Influence of deposition temperature on amorphous structure of PECVD deposited a-Si:H thin films

Abstract

Abstract:The effect of deposition temperature on the structural and optical properties of amorphous hydrogenated silicon (a-Si:H) thin films deposited by plasma-enhanced chemical vapour deposition (PECVD) from silane diluted with hydrogen was under study. The series of thin films deposited at the deposition temperatures of 50 − 200°C were inspected by XRD, Raman spectroscopy and UV Vis spectrophotometry. All samples were found to be amorphous with no presence of the crystalline phase. Ordered silicon hydride regions were proved by XRD. Raman measurement analysis substantiated the results received from XRD showing that with increasing deposition temperature silicon-silicon bond-angle fluctuation decreases. The optical characterization based on transmittance spectra in the visible region presented that the refractive index exhibits upward trend with increasing deposition temperature, which can be caused by the densification of the amorphous network. We found out that the scale factor of the Tauc plot increases with the deposition temperature. This behaviour can be attributed to the increasing ordering of silicon hydride regions. The Tauc band gap energy, the iso-absorption value their difference were not particularly influenced by the deposition temperature. Improvements of the microstructure of the Si amorphous network have been deduced from the analysis.

Firing-Stable PECVD SiOxNy/n-Poly-Si Surface Passivation for Silicon Solar Cells

“…The areas A 2100 and A 2000 are usually associated with large and small cavities, respectively, within the amorphous silicon network . Accordingly, the R -values are calculated to R = 0.9 for T dep = 220 °C and R = 0.5 for T dep = 400 °C, indicating the formation of cavity-rich n-a-Si layers for T dep = 220 °C, while T dep = 400 °C triggers the growth of densely packed amorphous networks . According to Figure , the cavity-rich or more “porous” n-a-Si films obtained with T dep = 220 °C are less prone to blistering even though it contains a higher amount of hydrogen, which is most likely related to a more efficient hydrogen effusion during annealing as compared to the densely packed a-Si films obtained with T dep = 400°C.…”

“…41 Accordingly, the Rvalues are calculated to R = 0.9 for T dep = 220 °C and R = 0.5 for T dep = 400 °C, indicating the formation of cavity-rich n-a-Si layers for T dep = 220 °C, while T dep = 400 °C triggers the growth of densely packed amorphous networks. 42 According to Figure 2, the cavity-rich or more "porous" n-a-Si films obtained with T dep = 220 °C are less prone to blistering even though it contains a higher amount of hydrogen, which is most likely related to a more efficient hydrogen effusion during annealing as compared to the densely packed a-Si films obtained with T dep = 400°C. On the contrary, molecular hydrogen might accumulate within macroscopic cavities located at the c-Si/ SiO x /a-Si interfaces due to the suppressed hydrogen effusion in dense n-a-Si layers that are grown with high deposition temperatures.…”

Optoelectronic Properties of Hydrogenated Amorphous Substoichiometric Silicon Carbide with Low Carbon Content Deposited on Semi‐Transparent Boron‐Doped Diamond

“…The pronounced band centered near 460–465 cm −1 corresponds to the transverse‐optic (TO) phonon mode of Si—Si bonds in an amorphous matrix of a‐Si:H, whereas the sharp Raman peak centered at 520 cm −1 is typical for crystalline Si, see Figure . The band centered below 480 cm −1 is followed by several bands, creating a wing spanning from 580 to 1100 cm −1 .…”

Improving the photoresponse spectra of BaSi2 layers by capping with hydrogenated amorphous Si layers prepared by radio-frequency hydrogen plasma

“…Regarding the substrate temperature (T S ) during the deposition of a-Si, a-Si:H depositions at T S = 180200 • C are recommended in PECVD. 22 Besides, even a pure a-Si capping layer deposited at T S = 180 • C acts as a passivation layer for BaSi 2 . 13, 14 We hence set T S at 180 • C in many samples.…”