1. LED Experiment Edward Cazalas Chris Sopko 9/9/13

2. Objective Test sensitivity of graphene device to various wavelengths of light so that the utilization of Raman laser for active area experiment can be assessed. Raman machine would be preferable due to magnification, small beam size of laser, and automated translation of stage. If graphene device shows field effect response to light of wavelength near 488 nm, Raman experiment may be successful. However, as 488 nm (2.54 eV) photons have energy below band gap of SiC (3 eV for 6H), the responsiveness of graphene would need to be explained with modification of understanding of band gap structure.

3. Light Emitting Diodes Sensitivity of graphene device to various wavelengths of light is tested with LEDs emitting specific wavelength bands. “LED Box” wired for easy switching of LED light. Wavelength Red: 620-640 nm Yellow: 585-595 nm Green: 520-530 nm Blue: 465-475 nm UV: 405 nm Energy Red: 1.94-1.99 eV Yellow: 2.08-2.12 eV Green: 2.34-2.38 eV Blue: 2.61-2.67 eV UV: 3.06 eV

5. Color of line corresponds to wavelength of light. As photon energy increases, field effect should become more prominent. UV Dark

6. Expect magnitude of graphene response to increase with increasing photon energy (green inconsistent)

7. Expect magnitude of graphene response to increase with increasing photon energy (red and blue inconsistent)

8. Backgate = 0 V exhibits expected response (observing magnitude of response but not sign)

9. Conclusion/Future Work Graphene device shows response to wavelengths near 488 nm… Raman can be utilized. Graphene device response is not consistent with expected response (greater response magnitude with greater photon energy)… Photon flux different for each LED ? -> Need to accurately measure power Experimental issues ? -> Perform experiment again Graphene response magnitude not consistent with field effect curves… Refined experimental procedure.

10. Additional Slides