Interlayer Trions in 2D Transition-Metal Dichalcogenide Heterostructures

Biswas Chandan,SEBAIT RIYA 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.10

A dimensionally confined dielectric constant and reduced dielectric screening lead to two-dimensional transition-metal dichalcogenides (TMDs). The confined dielectric constant triggers a strong Coulomb interaction and high exciton binding energies between TMD heterostructures. Here we show a highly efficient interlayer charged exciton or trion formation and its generation sites are present in materials at room temperature. Two different transition metals (Mo, W) and chalcogenide (S, Se) elements were investigated in two different heterostructure combinations (MoS2-WS2 and MoSe2-WS2). Room temperature photoluminescence measurements demonstrate a highly efficient trion formation between and close to the heterostructure interfaces. This study highlights an effective band alignment, strong photoexciting Coulomb interaction, and formation of interlayer trions with different recombination energies. This investigation suggests the possibility of utilizing interlayer trions in promising optoelectronic devices in the future.

Negative and Positive Persistent Photoconductance in Graphene

Biswas, Chandan,Gü,neş,, Fethullah,Loc, Duong Dinh,Lim, Seong Chu,Jeong, Mun Seok,Pribat, Didier,Lee, Young Hee American Chemical Society 2011 NANO LETTERS Vol.11 No.11

<P>Persistent photoconductance, a prolonged light-induced conducting behavior that lasts several hundred seconds, has been observed in semiconductors. Here we report persistent negative photoconductance and consecutive prominent persistent positive photoconductance in graphene. Unusually large yields of negative PC (34%) and positive PC (1652%) and remarkably long negative transient response time (several hours) were observed. Such high yields were reduced in multilayer graphene and were quenched under vacuum conditions. Two-dimensional metallic graphene strongly interacts with environment and/or substrate, causing this phenomenon, which is markedly different from that in three-dimensional semiconductors and nanoparticles.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-11/nl202266h/production/images/medium/nl-2011-02266h_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl202266h'>ACS Electronic Supporting Info</A></P>

Chemically Doped Random Network Carbon Nanotube p–n Junction Diode for Rectifier

Biswas, Chandan,Lee, Si Young,Ly, Thuc Hue,Ghosh, Arunabha,Dang, Quoc Nguyen,Lee, Young Hee American Chemical Society 2011 ACS NANO Vol.5 No.12

<P>Semiconductors with higher carrier mobility and carrier density are required to fabricate a p–n junction diode for high-speed device operation and high-frequency signal processing. Here, we use a chemically doped semiconducting single-walled carbon nanotube (SWCNT) random network for a field effect transistor (FET) and demonstrate a rectifier operated at a wide range of frequencies by fabricating a p–n junction diode. The p–n diode was fabricated by using a pristine p-type SWCNT-FET where half was covered by SiO<SUB>2</SUB> and the other half was chemically doped by using benzyl viologen molecules, which was converted into an n-type channel. The half-wave rectifier of the random network SWCNT p–n junction diode clearly highlights the device operation under high input signal frequencies up to 10 MHz with very low output distortion, which a commercial silicon p–n junction diode cannot access. These results indicate that the random network SWCNT p–n junction diodes can be used as building blocks of complex circuits in a range of applications in microelectronics, optoelectronics, sensors, and other systems.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-12/nn203391h/production/images/medium/nn-2011-03391h_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn203391h'>ACS Electronic Supporting Info</A></P>

Graphene vs Carbon Nanotubes in Electronic Devices: Graphene Versus Carbon Nanotubes in Electronic Devices (Adv. Funct. Mater. 20/2011)

Biswas, Chandan,Lee, Young Hee WILEY‐VCH Verlag 2011 Advanced Functional Materials Vol.21 No.20

<P>Graphene and CNT exhibit excellent electronic and optoelectronic properties. In a Feature Article on page 3806, Young Hee Lee and Chandan Biswas review recent progress in carbon nanotube and graphene research. The review compares the electronic and opto‐electronic properties of carbon nanotubes and graphene, and their performances in devices such as transparent conducting films (transparency and sheet resistance) and field‐effect transistors (device types, ambipolarity, mobility, doping strategy, FET‐performance, logic and memory operations). </P>

Van Der Waals Force Mediated, Rotationally Aligned Dry-Transfer-Stacking of Two-Dimensional Tungsten Diselenide

Daw Debottam,Sebait Riya,Biswas Chandan 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.10

Rotationally aligned, two-dimensional (2D), transition-metal dichalcogenides (TMDs) exhibit unique electronic, optical, and optoelectronic properties compared to random stacking. Rotationally aligned graphene stacking was demonstrated previously for numerous exotic phenomena, such as superconductivity, resonant tunneling, and moiré pattern. However, rotationally aligned dry-transfer techniques of TMDs, have yet to be demonstrated. Here, we show a simple method of selective cutting of a few-layer tungsten diselenide (WSe2) flake and rotationally aligning it by using dry-transfer stacking. The dry transfer techniques used for this study were adapted to maintain low sample contamination, a high-quality interface, a low number of defects. A combination of viscoelastic and thermoelastic materials was used for the TMD pickup and release to facilitate the rotationally aligned stacking. Aligned WSe2 stacks were characterized by Raman and photoluminescence spectroscopy to evaluate the integrity of the fabricated stack. This study highlights the possibility of using a rotationally aligned, artificial stacking method for exfoliated TMD materials for future electronic and optoelectronic applications.

Layer-by-Layer Doping of Few-Layer Graphene Film

Gü,neş,, Fethullah,Shin, Hyeon-Jin,Biswas, Chandan,Han, Gang Hee,Kim, Eun Sung,Chae, Seung Jin,Choi, Jae-Young,Lee, Young Hee American Chemical Society 2010 ACS NANO Vol.4 No.8

<P>We propose a new method of layer-by-layer (LbL) doping of thin graphene films. Large area monolayer graphene was synthesized on Cu foil by using the chemical vapor deposition method. Each layer was transferred on a polyethylene terephthalate substrate followed by a salt-solution casting, where the whole process was repeated several times to get LbL-doped thin layers. With this method, sheet resistance was significantly decreased up to ∼80% with little sacrifice in transmittance. Unlike samples fabricated by topmost layer doping, our sample shows better environmental stability due to the presence of dominant neutral Au atoms on the surface which was confirmed by angle-resolved X-ray photoelectron spectroscopy. The sheet resistance of the LbL-doped four-layer graphene (11 × 11 cm<SUP>2</SUP>) was 54 Ω/sq at 85% transmittance, which meets the technical target for industrial applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-8/nn1008808/production/images/medium/nn-2010-008808_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn1008808'>ACS Electronic Supporting Info</A></P>

Highly Interconnected Si Nanowires for Improved Stability Li-Ion Battery Anodes

Nguyen, Hung T.,Yao, Fei,Zamfir, Mihai R.,Biswas, Chandan,So, Kang Pyo,Lee, Young Hee,Kim, Seong Min,Cha, Seung Nam,Kim, Jong Min,Pribat, Didier Wiley (John WileySons) 2011 Advanced energy materials Vol.1 No.6

Development of Large Area Nanostructured Silicon-Hydrogen Alloy Material with Improved Stability for Solar Cell Application by Argon Dilution Method

Arka Dey,Mrinmay Das,Joydeep Datta,Rajkumar Jana,Joydeep Dhar,Sayantan Sil,Debasish Biswas,Chandan Banerjee,Partha Pratim Ray 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.4

Here we have presented the results of large area (30 × 30 cm2) siliconhydrogenalloy material and solar cell by argon dilution method. As analternative to hydrogen dilution, argon dilution method has been appliedto develop single junction solar cell with appreciable stability. Optimization of deposition conditions revealed that 95% argon dilutiongives a nanostructured material with improved transport property andless light induced degradation. The minority carrier diffusion length (Ld)and mobility-lifetime (μτ) product of the material with 95% argondilution degrades least after light soaking. Also the density of states(DOS) below conduction level reveals that this material is lessdefective. Solar cell with this argon diluted material has been fabricatedwith all the layers deposited by argon dilution method. Finally we havecompared the argon diluted solar cell results with the optimizedhydrogen diluted solar cell. Light soaking study proves that it is possibleto develop stable solar cell on large area by argon dilution method andthat the degradation of argon diluted solar cell is less than that ofhydrogen diluted one.