Effect of Ar plasmadistribution in RF-magnetron-sputtering on crystallinity and thermoelectricproperties of FeSi_2+x films

K.Kamata, H.Anzai, M,Sugita,Y.Oikawa, H.Ozaki

Department of Electrical Engineering andBioscience, Waseda University

3-4-1 Ohkubo, Shinjuku-ku, Tokyo,169-8555 Japan

The crystallinity and Seebeckcoefficient were investigated for FeSi_2+x(-0.3≤x≤0.3)films prepared by rf-magnetron-sputtering with various spatial distributions ofAr plasma. The crystallinity was evaluated by the intensity and peak width ofXRD spectra and by the grain size and compactness observed by SEM. Thedeviation x from stoichiometry was changed by changing the ratio of Fe and Siareas of the target. The Ar plasma distribution between substrate (MgO) andtarget was changed by various types of magnet setting behind and around thetarget.

The Seebeck coefficient S was measured in thetemperature region 470K–870K and showed negative values for all samplesin this study. The |S|showed a maximum at around 700K for each x, and showed a maximum at x=0 byvarying x for each temperature.

It was found that thecrystallinity was optimized when the plasma was concentrated to the targetside. Under this condition, |S| also showed a maximum value as high as 180mV/K at 700K, with deposition rate as highas 2.5nm/sec and with substrate temperature as low as 650K.