Home-grown diamond using CVD I want to make a diamond at home using chemical vapor deposition (CVD). 


If I use a metal chamber filled with methane and hydrogen gas and heated with a microwave oven oscillator element, will the gas explode? 
What is the ratio of methane and hydrogen for the diamond to be able grow?
The easiest way to grow diamond through chemical vapor deposition (CVD) is on a heated filament, which just takes a few watts. 

You'd need a low-pressure chamber (~30 torr, or ~0.04 atm) with gas-tight fittings for electricity, feed-gas of ~1% $\ce{CH4}$ and ~99% $\ce{H2}$ and $\ce{Cu}$, $\ce{Ti}$, $\ce{W}$ or $\ce{Ta}$ filaments. Since this is a flow-though reactor, you'll also need to dispose of the flammable feed-gas without letting it accumulate near the vacuum pump.

N.B. This is not a simple project one could do at home, since you'd need vacuum equipment, pressure regulators, high-pressure bottles* of these highly flammable gases, and a vacuum-vessel which could implode. If you can get a knowledgeable instructor involved who has access to laboratory facilities and a thorough understanding of safety procedures, though, it's not impossible to accomplish.  

* One of the greatest dangers would be a gas bottle falling, taking off like a rocket and leaving explosive gas in its wake!