modification of si nanocrystallites in sio 2 matrix by swift heavy ion irradiation
DESCRIPTION
Modification of Si nanocrystallites in SiO 2 matrix by swift heavy ion irradiation By: V. E. Thelelo & A. Rossouw In co-operation with, University of Fort Hare & Stellenbosch University Supervised By: N.S.Kirilkin, V.A.Skuratov Joint Institute for Nuclear Research, Dubna, Russia. - PowerPoint PPT PresentationTRANSCRIPT
Modification of Si nanocrystallites in SiO2 matrixby swift heavy ion irradiation
By: V. E. Thelelo & A. Rossouw
In co-operation with,University of Fort Hare & Stellenbosch University
Supervised By:
N.S.Kirilkin, V.A.SkuratovJoint Institute for Nuclear Research, Dubna, Russia
Brief project overview
The irradiation testing of nuclear ceramics and oxides with heavy ions of fission fragment energy
Our irradiation testing experiments will be focused on study of:
– correlation between surface and material bulk radiation damage induced by heavy ions with energies above 1 MeV/atomic mass unit (amu).
– temperature dependence of swift heavy ion-induced phase transformations and dense ionization effect on pre-existing defect structure in irradiating materials.
The project fulfillment allows us to acquire new knowledge concerning evolution of defect structure in nuclear ceramics under dense electronic excitations simulating the fission fragment impact.
G. Schiwietz et al. NIMB 226 (2004) 683
The source of structural changes in tracks of high energy (E > 1 MeV/amu) heavy ions is a huge energy deposition (Se tens keV/nm) in electron subsystem of irradiating material
SHI cause exotic effects in different classes of materials which cannot be generated by any other means.
Irradiation with swift heavy ions (SHI)
SiO2 layers with variable NC concentration
1. Deposition of SiO2 and Si on Si substrate from two sources separated by distance of 100 mm 2. dSiO2 = 400 - 1000 nm3. Si content in oxide: 5 - 90 vol.%4. Annealing: 1140оС, 40 min, N2
NC size: 3 – 5 nm
Si
Ordered arrays of Si nanocrystals in SiO2: structural, optical and propertiesOrdered arrays of Si nanocrystals in SiO2: structural, optical and properties
The ordering of composites under high-energy ion irradiation and formation of elongated particles (up to 250 nm length with diameter 3-5 nm) is known for metal nanoparticales in SiO2
Pt in SiO2
185 MeV AuNIM B 266 (2008), 3158
Kr, 90 MeV, 1012 cm-2
Formation of the ordered NC distribution
substrate
surface
Ion pass
30 nm
20 nm
Irradiated NC-SiO2 layer (37 % Si)
Kr, 90 MeV, 1012 cm-2 non-irradiated layer
HREM cross sectional images for the Si NCs in irradiated layer
Atomic planes of NCs in the irradiated samples are oriented along the ion tracks
500 550 600 650 700 750 800 850 9000
50
100
150
200
250
300
350
X, %: 57 51 40 33 26 22
PL in
tens
ity, a
rb. u
nits
Wavelength, nm500 550 600 650 700 750 800 850 9000
50
100
150
200
250
300
350
X, %:
51 40 33 26 22 18 14.5
PL in
tens
ity, a
rb. u
nits
Wavelength, nm
Bi, 670 MeV , ex. = 488 nm, Ar laser
Initial 1x1012 cm-2 8x1012 cm-2
500 550 600 650 700 750 800 850 9000
5
10
15
20
25
30SiO-3
X, vol.% 57 51 40 33 26 22 18
PL in
tens
ity, a
rb. u
nits
Wavelength, nm
Photoluminescence of irradiated layer
10 20 30 40 50 600
50
100
150
200
250
300
350
I PL, a
rb.u
nits
X, vol %
initial
Bi, 1012 cm-2
Bi, 8.1x1012 cm-2
Photoluminescence of 670 MeV Bi ion irradiated layer
Experimental Setup
Spectrometer
Diod380nm
Nc Si specimen
SpectrometerANDOR iDUS
1. Diod with 380nm wavelength produces excitation of Nc Si
2. Nc Si specimen emit light
3. Spectrometer register this light and cuts off signal less than 550nm wavelength
Extra Si concentration
1 2 3 654
5% 90%
Max effect for points 3 and 4
PL intensity of initial Si NCs as a function of Si concentration
Acknowledgments
Dr. N. M. Jacobs Prof. M. L. Lekala Dr. V. A. Skuratov Mr. N. S. Kirilkin JINR UFH US And everyone else involved in making this practice
possible.
Thank you for your attention!