| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 100 === NiO and CoO may react and form a low-resisitivity spinel structure with P-type conducting behavior and become one of transparent conducting oxides. In this study, nickel and cobalt nitrates with adequate ratio were mixed and heated at 300˚C for 24 h. Single-phase NiCo2O4 spinel was obtained. However, when the spinel powder were heated at temperatures 500˚C, 1000˚C, and 1500˚C, (Ni, Co)O solid solution with rock-salt structure appeared with consumption of NiCo2O4 spinel. At temperatures greater than 1000˚C, most spinel phases converted into the rock-salt phases.
To obtain a sputtering target consisting of nickel-cobalt oxides, the powder compact was sintered at 1500˚C for 6 h in air. Subsequently, low-temperature annealing was conducted to convert (Ni, Co)O with rock-salt structure into NiCo2O4 spinel. Spinel phase gradually appeared after annealing at adequate temperatures. For example, after annealing at 600˚C for 120 h, as high as 58.6% of (Ni, Co)O transformed to NiCo2O4 spinel.
To obtain a thin film of nickel-cobalt spinel, RF magnetron sputtering deposition method was adopted using (Ni, Co)O target under Ar or O2 atmosphere. The as-deposited film showed amorphous structure. With annealing at 600˚C for 120 h, a thin film of nickel-cobalt oxides showing spinel structure was obtained. The electrical property of spinel film was measured using 4-probe technique. The reduction in resistivity from 4.21 x 10-1Ω.cm down to 5.41 x 10-2 Ω.cm was observed.
|
|---|
