Granted Patent B1

US 9,343,275 · App. 13/490,214 · Granted May 17, 2016

Abstract

Claims (161)

1. A method for characterizing a carbon overcoat with a thickness of three nanometers or less, comprising:

performing electron energy loss spectroscopy (EELS) spectrum imaging for an area of a preselected carbon-based material and an area of a carbon overcoat of a magnetic head or a magnetic data storage medium to generate a reference EELS dataset and a carbon overcoat EELS dataset, respectively,

wherein the carbon overcoat has a thickness of three nanometers or less,

wherein the performing EELS spectrum imaging comprises performing high energy resolution low-loss EELS spectrum imaging and core-loss EELS spectrum imaging for both the area of the preselected carbon-based material and the area of the carbon overcoat;

removing plural scattering in both the reference EELS dataset and the carbon overcoat EELS dataset to account for the difference in thickness between the preselected carbon-based material and the carbon overcoat;

quantifying a ratio of sp 3 bonding to sp 2 bonding of the carbon overcoat based on the reference EELS dataset and the carbon overcoat EELS dataset; and extracting a carbon overcoat element profile and a two-dimensional map of the carbon overcoat in the core-loss EELS spectrum from the carbon overcoat EELS dataset.

2. The method of claim 1 , further comprising measuring a thickness of the carbon overcoat using a microscopy technique selected from the group consisting of transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM).

3. The method of claim 2 , further comprising measuring a thickness of a sub-layer of the carbon overcoat, the sub-layer comprising carbon and a seed material.

4. The method of claim 3 , wherein the thickness of the sub-layer of the carbon overcoat is measured using a microscopy technique selected from the group consisting of energy filtered transmission electron microscopy (EFTEM) and scanning transmission electron microscopy (STEM).

5. The method of claim 1 , wherein the preselected carbon-based material comprises a material selected from the group consisting of microcrystalline graphite and C 60 .

6. The method of claim 1 , wherein the preselected carbon-based material comprises substantially 100 percent sp 2 carbon bonding.

7. The method of claim 1 , further comprising performing power-law background subtraction on the reference EELS dataset and the carbon overcoat EELS dataset to extract signals for both the preselected carbon-based material and the carbon overcoat.

8. The method of claim 1 , wherein the quantifying the ratio of sp 3 bonding to sp 2 bonding of the carbon overcoat comprises:

determining a pi orbital intensity (I π ) and a sigma orbital intensity (I σ ) at a carbon K-edge for both the carbon overcoat and the preselected carbon-based material using the EELS datasets; and

calculating a number fraction of sp 3 bonding and a number fraction of sp 2 bonding of the carbon overcoat based on the following equations:

F

⁡

(

sp

3

)

=

1

-

3

·

N

π

N

σ

1

+

N

π

N

σ

,

where

N

π

N

σ

=

[

I

π

/

I

σ

]

coc

3

·

[

I

π

/

I

σ

]

reference

,

and

F

⁡

(

sp

2

)

=

1

-

F

⁡

(

sp

3

)

,

where F(sp 3 ) is the number fraction of the sp 3 bonding, F(sp 2 ) is the number fraction of the sp 2 bonding, N π is a number of carbon atoms having the sp 2 bonding, and N σ is a number of carbon atoms having the sp 3 bonding.

9. The method of claim 8 , wherein the quantifying the ratio of sp 3 bonding to sp 2 bonding of the carbon overcoat further comprises removing plural scattering by Fourier-Ratio in both the reference EELS dataset and the carbon overcoat EELS dataset.

10. The method of claim 8 ; wherein the quantifying the ratio of sp 3 bonding to sp 2 bonding of the carbon overcoat further comprises applying a non-linear least squares (NLLS) fitting on both the reference EELS dataset and the carbon overcoat dataset to determine the I π and I σ .

11. The method of claim 1 , wherein the carbon overcoat comprises a diamond-like carbon.

12. A method for characterizing a carbon overcoat with a thickness of three nanometers or less, comprising:

measuring a thickness of a carbon overcoat of a magnetic head or a magnetic data storage medium using transmission electron microscopy (TEM),

wherein the carbon overcoat has a thickness of three nanometers or less;

measuring a thickness of a sub-layer of the carbon overcoat using energy filtered transmission electron microscopy (EFTEM) or scanning transmission electron microscopy (STEM), the sub-layer comprising carbon and a seed material;

performing electron energy loss spectroscopy (EELS) spectrum imaging for an area of a preselected carbon-based material and an area of the carbon overcoat to generate a reference EELS dataset and a carbon overcoat EELS dataset,

wherein the performing EELS spectrum imaging comprises performing high energy resolution low-loss EELS spectrum imaging and core-loss EELS spectrum imaging for both the area of the preselected carbon-based material and the area of the carbon overcoat;

removing plural scattering in both the reference EELS dataset and the carbon overcoat EELS dataset to account for the difference in thickness between the reference preselected carbon-based material and the carbon overcoat;

quantifying a ratio of sp 3 bonding to sp 2 bonding of the carbon overcoat based on the reference EELS dataset and the carbon overcoat EELS dataset; and

extracting a carbon overcoat element profile and a two-dimensional map of the carbon overcoat in the core-loss EELS spectrum from the carbon overcoat EELS dataset.

13. The method of claim 12 , wherein the TEM is scanning transmission electron microscopy (STEM).

14. The method of claim 12 , wherein the quantifying a ratio of sp 3 bonding to sp 2 bonding of the carbon overcoat comprises:

determining a pi orbital intensity (I π ) and a sigma orbital intensity (I σ ) at a carbon K-edge for both the carbon overcoat and the preselected carbon-based material using the EELS datasets; and

calculating a number fraction of the sp 3 bonding and a number fraction of the sp 2 bonding of the carbon overcoat based on the following equations:

F

⁡

(

sp

3

)

=

1

-

3

·

N

π

N

σ

1

+

N

π

N

σ

,

where

N

π

N

σ

=

[

I

π

/

I

σ

]

coc

3

·

[

I

π

/

I

σ

]

reference

,

and

F

⁡

(

sp

2

)

=

1

-

F

⁡

(

sp

3

)

,

where F(sp 3 ) is the number fraction of the sp 3 bonding, F(sp 2 ) is the number fraction of the sp 2 bonding N π is a number of carbon atoms having the sp 2 bonding, and N σ is a number of carbon atoms having the sp 3 bonding.

Assignments (8)