Solid-State Reaction in Cu/a-Si Nanolayers: A Comparative Study of STA and Electron Diffraction Data

Abstract

The kinetics of the solid-state reaction between nanolayers of polycrystalline copper and amorphous silicon (a-Si) has been studied in a Cu/a-Si thin-film system by the methods of electron diffraction and simultaneous thermal analysis (STA), including the methods of differential scanning calorimetry (DSC) and thermogravimetry (TG). It has been established that, in the solid-state reaction, two phases are formed in a sequence: Cu + Si → η″-Cu3Si → γ-Cu5Si. It has been shown that the estimated values of the kinetic parameters of the formation processes for the phases η″-Cu3Si and γ-Cu5Si, obtained using electron diffraction, are in good agreement with those obtained by DSC. The formation enthalpy of the phases η″-Cu3Si and γ-Cu5Si has been estimated to be: ΔHη″-Cu3Si = −12.4 ± 0.2 kJ/mol; ΔHγ-Cu5Si = −8.4 ± 0.4 kJ/mol. As a result of the model description of the thermo-analytical data, it has been found that the process of solid-state transformations in the Cu/a-Si thin-film system under study is best described by a four-stage kinetic model R3 → R3 → (Cn-X) → (Cn-X). The kinetic parameters of formation of the η″-Cu3Si phase are the following: Ea = 199.9 kJ/mol, log(A, s−1) = 20.5, n = 1.7; and for the γ-Cu5Si phase: Ea = 149.7 kJ/mol, log(A, s−1) = 10.4, n = 1.3, with the kinetic parameters of formation of the γ-Cu5Si phase being determined for the first time.

Characterization of nanoscale atomic motion of Si in polycrystalline Cu layer

“…This solid phase evoked a change in the detection sensitivity factor of Si during depth profiling which is reflected in the concentration drop. According to Moiseenko et al [ 24 ], the reaction in nanolayers between Cu and Si is initiated at about 400 K and occurs in three steps: formation of amorphous CuSi phase, then formation of clusters Cu 3 Si and, finally, formation of the η’’-Cu 3 Si phase. The step-like drop of Si concentration seen in Fig.…”

Thermal Stability and Crystallization Processes of Pd78Au4Si18 Thin Films Visualized via In Situ TEM

“…Interestingly, Figure 2i also shows the presence of 100 nm particles that are proved to be pure Au precipitating from the original Pd(Au)-Si crystalline film, which will be thoroughly described below.The whole process of thermal heating was recorded in Supplementary Video S1. Despite the fact that all of the crystallization processes can be visualized at the nanoscale via in situ TEM and the exact determination of the resultant crystalline phases, some key parameters regarding the crystallization kinetics [29][30][31] are difficult to estimate, which is in part due to the lack of fine control over the heating rate. Future studies of in situ TEM techniques with improved fine control over the heating rate will address these difficulties.…”

Thermokinetic Study of Aluminum-Induced Crystallization of a-Si: The Effect of Al Layer Thickness

“…Simultaneously with heating, SAED patterns were registered, with the temperature of the sample being measured. The method was successfully used to investigate the phase formation during the solid-state reaction in different thin-film nanosystems: Al/Cu [29,30], Al/Pt [31], Al/Ag [32], Cu/Au [33], Al/Fe [34], Cu/Si [35], Fe/Si [36], Fe/Pd [33,37,38], and Co-ZrO 2 [39].…”