Dark Current Analysis of the ST-10XE CCD Camera Scott Robbins Ithaca College Department of Physics and Astronomy

What’s a CCD? A Charge Coupled Device captures freed photoelectric charges. By mapping these counts to a brightness scale, a black and white image is created. Full bucket white, empty bucket black. Charge in voltage, held by cap to send to comp for matrix of numbers. Photo Credit to Michael W. Davidson from Florida State University

What’s with those white spots? Even with the lens closed, many pixels appear to detect light. These are called “dark frames”. Matrix of numbers Dark Frame taken at the Astronomy Camp at the University of Nebraska-Lincoln

Can we measure this Dark Current? The slope of each line is the dark current at that temperature. State that you took exposures at increasing time intervals and that these are fitted lines.

Can we predict Dark Current behavior? We expect the Dark Current to follow the Arrhenius Law: Remember that light hitting surface needs same bandgap kick as thermal energy! That’s why Arrhenius! Linearize Dark Current vs. Temp. to create an Equation for the Dark Current!

What were the results? From this plot we found Dc (T) with an error of 0.56% Should pass through origin, and instead has y intercept 1.0176 ± 0.0158. This relates to the bias being different at different temperatures because Neyer and D0! Found a Band Gap Energy of 0.795eV which differs from the Band Gap energy of Silicon (1.1eV).

What can we learn? This energy is 0.55eV at cold temperatures, and 1.1eV at room temperature. Dark current needs same kick as photoelec, just because of thermal. Don’t even state directions of charge movement, just energy. 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/

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 The reason our lines didn’t converge to same offset/intercept is because D0 has a temperature dependence! Diffusion is kinetic energy of atoms in the solid.

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 Thank generally everyone who came!