Focused Practice

I. Answer the following questions:

1. Who was the main participant of the experiment?

2. Where did the experiment take place?

3. What was the essence of that experiment?

4. What idea was the research team about to test?

5. What results did the research team expect from that experiment?

6. What was the final stage of the experiment?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: The idea of the experiment.

Unit 4 Grammar: The Complex Sentences Word List:

1. magnetron	специальная усилительная лампа
2. sputtering	распыление пучка
3. target	мишень
4. vacuum chamber	вакуумная камера
5. ground	корпус камеры
6. removal of heat	отвод тепла
7. substrate	подложка
8. bias	напряжение, подаваемое заранее
9. background gas	фоновый (уже имеющийся) газ
10. field lines	силовые линии
11. 50 mTorr	50 мторр (значение давления, показывающее степень разрежения вакуума)

Magnetron Sputtering

Magnetron and ion beam sputtering differ in the means used to create and maintain a plasma and the method used to generate and extract energetic ions from this plasma. Magnetron sputtering is a modification of diode sputtering which affords some specific advantages. The essential element of magnetron sputtering is a sputter source which serves to insulate the target from the vacuum chamber and ground, while allowing for the application of a large negative voltage to the target, and for the removal of heat from the target. In addition, the planar magnetron source provides a magnetic field which serves to confine electrons to a race track shaped region on the surface of the target. In practice the vacuum chamber is backfilled with the desired sputtering gas to a pressure typically between 1 and 50 mTorr, and a large negative bias is applied to the target. This bias accelerates any ions and electrons which are present. The ions strike the target and emit secondary electrons and sputtered atoms. The electrons, in turn, collide with neutral argon atoms resulting in ionization of the argon. This process is self-sustaining and results in the formation of a glow discharge. Since the generation of ions depends upon collisions of background gas atoms with electrons, the efficiency of this process is improved when the electrons are confined to the region near the target surface by a magnetic field. This magnetic field also has the advantage of confining the electrons which might otherwise bombard the substrate and cause excessive substrate heating. In magnetron sputtering, there are large electric fields (roughly perpendicular to the target surface) present in the region between the target and the substrates. Any negative ions, or electrons which have not been confined by the magnetic field, will accelerate along these field lines, resulting in energetic particle bombardment of the substrates.