Room temperature amorphous to nanocrystalline transformation in ultra-thin films under tensile stress: anin situTEM study

Abstract

The amorphous to crystalline phase transformation process is typically known to take place at very high temperatures and facilitated by very high compressive stresses. In this study, we demonstrate crystallization of amorphous ultra-thin platinum films at room temperature under tensile stresses. Using a micro-electro-mechanical device, we applied up to 3% uniaxial tensile strain in 3-5 nm thick focused ion beam deposited platinum films supported by another 3-5 nm thick amorphous carbon film. The experiments were performed in situ inside a transmission electron microscope to acquire the bright field and selected area diffraction patterns. The platinum films were observed to crystallize irreversibly from an amorphous phase to face-centered cubic nanocrystals with average grain size of about 10 nm. Measurement of crystal spacing from electron diffraction patterns confirms large tensile residual stress in the platinum specimens. We propose that addition of the externally applied stress provides the activation energy needed to nucleate crystallization, while subsequent grain growth takes place through enhanced atomic and vacancy diffusion as an energetically favorable route towards stress relaxation at the nanoscale.

Structurally modified electrospun poly(methyl methacrylate) nanofibers as advanced host matrices for PbS quantum dots

“…The SAED patterns of each sample as given in Figure 3(b), (d), (f) show the successful incorporation of the complex to the fiber. The diffused rings obtained in each case indicate the presence of crystalline quantum dots in amorphous polymer 42 . Thus, the TEM results give a solid evidence for the preparation of pure and structurally modified PMMA nanofibers incorporated with PbS quantum dots supporting the previously mentioned FTIR and XRD results of the samples.…”

Switching properties of SrRuO 3 /Pb(Zr 0.4 Ti 0.6 )O 3 /SrRuO 3 capacitor grown on Cu-coated Si substrate measured at various temperatures

“…This indicates that the crystallinity of Ni-Al plays a very important role in the barrier performance, which is similar to that of the TaWSiC barrier [18]. Moreover, nanocrystalline Ni-Al dispersed in an a-Ni-Al matrix film may also relax some stresses in multilayer stack [19,20]. Therefore, a high-quality SRO/PZT/SRO/Ni-Al/Cu/Ni-Al/SiO 2 /Si heterostructure can be fabricated successfully using amorphous Ni-Al as diffusion barrier layer between Cu and SiO 2 /Si for its lack of grain boundaries as diffusion paths, and a two-step Ni-Al film as oxygen barrier layer to protect the Cu film from oxidation or reaction.…”

“…1) Although nanocrystalline grains in the higher-energy deposited Ni-Al film are found by HRTEM for the sample after the whole thermal processes, they should result from the high deposition energy during sputtering instead of heat treatment. Although heat treatment is the most commonly used technique in crystallization of amorphous solids, it requires temperatures comparable to half of the melting point to initiate any diffusion-based atomic restructuring process [16]. The melting temperature of Ni 3 Al is about 1430 • C [17], however, only 550 • C was used in our experiment.…”

Wide optical gap B-doped nc-Si thin films with advanced crystallinity and conductivity on transparent flexible substrates for potential low-cost flexible electronics including nc-Si superstrate p–i–n solar cells

“…In the present investigation a superior crystallinity on flexible PET-substrate arises from strain-induced crystallization at the incubation-layer due to substrate-bending via plasma-heating. 56 Stress generated at substrate/incubation-layer interface provides the activation energy for nanocrystallization and favours the formation of larger-nanocrystals at elevated and also leads to a gradually increased difference in crystallinity, although trivially, compared to that on glass substrate. 57,58 Although having a higher (~80%), the (~6.01x10 -1 S cm -( ) ( ) 1 ) of the p-nc-Si film prepared at ambient temperature ( =30 °C) appears slightly lower than (~9.95 x 10 -1 S cm -1 ) ( ) and the deviation increases at > 100 °C, which indicate that the surface strain/bending may not be favorable for electrical transport in samples on flexible PET-substrates, which becomes more stringent at higher , due to the formation of micro-cracks on the sample-surface.…”