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Temperature Dependence of the Energy Gap of InP Quantum Dots: A Sophomore-level Nanomaterials Experiment

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Conference

2012 ASEE Annual Conference & Exposition

Location

San Antonio, Texas

Publication Date

June 10, 2012

Start Date

June 10, 2012

End Date

June 13, 2012

ISSN

2153-5965

Conference Session

Physics Poster Session

Tagged Division

Engineering Physics & Physics

Page Count

10

Page Numbers

25.1269.1 - 25.1269.10

DOI

10.18260/1-2--22026

Permanent URL

https://peer.asee.org/22026

Download Count

90

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Paper Authors

biography

Jennifer Rose Annoni University of St. Thomas

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Jennifer Annoni is currently an Undergraduate student studying Electrical Engineering and Physics at the University of St. Thomas. She will graduate in May of 2012. Her plans are to pursue graduate school in the field of Engineering.

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Adam S. Green University of St. Thomas

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Adam S. Green is an Associate Professor of physics at the University of St. Thomas in St. Paul, Minn. He received his B.A.
from Gustavus Adolphus College and his M.S. and Ph.D. in atomic, molecular,
and optical physics at the University of Nebraska, Lincoln. He works with undergraduate physics and engineering students on research projects in physical optics, with an emphasis on interdisciplinary applications of polarimetry.

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Marie Lopez del Puerto University of Saint Thomas

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Marie Lopez del Puerto completed her B.S. in physics at Universidad de las Americas, Puebla, in Puebla, Mexico, and her Ph.D. in physics at the University of Minnesota, Twin Cities, in Minneapolis, Minn. She is currently an Assistant Professor in the Physics Department at the University of St. Thomas in St. Paul, Minn. Her research interests include the structural, optical and electronic properties of nanoscale systems, computational physics, and physics and engineering education.

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Abstract

Temperature dependence of the energy gap of CdSe quantum dots: a sophomore-level nanomaterials experimentThis paper presents a sophomore-level experiment that allows students to see the“particle-in-a-box” behavior of a real system (quantum dots of different sizes) andexplores the temperature dependence of the quantum dots’ energy gap. Quantum dots arenanometer-sized clusters of atoms that contain anywhere from a few to a few thousandatoms. Because of their size, quantum effects become important, which makes theminteresting to study and potentially useful for technological applications. Forsemiconductor quantum dots of a given material, the size of the quantum dot determinesthe energy gap (the energy difference between the HOMO – highest occupied molecularorbital, and the LUMO – lowest unoccupied molecular orbital) of that particular quantumdot. As a result of their different sizes, the cadmium selenide quantum dots studied(which we obtain from Cenco Physics) emit light of different wavelength (and hencecolor) when excited by ultraviolet light. In addition to being size dependent, the energygap also depends on temperature. In the experiment, the cadmium selenide quantum dotsare exposed to different temperatures and, by using a spectrometer, the wavelengths atwhich they emit light when excited by an ultraviolet source are recorded and compared.Using the model of an electron and a hole inside a spherical infinite potential well, therecorded wavelengths can be related to the size of the quantum dots at varioustemperatures. The experimental data is then compared to the changes that would beexpected from classical volume expansion and from the Varshni equation. Both methodsprovide an adequate explanation of the temperature dependence of the energy gap of thecadmium selenide quantum dots studied.



Annoni, J. R., & Green, A. S., & Lopez del Puerto, M. (2012, June), Temperature Dependence of the Energy Gap of InP Quantum Dots: A Sophomore-level Nanomaterials Experiment Paper presented at 2012 ASEE Annual Conference & Exposition, San Antonio, Texas. 10.18260/1-2--22026

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