Dark Current Analysis of the ST-10XE CCD Camera

Scott RobbinsIthaca College Department of Physics and Astronomy

What’s a CCD?

By mapping these counts to a brightness scale, a black and white image is created.

A Charge Coupled Device captures freed photoelectric charges.

Photo Credit to Michael W. Davidson from Florida State University

What’s with those white spots?

Dark Frame taken at the Astronomy Camp at the University of Nebraska-Lincoln

Even with the lens closed, many pixels appear to detect light. These are called “dark frames”.

Can we measure this Dark Current?The slope of each line is the dark current at that temperature.

Can we predict Dark Current

behavior?We expect the Dark Current to follow the Arrhenius Law:

Linearize Dark Current vs. Temp. to create an Equation for the Dark Current!

What were the results?

Found a Band Gap Energy of 0.795eV which differs from the Band Gap energy of Silicon (1.1eV).

From this plot we found Dc (T) with an error of 0.56%

What can we learn?

Our experimental value of 0.795eV may indicate that the Band Gap energy is subject to change with temperature.

Photo: http://what-when-how.com/remote-sensing-from-air-and-space/detectors-visible-imagery-remote-sensing/

This energy is 0.55eV at cold temperatures, and 1.1eV at room temperature.

A More Detailed model of Dark Current

Arrhenius’ Law gives a good fit, but it may not give the whole picture.

Meyer-Neldel Theoretical Model says:Depletion term dominates at low temp.Diffusion term grows at temperature increases

Overall Characterized the Dark Current in the

ST-10XE CCD Camera. Found the Band Gap Energy within the

CCD. Shed some light on the mystery of

“Dark Current”. Results should help future astronomers

at IC know which temperature regions will provide best images.

Thank You!• Professor Dan Briotta• Ithaca College Department of Physics

and Astronomy