[seminar] DANAS: NADER ZAKI (IF, 29.10., 15 sati)

[IF Seminar]

Poštovani,

podsjećamo Vas na današnji seminar na Institutu za fiziku,
koji će u 15 sati u predavaonici u zgradi Mladen Paić održati 
Nader Zaki sa Sveučilišta Columbia u New Yorku. 
Nader Zaki je trenutno gost na Institutu za fiziku u sklopu
bilateralne suradnje, Materials World Network (Prof. Osgood, 
Columbia - dr. Kralj, IF).


          AN STM STUDY OF ATOMIC COBALT WIRES
                      Nader Zaki
Applied Phyisics & Mathematics Department, Columbia University
                     nzaki1 at gmail.com

Due to stronger electron-electron interactions, 1-D systems are predicted 
and, in some cases, have been shown to exhibit unique and exotic electronic 
properties. One route to the formation of 1-D systems is by self-assembly 
using low-index vicinal crystal surfaces. In this regard, we have 
successfully formed 1-atom wide Co wires using Cu(775), a 7-atom wide stepped 
array with (111) terraces. For our particular morphology, the Co wires are not 
laterally encapsulated but are positioned exactly at the step edge. We have 
performed STM studies of this system at room temperature (RT) and have made 
STS measurements at low temperature (LT), ~5K. While vicinal Cu(111) does 
exhibit "frizz" at the steps when scanning above cryogenic temperatures, 
the Co wires pin the edges, visually accentuating their presence under STM. 
Furthermore, we observe a lower local density of states for the Co wires as 
compared with the Cu steps at RT, which also serves to differentiate the 
two metals.
At LT, a Co chain at the step edge induces a Friedel-like oscillation that is 
not present at a bare Cu step. Cu(111) possess a surface projected bandgap 
which may electronically decouple the wire electrons that reside in this gap. 
However, we also see resonances at the Fermi level which suggests electronic 
coupling between the vicinal Cu surface and the Co electrons.


(voditelji seminara IFa, Berislav Horvatić & Marko Kralj)