Your selection between 1/2 and 3/4 plywood primarily depends on the design and function of your desk. For prominent sections that bear weight, like the main surface, 3/4" plywood is frequently recommended due to its superior stability and strength.
Drawer sides, fronts, and backs can be comfortably made using 1/2" plywood. If you intend to incorporate drawers, their bottoms could be effectively fabricated with 1/4" plywood. By varying plywood thickness, you can optimise your desk's strength and functionality.