Silicon

Silicon is a very common element. In its pure form silicon is a dark, hard, rather glassy-looking material. The sand, for example, is mostly silicon oxide, i. e. the sand is a compound of silicon and oxygen.

The silicon oxide is an insulator, and when it is necessary we can make a very thin insulation on a piece of silicon by means of controllable oxidation.

Silicon is a semiconductor. If an electric field is set up in the crystal of silicon, the electrons tend (стремиться) to move in the direction of the field and the holes tend to move in the opposite direction. Thus conduction of current in a pure silicon known as intrinsic conduction takes place. If a little impurity is added to silicon, it will become an impurity semi­conductor. The addition of impurities is a very efficient way of causing extrinsic conductivity. It appears in addition to intrinsic conductivity.

Elements of group III or group V of the Periodic Table are usually employed as impurities. These elements have either 3 or 5 valence electrons.

7. Read the text again and select the best completion for each sentence. Complete the following sentences using the multiple choice suggested. There might be more than one variant.

1. Silicon is …

1. an unknown element d) a very common element

2. a semiconductor e) an impurity semiconductor

3. a conductor

2. In its pure form silicon is …

1. light-coloured d) glassy-looking

2. hard e) dark

3. soft

3. We can make a very thin insulation on a piece of silicon by means of …

1. an electric field c) controllable oxidation

2. adding impurities d) placing it into another environment

4. Elements which are usually employed as impurities have either…

1. 3 or 5 valence electrons c) 3 or 6 valence electrons

2. 2 or 4 valence electrons d) 2 or 5 valence electrons

5. Elements of group III or group V of the Periodic Table are…

1. antimony e) copper

2. indium f) phosphorus

3. ferrum j) gallium

d) aluminium

7. Complete the sentences with the correct ending according to the text.

1. The sand is mostly …

2. The silicon oxide is …

3. If an electric field is set up in the crystal of silicon, the electrons tend to …

4. Conduction of current in a pure silicon is known as …

5. If a little impurity is added to silicon, it …

6. The addition of impurities is a very efficient way of …

7. Extrinsic conductivity appears in addition to …

8. Elements of group III or group V of the Periodic Table are usually …

9. These elements have …

10. They are …

Speaking

7. Summarize the text “Silicon” in 150 words.

7. Translate the text “Applications of Silicon” paying attention to new technical terms in writing. Applications of Silicon

As the second most abundant element in the earth's crust, silicon is vital to the construction industry as a principal constituent of natural stone, glass, concrete and cement. The greatest impact of silicon on the modern world's economy and lifestyle has resulted from silicon wafers used as substrates in the manufacture of discrete electronic devices such as power transistors, and in the development of integrated circuits such as computer chips.

• Alloys

The largest application of metallurgical grade silicon, representing about 55% of the world consumption, is in the manufacture of aluminium-silicon alloys to produce cast parts, mainly for the automotive industry. Silicon is an important constituent of electrical steel, modifying its resistivity and ferromagnetic properties. Silicon is added to molten cast iron as ferrosilicon or silicocalcium alloys to improve its performance in casting thin sections, and to prevent the formation of cementite at the surface.

• Electronics

Pure silicon is used to produce ultra-pure silicon wafers used in the semiconductor industry, in electronics and in photovoltaic applications. Ultra-pure silicon can be doped with other elements to adjust its electrical response by controlling the number and charge (positive or negative) of current carriers. Such control is necessary for transistors, solar cells, integrated circuits, microprocessors, semiconductor detectors and other semiconductor devices which are used in electronics and other high-tech applications. In silicon photonics, it can be used as a continuous wave Raman laser medium to produce coherent light, though it is ineffective as a light source. Hydrogenated amorphous silicon is used in the production of low-cost, large-area electronics in applications such as LCDs, and of large-area, low-cost thin-film solar cells.