## 3 Results  
We have grown several groups of samples while using different growth conditions. Table 1 summarizes the growth details. The Group A samples were grown, while the Sb cracking temperature was set at 700 \({}^{\circ}\)C so the evaporated beam was composed with mostly Sb\({}_{4}\) molecules. Group B samples were done with the Sb cracking temperature set at 1000 \({}^{\circ}\)C, so Sb\({}_{2}\) molecules were the primary source molecules in the evaporated beam (higher than 90%). The electrical properties are only measured on the continuous films in our study, because most samples tend to form island structures, so the electrical performance (insulating or conducting) is hard to obtain. Similarly, it is difficult to have good XRD signals for the samples that are either too thin or no growth was done. In the following analysis, we have only used the results that are reliable and reproducible. At the beginning, we tried to understand whether there is a difference between Sb\({}_{2}\) and Sb\({}_{4}\) in the growth. Figure 1a-c show the surface morphology. The antimony film of B-1 is a good conductor (more accurately, semimetal) according to the Hall measurement results (Table 2), but for A-1, it is an insulator. Another sample using Sb\({}_{4}\) molecules (A-2) were grown under 200 \({}^{\circ}\)C, and the electrical data can be seen in Table 2. It is obvious that sample A-2 is a semimetal with a carrier concentration in the 10\({}^{20}\)/cm\({}^{3}\) level. The higher growth temperature for A-2 sample seems to introduce Sb\({}_{2}\) molecules. Hence, we believe that there is a critical temperature (T\({}_{\rm critical}\)) that is between 150 \({}^{\circ}\)C and 200 \({}^{\circ}\)C, when T\({}_{\rm growth}\) \(<\) T\({}_{\rm critical}\), samples using Sb\({}_{4}\) molecules are insulating and, on the other hand, conductive when T\({}_{\rm growth}\) \(>\) T\({}_{\rm critical}\). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample No.**} & **Growth** & **Growth Time** & \multirow{2}{*}{**Crystalline/Amorphous**} & **Electrical** & **Effective** \\  & **Temperature** (\({}^{\circ}\)C) & **(min)** & & & **Performance** & **Thickness (nm)** \\ \hline A-1 & 150 & 10 & amorphous & insulating & 57.81 \(\pm\) 4.38 \\ B-1 & 150 & 10 & crystal & conducting & \(\approx\)15 \\ A-2 & 200 & 30 & crystal & conducting & 32.01 \(\pm\) 2.08 \\ A-3 & 225 & 30 & crystal & \(\backslash\) & 32.11 \(\pm\) 9.40 \\ A-4 & 250 & 30 & crystal & \(\backslash\) & 10.48 \(\pm\) 3.73 \\ A-5 & 265 & 30 & crystal & \(\backslash\) & 1.33 \(\pm\) 0.37 \\ A-6 & 270 & 30 & \(\backslash\) & \(\backslash\) & 0 \\ A-7 & 280 & 30 & \(\backslash\) & \(\backslash\) & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sample list with the growth parameters and properties. Sb\({}_{4}\) molecules were used in the growth of group A samples and Sb\({}_{2}\) molecules were used in the growth of group B samples. \({}^{\omega}\)(\({}^{\prime}\) means no data were obtained. Figure 1: (**a–c**) Atomic force microscope (AFM) images of sample A-1, A-2, and B-1. (**d**) X-ray diffraction (XRD) diffractogram of sample A-1, A-2, and B-1. (**e**) Proposed cracking mechanism of Sb\({}_{4}\) on the surface, showing the difference when T \(<\) T\({}_{\rm critical}\) and T \(>\) T\({}_{\rm critical}\). The growth by Sb\({}_{4}\) or Sb\({}_{2}\) molecules might have different kinetic mechanisms, so the difference in electrical properties indicates the transformation of Sb\({}_{4}\) to Sb\({}_{2}\) on the sapphire surface above the critical temperature might introduce a different arrangement of the Sb\({}_{2}\) molecules for the following nucleation. Most Sb\({}_{4}\) molecules exist in a tetrahedral structure [32; 33]. They are flattened into a planar structure when arriving the substrate surface. After that, they gradually change to a rectangle or distorted rectangle structure and, finally, they split into two Sb\({}_{2}\) molecules, i.e., Sb\({}_{4}\)\(\rightleftharpoons\)2 Sb\({}_{2}\) (Figure 1e).