Experimental Study On Mechanics Characteristics Of Nanocontact And Friction For Germanium

With the rapid development of nanotechnology, MEMS (Microelectromechanical system, MEMS) has become more and more broad application prospects in the automotive, aerospace, communications, medical, environmental protection and so on. However, due to the effect of surface and size, when reduce device scale to the micro/nano-scale, MEMS surface force increase nearly one thousand times in relative size force, and the effect of wear, viscous resistance and surface tension related to the surface friction, are more significant on the system than the effect of inertia force and electromagnetic force related to the volume, surface force becomes the key factor that affects system performance. While germanium metal single crystal belongs to diamond structure, has excellent physical and chemical properties, are widely used in the semiconductor material, medical and some new application areas.Especially in the field of microelectronics, with the miniaturization of the chip and transistor, Moore’s law is facing the limitation of silicon-based materials on the physical size, it need to develop a new kind of material to break through the limit, the features of germanium makes base substrate likely to replace silicon germanium and applied in the advanced nano electronic devices. Therefore, further study of contact and friction characteristics in crystal germanium micro/nano mechanics have the vital significance for improving working performance and service life of the crystal germanium.This topic is selected from the national natural science fund project:the experimental section of "Micro mechanical friction pair contact mechanics behavior of multi-scale coupling analysis method research". In this paper, based on the theory of contact mechanics at home and abroad at present stage, we have done the contact and sliding friction experiment to the crystal germanium by nanometer indentation and scratch technology. Through the MTALB process of experimental data obtained under different conditions of load-displacement,Hardness/elastic modulus curve, displacement-friction curve, etc., analyze the curve three-dimensional topography of AFM experimental research, the crystal germanium mechanical properties of different contact conditions are as follows:By the load-displacement curve, we can see the pop-in in the loading stage when shift the elastic deformation to plastic deformation.When pressure depth greater than30nm, the phenomenon of pop-out appears in unloading process, the causes of this phenomenon may be that slip or partial fracture appear in crystal germanium with the increase of pressure into the load; According to the indentation work method, the size surrounded by add-unloading curve on behalf of the plastic work, so the size of the area surrounded from curve can analyze the crystal germanium material plastic, crystal germanium (110) crystal plane plastic is best,(100) crystal plane is second,(111) crystal plane plastic is worst; Each crystal crystal germanium atom density has the larger gap, the crystal germanium hardness and elastic modulus shows obvious anisotropy, the size in the order:(111) crystal plane,(110) crystal plane,(100) crystal plane. When pressure depth is greater than500nm, crystal germanium appears brittle fracture, with the increase of pressure depth, hardness and elastic modulus tends to be stable gradually.In the constant load constant speed sliding contact process, the wear properties of the crystal germanium have little affection by the crystal orientation. Under the condition of constant load, sliding speed on friction properties of crystal germanium has great influence. The frictional force is increased with the increase of the speed of sliding friction, and under the different sliding velocity, the surface of crystal germanium occurs serious wear-groove damage. With the increase of sliding velocity, groove on both sides of the debris volume is becoming more and more big, the depth of the groove is also increased gradually; in the process of a single scratch with smaller load, due to the effect of adhesion force, crystal forms convex surface, and with the increase of load, the raised height gradually reduces, and appears the coexisting phenomenon of bump and groove. With the increase number of friction, bump disappears, nick completely renders groove. When friction continues to increase, crystal germanium material appears rupture.