Fidele Twagirayezu's project page

Theoretical and Experimental study of the Optical Properties of Fe doped Nickel oxides.

Fidele Twagirayezu

Texas State University at San Marcos, Department of Physics, RFM 3228, 601 University Drive, San Marcos, TX78666.

Fidele Twagirayezu

My research project is about both experimental and theoretical studies of materials properties of NiO and Fe-doped NiO. I use both computational techniques (Density Functional Theory (DFT) VASP code) and LAB instruments (VSM and ellipsometry). NiO is known to be a semiconductor for which metal vacancies act like acceptors. On the other hand, NiO with a large number of oxygen vacancies behaves more like a metal and has a low resistivity. It is this property that makes the material interesting for application in Resistive RAM memory devices. The effect of Fe doping on the optical, electrical, and magnetic properties is studied The solvability of Fe in oxygen deficient rocksalt NiO is much larger than 2% which is often quoted for stoichiometric NiO.

Fidele graduated and is a graduate PhD student at UCLA.

Publications:

[1] John Petersen, Fidele Twagirayezu, Pablo D. Borges, Luisa Scolfaro and Wilhelmus Geerts, "Ab initio study of oxygen vacancy effects on electronic and optical properties of NiO", MRS Advances 1, 37 (2016), pp. 2617-2622.

[2] John E. Petersen, Fidele Twagirayezu, Luisa M. Scolfaro, Pablo D. Borges, Wilhelmus J. Geerts, “Electronics and Optical properties of antiferromagnetic Iron doped NiO – A first principles study”, AIP Advances, vol. 7, 055711 1-5, 2017; doi:http://dx.doi.org/10.1063/1.4975493.

[3] Fidele J. Twagirayezu, Md. Abdul Ahad Talukder, Wilhelmus J. Geerts, "Magnetic Properties of RF sputtered NiO and Ni0.8Fe0.2O1-d samples grown on SiO2/Si substrates, accepted for publication in Materials Research Innovations, July 19 2018, https://doi.org/10.1080/14328917.2018.155879

[4] Binod D.C., Andres Oliva, Anival Ayala, Shankar Acharya, Fidele Twagirayezu, James Nick Talbert, Luisa M. Scolfaro, Wilhelmus J. Geerts, "Magnetic Properties of reactive co-sputtered NiFe-oxide samples", August 13, 2018, 6 page paper published in IEEE Trans. on Magn., DOI: 10.1109/TMAG.2018.2866788

[5] Fidele Twagirayezu, "Theoretical and Experimental study of the Optical Properties of Fe doped Nickel oxides", thesis Texas State University, San Marcos, Summer 2017 (thesis).

[6] Fidele J. Twagirayezu, Density functional theory study of the effect of Vanadium on electronic and optical properties of NiO, International Journal of Computational Materials Science and Engineering, 2019, https://doi.org/10.1142/S2047684119500076.

Presentations:

[7] Binod D.C., Andres Oliva, Anival Ayala, Shankar Acharya, Fidele Twagirayezu, James Nick Talbert, Luisa Scolfaro, Wilhelmus Geerts, “Magnetic Properties of reactive sputtered NiFe-oxide samples”, poster presentation International Conference on Magnetism 2018, July 18, San Francisco.

[8] D. C. Binod, Andres Oliva, Anival Ayala, Shankar Acharya, Fidele Twagirayezu, James Talbert, Luisa Scolfaro, Wilhelmus Geerts, "VSM measurements on NiFe-oxide samples", poster presentation at the Spring-2018 TSAPS meeting at Tarleton State University in Stephenville, march 23, 2018.

[9] Fidele Twagirayezu, Wilhelmus Geerts, Yubo Cui, "Optical Properties of Magnetron Sputtered Nickel Thin Films", oral presentation National APS-March Meeting, 2015, San Antonio, Texas. 

[10] Yubo Cui, Fidele Twagirayezu, Wilhelmus Geerts, Stefan Zollner, "IR Ellipsometry on RF sputtered Permalloy Oxide thin films", National APS-March Meeting, 2015, San Antonio, Texas.       

[11] Yubo Cui, Fidele Twagirayezu, Wilhelmus Geerts, "Optical Properties of Permalloy Oxide Grown by reactive RF magnetron sputtering", oral presentation at the 2014-Fall meeting of the Texas Section of the American Physical Society, October 17-19, College Station, 2014.

[12] Fidele Twagirayezu, Gabriel Leitao, Pablo D. Borges, Luisa Scolfaro, Wilhelmus Geerts, "Study of electronic structure of Fe-doped NiO  using  first principle calculations", oral presentation at the Seventh International Conference for Graduate Students at Texas State University, November 17 - 18, 2015; San Marcos, Texas.

[13] Gabriel Leitao, Fidele Twagirayezu, Pablo D. Borges, Luisa Scolfaro, Wilhelmus Geerts, "Band structure and density of states of antiferromagnetic and ferromagnetic iron (II) oxide by ab initio simulations", poster presentation at the Fall 2015 Joint Meeting of the Texas Section of the AAPT, Texas Section of the APS and Zone 13 of the Society of Physics Students, October 29 -31, 2015; Waco, Texas.

[14] Fidele Twagirayezu (Department of Physics, Texas State  University), Erik Bochove (Theoretical Physics group Air Force Research Laboratory) , "Modeling of Fiber Laser Beam Propagation through a Homogeneous Atmosphere", poster presentation at the Fall 2015 Joint Meeting of the Texas Section of the AAPT, Texas Section of the APS and Zone 13 of the Society of Physics Students, October 29 -31, 2015; Waco, Texas.

[15] Fidele Twagirayezu, "A new Mathematical Curve: A perfect Astroid or CS-Type Astroid", oral presentation at the Seventh International Conference for Graduate Students at Texas State University, November 17 - 18, 2015; San Marcos, Texas.

[16]John Petersen, Fidele Twagirayezu, Pablo D. Borges, Luisa Scolfaro, Wilhelmus Geerts, "First principles study of oxygen vacancies and iron impurities on electrical and optical properties of NiO", oral presentation at the National  APS March Meeting 2016, Friday, March 18, Baltimore, Maryland.

[17] Luisa Scolfaro, John Petersen,  Fidele Twagirayezu, Gabriel Leitao, Pablo Borges, Wilhelmus Johannes Geerts, "Electronic, Optical and Magnetic Properties of Iron Doped Nickel Oxide", oral presentation at 2016 MRS Meeting  and Exhibit, March 31, Phoenix Arizona.