•Polar groups of CO has a strongly contribution to facilitate initial ALD growth.•Surface roughness able to evaluate the ALD normal growth on the polymer substrate.•The Al2O3 ALD layer can be a buffer layer as pre-treatment-like to provide OH groups.•Ligand number in precursor molecules affect the resulted water compatible functional OH groups.In this study, polyethylene terephthalate (PET) substrate was successfully coated Al2O3 and TiO2 films by atomic layer deposition (ALD). The experiment results demonstrate that the Al2O3 can be deposited more efficiently than TiO2 on PET substrates. Further characterization on the coated substrates reveals that the density of hydroxyl OH groups play a significant role on the growth of the oxides ALD film. Chemical composition of the coated substrates is characterized by X-ray photoelectron spectroscopy, which shows that the CO elements are replaced by the Al - related elements in the Al2O3 - coated PET and the Ti - related elements in the TiO2 - coated PET. The results demonstrate that the CO has a strongly contribution to facilitate the initial ALD growth of the oxides thin films.

Two-dimensional TiO2 nanosheets were synthesized by atomic layer deposition (ALD) on dissolvable sacrificial polymer layer. The photocatalytic performance of free-standing TiO2 nanosheets prepared with different numbers of ALD cycles (100, 300, 500, and 1000) were investigated by evaluating the degradation rates of methyl orange solutions. It is shown that the photocatalytic activity increases due to Ti3+ defect and the locally ordered structures in amorphous TiO2 nanosheets. The difference in the surface areas of nanosheets may also play a crucial role in the photocatalytic activity. The results obtained in this work can have potential applications in fields like water splitting and dye-sensitized solar cells.

A study of sub-microsecond high voltage pulse excited glow discharges in atmospheric helium is carried out here. The discharge is generated between the powered copper electrode and ground electrode covered with a ceramic sheet. The electrical and optical characteristics of two discharge events in each voltage pulse in terms of discharge current amplitude, current pulse duration, time instant at current peak and accumulated charge in discharge are investigated on voltage pulse duration and pulse voltage magnitude. The time-resolved imaging with 5 ns exposure time is used to demonstration the spatio-temporal evolution of discharge. It is found that the first discharge depends markedly on pulse voltage magnitude and space charge accumulation on ceramic sheet surface plays an important role on ignition of second discharge.