https://doi.org/10.1351/goldbook.V06589
Highest energy continuum of energy levels in a solid that is fully occupied by electrons at 0 K.
Notes:
  1. The
    valence
    band is lower in energy than the
    conduction band
    and is generally completely full in semiconductors. When heated, electrons from the
    valence
    band jump out of the band across the band gap and into the
    conduction band
    , making the material conductive. The
    Fermi level
    separates the
    valence
    band from the
    conduction band
    .
  2. In metals the
    valence
    band is the
    conduction band
    .
  3. Sample characterized by a (unique) sample axis Z with all directions perpendicular to Z being equivalent. In other words, the sample properties are invariant to rotation around Z. Uniaxiality exists in many anisotropic samples and simplifies the interpretation of their spectra considerably.
Source:
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 438 [Terms] [Paper]