- •Unit 7 The Movement of Holes Language Work
- •Present Perfect Passive (measurements have been done)
- •Fill in the gaps in the descriptions of the figures using the words from the table above where possible and the following verbs: break, free, move, come, occur.
- •Open the brackets and complete the dialogues with just, already, yet.
- •Put in become, broken, begun or come.
- •You are asking students questions about things they have done. Make questions with ever using the words in brackets.
- •Complete b’s answers. Some sentences are positive and some negative. Use the following verbs: write, use, design, interest, experiment, read.
- •Read the situations and write sentences using the example.
- •Complete these sentences with the following verbs (in the form of Present Perfect Passive).
- •Rewrite these sentences into the passive voice.
- •Make sentences from the words in brackets using the Present Perfect Passive.
- •Form adjectives from the following nouns using the suffix – ous and translate them.
- •Read and translate word-combinations.
- •Start from the first component:
- •Start from the second component:
- •Match the following sentences with their translations.
- •Choose as many words from the table of ex.1 as you can and form sensible sentences.
- •Specialist Reading
- •Read the text “The Movement of Holes”. Mark the following sentences as true (t) or false (f).
- •The Movement of Holes
- •Read the text again and complete the sentences with the correct ending.
- •Work in pairs. Ask your partner some questions based on the text. Make sure you use the correct auxiliary verb.
- •Summarize the text “The Movement of Holes” in 100 words using the following plan:
- •Translate the text, which contains additional information about electron-
- •Measuring the Movement of Holes in Crystal Surfaces
- •Speaking
- •Describe the process of recombination to your group mate using active terms of the Unit and the Present Perfect.
- •Try to work as an interpreter. Translate the explanation of the way the
- •Divide into two groups. Group a translates text a “Education”, group b translates text b “Science and Innovation" with a dictionary in writing. Text a education
The Movement of Holes
If a silicon crystal is heated, the breaking of covalent bonds is taking place. Figures of exercise 2 in Unit 7 show what occurs in the atoms of the crystal. In one figure we see that one covalent bond has broken, one electron has freed itself, and a hole has appeared at point A. In the next figure we see that a second hole at point B has appeared. Now there are two free electrons. The second electron is passing the first hole. It has been attracted by the hole and there is no hole at point A. It seems that the hole has moved from position A to position B.
Then we see that the third electron has freed itself and recombination has taken place at some other point where the hole has disappeared.
The movement of electrons and holes is random.
But if some voltage is applied, then the electrons begin to move in one direction and the holes begin to move in the opposite direction. Thus, conduction may take place in a pure semiconductor. Such a conduction is known as intrinsic conduction. The increase of temperature of the semiconductor increases its conductivity.
Read the text again and complete the sentences with the correct ending.
If a silicon crystal is heated, …
As a result of breaking of one covalent bond, one electron …
The second electron is passing the first hole and it …
The third electron has freed itself and …
If some voltage is applied …
The conduction which takes place in a pure semiconductor is known as …
The increase of temperature of the semiconductor …
Work in pairs. Ask your partner some questions based on the text. Make sure you use the correct auxiliary verb.
For example:
The breaking of covalent bonds takes place (Where?)
Where does the breaking of covalent bonds take place?
In one figure we see that one covalent bond has broken (What … next?) — …
If some voltage is applied, then the electrons begin to move (How?) — …
The increase of temperature changes the features of a semiconductor (How?) — …
Conduction may take place in (Where?) — …
Summarize the text “The Movement of Holes” in 100 words using the following plan:
The description of Figure 1.
The description of Figure 2.
The description of Figure 3.
The description of Figure 4.
Intrinsic conduction.
Changes of conductivity under specific conditions.
Translate the text, which contains additional information about electron-
hole movement with a dictionary in writing. Pay attention to the new
words for you and to the use of the Present Perfect.
Measuring the Movement of Holes in Crystal Surfaces
Vacancies in crystal surfaces are holes where atoms are missing from otherwise regular and uniform crystal lattices. Scientists have suspected for some time that vacancies are responsible for motion in crystals.
This motion occurs as the holes trade places with atoms, leading to atom-sized bubbles that percolate across crystal facets.
Now, researchers at the University of Leiden in the Netherlands have managed to measure vacancy motion in a copper crystal, and they have found that the holes are surprisingly mobile.
The discovery has important implications for the semiconductor industry and technologies that rely on tiny surface structures that may be gradually destroyed through vacancy mediated motion.
The researchers used a scanning tunneling microscope (STM) to study vacancy motion by monitoring the positions of indium atoms embedded in a copper lattice.
Because vacancies move rapidly, changing places with atoms roughly a hundred million times each second at room temperature, comparatively slow STMs cannot image vacancies directly. Instead, the researchers calculated vacancy motion by tracking the positions of the indium atoms.
From one image to another, indium atoms exhibited long jumps which result from multiple vacancy interactions. Essentially, the indium atoms move across the copper crystal in much the same way that individual pieces may be maneuvered from one place to another in toys known as slide puzzles.
Although high vacancy mobility may be bad news for manufacturers of microstructures, the new insights will potentially help to optimize crystal growing procedures vital to the semiconductor industry.
In future work, the researchers plan to create vacancies artificially by selectively removing atoms from a chilled crystal surface. Provided that crystal is sufficiently cooled, the vacancies should move slowly enough to show up in STM images.