Papers by Keyword: Saddle Field Source

Abstract: The mechanical performance of DLC coatings on 316L stainless steel deposited by a saddle field fast atom beam source has been evaluated using the four point bend (FPB) test. Two different deposition parameters, pressure and current were varied when depositing the films. Load-displacement measurements were carried out during the bend test to determine the load corresponding to crack initiation. This load designated as the cohesive strength of the coating which is also called the cracking resistance of coating and provides a measure of the strength of the coating. The cohesive strength of the coating was calculated based on elementary beam theory. Scanning Electron Microscopy (SEM) was used to determine the location of the crack. Finite element analysis was used to predict the stress distribution across the coating thickness. The experimental work on FPB tests has been used to support the numerical (finite element) model for the determination and prediction of film cohesive strength. It was observed that at lower deposition current, the cohesive strength increases with increased deposition pressure whereas, for higher deposition current, these values do not increase with increasing deposition pressure. The model takes into account the film’s Young’s modulus, thickness and deposition pressure and current, and has shown that it is capable of predicting film cohesive strength when combined with a theoretical formulation for brittle fracture. It has been observed that the maximum stress develops at the outer surface of the film and propagates through the film-substrate interface. This result has only been validated for films with higher Young’s modulus compared to that of the substrate material.

Abstract: This paper presents much more details on the process of etching n and p type SiC using a dc saddle field source. Here is described a method for stabilizing the dc discharge by adding controlled flow of O2 to SF6 in the source chamber. This kind of etching is used to fabricate 4H-SiC p-i-n diodes with a junction periphery protection. The effect of the junction periphery protection, the source power that terminates the etching process and testing environment on the breakdown voltage are investigated. The optimised p-i-n diodes exhibit a stable reverse bias operation with a breakdown voltage of 1700 V.