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V. Nirupama,K.R. Gunasekhar,B. Sreedhar,S. Uthanna 한국물리학회 2010 Current Applied Physics Vol.10 No.1
Molybdenum oxide films (MoO3) were deposited on glass and crystalline silicon substrates by sputtering of molybdenum target under various oxygen partial pressures in the range 8 × 10-5–8 × 10-4 mbar and at a fixed substrate temperature of 473 K employing dc magnetron sputtering technique. The influence of oxygen partial pressure on the composition stoichiometry, chemical binding configuration, crystallographic structure and electrical and optical properties was systematically studied. X-ray photoelectron spectra of the films formed at 8 × 10-5 mbar showed the presence of Mo6+ and Mo5+ oxidation states of MoO3 and MoO3-x. The films deposited at oxygen partial pressure of 2 × 10-4 mbar showed Mo6+ oxidation state indicating the films were nearly stoichiometric. It was also confirmed by the Fourier transform infrared spectroscopic studies. X-ray diffraction studies revealed that the films formed at oxygen partial pressure of 2 × 10-4 mbar showed the presence of (0 k 0) reflections indicated the layered structure of α-phase MoO3. The electrical conductivity of the films decreased from 3.6 × 10-5 to 1.6 × 10-6 Ω-1 cm-1, the optical band gap of the films increased from 2.93 to 3.26 eV and the refractive index increased from 2.02 to 2.13 with the increase of oxygen partial pressure from 8 × 10-5 to 8 × 10-4 mbar, respectively.
Fabrication of Photovoltaic Devices Using ZnO Nanostructures and SnS Thin Films
N. Koteeswara Reddy,mudusu devika,K.R. Gunasekhar,E. S. R. Gopal 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.7
The development of nontoxic and cost-effective solar cell devices is one of the challenging tasks even now. With this objective, solar cell devices using tin mono sulfide (SnS) thin films and zinc oxide (ZnO) nanostructures with a superstrate configuration of ITO/ZnO film/ZnO nanorods/ SnS film/Zn have been fabricated and their photovoltaic properties have been investigated. Vertically aligned ZnO nanostructures were grown on indium doped tin oxide substrate by chemical solution method and then, SnS thin films were deposited by thermal evaporation method. A typical solar cell device exhibited significant light conversion efficiency with an open circuit voltage and short circuit current of 350 mV and 5.14 mA, respectively.
D. Sreekantha Reddy,강병원,유성초,Y. Dwarakanadha Reddy,S.K. Sharma,K.R. Gunasekhar,K.N. Rao,P. Sreedhara Reddy 한국물리학회 2009 Current Applied Physics Vol.9 No.3
Nanostructured Zn1-xMnxS films (0 ≼ x ≼ 0.25) were deposited on glass substrates by simple resistive thermal evaporation technique. All the films were deposited at 300 K in a vacuum of 2 × 10-6 m bar. All the films temperature dependence of resistivity revealed semiconducting behaviour of the samples. Hot probe test revealed that all the samples exhibited n-type conductivity. The nanohardness of the films ranges from 4.7 to 9.9 GPa, Young’s modulus value ranging 69.7–94.2 GPa.
Sreekantha Reddy, D.,Kang, B.,Yu, S.C.,Dwarakanadha Reddy, Y.,Sharma, S.K.,Gunasekhar, K.R.,Rao, K.N.,Sreedhara Reddy, P. Elsevier 2009 Current Applied Physics Vol.9 No.2
Nanostructured Zn<SUB>1-x</SUB>Mn<SUB>x</SUB>S films (0=<x=<0.25) were deposited on glass substrates by simple resistive thermal evaporation technique. All the films were deposited at 300K in a vacuum of 2x10<SUP>-6</SUP>m bar. All the films temperature dependence of resistivity revealed semiconducting behaviour of the samples. Hot probe test revealed that all the samples exhibited n-type conductivity. The nanohardness of the films ranges from 4.7 to 9.9GPa, Young's modulus value ranging 69.7-94.2GPa.
Nandanapalli, Koteeswara Reddy,Mudusu, Devika,Lingandhinne, Raja Mohan Reddy,Mitta, Sekhar Babu,K. Reddy, Gunasekhar,Karuppannan, Ramesh,Whang, Dongmok Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.770 No.-
<P><B>Abstract</B></P> <P>Tin (II) sulfide (SnS), one of the most abundant materials, is being considered as an absorber material for the development of low-cost and nontoxic solar cell devices. In this direction, we have developed nanocrystalline films of SnS with uniform morphology on different substrates by adopting two-step thermal evaporation process. The surface studies show that irrespective of substrate nature, the as-grown SnS films possess uniform surface-morphology with well-defined facets. Structural studies reveal that SnS films grown on various substrates possess an orthorhombic crystal structure. However, as compared to other substrates, the structures developed on sapphire and copper exhibit 〈010〉 as preferential growth direction. From the electrical measurements, it is noticed that the films deposited on highly-conductive substrates consist of low electrical resistance, whereas the films are slightly resistive on insulating substrates. Based on these investigations it is emphasized that high-quality SnS films can be developed with uniform morphology on any substrates by adopting our two-step process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SnS films were developed with uniform morphology by using two-step process. </LI> <LI> The films grown on different substrates possess nanocrystallites with well-defined facets. </LI> <LI> These films consist of excellent chemical stoichiometry and phase purity. </LI> <LI> SnS films grown on different substrates have either 〈111〉 or 〈010〉 growth direction. </LI> </UL> </P>