Ion Implantation and Annealing of Crystalline Oxides and Ceramic Materials

The University of Tennessee, Knoxville

By : Younes Sina & Uk Huh

C.W. WHITE, L.A. BOATNER, P.S. SKLAD, C.J. McHARGUE, J. RANKIN , G.C. FARLOW and M.J. AZIZ Oak Ridge Natronal Laboratory, Oak Ridge, TN 37831, USA

Material

CaTiO3

SrTiO3

α-Al2O3

Fe implanted α-Al2O3

The unit cell of SrTiO3 consists of a central Ti4+-ion, which is octahedrally coordinated by 6 O2--ions. At the corners of the cube Sr2+-ions are situated

Ti

O

Sr

SrTiO3

Space group: Pm-3m Number: 221 Pearson symbol: cP5 Unit cell dimensions: a = 3.795 Å Atomic positions: Ti  at (0, 0, 0) Ca  at (1/2, 1/2, 1/2) O  at (1/2, 0, 0)

CaTiO3

a≈c

Orthorhombic structure

Al

O

Al2O3

Pb (540 keV, 1x1015 /cm2)

CaTiO3

Crystal Damage

Annealing in air@ 270- 550 ⁰C

TEM

Rutherford Back Scattering(RBS)2 Mev He+

Pb (540 keV, 1x1015 /cm2)

SrTiO3

Crystal Damage

Annealing in air@ 270- 550 ⁰CFrom few minutes to many hours

Rutherford Back Scattering(RBS)2 Mev He+

100110

111

2Al (90 keV, 4x1016 /cm2)& 3 O(55 keV, 6x1016 /cm2)

Al2O3

Crystal Damage

Annealing in air@ 800- 1200 ⁰C

Rutherford Back Scattering(RBS)2 Mev He+

TEM

Fe (160 keV, 4x1016 /cm2 ,L N2)

Al2O3

Crystal Damage

Annealing in Ar@ 800 & 960 ⁰C

Rutherford Back Scattering(RBS)2 Mev He+

TEM

implanted by: Pb (540 keV, 1x1015 /cm2)SrTiO3

100

Liquid Nitrogen

Ion channeling before annealing

Ion channeling after annealing (400 ° C/30 min)

Implanted Pb is substitutional in the lattice after annealing

Epitaxial Recrystallization

Depth of the amorphous region: 1800 Å

implanted by: Pb (540 keV, 1x1015 /cm2)(100) SrTiO3

Ion channeling after annealing 302 ° C/45 min

Epitaxial Recrystallization

Depth of the amorphous region after annealing: 800 Å

Crystallized depth vs. annealing time

implanted by: Pb (540 keV, 1x1015 /cm2)(100) SrTiO3

302 ° C

Induction period

Slope 0.91 Å/s

(100) SrTiO3

implanted by: Pb (540 keV, 1x1015 /cm2)

350 ° C

325 ° C

302 ° C

0.91 Å/s

1.48 Å/s

3 Å/s

Increasing T Increasing Slope

The induction period decreases markedly as the annealing temperature increases.

Crystallization of amorphous SrTiO3 Amorphous →Crystal Transformation

Kinetics of crystallization of Pb- implanted (100) SrTiO3

V(T)=V0e-Q/RT

V00.05 cm/s & Q0.77 eV

Q0.77 eV

Pb (540 keV, 1x1015 /cm2)

SrTiO3

110

111

100

Growth in the (110) direction almost is the same of (100)

Growth in the (111) direction is not linear with time

Crystallization kinetics are not strongly affected by Pb concentration

CaTiO3-High symmetry face

implanted by: Pb (540 keV, 1x1015 /cm2)

Ion channeling spectra after annealing at 425 ° C/15 h in air

Cross section micrograph of Pb (250 keV, 4x1015 /cm2) implanted CaTiO3

implanted by: Pb (250 keV, 4x1015 /cm2)

CaTiO3 (High symmetry face)

Ion channeling spectra in the as-implanted state

Ion channeling spectra after annealing at 500 ° C/h in air

Recrystallization of amorphous CaTiO3 Amorphous →Crystal Transformation

Kinetics of crystallization of Pb- implanted CaTiO3

Q1.3 eV

Q3.76 eV

Crystallization of amorphous Al2O3 Amorphous →Crystal Transformation

1600Å

A few minutes at 800 ° C for 1600 Å γ→α

100 hr at 800 ° C For 800 Å γ→α

γ→α stops before reaching the surface

TEM cross section of →α transition in Al2O3

Annealing at 960 ° C/ 90 min

Crystallization of amorphous Al2O3

Amorphous →Crystal Transformation

implanted by: 2 Al (90 keV, 4x1016 /cm2) & 3 O (55 keV, 6x1016 /cm2) at liquid nitrogen

960 ° C/45 min

Kinetics of →α transition in Al2O3

Temperature dependence of the →α interface velocity in Al2O3

Process Energy/Activation Energy (eV)

γ-Al2O3→α-Al2O3 3.6

Al-O bond energy 4.7

Bulk diffusion of O ions in Single crystal α-Al2O3

6.6

Bulk diffusion of O ions in polycrystalline α-Al2O3

4.8

Bulk diffusion of Al ions in α-Al2O3

5

A micrograph of Fe- implanted Al2O3 (LN2) after annealing at 960 ° C/45 min

Annealing of Fe (160 keV, 4x1016 /cm2 ,L N2) implanted α- Al2O3

960 ° C/45 min

As implanted

Al2O3Fe

Crystal Damage

1500 Å

Fe

Annealing

Fe toward the surface

Crystallization behavior (amorphous →→α ) remains the same but the kinetics of /α

transformation increase by the presence of Fe

The presence of Fe in the amorphous film increases the crystallization kinetics at least by

a factor of 4

Material Direction of the study

Implantation detail

Annealingdetail

Length of Amorphous region

CaTiO3 Low Symmetry (a or c- axis)High symmetry( b- axis)

LN2,Pb 540,250 keV, 4x1015 ,1x1015/cm2

Air500°C/1 hr< 500°C

1100 Å1800 Å

SrTiO3 (100), (110),(111) direction

LN2Pb 540 keV, 1x1015 /cm2

Air400 °C/30 min 302 °C/45 min 305°C325°C

1800 Å

α-Al2O3 C-axis oriented LN22Al (90 keV, 4x1016 /cm2)& 3 O(55 keV, 6x1016 /cm2)

800°C960°C/90 min950°C/45 min

1600 Å

Fe implanted α-Al2O3

C-axis oriented LN2Fe 160 keV, 4x1016 /cm2

Ar800-1200 °C

1500 Å

Thank you