Method to increase the thickness and quality of diamond layers using plasma chemical vapor deposition under (H, C, N, O) system

A method to increase the thickness of diamond layers grown by plasma chemical vapor deposition (CVD) is presented. Undesired polycrystalline diamond growth that typically occurs during long time periods of deposition was suppressed by introducing oxygen into the source gas mixture. To maintain a stable growth environment, a movable stage was introduced to control the distance from the top surface of the substrate to the core of the discharge region. This made it possible to sustain uninterrupted growth for over 200 h until the thickness of the CVD layer has reached 6 mm. The use of this continuous deposition process prevents the formation of growth interfaces, which are believed to be an origin of dislocations, in the CVD-grown layer. [Display omitted] •Technique of diamond growth without growth interfaces by plasma CVD was studied.•Introduction of oxygen as well as nitrogen into the source gas reduced undesired polycrystalline growth.•Growth of 6-mm-thick crystals with deposition times of 200 h was achieved.•During the growth, all the growth conditions were maintained but only the movable stage was controlled.