S. Venkatramana Reddy

Optimization of the distance between source and substrate for device-grade SnS films grown by the thermal evaporation technique

Tin monosulfide (SnS) films with varying distance between the source and substrate (DSS) were prepared by the thermal evaporation technique at a temperature of 300 degrees C to investigate the effect of the DSS on the physical properties. The physical properties of the as-deposited films are strongly influenced by the variation of DSS. The thickness, Sn to S at.% ratio, grain size, and root mean square (rms) roughness of the films decreased with the increase of DSS. The films grown at DSS = 10 and 15 cm exhibited nearly single-crystalline nature with low electrical resistivity. From Hall-effect measurements, it is observed that the films grown at DSS <= 15 cm have p-type conduction and the films grown at higher distances have n-type conduction due to the variation of the Sn/S ratio. The films grown at DSS = 15 cm showed higher optical band gap of 1.36 eV as compared with the films grown at other distances. The effect of the DSS on the physical properties of SnS films is discussed and reported.

Development of Hall sensor propeller anemometer for measuring wind speed using embedded controller

An Anemometer is a device for measuring wind speed. Propeller type anemometer measures wind speed by generating an a.c signal. In the development of new anemometer, we use Hall Effect sensor to generate digital signal. The voltage levels of the digital signal depends on the input voltage applied to the Hall sensor, its input voltage may be from 2.5V - 27V. The Timer/Counter is a register in the Microcontroller, whose value keeps increasing or decreasing for rising edge or falling edge of the internal or external clock source by a constant rate without the help of CPU. The external clock to the counter is the digital signal from the Hall sensor. Thus the rate of rotations made by the propeller is counted using counter in the PIC 18F series Microcontroller. The spinning rate of the propeller is proportional to the wind speed. Therefore, we can determine the wind speed from the measurement of spinning rate of the propeller using embedded controller and the radius of propeller. The performance of our system is compared with existing system and our designed anemometer is also inexpensive.

Doping effect of Ag+, Mn2+ ions on Structural and Optical Properties of ZnO nanoparticles

Pure ZnO and co-doped (Mn, Ag) ZnO nanoparticles have been successfully prepared by chemical co-precipitation method without using a capping agent. X-ray diffraction (XRD) studies confirms the presence of wurtzite (hexagonal) crystal structure similar to undoped ZnO, suggesting that doped Mn, Ag ions are substituted to the regular Zn sites. The morphology of the samples were studied by scanning electron microscopy (SEM). The chemical composition of pure and co-doped ZnO nanoparticles were characterized by energy dispersive X-ray analysis spectroscopy (EDAX). Optical absorption properties were determined by UV-vis Diffuse Reflectance Spectrophotometer. The incorporation of Ag+, Mn2+ in the place of Zn2+ provoked to decrease the size of nanocrystals as compared to pure ZnO. Optical absorption measurements indicates blue shift in the absorption band edge upon Ag, Mn ions doped ZnO nanoparticles.

Synthesis and structural properties of pure and co-doped (Cu, Ag) ZnO nanoparticles

Pure ZnO and co-doped (Cu, Ag) ZnO nanoparticles (Zn0.90Cu0.05Ag0.05O) are synthesized by chemical co-precipitation method in the presence of capping agent polyethylene glycol 600 (PEG 600) and annealed at 500 °C for 1h. The XRD measurements indicate that the samples show hexagonal structure without any change and the nanocrystalline size decreased from 12 to 5 nm. SEM images are of hexagonal structure of the ZnO and co-doped ZnO samples, and EDAX spectra reveals that the successful doping concentration of Cu and Ag.

Preparation and structural properties of pure and codoped (Mg, Ag) ZnO nanoparticles

Pure and co-doped (Mg, Ag) ZnO nanoparticles (Zn0.90Mg0.05Ag0.05O) are synthesized by chemical co-precipitation method in the presence of capping agent Polyethylene glycol 600 (PEG 600) and annealed at 500°C in air ambient for 1h. The XRD measurements reveals that the pure and co-doped ZnO samples have hexagonal structure without any change and the size of ZnO nanoparicles were decreased from 17 nm to 13 nm. FESEM images indicates that they are flake like structures of the ZnO and co-doped ZnO samples and ED AX spectra reveals that the successful doping concentration of Mg and Ag. From the TEM results, the size of the ZnO nanoparticles which are in good agreement with the XRD results.

Structural and optical properties of Ag and Co doped ZnO nanoparticles

Undoped and Ag, Co doped ZnO nanoparticles were Synthesized by Chemical Co-Precipitation method without use of capping agent. The X-ray diffraction results indicated that the synthesized codoped ZnO powders had the pure Hexagonal structure with out any significant change in the structure affected by Ag and Co. Substitution dopants Ag and Co elements are present in the ZnO host material and it conformed with the EDS spectra. Light blue emission was observed by PL spectra.

Preparation and Characterization of Ag and Co Doped ZnO Nano Particles

Pure ZnO and Ag, Co doped ZnO nano particles [Zn1-xAgxCoyO, where x = 0.00 and 0.05, y = 0.05] were synthesized by chemical co precipitation method without use of surfactant. All the prepared samples calcinated in 1 hour at 500oC, after that the morphology of the samples were evaluated by Scanning Electron Microscope (SEM). The X- ray diffraction (XRD) results indicated that the synthesized co-doped ZnO nano crystals had the pure hexagonal structure without any significant change in the structure affected by Ag and Co substitution. Dopant elements Ag and Co are present in the ZnO host material and conformed by Energy Dispersive Analysis of X-ray Spectra (EDAX). The incorporation of Ag+ in the place of Zn2+ has made a considerable decrease in the size of nano crystals as compared to pure ZnO nano particles (It is to be noted that Co should be kept constant at 5 mol %). Blue emission was observed by Photo Luminescence (PL) Spectra.