The present work demonstrates the superhydrophobic and Surface Enhanced Raman Spectroscopy (SERS)... more The present work demonstrates the superhydrophobic and Surface Enhanced Raman Spectroscopy (SERS) active substrate performance of silver coated copper oxide (Ag@CuO) nanostructured thin films prepared by the SILAR process. Super hydrophobic substrates that combine super hydrophobic condensation effect and high enhancement ability of Ag@CuO nanoflowers are investigated for SERS studies. The possible growth mechanism for the formation of nanoflower arrays from nanospindles has been discussed. Morphology and crystallinity of the Ag@CuO thin films are confirmed using FESEM and XRD. The results obtained in the present study indicate that the as-deposited hydrophobic nanospindles structure converts to super hydrophobic nanoflower arrays on annealing at 200°C. The Ag@CuO super hydrophobic nanoflowers thin film based SERS substrates show highly enhanced Raman spectra with an EF value of 2.0×10(7) for (Rhodamine 6G) R6G, allowing a detection limit from a 10(-10)molL(-1) solution. The present study may provide a new perception in fabricating efficient super hydrophobic substrates for SERS, suggesting that the fabricated substrates are promising candidates for trace analysis of R6G dye and are expected to be widely used as highly sensitive SERS active substrates for various toxic dyes in the future.
International Conference on Advanced Nanomaterials Emerging Engineering Technologies, 2013
ABSTRACT Vacancy, void incorporation and Si-Hx configuration in hydrogenated amorphous silicon (a... more ABSTRACT Vacancy, void incorporation and Si-Hx configuration in hydrogenated amorphous silicon (a-Si:H) thin films was studied. Films were grown by Direct Current (DC), pulsed DC and Radio Frequency (RF) magnetron sputtering. Fourier Transform Infrared (FTIR) spectroscopic analysis has been carried out on the films and found that, the a-Si:H films grown by DC magnetron sputtering are of good quality compared to pulsed DC and RF deposited films. The effect of Substrate temperature (TS) on the total hydrogen concentration (CH), configuration of hydrogen bonding, density (decided by the vacancy and void incorporation) and the microstructure factor (R*) was studied. TS is found to be an active parameter in affecting the above said properties of the films. The films contain both vacancies and voids. At low hydrogen dilutions the films are vacancy dominated and at high hydrogen dilutions they are void dominated. It is found that TS favors monohydride (Si-H) bonding at the cost of dihydride (Si-H2) bonding. This dividing line is at CH=14 at.%H for DC sputter deposited films. The microstructure structure factor R* is found to be zero for as deposited DC films at TS=773K. The threshold CH for void dominated region is found to be CH=23 at.%H for RF, CH=18 at.%H for PDC and CH~14 at.%H for DC sputter deposited films.
... sputtering. TK Subramanyam a , G. Mohan Rao b and S. Uthanna Corresponding Author Contact Inf... more ... sputtering. TK Subramanyam a , G. Mohan Rao b and S. Uthanna Corresponding Author Contact Information , E-mail The Corresponding Author , a. a Department of Physics, Sri Venkateswara University, Tirupati 517502, India. ...
All solid state batteries are essential candidate for miniaturizing the portable electronics devi... more All solid state batteries are essential candidate for miniaturizing the portable electronics devices.
ABSTRACT In the present investigation, Al2O3 thin films were deposited onto Si < 100 &... more ABSTRACT In the present investigation, Al2O3 thin films were deposited onto Si < 100 > substrates by DC reactive magnetron sputtering. The films were annealed in vacuum for one hour at 623, 823 and 1023 K. The composition of the films was quantitatively estimated using X-ray photoelectron spectroscopy (XPS) and the O/Al ratio was found be in the range 1.19 to 1.43. Grazing incidence X-ray diffraction (GIXRD) results revealed that the annealed films are amorphous in nature. Cross sectional transmission electron microscopy (X-TEM) analysis was carried out to study the microstructure and nature of the Al2O3-Si interface as a function of post-deposition annealing. TEM results revealed the presence of nanocrystalline gamma-Al2O3 in the annealed films and an amorphous interface layer was observed at the Al2O3 Si interface. The thickness of the amorphous interface layer was determined from the TEM analysis and the results are discussed.
The problems in measuring thermal emittance by steady-state calorimetric technique have been anal... more The problems in measuring thermal emittance by steady-state calorimetric technique have been analyzed. A few suggestions to make it more accurate, simple, and rapid have been discussed and results are presented.
An electron cyclotron resonance (ECR) plasma source (10 cm in diameter) has been developed for io... more An electron cyclotron resonance (ECR) plasma source (10 cm in diameter) has been developed for ion assisted sputter deposition of thin films. Variation of plasma parameters like ion density, electron temperature, plasma potential, and floating potential as a function of pressure and microwave power has been studied using Langmuir probe analysis. The ECR source gives an ion density of 1.01×1011/cm3 at a distance of 8 cm from the source exit at a pressure of 8×10−4 mbar and 400 W of microwave power. The uniformity of the plasma parameters at the substrate position was found to be ±2% over a diameter of 12 cm. Thin films of copper and silicon nitride have been deposited by rf sputtering in the presence of ECR plasma. The properties showed a significant change at an ECR power of 100 W.
Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effe... more Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effect of the ratio of nitrogen partial pressure to the total pressure during deposition and the substrate bias on the tungsten nitride formation has been studied. The glow discharge characteristics of the process have been studied in order to determine the deposition parameters. It is observed that nitrogen partial pressure ratio 0.4 and cathode current of 200mA favors the formation of the W2N films. The variation in the electrical resistivity of the ...
The present work demonstrates the superhydrophobic and Surface Enhanced Raman Spectroscopy (SERS)... more The present work demonstrates the superhydrophobic and Surface Enhanced Raman Spectroscopy (SERS) active substrate performance of silver coated copper oxide (Ag@CuO) nanostructured thin films prepared by the SILAR process. Super hydrophobic substrates that combine super hydrophobic condensation effect and high enhancement ability of Ag@CuO nanoflowers are investigated for SERS studies. The possible growth mechanism for the formation of nanoflower arrays from nanospindles has been discussed. Morphology and crystallinity of the Ag@CuO thin films are confirmed using FESEM and XRD. The results obtained in the present study indicate that the as-deposited hydrophobic nanospindles structure converts to super hydrophobic nanoflower arrays on annealing at 200°C. The Ag@CuO super hydrophobic nanoflowers thin film based SERS substrates show highly enhanced Raman spectra with an EF value of 2.0×10(7) for (Rhodamine 6G) R6G, allowing a detection limit from a 10(-10)molL(-1) solution. The present study may provide a new perception in fabricating efficient super hydrophobic substrates for SERS, suggesting that the fabricated substrates are promising candidates for trace analysis of R6G dye and are expected to be widely used as highly sensitive SERS active substrates for various toxic dyes in the future.
International Conference on Advanced Nanomaterials Emerging Engineering Technologies, 2013
ABSTRACT Vacancy, void incorporation and Si-Hx configuration in hydrogenated amorphous silicon (a... more ABSTRACT Vacancy, void incorporation and Si-Hx configuration in hydrogenated amorphous silicon (a-Si:H) thin films was studied. Films were grown by Direct Current (DC), pulsed DC and Radio Frequency (RF) magnetron sputtering. Fourier Transform Infrared (FTIR) spectroscopic analysis has been carried out on the films and found that, the a-Si:H films grown by DC magnetron sputtering are of good quality compared to pulsed DC and RF deposited films. The effect of Substrate temperature (TS) on the total hydrogen concentration (CH), configuration of hydrogen bonding, density (decided by the vacancy and void incorporation) and the microstructure factor (R*) was studied. TS is found to be an active parameter in affecting the above said properties of the films. The films contain both vacancies and voids. At low hydrogen dilutions the films are vacancy dominated and at high hydrogen dilutions they are void dominated. It is found that TS favors monohydride (Si-H) bonding at the cost of dihydride (Si-H2) bonding. This dividing line is at CH=14 at.%H for DC sputter deposited films. The microstructure structure factor R* is found to be zero for as deposited DC films at TS=773K. The threshold CH for void dominated region is found to be CH=23 at.%H for RF, CH=18 at.%H for PDC and CH~14 at.%H for DC sputter deposited films.
... sputtering. TK Subramanyam a , G. Mohan Rao b and S. Uthanna Corresponding Author Contact Inf... more ... sputtering. TK Subramanyam a , G. Mohan Rao b and S. Uthanna Corresponding Author Contact Information , E-mail The Corresponding Author , a. a Department of Physics, Sri Venkateswara University, Tirupati 517502, India. ...
All solid state batteries are essential candidate for miniaturizing the portable electronics devi... more All solid state batteries are essential candidate for miniaturizing the portable electronics devices.
ABSTRACT In the present investigation, Al2O3 thin films were deposited onto Si < 100 &... more ABSTRACT In the present investigation, Al2O3 thin films were deposited onto Si < 100 > substrates by DC reactive magnetron sputtering. The films were annealed in vacuum for one hour at 623, 823 and 1023 K. The composition of the films was quantitatively estimated using X-ray photoelectron spectroscopy (XPS) and the O/Al ratio was found be in the range 1.19 to 1.43. Grazing incidence X-ray diffraction (GIXRD) results revealed that the annealed films are amorphous in nature. Cross sectional transmission electron microscopy (X-TEM) analysis was carried out to study the microstructure and nature of the Al2O3-Si interface as a function of post-deposition annealing. TEM results revealed the presence of nanocrystalline gamma-Al2O3 in the annealed films and an amorphous interface layer was observed at the Al2O3 Si interface. The thickness of the amorphous interface layer was determined from the TEM analysis and the results are discussed.
The problems in measuring thermal emittance by steady-state calorimetric technique have been anal... more The problems in measuring thermal emittance by steady-state calorimetric technique have been analyzed. A few suggestions to make it more accurate, simple, and rapid have been discussed and results are presented.
An electron cyclotron resonance (ECR) plasma source (10 cm in diameter) has been developed for io... more An electron cyclotron resonance (ECR) plasma source (10 cm in diameter) has been developed for ion assisted sputter deposition of thin films. Variation of plasma parameters like ion density, electron temperature, plasma potential, and floating potential as a function of pressure and microwave power has been studied using Langmuir probe analysis. The ECR source gives an ion density of 1.01×1011/cm3 at a distance of 8 cm from the source exit at a pressure of 8×10−4 mbar and 400 W of microwave power. The uniformity of the plasma parameters at the substrate position was found to be ±2% over a diameter of 12 cm. Thin films of copper and silicon nitride have been deposited by rf sputtering in the presence of ECR plasma. The properties showed a significant change at an ECR power of 100 W.
Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effe... more Tungsten nitride thin films were deposited using unbalanced magnetron sputtering system. The effect of the ratio of nitrogen partial pressure to the total pressure during deposition and the substrate bias on the tungsten nitride formation has been studied. The glow discharge characteristics of the process have been studied in order to determine the deposition parameters. It is observed that nitrogen partial pressure ratio 0.4 and cathode current of 200mA favors the formation of the W2N films. The variation in the electrical resistivity of the ...
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Papers by G. Mohan Rao