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The growth morphology after conventional vapor phase deposition in homoepitaxy on Pt(111) and possibilities ofits modification - by temperature variation, by simultaneous ion bombardment and by the use of adsorbates - have been investigated by means of temperature variable scanning tunneling microscopy (STM). In order to quantitatively study the growth a new criterion has been introduced - the growth number. It characterizes the actual state of a considered system after growth which has taken place between the limits of the two extremes, Le. the ideal layer-by-layer growth and the ideal threedimensional growth. The growth number is applied and compared to the output of the normalized interface width criterion for the temperature and coverage dependence of the growth morphology. For conventional vapor phase deposition of Pt on Pt(111) the growth is known to proceed nearly layerwise at low and at high temperatures and threedimensional in the medium temperature range. Application of the growth number uncovers that the system is in intermediate states for most of the deposition temperatures. A binaryclassification of growth morphologies in layer-by-layer or threedimensional is therefore insufficient to describe the state a growth system is in. The growth number reveals that only around 430K the system is very close to an ideally threedimensional growth. An almost ideal layer-by-layer growth is only found around 640K. It is shown that this growth is caused by the Pt(111)-reconstruction which significantly decreases the island size without changing the diffusion of adatoms on top of the islands. Thereby an improved interlayer mass transport is induced. An often used way to modify a growth morphology is to continuously bombard the surface with ions during vapor phase deposition (ion beam assisted deposition - IBAD). The investigation of the infiuence of this method on the growth of Pt on Pt(111) shows that above 200K the simultaneous ion bombardment leads to a drastical increase of the island number density compared to conventional deposition: adatom clusters are created with high efficiency as a result of the ion impacts and adatoms from the vapor phase attach to these clusters. In contrast, at temperatures where thermal adatom diffusion is no longer possible the island number density in the presence of ion bombardment is reduced due to bombardment-induced adatom mobility. Thin films produced with IBAD at 400K are smoother than those obtained by conventional vapor phase deposition. The bombardment causes an increased interlayer mass transport due to the different nucleation behavior and to effects related to the decreased structure size. At 50K where vapor deposited films are highly disturbed in regard to epitaxy, the ion [...] |
