| The work presented in this dissertation is focused on the studies of a variety ofproperties for the initial stages of the Er/Si(001) and Hf/Si(00l) interface fOrmationby various experimental techniques and theoretical methods. ln addition, the resonantphotoemission phenomenon from Si(00l) has also been fOund.l. The ultra-thin Er layers with the thicAnesses in the range of 0.5 ~ 3monolayer (ML) are fOrmed by electron beam evaporation on Si (00l) substrate atroom temperature in an ultra-high vacuum system. After annealing at lowertemPeratures, ordered simcfores form on the surface. The trallsition of the surfacereconsmiction pattem from (2 X l) to (4 X 2) with the increase of Er coverage up to lML is observed by the reflective high energy electron diffraction (RHEED) and lowenergy electron diffraction (LEED). Based on the further study by the scedngtunneling microscopy (STM) investigation, a sthce strUctural model Wth theformation of the pair-like Er adatom rows is adoPted to rePlace the previouslysuggested single Er adatom model to explain the (4X2) reconsmiction. ln this newmodel, each Er atom replaces a Si dimer on the top layeT, and every tWo adjacent Eratoms form a pairlike smicture, with a surface vacancy being illtrOduced among twOadjacent Er dimers. A theoretical calculation based on this model is carried out, andthe results verify that the vacancies may reduce the mean binding energy of the Eratoms, and thus the model is energetically favorable. The bias-dependence of theSTM images is exp1ained in terms of the coupling between the Si pairs and thebuckling Er pairs.2. From the Si and Er core Ievel spectra and the Si valence band spectrum arather detailed description of the Er/Si(00l) interface formation is presented. ThefOllowing results can be extracted. The pinning of the surface Fermi level at 0.29 eVabove its initial value, equivalent to a variation of Schottky baxrier height of 0.67 eVis observed upon deposition of ~ 0.6 ML Er onto the clean p-tyPe Si(00l)(2xl)surface at room temperature. While no evidence is found for the formation of ErlIIsilicides at as-deposited surfaces. Annealing of the Er-covered Si(00l ) surfaces to 600OC results in the emergence of a new component with a 1.2 eV energy shift tOwardslower binding energy in the Si 2p core level spectrum, which is indicative of thepresence of some sort of Er silicides. Meanwhile, the Er 4f spectrum measured uponannealing exhibits well-resolved fine structure, implying that only mono-species of Ersilicide may exist on the surface.On the other hand, ultra thin Er silicide films are fOrmed on Si (00l) substrateby room temperature deposition of 3 to 20 ML Er atoms followed with the subsequeniin situ annealing. Auger e1ectron spectroscopic measurements indicate that theintermixing between the deposited Er and the substrate Si atoms Ieads to thefOrmation of ErSi, with the outermost surface terminated by Si atoms. X-raydiffiaCtion confirms that the resulting ErSi, film possesses the tetrahedral ThSi,crystalline strUcture. c(2x2) and (2x2) reconstructions obtained under differentannealing temPerthees a-nd different Er coverages are observed by RHEEDobservations. By carefully checking the LEED pattern, it is found that the "(2x2)"pattem is actually a combination of the c(2 x 2) reconstruction from the ErSi, islandsurfaces and the (2x l) reconstruction from the bare Si subStrae. STM observationconfirms the above argument, and verifies that c(2x2) reconsmiction occurs on thetops of the ErSi, quadrate nanoislands. An atomic smictufal model for c(2x2)reconstruction is proposed and a total energy calculation illustrates that the hollow-site-occuPied Si adatom model might be a possible atomic struCtUre of the c(2x2)reconstruction.TWo different groWth methods are used to prepare ultra-thin Hflayers on Si (001)substrate for the purpose of studying the initial stage of the hafniuIn/Si(001) interfaceformation. T...
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