Unformatted text preview: electron can produce up to 2800 electron
hole pairs • External bias required to generate current
– Conversion produces a gain of about 1000 so less subsequent
amplification required • Geometry
– Typically installed on bottom of lens pole piece in 2 or 4
quadrants CBEMS 164 – XRD, SEM & Microanalysis: Lecture 11
! 11 CBEMS 164 – XRD, SEM & Microanalysis: Lecture 11
! 12 Semiconductor Detectors!
! TTL Lenses!
! • With FESEM and short WD, SE
electrons are trapped by lens
and spiral up column
! • Basis of in-lens detector • Annular detector results in loss
of apparent side lighting effect.
• High resolution results
• Minimizes influence of SE
electrons generated by
interaction of BS electrons with
chamber walls etc. CBEMS 164 – XRD, SEM & Microanalysis: Lecture 11
! 13 In-Lens Detectors!
! • High resolution requires small probe size
Small probe size requires strong excitation of probe forming lens
Very short working distance required • Majority of signal flux spirals back up through lens pole piece
– Everhart-Thornley and SS BS detector become inefficient • SE...
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- Fall '08
- Electron, XRD, Scanning electron microscope, microanalysis