Polycrystalline NiO Thin Films Applicable to Nano-Storage Media

Abstract
We have investigated local electrical properties of NiO thin films applicable to nano-storage devices. Polycrystalline NiO thin films were deposited on Pt/Ti/SiO$_2$/Si substrates by dc magnetron reactive sputtering methods. X-ray diffraction (XRD) data have shown that polycrystalline NiO films without second phases were grown on the substrates. We also observed root mean square roughness of 1.9 nm in the 15 $mu$m $imes$ 15 $mu$m area of a NiO film by using atomic force microscopy (AFM) mode. Using conducting atomic force microscopy (C-AFM) mode, we measured the change in local current distribution and found that the grown NiO films exhibited excellent resistance switching behavior at the nanoscale and good retention behavior of the written nano-sized domains. Moreover, we investigated the relation between pulse height and bit size. It was possible to write $8 imes8$ bits in $4 imes4 mu$ m$^2$ area and to store digital information corresponding to several Gbit/inch$^2$. Therefore, we successfully showed the feasibility of NiO films as media for nano-storage devices.
Keywords: NiO, Conducting atomic-force microscopy, Nano-storage media

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