基板加熱成膜によるc面配向Coスパッタ薄膜の完全六方晶化

摘要

Effects of substrate heating of Co sputtered film with c-plane sheet texture on atomic-layer stacking were investigated and correlation between the atomic-layer stacking and uniaxial magnetocrystailine anisotropy constant (K_u) were analyzed. Through the quantitative evaluation of degree of stacking faults using laboratory-scale in-plane XRD, it was found that;①c-plane-oriented pseudo-hcp structure with around 10% fcc stacking (P_(fcc)) as stacking faults was formed in Co films sputtered at room temperature (R.T.). By sputtering with 400 ℃ substrate heating, nearly complete hcp structure with less than 0.1% fcc stacking was successfully made.②The value of saturation magnetization (M_s) was constant and the same as the value or hep Co bulk with increasing substrate temperature (T_(sub)), while the value of K_u changed drastically against T_(sub) and took the maximum value of 6.1×10~6 erg/cm~3.③In the analysis of perpendicular magnetic torque with twofold and fourfold components, contributes dominantly to K_u (= K_(u1)十K_(u2)) at P_(fcc) = 7 -10 %. Moreover, K_(u1) and K_(u2) has the same contribution to K_u at P_(fcc) = 2.5 % and K_(u1) contributes to K_u more than K_(u2) at P_(fcc) = 0 %.④Therefore, it was revealed that substrate heating was effective method to eliminate stacking faults in c-plane-oriented Co magnetic grains, which accordingly enhances the uniaxial magnetocrystailine anisotropy energy of Co sputtered film to the same value of hcp Co bulk (K_u = 5.97×10~6 erg/cm~3).%基板加熱がc面配向Coスパッタ薄膜の原子積層構造に及ぼす効果について評価し，原子積層構造と一軸結晶磁気異方性定数（K_u）との相関について解析した.具体的には，In-plane X線回折法を用いて薄膜中に形成される積層欠陥の導入度合いを定量評価し，磁気特性と積層構造との相関を詳細に検討したところ，以下のことが明らかとなった.①c面配向Coスパッタ薄膜においては，室温成膜では積層欠陥として局所的なfcc積層を10％程度含んだ六方晶原子積層構造が形成される.400℃の基板加熱成膜では積層欠陥の導入度合い(P_(fcc))が0.1％以下となり，ほぼ完全にhcp積層した薄膜が形成される.②基板温度を変化させても飽和磁化(M_s)は変化しない一方で，K_uは大きく変化し400℃において6.1×10~6 erg/cm~3の極大を示す.③垂直磁気トルク曲線を2回および4回対称成分に分離してK_(u1), K_(u2)を解析したところ（K_u=K_(u1)+K_(u2))，P_(fcc)=7-10％ではK_(u2)が支配的だがP_(fcc)=2.5％付近でK_(u1)とK_(u2)の値がほぼ等しくなり，なP_(fcc)=0％近傍ではK_(u1)の方がK_(u2)よりも増大した.④したがってc面配向Coスパッタ薄膜の基板加熱成膜は，磁性結晶粒中の積層欠陥を排除し完全六方晶原子積層構造を形成させるための有効な手法であり，これによりCoスパッタ薄膜にもバルクの文献値(K_u=5.97×10~6erg/cm~3)に匹敵する一軸結晶磁気異方性エネルギーを発現させ得ることを見出した.