A substance has a band gap of 0.85 eV at 273 K. Is this substance best classified as an insulator, a semiconductor, or a metal?

Verified step by step guidance

Understand the concept of band gap: The band gap is the energy difference between the valence band and the conduction band in a material. It determines the electrical conductivity of the material.

Classify materials based on band gap: Metals have no band gap (or a very small one), semiconductors have a moderate band gap, and insulators have a large band gap.

Recall typical band gap values: Metals typically have a band gap of 0 eV, semiconductors have a band gap ranging from about 0.5 eV to 3 eV, and insulators have a band gap greater than 3 eV.

Compare the given band gap: The substance has a band gap of 0.85 eV, which falls within the range typical for semiconductors.

Conclude the classification: Based on the band gap value of 0.85 eV, classify the substance as a semiconductor.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Band Gap

The band gap is the energy difference between the valence band and the conduction band in a material. It determines how easily electrons can be excited from the valence band to the conduction band, influencing the electrical conductivity of the material. A smaller band gap typically indicates a higher conductivity, while a larger band gap suggests insulating properties.

Classification of Materials

Materials are classified based on their electrical conductivity into three main categories: conductors (metals), insulators, and semiconductors. Conductors have no band gap, allowing free movement of electrons; insulators have a large band gap, preventing electron flow; semiconductors have a moderate band gap, enabling controlled conductivity under certain conditions, such as temperature or doping.

Temperature Effects on Band Gap

The band gap of a material can be affected by temperature. As temperature increases, the band gap may decrease due to thermal expansion and increased lattice vibrations, which can facilitate electron excitation. Understanding how temperature influences the band gap is crucial for determining the material's behavior in different conditions, particularly for semiconductors.

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Indicate if each solid forms an n-type or a p-type semiconductor.

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Does a photon of red light with a frequency of 4.29⨉10¹⁴ Hz have sufficient energy to promote an electron from the valence band to the conduction band in a sample of silicon (the band gap in silicon is 1.11 eV)?