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The rate sensitivity and plastic deformation of nanocrystalline tantalum films at nanoscale.

Cao Z, She Q, Huang Y, Meng X - Nanoscale Res Lett (2011)

Bottom Line: Nanoindentation creep and loading rate change tests were employed to examine the rate sensitivity (m) and hardness of nanocrystalline tetragonal Ta films.Experimental results suggested that the m increased with the decrease of feature scale, such as grain size and indent depth.The magnitude of m is much less than the corresponding grain boundary (GB) sliding deformation with m of 0.5.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, People's Republic of China. mengxk@nju.edu.cn.

ABSTRACT
Nanoindentation creep and loading rate change tests were employed to examine the rate sensitivity (m) and hardness of nanocrystalline tetragonal Ta films. Experimental results suggested that the m increased with the decrease of feature scale, such as grain size and indent depth. The magnitude of m is much less than the corresponding grain boundary (GB) sliding deformation with m of 0.5. Hardness softening behavior was observed for smaller grain size, which supports the GB sliding mechanism. The rate-controlling deformation was interpreted by the GB-mediated processes involving atomic diffusion and the generation of dislocation at GB.

No MeSH data available.


Related in: MedlinePlus

XRD patterns of the Ta films with different values of d. The insets are the bright-field TEM images and the corresponding selected area electron diffractions of the Ta films.
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Figure 1: XRD patterns of the Ta films with different values of d. The insets are the bright-field TEM images and the corresponding selected area electron diffractions of the Ta films.

Mentions: The XRD patterns of tetragonal Ta films are shown in Figure 1. The (002) and (004) diffraction peaks of β phases at 33.6° and 70.8° are found in Ta film prepared at RT. As the sputtering temperature increases to 673 K, the (002) and (004) peaks becomes more intensive, and two more peaks are observed in β phase at (410) and (202), while no peak is observed in α phase. This indicates that the samples consist of almost 100% β phase. It is noted that the two Ta films are not crystalline enough. The value of d determined by XRD and TEM is in the range of nanoscale. Even though the sputtering temperature reaches 673 K, the d is 20 nm, since the melting point of Ta is as high as 3269 K [17]. In Figure 1, full widths at half maximum (FWHM) of (004) peaks of Ta films are found to be very large. The FWHM of (002) peaks is smaller than that of (004) peaks, because (002) is the main crystal plane for XRD. The results of this study are consistent with those previously reported by Zhang et al. [18]. The plan-view microstructures of tetragonal Ta film with sputtering temperature of 300 and 673 K are shown in TEM counterparts of Figure 1. The corresponding selected area electron diffraction is shown at the right bottom corner of TEM insets. It is found that the grain size distribution is very uniform. The average d of the two samples is estimated to be about 10 and 20 nm through TEM images, respectively. It is well known that Scherrer equation is expressed by d = kλ/(βcos θ), where k is a constant (k = 0.9), λ is the wave length of the incident X-ray (λ = 0.15418 nm for Cu Kα radiation source), θ is Bragg angle, and β is the FWHM of the diffraction peak [19]. The values of β of the Ta films with sputtering temperature of RT and 673 K are 0.031 and 0.019, respectively. The grain sizes determined by Scherrer equation are about 13 and 23 nm, which are in agreement with TEM results.


The rate sensitivity and plastic deformation of nanocrystalline tantalum films at nanoscale.

Cao Z, She Q, Huang Y, Meng X - Nanoscale Res Lett (2011)

XRD patterns of the Ta films with different values of d. The insets are the bright-field TEM images and the corresponding selected area electron diffractions of the Ta films.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211239&req=5

Figure 1: XRD patterns of the Ta films with different values of d. The insets are the bright-field TEM images and the corresponding selected area electron diffractions of the Ta films.
Mentions: The XRD patterns of tetragonal Ta films are shown in Figure 1. The (002) and (004) diffraction peaks of β phases at 33.6° and 70.8° are found in Ta film prepared at RT. As the sputtering temperature increases to 673 K, the (002) and (004) peaks becomes more intensive, and two more peaks are observed in β phase at (410) and (202), while no peak is observed in α phase. This indicates that the samples consist of almost 100% β phase. It is noted that the two Ta films are not crystalline enough. The value of d determined by XRD and TEM is in the range of nanoscale. Even though the sputtering temperature reaches 673 K, the d is 20 nm, since the melting point of Ta is as high as 3269 K [17]. In Figure 1, full widths at half maximum (FWHM) of (004) peaks of Ta films are found to be very large. The FWHM of (002) peaks is smaller than that of (004) peaks, because (002) is the main crystal plane for XRD. The results of this study are consistent with those previously reported by Zhang et al. [18]. The plan-view microstructures of tetragonal Ta film with sputtering temperature of 300 and 673 K are shown in TEM counterparts of Figure 1. The corresponding selected area electron diffraction is shown at the right bottom corner of TEM insets. It is found that the grain size distribution is very uniform. The average d of the two samples is estimated to be about 10 and 20 nm through TEM images, respectively. It is well known that Scherrer equation is expressed by d = kλ/(βcos θ), where k is a constant (k = 0.9), λ is the wave length of the incident X-ray (λ = 0.15418 nm for Cu Kα radiation source), θ is Bragg angle, and β is the FWHM of the diffraction peak [19]. The values of β of the Ta films with sputtering temperature of RT and 673 K are 0.031 and 0.019, respectively. The grain sizes determined by Scherrer equation are about 13 and 23 nm, which are in agreement with TEM results.

Bottom Line: Nanoindentation creep and loading rate change tests were employed to examine the rate sensitivity (m) and hardness of nanocrystalline tetragonal Ta films.Experimental results suggested that the m increased with the decrease of feature scale, such as grain size and indent depth.The magnitude of m is much less than the corresponding grain boundary (GB) sliding deformation with m of 0.5.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, People's Republic of China. mengxk@nju.edu.cn.

ABSTRACT
Nanoindentation creep and loading rate change tests were employed to examine the rate sensitivity (m) and hardness of nanocrystalline tetragonal Ta films. Experimental results suggested that the m increased with the decrease of feature scale, such as grain size and indent depth. The magnitude of m is much less than the corresponding grain boundary (GB) sliding deformation with m of 0.5. Hardness softening behavior was observed for smaller grain size, which supports the GB sliding mechanism. The rate-controlling deformation was interpreted by the GB-mediated processes involving atomic diffusion and the generation of dislocation at GB.

No MeSH data available.


Related in: MedlinePlus