UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2011 Meeting


Section: Optics, Spectroscopy, Plasma and Lasers


Title:
Electrical characterization and optimization of TVA plasma for multilayer nanostructures


Authors:
I. Jepu (1), C. Porosnicu (1), I. Mustata (1), C. P. Lungu (1), F.Miculescu (2), V. Kuncser (3)


Affiliation:
National Institute for Lasers, Plasma and Radiation Physics, Magurele-Bucharest, RO (1)

Politehnica University of Bucharest, Faculty of Material Science and Engineering, Bucharest, RO (2)

3National Institute of Materials Physics, Bucharest-Magurele, RO (3)


E-mail
ionut.jepu@inflpr.ro


Keywords:
Thermionic vacuum arc


Abstract:
Thermionic vacuum arc method was applied to prepare high quality structural thin films on glass and silicon substrates. The method proposed in this work is based on electron beam emitted by an externally heated cathode (a tungsten grounded filament) accelerated by a high anodic voltage. The electron beam evaporates the anode material as neutral pure particles and facilitates their deposition on the substrate when the electron energy and the discharge current intensity are not too high (5-50 eV and 10-100 mA, respectively). In order to obtain the desired structures, an optimization of plasma ignited in pure metal vapors was performed. Total control of the external parameters of the plasma made possible the obtaining of the multilayer nanostructure. In the present paper we report obtaining Cu-Ni-Cu-Fe-Ta type nanostructure of 3-5-10 and 50 nm thickness using the original method of thermionic vacuum arc. Due to the absence of the buffer gas inside the vacuum chamber, the multilayer structures had no impurities. For this experiment it was used an experimental setup consisting in one electron beam gun representing the cathode and a multi-crucible circular anode. The voltage applied to the anode system had values between 600V and 2100V depending on the deposited material. The current values of the tungsten filament representing the cathode were of 50 to 60A. Due to different position of each substrate in respect with the discharge point, different concentration was obtained. Electrical characterization was performed on each ignited plasma. It was measured the collector current from the ignited plasma, by applying a negative voltage on the collector. This measurement was established for different values of the filament current and different negative voltages applied on the collector. Structural and morphological properties were analyzed by SEM (Scanning Electron Microscopy) and XRD (X-ray Diffraction). Electrical and magnetic properties of the multilayer structures were analyzed using a four point measurement system. For the thinner structures were observed changes in the electrical resistance behavior. The results were correlated with the plasma optimization process.