Authors: J.C. Sung and M-C Kan
Affilation: KINIK Company, Taiwan
Pages: 239 - 243
Keywords: amorphous diamond, solar cell, diamond electrode, thermal radiation, heat spreader, electroluminescence
Amorphous diamond is the only material that can emit electrons in vacuum when applied with an electrical field of only a few volts per micron and such current can increase hundreds or millions times when heated to only a few hundreds degrees centigrade. This miracle is due to amorphous diamond’s extreme atomic structure, with the highest atomic density and the largest configurational entropy. Amorphous diamond is made of carbon atoms with electrical resistivity that ranges from graphitic conductor to diamond-like insulator. But unlike ordinary composite materials that contain domains of relatively uniform material (e.g. metal and ceramic), each carbon atom in the amorphous diamond is unique in electronic bonding and energy state. In fact, amorphous diamond can be viewed as a self doped variable conductor. In comparison, semiconductors are chemically doped crystalline material. The numerous energy states in amorphous diamond can allow electrons to possess discrete energies so the inputted energy can be absorbed with a wide spectrum. Hence, even with the thermal energy may be absorbed to increase the energy of electrons. As a result, amorphous diamond can be a thermal generator, such as that for a solar cell. In this case, the energy conversion can have much higher efficiency (e.g. 50%) than that (e.g. 15%) of silicon based solar cells that can absorb only a narrow spectrum of sun light. As a solar cell, amorphous diamond has another advantage that its radiation hardness is the highest of all materials, hence, its thermal electricity efficiency will not attenuate as does the photo electrical semiconductor based solar cells.<br>An immediate application of amorphous diamond is to coat it on electron emitting electrodes, such as that used as cold cathode fluorescence lamps (CCFL) that illuminate liquid crystal displays (LCD), such is that used on note books and television sets. Amorphous diamond can dramatically reduce the voltage used to lit CCFL so the lamp life can be greatly extended. Moreover, the electrical current can be simultaneously increased to enhance the brightness of the light.