In Figure E6-2, which is the schematic symbol for a Schottky diode?

Explication

Symbol 6 is the diode whose cathode bar has its ends bent into opposing square hooks, forming the S shape that denotes a Schottky barrier. Symbol 3 carries the diagonally bent bar of a breakdown-reference diode, and symbols 1 and 2 carry different cathode markings again, so none of them is the Schottky device.