Журнал нано- та електронної фізики (Journal of nano- and electronic physics)
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Item Low Temperature Electrical Resistivity Studies in Lead Thin Films(Сумський державний університет, 2013) Manjunath, A.W.; Sankarappa, T.; Ramanna, R.; Ashwajeet, J.S.; Sujatha, T.; Sarvanan, P.Thin lead films of thickness, 100 nm, 150 nm, 200 nm and 250 nm have been deposited using electron beam evaporation technique at room temperature onto glass substrates under high vacuum conditions. Films were investigated for electrical resistivity at low temperatures from 77 K to 300 K. Resistivity variation with temperature indicates transition from metallic to semiconductor behavior. Transition tem-perature increased with increasing film thickness. Temperature coefficient of resistance in the metallic re-gion has been determined for all the four films. Using Arrhenius relation, activation energy for conduction in metallic region has been determined. Mott’s small polaron hopping model has been employed to deter-mine activation energy in the semiconducting region. In a film of 250 nm thick, deviation from Mott’s small polaron hopping model for below 100 K was noted and that has been considered under Mott’s variable range hopping model. The complete understanding of electrical properties of Pb films has been necessitat-ed by the fact that the band gap in CdS decreases when Pb is incorporated into it, which in turn can be used to fabricated large efficient solar cells. It is for the first time that lead films of the present thickness have been investigated for low temperature resistivity. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/31978Item Magnetic and Low Temperature Conductivity Studies in Oxidized Nano Ni Films(Видавництво СумДУ, 2011) Sadashivaiah, P.J.; Sankarappa, T.; Sujatha, T.; Saravanan, P.; Santoshkumar; Prashantkumar, M.; Devidas, G.B.; Vijayakumar, B.; Nagaraja, N.; Sharanabasava, N.A set of single layered nanostructured Ni films of thickness, t = 25 nm, 50 nm, 75 nm and 100 nm have been deposited using electron beam gun evaporation technique at 473 K under high vacuum condition. From the grazing incidence X-ray diffraction (GIXRD) studies, NiO phase formation has been noted. Grain sizes of the films were determined. The microstructure was examined by scanning electron microscope (SEM) studies. Average surface roughness was determined by atomic force microscope (AFM). The room temperature magnetization has been measured using the vibrating sample magnetometer (VSM). The coercive field was observed to be increasing with increasing t and became maximum for t = 75 nm and decreases for further increase in t. The behavior of coercive field with t indicated softness of the films. Low temperature electrical conductivity in the range from 5 K to 300 K has been measured. Temperature dependence of electrical conductivity showed semiconducting behavior. At temperatures above θD/2 (θD is the Debye temperature), the conductivity behavior has been understood in the light of Mott’s small polaron hopping model and activation energies were determined. An attempt has been made to understand conductivity variation below θD/2 using variable range hopping models due to Mott and Greaves. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/23716