Electrostatic Mechanism of Emission Enhancement in Hybrid Metal-semiconductor Light-emitting Heterostructures Page: 23

decreases at lower temperatures, resulting in an overall increase in the quantum
efficiency of the system.
In order to vary the temperature of the sample for measurement the sample is
placed within a cryostat with a viewing port such that the excitation source (laser) can
enter through the window, and the emitted light can be collected out the same window.
The cryostat is controlled by a temperature controller and allows for the temperature to
be varied between 11 and 300 K. The sample is allowed to come into thermal
equilibrium with the cryostat after each temperature change over 30 minutes. Figure 3.3
depicts the experimental setup used for temperature-dependent PL measurements.
HeCd
X Beam Stop
I Mirror
Triax 550
Grating
CCD
l Collimating Cryostat1 N
SLens /"
- - -; i
Slit
Sample
Temp.
Controller
Figure 3.3 Schematic diagram of the temperature-dependent PL experiment.
The primary change is the insertion of the sample into a cryostat, which is
used to vary the temperature of the sample from room temperature (300 K)
down to around10 K. The experiment is repeated at multiple temperatures,
and the spectrum at each temperature recorded to provide a description of
the change in emission with temperature.

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