K. Tamilarasan

Enhanced H2 sensing properties of a-plane ZnO prepared on c-cut sapphire substrate by sputtering

Zinc oxide (ZnO) thin films have been prepared on c-plane sapphire substrate by magnetron sputtering technique. The influence of deposition time on the structural, optical and photoluminescence properties of the films have been investigated. XRD patterns reveal the growth of preferentially oriented (101) non-polar a-plane ZnO film with hexagonal wurtzite structure. The PL peak shifts towards lower wavelength for deposition time up to 20xa0min, which is in consistent with the results obtained from UV absorption studies. The blue shift in the PL peak confirms the possibility for quantum confinement effect. The band gap energy of the film increases from 3.33 to 3.38xa0eV, indicating enhanced quantum confinement effects. FESEM micrographs showed that the films have a smooth and dense morphology with uniform grain growth. Hydrogen sensing measurements indicated that a-plane ZnO film on c-sapphire showed higher response than c-plane ZnO film reported earlier. The sensor response of 44xa0nm thick ZnO film exhibit highest response of 145 towards 500xa0ppm H2 gas at the operating temperature of 200xa0°C.

Room temperature ferromagnetic and ferroelectric properties of Bi1−xCaxMnO3 thin films

Bi1−xCaxMnO3 (BCMO) thin films with x = 0, 0.1, 0.2, 0.3 and 0.4 are successfully deposited on the n-type Si (100) substrate at two different temperatures of 400 °C and 800 °C using RF magnetron sputtering. The stoichiometry of the films and oxidation state of the elements have been described by X-ray photoelectron spectroscopy analysis. Dielectric measurement depicts the insulating property of BCMO films. Magnetic and ferroelectric studies confirm the significant enhancement in spin orientation as well as electric polarization at room temperature due to incorporation of Ca2+ ions into BiMnO3 films. The BCMO (x = 0.2) film grown at 400 °C shows better magnetization (Msat) and polarization (Ps)with the measured values of 869 emu / cc and 6.6 μC/ cm2 respectively than the values of the other prepared films. Thus the realization of room temperature ferromagnetic and ferroelectric ordering in Ca2+ ions substituted BMO films makes potentially interesting for spintronic device applications.

Influence of substrate and Ca substitution on multiferroic BiMnO3 thin films

BiMnO3 (BMO) and Ca (10 at%) substituted BiMnO3 (BCMO) thin films are grown on n-type Si (100) and Pt/Ti/SiO2/Si (100) substrates by RF magnetron sputtering. The structural, elemental, morphological, magnetic, dielectric and ferroelectric properties of the films are investigated by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDAX), atomic force microscope (AFM), vibrating sample magnetometer (VSM), dielectric and ferroelectric measurements, respectively. The XRD pattern shows that the films acquire monoclinic structure with C2 space group. The elemental composition and surface roughness of the films are also measured by EDAX and AFM analysis, respectively. The VSM results exhibit that all the films possess room temperature ferromagnetism and the BCMO film deposited on the Si substrate has better magnetic properties (Mrem = 1.8 × 10−3 emu cm−3) than the other films. The dielectric measurement also reveals that the BCMO film has the highest value of dielectric constant (497) with less dielectric loss (0.3). Similarly, the ferroelectric measurement implies that all the films possess room temperature ferroelectricity.

Erratum to: Enhanced H2 sensing properties of a-plane ZnO prepared on c-cut sapphire substrate by sputtering

The online version of the original article can be found under doi:10.1007/s10854-012-0927-y.K. Vijayalakshmi (&) K. KarthickDepartment of Physics, Bishop Heber College, Tiruchirappalli,Tamil Nadu, Indiae-mail: viji71naveen@yahoo.comK. S. Pugazhvadivu K. TamilarasanDepartment of Physics, Kongu Engineering College, Perundurai,Erode, Tamil Nadu, India

Influence of Sputtering Power on the Structure and Electrical Properties of Bi2Fe4O9 Thin Films

Bismuth ferrite (Bi2Fe4O9) thin films were grown on p-type Si (100) substrate by radio-frequency magnetron sputtering at 873xa0K. X-ray diffraction, field emission scanning electron microscopy and Raman spectroscopy studies revealed that the grown films have single-phase polycrystalline nature and are crystallized in orthorhombic structure. The grain size of the grown thin films was found to increase (56–130xa0nm) with sputtering power. Atomic force microscopy images clearly illustrated that the grown thin films have smooth surface. Energy-dispersive X-ray analysis revealed the presence of Bi, Fe and O elements with desired ratio and also the absence of impurities in the grown films. Analysis of ferroelectric hysteresis loops revealed that the remanent polarization and coercive field increase with the increase in sputtering power. Vicker’s hardness analysis showed that the hardness of films strongly depends on the grain size and film thickness, which are mainly determined by the sputtering power. The above observations revealed that Bi2Fe4O9 thin film deposited at higher sputtering power has good crystallinity and shows better electrical properties.

Effect of RF power on structural and magnetic properties of La doped Bi2Fe4O9 thin films

Effect of RF power on structural and magnetic properties of lanthanum (La3+) doped Bi2Fe4O9 thin films grown on p-Si substrates by radio frequency (RF) magnetron sputtering has studied in this investigation. It is observed that the sputtering power affects the crystalline nature and magnetic properties of grown thin films. X-ray diffraction and Raman spectrum confirms that the Bi2Fe4O9 (BFO) thin films were crystallized well with orthorhombic structure. The BFO thin films which was prepared at sputtering power of 100u2005W have good crystallinity than those prepared at 40u2005W. The magnetic properties are investigated by vibrating sample magnetometer. The magnetic hysteresis perceptive loop shows that the anti-ferromagnetic behavior of the sample at room temperature. These results confirms that the crystallinity and magnetic properties of the BFO thin films were enhanced at the higher sputtering power (100u2005W).

Structural and morphological studies on Bi1-xCaxMnO3 thin films grown by RF magnetron sputtering

Bi1-xCaxMnO3 (0 ≤ X ≤ 0.4) thin films are deposited on n–type Si (100) substrate at 800 °C by RF magnetron sputtering. X-ray diffraction pattern shows that the films are crystallized in monoclinic structure with C2 space group. The crystallite size and induced strain in the prepared films are measured by W-H plot. The cell parameters and texture coefficient of the films are calculated. The surface morphology of the films is examined by atomic force microscope. The study confirms the optimum level of calcium doping is 20 at. % in Bi site of BiMnO3 film, these findings pave the way for further research in the Ca modified BiMnO3 films towards device fabrication.

Influence of calcium on structural and morphological properties of BiMnO3 thin films

Bi1-xCaxMnO3 (x = 0, 0.1, 0.2, 0.4) thin films were deposited on n–type silicon (100) substrate by RF magnetron sputtering. The X-ray diffraction pattern showed that the films were in monoclinic structure with C2 space group. The crystallite size and strain in the prepared films were measured by W-H plot. The surface morphology of the films was examined by atomic force microscope. The thickness of films was measured by thickness monitor in the sputtering system. From the analysis, it has been concluded that the optimum level for calcium doping is 20 at.% in the Bi site of BiMnO3 thin film, which will lead a way for further research in the Ca doped BiMnO3 system.

Structural, Dielectric and Magnetic Properties of Bi2Fe4O9 Thin Film by RF Magnetron Sputtering

This paper presents the growth of bismuth ferrite (Bi2Fe4O9) thin film by radio frequency magnetron reactive sputtering on p-Si (100) substrate and the characterization of the grown thin film. The deposited thin film is characterized by X-ray diffraction (XRD), field emission scanning electron micrograph (FESEM), energy dispersive X-ray analysis (EDAX), dielectric measurements and vibrating sample magnetometer (VSM) analysis. The XRD study reveals the orthorhombic structure of the crystallites and the particle size is calculated as 45 nm. The FESEM result confirms that the film has smooth surface and uniform distribution of nanoclusters. The percentage of chemical compositions of the film is confirmed by EDAX measurement. The dielectric behavior of the film is examined in terms of the dielectric constant and the dielectric loss as a function of frequency. The magnetic behavior of the film is measured using VSM with the applied magnetic field of about 1 Tesla and the result shows the ferromagnetic behavior of the sample at room temperature.

Structural Properties of Zinc Doped Nanocrystalline Ceria

Zinc doped nanoceria powders were prepared by a simple and fast microwave induced combustion method using cerium nitrate, zinc nitrate, glycine and sorbitol. The resultant powders were examined for their structure and microstructure by XRD, SEM, TEM and their optical properties were measured by UV-Vis spectroscopy. The lattice parameter of the ceria powders was found in the range of 5.399 Å to 5.370 Å. The average crystallite size calculated from XRD was in the range ~ 4 nm to ~ 2.5 nm. The TEM selected area diffraction pattern images clearly showed the ring pattern indicated the powders were polycrystalline nature and there is agglomeration of the particles. Optical band gaps of the powders were in the range 2.71eV to 2.58eV.