Introduction:
A Schottky diode is a type of diode that is formed by the junction of a metal and a semiconductor material, typically silicon. It is named after the German physicist Walter H. Schottky.

Explanation:
In a Schottky diode, the silicon layer acts as the cathode. To understand why, let's look at the structure and working principle of a Schottky diode.

Structure of a Schottky Diode:
A Schottky diode consists of a metal layer and a semiconductor layer. The metal layer is typically made of a transition metal such as platinum, titanium, or tungsten, while the semiconductor layer is usually made of silicon. The metal layer forms a rectifying junction with the semiconductor layer.

Working Principle:
The working principle of a Schottky diode is based on the rectifying properties of the metal-semiconductor junction. When a forward bias voltage is applied to the diode (positive voltage on the metal side and negative voltage on the semiconductor side), electrons from the semiconductor layer are attracted to the metal layer. This creates a flow of current through the diode. On the other hand, when a reverse bias voltage is applied (negative voltage on the metal side and positive voltage on the semiconductor side), the flow of current is significantly reduced due to the barrier formed by the metal-semiconductor junction.

Role of the Silicon Layer:
In a Schottky diode, the silicon layer acts as the cathode. The cathode is the electrode through which the current flows out of the device. In this case, when a forward bias voltage is applied, the electrons from the silicon layer are attracted to the metal layer, resulting in a flow of current from the silicon layer to the metal layer. Therefore, the silicon layer is considered the cathode.

Conclusion:
In a Schottky diode, the silicon layer acts as the cathode. This is because the silicon layer is the electrode through which the current flows out of the device when a forward bias voltage is applied. The metal layer, on the other hand, acts as the anode, which is the electrode through which the current flows into the device.