A polycrystalline diamond is formed on a substrate to form a polycrystalline diamond compact (PDC) cutter for a tool. The polycrystalline diamond has a cross-sectional dimension of at least 4 millimeters. The substrate includes tungsten carbide. An outer surface of the PDC cutter is at least partially surrounded with at least a single layer of coating by atomic layer deposition. The single layer of coating is configured to protect the PDC cutter from thermal degradation in response to exposure to a temperature greater than 700 degrees Celsius (° C.) and less than about 1050° C.