributed to the presence of energy levelsaverage width and length of garland are 55nm and within the forbidden gap due to Cu as different type450 nm respectively. Hence the Cu doping initiated impurities [5]. In case of doping process, dependinga one dimensional growth type nanostructure in CdS upon the doping pattern, Cu may either replace Cdsemiconductors [6]. lattice site or as interstitial within the crystal lattice. Considering the band gap energy of bulk CdS as4.3 UV_VISIBLE STUDY: 2.34eV, large blue shift is observed in both CdS and Fig.-3(a) and Fig.-3(b) show the Cu doped CdS. This indicates a clear quantumUV_Visible absorption spectra of CdS and CdS:Cu confinement in PVA capped CdS nanostructures. C.respectively prepared in PVA matrix. The M. Janet et al reported that when the size of CdSabsorption peaks due to their transition between nanocrystal becomes smaller then the exciton radius a remarkable quantum size effect leads to a size dependent increase in the bandgap and a blue shift in the absorption onset [6]. From these TABLE:1. CALCULATION OF BAND ENERGY AND PARTICLES SIZES OF CdS and CdS: Cu (band gap (nm) (eV) Δ Egn (eV) D(diameter) gap energy) (Bulk band (blue shift) absorption Particles Samples Egn(eV) energy peak size nm Egb λgn CdS 309 4.04 2.34 1.7 5.7Fig.3 (a) Uv_Vis Absorption spectra of CdS (0.5) CdS: 350 3.53 2.34 1.19 6.8PVA. Cu Calculated blue shift values (TABLE-1) theoretical size of the nanoparticles can be determined by using Effective Mass Approximation (EMA) method. The formula in EMA calculation as derived by L.E.Brus is given as [12] “Δ Egn = π2 h2 /2R2/ ( 1/me +1/mh) -1.8e2/εR” ……………...(2) Where me = effective mass of the electron of the specimen, mh = effective mass of hole of theFig. 3(b). UV_VIS absorbance Spectra of CdS:Cu specimen, h =6.58 x 10-16 eV and R = radius of the(0.5M)PVA nanoparticle. The size of the particle (D) is given by D = 2R and the estimated sizes of CdS and CdS: Cu 1658 | P a g e
  • Bhaskarjyoti Bodo, Nabajyoti Talukdar, P K Kalita / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1656-1659are 5.7nm and 6.8nm (table-1) respectively which method , Journal of Magnetism andindicate quantum size effect. This increase of magnetic material, 320, 2008, 788-795.particle size decreases the band gap which shows a [5] Bhaskarjyoti bodo, P K Kalita , Chemicalclear red shift on Cu-doping. It is reported that the Synthesis of ZnS:Cu Nanosheets,increment in bandgap is approximately inversely AIP,Conf, proc. 1276, 2010, 31- 36.proportional to the square of the crystal size based [6] C M Janet and R P Viswanath, Large scaleon the effective mass approximation [13]. synthesis of CdS nanorods and its utilization in photo-catalytic H2production,5. CONCLUSION Nanotechnolgy 17, 2006, 5271-5277 [7] Zhu H, Yao K, Wo Y, Wang N and Wang CdS and Cu doped CdS have been L, A Hydrothermal synthesis of singlesynthesized successfully through chemical route and crystalline In(OH)3 nanorods and theirtheir respective sizes lie in the range of 5 nm~ 10nm characterization, 2004 Semicondor.Sc.which have inferred by XRD and TEM. XRD Technol. 19, 2004, 1020-1030.analysis of the as-prepared sample indicated CdS:Cu [8] F Atay et al , The investigation of Cunanorods to be mixture of two phases namely doped CdS films produced by ultrasonichexagonal and cubic. The TEM image shows the spray pyrolysis technique,formation of garland shaped CdS nanostructure. The J.optoelectronics and Advanced Materials,UV_Visible study reveals large blue shift both in 10(2), 2008, ,311-318.CdS and CdS:Cu nanoparticles indicating the strong [9] Anlian Pan et al Surface crystallizationquantum confinement. The additional long effects on the optical and electricwavelength absorptions shows that copper can exists properoties of CdS nanorods,as different types of additional impurities such as Nanotechnology, 16, 2005, 2402-2406.replacing host Cd in its lattice site as well as [10] Li Zhang, Dezhi Qin, Synthesis andinterstitials within the crystal lattice. The absorption Characterisation of CdS nanorods by theedge is red shifted with respects undoped CdS that Solvothermal Process with PVA as Matrix,indicate the increase of particle size from 5.7 to Chalcogenide Letters, 8, 2011, 349-353.6.8nm. Thus the Cu incorporated CdS nanostructure [11] M. Sima, I. Enculescu, A.Ioncea, T. Visan,can bring morphological, structural and optical C. Trautmann, Chalcogenide Letters, 1,properties changes. Hence such synthesized CdS:Cu 2004, 119-124nanorods have a great potential to be used in [12] L.E. Brus, Electronic wave function inphotonic device fabrication. semiconductor clusters-experiment and theory, J. Phys.Chem. 90, 1986, 2555-ACKNOWLEDGEMENTS 2560. The authors sincerely thank the SAIF, [13] Tong H and Zhu Y J , Synthesis of CdSNEHU (North East Hills University), Shillong and nanocystals based on low-temperatureDepartment of Physics, Tezpur University, Tezpur thermolysis of one single-sourefor providing the facilities for characterizations. organometallic precursor,Nanotechnology 17, 2006, 845-851.REFERENCES. [14] Klug H P and Leory EA X-Ray Diffraction [1] Hasanzadeh J.,& Farjami Shayateh, Optical Procedures ,(New York :Wiley),1974, and structural characterization of Cu doped 656-672. CdS nanoparticles, Eur.Phys.J. Appl Phys. [15] Sanjay R Dhage,Henry A Colorado and 51(3), 2010, 30601-30605. Thomas Halm, Morphological variations in [2] Aoneng Cao et al , A Facile One-step cadmium sulfide nanocrystals without Method to Produce Graphene-CdS phase transformation, Nanoscale Research Quantum Dot Nanocomposites as Letters 6, 2011, 420-424. Promising Optoelectronic Materials, Adv.Mater, 22, 2010, 103-106. [3] Young Wang et al Silica Coating of Water-Soluble CdTe /CdS Core-Shell Nanocrystals by Microemulsion Method,Chinese J. chem Phy ,.20(6), 2007, 685-689. [4] V. Srinivas, S K Barik, Bhaskarjyoti Bodo, Debjani Karmkar, T V Chandrasekhar, Magnetic and electrical properties of oxygen stabilized nickel nanofibers prepared by the borohydride reduction 1659 | P a g e