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Characterization of Films with Thickness Less than 10 nm by Sensitivity-Enhanced Atomic Force Acoustic Microscopy

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ABSTRACT

We present a method for characterizing ultrathin films using sensitivity-enhanced atomic force acoustic microscopy, where a concentrated-mass cantilever having a flat tip was used as a sensitive oscillator. Evaluation was aimed at 6-nm-thick and 10-nm-thick diamond-like carbon (DLC) films deposited, using different methods, on a hard disk for the effective Young's modulus defined as E/(1 - ν2), where E is the Young's modulus, and ν is the Poisson's ratio. The resonant frequency of the cantilever was affected not only by the film's elasticity but also by the substrate even at an indentation depth of about 0.6 nm. The substrate effect was removed by employing a theoretical formula on the indentation of a layered half-space, together with a hard disk without DLC coating. The moduli of the 6-nm-thick and 10-nm-thick DLC films were 392 and 345 GPa, respectively. The error analysis showed the standard deviation less than 5% in the moduli.

No MeSH data available.


Relationship between γ and a/t, where the symbol ο represents the numerical result obtained by the theoretical analysis for indentation of a layered half-space [13], and the solid curve is a least-square fit of Eq. 3.
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Figure 2: Relationship between γ and a/t, where the symbol ο represents the numerical result obtained by the theoretical analysis for indentation of a layered half-space [13], and the solid curve is a least-square fit of Eq. 3.

Mentions: where and are the effective Young's moduli of a film and a substrate, respectively. The coefficient γ is a function of a/t, where t is the film thickness. The numerical result on a relation of γ and a/t was graphically shown in reference [13]. Note that the symbol a in reference [13] is defined as the square root of the contact area, which differs from the definition of a (the radius of the contact area) in this letter, and then γ multiplied by π1/2 equals the symbol α in reference [13]. Examples of the numerical result are indicated with circles in Figure 2. The numerical data can be well fitted by the following formula.


Characterization of Films with Thickness Less than 10 nm by Sensitivity-Enhanced Atomic Force Acoustic Microscopy
Relationship between γ and a/t, where the symbol ο represents the numerical result obtained by the theoretical analysis for indentation of a layered half-space [13], and the solid curve is a least-square fit of Eq. 3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211417&req=5

Figure 2: Relationship between γ and a/t, where the symbol ο represents the numerical result obtained by the theoretical analysis for indentation of a layered half-space [13], and the solid curve is a least-square fit of Eq. 3.
Mentions: where and are the effective Young's moduli of a film and a substrate, respectively. The coefficient γ is a function of a/t, where t is the film thickness. The numerical result on a relation of γ and a/t was graphically shown in reference [13]. Note that the symbol a in reference [13] is defined as the square root of the contact area, which differs from the definition of a (the radius of the contact area) in this letter, and then γ multiplied by π1/2 equals the symbol α in reference [13]. Examples of the numerical result are indicated with circles in Figure 2. The numerical data can be well fitted by the following formula.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

We present a method for characterizing ultrathin films using sensitivity-enhanced atomic force acoustic microscopy, where a concentrated-mass cantilever having a flat tip was used as a sensitive oscillator. Evaluation was aimed at 6-nm-thick and 10-nm-thick diamond-like carbon (DLC) films deposited, using different methods, on a hard disk for the effective Young's modulus defined as E/(1 - ν2), where E is the Young's modulus, and ν is the Poisson's ratio. The resonant frequency of the cantilever was affected not only by the film's elasticity but also by the substrate even at an indentation depth of about 0.6 nm. The substrate effect was removed by employing a theoretical formula on the indentation of a layered half-space, together with a hard disk without DLC coating. The moduli of the 6-nm-thick and 10-nm-thick DLC films were 392 and 345 GPa, respectively. The error analysis showed the standard deviation less than 5% in the moduli.

No MeSH data available.