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Holy Conductivity Trinity

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    Rosa Tiara


We live in a world full of objects around us. Little did we know, those objects are divided into three kinds based on their level of conductivity. Those three kinds are insulators, conductors, and semiconductors. Whilst conductivity is the principal difference between the trio, there are several other differences between them. Let’s get started!

What is conductivity and why does it matter?

Conductivity is a measurement of a matter’s ability to conduct electricity. This guy right here needs to be considered when thinking about their industrial and commercial uses.

If there’s a ranking for the trio, conductor material will take first place and sadly, the insulator will be in the last position (ah, she’s so bad at conducting electricity!). Take a look at the picture below!



The king of conductivity. Why? As you saw before, there is no gap between the valence and conduction band.

What is a valence band, seriously?

Valence band is a band of electron orbitals that electrons can jump out of and move into the conduction band when an electric field is applied. This band is the outermost electron orbital of an atom. Remember that valence electron you learned in high school? Well, the concept is quite similar!

What about the conduction band?

Based on the valence band’s definition up there, we already got the answer. Conduction band is a place for the migrated electrons that are coming from the valence band! Note that the conduction band is unfilled at the initial condition.


The electron will move from the valence band to the conduction band. When there’s no gap between the two of them, electrons can move easily. That’s why conductor materials have the best conductivity level. The examples of conductor are silver, gold, copper, and steel.


Unlike conductor, semiconductor materials do have gap between the bands. But, the gap is narrow.

How do the electrons move when there’s a gap between the bands?

They will need a small amount of voltage necessary to get them moving which is known as a cut-in voltage. Silicon needs a 1.1 eV cut-in voltage, whereas Germanium needs 0.67 eV.

The elemental semiconductors are those composed of single species of atoms, such as silicon (Si), germanium (Ge), and tin (Sn) in column IV and selenium (Se), and tellurium (Te) in column VI of the periodic table.


Insulator, such as fused quartz and glass have very low conductivities, on the order of 10-18 to 10-10 siemens per centimetre. Insulators have the widest gap between the bands. The wider the gap, the harder electron movement will be, right? Insulator needs a cut-in voltage that is greater than 5eV to help the electron move. Beside fused quartz and glass, rubber, oil, diamond, and dry wood are considered as insulator as well.

That's all for this topic! I really do hope this post helps you to gain a better understanding about semiconductor materials. Cheers!


  1. Difference Between Conductor, Semiconductor and Insulator. (2019). Retrieved 12 September 2021, from here
  2. Valence band — Energy Education. (2021). Retrieved 12 September 2021, from here
  3. Valence and conduction bands — Wikipedia. (2015). Retrieved 13 September 2021, from here
  4. semiconductor | Definition, Examples, Types, Uses, Materials, Devices, & Facts. (2021). Retrieved 13 September 2021, from here