Experimental and theoretical study of electronic and hyperfine properties of hydrogenated anatase (TiO$_2$): defects interplay and thermal stability

التفاصيل البيبلوغرافية
العنوان: Experimental and theoretical study of electronic and hyperfine properties of hydrogenated anatase (TiO$_2$): defects interplay and thermal stability
المؤلفون: Zyabkin, D. V., Gunnlaugsson, H. P., Goncalves, J. N., Bharuth-Ram, K., Qi, B., Unzueta, I., Naidoo, D., Mantovan, R., Masenda, H., Olafsson, S., Peters, G., Schell, J., Vetter, U., Dimitrova, A., Krischok, S., Schaaf, P.
سنة النشر: 2020
المجموعة: Condensed Matter
مصطلحات موضوعية: Condensed Matter - Materials Science
الوصف: In this study we report on the results from emission $^{57}$Fe M${\"o}$ssbauer Spectroscopy experiments, using dilute $^{57}$Mn implantation into pristine (TiO$_2$) and hydrogenated anatase held at temperatures between 300-700 K. Results of the electronic structure and local environment are complemented with ab-initio calculations. Upon implantation both Fe$^{2+}$ and Fe$^{3+}$ are observed in pristine anatase, where the latter demonstrates the spin-lattice relaxation. The spectra obtained for hydrogenated anatase show no Fe$^{3+}$ contribution, suggesting that hydrogen acts as a donor. Due to the low threshold, hydrogen diffuses out of the lattice. Thus showing a dynamic behavior on the time scale of the $^{57}$Fe 14.4 keV state. The surrounding oxygen vacancies favor the high-spin Fe$^{2+}$ state. The sample treated at room temperature shows two distinct processes of hydrogen motion. The motion commences with the interstitial hydrogen, followed by switching to the covalently bound state. Hydrogen out-diffusion is hindered by bulk defects, which could cause both processes to overlap. Supplementary UV-Vis and electrical conductivity measurements show an improved electrical conductivity and higher optical absorption after the hydrogenation. X-ray photoelectron spectroscopy at room temperature reveals that the sample hydrogenated at 573 K shows presence of both Ti$^{3+}$ and Ti$^{2+}$ states. This could imply that a significant amount of oxygen vacancies and -OH bonds are present in the samples. Theory suggests that in the anatase sample implanted with Mn(Fe), probes were located near equatorial vacancies as next-nearest-neighbours, whilst a metastable hydrogen configuration is responsible for the annealing behavior.
نوع الوثيقة: Working Paper
DOI: 10.1021/acs.jpcc.0c00085
URL الوصول: http://arxiv.org/abs/2003.07600
رقم الأكسشن: edsarx.2003.07600
قاعدة البيانات: arXiv
الوصف
DOI:10.1021/acs.jpcc.0c00085