V2O and V3O DEFECTS IN SILICON: FTIR STUDIES

Leonid Murin 1,2

11 Joint Institute of Solid State and Joint Institute of Solid State and Semiconductor Physics, Minsk, BelarusSemiconductor Physics, Minsk, Belarus

22 Oslo University, Centre for Materials Science Oslo University, Centre for Materials Science

and Nanotechnology, Oslo, Norwayand Nanotechnology, Oslo, Norway

OUTLINE

• What we know• V2O and V3O formation upon irradiation at RT

• V2O and V3O formation upon annealing• Comparison of electron and neutron irradiation• LVMs of excited states

BACKGROUND - WHAT IS KNOWN

V2O defect N.V.Sarlis, C.A. Londos, and L.G. Fytros (J. Appl. Phys. 81 (1997) 1645) have assigned the band at 839 cm-1 (RT position) to this defect (neutron irradiated Cz-Si)J.L. Lindström, L.I. Murin, V.P. Markevich, T. Hallberg, and B.G. Svensson (Physica B 273-274 (1999) 291) have assigned the band at 833.4 cm-1 (LT position, 826 cm-1 – RT position ) to V2O (electron irradiated Cz-Si)

V3O defect

Y.H Lee, J.C. Corelli and J.W. Corbett (Phys. Lett. 60A (1977) 55) assigned the band at 889 cm-1 (RT position) to this defect

C.A. Londos, N.V.Sarlis, and L.G. Fytros (J. Appl. Phys. 81 (1999) 1645) have assigned a shoulder (at 884 cm-1 (RT position)) of the 889 cm-1 band (VO2) to V3O (neutron irradiated Cz-Si)

Formation of V2O and V3O

1. RT irradiation

V + Oi VO (1)V + VO V2O (2)V + V2O V3O (3)

The V capture radii appear to be very similar for reactions (1) and (2). So, at electron irradiation doses when [VO] does not exceed 3-5% of [Oi], the V2O line (833.4 cm-1) is practically not detectable (it is masked by the Si isotope lines of VO, see Fig 1a). However, at higher doses, when [VO] increases up to 10-20% of [Oi], the appearance of V2O is clearly seen (Fig. 1b, the Si isotope lines are taken into account for all the defects, not shown). Along with the main V2O band (at 833.4 cm-1), a weaker band at 837 cm-1 is developing. Besides, two weak lines, at 842.4 and 848.6 cm-1, start to appear as well. These are suggested to arise from a V3O defect.

820 825 830 835 840 845 8500.0

0.1

0.2

0.3

0.4

0.5

0.6 VO

VnOm Fig 1a

32

1

T = 15 K

n-type Cz-Si, [P] = 5x1013 cm-3

[Oi] = 8.3x1017 cm-3, [Cs] = 5x1016 cm-3

RT irradiation e- 10 MeV 3x1017 cm-3

1 - 835.8 cm-1 (28Si-O-28Si)

2 - 834.2 cm-1 (29Si-O-28Si)

3 - 832.7 cm-1 (30Si-O-28Si)

Abs

orpt

ion

coef

ficie

nt, c

m-1

Wavenumber, cm-1

820 825 830 835 840 845 850

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

VnOm Fig 1b

T = 15 K

76

543

2

1

n-type Cz-Si, [P] = 4x1015 cm-3

[Oi] = 7.5x1017 cm-3, [Cs] = 1x1016 cm-3

RT irradiation e- 10 MeV 4x1018 cm-3

1 - VO 835.8 cm-1 (28Si-O-28Si)

2 - VO 834.2 cm-1 (29Si-O-28Si)

3 - VO 832.7 cm-1 (30Si-O-28Si)

4 - V2O0 833.5 cm-1

5 - V2O- 837.0 cm-1

6 - V3O0 842.4 cm-1

7 - V3O- 848.6 cm-1

A

bsor

ptio

n co

effic

ient

, cm

-1

Wavenumber, cm-1

Formation of V2O and V3O

2. Annealing

Migration of V2 that occurs at T > 150 C results in a further development of VnO centres (Fig. 2a,b) via the V2 interaction with Oi, VO and other defects

V2 + Oi V2O (4)

V2 + VO V3O (5)

V2 + V2O V4O (6)

820 825 830 835 840 845 850

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

VnOm Fig 2a

n-type Cz-Si, [P] = 4x1015 cm-3

[Oi] = 7.5x1017 cm-3, [Cs] = 1x1016 cm-3

RT irradiation e- 10 MeV 4x1018 cm-3

+ 170 C 650 h

1 - VO 835.8 cm-1 (28Si-O-28Si)

2 - VO 834.2 cm-1 (29Si-O-28Si)

3 - VO 832.7 cm-1 (30Si-O-28Si)

4 - V2O0 833.5 cm-1

5 - (V2O- + V4O) 837.0 cm-1

6 - V3O0 842.4 cm-1

7 - V3O- 848.6 cm-1

765

4

3 2

1

T = 15 K

Abs

orpt

ion

coef

ficie

nt, c

m-1

Wavenumber, cm-1

800 810 820 830 840 850 860

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8VnOm Fig 2b

n-type Cz-Si, [P] = 4x1015 cm-3

[Oi] = 7.5x1017 cm-3, [Cs] = 1x1016 cm-3

RT irradiation e- 10 MeV 4x1018 cm-3

1 - VO 830.3 cm-1 (28Si-O-28Si)

2 - VO 828.7 cm-1 (29Si-O-28Si)

3 - VO 827.2 cm-1 (30Si-O-28Si)

4 - V2O 825.7 cm-1

5 - V4O 834.6 cm-1

6 - V3O 839.1 cm-1

T = 300 K

65

4

3

2

1

A

bsor

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effic

ient

, cm

-1

Wavenumber, cm-1

In electron-irradiated Cz-Si the interstitial oxygen appears to be a dominant trap of mobile divacancies. In crystals with different doping levels and irradiated with different doses, the main part of V2 disappear during isochronal anneal in the same temperature region

50 100 150 200 250 3000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0Fig 2c.V2 elimination upon 30 min isochronal anneal

4 MeV 3*1016 cm-2, [Oi] = 7.5x1017 cm-3, [P] = 4*1015 cm-3

10 MeV 3*1017 cm-2, [Oi] =1.0x1018 cm-3, [P] = 8*1014 cm-3

2 MeV 7*1017 cm-2, [Oi] = 6.0x1017 cm-3, [As] = 5*1016 cm-3

10 MeV 4*1018 cm-2, [Oi] =1.0x1018 cm-3, [P] = 4*1013 cm-3

2 MeV 1.6*1018 cm-2, [18Oi] = 1.5x1018, cm-3 [P] = 2*1016 cm-3

x 0.5

2767

ban

d A

C, c

m-1

Temperature, C

50 100 150 200 250 300

0.0

0.2

0.4

0.6

0.8

1.0

4 MeV 3*1016 cm-2, [Oi] = 7.5x1017 cm-3, [P] = 4*1015 cm-3

10 MeV 3*1017 cm-2, [Oi] =1.0x1018 cm-3, [P] = 8*1014 cm-3

2 MeV 7*1017 cm-2, [Oi] = 6.0x1017 cm-3, [As] = 5*1016 cm-3

10 MeV 4*1018 cm-2, [Oi] =1.0x1018 cm-3, [P] = 4*1013 cm-3

2 MeV 1.6*1018 cm-2, [18Oi] = 1.5x1018, cm-3 [P] = 2*1016 cm-3

V2 elimination upon 30 min isochronal annealFig 2d

U

nann

eale

d fra

ctio

n of

276

7

Temperature, C

0 100 200 300 400 500 6000.01

0.1

1VnOm Fig 3a Isothermal anneals at 170, 190 and 219 C

n-type Cz-Si, [P] = 4x1015 cm-3

[Oi] = 7.5x1017 cm-3, [Cs] = 1x1016 cm-3

RT irradiation e- 10 MeV 4x1018 cm-3

= 4.4 h

= 33.8 h

= 160 h

170 C 190 C 219 C

Una

nnea

led

fract

ion

2767

(t)/

2767

(0)

Time, h

1.8 1.9 2.0 2.1 2.2 2.3

103

104

105

106VnOm Fig 3b

275 C

170 C

Temperature dependence of V2 life-time

[Oi] = 6x1017 cm-3

[VO] = 1.3x1017 cm-3

= -1exp(E/kT)

E = 1.40 eV

= 1.6*1010 s-1

, s

1000/T, K

0 20 40 60 80 1000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8VnOm Fig 4a Removal of Oi upon V2O generation

Anneal at 190 C

x 2

x 0.2

-N

O,1

017 c

m-3

2767 cm-1 (V2)

833.5 cm-1 (V2O)

-1107*3.14*1017 cm-3

Abs

orpt

ion

coef

ficie

nt, c

m-1

Time, h

In samples with a high V2 concentration, a noticeable decrease in [Oi] is observed (Fig. 4a), in accordance with reaction (4).

0 20 40 60 80 100

0.00

0.05

0.10

0.15

0.20

0.25

VnOm Fig 4b Removal of VO upon V3O generation

Tanneal = 190 C

x 0.05

2767 cm-1 (V2)

842.4 cm-1 (V3O)

835.8 cm-1, - (VO)

Abs

orpt

ion

coef

ficie

nt, c

m-1

Time, h

Due to occurrence of reaction (5) the concentration of A-centres is decreasing as well

However, reaction (5) can not account for the observed overall generation of V3O, especially in samples with relatively low VO concentration. It is very likely, that V3 has the same migration ability as V2, and V3O can be also generated via the reaction

V3 + Oi V3O (7)

175 200 225 250 275 3000.0

0.2

0.4

0.6

0.8Cz-Si, 5 MeV neutron irradiation, 7.5x1016 cm-2

V2O and V3O formation upon V2 elimination during 30 min isochronal anneal

2767 cm-1 band (V2)

833.4 cm-1 band (V2O)

842.4 cm-1 band (V3O)

x 0.2

AC

, cm

-1

Temperature, C

820 825 830 835 840 845 850

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

3

2

1

1 - n 5 MeV 1x1017 cm-2

2 - e- 10 MeV 3x1017 cm-2

3 - e- 2 MeV 1x1018 cm-2 V3O

V2ODiffererence 275 C 30 min - irr Cz-Si carbon-rich

x3

A

C, c

m-1

WN, cm-1

Note

It is interesting to note that the V2H and V3H defects detected in EPR and FTIR studies (P. Stallinga et al, PRB 58, 3842, (1998)) are also not distinguished in their annealing behaviour. According to the latter paper the ratio of V3 and V2 production rates is about 0.5 in proton implanted Si. In the case of 10 MeV electron irradiation, this ratio is about 0.2-0.3 (our estimations), but for neutron irradiation it increases again up to 0.5.

820 840 860 880 900

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

VO2

VOT = 15 K

5

4321

Cz-Si, [Oi] = 1x1018, [Cs] = 5x1016, [P] = 5x1013 cm-3

10 MeV electron irr 4x1018 cm-2, Tirr = 100-150 C30 min anneal at: 1 - 300 C 2 - 325 C 3 - 350 C 4 - 375 C 5 - 400 C

A

bsor

ptio

n co

effic

ient

, cm

-1

Wavenumber, cm-1

820 825 830 835 840 845 850 855 860

0.00

0.25

0.50

0.75

1.00

1.25 V4O?

V2O2

V3O2-

V3O20

V3O-

V3O0

300 C 325 C 350 C 375 C 400 C

Abs

orpt

ion

coef

ficie

nt, c

m-1

Wavenumber, cm-1

50 100 150 200 250 300 350 400

0.0

0.2

0.4

0.6

0.8

1.0VnOm development upon 30 min isochronal anneal

Cz-Si, [Oi] = 1x1018 cm-3, [Cs] = 5x1016 cm-3, [P] = 5x1013 cm-3

10 MeV electron irr 4x1018 cm-2, Tirr = 100-150 C

x0.25

x0.5

2767 V2 835.8 VO 833.5 V2O 829.4 V2O2

837.0 V2Oex + V4O?

842.4 V3O 844.1 V3O2

Abs

orpt

ion

coef

icie

nt, c

m-1

Temperature, C

820 830 840 850 860 870 880 890

-0.03

-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

Excited states of V2O and V3O

T = 15 K n-type Cz-Si, [P] = 4x1015 cm-3, [Oi] = 7x1017 cm-3,

RT irr. e- 10 MeV 4x1018 cm-3 + 170 C 650 hDifferential spectrum: Ge-filter - without

1 - V2O0

2 - VO0

3 - V2O-

4 - V3O0

5 - (V3O-

6 - VO-

65

4

3

2

1

A

bsor

ptio

n co

effic

ient

, cm

-1

Wavenumber, cm-1

820 830 840 850 860

0.0

0.1

0.2

0.3

0.4

0.5

T = 15 K

V3O2 excited state

V3O2-

V3O20

3

2

1

Cz-Si, [Oi] = 1x1018 cm-3,

[Cs] = 5x1016 cm-3,

[P] = 5x1013 cm-3

10 MeV e- irr 4x1018 cm-2

30 min anneal at 375 C1 - normal spectrum2 - Ge filter3 - difference

A

bsor

ptio

n co

effic

ient

, cm

-1

Wavenumber, cm-1