Abstract

Diamond
As an ultimate semiconductor material in future applications

D. Takeuchi'

Research Centre for Advanced Carbon Materials, National Institute of Advanced Industrial Science and Technology (AIST), Japan


What is diamond? People know it very well about one of the hardest gemstones in the world. Some of them also recognize it as one of the carbon materials such as graphite. Here you notice that only the diamond is such a gemstone as consisted of pure element, carbon, and the other gemstones is oxides. [1]

Diamond is the IV-element group indirect semiconductor material such as silicon and germanium. The band gap of it is 5.5 eV in room temperature, and it is physically, chemically stable in harsh environment. Many researchers have already demonstrated its stability in strong acids, high temperature around 1000 °C, and in radiation. The electron and hole mobility are around 2000 cm²/Vsec, and the type of major carriers start to be controlled by chemical vapour deposition (CVD). [2] Evaluating as semiconductors, diamond showed excellent scores for high power devices because of the highest thermal conductivity in all the materials. The amount of specific properties of diamond as a useful industrial material is due to the sp3 network of carbon atoms. [3]

The higher exciton (bound electron-hole pairs) binding energy (80 meV) than thermal energy in room temperature (25 meV) is promised in diamond due to its low dielectric constant and heavy effective mass of carriers. [4] Recently the strong 235 nm luminescence due to exciton recombination radiation at room temperature from CVD films were reported, and we start to study the diamond as the filed which arrows very high density of excitons at room temperature. [5] This characteristic contributes to the applications such as ultraviolet (UV) light-emitting diodes (LEDs), and UV lasers. [2]

Also hydrogenised diamond showed remarkable properties as materials. The hydrogen-terminated surface shows negative electron affinity (NEA), in which the conduction band minimum (CBM) of diamond exists over the vacuum level. [6] The hydrogenised diamond showed very high p-type conductivity even without doping of impurities, and almost ideal Schottky diodes and metal-semiconductor (MES) and/or metal-insulator-semiconductor (MIS) field-effect transistors (FETs) have already achieved. [7]

Moreover diamond is chemically inactive, pure carbon material, which is interested in as substrates for bioscience and bio industry from the viewpoint of intermediate between organic and inorganic materials. The affinity to genes of diamond has already demonstrated as genome-tips.

In this school diamond will be introduced as an ultimate semiconductor material in future applications, and reviewed the present status and future subjects.

References

[1] Ex. http://www.pbs.org/wgbh/nova/diamond/.
[2] S. Koizumi, K. Watanabe, M. Hasegawa, and H. Kanda, Science 292 1899 (2001).
[3] "Diamond: Electronic properties and applications (Ed. L. S. Pan, D. R. Kania, Kluwer Academic Publishers, Boston)" (1995).
[4] P. J. Dean, E. C. Lightowlers, and D. R. Wight, Phys. Rev. 140 A352 (1965).
[5] H. Watanabe, K. Hayashi, D. Takeuchi, S. Yamanaka, H. Okushi, and K. Kajimura, Appl. Phys. Lett. 73 981 (1998).
[6] M. W. Geis, J. C. Twichell, J. Macaulay, and K. Okano, Appl. Phys. Lett. 67 1328 (1995).
[7] H. Umezawa, K. Tsugawa, S. Yamanaka, D. Takeuchi, H. Okushi and H. Kawarada, Jpn. J. Appl. Phys., Part 2 38 L1222 (1999).