@misc{pearce_wilkins_paskova_ivanisevic_2015, title={A review of in situ surface functionalization of gallium nitride via beaker wet chemistry}, volume={30}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2015.132}, number={19}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Pearce, Brady L. and Wilkins, Stewart J. and Paskova, Tania and Ivanisevic, Albena}, year={2015}, month={Oct}, pages={2859–2870} }
 @article{wilkins_paskova_reynolds_ivanisevic_2015, title={Comparison of the Stability of Functionalized GaN and GaP}, volume={16}, ISSN={["1439-7641"]}, DOI={10.1002/cphc.201500105}, abstractNote={Surface functionalization via 1 H,1 H,2 H,2H-perfluoro octanephosphonic acid was done in the presence of phosphoric acid to provide a simplified surface passivation technique for gallium nitride (GaN) and gallium phosphide (GaP). In an effort to identify the leading causes of surface instabilities, hydrogen peroxide was utilized as an additional chemical modification to cap unsatisfied bonds. The stability of the surfaces was studied in an aqueous environment and subsequently characterized. A physical characterization was carried out to evaluate the surface roughness and water hydrophobicity pre and post stability testing via atomic force microscopy and water goniometry. Surface-chemistry changes and solution leaching were quantified by X-ray photoelectron spectroscopy and inductively coupled plasma mass spectrometry. The results indicate a sensitivity to hydroxyl terminated species for both GaN and GaP under aqueous environments, as the increase of the degree of leaching was more significant for hydrogen peroxide treated samples. The results support the notion that hydroxyl species act as precursors to gallium oxide formation and lead to subsequent instability in aqueous solutions.}, number={8}, journal={CHEMPHYSCHEM}, author={Wilkins, Stewart J. and Paskova, Tania and Reynolds, C. Lewis, Jr. and Ivanisevic, Albena}, year={2015}, month={Jun}, pages={1687–1694} }
 @article{pearce_wilkins_rahn_ivanisevic_2015, title={In situ functionalization of gallium nitride powder with a porphyrin dye}, volume={30}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2015.152}, number={19}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Pearce, Brady L. and Wilkins, Stewart J. and Rahn, Matthew S. and Ivanisevic, Albena}, year={2015}, month={Oct}, pages={2910–2918} }
 @article{wilkins_paskova_ivanisevic_2015, title={Modified surface chemistry, potential, and optical properties of polar gallium nitride via long chained phosphonic acids}, volume={327}, ISSN={["1873-5584"]}, DOI={10.1016/j.apsusc.2014.11.179}, abstractNote={Surface potential, chemistry, topography, and optical properties were modulated utilizing the attachment of phosphonic acids (11-mercaptoundecylphosphonic acid, 1H,1H,2H,2H-perfluorooctanephosphonic acid, and 1,8-octanediphosphonic acid) with phosphoric acid to polar (c-plane) GaN. These changes were identified using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) with kelvin probe force microscopy (KPFM), photoluminescence (PL), and water contact angle. The results indicated that the attachment of phosphonic groups to gallium nitride strongly depends on the formation of a native oxide layer and subsequent passivation. It was seen that a fluorine terminated phosphonic acid increased the overall surface oxide versus other groups, as well as reduced the surface potential and improved the photoluminescence relative to other treatments. Sulfur terminated phosphonic acid demonstrated a similar reduction in surface potential and oxide formation to fluorine based phosphonic acid; however, improvements of optical luminescence on the same scale were not achieved.}, journal={APPLIED SURFACE SCIENCE}, author={Wilkins, Stewart J. and Paskova, Tania and Ivanisevic, Albena}, year={2015}, month={Feb}, pages={498–503} }
 @article{wilkins_slomski_paskova_weyher_ivanisevic_2015, title={Modulated optical sensitivity with nanostructured gallium nitride}, volume={106}, ISSN={["1077-3118"]}, DOI={10.1063/1.4918739}, abstractNote={Surface functionalization via etching of high aspect ratio gallium nitride (GaN) nanostructures provides a way to modulate the optical properties in addition to properties gained from unique topographical formations. In this study, planar layered (heteroepitaxy) and bulk free-standing gallium nitride were modified via a phosphonic acid (1H,1H,2H,2H-perfluorooctanephosphonic acid) assisted phosphoric acid etch in conjunction with an aqueous KOH + K2S2O8 formed gallium nitride nanostructured surface. Despite the high defect concentrations in the thin planar and nanostructured GaN layer, the nanostructured GaN sample produced improved photoluminescence intensities versus the high quality bulk free-standing gallium nitride. Subsequent treatments with additive and additive-free phosphoric etches provided a means of additional optical manipulation in the form of red-shifting the near-band-edge (NBE) emission of the nanostructured GaN sample and increasing the maximum NBE photoluminescence intensity.}, number={15}, journal={APPLIED PHYSICS LETTERS}, author={Wilkins, S. J. and Slomski, M. J. and Paskova, T. and Weyher, J. L. and Ivanisevic, A.}, year={2015}, month={Apr} }
 @article{wilkins_paskova_ivanisevic_2013, title={Effect of etching with cysteamine assisted phosphoric acid on gallium nitride surface oxide formation}, volume={114}, ISSN={["1089-7550"]}, DOI={10.1063/1.4817899}, abstractNote={In-situ functionalization of polar GaN was performed by adding cysteamine to a phosphoric acid etchant in order to study its effect on photoluminescence and oxide formation on the surfaces. The functionalization was characterized by atomic force microscopy, x-ray photoelectron spectroscopy, photoluminescence (PL), and water contact angle measurements. Two sets of polar GaN samples with different dislocation densities were evaluated, thin GaN layers residing on sapphire and thick free-standing GaN separated from sapphire substrate aiming to reveal the effect of material quality on in-situ functionalization. The addition of cysteamine to the phosphoric acid solution was found to result in: (i) decreased surface roughness, (ii) no change to hydrophobicity, (iii) decreased oxygen content especially at high-temperature treatments. The effect of the in-situ functionalization on the PL efficiency was more pronounced in the free-standing sample than in the film residing on the sapphire, which was attributed to a higher crystal quality free from strain.}, number={6}, journal={JOURNAL OF APPLIED PHYSICS}, author={Wilkins, S. J. and Paskova, T. and Ivanisevic, A.}, year={2013}, month={Aug} }