Crystallization of Cu-doped thin Ge film assisted with a Cu–Ge droplet

Abstract

We observed the crystallization process of an amorphous germanium (a-Ge) thin film, including copper (Cu) nanoparticles in the intermediate position of the structures in terms of depth, by using in situ TEM. It was found that a nanoscale droplet was formed around the Cu nanoparticles at 500 °C, which is lower than the eutectic temperature of the bulk Cu-Ge system (640 °C); following which, the nanoscale droplets solidified at the same temperature. The existence of a nanoscale liquid phase at a temperature lower than the bulk eutectic temperature is consistent with the eutectic system with gold nanoparticles on the Ge film. © 2020 The Japan Society of Applied Physics Fig. 1. (Color online) (a) Crystallization ratio derived from Raman scattering spectra at 500 °C for various annealing times. The inset shows the Raman scattering spectra of the as-deposited Cu-doped Ge film. Crosssectional TEM-EDX mapping for (b) Ge and (c) Cu.

Raman scattering spectroscopy for solid-phase and metal-induced crystallization of extremely thin germanium films on glass

“…The composition of Cu in the film with t Cu = 4 s was estimated to be approximately 0.1 from the SIMS profile in which the Cu atoms diffused from the middle to both Ge/ insulator interfaces; excessive atoms were gettered by the strain field around the defects. 25,26) These results indicate that the optimal value of t Cu exists below 1 s; that is, the suppressive supply of Cu (less than a few at% of Ge) is effective for enhancing the progress of MIC. Furthermore, it played a role in reducing the transition from the amorphous state to the nano-sized crystallite state, which was considered in the sputtering films.…”

“…Several TEM images and SIMS profiles have been demonstrated in other studies. 11,21,[24][25][26] 3. Results and discussion 3.1.…”

“…24) The other type of crystallization induced by Ge-Cu eutectic was found at a specific T a of 500 °C under an in situ TEM observation, which was reported separately. 26) In GeSn films, the following two main effects were expected for Sn:Sn-MIC and the synthesis of the Ge 1−x Sn s compound. For Sn-MIC, the effect of lowering the crystallization temperature was reported to be evident for the Sn contents of 9-25 at% 49,50) and to a small extent for 2 at%.…”

Evaluation of extremely thin polycrystalline germanium films and their TFT performance fabricated at 400 °C by Cu-induced crystallization on a glass substrate

“…[21][22][23][24] To investigate the details of the crystallization mechanism of Cu-MIC, we used Cu sandwiched between Ge as an initial film and performed in situ TEM observation of crystal growth at 500 °C. 25) Cu was found to exist as thin nanodisks with a diameter of several 10 nm immediately after deposition. The research showed that nanodroplets formed around the Cu nanodisks at 500 °C within 5 min, which then solidified.…”