# Marterial Science (Chemistry Related) Problem

Material Science (Chemistry Related) Problem

I am having a hard time starting my solution to the following problem:

In a metal-oxide-semiconductor (MOS) device, a thin layer of $$SiO_2$$ (density = 2.20 $$Mg/m^3$$) is grown on a single crystal chip of silicon. How many Si atoms and how many O atoms are present per square millimeter of the oxide layer? Assume that the layer thickness is 100 nm.

So far I have been looking throughout the text book at some sample problems but the sample problems are not asking for a similar solution to this question. I have also referred to my lecture notes and have not gotten any where for quite some time. Mentally I thought that I could find the volume of the silicon oxide but I was incorrect in my mental calculations. Please help me get started.

Last edited:

CarlB
Homework Helper
From the density and thickness, you can get the mass in a square millimeter of oxide. From there, you can get the number of Si and O atoms by knowing how much these atoms weigh.

Carl

Thanks I did arrive at a solution of 2.21x$$10^{15}$$ atoms of SI and 4.41x$$10^{15}$$ atoms of O.

But What formula did you use? I did not get the same answers

yes, some clarification to this post is needed. what steps do u take to get those answers?