Influence Of Peak-like Micro Structures On The Contact Angle On Silicon Surfaces

Wettability is an important property of solid surfaces,which can be modified by changing its texture and(or)its chemistry.The materials with different surface wettability have been widely used in daily life and industrial production.It is of great academic significance and engineering application value by studying the influence of different microstructures morphology on wettability and achieving it.In this paper,the peak-like microstructures were prepared by Plasma Immersion Ion Implantation(P?)on the surface of the polished monocrystalline silicon.The influence of the different mixture ratio of etching gas to passivation gas on the surface morphology and wetting characteristics of silicon was systematically investigated.The surface morphology was characterized by Scanning Electron Microscope(SEM)and Atomic Force Microscope(AFM),and the static and dynamic macroscopic contact angles of the micro structural surface were measured.According to the surface microstructural morphology obtained by the experimental characterization,the geometric model of the parameterized microstructural surface was established.The spread process of droplets on the different types of microstructural surface and the influence of the surface microstructural parameters on the wettability were studied by the VOF method.The experimental results showed that P? technology can produce obvious "peak-like" microstructures on the surface of polished monocrystalline silicon.With the increase of the mixture ratio of gases,the height of the convex structure first increased and then decreased slightly,while the projection area of the microstructure increasing continuously.The contact angle measurement results showed that the macroscopic contact angle of the sample surface was affected by the surface chemical properties and surface morphology.The increase of surface roughness and area ratio will enlarge the macro static contact angle.With the increase of the gas mixing ratio in the P? process,the advancing contact angle and the back contact angle increased gradually,and the contact angle hysteresis changed irregularly.The numerical simulation showed that the VOF model can better realize the numerical simulation of the macroscopic contact angle on the surface of the complex structure.The presence of the surface microstructures hindered the spread of the droplets on the surface,which resulted in the macroscopic infiltration characteristics of the droplets on the microstructural surface.The three-dimensional morphology of the peak microstructure was simplified by the two-dimensional axisymmetric CFD model with triangular waveform,which was highly consistent with the experimental results.Under the body force,the droplet movement process was made of deformation and movement.On the smooth surface,the droplet moved overall and maintained the constant advancing and receding angles.However,on the microstructure surface,the droplet moved partially for the different advancing and receding angles.The advancing angles almost remained constant,but the receding angle was close to zero during the movement on the microstructure surface.