Ni-Cr系酸化物薄膜の微細構造に及ぼす酸素添加の影響

概要

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Ni-Cr oxide thin films were prepared by the magnetron sputtering with an NiO-Cr2O3 composite target and O2-added Ar sputtering gas. The electric conductivity of the films showed sharp changes from 10-11 S·m-1 to 100 S·m-1 with the addition of O2 gas from 0 vol% to 20 vol%. The existence of the cubic nickel oxide crystal was assured only in the films prepared by the O2-addition of 20 vol% or less from X-ray diffraction measurements. X-ray photoelectron spectroscopic analysis revealed that the chemical states of chromium and nickel are Cr2O3 and Ni1-xO (0<x<0.34), respectively, and the nickel deficiency maybe increased with the addition of O2 gas. These results suggested that the Ni1-xO crystalline particles were embedded in the amorphous Cr2O3 matrix. The crystallite size of Ni1-xO particles increased from 6.3 nm to 32 nm with increase in the O2-addition ratio from 0 vol% to 20 vol%. The close relationship between the electrical conductivity and the Ni1-xO particle size of the films brought us to the conclusion that the increase in conductivity was possibly attributable to the crystal growth of the conductive Ni1-xO crystallites as well as its nickel deficiency.