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.

Focused Practice

I. Answer the following questions:

1. What is magnetron sputtering?

2. What is the essential element of magnetron sputtering?

3. What does the planar magnetron source provide?

4. What does a large negative bias applied to the target accelerate?

5. How are secondary electrons and sputtered atoms emitted?

6. When is the efficiency of the generation of ions improved?

7. Where are large electric fields present in magnetron sputtering?

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

III. Speak on: Magnetron sputtering.

Unit 5

Grammar: The Passive Voice

Word List:

1. strong particle-induced turbulence attenuation	ослабление сильной турбулентности (завихрения), обусловленной (наведенной, вызванной) частицами
2. wake	след (за телом в потоке), вихревая зона
3. eddy	вихревое движение, вихрь
4. particle Reynolds numbers	числа Рейнольдса для частиц
5. dissipating scales	значения рассеивания
6. center-plane	диаметральная плоскость
7. blower	нагнетатель воздуха
8. 10:1 contraction	десятикратное сужение

Particle-Induced Turbulence Attenuation

Experiments show that strong turbulence attenuation occurs with particle Reynolds numbers in the range of 10 to100. This indicates that the particles have long wakes which may have scales comparable to energy containing eddies in the flow. Distortion of eddies by these wakes is in some way responsible for the large reductions in turbulence levels. In a manner not fully understood, these wakes modify the turbulence so that energy is passed more rapidly from the energy containing eddies to the dissipating scales. This mechanism is studied by measuring the spatial structure and the dissipation rate for flows with strong particle-induced turbulence attenuation. In particular, the center-plane region of the fully-developed channel flow is examined. The experiments showed turbulence reductions by as much as a factor of 3 for particle mass loading ratios ranging up to 80 %.

The experiments were conducted in the vertical fully developed channel air-flow. The tunnel consists of an inlet and blower section, a flow conditioning section, a particle-feeding section, a 10:1contraction, a 5.2 m long development section, a test section, and a particle removal system. The particle feeding section provides a uniform and steady flow of particles that accelerate to their terminal velocity in the long development section. The development section also allows the gas flow to reach fully developed conditions. The acrylic test section has a channel half-width of
2 cm and a spanwise width of 46 cm. All experiments were conducted with a mean velocity of 10.5 m/s in the test section. The mean properties of the flow were largely unchanged by the addition of particles while the turbulence was changed substantially.

Focused Practice

I. Answer the following questions:

1. What do the experiments on turbulence show?

2. What do the particles have?

3. How do the long wakes modify the turbulence?

4. How is the mechanism studied?

5. What is examined in particular?

6. Where were the experiments conducted?

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

III. Speak on: The vertical fully developed channel air-flow.

Unit 6