高Al组分Al_xGa_(1-x)N薄膜的弹性-塑性力学性质

Elastic-Plastic Mechanical Properties of Al_xGa_(1-x)N Thin Films with High Al Composition

采用纳米压痕方法,研究了AlN/spphire模板上的高Al组分AlxGa1-xN薄膜的力学性质,特别是弹性-塑性转变行为.研究表明,AlxGa1-xN薄膜的杨氏模量E随着Al组分的增加而增大,薄膜中产生塑性形变所必要的剪切应力也随着Al组分的增加而增大.在AlxGa1-xN薄膜纳米压痕实验中,观察到位移不连续的跳断('pop-in')行为,并且发现'pop-in'行为强烈依赖于Al组分,Al组分的增加导致这种行为的减少.我们认为随着Al组分的增加,AlxGa1-xN中键能的增强和由于AlxGa1-xN与AlN/sapphire模板之间晶格失配减少这两个因素增加了AlxGa1-xN中新位错形成的阻力,从而导致了AlxGa1-xN薄膜中的'pop-in'行为随Al组分增加而减少.

The elastic-plastic mechanical properties of AlxGa1-x N thin films with high Al composition are investigated by the nano-indentation technique. It is found that the Young＇s modulus E of the films and the shear stress to produce the plastic deformation in Alx Ga1-x N films increase with increasing Al composition, while the occurrence of the clear and sudden displacement discontinuity （＂pop-in＂） in the plastic deformation （PD） process decreases. With increasing Al composition,it is believed that the increase of the bond strength and the decrease of the stress due to the lesser lattice mismatch between AlxGa1-x N films and AlN/sapphire templates result in more resistance to the formation of dislocations,which is responsible for the ＂pop-in＂ behavior in AlxGa1-xN films.