## 3 Results
### Prediction of Infrared Frequencies of Ga-N and Ga-CH\({}_{3}\) Species of Product Structures  
The current work proposed reaction pathways leading to possible four-product structures that formed in the first half of ALD (TMG adsorption) and possible four-product structures that formed in the second half of ALD (NH\({}_{3}\) nitridation). The vibrational characteristics of these structures were calculated and compared to other experimental results [11; 32]. Their predicted infrared frequencies are listed in Table 2. According to  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Reaction** & \multicolumn{4}{c}{**Activation Energy (eV)**} \\ \hline
**TGM Adsorption** & \begin{tabular}{c} **First** \\ **Activation Energy** \\ \end{tabular} & \
\begin{tabular}{c} **Second** \\ **Activation Energy** \\ \end{tabular} &
\begin{tabular}{c} **Average** \\ **Activation Energy** \\ \end{tabular} & **Reference** \\ \hline On Si–NH\({}_{2}\) surface of Si(100) & 2.00 & 1.44 & 1.72 & This work \\ On Si\({}_{2}\)–NH surface Si(100) & 1.11 & 2.07 & 1.59 & This work \\ Gas phase decomposition & - & - & 3.27 & [69] \\ On NH\({}_{2}\) terminated Ga(0001) & 1.28 & 1.84 & 1.56 & [47] \\ On GaN surface of Sapphire & - & - & 1.20 & [70] \\
**NH\({}_{3}\) adsorption** & & & & \\ \hline On PC 1–2 surface Si(100) & 1.88 & 1.92 & 1.90 & This work \\ On PC 2–1 surface Si(100) & - & - & 1.96 & This work \\ On PC 2–2 surface Si(100) & - & - & 2.00 & This work \\ On GaN surface on Sapphire & - & - & 1.14 & [70] \\ On Platinum Wire surface & - & - & 6.1 & [71] \\ On Un tungsten surface & - & - & 1.7 & [71] \\ On quartz sand surface & - & - & 1.52 & [72] \\ On calcined and sulfated & - & - & 1.02, 1.51 & [73] \\ Limestone surface & - & - & 1.14 & [70] \\ On Ga Surface of Sapphire & - & - & 1.34 & [11] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Activation energies of TMG and NH\({}_{3}\) on different substrate surfaces for ALD-GaN processes.  
the reaction mechanisms of TMG adsorption on the Si-NH\({}_{2}\) and Si\({}_{2}\)-NH surfaces in the adsorption step, TMG is adsorbed on the surfaces by forming Ga-N bonds. The IR frequencies of Ga-N stretching bonds that formed in PC 1-1, PC 2-1, and PC 1-2 stages were at wave numbers of 531, 530, and 537 cm\({}^{-1}\), respectively. This was in good agreement with the work of [PERSON] that reported an IR peak of the Ga-N stretching bond at a wave number of 534 cm\({}^{-1}\)[11]. The Ga-CH\({}_{3}\) stretching peaks formed in the PC 1-1, PC 2-1, and PC 1-2 stages were at wave numbers of 2917 cm\({}^{-1}\). This was in good agreement with the work of [PERSON] that reported an IR peak of the Ga-CH\({}_{3}\) stretching bond at a wave number of 2912 cm\({}^{-1}\)[32]. Additionally, Ga-N peaks were observed to shift slightly as TMG was adsorbed on different surface locations (SiN-H\({}_{2}\) or Si\({}_{2}\)-NH), and the Ga-N peaks also slightly shifted when the adsorption occupied one or two surface adsorption site(s). In the reaction step (NH\({}_{3}\) nitridation), NH\({}_{3}\) adsorbs on the surfaces by forming a Ga-N bond. The IR frequencies of the Ga-N stretching bonds that formed in the PC 3-1 and PC 3-2 stages were at wave numbers of 547 and 539 cm\({}^{-1}\), respectively. Similar to the TMG adsorption step, the Ga-N peaks were observed to shift slightly as the Ga-N bonds formed on different substrates (PC 2-1 or PC 2-2).