Effect of Oxidation Protection Layer on the Performance of Magnetic Force Microscope Tip

Abstract

  Magnetic force microscope (MFM) tips are prepared by coating silicon tips of 4 nm radius with 20-nm-thick metallic magnetic films with and without 2-nm-thick oxidation protection layers. Iron (Fe) is used as the magnetic material, whereas carbon (C), silicon nitride (Si-N), or silicon carbide (Si-C) is employed as the protection layer. The MFM tips are exposed in an environment of high temperature of 70 °C and high relative humidity of nearly 100%. The effect of protection layer on the spatial resolution is investigated as a function of period of exposure to the environment. The resolution of MFM tip without protection layer deteriorates from 7.2 to 21.2 nm in 10 days. The deterioration is attributed to an increase in the tip radius and a loss of the detection sensitivity caused by oxidation of coated Fe material. In contrast, the resolutions of tips with C, Si-N, and Si-C layers are kept almost constant at 12.1 ± 0.5, 12.1 ± 0.5, and 14.8 ± 2.1 nm for a time span of 10 days, respectively. The coating of a very thin protection layer has been shown effective in keeping the MFM tip performance for a long period of time by preventing the oxidation of coated metallic magnetic material.