# Why do we need to add hydrogen to amorphous silicon?

I was recently studying about Staebler-Wronski effect observed in amorphous silicon (a-Si). I realised it was due to imperfections in the lattice structure and breaking of Si-Si bond to Si-H bonds.

So if hydrogen atoms will be less the effect will be minimum. Why do we add hydrogen atoms to a-Si?

Is is just to passivate the unsaturated Si atoms at the edges, or am I missing something?

• You are essentially correct. You need to passionate any unsatisfied bonds. – Jon Custer Dec 30 '18 at 17:37
• @JonCuster xD my goodness... – Mithoron Dec 30 '18 at 18:28
• @Mithoron - Sigh... stupid auto correct. I sense a (niche) market for a technical spell check dictionary... – Jon Custer Dec 30 '18 at 18:29
• @JonCuster Oh no! T'is a thing of beauty :D – Mithoron Dec 30 '18 at 18:35

Or one adds it accidentally / coincidentally by using a deposition technique or raw material that contains hydrogen. ($$\ce{SiH4}$$ or $$\ce{SiH_xCl_{4-x}}$$). But you can usually thermocycle these problems away, as long as your substrate can handle it. If you did it, accidentally, on a plastic surface - it is usually referred to as "scrap" and recycled...