We report on the fabrication of buried cannel waveguides in Sapphire crystals by 250-kHz high repetition rate ultrafast laser inscription with 385 nm pulses. The propagation properties of the waveguides were studied as a function of the writing conditions. The micro-fluorescence analysis of the R lines generated by trace Cr(3+) dopant in Sapphire is used to elucidate the micro-structural modifi...

Gallium nitride light emitting diodes were deposited on a sapphire substrate that was pre-patterned with an ordered two-dimensional structure. The size and arrangement of the substrate surface pattern was designed to increase the diffraction and extraction of light from the device as well as define the grain size and thus dislocation density of the GaN crystal. A close-packing of self-assembled...

A sapphire backscattering monochromator with 1.1 (1) meV bandwidth for hard X-rays (20-40 keV) is reported. The optical quality of several sapphire crystals has been studied and the best crystal was chosen to work as the monochromator. The small energy bandwidth has been obtained by decreasing the crystal volume impinged upon by the beam and by choosing the crystal part with the best quality. T...

We report on the growth of planar semipolar (101̄1) GaN on (112̄3) pre-patterned sapphire. This method allows the growth of semipolar oriented (101̄1) GaN on large scale. By x-ray diffaction, only the peaks of the desired (101̄1) plane could be observed. The in-plane orientations could be determined as [0001]GaN ‖ [0001]sapphire and [112̄0]GaN ‖ [101̄0]sapphire. Scanning electron microscopy, transmis...

This paper presents a study on laser intensity distributions where field enhancements occur due to scattering by spherical sapphire particles and under conditions of different wavelengths and substrate media. A sapphire micro particle concept is employed to determine the effects of light–particle interaction with a particle refractive index approaching 2 (n ≤ 2). Mie scattering software is used...

This study reports a non-destructive method of measuring the residual strain in the GaN epilayer grown on sapphire substrate by micro-Raman spectroscopy. Operating in confocal mode this method allows a depth-dependent measurement of residual strain in the epitaxial layer without prior treatment of the sample. This approach to measurement of residual strain is demonstrated on GaN epitaxial films...

Polyaminoboranes [N(R)H-BH2]n (1: R = H, 2: R = Me) were pyrolyzed on a range of substrates: silicon, metal foils (stainless steel, nickel, and rhodium), and sapphire wafers, as well as on Al2O3 and AlN powders. The pyrolysis of 2 on a Si-wafer resulted in porous nanostructures containing hexagonal-boron nitride (h-BN). In the case of 1 or H3N·BH3 as precursor, using rhodium foil as substrate a...

Influence of sapphire pretreatment conditions on crystalline quality of AlN epilayers has been investigated by metal organic chemical vapor deposition (MOCVD). Compared to alumination treatment, it is found that appropriate sapphire nitridation significantly straightens the surface atomic terraces and decreases the X-ray diffraction (0002) full width at half maximum (FWHM) to a minimum of 55 ar...

Single-crystal aluminas are being considered for use in the manufacture of prosthetic heart valves. To characterize such materials for biomedical application, subcritical crack growth by stress corrosion (static fatigue) and by cyclic fatigue has been examined in sapphire along (1100) planes in 24 degrees C humid air and 37 degrees C Ringer's solution (the latter as a simulated physiological en...