Funder

The experiments were performed using the facility of the Physics and Astronomy Department and High Pressure Science and Engineering Center (HiPSEC) at University of Nevada, Las Vegas (UNLV). HiPSEC (UNLV) is supported by U.S. Department of Energy Award DE-SC0001928.

Document Type

Poster

Publication Date

2015

Publisher

University of Nevada, Las Vegas; Center for Academic Enrichment and Outreach

Abstract

In recent years, Quantum Dot (QD) materials have attracted considerable interest due to their versatile properties and potential applications in electronics, biology, and optoelectronics, i.e. photovoltaic solar cell materials [1-2].

In 2000, RincÓn et al. reported an extensive study of the bulk material of CuInTe2 along with its comparison to its ordered defect compounds [3]. The chalcopyrite structure consists of eight atoms per unit cell. This means there are 24 vibrational modes expected for the tetragonal structure. Out of the 24 modes, 21 vibrational modes belong to optical modes, and the other 3 modes are acoustical modes. The irreducible representation of the optical modes at Γ point is given as,

Γ = 1A1 + 2A2 + 3B1 + 3B2 + 6E,

where E modes are twofold degenerate vibrations. Theoretically, other than A2 modes, the optical modes at Γ point should be Raman-active [3].

At ambient conditions, both bulk and nanoparticle of CuInTe2 exhibit chalcopyrite structure [3-5]. In bulk, the CuInTe2 chalcopyrite structure is reported to undergo a pressure-induced phase transition to an orthorhombic (d-Cmcm) structure around 3.6 GPa (see Fig. 1) [5]. In QDs, Kosuga et al reported I-42d as the space group of CuInTe2 [6]. The I-42d space group is translated to D2d or Vd point group. At ambient conditions, the Raman peaks of CuInTe2 nanocubes were observed at 121 cm-1 and 174 cm-1. The 121 cm-1 and 174 cm-1 have been assigned as A1 and E or B2 (LO) modes, respectively. The A1 mode of CuInTe2 is due to of the motion of tellurium atoms with the idle Copper and Indium atoms [7].

This present project aims on investigation the phase transition properties of CuInTe2 QDs under high pressure. We have used high pressure Raman Spectroscopy to map the variation of vibrational modes up to 7.7 GPa. A pressure-induced phase transition is observed around 2.9 GPa for the QDs in our experiment.

Keywords

Quantum Dots; CuInTe2; Raman Spectroscopy

Disciplines

Physics

Language

English


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Physics Commons

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