Soil solarisation is the process of using a green house effect with plastic to kill some pathogens and weeds in the first 6 inches layer of soil. It also helps break down organic materials on the surface making them more available to plants.
Clear PV resistant plastic is used in hot regions to allow greater transmission of solar radiation to the soil, and the aim is to maintain soil temperature to 110-125 deg F for 4-6 weeks. Black plastic deflects some of the heat so you would have to do this for longer. Thinner plastic allows more energy in, but also is more easily damaged.
The process is done during summer. The soil needs to be wet before the plastic is laid down as this allows the heat to be more easily transferred through the soil. The edges of the plastic need to be dug in to prevent heat loss at the edges.