Magnetism in dilute magnetic semiconductors

We have resolved a longstanding issue on the origin of ferromagnetism in the field of dilute magnetic semiconductors (DMS) that has stymied researchers for decades. The most puzzling aspect is the observation of magnetic order well below percolation threshold seen in these materials that cannot be explained using the traditional theory of magnetism. In our work we have demonstrated that the proposed defect-induced ferromagnetic coupling (FMC) exhibits the following features; bipartition, synergy and locality and is based on the formation and interaction among spin-polarized neighborhoods analogous to spin-polarized radicals centered at the codopant sites. The FMC is mediated by the molecular orbitals (MOs) of these radicals and is greatly facilitated if the codopant-centered radicals could form bipartite configurations within the host lattices. Within this picture, the origin of magnetism in DMSs and TMOs appears to be the synergy and the interplay between correlated spin-polarization processes that take place in a successive way within neighborhoods centered at the codopants and include their first nearest neighbors (1nn’s). The proposed model can be used as a practical guide for choosing the appropriate pair of codopants for a specific semiconductor environment that can lead to the fabrication of DMSs and TMOs with enhanced magnetic properties.

Our theory provides a unified picture of defect induced magnetism in a diverse set of materials of which DMS forms just one part. The sophistication of the theory allows for predicting specific dopant materials for use in DMS for obtaining materials with enhanced magnetic properties. The paper has been published in Physical Review B.

Informatics Guided Discovery of Surface Structure-Chemistry Relationships in Catalytic Nanoparticles.

We have formulated a data driven discovery strategy based on statistical learning principles and used it to discover new correlations between electronic structure and catalytic activity of surfaces. From the quantitative formulations derived from this informatics based model, a high throughput computational framework for predicting binding energy as a function of surface chemistry and surface coordination that bypasses the need for repeated electronic structure calculations has been developed.

New Visible Light Absorbing Materials for Solar Fuels, Ga(Sbx)N1−x Alloy.

Using first principles methods we predicted large band gap bowing of dilute antimonide alloys of gallium nitride, Ga(Sbx)N1−x (x from 0 to 0.08). The predicted monotonic lattice parameters expansion and reduction of the optical band gap from 3.45 eV to 1.5 eV has subsequently been ex- perimentally confirmed qualitatively as well as quantitatively. The band edge positions for the alloys with compositions up to 8 at% have been shown to straddle the electrochemical potentials of the hydrogen and oxygen evolution reactions confirming this alloy’s potential for use as a photo-catalyst for direct water splitting under visible light. The paper resulting from joint theory-experiment collaboration has been published in the prestigious journal, Advanced Materials.

Informatics aided band gap engineering for solar materials.

We have investigated the applicability of statistics based methods combined with first principles methods to predict band gaps for chalcopyrite materials. The new method accelerates materials discovery process by more than an order of magnitude and has proven to be very useful for the search for new materials for solar energy applications.

Theoretical band edge determination

We have developed a new formalism to predict the band edge positions of ternary and quarternary alloys relative to vacuum. There is no method currently available in the literature that can do this. Our method therefore provides a valuable tool that can be used to judge the usefulness of multicomponent alloys for use in solar energy applications. The band edge positions predicted by this new method for the Ga(Sbx)N1−x alloys have been confirmed experimentally.

Optical Generation and Detection of Polaronic States in PCBM.

PCBM is a fullerene derivative commonly used in organic solar cells as an electron acceptor due its high electron affinity, and relatively strong absorbance in the visible region. Using first principles methods we have predicted the absorption spectra for negatively charged C60 and C70 chains. The experimentally observed transitions for these systems are in agreement with theoretical predictions. This confirms that charge transfer occurs preferentially at the polaronic transition energies in the PCBM, providing a new means for polaronic state spectroscopy.

Tunable Magnetic Properties of Transition-Metal Doped MoS2.

We performed a detailed investigation of the electronic and magnetic properties of the transition- metal (TM) doped two-dimensional (2D) MoS2 using ab initio calculations. The doping is achieved by substituting two or more Mo-atoms by TM-atoms of the 3d-series. Additionally, the effect of codoping on the 2D-MoS2 by cation-cation and cation-anion pairs is also investigated. Our results demonstrated that the TM-doping of 2D-MoS2 leads to a significant reduction of the energy gap and the appearance of magnetic features whose major characteristic is the ferromagnetic coupling of the TM-dopants. The latter is found to be significantly enhanced by codoping as demonstrated by codoping with (Co,Cu), (Ni,Cu), (Mn,Cu) and (Mn,Sb) codopant-pairs.

Collaborators

1. Prof. Antonis Andriotis: Director, Institute of Electronic Structure and Laser, FORTH, Heraklion, Crete, Greece.
2. Prof. George Froudakis: Department of Chemistry, University of Crete, Heraklio, Crete, Greece.
3. Dr. Ernst Richter: Daimler AG FGR/ESS, Wilhelm-Runge-Str. 11, 89081 Ulm, Germany.
4. Prof. Inna Ponomareva: University of South Florida, Tampa, FL.
5. Dr. Deepak Srivastava: NASA Ames, Mountain View, CA.
6. Dr. Michael Sheetz: Center for Computational Sciences, University of Kentucky.
7. Prof. Mahendra Sunkara: Director, Institute for Advanced Materials and Renewable Energy, University of Louisville.
8. Prof. Eva Gonzalez Noya: Universidad Complutense de Madrid, Madrid, Spain.
9. Dr. Sergey Lisenkov: University of South Florida, Tampa, Florida.
10. Prof. Bruce Alphenaar: University of Louisville.
11. Prof. Somnath Datta: University of Louisville. (11) Dr. Jacek Jacinski: University of Louisville.
12. Prof. Krishna Rajan: Iowa State University.
13. Dr. Indira Chaudhuri: University of Louisville.
14. Prof. Doo Young Kim: University of Kentucky.
15. Dr. Steve Lipka: University of Kentucky.

Software:

MedeA

Grants:

Menon, Madhusudan ULRF 11-0817-02 SOLAR: New Materials Search for Solar Energy Conversion to Fuels $237,000 University of Louisville 9/15/2011 -8/31/2015
Menon, Madhusudan KSEF-148-502-14-334 KSEF RDE: Novel approach to the study of a new alloy for energy applications KY Science and Technology Co Inc 7/1/2014 - 6/30/2015 $30,000
Menon, Madhusudan DE-FG02-07-ER46375 DOE EPSCoR: Nanoscale Materials and Architecture for Energy Conversion Department of Energy 7/1/2008 - 7/14/2014 SCOPE
NSF (IIA-1355438) Powering the Kentucky Bioeconomy for a Sustainable Future Awarded NSF (DMS-1125909) SOLAR: New Materials Search for Solar Energy Awarded
DOE Transport Properties of Metal-Organic Nanostructured Interfaces Pending
NSF Use of a predictive approach in the design of new dilute magnetic semiconductors (ready for submission)
NSF EFRI 2-DARE Preliminary Proposal: Chemical Design, Synthesis and Manufacturing of 2-D Materials (ready for submission)
NSF Graphene Based Nanocomposites (ready for submission)
ACS-Petroleum Design novel Nano-materials for efficient CO2 & H2S removal from natural gas (ready for submission)

Publications:

2015

1. M. Akhtar, M. Menon, M. Sunkara, G. Sumanasekera, A. Durygin, and J. B. Jasinski "High-pressure synthesis of rhombohedral α -AgGaO2 via direct solid state reaction", J. Alloys and Compounds 641 87 (2015).
2. A.N. Andriotis and M. Menon "Band gap engineering via doping: A predictive approach", J. Applied Phys. 117 125708 (2015).
3. A.N. Andriotis, Z. Fthenakis, and M. Menon "Successive spin polarizations underlying a new magnetic coupling contribution in diluted magnetic semiconductors", J. Phys: Condens. Matter 27 052202 (2015).

2014

1. A. N. Andriotis and M. Menon, “Tunable Magnetic Properties of Transition-Metal Doped MoS2”, Phys. Rev. B 90 125304 (2014).
2. A.N. Andriotis, G. Mpourmpakis, S. Broderick, K. Rajan, S. Datta, M. Sunkara, and M. Menon "Informatics guided discovery of surface structure-chemistry relationships in catalytic nanoparticles", J. Chem. Phys. 140 094705 (2014).
3. P. Dey, J. Bible, S. Datta, S. Broderick, J. Jasinski, M. Sunkara, M. Menon and K. Rajan "Informatics-Aided Bandgap Engineering for Solar Materials", Computational Materials Science 83 185 (2014).
4. A.N. Andriotis, R.M. Sheetz, E. Richter, and M. Memon "Band alignment and optical absorption in Ga(Sb)N alloys", J. Phys.: Condens. Matter 26 055013 (2014).
5. S. Sunkara, V. KalyanVendra, J. Jasinski, T. Deutsch, A. N. Andriotis, M. Menon and M. Sunkara, “New Visible Light Absorbing Materials for Solar Fuels, Ga(Sbx)N1−x Alloy, Ad- vanced Materials, 2014, (DOI: 10.1002/adma.201305083).

2013

1. H. Shah, A. Carver, K. Fernando, S. Kolli, B. Abeyweera, S. Lisenkov, M. Menon and B. Alphenaar, “Optical Generation and Detection of Polaronic States in PCBM” J. Phys. Chem C, 117, 26538 (2013).
2. D. R. Cummins, H. B. Russell, J. B. Jasinski, M. Menon, and M. K. Sunkara, \Iron Sul de (FeS) Nanotubes Using Sulfurization of Hematite Nanowires", Nano Lett. 13, 2423 (2013).
3. A. N. Andriotis and M. Menon, \Defect-induced magnetism: Codoping and a prescription for enhanced magnetism", Phys. Rev. B 87, 155309 (2013).
4. A. N. Andriotis, G. Mpourmpakis, S. Lisenkov, R. M. Sheetz and M. Menon, \Ucalculation of the LSDA+U functional using the hybrid B3LYP and HSE functionals", Phys. Status Solidi B 250, 356 (2013).

2012

1. A. N. Andriotis and M. Menon, \The synergistic character of the defect-induced magnetism in diluted magnetic semiconductors and related magnetic materials", J. Phys: Condens. Matter 24 455801 (2012).
2. C. Pendyala, J. B. Jasinski, J. H. Kim, V. K. Vendra, S. Lisenkov, M. Menon and M. K. Sunkara, \Nanowires as semi-rigid substrates for growth of thick, InxGa1

2011

1. A. N. Andriotis and M. Menon, \Magnetic coupling in dilute magnetic semiconductors: A new perspective", Phys. Stat. Solidi, B248, 2032 (2011).
2. R. M. Sheetz, E. Richter, A. N. Andriotis, S. Lisenkov, C. Pendyala, M. K. Sunkara and M. Menon, \Visible light absorption and large band gap bowing in dilute alloys of gallium nitride with antimony", Phys. Rev. B84 075304 (2011).
3. A. N. Andriotis, S. Lisenkov and M. Menon, \ Ferromagnetic interactions in hosted bipartite materials - generalized-double-exchange and generalized-superexchange interactions", J. Phys.: Condens. Matter 23 086004 (2011).
4. S. Lisenkov, A. N. Andriotis, R. M. Sheetz and M. Menon, \E ects of co-doping on the ferromagnetic enhancement in ZnO", Phys. Rev. B83, 235203 (2011).

2010

1. A. N. Andriotis, R. M. Sheetz and M. Menon, \LSDA+U approximation: An ecient calculation of the U-values", Phys. Rev. B 81 245103 (2010).
2. S. Lisenkov, A. N. Andriotis and M. Menon, \Magnetic Graphene: A new class of cages formed from graphene sheets and carbon nanotubes ", Phys. Rev. B82 165454 (2010).
3. A. N. Andriotis, Z. G. Fthenakis and M. Menon, \Variation of the surface to bulk contribution to cluster properties`", submitted to VADEMECUM.
4. A. N. Andriotis, R. M. Sheetz and M. Menon, \Defect-induced defect-mediated magnetism in ZnO and carbon-based materials", J. Phys.: Condens. Matter 22 , 334210 (2010)
5. A. N. Andriotis, R. M. Sheetz, E. Richter and M. Menon, \Structural, electronic, magnetic, and transport properties of carbon-fullerene-based polymers", The Oxford Handbook of Nanoscience and Technology, edited by A. V. Narlikar and Y. Y. Fu, Vol. II: Materials, Chapter 21, page 745 (2010).