  The impact of variable Ti self-doping on the 1T-TiSe2 charge density wave
(CDW) is studied by scanning tunneling microscopy. Supported by density
functional theory we show that agglomeration of intercalated-Ti atoms acts as
preferential nucleation centers for the CDW that breaks up in phaseshifted CDW
domains whose size directly depends on the intercalated-Ti concentration and
which are separated by atomically-sharp phase boundaries. The close
relationship between the diminution of the CDW domain size and the
disappearance of the anomalous peak in the temperature dependent resistivity
allows to draw a coherent picture of the 1T-TiSe2 CDW phase transition and its
relation to excitons.
