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Modification of the Surface Properties of AlxGa1–xN Substrates with Gradient Aluminum Composition Using Wet Chemical Treatments
journal contribution
posted on 2019-07-08, 08:13 authored by Sara Gleco, Oleksandr Romanyuk, Ivan Gordeev, Karla Kuldová, Tania Paskova, Albena IvanisevicThe
surface properties of biomolecular gradients are widely known
to be important for controlling cell dynamics, but there is a lack
of platforms for studying them in vitro using inorganic materials.
The changes in various surface properties of an AlxGa1–xN film (0.173 ≤ x ≤ 0.220) with gradient aluminum content were quantified
to demonstrate the ability to modify interfacial characteristics.
Four wet chemical treatments were used to modify the surface of the
film: (i) oxide passivation by hydrogen peroxide, (ii) two-step functionalization
with a carboxylic acid following hydrogen peroxide pretreatment, (iii)
phosphoric acid etch, and (iv) in situ functionalization with a phosphonic
acid in phosphoric acid. The characterization confirmed changes in
the topography, nanostructures, and hydrophobicity after chemical
treatment. Additionally, X-ray photoelectron spectroscopy was used
to confirm that the chemical composition of the surfaces, in particular,
Ga2O3 and Al2O3 content,
was dependent on both the chemical treatment and the Al content of
the gradient. Spectroscopic evaluation showed red shifts in strain-sensitive
Raman peaks as the Al content gradually increased, but the same peaks
blue-shifted after chemical treatment. Kelvin probe force microscopy
measurements demonstrated that one can modify the surface charge using
the chemical treatments. There were no predictable or controllable
surface charge trends because of the spontaneous oxide-based nanostructured
formations of the bulk material that varied based on treatment and
were defect-dependent. The reported methodology and characterization
can be utilized in future interfacial studies that rely on water-based
wet chemical functionalization of inorganic materials.
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hydrogen peroxide pretreatmentmaterialchemical treatmentsAl contentGa 2 O 3Kelvin probe force microscopy measurementsWet Chemical Treatmentschemical treatmentgradient aluminum contentsurface propertiessurface charge trendsphosphoric acidAl 2 O 3 contentoxide-based nanostructured formationsGradient Aluminum Compositionfunctionalizationstrain-sensitive Raman peaksX-ray photoelectron spectroscopy
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