title: Photoresponse of a Single Y-Junction Carbon Nanotube.
abstract: We report investigation of optical response in a single strand of a branched carbon nanotube (CNT), a Y-junction CNT composed of multiwalled CNTs. The experiment was performed by connecting a pair of branches while grounding the remaining one. Of the three branch combinations, only one combination is optically active which also shows a nonlinear semiconductor-like I-V curve, while the other two branch combinations are optically inactive and show linear ohmic I-V curves. The photoresponse includes a zero-bias photocurrent from the active branch combination. Responsivity of ≈1.6 mA/W has been observed from a single Y-CNT at a moderate bias of 150 mV with an illumination of wavelength 488 nm. The photoresponse experiment allows us to understand the nature of internal connections in the Y-CNT. Analysis of data locates the region of photoactivity at the junction of only two branches and only the combination of these two branches (and not individual branches) exhibits photoresponse upon illumination. A model calculation based on back-to-back Schottky-type junctions at the branch connection explains the I-V data in the dark and shows that under illumination the barriers at the contacts become lowered due to the presence of photogenerated carriers.
authors.affiliation: Unit for Nanosciences, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences , Salt Lake, Kolkata, West Bengal 700091, India.
authors.forename: Sudeshna
authors.initials: S
authors.lastname: Samanta
authors.affiliation: Department of Physics and Astronomy and Clemson Nanomaterials Centre, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Deepika
authors.initials: D
authors.lastname: Saini
authors.affiliation: Bose Institute , 93/1, Acharya Prafulla Chandra Road, Kolkata, West Bengal 700009, India.
authors.forename: Achintya
authors.initials: A
authors.lastname: Singha
authors.affiliation: Unit for Nanosciences, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences , Salt Lake, Kolkata, West Bengal 700091, India.
authors.forename: Kaustuv
authors.initials: K
authors.lastname: Das
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of California, San Diego , La Jolla, California 92093, United States.
authors.forename: Prabhakar R
authors.initials: PR
authors.lastname: Bandaru
authors.affiliation: Department of Physics and Astronomy and Clemson Nanomaterials Centre, Clemson University , Clemson, South Carolina 29634, United States.
authors.forename: Apparao M
authors.initials: AM
authors.lastname: Rao
authors.affiliation: Unit for Nanosciences, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences , Salt Lake, Kolkata, West Bengal 700091, India.
authors.forename: Arup Kumar
authors.initials: AK
authors.lastname: Raychaudhuri
keywords: Schottky barrier; Y-junction; low-temperature electrical transport; photoresponse; single carbon nanotube; zero-bias photocurrent