Cu／Ni多层膜中交变应力场对可动位错的制约

CONSTRAIN OF ALTERNATING STRESS FIELD ON GLIDE DISLOCATIONS IN Cu/Ni MULTILAYERS

Cu／Ni多层膜的强化作用来自于多层膜结构中交变应力场对位错运动的约束,该交变应力场主要包括两部分：在共格界面处由于剪切模量差而导致的镜像力,以及多层膜内由于晶格常数差而形成失配位错网的应力,如果位错在膜层内运动的临界应力值小于交变应力场的约束,位错会被限制在单层膜内运动,多层膜被强化；反之,则位错很容易通过界面到达临近的膜层,多层膜开始出现弱化,交变应力场的变化幅值与多层膜的调制波长相关,理论计算结果表明,Cu／Ni多层膜的临界调制波长为1．9 nm,但失配位错网的交变应力场在多层膜的调制波长λ=9 nm时振幅达到极值。

The strengthening of Cu/Ni multilayers arises from the constraint of the alternating stress field on glide dislocations in multilayers, which includes image forces due to modulus difference across an interface, and the stress of misfit dislocations due to lattice mismath at the interfaces. If the critical stress for interracial dislocation motion is smaller than the constraint of alternating stress field, the dislocations will bow and move within individual layer. In this case, the multilayers exhibit strengthening behavior; otherwise, multilayers will be weaken. The amplitude of alternating stress is dependent on the wavelength. Theoretical analysis shows that the wavelength for Cu/Ni multilayers is 1.9 nm, while the amplitude of the alternating stress of misfit dislocations peaks at λ=9 nm.