27 research outputs found
Surfactant effect in heteroepitaxial growth. The Pb - Co/Cu(111) case
A MonteCarlo simulations study has been performed in order to study the
effect of Pb as surfactant on the initial growth stage of Co/Cu(111). The main
characteristics of Co growing over Cu(111) face, i.e. the decorated double
layer steps, the multiple layer islands and the pools of vacancies, disappear
with the pre-evaporation of a Pb monolayer. Through MC simulations, a full
picture of these complex processes is obtained. Co quickly diffuses through the
Pb monolayer exchanging place with Cu atoms at the substrate. The exchange
process diffusion inhibits the formation of pure Co islands, reducing the
surface stress and then the formation of multilayer islands and the pools of
vacancies. On the other hand, the random exchange also suppress the nucleation
preferential sites generated by Co atoms at Cu steps, responsible of the step
decoration.Comment: 4 pages, latex, 2 figures embedded in the tex
Bringing online adaptive radiotherapy to a standard C-arm linac
Current online adaptive radiotherapy (oART) workflows require dedicated equipment. Our aim was to develop and implement an oART workflow for a C-arm linac which can be performed using standard clinically available tools. A workflow was successfully developed and implemented. Three patients receiving palliative radiotherapy for bladder cancer were treated, with 33 of 35 total fractions being delivered with the cone-beam computed tomography (CBCT)-guided oART workflow. Average oART fraction duration was 24 min from start of CBCT acquisition to end of beam on. This work shows how oART could be performed without dedicated equipment, broadening oART availability for application at existing treatment machines
Sb-enhanced nucleation in the homoepitaxial growth of Ag(111)
The effect of Sb on the homoepitaxial growth mode of a Ag(111) surface has been studied by scanning tunneling microscopy. In a previous paper we reported on the effect of Sb on the interlayer diffusion barrier of Ag(111). Here we describe in more detail the effect of Sb on the island nucleation and surface diffusion. We find a homogeneous effect of the Sb on the Ag(111) surface, while heterogeneous nucleation and sticking can be excluded. The surface diffusion barrier appears to be linearly dependent on the Sb concentration. This shows that Sb has an effect not only locally at the step edges, but also on the terraces where it decreases the mobility of the Ag atoms. Further, we show that the Sb segregates efficiently during growth. [S0163-1829(98)02807-0]