## 3 Results and Discussion  
The e-beam evaporation of thin films is an atomistic process, where atoms and molecules involved in the deposition in the vapor state chemically or physically adsorb on the surface of the substrate and eventually form a thin film following the thin film evaluation steps of nucleation, crystal/grain growth, coalescence, grain coarsening, and phase transformations [12]. The morphology of the resulting thin films largely depends on the substrate temperature, the deposition parameters, and the composition of the evaporated material. At an evaporation of metal oxides, the elemental composition of the thin films may differ from the initial material in the crucible. A variation in composition changes the thermochemical properties of each material and affects the diffusion towards microstructure formation [13]. In case of the deposition of complex compounds, the deviation in elemental composition of the formed thin films and initial material may occur due to the different evaporation rates of the chemical elements in the compound (Table 1). Such deviations can be minimized to the level of obtaining very close stoichiometry of the thin films compared to the initial material by adjusting the deposition parameters, such as the e-beam current, the substrate temperature, etc. Here, the microstructural and crystallographic properties are investigated by keeping technological parameters constant and depositing different compounds; therefore, a relatively larger difference in the elemental composition is observed for the doped compounds. The formed thin films were dense, and the density ranged from 86 to 92% of the relative density for undoped/doped barium cerate thin films and from 87 to 95% of the relative density for undoped/doped barium zirconate thin films compared to their theoretical densities [14; 15; 16; 17]. The high density is attributed to the formation of the vapor phase in its neutral form that is deposited in the substrate. A low deposition rate minimizes the collisions between the evaporated particles to generate a less dense vapor cloud above the crucible. However, accelerated electrons from the e-beam gun can interact with the high dense cloud to generate partial ionization and create defects on the film [18]. The vapor cloud density also is influenced by the evaporated material [19]. The growth of the thin films and the resulting microstructure can be described by several structure zone models (SZM), such as Movchan and Demichishin [20], Thornton [21], and modified SZMs for specific compounds or formation methods [22; 23]. The SZMs may give a qualitative guideline to the thin film growth processes during the deposition that can be altered by changes in the technological parameters. The formed thin films consisted \begin{table}
\begin{tabular}{c c c c c c c} \hline  & **Ba, at.\%** & **Zr, at.\%** & **Ce, at.\%** & **Y, at.\%** & **O, at.\%** & **Relative Density, \%** \\ \hline BCO thin films & 9.6 & - & 9.2 & - & 81.3 & 92 \\ BCO initial powder & 18.7 & - & 9.0 & - & 72.3 & \\ \hline BCY10 thin films & 10.3 & - & 7.5 & 1.1 & 81.1 & 86 \\ BCY10 initial powder & 20.0 & - & 8.8 & 2.0 & 69.2 & \\ \hline BCY20 thin films & 10.1 & - & 6.0 & 1.5 & 82.4 & 90 \\ BCY20 initial powder & 15.6 & - & 9.6 & 3.0 & 71.8 & \\ \hline BZO thin films & 14.0 & 10.2 & - & - & 75.9 & 95 \\ BZO initial powder & 15.4 & 13.8 & - & - & 70.8 & \\ \hline BZCY thin films & 13.3 & 12.8 & 1.0 & 2.8 & 70.2 & 87 \\ BZCY initial powder & 13.9 & 8.9 & 2.8 & 1.1 & 73.4 & \\ \hline BZY20 thin films & 13.7 & 8.1 & - & 1.1 & 77.0 & 90 \\ BZY20 initial powder & 13.7 & 10.8 & - & 2.5 & 73.0 & \\ \hline \end{tabular}
\end{table} 
Table 1: Elemental composition of the formed thin films and initial material. of oriented columnar grains defined by the grain boundaries. The microstructure of the formed thin was influenced by the dopants in the grain size and shape of the thin films.