SHAHEERA. M1, K. G. GIRIJA2, MANMEET KAUR3, V. GEETHA1, A. K. DEBNATH3, R. K. VATSA2, K. P. MUTHE3, S. C. GADKARI3 1Research Department of Physics, Government Victoria College, Palakkad, Kerala-678001 India 2Chemistry Division, 3Technical Physics Division, Bhabha Atomic Research Centre, Mumbai-400094 India Shaheera.M ([email protected]) MS received Short Title Visible photoluminescence emission from co-doped ZnO thin films Fig.2 shows the FESEM images of pristine and doped ZnO films. All the films have a dense, uniform, smooth and crack free microstructure. The morphology of ZnO and GZO has granular structure while IZO shows corn like structure. The grain size of the IGZO thin films is smaller than that of ZnO. This behavior was attributed to the various relationship between the nucleation, growth and activation energy of the thin films. The ionic radius inequality between Ga3, In3 and Zn2 in the lattice site of ZnO played a decisive role in the overall surface morphology modification of the films. Owing to the close ionic radius disparity between Ga3 and In3 , the compression in volume caused by gallium to the ZnO lattice is effectively compensated and counteracted by the tension in lattice caused by indium such that there will be less strain imposed in the lattice and fewer dislocations will be formed 15. As a result, IGZO films have better surface morphology than other films. 3.2 Elemental Analysis The weight of all elements of the thin films is studied with the help of EDS and summarized in Table.2. The associated spectrum obtained by EDS studies of all films are shown in Fig.3 (a-d). EDS studies confirm the presence of doped elements such as In, Ga, in ZnO. The amounts of doped element are found to be less than the actual amount of target composition. In order to understand the oxidation states of the deposited thin films, XPS analyses are performed and shown in Fig.4 and 5. The spectra are corrected using the C 1s line from adventitious aliphatic carbon (285 eV). It is seen that the O 1s and Zn 2p peaks of the doped ZnO thin films (Fig.4 (a) and (b)) shift towards higher binding energies compared to pristine ZnO thin films. This attributed to the formation of stronger bonds between the dopants (In Ga) and oxygen in doped thin films compared to those between Zn and oxygen in the pristine ZnO. The binding energy of the zinc 2p3/2 and 2p1/2 peaks (Fig.4.b) of all the films are consistently found to be 1020.2 0.2 eV and 1043.2 0.2) eV respectively which can be attributed to the Zn2 in ZnO 16. O1s spectra of all the films can be deconvoluted into 3 distinct sub peaks (I, II and III) using Gaussian fitting (Fig. 4. (a)) Among them, the low energy (region I) peak (529.4 ( 0.2 eV) originates from O2- ions forming bonds with the metal cations (Zn2,In3 and Ga3) in the lattice 17. The medium energy region II(530.4 ( 0.5 eV) components are associated with O2- ions near the oxygen deficient regions within the ZnO lattice 18 and region III (532.01( 0.5 eV) is due to the presence of loosely bound oxygen on the film surface belonging to a specific ratio such as CO3, adsorbed H2O or adsorbed oxygen 19. The In 3d and Ga 3d peaks are clearly seen from the XPS survey spectrum of IZO, GZO and IGZO thin films, indicating that In and Ga have indeed blended into the ZnO lattice. The gallium 3d5/2 peaks of GZO (Fig. 5 (b)) and IGZO films (Fig. 5 (c)) have binding energy (B.E) of 20.33 eV and 20.31 eV respectively, which is due to Ga3. Similarly, the indium 3d5/2 and 3d3/2 peaks of IZO (Fig.5 (a)) and IGZO (Fig.5 (d)) have B.E of 444.4 eV 451.5 eV and 444.9 eV 452.29 eV respectively, which is due to In3 9. 3.3 Optical properties 3.4 Photoluminescence spectra Acknowledgements The first and fourth authors would like to thank to the thin film devices group, Technical Physics Division at BARC, Mumbai for their help during the work. References Vinoth Kumar Jayaraman Arturo Maldonado Alvarez, Maria de la luz and Olvera Amador 2017 Physica E 86 164 Fang-Hsing Wang, Chiao-Lu Chang, 2016 Appl. Surf. Sci. 370 83 Dymitr Snigurenko, Elzbieta Guziewicz, Tomasz A Krajewski, Rafal Jakiela, Yevgen Syryanyy and Krzysztof Kopalko et al 2016 Mater. Res. Expres 125907 Shang-Chou Chang 2014 Nanoscale Res. Lett 9 562 Shang-Chou Chang, 2014 Inter. J. of Photoenergy 2014, 916189. D. Gaspara, L. Pereiraa, K. Gehrke, B. Galler, E. Fortunato and R. Martins, 2017 Sol. Energy Maters Sol. 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Express 1733 (10-2)ZnO34.1710.469117.7093.1890.30260.52410.26211.7320.1957IZO34.1160.729011.3947.7030.30310.52490.26251.7320.3042GZO34.1270.675712.2936.6170.30290.52480.26241.7320.282IGZO33.8110.759710.9258.3780.30570.52950.26481.7320.3173 Table 2. Compositional ratio of ZnO, IZO, GZO and IGZO thin films from EDS SampleZn (wt)O (wt)In (wt)Ga (wt)Total ZnO52.247.8–100IZO68.829.51.7-100GZO58.641-0.4100IGZO81.4180.40.2100 PAGE 104 Author PAGE 103 RH Bull. Mater. Sci., Vol. xx, No. x, Month 2017, pp. xxxxxx Indian Academy of Sciences DOI 10.1007/sxxxx-0xx-1xyz-8 PAGE 1 PAGE 4 Shaheera.M et al 4 3 5 Bull. Mater. Sci., Vol. 24, No. 1, February 2001, pp. 000000. Indian Academy of Sciences. PAGE 101 )kRosdXdffg_QvIV7UjklkiVStj_c6fO53g0K,nmYCVvz TTHba864/XLHEAArcORyS Smb MXHcJGq r.-7DTbV ,ivJ4Z-VDb GssD dx,VYyjRhAb74LYHw JgrpXg3HzBcrKBLlGU_Dq9 _e 4VIp)EUi ,(PB6kZAQYYQtc89Q)9utt)JzwnKoy
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