Research

Focus: Programmable 2D materials and van der Waals crystals.

Motivation: 2D materials, and more specifically transition metal dichalcogenides, are stable as single isolated layers of matter – just one layer of metal sandwiched between S, Se, or Te on either side. They possess unique electronic properties and can be assembled into van der Waals crystals where the interlayer interaction is weak. We aim to control the composition and structure within the individual layers to deterministically adjust their electronic (and maybe magnetic) structure – and then add the next layer. The use of 2D materials is broad – conventional transistors, and quantum materials, catalysis, and optical emitter. There are many more ideas but their realization hinges on finding new ways to make materials with superb nanoscale control of geometric and electronic structure, which is particularly challenging for the van der Waals crystals, but critical to their use.  

Target: This project is currently a mosaic of projects which target challenges recognized as critical bottlenecks in TMD’s use as electronic and quantum materials. These challenges include understanding of growth mechanisms at the atomic scale, which will lead to higher quality material, find new routes to functionalization for sensing and catalysis, develop new functionalities by twisting, rippling, and doping the TMD layers. 

Project Details: In our group we use scanning tunneling microscopy and spectroscopy (STM/STS) and other surface science techniques to probe the geometric and electronic structure for single layers and van der Waals crystals. This is the basis for device development and to encode the growth parameters for rapid materials discovery. For an example of our work on 2D materials: Monazami, E., Bignardi, L., Rudolf, P., & Reinke, P. (2015). Strain lattice imprinting in graphene by C60 intercalation at the graphene/Cu interface. Nano letters, 15(11), 7421-7430, and Volders, C., Monazami, E., Ramalingam, G., & Reinke, P. (2017). Alternative route to silicene synthesis via surface reconstruction on h-MoSi2 crystallites. Nano letters, 17(1), 299-307

This project includes collaborations with PennState University, and Prof. McDonnell’s research group at UVa to synthesize materials with new elements. Our main collaboration is Prof. Balachandran’s research group who brings expertise in machine learning,  and electronic structure theory to the table, and helps us link all the different aspects of TMD materials. These collaborations are critical to make new, and better materials and devices. 

Focus: Control oxide performance by understanding the atomic scale processes.

Motivation: Dry and aqueous corrosion of technical alloys comes at a high cost to the economy, and incurs substantial risk, and limits longevity of materials. This problem extends from the large bridge structure to the ship in saltwater, to the nanoscale interconnects in computer chips. Our work addresses the initial reaction steps of binary and ternary alloys as they transform from a pristine metallic surface to an oxide, or nitride layer. We currently study Ni-based superalloys including NiCrW and NiCrMo, which are coveted for their high corrosion resistance in aggressive media. 

Target: The project investigates surface chemical reactions, oxide nucleation and growth to unravel the critical steps and synergies on the alloy surface. This will lead us ultimately to predict and control corrosion resistance either by alloy design or surface engineering. This work was started several year ago in the framework of award by the Office of Naval Research. 

Project Details: In the next few years we will include other alloys of technical relevance in our work such as FeNiCr, and possibly Cu and Cu-alloys. This project will be focused on dry oxidation (reaction with O2) and gas phase water, and nitrogen to mimic reactants found in the environment and understand how they act synergistically to form and react with the protective oxide or nitride layer. We study these reactions with in-situ experiments using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS), and an example can be found in a recent student publication: Blades, W. H., & Reinke, P. From alloy to oxide: capturing the early stages of oxidation on Ni–Cr (100) alloys. ACS applied materials & interfaces, 10(49), 43219-43229. The nanoscale resolution of STM is complement by the time and exposure (T, p(O2)) resolved operando characterization of the oxidation using X-ray photoelectron spectroscopy (XPS), or X-ray photoelectron emission microscopy (XPEEM) at synchrotron beamlines such as Brookhaven National Laboratory or the Advanced Light Source. Analysis of complex data sets is part of this work, and instrumental to interface with theoreticians. 

Focus: Predict where pitting will occur in a protective oxide (this has eluded scientists and engineers for many decades...). 

Motivation: Dry and aqueous corrosion of technical alloys comes at a high cost to the economy, and incurs substantial risk, and limits longevity of materials. This problem extends from the large bridge structure to the ship in saltwater, to the nanoscale interconnects in computer chips. Our work addresses the initial reaction steps of binary and ternary alloys as they transform from a pristine metallic surface to an oxide, or nitride layer. We currently study Ni-based superalloys including NiCrW and NiCrMo, which are coveted for their high corrosion resistance in aggressive media. 

Target: The project targets aqueous corrosion, and will focus on the role of chloride in the initiation of pitting events in protective oxides, and is of high technological relevance for any alloy used in or close to seawater. Generalized models will help to generalize the our understanding of protective layer stability in aggressive media. This will lead us ultimately to predict and control corrosion resistance either by alloy design or surface engineering.

Project Details: This project will integrate surface science experimentation, model system studies, and electrochemical corrosion studies, and is currently being developed in collaboration with Prof. Scully’s research group. This work was started several year ago in the framework of award by the Office of Naval Research and a recent publication can be found here: Gusieva, K., Cwalina, K. L., Blades, W. H., Ramalingam, G., Perepezko, J. H., Reinke, P., & Scully, J. R. (2018). Repassivation behavior of individual grain facets on dilute Ni–Cr and Ni–Cr–Mo alloys in acidified chloride solution. The Journal of Physical Chemistry C, 122(34), 19499-19513. The methods used include STM/STS, and XPS and related techniques, atomic force microscopy (some of the work might be at Oak Ridge National Laboratory), and electrochemical techniques to study corrosion. We will also develop specific model experiments which target the Cl interaction with oxide surfaces, and build an UHV compatible chloride source. This project will require to cross-correlate a wide range of data and data analysis methods with experimental work.