Growth of in situ multilayer diamond films by varying substrate-filament distance in hot-filament chemical vapor deposit
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a Ürgen Department of Metallurgical and Materials Engineering, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey (Received 2 May 2012; accepted 18 October 2012)
Single and multilayer diamond films were grown on silicon by varying substrate distance in hot-filament chemical vapor deposition. The grown films were characterized by scanning electron microscope (SEM) and Raman spectroscopy. From SEM surface images, it was observed that the films grown at substrate distances of 8, 7, and 6 mm and temperatures of 740, 780, and 830 °C possessed cauliflower, pseudocubes, and finally well-faceted cubes morphology. SEM fracture cross-sectional investigations revealed that growth of pseudocubes initiated on the top of cauliflower structure. By using the parametric relations gathered from single layer diamond growth studies, first time, multilayer diamond coatings were grown in situ with tunable thickness by only varying the substrate distance from filament assembly during deposition.
I. INTRODUCTION
Since the development of the chemical vapor deposition (CVD) techniques for growing diamond thin and thick films, a wide range of cutting edge application areas, such as biological sensors, medical implants, infrared imaging technology, light/field emitter devices, heat sinks for electronic equipment, electrode materials, cutting tools, fusion plasma facing components, etc., have emerged for them.1–8 Hot-filament CVD and microwave CVD are the most widely used techniques for growing diamond films. Uniform diamond coatings on large area substrates can easily be achieved with hot-filament CVD by maintaining high film uniformity compared to microwave CVD.8 A wide variety of diamond with different microstructures and morphology can be grown by varying the deposition conditions in CVD processes, and consequently, these variations affect growth rate and other properties as well.9–11 Nucleation and growth of diamond films have been the subjects of numerous studies. Very comprehensive reviews have been published covering and analyzing the literature on diamond nucleation and growth.12–15 In these studies, the critical role of the substrate temperature or distance from filament assembly on diamond growth morphology has been stressed. For adjusting diamond-coated tools and components to different applications, it is necessary not only to adapt diamond growth to substrate requirements but also to match diamond coating properties to application requirements to a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.378 J. Mater. Res., Vol. 27, No. 24, Dec 28, 2012
achieve high performance corresponding to the extreme properties of diamond.16 Multilayer diamond films may have useful applications in many engineering fields, e.g., in the areas requiring increased shock resistance. Takeuchi et al.17 showed that in polycrystalline diamond film, due to crack propagation through the columnar particles, toughness of the film is decreased. The problem was overcome by applying bias current to the substrate repeatedl
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