Controlling Properties of Micro-crystalline Diamond Films using Oxygen in a Hot Filament Chemical Vapour Deposition System (original) (raw)

Microcrystalline diamond (MCD) films were deposited using a conventional hotfilament chemical vapor deposition (HFCVD) system on 4" N-type Si (100) substrates at 30 mbar and 2800 watt for 20 hours. The methane and hydrogen gas flows were 3 sccm and 300 sccm, respectively while the oxygen flow was varied from 0.01 sccm to 0.04 sccm corresponding to 0.2% to 0.8% of methane. The films obtained were characterized using x-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) for their structure, quality and morphology, respectively. The resistivity was calculated by van der Pauw technique, current and voltage were measured using semiconductor device analyzer. It was found that growth rate and grain size increased gradually for higher concentrations of oxygen and resistivity decreased continuously whilst surface morphology varied significantly with the addition of O 2. The enhanced growth rate was correlated with the enhanced atomic hydrogen as well as O 2 /C 2 ratio with increasing oxygen concentration and the drop in resistivity was correlated with a rise in the local defects caused by the addition of oxygen to the CVD chamber. Low resistivity polycrystalline diamond films with larger grain size can be achieved by adding very small amount of O 2 while keeping other parameters constant. These low resistivity diamond films can be used for various electronic applications and as substrates for cells cultivation. It can also be used for bio applications such as biosensors or tissue engineering.