Laboratory for Surface Modification (LSM)

Seminars Archives

January 2018 | February 2018 | March 2018

Thursday, February 01, 2018
Ferrate heterostructures: From metal-insulator transitions to ionic functionality
Steve May
Department of Materials Science and Engineering
Drexel University
12:00 Noon CHEM 260

Complex oxide heterostructures continue to generate significant interest both as a platform for exploring new fundamental materials physics and for their potential in new electronic devices. The ferrates, such as CaFeO3-d and SrFeO3-d, host many of the novel properties found in correlated oxides including coupled structural and electronic phase transitions, helical magnetism, and negative charge transfer physics. This talk will highlight recent activities within my group focused on using epitaxial ferrate films to gain insights into electronic behavior and to induce new means to control functionality in these materials. First, I will describe how the electronic structure of CaFeO¬3 is altered across its metal-insulator, using X-ray spectroscopies to distinguish the response on both iron and oxygen sites.[1] Second, the central role of the nominal Fe valence state on the electronic and optical properties will be presented, with both oxygen deficiency and cation composition shown to effectively tailor behavior in La1-xSrxFeO3-d films.[2,3] I’ll conclude by highlighting the promise of ferrates for use in three-terminal non-volatile devices in which the channel resistivity is controlled through electric-field induced oxidation/reduction.[4]

[1] P. C. Rogge, R. U. Chandrasena, A. Cammarata, R. J. Green, P. Shafer, B. M. Lefler, A. Huon, A. Arab, E. Arenholz, H. N. Lee, T.-L. Lee, S. Nemšák, J. M. Rondinelli, A. X. Gray, and S. J. May, “The electronic structure of negative charge transfer CaFeO3 across the metal-insulator transition”, submitted to Physical Review Materials.

[2] Y. J. Xie, M. D. Scafetta, E. J. Moon, A. L. Krick, R. J. Sichel-Tissot, S. J. May, Applied Physics Letters 105, 062110 (2014).

[3] S. Y. Smolin, M. D. Scafetta, A. K. Choquette, M. Y. Sfeir, J. B. Baxter, and S. J. May, Chemistry of Materials 28, 97 (2016).

[4] A. L. Krick and S. J. May, APL Materials 5, 042504 (2017).
Thursday, February 08, 2018
Programmable Nano-Systems: Form Designed Architectures to Controllable Processes
Oleg Gang
Columbia University
Chemical Engineering and Applied Physics and Applied Mathematics
12:00 Noon CHEM 360

Our ability to organize diverse type of nanoscale objects into the desired organizations is often a
limiting factor in creating targeted nanomaterial. DNA provides powerful means for interaction
encoding, and much progress was achieved recently in ability to tailor DNA structures. However,
it is challenging to prescribe the architecture or behavior of the entire nanoscale system as well as
translate the advances of DNA assembly into material design. Our research explores novel
concepts for creating targeted static and dynamic nano-architectures by bridging DNA-encoded
nano-objects with structural plasticity and programmability of DNA macromolecular structures.
Through establishing assembly approaches and revealing the phenomena that govern systems with
DNA-encoded interactions, we develop methods for fabrication of well-defined three-dimensional
lattices, two-dimensional membranes and finite-sized clusters from the multiple types of the nanocomponents.
Our recent progress demonstrates strategy for organizing such nano-components as
nanoparticles and proteins into ordered 3D arrays with engineered crystallographic symmetries,
and clusters with prescribed architectures. These methods are also used to control a system
dynamic behavior: structural transformations, specific triggering of desired configurations and
molecular amplification. The applications of the DNA-based assembly platform for creation of
optical and biomedical materials will be also discussed.
Thursday, February 15, 2018
Nanoscale Transducers for Photonic Quantum Information Science and Metrology
Kartik Srinivasan
Center for Nanoscale Science and Technology
National Institute of Standards and Technology
12:00 Noon CHEM 260

Advances in nanofabrication technology have enabled the development of chip-scale geometries that control the propagation and confinement of light at the wavelength-scale. Taken together with complementary advances in areas such as nanomechanics, there is great opportunity to create systems in which light-matter interactions are dramatically enhanced in comparison to bulk materials. In this talk, I will present an overview of a number of chip-scale signal transducers, based on the engineering of optomechanical, nonlinear optical, and dipole interactions in nanoscale geometries. The systems I will describe include a piezo-optomechanical circuit platform for realizing a coherent link between the RF and optical domains through acoustics, and silicon nitride optomechanical cavities used in Brownian motion thermometry calibrated by quantum noise. The nonlinear optical Kerr effect is used to establish classical and quantum coherent links across the optical spectrum, through the creation of octave-spanning microresonator frequency combs, quantum light sources spanning the visible and telecommunications bands, and quantum frequency converters for efficient and low-noise transduction of quantum states. Finally, I will discuss how we can use heterogeneous integration to introduce single quantum emitters based on InAs/GaAs quantum dots into this Kerr nonlinear platform.
Thursday, February 15, 2018
A New Approach to Magnetic Resonance at Heterointerfaces: Spin Dependent Charge Pumping in 4H-SiC MOSFETs
Patrick M. Lenahan
Pennsylvania State University
10:00am NPL 201

Although 4H SiC MOSFETs have great promise in high power and high temperature applications, their great promise is limited by the presence of a defective silicon carbide-silicon dioxide interface region. We have utilized a new electron paramagnetic resonance (EPR) apprach to explore the defect structure at these SiC- oxide interfaces in fully processed transistors: multi-field and RF frequency spin dependent charge pumping.

Conventional electron paramagnetic resonance (EPR) offers unrivalled analytical power for the identification of point defects in semiconductors and insulators. Unfortunately, the sensitivity of conventional EPR measurements is, at best, about ten billion total defects. This sensitivity is inadequate for measurements in most devices of technological significance. A second limitation of conventional EPR in device physics studies is that it is sensitive to all paramagnetic defects within structure under study. EPR detection via electrically detected magnetic resonance (EDMR) can overcome both of these limitations. It provides a sensitivity typically at least ten million times higher than that of conventional EPR and is also exclusively sensitive to defect centers which impact the electronic behavior of the devices.

EDMR studies nearly always utilize spin dependent recombination (SDR). SDR is quite sensitive to deep level defects but, in studies of heterointerfaces such as the SiC/SiO2 boundary, defects throughout the entire interface bandgap can be important. In this study, we utilize a new EDMR apprach to invesitgate the silicon carbide-silicon dioxide interface: multi-magentic field and RF frequency spin dependant charge pumping (SDCP).

SDCP allows quite sensitive EDMR measurements of interface defects with levels throughout nearly the entire interface bandgap. The SDCP sensitivity is very nearly magnetic field and frequency independent and is typically more sensitive than SDR. The enhanced sensitivity as well as the field and frequency independence alows us to make measurements at resonance frequencies as high as 16 GHz and as low as 85 MHz. The multi-field and frequency measurements yield information about the relative contributions of hyperfine and spin orbit interactions and thereby aid in defect identification. In this presentation I will briefly review the physics involved in SDCP and discuss the defects which we observe via SDCP. In addition, I will briefly outline the close connection between low frequency SDCP and a near zero field non- resonant response in charge pumping currents. The near zero field response may one day provide a remarkably simple tool for the study of interface defect structure.
Thursday, February 22, 2018
Controlling Electronic Structure and Correlations in Artificial Quantum Materials
Kyle Shen
Physics Department
Cornell University
12:00 Noon CHEM 260

Our ability to control the electronic structure of materials, for instance at semiconductor interfaces, has had enormous scientific and technological implications. Recently, this concept has been extended to materials which possess inherently strong quantum many-body interactions, such as strongly correlated transition metal oxides, allowing us to synthesize artificial heterostructures which can harbor novel electronic or magnetic properties. The ability to deterministically manipulate the strength of electron correlations or the electronic band structure will be critical to designing new materials with novel properties. I will describe some examples of our recent work in thin films of the odd-parity superconductor Sr2RuO4 where we have used both epitaxial strain to control the strength of electronic correlations, the electronic band structure, and the Fermi surface topology. These new insights could someday enable new approaches towards the control over the emergent properties of quantum materials.
Tuesday, February 27, 2018
Thirty-Second Annual Symposium of the LSM and IAMDN
Life Sciences Building
8:30 - 5:00pm


Thirty-Second Annual LSM/IAMDN Symposium

Tuesday, February 27, 2018
8:30 a.m. to 5:00 p.m.
Life Sciences Center
Busch Campus

The Laboratory for Surface Modification (LSM) and the Institute for Advanced Materials, De-vices and Nanotechnology (IAMDN) will host the Thirty-Second Annual LSM/IAMDN Sympo-sium on Tuesday, February 27, 2018. The symposium will focus on experimental and theoretical studies of surfaces, interfaces, thin films and their applications, as well as nanoscale phenomena. We will include both oral and poster presentations; contributed talks will be 15 minutes long (in-cluding a short discussion).

The program will include two "Highlight Presentations", this year given by two prominent invited speakers:

Dr. Ivan Božović, Brookhaven National Laboratory, his talk is titled: “The Exciting New Interface Physics”

Professor Robert Wallace, University of Texas at Dallas, his talk is titled: “2D Materials: Surfaces, Interfaces and Defects”

This meeting is an excellent opportunity for graduate students and postdocs to present their work in a friendly atmosphere. Of course, faculty members are welcome to speak as well. We also en-courage participants from other universities to attend and present their work.

We will award two prizes for best student presentations. For the best oral presentation, the
Theodore E. Madey Prize will be awarded, while the Leszek Wielunski Prize is to be given for the best poster presentation. The prize will be awarded to the first author listed for the presenta-tion. Only student presenters are eligible to compete.

The draft program is available on the LSM website

You may also view a summary of past and upcoming seminars.