Step flow growth, diamond

A further elaboration of the two-step process was done by depositing a B-doped layer on an undoped (100) HOD film [265]. The source gas was a mixture of CH4 and trimethyl borane [B(CH4)3], whose concentrations were 0.5% and 10 ppm, respectively. As a result, a significant lateral growth of B-doped diamond film occurred, which (i) reduced the density of microtwins and (ii) enhanced a step-flow growth. The former result (i) is consistent with those of Refs. [4, 294]. 

Active diamond electronics has not successfully developed. After the demonstration of rudimentary high temperature Schottky diodes and transistors, problems with the deposition of semiconductor quality thin diamond films has limited further development. Imposing step flow growth on homoepitaxial growth requires very expensive synthetic HP/HT diamond crystals cut under a specific angle. 

It has been reported that the carbon concentration in the gas phase should also be controlled during deposition in order to achieve step-flow growth. When the carbon concentration in the gas phase exceeds the ability of the surface steps to incorporate the carbon atoms, abnormal nucleation occurs on the surface terraces, and this results in non-epitaxial growth [12]. For a (100) diamond substrate, non-epitaxial growth can be seen as a pyramidal hillock, which consists of (ill) facets [9,12]. In order to obtain homoepitaxial BDD thin films of high quality, the carbon concentration in the gas phase should be low, however, low carbon concentration also leads to a low growth rate. Therefore, the carbon concentration should be optimized and controlled [13]. 

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