E.M. Hunt , J.M. Hampikian , D.B. Poker , N.D. Evans

Ion implantation induced formation of aluminum nanoparticles in

alumina via reduction

Presentation by: Younes Sina

Colloid formation mechanism:

Ion implantation

Precipitation of the implanted ion(s) & formation of nanocrystals at high temperature during implantation or post-implantation annealing Irradiation –induced dissociation of the host material

Metal particle formation due to electron or neutron irradiation of alkali halides (LiF), alkaline earth fluorides (CaF2), and some oxides (Lithia LiO, Alumina Al2O3)

LiF Li (colloid)slightly elevated temperature

eAl2O3

14 MeVAl

Al2O3thin film

1 MeV

elevated temperature

Al LiO2 Li (colloid)

1 MeVe

e

e

Removing residual polishing damage

1500 ⁰C

80 h

Vacuum

0.5-2 mA

1x10-7 Torr

50 keV

70 keV

5x1016 Ca+/cm2

Vacuum

0.5-2 mA

1x10-7

150 keV

5x1016 Y+/cm2

Equipments used for the results:

Knoop microhardness

Rutherford backscattering

Differential optical absorption

TEM

Energy Dispersive X-ray Spectroscopy (EDS)

High Resolution Parallel detector Electron Energy Loss Spectroscopy (PEELS)

Energy Filtered TEM (EFTEM)

Ca 14%

Y 9%

Ca 10%

50 keV 70 keV ~30nm ~40 nm

~41 nm

150 keV

Experimental implanted ion range

Amorphous layer =120 nm

5x1016 Ca+/cm25x1016 Ca+/cm2

5x1016 Y+/cm2

Experimental im

planted ion range

Experimental im

planted ion range

Experimental im

planted ion range

The implanted ion range predictions made by PROFILE simulation program were reasonably accurate.

Rutherford backscattering

Knoop microhardness

<1

Ca 50

Ca 70

Y 1 50

Implanted hardness

Unimplanted hardness

Differential optical absorption by High Resolution TEM

Optical absorption spectra from the implanted samples, showing the absorption feature caused by the presence of metallic colloids dispersed in the matrix.

?

?

TEM

TEM micrograph of 150 keV Y+ implantation

TEM micrograph of 50 keV Ca+ implantation

TEM micrograph of 70 keV Ca+ implantation

10.7±1.8 nm

8.8±1.2 nm

7.5±1.4 nm

0.410±0.004 nm

0.413±0.004 nm

0.409±0.004 nm

Lattice parameter of pure FCC aluminum= 0.40497 nm

From: High Resolution Parallel detector Electron Energy Loss Spectroscopy (PEELS)

Energy loss spectra from 150 keV Y+

Energy loss spectra from 70 keV Ca+

Alumina Plasmon loss @ 25 eVMetallic aluminum Plasmon @ 15 eV

Energy Dispersive X-ray Spectroscopy (EDS)

Chemical analysis of the 3 samples using Energy Dispersive X-ray Spectroscopy (EDS) indicates that the particles are aluminum-rich with respect to the surrounding matrix.

There is no graph or more information about EDS !!!!!??????

Energy Filtered TEM (EFTEM) micrographs of the 50-keV Ca+ implantation

15-eV-loss image

25-eV-loss image

Elemental map of oxygen from an adjacent region

particles in the implanted areas appear bright

particles in the implanted areas appear dark

particles are oxygen deficient with respect to the surrounding matrix

This set of images confirms that the particles contain metallic aluminum

ωp =Plasmon frequency of the bulk metal

Wavelength at maximum absorption (λ peak) due to colloidal metal particles

width of absorption peak:

ω0 =Collision frequency of the electron in the metal

Mie theory for absorption by small metal particles

)2 200

(2 2/1

np

peak

c

)2(2

4 2

0020 np

c

From Eq. (1):

λ peak=218 nm using

ε₀=1 n0 =1.76ω₀ =2.309x1016 s-1

Implantation of ions into the matrix materials will increase the index of refraction (n0) in the surface region

Increase of n0 =1.76 to 1.96 results in a calculated λ peak=240 nm

Theoretical calculation:

Alumina is known to be difficult to fully amorphize except with large doses of heavy ions and/or implantation at reduced

temperatures

Zn & Zr (strongly oxidizing elements) produce buried amorphous layers in alumina with much greater accelerating energies or a much higher fluence.

Different behavior of Ca

?

Reduction of target cation with ion (that is more oxygen reactive)

2 Y+ Al2O3 2 Al+ Y2O3

3 Ca+ Al2O3 2Al+ 3CaO

G<0

G<0

Kurdistan, Iran