Date of Award
Doctor of Philosophy (PhD)
Physics & Astrophysics
Scanning Tunneling Microscopy and Spectroscopy (STM/STS), Transmission Electron
Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS) studies were performed to
characterize the morphology, electronic properties, and chemical properties of the Iridium
(Ir) induced nano-structures formed on clean Si (110) surface. It was found that the
deposition of Ir in the sub-monolayer and monolayer (ML) regime on clean Si (110) ``16 Ã 2ââ
surface produces Ir-silicide nano-structures, as this surface is suitable for growing
nanostructures because of its inherent structural asymmetry. STM shows that nanowires
with an average length and width of 100 nm and 21 nm, respectively, were grown on clean
Si (110) surface when 0.25 ML of Ir was deposited. Statistical analysis of STM images of Irsilicide
nanowires show that the length and the width of the nanowires are correlated. TEM
results show that there are two different regions across the nanowires, one close to the Si
substrate which is made of IrSi2 and other close to the nanowire surface which is possibly
made of amorphous Ir. STS indicates that the nanowires have different electronic properties.
The smaller nanowires are metallic based on size, but the bigger nanowires are
semiconducting with a band gap of ï¾ 0.34 eV.
STM images indicate that 2 ML of Ir deposition produces Ir covered flat terraces on
clean Si (110). The interface between the Ir and substrate is Ir-silicide.
In addition, quasi periodic Ir quantum dots (QDs) appear on Ir terraces. Quantum dots
are loosely bound to the terraces as they tend to move around if the STM tip comes close to
them. STS indicates that Ir-QDs exhibit Coulomb blockade and a negative differential
resistance at room temperature. Coulomb blockade and a negative differential resistance in
the dI/dV plot indicates a Coulomb gap of ï¾ 0.7 eV.
XPS data shows that the binding energy of both Ir modified Si 2p3/2 and Si modified
Ir 4f7/2 peaks shift towards higher energy with respect to pure Si and Ir which indicates that
the interface between Ir terrace and the Si substrate has a Si rich silicide layer.
Mohottige, Rasika, "Study Of Physical And Chemical Properties Of Iridium Modified Nanostructures Formed On Silicon (110) Surface" (2018). Theses and Dissertations. 2288.