Effect of Air Dielectric Barrier Discharge on Calcium-Silicate Thinfilm

Objectives:

Calcium phosphates and bio-active glass/ceramics were introduced by several thinfilm processes to improve surface bioactivity of dental implant. However, the adhesion problem has not been solved even though ion-beam assisted deposition.

Plasma discharge technologies were known for surface modification treatments. The unique characteristic of dielectric discharge in air at atmosphere pressure is streamers which are well established plasma columns containing excited ions and electrons.

In this research, dielectric barrier discharge (DBD) in air at atmospheric pressure was considered as a method to solve adhesion problem because it was expected that the hitting by well established plasma columns would act as spot welding process.

Methods:

Calcium-silicate (Ca:Si = 63:37) thinfilm (300 nm) was deposited on Ar ion-beam pre-cleaned silicon wafer and annealed in air at 400°C. The specimen was placed between alumina plates of 1 mm thick with the areal metal electrodes. Specific high voltage DC pulses were introduced to fire the air DBD. The surface was characterized by optical emission spectra (OES), contact angle measurement, FTIR-ATR, FE-SEM/EDX, AFM.

Results:

Hydroxyl groups which could be immobilized on calcium-silicate surface and activate bio-activity were observed by OES and its immobilization was also confirmed by FTIR-ATR spectra on the DBD treated calcium-silicate surface. The change of surface roughness was not significant by DBD treatment. Unique creator like surface was observed by the hitting of plasma column and spot like welding process. Titanium concentration in calcium-silicate near the creator from cross-sectional observation by FE-SEM/EDX was the evidence of the spot welding process. Increased reactivity of calcium-silicate thinfilm in phosphate buffed saline was observed with FE-SEM and significant adhesion problem was not observed because of the effect of streamer hitting.

Conclusion:

Plasma streamer played a role of spot welding process and improved adhesion.