We employ x-ray photoelectron spectroscopy (XPS), reflection high-energy electron diffraction
(RHEED) and nuclear reaction analysis (NRA) to characterize the concentration-dependent
structural properties of nitrogen doping into rutile TiO2. High quality N-doped TiO2 were
prepared on rutile single crystal TiO2(110) substrates using plasma-assisted molecular beam
epitaxy with an electron cyclotron resonance (ECR) plasma and Ti effusive sources. Films with
N dopant concentrations at or below 2 at.% exhibited predominately substitutional doping based
on NRA data, whereas films with concentrations above this limit resulted in little or no
substitutional N and surfaces rich in Ti3+ . The binding energy of the N 1s feature in XPS did not
readily distinguish between these two extremes in N-doping, rendering features within 0.4 eV of
each other and similar peak profiles. Although widely used to characterize the state of N in
anion-doped TiO2 materials, we find that XPS is unsuitable for this task.
Synchrotron-based Far-IR Reflection Absorption Spectroscopy has been used to measure the optical response of multi- layers of water adsorbed on a cleaned and annealed Fe3O4(100) single crystal thin film on MgO(100) substrate in the grazing incidence geometry. Several features of the composite system have been observed. In particular, two derivative-type bands at 700 and 800 cm-1 have been attributed to the librations of ice, and an anti-absorption band at 200 cm-1 has been assigned to be hindered translations of ice.