Manuel Roldan Gutierrez
-
-
Physical Science Building B-Wing 155 Tempe, AZ 85287
-
Mail code: 8301Campus: Tempe
-
Before joining the ASU staff, Manuel Roldan Gutierrez received his doctorate in materials science from the University of Seville (Spain) for his work in synthesis by ball milling and control rate thermal analysis of ceramics in the (Ti,V,C,N) group. Including characterization by x-ray diffractometry (XRD), scanning electron microscopy (SEM), dilatometry, micro-hardness and extended X-ray absorption fine structure (EXAFS) with Dr. Concepcion Real. Afterwards, he became a research associate for almost five years at the University Complutense of Madrid, Spain, although he was permanently located at the STEM Group in Oak Ridge National Laboratory (ORNL), under the supervision of Dr. Stephen J. Pennycook and Dr. Maria Varela. At ORNL, he has been trained in advanced electron microscopy techniques (including both imaging and spectroscopy), becoming an expert in obtaining structural and chemical information in complex materials from aberration-corrected scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS). He is also familiar with other spectroscopic techniques such as electron dispersion X-ray spectroscopy (EDX). Then, he spent two years in the Imaging characterization Core Lab in KAUST (Saudi Arabia) where he worked for the first time in a user facility providing services to faculty and external companies.
- Ph.D. Materials Science, University of Seville, Spain 2009. Dissertation: "Synthesis and Characterization of binary and ternary nitrides in the system (Ti, V, C, and N)."
- Bachelor's degree. Chemistry, University of Seville, Spain 2003
Advances in nanotechnology have resulted in materials where properties are very different from their bulk, such as epitaxial thin films or other reduced dimensionality systems. The aims is to measure and analyze in a quantitative fashion structure-property correlations in such materials using advanced electron microscopy techniques, with the objective of contributing to the design of materials with properties specifically tailored for electronic, magnetic, optical, and energy applications.
Publications
41. Er-Jia Guo, R. Desautels, D. Keavney, M.A. Roldan, B.J. Kirby, D. Lee, Z. Liao, T. Charlton, A. Herklotz, T.Z. Ward, M.R. Fitzsimmons, H.N. Lee “Nanoscale ferroelastic twins formed in strained LaCoO3 films”. Science Advances 5, 3 (2019).
40. Y. Luengo, M.A. Roldan, M. Varela, F. Herranz, M. Morales, S. Veintemillas-Verdaguer “Doped-Iron Oxide Nanocrystals Synthesized by One-Step Aqueous Route for Multi-Imaging Purposes”. The Journal of Physical Chemistry C 123, 12, 7356-7365 (2019).
39. L. Bégon-Lours, V. Rouco, Qiao Qiao, A. Sander, M.A. Roldán, R. Bernard, J. Trastoy, A. Crassous, E. Jacquet, K. Bouzehouane, M. Bibes, J. Santamaría, A. Barthélémy, M. Varela, J. E. Villegas “Factors limiting ferroelectric field-effect doping in complex oxide heterostructures”. Phys. Rev. Materials 2, 084405 (2018).
38. Er-Jia Guo, M.A. Roldan, X. Sang, S. Okamoto, T. Charlton, H. Ambaye, H.N. Lee, and M.R. Fitzsimmons “Influence of chemical composition and crystallographic orientation on the interfacial magnetism in BiFeO3/La1−xSrxMnO3 superlattices”. Phys. Rev. Materials 2, 114404 (2018).
37. R. Al-Shareef, M. Harb, Y. Saih, S. Ould-Chikh, M.A. Roldan, D.H. Anjum, E. Guyonnet, J.P. Candy, D.Y. Jan, S.F. Abdo, A. Aguilar-Tapia, O. Proux, J.L. Hazemann, J.M. Basset. “Understanding of the structure activity relationship of PtPd bimetallic catalysts prepared by surface organometallic chemistry and ion exchange during the reaction of iso-butane with hydrogen”. Journal of Catalysis 363 34-51 (2018).
36. V. Tzitzios, K. Dimos, S.M. Alhassan, R. Mishra, A. Kouloumpis, D. Gournis, N. Boukos, M. Roldan, J.C. Idrobo, M.A. Karakassides, G. Basina, Y. Alwahedi, H.J. Kim, M. Fardis, S. Pantelides, G. Papavasileiou. “Facile MoS2 growth on reduced graphene-oxide via liquid phase method”. Frontiers in Materials 5, 29 (2018).
35. Er-Jia Guo, M. A. Roldan, T. Charlton, Z, Liao, Q. Zheng, H. Ambaye, A. Herklotz, Z. Gai, T. Zac Ward, H. N. Lee, and M. R. Fitzsimmons, “Removal of Magnetic Dead Layer by Geometric Design” accepted in Advanced Functional Materials. Accepted (2018).
34. C. M. Jimenez, D. Aggad, J. G. Croissant, K. Tresfield, D. Laurencin, D. Berthomieu, N. Cubedo, M. Rossel, S. Alsaiari, D. H. Anjum, R. Sougrat, M. A. Roldan-Gutierrez, S. Richeter, E. Oliviero, L. Raehm, C. Charnay, X. Cattoën, S. Clément, M. Wong C. Man, M. Maynadier, V. Chaleix, V. Sol, M. Garcia, M. Gary-Bobo, N. M. Khashab, N. Bettache,* and J. O. Durand. “Porous Porphyrin-Based Organosilica Nanoparticles for NIR Two-Photon Photodynamic Therapy and Gene Delivery in Zebrafish”. Advanced Functional Materials 1800235 (2018). 33. Q. Wang, A. P. Chen, E. J. Guo, M. A. Roldan, Q. X. Jia, and M. R. Fitzsimmons. “Upper limit for the effect of elastic bending stress on the saturation magnetization of La0.8Sr0.2MnO3”. Physical Review B. 97, 014437 (2018). 32. I.A. Ajia, P.R. Edwards, Y. Pak, E. Belekov, M.A. Roldan, N. Wei, Z. Liu, R.W. Martin, and I.S Roqan. “Generated carrier dynamics in V-pit enhanced InGaN/GaN light emitting diode”. ACS Photonics. 5. 820-826 (2017). 31. J. Gazquez , M. Stengel, R. Mishra, M. Scigaj, M. Varela, M.A. Roldan, J. Fontcuberta, F.Sánchez, and G. Herranz. “Competition between polar and nonpolar lattice distortions in oxide quantum wells: a new critical thickness at polar interfaces”. Physical Review Letters 119 106102 (2017). 30. E. J. Guo, J. R. Petrie, M. A. Roldan, Q. Li, R. D. Desautels, T. Charlton, A. Herklotz, J. Nichols, J. van Lierop, J. W. Freeland, S. V. Kalinin, H. N. Lee, M. R. Fitzsimmons. “Spatially Resolved Large Magnetization in Ultrathin BiFeO3”. Advanced Materials 1700790 (2017). 29. J. Gázquez, G. Sánchez-Santolino, N. Biškup, M. A. Roldan, M. Cabero, S. J. Pennycook, M. Varela. “Applications of STEM-EELS to complex oxides”. Materials Science in Semiconductor Processing. 65 45-63 (2017). 28. M. M. Muhammed, M. A. Roldan, Y. Yamashita, S.-L. Sahonta, I. A. Ajia, K. Iizuka, A. Kuramata, C.J. Humphreys, and I. S. Roqan. “High-quality III-nitride films on conductive, transparent (2 01)oriented β-Ga2O3 using a GaN buffer layer”. Scientific Reports 6, 29747 (2016). 27. C. D. Amos, M. A. Roldan, M. Varela, J. B. Goodenough, and P. J. Ferreira. “Revealing the Reconstructed Surface of Li[Mn2]O4”. Nano Letters. 16 (5) 2899-2906 (2016). 26. M. C. Spadaro, S. D'Addato, Luches, S. Valeri, V. Grillo,E. Rotunno, M. A. Roldan, S. J. Pennycook, A. M. Ferretti, E. Capetti. “Tunability of exchange bias in Ni@NiO core-shell nanoparticles obtained by sequential layer deposition”. Nanotechnology 26 405704 (2015). 25. P. Jain, Q. Wang, M. Roldan, A. Glavic, V. Lauter, C. Urban, Z Bi, T. Ahmed, J. Zhu, M. Varela, Q. X. Jia, M. R. Fitzsimmons. “Synthetic magnetoelectric coupling in a nanocomposite multiferroic”. Scientific Reports 5 9089 (2015). 24. M. A. Roldan, M. D. Alcala, C. Real. “Mechanically induced self-propagating reaction of vanadium carbonitride”. Ceramics International 41 4688-4695 (2015). 23. L. Yedra, E. Xuriguera, M. Estrader, A. López-Ortega, M.D. Baró ,J. Nogués, M. A. Roldan, M. Varela, S. Estradé and F. Peiró. “Oxide Wizard: an EELS application to quantitatively characterize the oxidation state of transition metal edges”. Microscopy and Microanalysis. 20 698-705 (2014 22. M. A. Roldan, M. P. Oxley, Q. A. Li, H. Zheng, K. E. Gray, J. F. Mitchell, S. J. Pennycook, and M. Varela. “Atomic scale studies of La/Sr ordering in colossal magnetoresistant La2-2xSr1+2xMn2O7 single crystals”. Microscopy and Microanalysis. 20 1791-1797 (2014). 21. M. Laskar, D. N. Nath, L. Ma, E. Lee, C. H. Lee, T. Kent, Z. Yang, R. Mishra, M. A. Roldan, J. C. Idrobo, S. T. Pantelides, S. J. Pennycook, R. Myers, Y. Wu and S. Rajan. “p-type doping in CVD grown MoS2 using Nb”, Applied Physics Letters. 104 092104 (2014). 20. P. Wadley, A. Crespi, J. Gazquez, M.A. Roldan, P. Garcıa, V. Novak, R. Campion, T. Jungwirth, C. Rinaldi, X. Martı, V. Holy, C. Frontera and J. Rius. “Obtaining the structure factors for an epitaxial film using Cu X-ray radiation”, Journal of Applied Crystallography 46, 1749-1754 (2013). 19. E. M. F. Vieira, J. Martın-Sanchez, M. A. Roldan, M. Varela, M. Buljan, S. Bernstorff, N. P. Barradas, N. Franco, M. R. Correia, A. G. Rolo, S. J. Pennycook, S. I. Molina, E. Alves, A. Chahboun and M. J. M. Gomes. “Influence of RF-sputtering power on formation of vertically stacked Si1−xGex nanocrystals between ultra-thin amorphous Al2O3 layers: structural and photoluminescence properties” J. Phys. D: Appl. Phys. 46, 385301 (2013). 18. P. Wadley, V. Novak, R.P. Campion, C. Rinaldi, X. Marti, H. Reichlova, J. Zelezny, J. Gazquez, M. A. Roldan, M. Varela, D. Khalyavin, S. Langridge, D. Kriegner, F. Maca, J. Masek, R. Bertacco, V. Holy, A. W. Rushforth, K. W. Edmonds, B. L. Gallagher, C. T. Foxon, J. Wunderlich, and T. Jungwirth. “Tetragonal phase of epitaxial room-temperature antiferromagnet CuMnAs”. Nature Communications 4, 2322 (2013). 17. D. F. Reyes, D. Gonzales, F. Bastiman, L. Dominguez, C. J. Hunter, E. Guerrero, M. A. Roldan, A. Mayoral, J. P. R. David and D. L. Sales. “Photoluminescence Enhancement of InAs(Bi) Quantum Dots by Bi Clustering”. Applied Physics Express 6, 042103 (2013). 16. D. Timmerman, S. Saeed, T. Gregorkiewicz, M. A. Roldan, and S. I. Molina. “Investigation of saturation and excitation behavior of 1.5 μm emission from Er3+ ions in SiO2 sensitized with Si nanocrystals”. Physica Status Solidi C, 1-6, 201200311 (2012). 15. S. Singh, M. R. Fitzsimmons, T. Lookman, H. Jeen, A. Biswas, M.A. Roldan, and M. Varela “Role of elastic bending stress on magnetism of a manganite thin film studied by polarized neutron reflectometry”. Physical Review B, 85 (21) 214440 (2012). 14. S.R.C. Pinto, M Buljan, A. Chahboun, M.A. Roldan, S. Bernstorff, M. Varela, S.J. Pennycook, N.P. Barradas, E. Alves, S.I. Molina, M.M.D. Ramos, M.J.M. Gomes. “Tuning Properties of Gequantum dots superlattices in amorphous silica matrix through deposition conditions”. Journal of Applied Physics 111 (7) 074316 (2012). 13. S. Singh, M. R. Fitzsimmons, T. Lookman,, J. D. Thompson, H. Jeen, A. Biswas, M. A. Roldan, M. Varela. “Magnetic Nonuniformity and Thermal Hysteresis of Magnetism in a Manganite Thin Film”. Physical Review Letters, 108 (7) 077207 (2012). 12. M.A. Roldan, M.D. Alcala, C. Real. “Characterisation of ternary TixV1-xNy nitride prepared by mechanosynthesis”. Ceramics International 38 687-693 (2012). 11. D. Alonso-Alvarez, B. Alen, J.M. Ripalda, J.M. Llorens, A.G. Toboada, F. Briones, M.A. Roldan, J. Hernandez-Saz, D. Hernandez-Maldonado, M. Herrera, S.I. Molina. “Strain balanced quantum Posts”. Applied Physics Letters, 98 (17) 173106 (2011). 10. M.A. Roldan, M.D. Alcala, A. Ortega, C. Real. “Synthesis and characterization of titanium-vanadium ternary nitride (TixV1-xN)”. Boletin de la Sociedad Española de Ceramica y Vidrio, 50 31-40 (2011). 9. Alonso-Alvarez, D. Alén, B. Ripalda, J.M. Taboada, A.G. Llorens, J.M. González, Y. González, L. Briones, F. Antolín, E. Ramiro, I. Martí, A. Luque, A., M.A. Roldán, Hernandez-Saz, J. Herrera, M. Molina, S.I. “Strain balanced quantum posts for intermediate band solar cells”. IEEE Photovoltaic Specialists Conference, 1 928- 933 (2010). 8. M.A. Roldan, V. Lopez-Flores, M.D. Alcala, A. Ortega, C. Real. “Mechanochemical synthesis of vanadium nitride”. J. European Ceramic Society 30 2099-2107 (2010). 7. E. Deprez, M.A. Muños-Marquez, M.A Roldan, C. Prestipino, M. Bonatto, U. Bosenberq, M. Dornheim, R. Bormann, A. Fernandez. “Oxidation State and Local Structure of Ti-Based Additives in the Reactive Hydride Composite 2 LiBH(4) + MgH2”. J. Phys. Chem 114 (7) 3309-3317 (2010). 6. V. Lopez-Flores, M.A. Roldan, C. Real, A. Muñoz-Paez, G. R. Castro. “Polymorphic transformation from body-centered to face-centered cubic vanadium metal during mechanosynthesis of nanostructured vanadium nitride determined by extended x-ray absorption fine structure spectroscopy”. J. App.Phys.104 (2) 023519 (2008). 5. G. de Portu, L. Micele, M.A.R. Gutierrez, L. Puppulin, M.C. Munisso, C. Melandri, G. Pezzotti. “New method to measure thermal shock resistance in ceramics using a Piezo-spectroscopic technique”. Journal of the American Ceramic Society 91 (4) 1316-1318 (2008). 4. M.A. Roldan, A. Ortega, I. Palencia, C. Real. “Synthesis by reactive grinding of molybdenum iron bimetallic nitride”. Revista de Metalurgia 44 (1) 13-18 (2008). 3. C. Real, M.A. Roldan, M.D. Alcala, A. Ortega. “Synthesis of nanocrystalline chromium nitride powder by mechanical processing”. Journal of the American Ceramic Society 90 (10) 3085-3090 (2007). 2. A. Ortega, M.A. Roldan, C. Real. “Carbothermal Synthesis of Vanadium Nitride (VN): Kinetics and Mechanism”. Int. J. Chem. Kinetics 38 (6) 369-375 (2006). 1. A. Ortega, M.A. Roldan, C. Real. “Carbothermal Synthesis of Titanium Nitride (TiN): Kinetics and Mechanism”. Int. J. Chem. Kinetics 37 566-571 (2005) Conference Proceedings 7. D. H. Anjum, A. Samal, M. A. Roldan. “Characterization of core/shell bi-metallic cube-shaped nanoparticles with scanning transmission electron microscopy”. Microscopy and Microanalysis 21 (S3), 1069-1070 (2015). 6. Y. Gao, M. A. Roldan, J. Zhang, L. Qiao, M. Chi, D. Mandrus, X. Shen, M. F. Chisholm, D. J. Singh, G. Cao. “Atomic Resolution STEM-EELS study of transition electronic localization state induced by strain”. Microscopy and Microanalysis 21 (S3), 617-618 (2015).
5. C. Amos, M.A. Roldan, M. Varela, J. B. Goodenough, P. J. Ferreira. “Understanding the Surface Structure of LiMn 2 O4 Spinel Cathodes with Aberration-Corrected HAADF STEM and EELS”. Microscopy and Microanalysis 21 (S3), 1375-1376 (2015). 4. M. A. Roldan, J Salafranca, R Ishikawa, R Mishra, A Lopez-Ortega, M Estrader, G Salazar-Alvarez, J. Nogues, SJ Pennycook, M Varela. “Atomic-Resolution Monitoring of Structural Phase Transition in Bi-magnetic Core/Shell Oxide Nanoparticles”. Microscopy and Microanalysis 20 (S3) 106-107 (2014). 3. Q. Qiao, P. Mirtchev, Y. Zhang, M. A. Roldan, M. Varela, S. T. Pantelides, D. D. Perovic , G. Ozin and S. J. Pennycook. “Atomic and Electronic Structure of γFe2O3/Cu2O Heterostructured Nanocrystals”. Microscopy and Microanalysis 20 (S3) 410-411 (2014). 2. M.A. Roldan, W. Siemons, J. Salafranca, M. Varela, A.R. Lupini, S.J. Pennycook and H.M. Christen. ”Interface Magnetism in LaMnO3 / SrTiO3 Superlattices: Influence of Oxygen Octahedral Tilts”. Microscopy and Microanalysis 19 (S2) 1916-1917 (2013). 1. M.A. Roldan, D. Hernández-Maldonado, J. Hernandez-Saz, M. Herrera, M. Guerrero, P. Galindo, D. Alonso-Alvarez, J. Ripalda, B. Alen, Y. Gonzalez, M. Varela, S.J. Pennycook, S. Molina. “Compositional Mapping by Z-Contrast Imaging”. Microscopy and Microanalysis 17 (S2) 17281729 (2011). Conference and Workshop Contributions 24. The 16th European Microscopy Conference (EMC2016) Lyon, France. August 28th- September 2nd, 2016. M. A. Roldan, M. P. Oxley, Q. A. Li, H. Zheng, K. E. Gray, J. F. Mitchell, S. J. Pennycook, and M. Varela. “Atomic scale studies of La/Sr ordering in La 2-2x Sr 1+2x Mn 2 O 7 single crystals”. Poster. 23. Euromat 2015. Warsaw, Poland. September 21-24, 2015. M. A. Roldan, D. H. Anjum, R. Sougrat. “Role of Electron Spectroscopy analysis with TEM for the Characterization of Core/Shell Nanoparticles”. Oral Presentation. 22. Microscopy and Microanalysis 2015. Portland, OR. August 2-6, 2015. D. H. Anjum, A. Samal, M. A. Roldan. “Characterization of core/shell bi-metallic cube-shaped nanoparticles with scanning transmission electron micrsocopy”. Poster 21. Microscopy and Microanalysis 2015. Portland, OR. August 2-6, 2015. Y. Gao, M. A. Roldan, J. Zhang, L. Qiao, M. Chi, D. Mandrus, X. Shen, M. F. Chisholm, D. J. Singh, G. Cao. “Atomic Resolution STEM-EELS study of transition electronic localization state induced by strain”. Oral Presentation. 20. ICCE-23 Conference. Chengdu China. ICCE-23 July 12-18, 2015. M.A. Roldan, J. Salafranca, R. Ishikawa, R. Mishra, A. López-Ortega, M. Estrader, G Salazar-Alvarez, J. Nogues, S. J. Pennycook and M. Varela. “STEM-EELS Study of Structural Phase Transition in Core/Shell Bi-magnetic Oxide Nanoparticles”. Invited talk. 19. 18th International Microscopy Congress. Prague, Czech Republic. 7-12 September, 2014. M.A. Roldan, M. Varela, J. Salafranca, A.R. Lupini, W. Siemons, S.J. Pennycook and H.M. Christen. “Oxygen Octahedral Tilts: In the Origin of Ferromagnetism at Insulating LaMnO3 and SrTiO3 Interfaces”. Oral Presentation. 18. Microscopy and Microanalysis 2014. Hartford, CT. August 3-7, 2014. M.A. Roldan, J. Salafranca, R. Ishikawa, A. López-Ortega, M. Estrader, J. Nogues, S. J. Pennycook, M. Varela. “AtomicResolution Monitoring of Structural Phase Transitions in Bi-magnetic Core/Shell Oxide Nanoparticles”. Oral Presentation. 17. XXXVII Encontro Nacional de Fisica da Materia Condensada. Costa do Sauipe, Brazil. May 12-16, 2014. J. Nogues, M. Estrader, S. Estarde, F. Peiro, A. Lopez-Ortega, I.V. Golosovsky, G. SalazarAlvarez, M. Vasilakaki, K. N. Trohidou, M.A. Roldan, M. Varela, D. C. Stanley, M. Sinko, M. J. Pechan, D. J. Keavney, M. Laver, K. L. Krycka, J. A. Borchers, S. Surinach, M. D. Baro.“Antiferromagnetic coupling in ferrimagnetic hard-soft core/shell nanoparticles.” Oral Presentation. 16. 58th Annual Conference on Magnetism and Magnetic Materials. Denver, CO. November 5-8, 2013. M. R. Fitzsimmons, S. Singh, T. Lookman, H. Jeen, M. A. Roldan, M. Varela, A. Biswas. “Magnetic non-uniformity in (La0.4Pr0.6)0.67Ca0.33MnO3 films and measurement of the strainmagnetization coupling coefficient.” Oral Presentation. 15. 17th International Conference on Crystal Growth and Epitaxy. Warsaw, Poland. August 11-16, 2013. R. P. Campion, P. Wadley, V. Novak, C. Rinaldi, X. Martı, H. Reichlova, J. Zelezny, J. Gazquez, M. A. Roldan, M. Varela, D. Khalyavin, S. Langridge, D. Kriegner, F. Maca, J. Masek, R. Bertacco, V. Holy, A. W. Rushforth, K.W. Edmonds, B. L. Gallagher, C. T. Foxon, J. Wunderlich, and T. Jungwirth. “From GaMnAs to CuMnAs: growth by Molecular Beam Epitaxy (MBE)” .Oral Presentation 14. Microscopy and Microanalysis 2013. Indianapolis, IN. August 4-8, 2013. M.A. Roldan, W. Siemons, J. Salafranca, M. Varela, A.R. Lupini, S.J. Pennycook and H.M. Christen. ”Interface Magnetism in LaMnO3 / SrTiO3 Superlattices: Influence of Oxygen Octahedral Tilts”. Oral Presentation. 13. Microscopy and Microanalysis 2012. Phoenix, AZ. July 29-August 2, 2013. M.A. Roldan, M.P. Oxley, K.E. Gray, Q.A. Li, H. Zheng, J.F. Mitchell S.J. Pennycook , M. Varela. “Atomic Resolution Quantification of Chemical Ordering in a Layered Perovskite”. Poster.
12. EMRS Spring 2012. Strasbourg, France. May 14-18, 2012. E.M.F.Vieira, J. Martín-Sánchez , S. Levichev, M. Buljan, S. Bernstorff, M. A. Roldan, A.G. Rolo, A. Chahboun, S.I. Molina, M. Varela, S. J. Pennycook, M.J.M. Gomes "Evidence of self-organized Si1-xGex nanoparticles in Al2O3 multilayer structure". Oral Presentation.
11. EMRS Spring 2012. Strasbourg, France. May 14-18, 2012. E. M. F. Vieira, S. R. C. Pinto, J. MartinSanchez, S. Levichev, M. Buljan, S. Bernstorff, M.A. Roldan, S. I. Molina, I. Capan, A.G. Rolo, O.Conde, A. Chahboun, E. Alves, N. Barradas, M. Varela , S. J. Pennycook,M. J. M. Gomes "SiGe and Ge nanocrystals embedded in dielectrics for carrier retention applications". Poster.
10. EMRS Spring 2012. Strasbourg, France. May 14-18, 2012. D. F. Reyes, F. Bastiman, D. L. Sales, C. Hunter, M.A. Roldán, A. Mayoral, M. Varela, S.J. Pennycook, S. I. Molina and D. González. “Bismuth incorporation into InAs/GaAs Quantum Dots”. Oral Presentation 9. Microscopy and Microanalysis 2011. Nashville, TN. August 7-11, 2011. M.A. Roldan, D. Hernandez, M. Herrera, D. Alonso, J.M. Ripalda, B. Alen, M. Guerrero, J. Hernandez, M. Varela, S.J. Pennycook, S.I. Molina. “Compositional Mapping by Z-Contrast Imaging”. Poster. 8. NANOSCIENCE - HPC2011. Bilbao, Spain. April 11-14 2011. M. P. Guerrero-Lebrero, P.L. Galindo, J. Pizarro, D.L. Sales, M.A. Roldan, M. Varela, S.J. Pennycook, S.I. Molina,.”Parallel software for characterization of large structures using HAADF-STEM with effect of spatial incoherence corrected”. Oral Presentation. 7. 2nd International Workshop on Bismuth-Containing Semiconductors: Theory, Simulation, and Experiment. Guildford, United Kingdom. July 18-20 2011. D. L. Sales, D. F. Reyes, M. A. Roldán, S. I. Molina, D. González, F. Bastiman, C. Hunter. “Transmission Electron Microscopy characterization of InAs(Bi)/GaAs QDs”. 6. Conference Record of the IEEE Photovoltaic Specialists Conference. Honolulu, Hawai. June 20-25, 2010. J.Hernandez, M. Herrera, S.I. Molina, M. A. Roldan, et al. “Strain Balanced Quantum Posts for Intermediate Band Solar Cells”. Poster. 5. SR User Meeting, Diamond Light Source. Oxford, United Kingdom. September 13-14, 2007. M. A. Roldán, V. López, A. Muñoz, C. Real.“HRPD vs. Cu Kα XRD, Vanadium Nitride Obtained by Ball Milling”. Poster. 4. III Reunión Anual AUSE Jaca, Spain. July 9-11, 2007 V. Lopez-Flores, M.A. Roldán, C. Real-Perez, A. Muñoz-Paez. “EXAFS study of ternary nitrides obtained by mechanosynthesis”. Poster. 3. 10th Int. Conf. and Exhibition of European ceramic society Berlin, Germany. June 17-21, 2007. G. de Portu, L. Micele, M.A. Roldan, L. Puppulin, M.C. Munisso, C. Melandri, G. Pezzotti. “Piezospectroscopic technique for assessing thermal shock cracks in alumina-zirconia composites”.Poster. 2. XLV Congreso de la SECV Sevilla, Spain. November 2 – 5, 2005 M. A. Roldán, C. Real. “Síntesis de Nitruro de molibdeno y hierro mediante mecanosíntesis”. Poster. 1. VIII Congreso Nacional de Materiales. Valencia, Spain. June 15 -17, 2004. C. Real, M. A. Roldán, A. Ortega, M. D. Alcalá. “Influence of the synthesis method in the structure and texture of VN”. Poster.