Roughness development in electrodeposited ultrathin cobalt and nickel layers
- PDF / 266,463 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 28 Downloads / 227 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Roughness development in electrodeposited ultrathin cobalt and nickel layers Robert F. Renner and KNona C. Liddell Department of Chemical Engineering, Washington State University, Pullman, Washington 99164-2710 (Received 22 February 1999; accepted 3 November 1999)
For both Co and Ni, a series of electrodeposited films of varying thickness (2–10 nm) was grown under otherwise identical conditions using potentiostatic control. The substrates were pieces of Si wafer onto which a Cu basal layer had been thermally evaporated. Contact mode atomic force microscopy was used to measure both the root-mean-square peak height (nm) and the areal peak density (m−2) of each film. Root-mean-square (rms) peak heights for Co initially increase with film thickness and then plateau at a layer thickness of 3 nm. For Ni, the rms peak heights increase almost linearly for layer thicknesses less than 11 nm, reaching a value of 6 nm. Peak density shows the opposite trend, decreasing with layer thickness before reaching an approximately constant value for both metals at a film thickness of 4 nm. The atomic force microscopy data indicate that Ni and Co have different deposition mechanisms. A Co film initially nucleates rapidly; then the nucleation phase is followed by multinuclear, multilayer growth. Ni deposits also have initial rapid nucleation, but the dominant growth mode is primarily vertical, with increasing peak heights but no change in peak density. Increased peak density is linearly correlated with decreased peak height for the thinnest films in both systems.
I. INTRODUCTION
Since the discovery of giant magnetoresistance (GMR) in Fe/Cr multilayers,1,2 the microstructure and magnetic properties of layered alloys have been studied intensively. Physical deposition techniques have often been used to prepare multilayer materials for characterization, and there is considerable information on both molecular beam epitaxy (MBE) and sputtered samples. Interlayer roughness has been found to significantly affect the magnetoresistance (MR) ratio of multilayers made by either method.3–15 Independent of efforts to understand the novel properties of this new class of magnetic materials, development of modern multilayer electrodeposition processes began in the mid-1980s. Despite widespread use of Ni/ Cu and Co/Cu as model systems,16 –36 to date relatively few reports on electrodeposited multilayers include magnetic characterization data. Fewer still have considered layer roughness or topography.37 For electrodeposited multilayer films, the relationships among layer thickness, roughness, and magnetic properties remain to be investigated. This important knowledge gap persists even though electroplating has long been used in the manufacture of hard disk drives, where it continues to offer processing advantages that include rapid rates, good step coverage, comparatively easy scale up, and low capital and operating costs. 458
http://journals.cambridge.org
J. Mater. Res., Vol. 15, No. 2, Feb 2000 Downloaded
Data Loading...
