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Chundi Seshendra Reddy,Liwen Zhang,Yejun Qiu,Yanan Chen,A. Sivasankar Reddy,P. Sreedhara Reddy,Sreekantha Reddy Dugasani 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.63 No.-
Graphene-based device/sensor made of multifunctional nanomaterials is an emerging technology due to its huge impact on the engineering materials. Herein, we report the synthesis of pristine SnO2, Al-doped SnO2 (Al–SnO2), and graphene-embedded Al–SnO2 (G–Al–SnO2) nanotubes by one-step electrospinning method and studied their physical and gas sensing characteristics. The synthesized tubular structure was confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Structural, chemical binding, pore size, and chemical composition/elemental states were estimated by the X-ray diffraction, Raman, BET, and X-ray photoelectron spectroscopy, respectively. The performance of the gas sensing based on SnO2, Al–SnO2, and G–Al–SnO2 materials for H2 detection was investigated, and the G–Al–SnO2 composite nanotubes exhibit the superior sensitivity at 300 °C. The sensing response reaches about 23.8 at H2 concentration of 100 ppm with a shorter response time of about 2.2 s and recovery time of about 1.4 s. The gas sensing performance of the G–Al–SnO2 nanotubes is much better than that of the pristine SnO2 and Al–SnO2 nanotubes, which is probably attributed to the relatively smaller diameter of about 100 nm, better thermal and electronic conductivity, and relatively high oxygen vacancy, induced by graphene and Al-doping. The prepared H2 sensor is a simple, compact and highly sensitive, which holds high promising in many fields.
Chundi Seshendra Reddy,A. Sivasankar Reddy,P. Sreedhara Reddy 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1
La0.7Ba0.3MnO3 (LBMO) thin films were deposited on Si substrates at various substrate temperatures (Ts) ranging from 823 K to 1023 K using electron beam evaporation (EBE), and studied the structural, composition and electrical properties of the films as a function of deposition temperature were studied. X-ray diffraction (XRD) studies revealed the epitaxial growth in the films. The surface morphology of the films were characterized by atomic force microscopy (AFM). The elemental composition analysis investigated by energy dispersive spectroscopy (EDS) confirmed the stoichiometry. The films deposited at higher substrate temperatures (1023 K), showed lower resistivity with a higher temperature coefficient of resistance (TCR). A TCR of 4.09%/K obtained in the present investigation is suitable for bolometric applications near to the room temperature.
A. Mallikarjuna Reddy,Chang Woo Byun,주승기,A. Sivasankar Reddy,P. Sreedhara Reddy 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.5
The influence of substrate temperature on the properties NiO films, prepared by dc reactive magnetron sputtering technique, is studied by various characterization methods. X-ray diffraction studies revealed that the crystal structure is highly influenced by the substrate temperature. The optical results indicated that the optical transmittance and band gap of the films increased with the increase of substrate temperature up to 523 K. The optical band gap of NiO films decreases from 3.82 to 3.70 eV with the increase of substrate temperature from 523 to 723 K. The electrical resistivity decreased with the increase of substrate temperature from 303 to 723 K, whereas carrier concentration and Hall mobility increased with increasing the substrate temperature.
SiO2/Si 및 Si 기판에 rf magnetron sputtering법으로증착된 적외선 센서용 La0.7Sr0.3MnO3 CMR 박막 저항체 특성연구
최선규,A.Sivasankar Reddy,유병곤,류호준,박형호 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.2
La0.7Sr0.3MnO3 박막을 rf 마그네트론 스퍼터를 이용하여 챔버 내 산소가스유량비를 0, 40, 80 sccm 으로 조절하고 후열처리 공정 없이 기판온도를 350℃로 유지하면서 SiO2/Si(100) 및 Si(100) 기판에 증착하였다. 증착된 La0.7Sr0.3MnO3 박막은 SiO2/Si(100), Si(100) 기판 모두 (100), (110), (200)면을 갖는 polycrystalline 상태였으며, oxygen flow rate이 증가함에 따라 박막의 grain size가 증가하였다. 증가되는 grain size로 인하여 grain boundary가 감소하였고 따라서 높은 oxygen flow rate에서 증착된 박막은 면저항이 감소하는 현상을 나타내었다. SiO2/Si 기판과 Si 기판에 증착된 LSMO 박막의 TCR 값은 약 -2.0 ~ -2.2%를 나타내었다. La0.7Sr0.3MnO3 films were deposited on SiO2/Si and Si substrates annealed at 350oC by rf magnetron sputtering. The oxygen gas flow rates were varied as 0, 40, and 80 sccm. Without post annealing process, La0.7Sr0.3MnO3 thin films on SiO2/Si and Si substrates were polycrystalline with (100), (110), and (200) growth planes. The grain size of La0.7Sr0.3MnO3 thin films was increased with increasing oxygen gas flow rate. The sheet resistance of La0.7Sr0.3MnO3 thin films was decreased with oxygen flow rate due to the increased grain size which induced a reduction of grain boundary. TCR (temperature coefficient of resistance) values of La0.7Sr0.3MnO3 thin films were obtained from -2.0% to -2.2%.
RF 스퍼터링을 이용하여 저온에서 SiO2/Si 기판 위에 증착된 La0.7Sr0.3MnO3 박막의 구조 및 전기적 특성
최선규,A. Sivasankar Reddy,하태정,유병곤,박형호 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.11
The La0.7Sr0.3MnO3 was deposited on SiO2/Si substrate by RF magnetron sputtering. The oxygen gas flow rate was changed from 0 to 80 sccm and the substrate temperature was 350oC. The oxygen gas flow rate was changed to control the growth orientation and crystalline state of the film. Relatively high TCR (temperature coefficient of resistance) value (−2.33%/K) was obtained when comparing with the reported values of the films prepared by using high substrate anneal temperature. The decrease in the sheet resistance and TCR value were observed when grain size of the film increased with the increase of oxygen gas flow rate.
Room temperature photoluminescence property of Mo-doped In2O3 thin films
S. Kaleemulla,A. Sivasankar Reddy,S. Uthanna,P. Sreedhara Reddy 한국물리학회 2010 Current Applied Physics Vol.10 No.2
Mo-doped In2O3 thin films have been prepared on glass substrates using an activated reactive evaporation method and systematically studied the effect of oxygen partial pressure on the structural, optical,electrical and photoluminescence properties of the films. The obtained films are highly transparent and conductive. The films exhibited the lowest electrical resistivity of 5.2 × 10-4 Ω cm, with an average optical transmittance of 90% in the visible region. An intensive photoluminescence emission peaks were observed at 415 and 440 nm.
최선규(Sun Gyu Choi),A. Sivasankar Reddy,유병곤(Byoung-Gon Yu),류호준(Hojun Ryu),박형호(Hyung-Ho Park) 한국진공학회(ASCT) 2008 Applied Science and Convergence Technology Vol.17 No.2
La0.7Sr0.3MnO₃ 박막을 rf 마그네트론 스퍼터를 이용하여 챔버 내 산소가스유량비를 0, 40, 80 sccm 으로 조절하고 후열처리 공정 없이 기판온도를 350℃로 유지하면서 SiO₂/Si(100) 및 Si(100) 기판에 증착하였다. 증착된 La0.7Sr0.3MnO₃ 박막은 SiO₂/Si(100), Si(100) 기판 모두 (100), (110), (200)면을 갖는 polycrystalline 상태였으며, oxygen flow rate이 증가함에 따라 박막의 grain size가 증가하였다. 증가되는 grain size로 인하여 grain boundary가 감소하였고 따라서 높은 oxygen flow rate에서 증착된 박막은 면저항이 감소하는 현상을 나타내었다. SiO₂/Si 기판과 Si 기판에 증착된 LSMO 박막의 TCR 값은 약 -2.0 ~ -2.2%를 나타내었다. La0.7Sr0.3MnO₃ films were deposited on SiO₂/Si and Si substrates annealed at 350℃ by rf magnetron sputtering. The oxygen gas flow rates were varied as 0, 40, and 80 sccm. Without post annealing process, La0.7Sr0.3MnO₃ thin films on SiO₂/Si and Si substrates were polycrystalline with (100), (110), and (200) growth planes. The grain size of La0.7Sr0.3MnO₃ thin films was increased with increasing oxygen gas flow rate. The sheet resistance of La0.7Sr0.3MnO₃ thin films was decreased with oxygen flow rate due to the increased grain size which induced a reduction of grain boundary. TCR (temperature coefficient of resistance) values of La0.7Sr0.3MnO₃ thin films were obtained from -2.0% to -2.2%.