The accelerating voltage of electron beam in SEM for chemical micro-analysis using EDS is normally from 20 kV to 30 kV [1], while the accelerating voltages for TEM-EDS analysis are normally between 200 kV and 400 kV. (also refer to Dependence of EDS on Accelerating Voltages of Incident Electrons)
For effective generation of X-ray by ionization processed by electron interaction, the overvoltage U should be greater than 1.3 because the characteristic-to-continuum ratio (or the X-ray peak to background ratio, P/B) of X-ray signal is reduced substantially as E0 (energy of incident beam) approaches Ei (ionization energy). An overvoltage of ~ 2.0 generally results in a sufficient value of the peak-to-background to permit detection of concentration levels to trace levels for most elements. It is necessary to mention that the low energy X-ray lines, e.g. Cu(L) at 0.93 keV instead of Cu(K) at 8.04 keV, are used at low accelerating voltage of incident electrons.
Table 4610a lists the KMoO factors for Mo Lα1 and O K X-rays at accelerating voltages from 15 keV to 30 keV. The X-rays are collected from a bulk sample in an SEM system. At the lower voltage 15 keV, both intensities of Mo Lα1 and O K X-rays are higher and the KMoO factor is lower.
Table 4610a. KMoO Factors for Mo Lα1 and O K X-rays at accelerating voltages from 15 keV to 30 keV. |
|
Intensity |
|
15 keV |
20 keV |
25 keV |
30 keV |
Mo Lα1 |
562.54 |
518.47 |
511.56 |
502.05 |
O K |
117.33 |
71.33 |
59.58 |
52.48 |
KMoO Factors |
4.79 |
7.27 |
8.59 |
9.57 |
For light element matrices the spatial resolution is substantially degraded. On the other hand, in light-element analysis it is also desirable to use a low accelerating voltage in the interest of minimizing absorption corrections. For instance, accelerating voltage down to 0.8 kV have been proved practical to distinguish very small (nm) inclusions of C in an O-rich ceramic matrix [2].
In comparison between EDS measurements of low- and high-energy incident electron beams, the low-energy method has the disadvantage of reducing the number of peaks in the spectrum that can be excited by the incident beam. Therefore, there are a number of peaks at these low energies and thus these peaks overlap, resulting in inaccurate elemental identification and quantification. However, For EDS measurements with high-energy beams, peak overlap may not be a critical problem so that the position and intensity of the high energy peaks can allow more accurate identification and quantification.
Furthermore, a typical problem in performing analysis at low beam energy is the effect of surface layer, which is different from the interior because of native surface oxidation, conductive coating for minimizing charging effect, and/or contamination. At high beam energy, the thickness of this surface layer is a small fraction of the excitation range so that the effect on EDS measurement is negligible. However, at low beam energy, the total sampling depth becomes so shallow that the surface layer contributes a significant fraction of the analyzed volume.
From Tables 4610b to 4610e, we can know that there are more peak overlaps between elements or more elements which are not detectable at low accelerating voltages.
Table 4610b. Periodic Table showing typical choices of X-ray lines for EDS operation in the range of accelerating voltages higher than 50 keV. |
1 |
2 |
|
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
|
|
|
1 H |
|
2 He |
|
|
|
|
|
|
|
|
|
3 Li
|
4 Be
Kα 0.110 |
|
5 B
Kα 0.183 |
6 C
Kα 0.277 |
7 N
Kα 0.392 |
8 O
Kα 0.525 |
9 F
Kα 0.677 |
10 Ne
Kα 0.848 |
|
|
You can download the excel file in order to highlight the elements in your EDS profile. |
|
|
|
|
|
|
11 Na
Kα 1.041 |
12 Mg
Kα 1.253 |
|
Not detectable |
|
|
K-shell |
|
|
|
|
L-shell |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
13 Al
Kα 1.486 |
14 Si
Kα 1.739 |
15 P
Kα 2.013 |
16 S
Kα 2.307 |
17 Cl
Kα 2.621 |
18 Ar
Kα 2.957 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
19 K
Kα 3.312
|
20 Ca
Kα 3.690
|
|
21 Sc
Kα 4.088
|
22 Ti
Kα 4.508
Kβ 4.931
|
23 V
Kα 4.949
|
24 Cr
Kα 5.411
|
25 Mn
Kα 5.894
|
26 Fe
Kα 6.398
|
27 Co
Kα 6.924
|
28 Ni
Kα 7.471
|
29 Cu
Kα 8.040
Kβ 8.91 |
30 Zn
Kα 8.630
|
31 Ga
Kα 9.241
|
32 Ge
Kα 9.874
|
33 As
Kα 10.530
|
34 Se
Kα 11.207
|
35 Br
Kα 11.907
|
36 Kr
Kα 12.631
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
37 Rb
Kα 13.373
|
38 Sr
Kα 14.140
|
|
39 Y
Kα 14.931
|
40 Zr
Kα 15.744
|
41 Nb
Kα 16.581
|
42 Mo
Kα 17.441 |
43 Tc
Kα 18.325 |
44 Ru
Kα 19.233 |
45 Rh
Kα 20.216 |
46 Pd
Lα 2.838 |
47 Ag
Lα 2.984 |
48 Cd
Lα 3.133 |
49 In
Lα 3.286 |
50 Sn
Lα 3.443 |
51 Sb
Lα 3.604 |
52 Te
Lα 3.769
|
53 I
Lα 3.937 |
54 Xe
Lα 4.109 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
55 Cs
Lα 4.286 |
56 Ba
Lα 4.465 |
{57-70} |
71 Lu
Lα 7.654 |
72 Hf
Lα 7.898 |
73 Ta
Lα 8.145 |
74 W
Lα 8.396 |
75 Re
Lα 8.651 |
76 Os
Lα 8.910 |
77 Ir
Lα 9.174 |
78 Pt
Lα 9.441 |
79 Au
Lα 9.712 |
80 Hg
Lα 9.987 |
81 Tl
Lα 10.267 |
82 Pb
Lα 10.550 |
83 Bi
Lα 10.837 |
84 Po
Lα 11.129 |
85 At
Lα 11.425 |
86 Rn
Lα 11.725 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
87 Fr
Lα 12.029 |
88 Ra
Lα 12.340 |
[89-102] |
103 Lr
|
104 Rf
|
105 Db
|
106 Sg
|
107 Bh
|
108 Hs
|
109 Mt
|
110 Uun
|
111 Uuu
|
112 Uub
|
|
114 Uuq
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
{lanthanides} {57-70} |
57 La
Lα 4.650 |
58 Ce
Lα 4.839 |
59 Pr
Lα 5.033 |
60 Nd
Lα 5.229 |
61 Pm
Lα 5.432 |
62 Sm
Lα 5.635 |
63 Eu
Lα 5.845
|
64 Gd
Lα 6.056
|
65 Tb
Lα 6.272 |
66 Dy
Lα 6.494 |
67 Ho
Lα 6.719 |
68 Er
Lα 6.947 |
69 Th
Lα 7.179 |
70 Yb
Lα 7.414 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
{actinides} [89-102] |
89 Ac
Lα 12.650 |
90 Th
Lα 12.967
|
91 Pa
Lα 13.288
|
92 U
Lα 13.612
|
93 Np
Lα 13.942
|
94 Pu
Lα 14.276
|
95 Am
Lα 14.615
|
96 Cm
|
97 Bk
|
98 Cf
|
99 Es
|
100 Fm
|
101 Md
|
102 No
|
|
|
|
Table 4610c. Periodic Table showing typical choices of X-ray lines for EDS operation in the range of accelerating voltages between 10 keV and 30 keV (U > 2 for Ec ≤ 10 keV). |
1 |
2 |
|
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
|
|
|
1 H |
|
2 He |
|
|
|
|
|
|
|
|
|
3 Li
|
4 Be
Kα 0.110 |
|
5 B
Kα 0.183 |
6 C
Kα 0.277 |
7 N
Kα 0.392 |
8 O
Kα 0.525 |
9 F
Kα 0.677 |
10 Ne
Kα 0.848 |
|
|
You can download the excel file in order to highlight the elements in your EDS profile. |
|
|
|
|
|
|
11 Na
Kα 1.041 |
12 Mg
Kα 1.253 |
|
Not detectable |
|
|
K-shell |
|
|
K- & L-shell |
|
L-shell |
|
|
L- & M-shell |
|
|
M-shell |
|
|
|
|
|
|
|
|
|
13 Al
Kα 1.486 |
14 Si
Kα 1.739 |
15 P
Kα 2.013 |
16 S
Kα 2.307 |
17 Cl
Kα 2.621 |
18 Ar
Kα 2.957 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
19 K
Kα 3.312
|
20 Ca
Kα 3.690
|
|
21 Sc
Kα 4.088
|
22 Ti
Kα 4.508
Kβ 4.931
|
23 V
Kα 4.949
|
24 Cr
Kα 5.411
Lα 0.573
|
25 Mn
Kα 5.894
Lα 0.637
|
26 Fe
Kα 6.398
Lα 0.705
|
27 Co
Kα 6.924
Lα 0.776
|
28 Ni
Kα 7.471
Lα 0.851
|
29 Cu
Kα 8.040
Kβ 8.91
Lα 0.930 |
30 Zn
Kα 8.630
Lα 1.012
|
31 Ga
Lα 1.098
|
32 Ge
Lα 1.188
|
33 As
Lα 1.282
|
34 Se
Lα 1.379
|
35 Br
Lα 1.480
|
36 Kr
Lα 1.586
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
37 Rb
Lα 1.694 |
38 Sr
Lα 1.806 |
|
39 Y
Lα 1.922 |
40 Zr
Lα 2.042 |
41 Nb
Lα 2.166 |
42 Mo
Lα 2.293 |
43 Tc
Lα 2.424 |
44 Ru
Lα 2.558 |
45 Rh
Lα 2.696 |
46 Pd
Lα 2.838
|
47 Ag
Lα 2.984 |
48 Cd
Lα 3.133 |
49 In
Lα 3.286 |
50 Sn
Lα 3.443 |
51 Sb
Lα 3.604 |
52 Te
Lα 3.769 |
53 I
Lα 3.937 |
54 Xe
Lα 4.109 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
55 Cs
Lα 4.286
|
56 Ba
Lα 4.465
|
{57-70} |
71 Lu
Lα 7.654
M 1.581
|
72 Hf
Lα 7.898
M 1.644
|
73 Ta
Lα 8.145
M 1.709
|
74 W
M 1.774
|
75 Re
M 1.842
|
76 Os
M 1.914
|
77 Ir
M 1.977
|
78 Pt
M 2.048
|
79 Au
M 2.120
|
80 Hg
M 2.195
|
81 Tl
M 2.267
|
82 Pb
M 2.342
|
83 Bi
M 2.419
|
84 Po
|
85 At
|
86 Rn
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
87 Fr |
88 Ra |
[89-102] |
103 Lr
|
104 Rf
|
105 Db
|
106 Sg
|
107 Bh
|
108 Hs
|
109 Mt
|
110 Uun
|
111 Uuu
|
112 Uub
|
|
114 Uuq
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
{lanthanides} {57-70} |
57 La
Lα 4.650
|
58 Ce
Lα 4.839
|
59 Pr
Lα 5.033
M 0.929 |
60 Nd
Lα 5.229
M 0.978 |
61 Pm
Lα 5.432
|
62 Sm
Lα 5.635
M 1.081 |
63 Eu
Lα 5.845
M 1.131
|
64 Gd
Lα 6.056
M 1.185
|
65 Tb
Lα 6.272
M 1.240
|
66 Dy
Lα 6.494
M 1.293 |
67 Ho
Lα 6.719
M 1.347 |
68 Er
Lα 6.947
M 1.405 |
69 Th
Lα 7.179
M 1.462 |
70 Yb
Lα 7.414
M 1.521 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
{actinides} [89-102] |
89 Ac
|
90 Th
M 2.991 |
91 Pa
M 3.077 |
92 U
M 3.164 |
93 Np
M 3.260 |
94 Pu
M 3.348 |
95 Am
M 3.437 |
96 Cm
M 3.539 |
97 Bk
M 3.634 |
98 Cf
M 3.731 |
99 Es
|
100 Fm
|
101 Md
|
102 No
|
|
|
|
Table 4610d. Periodic Table showing typical choices of X-ray lines for EDS operation at accelerating voltage of 5 keV (U > 1.1 for Ec ≤ 4.5 keV). |
1 |
2 |
|
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
|
|
|
1 H |
|
2 He |
|
|
|
|
|
|
|
|
|
3 Li
|
4 Be
Kα 0.110 |
|
5 B
Kα 0.183 |
6 C
Kα 0.277 |
7 N
Kα 0.392 |
8 O
Kα 0.525 |
9 F
Kα 0.677 |
10 Ne
Kα 0.848 |
|
|
You can download the excel file in order to highlight the elements in your EDS profile. |
|
|
|
|
|
|
11 Na
Kα 1.041
|
12 Mg
Kα 1.253 |
|
Not detectable |
|
|
K-shell |
|
|
|
|
L-shell |
|
|
M-shell, but are not sufficiently excited to be practically measured. |
|
|
|
|
13 Al
Kα 1.486 |
14 Si
Kα 1.739 |
15 P
Kα 2.013 |
16 S
Kα 2.307 |
17 Cl
Kα 2.621 |
18 Ar
Kα 2.957 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
19 K
Kα 3.312
|
20 Ca
Kα 3.690 |
|
21 Sc
Kα 4.088
|
22 Ti
Lα 0.452 |
23 V
Lα 0.511 |
24 Cr
Lα 0.573 |
25 Mn
Lα 0.637 |
26 Fe
Lα 0.705 |
27 Co
Lα 0.776 |
28 Ni
Lα 0.851 |
29 Cu
Lα 0.930 |
30 Zn
Lα 1.012 |
31 Ga
Lα 1.098 |
32 Ge
Lα 1.188 |
33 As
Lα 1.282 |
34 Se
Lα 1.379 |
35 Br
Lα 1.480 |
36 Kr
Lα 1.586 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
37 Rb
Lα 1.694
|
38 Sr
Lα 1.806 |
|
39 Y
Lα 1.922 |
40 Zr
Lα 2.042 |
41 Nb
Lα 2.166 |
42 Mo
Lα 2.293 |
43 Tc
Lα 2.424 |
44 Ru
Lα 2.558 |
45 Rh
Lα 2.696 |
46 Pd
Lα 2.838 |
47 Ag
Lα 2.984 |
48 Cd
Lα 3.133 |
49 In
Lα 3.286 |
50 Sn
Lα 3.443 |
51 Sb
Lα 3.604 |
52 Te |
53 I |
54 Xe |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
55Cs |
56 Ba |
{57-70} |
71 Lu
M 1.581 |
72 Hf
M 1.644 |
73 Ta
M 1.709 |
74 W
M 1.774 |
75 Re
M 1.842 |
76 Os
M 1.914 |
77 Ir
M 1.977 |
78 Pt
M 2.048 |
79 Au
M 2.120 |
80 Hg
M 2.195 |
81 Tl
M 2.267 |
82 Pb
M 2.342 |
83 Bi
M 2.419 |
84 Po
|
85 At
|
86 Rn
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
87 Fr |
88 Ra |
[89-102] |
103 Lr
|
104 Rf
|
105 Db
|
106 Sg
|
107 Bh
|
108 Hs
|
109 Mt
|
110 Uun
|
111 Uuu
|
112 Uub
|
|
114 Uuq
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
{lanthanides} {57-70} |
57 La |
58 Ce
M 0.883 |
59 Pr
M 0.929 |
60 Nd
M 0.978 |
61 Pm
|
62 Sm
M 1.081 |
63 Eu
M 1.131
|
64 Gd
M 1.185
|
65 Tb
M 1.240 |
66 Dy
M 1.293 |
67 Ho
M 1.347 |
68 Er
M 1.405 |
69 Th
M 1.462 |
70 Yb
M 1.521 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
{actinides} [89-102] |
89 Ac
|
90 Th
M 2.991 |
91 Pa
M 3.077 |
92 U
M 3.164 |
93 Np
M 3.260 |
94 Pu
M 3.348 |
95 Am
M 3.437 |
96 Cm
M 3.539 |
97 Bk |
98 Cf |
99 Es |
100 Fm |
101 Md |
102 No |
|
|
|
Table 4610e. Periodic Table showing typical choices of X-ray lines for EDS operation at accelerating voltage of 2.5 keV (U > 1.2 for Ec ≤ 2.2 keV). |
1 |
2 |
|
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
|
|
|
1 H |
|
2 He |
|
|
|
|
|
|
|
|
|
3 Li
|
4 Be
Kα 0.110 |
|
5 B
Kα 0.183 |
6 C
Kα 0.277 |
7 N
Kα 0.392 |
8 O
Kα 0.525 |
9 F
Kα 0.677 |
10 Ne
Kα 0.848 |
|
|
You can download the excel file in order to highlight the elements in your EDS profile. |
|
|
|
|
|
|
11 Na
Kα 1.041
|
12 Mg
Kα 1.253 |
|
Not detectable |
|
|
K-shell |
|
|
|
|
L-shell |
|
|
M-shell, but are not sufficiently excited to be practically measured. |
|
|
|
|
13 Al
Kα 1.486 |
14 Si
Kα 1.739 |
15 P
Kα 2.013 |
16 S |
17 Cl |
18 Ar |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
19 K
|
20 Ca
Lα
0.341 |
|
21 Sc
Lα 0.395 |
22 Ti
Lα 0.452 |
23 V
Lα 0.511 |
24 Cr
Lα 0.573 |
25 Mn
Lα 0.637 |
26 Fe
Lα 0.705 |
27 Co
Lα 0.776 |
28 Ni
Lα 0.851 |
29 Cu
Lα 0.930 |
30 Zn
Lα 1.012 |
31 Ga
Lα 1.098 |
32 Ge
Lα 1.188 |
33 As
Lα 1.282 |
34 Se
Lα 1.379 |
35 Br
Lα 1.480 |
36 Kr
Lα 1.586 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
37 Rb
Lα 1.694 |
38 Sr
Lα 1.806 |
|
39 Y |
40 Zr |
41 Nb |
42 Mo |
43 Tc |
44 Ru |
45 Rh |
46 Pd |
47 Ag
|
48 Cd |
49 In |
50 Sn |
51 Sb |
52 Te |
53 I |
54 Xe |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
55 Cs |
56 Ba |
{57-70} |
71 Lu
M 1.581
|
72 Hf
M 1.644
|
73 Ta
M 1.709
|
74 W
M 1.774
|
75 Re
M 1.842
|
76 Os |
77 Ir |
78 Pt |
79 Au |
80 Hg |
81 Tl |
82 Pb |
83 Bi |
84 Po |
85 At |
86 Rn |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
87 Fr |
88 Ra |
[89-102] |
103 Lr
|
104 Rf
|
105 Db
|
106 Sg
|
107 Bh
|
108 Hs
|
109 Mt
|
110 Uun
|
111 Uuu
|
112 Uub
|
|
114 Uuq
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
{lanthanides} {57-70} |
57 La |
58 Ce
M 0.883 |
59 Pr
M 0.929 |
60 Nd
M 0.978 |
61 Pm
|
62 Sm
M 1.081 |
63 Eu
M 1.131
|
64 Gd
M 1.185 |
65 Tb
M 1.240 |
66 Dy
M 1.293 |
67 Ho
M 1.347 |
68 Er
M 1.405 |
69 Th
M 1.462 |
70 Yb
M 1.521 |
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{actinides} [89-102] |
89 Ac |
90 Th |
91 Pa |
92 U |
93 Np |
94 Pu |
95 Am |
96 Cm |
97 Bk |
98 Cf |
99 Es |
100 Fm |
101 Md |
102 No |
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[1] R. Castaing, A. Guinier, Proceedings 1st International Congress on Electron Microscopy, Delft, 1950, p. 60.
[2] Edward D. Boyes, Analytical potential of EDS at low voltages, Mikrochim. Acta 138, 225-234 (2002).
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