The density and compositional analysis of titanium doped sapphire single crystal grown by the Czocharlski method

Titanium doped sapphire (Ti:Al2O3) crystal has attracted attention not only as beautiful gemstones, but also due to their applications as high power laser action. It is very important crystal for tunable solid state laser. Ti:Al2O3 crystals have been success grown using the Czocharlski method with automatic diameter control (ADC) system. The crystals were grown with different pull rates. The structure of the crystal was characterized with X-Ray Diffraction (XRD). The density of the crystal was measurement based on the Archimedes principle and the chemical composition of the crystal was confirmed by the Energy Dispersive X-ray (EDX) Spectroscopy. The XRD patterns of crystals are showed single main peak with a high intensity. Its shows that the samples are single crystal. The Ti:Al2O3 grown with different pull rate will affect the distribution of the concentration of dopant Ti3+ and densities on the sapphire crystals boules as well on the crystal growth process. The increment of the pull rate will increase the percentage distribution of Ti3+ and on the densities of the Ti:Al2O3 crystal boules. This may be attributed to the speed factor of the pull rate of the crystal that then caused changes in the heat flow in the furnace and then causes the homogeneities is changed of species distribution of atoms along crystal.

Source:IOPscience

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High-Temperature Hardness of Bulk Single-Crystal AlN

The hardness of single-crystal aluminum nitride (AlN) 0.5-mm-thick wafers was measured at elevated temperatures and compared with that of other semiconductors. A Vickers indentation method was used to determine the hardness under an applied load of 0.5–5 N in the temperature range 20–1400°C. The average hardness was measured as 17.7 GPa at room temperature. AlN exhibits a hardness higher than that of GaN in the entire temperature range investigated. A high mechanical stability for AlN at high temperatures is deduced.

Source:IOPscience

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The impact of subsurface damage on the fracture strength of diamond-wire-sawn monocrystalline silicon wafers

We describe a multi-diamond-wire saw for cutting monocrystalline silicon bricks into thin (120 µm) and thick (200 µm) wafers and label as fresh- and worn-wire sides. While almost no difference was found in the fracture stress of the thick wafers(200 µm) cut from either side, the thin (120 µm) wafers showed a lower fracture stress in those from the fresh-wire side compared to the worn-wire side. This is a remarkable result when wafers are sawn with conventional diamond wire. On the contrary, wafers sawn with improved diamond wire (100d-M6/12) showed a higher fracture stress compared to those cut with conventional diamond wire (100d-M8/16), for both the fresh- and worn-wire sides. Observing the subsurface areas of wafers by micro-Raman spectroscopy, we succeeded in quantifying the defective silicon fraction as the Raman crystallinity factor (Φc). We found that wafers having a higher fracture strength had a larger Φc.

Source:IOPscience

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