The Surface And Low Dimension Dynamical Behaviors Of Amorphous Metals And Their Applications

As a simple and typical condensed matter with the disorder atomic structure,metallic glasses(MGs)or amorphous alloy have many unique properties which are different from their crystalline counterparts.However,it is quite difficult to improve the size of preparation for current technologies,on the other hand,MGs are lacking in macroscopic tensile ductility,which restricts the widely used of BMGs,and also limits the development of MGs research.In the micro/nano scale,MGs not only show the better mechanical properties,compared with the crystalline counterparts MGs,but also show some special performance.Therefore,there are great potential for the applications of nanoimprint,nano-functional device,3D printing and new energy materials.However,the studies of glassy surface and interface is still are infancy.Little is known on physical and chemical properties of nano-sized amorphous alloy.The surface dynamic behaviors of metallic glass would be an important research topic in future.As there is the great demand of the new micro and nano functional materials,the thin film deposition technologies are widely used to prepare the micro/nano-devices or grow the low dimensional materials.Take advantage of these technologies,this thesis will present the direct observation and measurement of surface and low dimension dynamic behaviors of MGs,and the investigation of related potential applications.Base on the current methods of surface dynamic measurement,we applied the method of surface sine gratings decay to measure the surface diffusion and viscosity of Pd-basd MG.It is found that the surface diffusion rate is millions of times higher than the bulk diffusion at the temperature below and near glass transition temperature.And such a fast surface dynamic induces the fast singlecrystal-like surface crystallization,which shows the growth rate along the surface is hundreds of times faster than from the surface to the interior.Furthermore,benefit from the high surface dynamic,the surface separate aluminum out and form the crystalline alumina passivation layer under the electron beam irradiation can be observed by the high resolution transmission electron microscopy(HRTEM)in aluminiferous MGs.While which has not been observed in the crystalline counterparts.Over the past decades the technologies and theories of the thin films preparation has been developed in to a mature stage,and the thin film deposition has become the important method to prepare the samples for modern condensed matter physics.However,the most of the past researches focused on the crystalline materials instead of amorphous or liquid materials.The amorphous materials not only have some unique physical and chemical properties,but also in the nano-scale they show the excellent properties much better than the bulk counterparts,while it is poor understanding of the nano-sized amorphous alloy.Take advantages of the methods of Pulsed Laser Deposition(PLD)and Ion Beam Assisted Deposition(IBAD)to prepare the atomic level ultrathin films,and observed by the aberration-corrected scanning transmission electron microscop(Cs-STEM)it was found that there are lots of special surface dynamic behaviors,such as the high thermal stability,high mobility or low room temperature viscosity and special crystallization behaviors,etc.Moreover,the thermal stability,surface morphology and composition structure can be controlled by the parameters as deposition rate,angle and ion energy,which can help us to prepare the amorphous materials with different properties and various micro/nano-structures.Furthermore,the liquid-like surface dynamics of amorphous alloy presents the high surface catalytic activity,and similar as its bulk counterparts the amorphous metallic thin films also have the outstanding mechanical and unique electrical properties which makes possible to be applied to the electronic skin research.As the early stage of investigation the surface and low dimensional science not only will develop more interdisciplinary research area,but also can provide new views in the traditional amorphous materials study in future.