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2 2011

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Electrical and optical properties of NiO films deposited by magnetron sputtering

Guziewicz M., Grochowski J., Borysiewicz M., Kaminska E., Domagala J. Z., Rzodkiewicz W., Witkowski B. S., Golaszewska K., Kruszka R., Ekielski M., Piotrowska A.

Optica Applicata

2011

Vol. 41, nr 2

431--440

Films of transparent semiconductors are widely studied and developed because of high potential applications in electronics in last decade. Our work concerns the properties of NiO films fabricated by RF magnetron sputtering. Electrical and optical parameters of the films were characterized using Hall and transmittance measurements, respectively. P-type conductivity of as-deposited films and after annealing in oxygen or argon at the temperature range from 300 °C to 900 °C was verified. Transmittance of NiO films strongly depends on deposition temperature and oxygen amount during sputtering. Films deposited at room temperature without oxygen have transmittance near 50% in the visible range and resistivity about 65 ?cm. An increase in oxygen amount in deposition gas mixture results in higher conductivity, but transmittance decreases below 6%. Resistivity of 0.125 ?cm was attained at sputtering in oxygen. Films deposited at temperature elevated up to 500 °C are characterized by transmittance above 60% and lower conductivity. Annealing of NiO films in Ar causes resistivity to rise dramatically.

Mechanisms of carriers transport in Ni/n-SiC, Ti/n-SiC ohmic contacts

Kisiel R., Guziewicz M., Golaszewska K., Sochacki M., Paszkowicz W.

Materials Science Poland

2011

Vol. 29, No. 3

233--240

A mechanism of carriers transport through metal-semiconductor interface created by nickel or titanium-based ohmic contacts on Si-face n-type 4H-SiC is presented herein. The mechanism was observed within the temperature range of 20 °C - 300 °C which are typical for devices operating at high current density and at poor cooling conditions. It was found that carriers transport depends strongly on concentration of dopants in the epitaxial layer. The carriers transport has thermionic emission nature for low dopant concentration of 51016 cm-3. The thermionic emission was identified for moderate dopant concentration of 5-1017 cm-3 at temperatures higher than 200 °C. Below 200 °C, the field emission dominates (for the same doping level of 5-1017 cm-3). High dopant concentration of 5-1018 cm-3 leads to almost pure field emission transport within the whole investigated temperature range.