CoおよびFe-B磁性膜被覆による高分解能磁気力顕微鏡探針の作製

摘要

Magnetic force microscope (MFM) tips are prepared by coating Si tips of 5 and 3 nm radiuses with Co and Fe-B alloy films. The effects of coating film thickness, Si tip radius, and surface undulation of coated material on the MFM resolution are investigated. The MFM resolution is influenced by both the tip radius and the MFM signal detection sensitivity. As the coating thickness increases, the sensitivity increases due to the increase in remanent magnetization of coated film material. However, with increasing the coating film thickness, the tip radius increases. A thicker coating film thickness degrades the MFM resolution due to an increase of tip radius, though the sensitivity is enhanced. A resolution of 9.0 nm is obtained with an MFM tip prepared by coating Si tip of 5 nm radius with 18-nm-thick Co film. The resolution improves to 7.8 nm by using a sharper Si tip of 3 nm radius coated with 20 nm thick Co film. The MFM resolution further improves by using an Fe_(82)B_(18) alloy material which effectively decreases the MFM tip radius through realizing a smooth surface with reduced undulations around the top of MFM tip. A resolution of 7.3 nm is obtained with an MFM tip prepared by coating a Si tip of 3 nm radius with 20-nm-thick Fe_(82)B_(18) film. The present research has shown that in order to prepare an MFM tip with high-resolution capability. It is very important to use a sharp base tip with smaller radius, coated of a higher remanent magnetization film with a smoother surface.%先端半径5および3nmのSi探針をCoおよびFe-B合金膜で被覆することにより，磁気力顕微鏡（MFM）探針を作製し，被覆膜厚，被覆前のSi探針半径，および被覆膜の表面起伏がMFM分解能に及ぼす影響について調べた．分解能は探針形状および信号検出感度により影響された．被覆磁性膜厚の増加に伴い，被覆膜の残留磁化値が増大し，MFM信号検出感度が向上した．しかし，MFM探針の先端曲率半径が増大し，MFM分解能の低下を招いた．先端曲率半径5nmのSi探針を用いた場合，Co膜を18nm被覆したMFM探針で9．0nmの分解能が得られた．先端曲率半径が3nmのSi探針を用いた場合，分解能が7．8nmに向上した．また，Coの代わりにFe_(82)B_(18)合金の被覆膜（20nm）を用いることにより，MFM分解能が7．3nmまで改善された．Fe_(82)B_(18)膜は非晶質でSiに対する濡れ性が良いためMFM探針の表面起伏が改善され，滑らかで鋭い先端曲率を持つMFM探針を作製できた．本研究により高分解能なMFM探針の作製では，高い残留磁化値を持ち，かつ先鋭で滑らかな表面を持つ探針の実現が重要であることが示された．