Material Density Electron Distribution in SEY Layer Band Gap - - PowerPoint PPT Presentation

S econdary E lectron P rimary E lectron P ath

~500eV <20eV C

• nductive S

ubstrate S E Y Layer P rimary E lectron S econdary E lectrons

Secondary electron yield (SEY) is a function of:

• Material Density
• Electron Distribution in SEY Layer
• Band Gap
• Primary Electron Energy

Some of the best materials for high SEY are electrical insulators/semiconductors:

• Film thickness
• Positive charging hinders secondary electron emission

2

200 400 600 800 1 2 3 4 5

Electron Gain (secondaries/primary) Primary Electron Energy (eV) MgO 20Å 30Å 40Å Al2O3 20Å 30Å 40Å

3

25 50 75 100 125 150 175 200 225 2 3 4 5 6 7

• Max. Gain vs. Thickness

MgO Al2O3

Electron Gain (secondaries/primary)

Sample Thickness (Å)