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Search Publications by: Nikolai Zhitenev (Fed)

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Displaying 26 - 50 of 57

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

December 16, 2015
Author(s)
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
Author(s)
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

Electron beam induced current in the high injection regime

July 2, 2015
Author(s)
Paul M. Haney, Heayoung Yoon, Prakash Koirala, Robert W. Collins, Nikolai B. Zhitenev
Electron beam induced current (EBIC) is a powerful technique which measures the charge collection efficiency of photovoltaics with sub-micron spatial resolution. The exciting electron beam results in a high generation rate density of electron-hole pairs

Strong asymmetric charge carrier dependence in inelastic electron tunneling spectroscopy of graphene phonons

June 16, 2015
Author(s)
Donat F. Natterer, Yue Y. Zhao, Jonathan E. Wyrick, Yang-Hao Chan, Wen-Ying Ruan, Mei-Yin Chou, Kenji Watanabe, Takashi Taniguchi, Nikolai B. Zhitenev, Joseph A. Stroscio
The observation of phonons in graphene by inelastic electron tunneling spectroscopy has been met with limited success in previous measurements arising from weak signals and other spectral features which inhibit a clear distinction between phonons and

Creating and Probing Electron Whispering-Gallery Modes in Graphene

May 8, 2015
Author(s)
Yue Y. Zhao, Jonathan E. Wyrick, Donat F. Natterer, Joaquin R. Nieva, Cyprian Lewandowski, Kenji Watanabe, Takashi Taniguchi, Leonid Levitov, Nikolai B. Zhitenev, Joseph A. Stroscio
Designing high-finesse resonant cavities for electronic waves is hampered by the short coherence lengths in solids. Previous approaches, e.g. the seminal nanometer-sized quantum corrals, depend on careful positioning of adatoms at clean surfaces. Here we

Nanoscale Imaging of Photocurrent and Efficiency in CdTe Solar Cells

October 15, 2014
Author(s)
Leite Marina, maxim abashin, Henri Lezec, anthony gianfrancesco, Alec Talin, Nikolai Zhitenev
The local collection characteristics of grain interiors and grain boundaries in thin film CdTe polycrystalline solar cells are investigated using scanning photocurrent microscopy. The carriers are locally generated by light injected through a small

Pseudomagnetic Fields in a Locally Strained Graphene Drumhead

August 25, 2014
Author(s)
Shuze Zhu, Yinjun Huang, Nikolai Klimov, David B. Newell, Nikolai Zhitenev, Joseph A. Stroscio, Santiago D. Solares Rivera, Teng Li
Recent experiments reveal that a scanning tunneling microscopy (STM) probe tip can generate a highly localized strain field in a graphene drumhead, which in turn leads to pseudomagnetic fields in the graphene that can spatially confine graphene charge

Cathodoluminescence Quantum Efficiency of Quantum Dot Thin Films

July 7, 2014
Author(s)
Heayoung Yoon, Christopher C. Bohn, Youngmin Lee, Seung H. Ko, Jonathan S. Steckel, Seth Coe-Sullivan, Nikolai B. Zhitenev
A thin film of quantum dots (QD) was used to visualize the local photo-response of polycrystalline CdTe solar cells by down-converting an electron beam of high energy to photons of visible light. The efficient photon generation in the QD film is compared

Mapping the Local Photo-Electronic Properties of Polycrystalline Solar Cells through High Resolution Laser-Beam-Induced Current Microscopy

January 1, 2014
Author(s)
Marina S. Leite, Maxim Abashin, Henri J. Lezec, Anthony G. Gianfrancesco, Albert A. Talin, Nikolai B. Zhitenev
To boost the efficiency of thin film polycrystalline solar cells that are microscopically inhomogeneous, it is imperative to understand how the grain cores (GCs) and grain boundaries (GBs) within these materials affect its overall electronic properties. By

High-Resolution Photocurrent Microscopy Using Near-Field Cathodoluminescence of Quantum Dots

June 10, 2013
Author(s)
Heayoung Yoon, Youngmin Lee, Christopher C. Bohn, Seung H. Ko, Anthony G. Gianfrancesco, Jonathan S. Steckel, Seth Coe-Sullivan, Albert A. Talin, Nikolai B. Zhitenev
We report a fast, versatile photocurrent imaging technique to visualize the local photo response of solar energy devices and optoelectronics using near-field cathodoluminescence (CL) from a homogeneous quantum dot layer. This approach is quantitatively

Modulated photocurrent spectroscopy of CdTe/CdS solar cells-equivalent circuit analysis

May 20, 2013
Author(s)
Behrang H. Hamadani, John F. Roller, Kounavis Panagiotis, Nikolai B. Zhitenev, David J. Gundlach
We have used the technique of photocurrent modulated spectroscopy to investigate the dynamic response of charge carrier transport in thin film CdTe/CdS solar cells as a function of light bias and temperature over a broad excitation frequency range. The

High-Resolution Local Current Measurement of CdTe Solar Cells

October 4, 2012
Author(s)
Heayoung Yoon, Dmitry A. Ruzmetov, Paul M. Haney, Marina S. Leite, Behrang H. Hamadani, Albert A. Talin, Nikolai B. Zhitenev
We investigate local electronic properties of CdTe solar cells using electron beam to excite electron-hole pairs and evaluate spatially resolved photocurrent characteristics. Standard semiconductor processes were used to fabricate Ohmic metal contacts on

Renormalization of the graphene dispersion velocity determined from scanning tunneling spectroscopy

September 11, 2012
Author(s)
Joseph A. Stroscio, Jungseok Chae, Nikolai B. Zhitenev, Suyong Jung, Andrea F. Young, Cory Dean, Yuanda Gao, Kenji Watanabe, Takashi Taniguchi, James Hone, Kenneth L. Shepard, Philip Kim, Lei Wang
In most metals, electrons behave as non-interacting quasiparticles with renormalized dynamical properties in the presence of electron interactions. Historically, many measurements are capable to probe the effect of interactions at the Fermi energy

Electro-Mechanical Properties of Graphene Drumheads

June 22, 2012
Author(s)
Nikolai N. Klimov, Suyong S. Jung, Shuze Zhu, Teng Li, C. Alan Wright, Santiago Solares, David B. Newell, Nikolai B. Zhitenev, Joseph A. Stroscio
The electro-mechanical properties of a suspended graphene layer are determined by scanning tunneling microscopy (STM) and spectroscopy (STS) measurements and computational simulations of the graphene membrane mechanics and morphology. The graphene membrane

Enhanced carrier transport along edges of graphene devices

March 20, 2012
Author(s)
Jungseok Chae, Suyong S. Jung, Sungjong Woo, Hongwoo Baek, Jeonghoon Ha, Young J. Song, Young-Woo Son, Nikolai Zhitenev, Joseph A. Stroscio, Young Kuk
The relation between the macroscopic charge transport properties and the microscopic carrier distribution inside conducting channels is one of the central issues in physics and future applications of graphene devices (GDs). With scanning gate microscopy

Mechanism for puddle formation in graphene

December 5, 2011
Author(s)
Shaffique Adam, Suyong S. Jung, Nikolai N. Klimov, Nikolai B. Zhitenev, Joseph A. Stroscio, Mark D. Stiles
Close to charge neutrality, graphene's energy landscape is highly inhomogeneous, forming a sea of electron-like and hole-like puddles that determine the properties of graphene at low carrier density. However, the details of puddle formation have remained

Graphene: Materials to devices

July 1, 2011
Author(s)
Jungseok Chae, Jeonghoon Ha, H. Baek, Young Kuk, Suyong S. Jung, Young J. Song, Nikolai B. Zhitenev, Joseph A. Stroscio, S.J. Woo, Y.-W. Son

Imaging of nanoscale charge transport in bulk heterojunction solar cells

June 17, 2011
Author(s)
Behrang H. Hamadani, Nadine E. Gergel-Hackett, Paul M. Haney, Nikolai B. Zhitenev
We have studied the local charge transport properties of organic bulk heterojunction solar cells based on the blends of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) with a photoconductive atomic force microscope (PCAFM). We

Microscopic Polarization in the Bilayer Graphene

April 24, 2011
Author(s)
Joseph A. Stroscio, Suyong S. Jung, Nikolai N. Klimov, David B. Newell, Nikolai B. Zhitenev, Gregory Rutter
Bilayer graphene has drawn significant attention due to the opening of a band gap in its low energy electronic spectrum, which offers a route to electronic applications that is not practical with single layer graphene. The gap can be either tunable through

Three-Dimensionally Structured CdS/CdTe Photovoltaics on Dual Interdigitated Back-Contacts

April 8, 2011
Author(s)
Carlos M. Hangarter, Behrang Hamadani, Ryan F. Need, Carlos R. Beauchamp, Hua Xu, John E. Bonevich, Nikolai Zhitenev, Daniel Josell
The fabrication and properties of three-dimensionally structured CdS/CdTe solar cells with back-contacts are described. Fabrication entails electrodeposition of CdS at submicrometer length scales on one of two metal electrodes interdigitated in a comb