As a kind of wide band gap semiconductor, diamond is undoubtedly the most attractive application prospect in optoelectronics.However, due to the certain difficulties in n-type diamond semiconductor doping, the preparation of homogeneous junction is more difficult. At present, the leading research on diamond film P-N junction is still conducted by MIT. Koizumi et al. of MIT first prepared diamond film P-N junction in 2001.On the (111) face of diamond single crystal with homogeneous epitaxial growth method of preparation of the two layers of diamond film, p-type semiconductor element B doped diamond film, n-type semiconductor with p element doped preparation, then they for this device was improved, and in the case of applying 20 v bias circuit, device are out of the uv light, and points out that,The device can operate at high temperatures.
Alexov A et al. prepared A layer of n-doped diamond film on the b-doped diamond film by homoepitaxy method, but they did not report the electroluminescence and other characteristics of this P-N junction in detail.Later reports on homogenous junction are not common, which may be mainly due to the difficulty in the repeatability of diamond N-type semiconductor doping. Current reports are focused on heterogenous junction of diamond semiconductor, for example, diamond film containing B has been grown on Si wafer.Or make Schottky diodes (Schottky diodes) and Field effect transistors (Fets).
The surface of diamond was treated by hydrogen plasma sputtering to form hydrogen terminal surface.In 1989,Landstrass first reported that hydrogen terminal surfaces exhibited P-type conductivity, and others later confirmed this finding.In 1997,Hayashi et al. found that after hydrogen surface treatment of b-containing diamond film, the surface electrical properties of the film also showed the same change rule as that of undoped diamond.Hydrogen terminal diamond materials have been studied as field emission transistors for more than 10 years. The MIT team analyzed the emission surface of diamond for the first time, and found the electron emission characteristics near the Fermi level after B doping and N doping.Then they prepared diamond materials for field emission cathode, investigated the contact current between metal and diamond, and proposed the mechanism of diamond's electron release in vacuum.
Diamonds have a very high SEE coefficient, which was confirmed in the 1990s.Diamond sizes have been reduced from the micron to the nanometer scale.In the early 1990s, an experimental study was conducted on the SEE properties of diamond films, and it was found that the SEE coefficient of diamond films was relatively large (up to 10).Subsequently, the SEE properties of different doped diamond films were studied. In the case of cesium doping, the SEE coefficient of diamond films was as high as 55 at 5kV.In the late 1990s, the SEE coefficient of hydrogenated diamond films was studied, and it was found that the hydrogenated diamond films had higher SEE coefficient than the cesium-doped diamond films.
In the early 21st century, the United States Naval Laboratory conducted an experimental study on the SEE coefficient of diamond film, and found that the secondary electron transmission coefficient of diamond film could reach 10 under the condition of more than 10 kv.At present, the biggest problem of SEE is the instability of hydrogenated diamond film. Many reports in recent years focus on the damage of hydrogenated surface caused by different factors.
IIEE has an important defect, which is easy to lead to the graphitization of diamond. Although it is pointed out that diamond has good IIEE characteristics and has great application potential in plasma display, it is still an important research bottleneck to find suitable bombardment ions to avoid the graphitization of diamond.
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