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295 results on '"Sankaran, R. Mohan"'

2. Intervalence Plasmons in Boron-Doped Diamond

Author

Bhattacharya, Souvik, Boyd, Jonathan, Reichardt, Sven, Allard, Valentin, Talebi, Amir Hossein, Maccaferri, Nicolò, Shenderova, Olga, Lereu, Aude L., Wirtz, Ludger, Strangi, Giuseppe, and Sankaran, R. Mohan

Subjects
Condensed Matter - Materials Science, Physics - Optics
Abstract

Doped semiconductors can exhibit metallic-like properties ranging from superconductivity to tunable localized surface plasmon resonances. Diamond is a wide-bandgap semiconductor that is rendered electronically active by incorporating a hole dopant, boron. While the effects of boron doping on the electronic band structure of diamond are well-studied, any link between charge carriers and plasmons, has never been shown. Here, we report intervalence plasmons in boron-doped diamond, defined as collective electronic excitations between the valence subbands, opened up by the presence of holes. Evidence for these low-energy excitations is provided by valence electron energy loss spectroscopy and near-field infrared spectroscopy. The measured spectra are subsequently reproduced by first-principles calculations based on the contribution of intervalence band transitions to the dielectric function. Our calculations also reveal that the real part of the dielectric function exhibits a crossover characteristic of metallicity. These results suggest a new mechanism for inducing plasmon-like behavior in doped semiconductors, and the possibility of attaining such properties in diamond, a key emerging material for quantum information technologies.

Published
2024
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3. Intervalence plasmons in boron-doped diamond.

Author

Bhattacharya, Souvik, Boyd, Jonathan, Reichardt, Sven, Allard, Valentin, Talebi, Amir Hossein, Maccaferri, Nicolò, Shenderova, Olga, Lereu, Aude L., Wirtz, Ludger, Strangi, Giuseppe, and Sankaran, R. Mohan

Subjects
SURFACE plasmon resonance, ELECTRONIC band structure, PERMITTIVITY, PARTICLES (Nuclear physics), DOPED semiconductors, ELECTRON energy loss spectroscopy
Abstract

Doped semiconductors can exhibit metallic-like properties ranging from superconductivity to tunable localized surface plasmon resonances. Diamond is a wide-bandgap semiconductor that is rendered electronically active by incorporating a hole dopant, boron. While the effects of boron doping on the electronic band structure of diamond are well-studied, any link between charge carriers and plasmons has never been shown. Here, we report intervalence plasmons in boron-doped diamond, defined as collective electronic excitations between the valence subbands, opened up by the presence of holes. Evidence for these low-energy excitations is provided by valence electron energy loss spectroscopy and near-field infrared spectroscopy. The measured spectra are subsequently reproduced by first-principles calculations based on the contribution of intervalence band transitions to the dielectric function. Our calculations also reveal that the real part of the dielectric function exhibits a crossover characteristic of metallicity. These results suggest a new mechanism for inducing plasmon-like behavior in doped semiconductors, and the possibility of attaining such properties in diamond, a key emerging material for quantum information technologies. Doping diamond with boron is well known to change its electronic structure. Here, the authors reveal low-energy collective excitations in boron-doped diamond, which originate from intervalence band transitions. [ABSTRACT FROM AUTHOR]

Published
2025
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7. Metal-Insulator Transition in Variably Doped (Bi1-xSbx)2Se3 Nanosheets

Author

Lee, Chee Huei, He, Rui, Wang, ZhenHua, Qiu, Richard L. J., Kumar, Ajay, Delaney, Conor, Beck, Ben, Kidd, T. E., Chancey, C. C., Sankaran, R. Mohan, and Gao, Xuan P. A.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Topological insulators are novel quantum materials with metallic surface transport, but insulating bulk behavior. Often, topological insulators are dominated by bulk contributions due to defect induced bulk carriers, making it difficult to isolate the more interesting surface transport characteristics. Here, we report the synthesis and characterization of nanosheets of topological insulator Bi2Se3 with variable Sb-doping level to control the electron carrier density and surface transport behavior. (Bi1-xSbx)2Se3 thin films of thickness less than 10 nm are prepared by epitaxial growth on mica substrates in a vapor transport setup. The introduction of Sb in Bi2Se3 effectively suppresses the room temperature electron density from ~4 \times 10^13/cm^2 in pure Bi2Se3 (x = 0) to ~2 \times 10^12/cm^2 in (Bi1-xSbx)2Se3 at x ~0.15, while maintaining the metallic transport behavior. At x > ~0.20, a metal-insulator transition (MIT) is observed indicating that the system has transformed into an insulator in which the metallic surface conduction is blocked. In agreement with the observed MIT, Raman spectroscopy reveals the emergence of vibrational modes arising from Sb-Sb and Sb-Se bonds at high Sb concentrations, confirming the appearance of Sb2Se3 crystal structure in the sample. These results suggest that nanostructured chalcogenide films with controlled doping can be a tunable platform for fundamental studies and electronic applications of topological insulator systems., Comment: accepted for publication in Nanoscale. See http://gaogroup.case.edu/index.php/Publications for related papers from our lab

Published
2013
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13. Plasma Electrochemistry: A Novel Chemical Process for the Synthesis and Assembly of Nanomaterials

Author

Lee, Seung Whan, Sankaran, R. Mohan, Drake, Gordon W. F., Editor-in-chief, Bandrauk, Andre D., Series editor, Bartschat, Klaus, Series editor, Becker, Uwe, Series editor, Burke, Philip George, Series editor, Compton, Robert N, Series editor, Flannery, M. R., Series editor, Joachain, Charles J., Series editor, Lambropoulos, Peter, Series editor, Leuchs, Gerd, Series editor, Meystre, Pierre, Series editor, Bonitz, Michael, editor, Lopez, Jose, editor, Becker, Kurt, editor, and Thomsen, Hauke, editor

Published
2014
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22. Electrostatic charging of wind-blown dust and implications on dust transport

Author

Toth Joseph R., Rajupet Siddharth, Squire Henry, Volbers Blaire, Zhou Jùn, Li Xie, Sankaran R. Mohan, and Lacks Daniel J.

Subjects
Environmental sciences, GE1-350
Abstract

It is well known that electric fields occur in wind-blown dust, due to the triboelectric charging of particles as they collide. Triboelectric charging, or contact electrification, is a poorly understood and complex phenomenon. It is especially important in granular systems, as the high surface-to-volume ratio can lead to the build-up of large amounts of charge. A particularly surprising effect, which is important in dust systems, is that charge transfer occurs in systems of a single composition, such that there is a particle-size dependent polarity of the particles. Here, we use a combined experimental and theoretical approach to elucidate the electrostatic charging that occurs during dust storms, and the effects of this electrostatic charging on dust transport. We create laboratory-scale wind-blown dust systems, and study the electrostatic charging. We find that larger particles tend to charge positive and to stay at or near the sand bed, while smaller particles tend to charge negative and get lofted to higher elevations. This self-segregating of charged particles would lead to electric fields within a dust storm. Our results show that electric fields then increase the dust transport by more easily lofting charged particles.

Published
2019
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34. Ultrathin-film optical coating for angle-independent remote hydrogen sensing

Author

ElKabbash, Mohamed, primary, Sreekanth, Kandammathe Valiyaveedu, additional, Fraiwan, Arwa, additional, Cole, Jonathan, additional, Alapan, Yunus, additional, Letsou, Theodore, additional, Hoffman, Nathaniel, additional, Guo, Chunlei, additional, Sankaran, R Mohan, additional, Gurkan, Umut A, additional, Hinczewski, Michael, additional, and Strangi, Giuseppe, additional

Published
2020
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43. Engineering the surface morphology of inkjet printed Ag by controlling solvent evaporation during plasma conversion of AgNO3 inks.

Author

Sui, Yongkun, Hess-Dunning, Allison, Radwan, Aziz N., Sankaran, R. Mohan, and Zorman, Christian A.

Abstract

In this paper, we show that the surface morphology of silver (Ag) structures prepared by plasma conversion of particle-free inks can be controlled by solvent evaporation effcts. A series of three ethylene-glycol-based solvents were used to systematically vary the vapor pressure of the ink. Following inkjet printing, films were converted by exposure to a low-pressure, low-temperature radio-frequency (RF) plasma. Scanning electron microscopy (SEM) and profilometry of the Ag films showed that the surface roughness and porosity depend on the vapor pressure of the ink solvent, with each increasing with decreasing vapor pressure. As a result of changes to the porosity, electrical resistivity increased as the solvent vapor pressure decreased. To demonstrate the utility of a printing technique for rough and porous metal films, we fabricated Ag-based hydrogen peroxide (H2O2) sensors using inks comprised of the three ethylene-glycol-based solvents. The sensitivity of these sensors was found to increase with the surface roughness and porosity, which in turn, was related to the vapor pressure of the solvent. [ABSTRACT FROM AUTHOR]

Published
2022
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44. Microplasmas for Advanced Materials and Devices

Author

Chiang, Wei Hung, Mariotti, Davide, Sankaran, R. Mohan, Eden, J. Gary, Ostrikov, Kostya, Chiang, Wei Hung, Mariotti, Davide, Sankaran, R. Mohan, Eden, J. Gary, and Ostrikov, Kostya

Abstract

Microplasmas are low-temperature plasmas that feature microscale dimensions and a unique high-energy-density and a nonequilibrium reactive environment, which makes them promising for the fabrication of advanced nanomaterials and devices for diverse applications. Here, recent microplasma applications are examined, spanning from high-throughput, printing-technology-compatible synthesis of nanocrystalline particles of common materials types, to water purification and optoelectronic devices. Microplasmas combined with gaseous and/or liquid media at low temperatures and atmospheric pressure open new ways to form advanced functional materials and devices. Specific examples include gas-phase, substrate-free, plasma-liquid, and surface-supported synthesis of metallic, semiconducting, metal oxide, and carbon-based nanomaterials. Representative applications of microplasmas of particular importance to materials science and technology include light sources for multipurpose, efficient VUV/UV light sources for photochemical materials processing and spectroscopic materials analysis, surface disinfection, water purification, active electromagnetic devices based on artificial microplasma optical materials, and other devices and systems including the plasma transistor. The current limitations and future opportunities for microplasma applications in materials related fields are highlighted.

Published
2020

48. Hydrogen Sensing Using Thin-Film Perfect Light Absorber

Author

ElKabbash, Mohamed, primary, Sreekanth, Kandammathe V., additional, Alapan, Yunus, additional, Kim, Myeongseop, additional, Cole, Jonathan, additional, Fraiwan, Arwa, additional, Letsou, Theodore, additional, Li, Yandong, additional, Guo, Chunlei, additional, Sankaran, R. Mohan, additional, Gurkan, Umut A., additional, Hinczewski, Michael, additional, and Strangi, Giuseppe, additional

Published
2019
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