Hemisphere Object
 

I want to add my video as a texture to a hemisphere...

Can someone tell me how to add a hemisphere model?
or
Can I slice the sphere into half making it look like a hemisphere? I tried this by using clipPlane() but the half of the video is not visible as it is clipped off using clipPlane().

You can create this type of model in any modeling software. Make sure to export it with a texture so that it has texture coordinates. Then you can apply the video and it should look correct.