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Search Publications by: Nikolai Zhitenev (Fed)

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Displaying 1 - 25 of 54

Spatially Resolved Potential and Li-Ion Distributions Reveal Performance-Limiting Regions in Solid-State Batteries

October 19, 2021
Elliot Fuller, Evgheni Strelcov, Jamie Weaver, Michael Swift, Joshua Sugar, Andrei Kolmakov, Nikolai Zhitenev, Jabez J. McClelland, Yue Qi, Joseph Dura, Alec Talin
The performance of solid-state electrochemical systems is intimately tied to the potential and lithium distributions across electrolyte–electrode junctions that give rise to interface impedance. Here, we combine two operando methods, Kelvin probe force

Edge channels of broken-symmetry quantum Hall states in graphene visualized by atomic force microscopy

May 14, 2021
Joseph A. Stroscio, Sungmin Kim, Johannes Schwenk, Daniel T. Walkup, Yihang Zeng, Fereshte Ghahari, Son T. Le, Marlou R. Slot, Julian Berwanger, Steven R. Blankenship, Kenji Watanabe, Takashi Taniguchi, Franz Giessibl, Nikolai Zhitenev, Cory Dean
The quantum Hall (QH) effect, a topologically non-trivial quantum phase, expanded and brought into focus the concept of topological order in physics. The topologically protected quantum Hall edge states are of crucial importance to the QH effect but have

Tuning single-electron charging and interactions between compressible Landau level islands in graphene

January 29, 2020
Daniel T. Walkup, Fereshte Ghahari Kermani, Christopher Guti?rrez, Kenji Watanabe, Takashi Taniguchi, Nikolai B. Zhitenev, Joseph A. Stroscio
Interacting quantum dots (QDs), small chunks of matter with well-separated energies of electronic levels, have been extensively exploited in condensed matter physics and quantum information science. Using a low-temperature scanning tunneling microscope

Nanoscale mapping of the double layer potential at the graphene-electrolyte interface

January 28, 2020
Evgheni Strelcov, Christopher M. Arble, Hongxuan Guo, Brian D. Hoskins, Alexander Yulaev, Ivan Vlassiouk, Nikolai B. Zhitenev, Alexander Tselev, Andrei A. Kolmakov
The structure and potential drop across the electrical double layer (EDL) govern the operation of multiple electrochemical devices, determine reaction potentials and condition ion transport through the cellular membranes in living organisms. Despite more

Unveiling defect-mediated charge-carrier recombination at the nanometer scale in polycrystalline solar cells

November 20, 2019
Yohan Yoon, Wei-Chang Yang, Dongheon Ha, Paul M. Haney, Daniel Hirsch, Heayoung Yoon, Renu Sharma, Nikolai Zhitenev
In this work, we employ two techniques, near-field scanning photocurrent microscopy (NSPM) and transmission electron microscope based cathodoluminescence spectroscopy (TEM-CL), to analyze the nanoscale electrical and optical properties of CdTe solar cells

Streaming Batch Eigenupdates for Hardware Neural Networks

August 6, 2019
Brian D. Hoskins, Matthew W. Daniels, Siyuan Huang, Advait Madhavan, Gina C. Adam, Nikolai B. Zhitenev, Jabez J. McClelland, Mark D. Stiles
Neuromorphic networks based on nanodevices, such as metal oxide memristors, phase change memories, and flash memory cells, have generated considerable interest for their increased energy efficiency and density in comparison to graphics processing units

Direct-write Lithiation of Silicon Using a Focused Ion Beam of Li+

July 8, 2019
William R. McGehee, Evgheni Strelcov, Vladimir P. Oleshko, Christopher L. Soles, Nikolai B. Zhitenev, Jabez J. McClelland
Electrochemical processes that govern the performance of lithium ion batteries involve numerous parallel reactions and interfacial phenomena that complicate the microscopic understanding of these systems. As a new way to study the behavior of ion transport

Interaction-driven quantum Hall wedding cake-like structures in graphene quantum dots

August 24, 2018
Christopher Gutierrez, Daniel T. Walkup, Fereshte Ghahari Kermani, Cyprian Lewandowski, Joaquin R. Nieva, Kenji Watanabe, Takashi Taniguchi, Leonid Levitov, Nikolai Zhitenev, Joseph A. Stroscio
Interactions amongst relativistic particles underpin exotic behaviours in diverse systems ranging from quark-gluon plasmas to Dirac electron fluids in solids. Despite long-standing interest, direct observation of quantum-relativistic matter under ambient

Improving dielectric nanoresonator array coatings for solar cells

June 19, 2018
Dongheon Ha, Nikolai B. Zhitenev
We introduce single layer silicon dioxide (SiO2) nanosphere arrays as antireflection coatings (ARCs) on a gallium arsenide (GaAs) solar cell. We make macro- and nanoscale experiments and finite-difference time-domain (FDTD) calculations to prove the

Nanoscale photocurrent mapping in perovskite solar cells

June 1, 2018
Yohan Yoon, Dongheon Ha, Ik Jae Park, Paul M. Haney, Sangwook Lee, Nikolai Zhitenev
In this work, we study spatially-resolved generation of photocurrent of methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells to reveal the microscopic effects of annealing temperature and degradation under light exposure. Correlating a novel

Paper in electronic and optoelectronic devices

March 6, 2018
Dongheon Ha, Zhiqiang Fang, Nikolai B. Zhitenev
The demand for lightweight, cost-effective, and/or flexible electronic and optoelectronic devices drives research toward new materials advancing the desired functionality or reducing manufacturing costs. Paper, being in addition an earth abundant and

Stateful characterization of resistive switching TiO2 with electron beam induced currents

December 7, 2017
Brian D. Hoskins, Gina C. Adam, Evgheni Strelcov, Nikolai B. Zhitenev, Andrei A. Kolmakov, Dmitri B. Strukov, Jabez J. McClelland
Metal oxide resistive switches have become increasingly important as possible artificial synapses in next generation neuromorphic networks. Nevertheless, there is still no codified set of tools for studying fundamental properties of the devices. To this

Local measurements of photocurrent and band gap in CdTe solar cells

September 25, 2017
Yohan Yoon, Jungseok Chae, Aaron M. Katzenmeyer, Heayoung Yoon, Joshua D. Schumacher, Sang M. An, Andrea Centrone, Nikolai B. Zhitenev
Polycrystalline thin film technology has shown great promise for low cost, high efficiency photovoltaics. To further increase the power efficiency, a firm understanding of microstructural properties of the devices is required. In this work, we investigate

Strain engineering a 4a*?3a charge-density-wave phase in transition-metal dichalcogenide 1T-VSe2

July 19, 2017
Duming Zhang, Jeonghoon Ha, Hongwoo H. Baek, Yang-Hao Chan, Donat F. Natterer, Alline Myers, Joshua D. Schumacher, William Cullen, Albert Davydov, Young Kuk, Mei-Yin Chou, Nikolai Zhitenev, Joseph A. Stroscio
We report a new charge density wave (CDW) structure in strained 1T-VSe2 thin films synthesized by molecular beam epitaxy. The CDW structure is unconventional and exhibits a rectangular 4a×√3a periodicity, as opposed to the previously reported hexagonal 4a

An On/Off Berry Phase Switching with Circular Graphene Resonators

May 26, 2017
Fereshte Ghahari Kermani, Daniel T. Walkup, Christopher Gutierrez, Joaquin R. Nieva, Yue Y. Zhao, Jonathan E. Wyrick, Donat F. Natterer, William G. Cullen, Kenji Watanabe, Takashi Taniguchi, Leonid Levitov, Nikolai B. Zhitenev, Joseph A. Stroscio
Berry phase is an example of anholonomy, where the phase of a quantum state may not return to its original value after its parameters cycle around a closed path; instead the quantum system’s wavefunction may acquire a real measurable phase difference

Nanoscale Imaging and Spectroscopy of Band Gap and defects in Polycrystalline Photovoltaic Devices

April 12, 2017
Yohan Yoon, Jungseok Chae, Aaron M. Katzenmeyer, Heayoung Yoon, Joshua D. Schumacher, Sang M. An, Andrea Centrone, Nikolai B. Zhitenev
Improving the power conversion efficiency of photovoltaic (PV) devices is challenging because the generation, separation and collection of electron-hole pairs in PV devices is strongly dependent on details of the nanoscale chemical composition and defects

Depletion region surface effects in electron beam induced current measurements

September 7, 2016
Paul M. Haney, Heayoung Yoon, Benoit H. Gaury, Nikolai B. Zhitenev
Electron beam induced current (EBIC) is a powerful characterization technique which offers the high spatial resolution needed to study polycrystalline solar cells. Ideally, an EBIC measurement reflects the spatially resolved quantum efficiency of the

Scanning tunneling spectroscopy of proximity superconductivity in epitaxial multilayer graphene

January 7, 2016
Donat F. Natterer, Jeonghoon Ha, Hongwoo H. Baek, Duming Zhang, William G. Cullen, Nikolai B. Zhitenev, Young Kuk, Joseph A. Stroscio
Superconducting aluminum films were grown on multilayer graphene. The aluminum films were discontinuous with networks of trenches in the film morphology reaching down to the substrate to exposed graphene terraces. Superconductivity was induced in

Local photocarrier dynamics in CdTe solar cells under optical and electron beam excitations

December 16, 2015
Heayoung Yoon, Paul M. Haney, Yohan Yoon, Sang M. An, James I. Basham, Nikolai Zhitenev
We investigate local carrier dynamics in n-CdS / p-CdTe solar cells, where the electron-hole pairs are generated by either near-field optical illumination or highly focused electron beam excitation. A focused ion milling process was used to prepare a

Creating Nanostructured Superconductors by Local Current Annealing

September 17, 2015
Hongwoo H. Baek, Jeonghoon Ha, Duming Zhang, Bharath NMN Natarajan, Jonathan P. Winterstein, Renu Sharma, Rongwei Hu, Kefeng Wang, Steven Ziemak, Johnpierre Paglione, Young Kuk, Nikolai B. Zhitenev, Joseph A. Stroscio
Superconductivity results from a Bose condensate of Cooper-paired electrons with a macroscopic quantum wavefunction. Dramatic effects can occur when the region of the condensate is shaped and confined to the nanometer scale. Recent progress in