Abstract
Chemical vapour deposition (CVD) grown nanocrystalline diamond is an attractive material for the fabrication of devices. For some device architectures, optimisation of its growth on silicon nitride is essential. Here, the effects of three pre-growth surface treatments, often employed as cleaning methods, were investigated. Such treatments provide control over the surface charge of the silicon nitride substrate through modification of the surface functionality, allowing for the optimisation of electrostatic diamond seeding densities. Zeta potential measurements and X-ray photoelectron spectroscopy (XPS) were used to analyse the silicon nitride surface following each treatment. Exposing silicon nitride to an oxygen plasma offered optimal surface conditions for the electrostatic self-assembly of a hydrogen-terminated diamond nanoparticle monolayer. The subsequent growth of boron-doped nanocrystalline diamond thin films on modified silicon nitride, under CVD conditions, produced coalesced films for oxygen plasma and solvent treatments, whilst pin-holing of the diamond film was observed following RCA-1 treatment. The sharpest superconducting transition was observed for diamond grown on oxygen plasma treated silicon nitride, demonstrating it to be of the least structural disorder. Modifications to the substrate surface optimise the seeding and growth processes for the fabrication of diamond on silicon nitride devices.
Highlights
Chemical vapour deposition (CVD) grown nanocrystalline diamond is an attractive material for the fabrication of devices
Silicon nitride is an excellent substrate for the growth of CVD diamond due to their similar linear thermal expansion coefficients, which ensures the adhesion of diamond to the silicon nitride surface through a reduction in the interfacial stress[4,5]
Seeded silicon nitride wafers are exposed to CVD growth conditions incorporating a gas-based boron dopant, and the resulting films are analysed under scanning electron microscopy (SEM), Raman spectroscopy, and sample resistance’s are measured as a function of temperature, to allow for a comparison of film quality and structural properties
Summary
Chemical vapour deposition (CVD) grown nanocrystalline diamond is an attractive material for the fabrication of devices. The effects of three pre-growth surface treatments, often employed as cleaning methods, were investigated Such treatments provide control over the surface charge of the silicon nitride substrate through modification of the surface functionality, allowing for the optimisation of electrostatic diamond seeding densities. By definition the above techniques lead to significant surface damage[24] Whilst this is of little concern for high performance cutting tools, for thin film device applications, surface imperfections become wholly more significant, especially when the thermal and electrical properties of the diamond-silicon nitride interface are considered. The use of such seeding techniques is inappropriate. Seeded silicon nitride wafers are exposed to CVD growth conditions incorporating a gas-based boron dopant, and the resulting films are analysed under scanning electron microscopy (SEM), Raman spectroscopy, and sample resistance’s are measured as a function of temperature, to allow for a comparison of film quality and structural properties
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