How long does it take for a valence electron being excited to conduction band?

In summary, the time it takes for a valence electron to travel from the valence band to the conduction band in silicon after being excited by one or two photons is typically around 1 fs (1x10-15 s), based on studies of electronic transitions in molecules. However, recent experiments have shown the possibility of even faster transitions with pulses as short as 0.1 fs.
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zhterran
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We know in silicon a valence electron can be excited to conduction band if it absorbs one photon(one photon absorption) or two photon(two photon absorption),my question is that it must need a certain amount of time for the electron to 'travel' from the valence band to the conduction band(I cannot imagin a instantaneously transition with zero time),then how long is that time?
 
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zhterran said:
We know in silicon a valence electron can be excited to conduction band if it absorbs one photon(one photon absorption) or two photon(two photon absorption),my question is that it must need a certain amount of time for the electron to 'travel' from the valence band to the conduction band(I cannot imagin a instantaneously transition with zero time),then how long is that time?

I am not sure about transitions in semi-conductors, but for transitions between electronic states in molecules, the timescale is typically on the order of 1 fs (1x10-15 s). Some of the most recent cutting edge experiments in molecular spectroscopy have started looking at the "motion" of the electron density in atoms and molecules after electronic transitions have been excited with an extremely short (~0.1 fs) pulse. ( For example, check out Nature 466, (2010) p. 739.)
 
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1. How does a valence electron become excited?

Valence electrons can become excited when they absorb energy from an external source, such as heat, light, or an electrical current. This causes them to jump to a higher energy level, known as the conduction band.

2. What factors affect the time it takes for a valence electron to reach the conduction band?

The time it takes for a valence electron to become excited and reach the conduction band can be influenced by several factors, including the energy of the external source, the type of material the electron is in, and any obstacles or barriers the electron may encounter.

3. Is the time it takes for a valence electron to reach the conduction band the same for all materials?

No, the time it takes for a valence electron to become excited and reach the conduction band can vary depending on the type of material. For example, metals tend to have a shorter time due to their low resistance to electron flow, while insulators have a longer time due to their high resistance.

4. Can the time it takes for a valence electron to reach the conduction band be measured?

Yes, the time it takes for a valence electron to become excited and reach the conduction band can be measured using various techniques, such as spectroscopy, time-resolved microscopy, and ultrafast laser spectroscopy. These methods allow scientists to study the movement of electrons in real-time.

5. How can understanding the time it takes for a valence electron to reach the conduction band help in research and technology?

Understanding the time it takes for a valence electron to become excited and reach the conduction band is crucial in many fields of research, such as materials science, optoelectronics, and semiconductor technology. It allows scientists to design and develop new materials and devices with specific properties, such as faster electronic conductivity or higher energy efficiency.

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