Study on deposition of Al_2O_3 films by plasma-assisted atomic layer with different plasma sources

In this paper,Al_2O_3 thin films are deposited on a hydrogen-terminated Si substrate by using two home-built electron cyclotron resonance（ECR） and magnetic field enhanced radio frequency plasma-assisted atomic layer deposition（PA-ALD） devices with Al（CH_3）_3（trimethylaluminum,TMA） and oxygen plasma used as precursor and oxidant,respectively.The thickness,chemical composition,surface morphology and group reactions are characterized by in situ spectroscopic ellipsometer,x-ray photoelectric spectroscopy,atomic force microscopy,scanning electron microscopy,a high-resolution transmission electron microscope and in situ mass spectrometry（MS）,respectively.We obtain that both ECR PA-ALD and the magnetic field enhanced PAALD can deposit thin films with high density,high purity,and uniformity at a high deposition rate.MS analysis reveals that the Al_2O_3 deposition reactions are not simple reactions between TMA and oxygen plasma to produce alumina,water and carbon dioxide.In fact,acetylene,carbon monoxide and some other by-products also appear in the exhaustion gas.In addition,the presence of bias voltage has a certain effect on the deposition rate and surface morphology of films,which may be attributed to the presence of bias voltage controlling the plasma energy and density.We conclude that both plasma sources have a different deposition mechanism,which is much more complicated than expected.

DBD plasma assisted atomic layer deposition alumina barrier layer on self-degradation polylactic acid film surface

In this work, the plastic of polylatic acid(PLA) film is coated by alumina(Al_2O_3)through dielectric barrier discharge plasma assisted atomic layer deposition(DBD PA-ALD) for the proposal of the barrier property enhancement. The influence of ALD Al_2O_3 thickness on properties of barrier, mechanical, optical and degradation is investigated in detail. It is obtained that the growth rate of Al_2O_3 in DBD PA-ALD is as quick as 0.12 nm/cycle. After coated～40 nm Al_2O_3, the water vapor transmission rate of PLA is reduced by two orders of magnitude.Additionally, it is noticed that the tension strength of the coated film is improved slightly,whereas the light transmission rate is decreased with the increase of Al_2O_3 thickness. The degradation test shows that Al_2O_3 coating almost does not affect the self-degradation rate of PLA film.