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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.


The spectra for reference samples [Si (100), Si (111), Al2O3 (0001), and diamond (100)] and hard disk samples [6 nm-DLC (Sputter), 10 nm-DLC (CVD) and Co-Cr alloy (hard disk without DLC)].
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Figure 4: The spectra for reference samples [Si (100), Si (111), Al2O3 (0001), and diamond (100)] and hard disk samples [6 nm-DLC (Sputter), 10 nm-DLC (CVD) and Co-Cr alloy (hard disk without DLC)].

Mentions: To measure f, we set Fe to be a value as small as possible, at which the resonant peak was clear and settled in frequency. The value depended on the sample material. The resonance frequencies for Si (100), Si (111), Al2O3 (0001), and diamond (100) were f = 199.3 ± 1.3 kHz, 218.6 ± 1.9 kHz, 254.5 ± 1.1 kHz, and 281.0 ± 1.1 kHz, where Fe is set to 300, 400, 500, and 700 nN, respectively. The errors show the 95% confidence regions (±2σ). The excellent reproducibility was attained in the measurements for 5–10 different positions on each reference surface. Figure 4 shows examples of spectra for the reference samples.


Characterization of Films with Thickness Less than 10 nm by Sensitivity-Enhanced Atomic Force Acoustic Microscopy
The spectra for reference samples [Si (100), Si (111), Al2O3 (0001), and diamond (100)] and hard disk samples [6 nm-DLC (Sputter), 10 nm-DLC (CVD) and Co-Cr alloy (hard disk without DLC)].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: The spectra for reference samples [Si (100), Si (111), Al2O3 (0001), and diamond (100)] and hard disk samples [6 nm-DLC (Sputter), 10 nm-DLC (CVD) and Co-Cr alloy (hard disk without DLC)].
Mentions: To measure f, we set Fe to be a value as small as possible, at which the resonant peak was clear and settled in frequency. The value depended on the sample material. The resonance frequencies for Si (100), Si (111), Al2O3 (0001), and diamond (100) were f = 199.3 ± 1.3 kHz, 218.6 ± 1.9 kHz, 254.5 ± 1.1 kHz, and 281.0 ± 1.1 kHz, where Fe is set to 300, 400, 500, and 700 nN, respectively. The errors show the 95% confidence regions (±2σ). The excellent reproducibility was attained in the measurements for 5–10 different positions on each reference surface. Figure 4 shows examples of spectra for the reference samples.

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.