Modification of the Surface Properties of Al<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N Substrates
with Gradient Aluminum Composition Using Wet Chemical Treatments
Sara Gleco
Oleksandr Romanyuk
Ivan Gordeev
Karla Kuldová
Tania Paskova
Albena Ivanisevic
10.1021/acsomega.9b01467.s001
https://acs.figshare.com/articles/journal_contribution/Modification_of_the_Surface_Properties_of_Al_sub_i_x_i_sub_Ga_sub_1_i_x_i_sub_N_Substrates_with_Gradient_Aluminum_Composition_Using_Wet_Chemical_Treatments/8797703
The
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 Al<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>N film (0.173 ≤ <i>x</i> ≤ 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,
Ga<sub>2</sub>O<sub>3</sub> and Al<sub>2</sub>O<sub>3</sub> 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.
2019-07-08 08:13:18
hydrogen peroxide pretreatment
material
chemical treatments
Al content
Ga 2 O 3
Kelvin probe force microscopy measurements
Wet Chemical Treatments
chemical treatment
gradient aluminum content
surface properties
surface charge trends
phosphoric acid
Al 2 O 3 content
oxide-based nanostructured formations
Gradient Aluminum Composition
functionalization
strain-sensitive Raman peaks
X-ray photoelectron spectroscopy