It induces the presence of trace oxygen to react with the precursor molecules that lead to the occurrence of numerous peel-off sites [16]. Although the cracks appear on the PET surface coated by ALD with plasma pretreatment and PA-ALD, the deposited surface area achieves the smooth state. It indicates that the necessary chemical functional Anlotinib cost groups induced due to the energetic ion bombardment in plasmas have a significant role on the initial growth on the PET surfaces. The surface morphologies of Al2O3-coated PET films are shown in Figure 4. The root mean square (RMS) surface roughness is evaluated

to be 7.9 and 7.2 nm for the uncoated PET film and the Al2O3 deposited PET film by ALD, respectively. With the introduction of plasmas in ALD, the RMS surface roughness is raised to be MLN2238 nmr 8.1 and 9.8 nm for the Al2O3 deposited PET film by plasma pretreated ALD and PA-ALD, respectively. Given that the plasma provides the additional energy for chemical reactions in ALD process, the deposition of Al2O3 can be enhanced with the assistance of plasma in ALD. Figure 4 AFM images. (a) Uncoated PET film, the Al2O3-coated PET films by (b) ALD, (c) ALD with plasma pretreatment, and (d) PA-ALD. Wettability of the deposited Al2O3 film The wettability of the

Al2O3 film on PET is examined by means of the water contact angle measurement, as shown in Figure 5. It clearly demonstrates the significant improvement of wettability when the water contact angle reduces to 65.76° with the deposition of Al2O3 film on PET by ALD, compared to the contact angle of the uncoated substrate (88.26°). GS-4997 chemical structure The enhancement of wettability is attributed to the surface rearrangement by the ALD coating of aluminum oxide.

Further reduction of contact angle is achieved to be 54.9° and 55.07° by the plasma pretreated ALD and PA-ALD, respectively, which suggests that the introduction of plasma in ALD provides additional ion bombardment on the deposited Al2O3 film. It proposes that the plasma employed in ALD contributes to both eltoprazine the fragmentation of precursor molecules and the surface activation of PET surfaces. Figure 5 The water contact angle as a function of the aging time. Figure 5 also shows the recovering of water contact angle as a function of time. It shows that the induced modifications on the wettability of the Al2O3 film on PET are not permanent since the contact angle increases to around 86° in about 2 days, which approaches that of the uncoated PET film. The recovering of water contact angle suggests the decrease of surface free energy with aging time [17], which is caused by the reorientation of induced polar chemical groups into the bulk of the material [18, 19]. It is also worth noting that the water contact angles of Al2O3 films deposited by ALD and plasma pretreated ALD (approximately 94°) are higher than that of PA-ALD (approximately 88°) after 3 days of aging.