Semi-Conductors come in many different forms (e.g Bronze, Ruby, Gold, Diamiond), that depending on their level are found in various places. Bronze are usually well hidden in the environment of Dead Space 2 and can usually be found by exploring rooms that aren't highlighted by the story "line" you are suppose to follow or even easy to miss places. For example towards the start of the game when passing through the vacuum on your right keep moving through and eventually you will see a semi-conductor floating in space which you will use kenesis to grab. Not only will exploring all possible rooms nab you these, but precious ammo and health packs as well which are essential on higher difficulties. Gold and Ruby Semi-Conductors are most commonly found in rooms you need a power node to access. I, personally always keep one on me for situations such as these since again, these rooms give sometimes a much needed resupply and for many of the rooms I encountered another power node is either near or sometimes even in these rooms. Rubys can be found on the very tough enemies such as Brutes. By Chapter 8 I nabbed this achievement by just searching power node rooms, killing tough enemies, and a few from exploring the world of Dead Space 2. Finally the ever elusive but oh so rewarding Diamond. I admit at one point I was frantically running around and trying not to die and picking up all I could so I am not 100% where I picked this up, but if someone wants to comment and give the information Ill post it up! All I know is that these are very very rare and by Chapter 10 I have only come across one of these. Anyways I hope this helps you all nabbing those semi-conductors and keep those guns loaded and your health high!