Characterizing topography-induced contrast in photoelectron emission microscopy

• Published in: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films Surfaces, and Films, 2003-07, Vol.21 (4), p.1098-1102
• Main Authors: Siegrist, K., Williams, E. D., Ballarotto, V. W.
• Format: Article
• Language: English
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.1562185

As part of an ongoing study to quantify the imaging response of the photoelectron emission microscope (PEEM), we have investigated the effect of sample topography on PEEM contrast. Both numerical simulations and well characterized samples were used to investigate topography-induced contrast. As expected, numerical simulations show that the lateral field strength that is present at a step edge is the same order of magnitude as the perpendicular accelerating field strength (10 3   V/mm ) used for imaging. Consequently, electrons emitted near a step edge can be displaced from the image collection volume and thus generate image contrast. Simulations have also shown, in agreement with experiments, that the lateral field strength increases as the step height increases and as a result edge contrast increases with step height. In addition, we have found that for a metal line entrenched in a charged oxide, the edge contrast is observed to increase significantly. We attribute this effect to a constant lateral surface field. Furthermore, we show that edge contrast due to topography can be distinguished from a constant lateral surface field by varying the accelerating field strength.