Carbon nanotubes - University of Oxford · Carbon nanotubes 8.1 Introduction In ... In this section...

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Handout 8 Carbon nanotubes 8.1 Introduction In the last lecture we started to look at bandstructure engineering and the construction of “artificial” materials. In this section we will take a closer look at one particular nanostructure; the carbon nanotube, which is currently the focus of intense research. This system also provides us with an opportunity apply many of the techniques of bandstructure calculation that we have learnt so far. Carbon nanotubes are single sheets of graphite (called graphene ) rolled into cylinders. The diameter of the tubes are typically of nanometer dimensions, while the lengths are typically micrometers. This huge aspect ratio leads to unusual electrical transport. Notably some tubes behaving as metals and others as semiconductors. The bandstructure of graphite was first calculated by Wallace in 1947 1 , but it was not until 1991 that multi-walled nanotubes were discovered 2 . We will concentrate on single walled nanotubes which were discovered in 1993. 8.2 Reading Since carbon nanotubes are currently an area of active research the books on the subject tend to be aimed at a research audience. For those of you who would like to read more about carbon nanotubes I can recommend two books: 1. Physical properties of carbon nanotubes by Saito, Dresselhaus and Dresselhaus (Imperial College Press, 1998). 2. Carbon Nanotubes, basic concepts and physical properties by Reich, Thomsen and Maultzsch (Wiley, 2004). 8.3 Lecture slides The following 7 pages reproduce the slides shown in the lectures. 1 See P.R. Wallace Physical Review, 71: 622-634 (1947) 2 S. Iijima, Nature 354: 56-58 (1991) 61

Transcript of Carbon nanotubes - University of Oxford · Carbon nanotubes 8.1 Introduction In ... In this section...

Handout 8

Carbon nanotubes

8.1 Introduction

In the last lecture we started to look at bandstructure engineering and the construction of “artificial”materials. In this section we will take a closer look at one particular nanostructure; the carbon nanotube,which is currently the focus of intense research. This system also provides us with an opportunity applymany of the techniques of bandstructure calculation that we have learnt so far.

Carbon nanotubes are single sheets of graphite (called graphene) rolled into cylinders. The diameterof the tubes are typically of nanometer dimensions, while the lengths are typically micrometers. Thishuge aspect ratio leads to unusual electrical transport. Notably some tubes behaving as metals andothers as semiconductors.

The bandstructure of graphite was first calculated by Wallace in 19471, but it was not until 1991that multi-walled nanotubes were discovered2 . We will concentrate on single walled nanotubes whichwere discovered in 1993.

8.2 Reading

Since carbon nanotubes are currently an area of active research the books on the subject tend to beaimed at a research audience. For those of you who would like to read more about carbon nanotubes Ican recommend two books:

1. Physical properties of carbon nanotubes by Saito, Dresselhaus and Dresselhaus (Imperial CollegePress, 1998).

2. Carbon Nanotubes, basic concepts and physical properties by Reich, Thomsen and Maultzsch(Wiley, 2004).

8.3 Lecture slides

The following 7 pages reproduce the slides shown in the lectures.

1See P.R. Wallace Physical Review, 71: 622-634 (1947)2S. Iijima, Nature 354: 56-58 (1991)

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8.3. LECTURE SLIDES 69

Figure 8.1 shows the band gaps

70 HANDOUT 8. CARBON NANOTUBES

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Figure 8.1: Band gap versus lattice parameter for some of the more common semiconductors. Thecurves indicate commonly-used alloys such as (Ga,Al)As, (Ga,In)As etc.; solid curves represent directgaps and dashed curves indirect gaps.