A high strength carbon fiber composite (CFC) wafer, and method of making such wafer, with low surface roughness comprising at least one sheet of CFC including carbon fibers embedded in a matrix. The wafer can have a thickness of between 10-500 micrometers. The wafer can have a root mean square surface roughness Rq, on at least one side, of less than 300 nm in an area of 100 micrometers by 100 micrometers and less than 500 nm along a line of 2 millimeter length. The wafer may be cut to form x-ray window support structures, MEMS, or other micrometer sized structures.