Photochromism has been studied for irradiated type Ib diamonds which are then annealed above 1500 "C. This mainly involves H2 and H3 centres. When the samples are illuminatedwithlightofwavelengthshorterthan 600 nm, absorption of H2centresis reduced while thatofH3centresisenhanced. In thedark the processisreversed. Severalcharacteristic features have been examined for various illumination conditions and different samples. O n the basis of the results a model is proposed: H2 and H 3 centres are the same centre with different chargestates andphotoionizationofH2maybe responsibleforthephotochromism,
High-quality synthetic type IIa diamond crystals of several carats, containing less than 0.1 ppm chemical impurities and few inclusions, have been successfully synthesized by the temperature gradient method under high pressure and high temperature. The crystals are transparent over a wide range of wavelengths from ultraviolet to far infrared regions, showing no absorptions due to impurities.They also have high crystalline quality with fewer crystal defects, less internal strain, and less variation in defects among crystals than those of natural diamonds or conventional synthetic type Ib diamond. The outstanding characteristics of the synthetic type IN diamond permit application to a considerably wide range of industrial and scientific uses such as optical parts, monochromators, high-pressure anvils, and so on.[synthetic diamond, high pressure, crystal growth, impurity, dislocation]
Superconducting Y-Ba-Cu-O thin films have been prepared by RF magnetron sputtering on Si(100) substrate with a buffer layer of ZrO2 or MgO. The film with a ZrO2 buffer layer exhibited a superconductive transition with zero resistance at 82 K. X-ray diffraction patterns indicated a preferential orientation where c-axes were perpendicular to the substrate.
We have investigated the crystalline properties and surface morphology of the buffer layers of Y2O3, ZrO2 and Y2O3/ZrO2 on a Si(100) substrate for a superconducting thin film. The results of RHEED and X-ray diffraction indicate the hetero-epitaxial growth of buffer layers on Si(100) substrates. Epitaxial planes of the buffer layers on the Si(100) surface are (110), (100) and (100)/(100) for Y2O3, ZrO2 and Y2O3/ZrO2, respectively. YBa2Cu3O7-x
thin films have been grown on Si with each buffer layer. The highest critical temperature obtained was 88 K on the Si with the Y2O3/ZrO2 buffer layer.
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