Four Probe Viva Questions

What is the Four-Point Probe method?

Answer explanation

The Four-Point Probe method is a technique used to measure the resistivity of materials by applying current through two outer probes and measuring the voltage across the inner probes.

Why is the Four-Point Probe method preferred over the Two-Point Probe method?

Answer explanation

It eliminates contact resistance effects, providing more accurate resistivity measurements.

What is resistivity? How is it different from resistance?

Answer explanation

Resistivity (ρ) is an intrinsic property of a material that quantifies its opposition to current flow, measured in ohm-meter (Ωm). Resistance (R) depends on the material's shape and size.

What is the importance of measuring resistivity in semiconductors?

Answer explanation

It helps determine material properties, doping levels, and temperature dependence, which are crucial for electronic applications.

How does temperature affect the resistivity of a semiconductor like Ge?

Answer explanation

As temperature increases, more charge carriers are thermally excited, decreasing resistivity.

What are the main components of a Four-Point Probe setup?

Answer explanation

Probe arrangement, constant current source, voltmeter, sample holder, and temperature control system.

How is the current supplied in the Four-Point Probe method?

Answer explanation

A constant DC or AC current is applied through the outer probes.

Why is germanium used in this experiment?

Answer explanation

Ge has a small band gap (~0.66 eV), making it sensitive to temperature variations.

How does temperature influence the resistivity of Ge?

Answer explanation

Higher temperatures increase carrier generation, reducing resistivity.

What is the band gap energy (E₉) of a semiconductor?

Answer explanation

What is the band gap energy (E₉) of a semiconductor?