The Morphology Of 5-fold Surface On The AlPdMn Quasicrystal

Quasicrystals are a new form of the solid state which differs from the two known forms, crystalline and armorphous. The existence of long-range order without periodicity is the most striking feature of quasicrystal. They are intermetallic compounds normally found in a narrow chemical composition range of the phase diagram.In this paper, we employ several techniques (STM, SEI,AES, LEED)to gain insight into the atomic morphology at the surface of one particular quasicrystal, icosahedral Al-Pd-Mn. Upon Ar~+ sputtering ,light element will be preferentially removed on the surface. This result can be seen from the AES spectrum . preferentially sputtering lead to the surface transforming into crystalline phase. We used SEI to probe the surface and found this phase belong to body-center cubic phase, body-center cubic phase is stable below 700K annealing temperature. Above 700K ,we found the transition from body-center cubic phase into icosahedral phase. From AES we can also see that the composition of surface is close to the bulk. In this paper we explain the probability of existence on the body-center cubic and icosahedral phase and the transforming process.Scanning tunneling microscopy is one of the most frequently used experimental probes for the analysis of the local structure of quasicrystalline surface. In paper, we used Scanning tunneling microscopy probe the 5-fold surface from micrometer to nanometer scale. The surface prepared by sputtering annealing at 900K usually yields a step-terrace structure. The terraces are separated by steps with two different stepheights. We explain the surface according to diffusitivity. In nanometer scale, we found that different terrace have different morphology. Some terrace are mirrorlike but others have lots of voids which can expand at higher temperature (950K). In this process, it can form another stepheight with the void depth. We explain the evolution of stepheight in the paper.