Diluted magnetic semiconductors (DMS)

in which some atoms of host semiconductors are ran-domly substituted by magnetic atoms

are regarded as key materials for spintronics because they have charge and spin degrees of freedom in a single substance. ZnO is a potential candidate for applications of spintronics devices since its possibility for room temperature ferromagnetism and its intrinsic excellent electrical properties. ZnO is also suitable for fabricating carrier controllable ferromagnetism because carrier-controlling techniques for ZnO have been well established. And among the methods used for deposition of thin films

PLD is effective and has the advantage that the ratios of the elemental components of the bulk and film are almost the same

even for chemically complex systems. In this paper

Zn

0.95

Co

0.05

O thin films were prepared by pulse laser deposition(PLD) on silicon(100) and quartz substrates. By optimizing the growth conditions

the Co-doped ZnO thin films obtained at temperature of 700℃ and oxygen pressure of 0.02 Pa showed magnetism even at room temperature. The X-ray diffraction patterns suggested that the obtained films showed c axis orientation preference

and Co related phases such as CO

2

O

3

didn’t appear

simply indicating that Co ions had been successfully doped into ZnO crystal lattices. SEM images showed that the films have dense surfaces with small roughness. The obtained sample was measured to have a hole concentration of ~10

18

cm

-3

a mobility of 18.7 cm

2

·V-1·s

-1

and a resistivity of about 0.04 Ω·cm

maintaining semiconductivity.And the magnetization of the Co-doped ZnO film can be measured at 12 K

even at room temperature.