1. Z.Werner,M.Pisarek,M.Barlak,R.Ratajczak,W.Starosta,J.Piekoszewski,W.Szymczyk,R.Grtzschel
Chemical effects in Zr- and Co-implanted sapphire
Younes Sina

2. 5 1017 Co+& Zr+/cm2
Annealing in vacuum for 1 hr
Al2O3
300 m thick
200,400,600,800C
5 1017 Co+& Zr+/cm2
Annealing in vacuum for 5 hr
XPS
XRD RBS
Covering with thin graphite layer
800C
5 1017 Co+& Zr+/cm2
Annealing in argon gas for 1 hr
1400C
Room temperature
65 keV
3. Based on the calculation
2Al2O3+3ZrZrO2+4Al
G298.15 =39.36 kJ/mol
2Al2O3+3ZrZrO2+4Al
G298.15 =-546.24 kJ/mol
=3[-546.24-(-559.36)]=
Al2O3+3CoCoO+2Al
G298.15 =-71.12 kJ/mol
=3[-71.12-(-384.16)]=
Al2O3+3CoCoO+2Al
G298.15 =939.12 kJ/mol
Al2O3+Co Al2O3+ Co
G298.15 =-384.16 kJ/mol
The above reactions do not tell much about the possibility of forming ternary compounds like cobalt spinel CoAl2O4.
2Al2O3+ZrAl2O3+Zr
G298.15 =-559.36 kJ/mol
Thermalizing during implantation is very fast, therefore CoAl2O4 can not be formed at that time. However, such reactions are possible upon thermal annealing.
4. We predicted that ZrO2 can be formed during implantation
As implanted
800C
During annealing amount of ZrO2 decreases
1400 C
Zr XPS lines in sapphire implanted with51017
Zr ions/cm2 and annealed at 800C and 1400C
5. 800C
1400 C
a
As implanted
Having a peak for CoO in as implanted case is in controversy with the thermodynamics data.
Co XPS lines in sapphire implanted with51017 Co ions/cm2 and annealed at 800C and 1400C
6. Oxygen O1s line positions in Al2O3 cover a broad range extending from 528.7 eV up to 532.7 eV and it is not excluded that the observed shift is associated with crystallographic recovery during the annealing.
?
Measurements on virgin and annealed sapphire are in progress to clarify this point.
XPS oxygen O1s lines in Zr-and Co-implanted sapphire samples after annealing at 800C and 1400C
7. Co-implantation
Surface topology in the Zr-implanted sample shows droplets of zirconium oxide.
Zr-implantation
By contrast, surface of the Co-implanted sample is completely free of any deposits. We conclude that Co must have diffused into the sample.
SEM photographs of sapphire surface
implanted and annealed at 800 C
Implanted fluencies: 51017 ions/cm2
8. Co
Annealing in vacuum for 1 hr
>1000C
The Co-implanted samples turned blue after annealing at 1400 C. On the other hand it is well known that Co spinel CoAl2O4 formed in traditional solid-state reactions above 1000 C is bright blue.
9. RBS spectra of Zr/Co implanted sapphire
10. 11. Implantation profiles and simulation of RBS spectra of the Zr/Co-implanted and annealed sapphire
12. In Zr sample it is seen that Zr accumulates in the surface layer and does not spread over the sample bulk, as deduced from constant intensity of Al edge in channels 350500. Aluminum is still seen at the surface, close to channel 530, but it is barely visible.
800 C
This result is consistent with the SEM image of this sample showing an almost full coverage of the surface with zirconium oxide foam.
Depth(nm)
13. At 800 C an almost metallic Co layer must have been formed near the surface. After annealing at 1400 C, the Al threshold recovers to previous position, and the Co peak spreads over a greater depth.
concentration
800 C
Depth(nm)
14. Zr
No Zr lines are seen after implantation and after annealing. Instead, a number of peaks associated with zirconium oxides of different structure are observed after annealing. They include tetragonal, and monoclinic forms. We conclude that zirconium does not segregate into metal and instead it replaces Al from AlO bonds forming ZrO2 compound. In XPS data AlO bonds are still seen due to incomplete coverage of the surface with the new compound.
15. Co
After implantation a broad cubic Co peak is seen at 2=44.2. Upon annealing this peak narrows and another peak at 2=51.5 appears. At the same time, a number of peaks associated with CoAl2O4 spinel appear, as shown by the markers. Broad Co peak suggests formation of Co nanoinclusions of small size. Narrowing
and reduction in intensity reflects Ostwald ripening of the peaks followed by their dissolution and transformation into spinel. This behavior is consistent with RBS results showing a growth of Co layer after 800 C annealing and XPS transformation occurring at 1400 C.
16. ?
Zr-implanted
Why can notwe see the ZrO2 peak here?
It seems we have ZrO2during annealing.
Co-implanted
?
XRD with Cu K (=0.154 nm)
XRD data for as received/implanted/implanted and annealed sapphire samples. Implantation: 51017 ions/cm2 & Annealing: 1400 C in argon.
17. I think this paper is a weak paper and suffers from a lot of problems:
It doesnt have a SEM topology micrograph for virgin alumina to compare the other two graphs with.
The amount of dose for the ions is at least 10 times more than a proper dose for having a reasonable result. In other words instead of ion implantation they form a thin layer of metal on the sapphire.
It doesn't have any TEM graph to see if the CoAl2O4 and other oxide compound exist in the sample.
The XPS results are not reliable, because during sample preparation there is no guarantee to take a layer of alumina with the same stoeciometry ratio of 2: 3.
There is no optical measurement to proofif the blue color after annealing appears because of cobalt aluminates existing.
Thethermodynamics data predict that Zr react with alumina, but XRD doesn't show that. At the same time the peak for as implanted Co sample can be a sign for having CoO that is not true because of thermodynamics point of view and the other reasons.
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Please email me if you want to know more.
18. Thank you