Columnar films growth techniques

Boron-doped diamond (BDD) thin films were synthesized at CSEM (Neuchatel, Switzerland) by the hot filament chemical vapor deposition technique (HF CVD) on p-type, low-resistivity (l-3mQcm), single-crystal, silicon wafers (Siltronix). The temperature of the filament was between 2440 and 2560 °C and that of the substrate was monitored at 830 °C. The reactive gas was a mixture of 1% methane in hydrogen, containing trimethylboron as a boron source (1-3 ppm, with respect to H2). The reaction chamber was supplied with the gas mixture at a flow rate of 51 min giving a growth rate of 0.24 pm h for the diamond layer. The obtained diamond film has a thickness of about 1 pm ( 10%) and a resistivity of 15mQcm ( 30%). This HF CVD process produces columnar, random textured, polycrystalline films [9]. 

Columnar or dendritic microstructure is found also in most metal and many compound films formed by chemical vapour deposition in certain ranges of condition. As a result of the same mechanism of uninterrupted crystal growth towards the direction of material supply it is further found in films obtained by some deposition techniques from solution, particularly in electroplated films. 

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