Scanning Electron Microscopy and X-Ray Microanalysis

168

11

012 345

Beam energy (keV)

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Se

condar

y elec

tron coefficien

t

Reimer and Tollkamp (1980)

Moncrieff and Barker (1976)

Bongeler et al. (1993)

Shimizu (1974)

Kanter (1961)

Bruining and De Boer (1938)

Bronstein and Fraiman (1969)

Hilleret et al. (2000)

Aluminum

. Fig. 11.4 Secondary electron
coefficient, δ, as a function of
beam energy for Al (Taken from
the data of various authors)

01234 5

Beam energy (keV)

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

BSE and SE coefficients

BSE and SE coefficients: gold

Secondary electrons

Backscattered electrons

. Fig. 11.3 Secondary electron
coefficient, δ, and backscatter
electron coefficient, η, as a
function of beam energy for Au,
taken from the data of Bongeler
et al. ( 1993 )

remove such artifacts. However, even with ion beam clean-

ing, it must be recognized that at the vacuum levels of the

conventional “high vacuum” SEM, for example, 10−^4 Pa

(10−^6 torr), the partial pressure of oxygen is sufficiently

high that a monolayer of oxide will form on a reactive sur-

face such as Al in a matter of seconds. Thus, while ion beam

milling may successfully remove contamination, oxide for-

mation at least at the monolayer level may be unavoidable

Chapter 11 · Low Beam Energy SEM