Research

        

Mobility

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BSO Device

 

 

 

 

 

 

 

 

BaSnO3-EDLT_Jalan

 

 

 

 

NTO-broken gap-Jalan
predict_1

 

 

 

 

 

 

 

 

 

 

 

 

 

Radical-based oxide MBE-Jalan

High-Mobility Perovskite Oxides with Ultra Wide Bandgap

In this project, we are developing thin films and heterostructures of high-mobility perovskite oxides based on the recent discovery of high room-temperature mobility in bulk alkaline-earth stannate crystals. Through a combination of experimental and computational techniques, the project seeks to investigate fundamental factors that influence the defect formation and electronic properties in strain-engineered alkaline-earth stannate (Sr1-xBaxSnO3) thin films. We seek to understand, and control defects specifically dislocations, local structure, and electronic mobility in these materials with an ultimate goal to create a new class of high-mobility semiconducting materials with wide bandgap for room-temperature applications. The project is also exploiting novel synthesis methods for atomic level control of point defects and structural defects in complex oxides. 

Recent Selected Publications:

A. Prakash and B. Jalan, “Wide Bandgap Perovskite Oxides with High Room-Temperature Electron Mobility”, Adv. Mater. Interfaces (2019) (Invited progress report) (in press)

A. Prakash, N. F. Quackenbush, H. Yun, J. Held, T. Wang, T. Truttmann, J. M. Ablett, C. Weiland, T-L.  Lee, J. C. Woicik, KA. Mkhoyan and B. Jalan, “Separating electrons and donors in BaSnO3 via band engineering” https://arxiv.org/abs/1905.04563 (under review) (2019)

W. Nunn, A. Prakash, A. Bhowmik, R. Haislmaier, J. Yue, J. M. Garcia Lastra, and B. Jalan, “Frequency- and temperature-dependent dielectric response in hybrid molecular beam epitaxy-grown BaSnO3 films” APL Mater. 6, 066107 (2018)

T. Wang, A. Prakash, Y. Dong, T. Truttmann, A. Bucsek, R. James, D. D. Fong, J.-W. Kim, P. J. Ryan, H. Zhou, T. Birol, and B. Jalan, “Strain-Engineered Phases of SrSnO3 with 300% Mobility Enhancement at Room Temperature” ACS Appl. Mater. Interfaces 10, 21061 (2018)

A. Prakash, P. Xu, X. Wu, G. Haugstad, X. Wang, and B. Jalan "Adsorption-Controlled Growth and the Influence of Stoichiometry on Electronic Transport of Hybrid Molecular Beam Epitaxy-Grown BaSnO3 Films" J. Mater. Chem. C 5, 5730 (2017) (Emerging Investigator invited article)

A. Prakash, P. Xu, A. Faghaninia, S. Shukla, J. W. Ager, C. S. Lo, and B. Jalan “Wide Band-gap Oxide with Room Temperature Conductivity Exceeding 104S/cm”, Nat. Commun. 8, 15167 (2017)

Perovskite-based Power Electronics 

Perovskite-based alkaline-earth stannates possess wide-to-ultra wide bandgaps that make them highly suitable candidate for transparent conductors, power electronic devices, and high electron mobility transistors. Additionally, perovskite structure brings with them exceptional flexibility with regards to composition tuning and structural compatibility. Despite much of the promise on the stannate perovskite growth and devices, there are numerous fundamental questions that need to be addressed before this technology can reach its full potential. In this project, we are developing materials and novel device architectures utilizing high mobility stannates for room-temperature oxide electronics. These materials are grown using radical-based MBE approach and characterized, in particular, for material properties that are strongly coupled to device performance. This is a joint project with Prof. Steven Koester, Electrical Engineering at the University of Minnesota.  

Recent Selected Publications:

L. R. Thoutam, J. Yue, A. Prakash, T. Wang, K. E. Elangovan, and B. Jalan, “Electrostatic control of insulator–metal transition in La-doped SrSnO3 films” ACS Appl. Mater. Interfaces11 (8), 7666 (2019) 

V. R. S. K. Chaganti, A. Prakash, J. Yue, B. Jalan, and S. J. Koester, “Demonstration of a depletion-mode SrSnO3 n-channel MESFET” IEEE Elec. Dev. Lett.39, 1381 (2018)

J. Yue, A. Prakash, M. C. Robbins, S. J. Koester, and B. Jalan, “Depletion Mode MOSFET using La-doped BaSnO3 as a Channel Material” ACS Appl. Mater. and Interfaces10, 21061 (2018)

Electrostatic and Electrochemical Control of Properties 
 
The ability to control materials properties via external stimuli is a powerful approach to investigate materials for their potential applications. In this project, we are using ion-gel and ionic liquid gating in addition to the convectional gate dielectrics to not only control the electronic and magnetic properties of complex oxides but also to discover completely novel ground states. In particular, we seek to separate disorder and electronic contribution to the conductivity with the ultimate goal to understand and then exploit disorder in determining electronic and dielectric properties of materials. This project utilizes the state-of-the-art MBE approach for materials synthesis, structural and electronic characterizations available both at the University of Minnesota and in the national laboratory network. 

Recent Selected Publications:

L. R. Thoutam, J. Yue, A. Prakash, T. Wang, K. E. Elangovan, and B. Jalan, “Electrostatic control of insulator–metal transition in La-doped SrSnO3 films” ACS Appl. Mater. Interfaces11 (8), 7666 (2019) 

Strongly Correlated Phenomena, and Superconductivity in Complex Oxides 

Complex oxides with perovskite structure (ABO3) are known due to their impressive multi-functionality, encompassing high temperature superconductivity; colossal magnetoresistance; multiferroicity; and strongly-correlated electron behavior. These phenomena have extreme sensitivity to composition, which offers the opportunity to design novel devices (such as Mott field effect transistors) with additional means to control functionality. Heterostructures formed from these materials also display interface-stabilized ground states (such as two-dimensional electron gases (2DEGs), 2D superconductivity, and novel magnetism) that do not exist in the bulk constituents. In this project, we seek to investigate role of disorder and doping on superconductivity in select perovskite oxide thin films and related heterostructures including the study of unusual magnetic ground states, and strongly-correlated Mott-Hubbard-type insulator characteristics in rare-earth titanates. With the particular emphasis on synthesis with excellent control over stoichiometry, dimensionality and strain, we seek to understand, and control the interplay between lattice, charge and spin degree of freedom and their coupling to the functionality such as exotic magnetism, and superconductivity in “built-to-order” quantum structures.

Recent Selected Publications:

L. Thoutam, J. Yue, P. Xu and B. Jalan, “Hopping transport in SrTiO3/NdTiO3-x/SrTiO3 heterostructures” Phys. Rev. Mater. 3, 065006 (2019).

X. Cai, Y. Ayino, J. Yue, P. Xu, B. Jalan and VS. Pribaig, “Disentangling spin-orbit coupling and local magnetism in a quasi-2D electron system” https://arxiv.org/abs/1904.00295(under review)

S.A. Chambers, Y. Du, Z. Zhu, J. Wang, M. J. Wahila, L. F. J. Piper, A. Prakash, J. Yue, B. Jalan, S. R. Spurgeon, D. M. Kepaptsoglou, Q. M. Ramasse, P. V. Sushko, “Interconversion of intrinsic defects in SrTiO3 (001)” Phys. Rev. B.97, 245204 (2018)

P. Xu, Y. Ayino, C. Cheng, V. Pribiag, R. Comes, P. V. Sushko, S. Chambers, and B. Jalan* “Predictive control over charge density in the two-dimensional electron gas at the polar/non-polar NdTiO3/SrTiOinterface”, Phys. Rev. Lett.117, 106803 (2016). 

P. Xu, T. C. Droubay, J. S. Jeong, K. A. Mkhoyan, P. V. Sushko, S. A. Chambers, B. Jalan, “Quasi two-dimensional ultra-high carrier density in a complex oxide broken-gap heterojunction”, Adv. Mater. Interfaces3, 1500432 (2016).

P. Xu, D. Phelan, J. S. Jeong, K. A. Mkhoyan, and B. Jalan, “Stoichiometry-driven metal-to-insulator transition in NdTiO3/SrTiOheterostructures”, Appl. Phys. Lett.104, 082109 (2014).

Development of Radical-based Approaches for Novel Ferroelectric Oxides 

The innovation in materials drives the future technologies and discovery. In this project, through a combination of experimental and theoretical/computational techniques, we seek identify the fundamental factors at the atomic and electronic levels, which are responsible for determining crystal growth of metal oxides of a stubborn metal in ultra high vacuum via select perovskite films, and layered Ruddlesden-Popper (RP) phases. Our objectives are two-fold: (i) to develop low-energy, radical-based MBE, and novel chemical beam epitaxy (CBE) approaches for single-crystalline films of metal perovskite oxides of stubborn metal with particular emphasis on the study of growth kinetics for the synthesis of “built-to-order” structures those are thermodynamically unstable in their bulk form; (ii) to exploit the these structures to investigate growth kinetics – defect – structure – electroactive response relationships. 

Recent Publications:

T. Wang, A. Prakash, E. Warner, W. L. Gladfelter, and B. Jalan, “Molecular beam epitaxy growth of SnO2 using a tin chemical precursor”, J. Vac. Sci. Technol. A 33, 020606 (2015).

Waste heat to Energy Conversion

The discovery of new methods of generating energy without adversely affecting the environment is a compelling scientific problem of our time. This project, in close collaboration with Prof. Richards James of Aerospace Engineering and Mechanics (AEM), UMN seeks to develop new materials and devices for the direct conversion of heat to electricity. Here, “direct” means that electricity is generated by the material itself, without the need of a separate electrical generator. We employ phase change material having an abrupt change of polarization at the transformation. One major focus of this project is to gain a fundamental understanding of the first order phase transition and the origin of thermal hysteresis in hard materials. Guided by the mathematical design of materials (led by James’s group), we employ state-of-the-art hybrid MBE approach to synthesize them and control their properties using strain engineering, alloying, and electrical control. 

Recent Publications:

A. Bucsek, W. Nunn, M. Verdugo, B. Jalan and R. D. James, “Ferroelectric energy conversion using first-order phase transformations”, (2019) Phys. Rev. Appl. (accepted) 2019