{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# g_q - Experimental Problem Determination of energy band gap...

This preview shows pages 1–3. Sign up to view the full content.

1 Experimental Problem Determination of energy band gap of semiconductor thin films I. Introduction Semiconductors can be roughly characterized as materials whose electronic properties fall somewhere between those of conductors and insulators. To understan d semiconductor electronic properties, one can start with the photoelectric effect as a well -known phenomenon. The photoelectric effect is a quantum electronic phenomenon, in which photoelectrons are emitted from the matter through the absorption of sufficient energy from electromagnetic radiation (i.e. photons). The minimum energy which is required for the emission of an electron from a metal by light irradiation ( photoelectron ) is defined as " work function" . Thus, only photons with a frequency higher than a characteristic threshold, i.e. with an energy h ( h is the Planck s constant) more than the material s work function, are able to knock out the photoelectrons. Figure 1 . An illustration of photoelectron emission from a metal plate : The incoming photon should have an energy which is more than the work function of the material. In fact, the concept of work function in the photoelectric process is similar to the concept of the energy band gap of a semiconducting material. In solid state physics, the band gap g E is the energy difference between the top of the valence band and the bottom of the conduction band of insulators and semiconductors. The valence band is completely filled with electrons, while the conduction band is empty however electrons can go from the valence band to the conduction band if they acquire sufficient energy (at least equal to the band gap energy).The semiconductor's conductivity strongly depends on its energy band gap. Figure 2 . Energy band scheme for a semiconductor. Conduction band Unfilled band Filled bands E Energy Band Gap Valence b and

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 Band gap engineering is the process of controlling or altering the band gap of a material by controlling the composition of certain semiconductor alloys. Recently, it has been shown that by changing the nanostructure of a semiconductor it is possible to manipulate its band gap. In this experiment, we are going to obtain the energy band gap of a thin- film semiconduc tor containing nano-particle chains of iron oxide (Fe 2 O 3 ) by using an optical method. To measure the band gap, we study the optical absorption properties of the transparent film using its optical transmission spectrum. As a rough statement, the absorption spectra shows a sharp increase when the energy of the incident photons equals to the energy band gap. II. Experimental Setup You will find the following items on your desk: 1. A large white box containing a spectrometer with a halogen lamp. 2. A small box containing a sample, a glass substrate, a sample-holder, a grating, and a photoresistor.
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 8

g_q - Experimental Problem Determination of energy band gap...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online