layer of the atmosphere that contain ozone?

Answer 1

The ozone layer is contained mostly in the stratosphere, but is actually located at the lower layer of the stratosphere, adjacent to the troposphere. The mesosphere is situated above the stratosphere

Ozone will slowly diffuse down because it is heavy and will be destroyed in collisions when it encounters "pollutants". Expansion is not quite the right way to look at it because that implies moving into a lower pressure region. In the mixing of gasses in pressure equilibrium the movement of a molecule (diffusion) is hindered by collisions so for large distances can take a long time. So the reason that there is a layer is that is where it is created. If the creation stopped the ozone layer would disappear
"Ozone (O3) is generated when an oxygen molecule (O2) is dissociated to an oxygen atom (O) by ultraviolet light and the oxygen atom combines with an oxygen molecule (O2).
The dense ozone layer is formed at 20 - 30 kilometers above the ground. The number of oxygen molecules, which are an ingredient of ozone, decreases with increasing altitude, but the intensity of ultraviolet light, which breaks down the oxygen molecules, increases as altitude increases. According to these two factors, ozone generation becomes highest at around 20 - 30 kilometers."

Answer 2

There is ozone in several layers of the atmosphere. Are you concerned with concentration? Ozone is produced by lightning, engines which burn fossil fuel, and other sources of electricity such as some welding operations. Some of these obviously occur in the layer in which we live.

Answer 3

Ozone layer

Answer 4

Ozonosphere!