Carbon spheres are carbon materials that have a near spherical and a spherical shape. Many carbon spheres have been extensively used such as batteries, fuel cells, capacitors. Because these materials have a lot of advantages : high surface area, high thermal stability, low density. During last few decades, carbon microspheres have been synthesized in a various of methods and studies on their applications have been reviewed.
In this study, we suggested the mixed-source HVPE(Hybride Vapor Phase Epitaxy) method that can synthesize carbon spheres. HVPE reactor consists of two furnaces. The temperature of the first furnace was 850 ℃ for 1.5h where Ga, Al source on graphite crucible. Source vapors were carried to the second furnace by nitrogen carrier gas. The temperature of the second furnace was kept at about 1095℃ for 3h and sapphire substrate was placed on this reactor. In this reaction, NH3, HCl had been used to make carbon spheres.
Carbon sphere was synthesized during the process of LED structure. The carbon materials from graphite boat vaporized outside the source zone, carbon cholrides were carried with N2 gas to the growth zone. There are many obstacles to grow epi-layer on sapphire in growth zone. This suggests that there seems like holes on epi-layer. This space could act as template providing the nucleation site for carbon sphere formation.
The SEM image of carbon microspheres indicated that they have a smooth surface with a diameter of 100~350um. XPS(X-ray photoelectron spectroscopy) showed many ingredients involved in carbon sphere. And CL measurement was found near at 550nm in the visible range.
We found that mixed-source HVPE method was one of promising growth methods for carbon spheres.