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Open-source photoluminescence system

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Introduction

Photoluminescence is the process where a substance absorbs photons and reemits photons. The incident photons excite electrons from a lower energy level to a higher energy level. As the electrons relax from the higher energy level to the lower energy level a photon is released. For a semiconductor, the electrons are excited from a set of energy levels called the valence band to a higher set of energy levels called the conduction band. The energy area between the valence band and the conduction band is called the band gap, and no electrons can be energetically found here.

Photoluminescence (PL) Spectroscopy is a type of contactless and nondestructive probing method for determining the electronic structure of a sample. In PL Spectroscopy, a laser is fired at a sample and the resulting fluorescence is measured by a spectrometer. The measured fluorescence can be used to determine the bandgap of a semiconductor sample, impurity levels and possible defects in the sample, and the recombination mechanisms within the sample [1]. The determination of the electronic bandgap for a semiconductor is the primary focus of this work.

As previously stated, in a semiconductor the electrons are excited from the valence to the conduction band. When electrons relax from the conduction band back down to the valence band, photons will be released. These photons will have energy that matches the transition from the conduction band to the valence band. Measuring the emitted photons’ wavelength with a spectrometer will reveal the energy of the photon and therefore the size of the bandgap.


Design

Equipment List

Pavilion Integration Corp W445-40FS 445 nm laser Thor Labs LB1761-A N-BK7 Bi-Convex Lens, Ø1", f = 25.4 mm, Anit-Reflective Coating: 350-700nm Thor Labs KM100-E02 Kinematic Mount for Ø1" Optics with Visible Laser Quality Mirror Ocean Optics USB2000+VIS-NIR spectrometer Ocean Optics 600 micron VIS NIR fiber optics cable part # QP600-2-VIS-NIR

  • equipment list and specs for our ocean optics system
  • Design schematic
  • pictures of setup
  • operation instructions
this section will eventually get ported to its own protocol page.

Open source PL Design

  • equipment list and specs
  • 3D design schematic - particularly of external case to be printed by reprap
  • pictures of setup
  • operation instructions

See also