Fabrication Of Super-Hydrophobic Thin Films By Dual Source Driven Atmospheric Plasma

Atmospheric pressure low-temperature plasma has the characteristics of low gas temperature,high physical and chemical activity,and no vacuum requirements.It has broad application prospects in material surface modification,such as in the fabrication of super-hydrophobic/oleophobic,super-hydrophilic surfaces.However,the uniform treatment of the surface of the material under atmospheric pressure places stringent requirements on the stability and uniformity of the plasma source,which is also a key problem in the current large-area surface modification of materials by plasma.Focusing on the above research difficulties,we designed a new type of atmospheric pressure plasma material surface treatment device,which can significantly improve the stability and uniformity of argon dielectric barrier discharge in an open environment by coupling two driving power sources,and it is used in film deposition to fabricate a uniform super-hydrophobic surface on glass samples.The main research contents of this article are as follows:A three-electrode dual-power-driven plasma generator device was designed.The middle electrode was a ground electrode.The upper RF power source and the lower pulse power source shared one ground.Each of them was an independent loop,which reduced the influence between power sources.The lower pulse discharge can effectively reduce the initial voltage of the upper RF discharge,making RF discharge easier to generate;at the same time,the active particles(seed electrons,metastable state,etc.)generated by the RF discharge make the lower pulse discharge more stable and uniform,suitable for surface treatment and film deposition.Hexamethyldisilazane(HMDSN)was added to the discharge as a precursor.The OES spectrum showed that the monomer was cracked mainly in the RF discharge region,and the generated CH,Si H and other molecules entered the uniform pulse discharge area below,polymerized and deposited on the glass substrate thus thin film with low surface energy is formed.The results show that the uniformity and hydrophobicity of the film deposited by dual power supply are better than that of a single power supply,and the static contact angle can reach 170 degrees.When the positive polarity pulse and the RF power are used simultaneously,a uniformly distributed dot pattern can be deposited on the sample under certain parameters,while the RF / negative pulse dual source synergistic discharge forms a uniform film(no pattern).Combined with the discharge image captured by a high-speed camera and thin-film physicochemical analysis,it is found that the fundamental reason for the formation of the above patterned and un-patterned films is that the positive and negative pulse discharges have different discharge forms,positive pulse discharge shows a "column dispersion" shape,while negative pulse discharge is in a form of "bulk dispersion",molecules cracked from monomers generated by radiofrequency discharge are more prone to chain reaction under the function of the pulse discharge area below,including further cracking and polymerization,etc.,a uniform patterned or un-patterned super-hydrophobic film is deposited corresponding to the different form of the pulse discharge.This work not only innovatively provided practical ideas for large-area homogenized plasma surface treatment,but also laid an experimental and theoretical basis for the vapor deposition of special patterned or uniform functional thin films.