How do color defects work in relation to a diamond's band gap?

How do color defects work in relation to a diamond's band gap?

• A. They increase the band gap, preventing absorption.
• B. They create localized states that do not affect absorption.
• C. They create energy steps within the band gap that enable visible light absorption.
• D. They cause absorption only in the ultraviolet region.

Answer: (C)

Color defects work by introducing energy states inside diamond’s wide band gap, which allows visible light to be absorbed. Diamond’s band gap is about 5.5 eV, so a perfect crystal would mostly be colorless because photons in the visible range don’t have enough energy to bridge the gap. When impurities (like nitrogen or boron) or lattice defects (such as vacancies) are present, they create discrete energy levels within that gap. Electrons can jump between these defect-related states or from the valence band to a defect state (or from a defect state to the conduction band) using photons in the visible range. This creates selective absorption of certain wavelengths, and what’s left transmitted appears colored. So the color comes from these mid-gap energy steps enabled by defects, not from widening the band gap.

Color defects work by introducing energy states inside diamond’s wide band gap, which allows visible light to be absorbed. Diamond’s band gap is about 5.5 eV, so a perfect crystal would mostly be colorless because photons in the visible range don’t have enough energy to bridge the gap. When impurities (like nitrogen or boron) or lattice defects (such as vacancies) are present, they create discrete energy levels within that gap. Electrons can jump between these defect-related states or from the valence band to a defect state (or from a defect state to the conduction band) using photons in the visible range. This creates selective absorption of certain wavelengths, and what’s left transmitted appears colored. So the color comes from these mid-gap energy steps enabled by defects, not from widening the band gap.