Высокотемпературная диффузия акцепторной примеси Ве в AlN

The high-temperature diffusion of an acceptor impurity of beryllium (Be) into bulk single-crystal aluminum nitride (AlN) has been studied. It is shown that the introduction of Be leads to the appearance of green luminescence of AlN, which is stable at room temperature and is observed over the entire thickness of the sample. It was shown by the method of luminescence analysis that the Be diffusion process is most efficiently realized in the temperature range from 1800°C to 2100°C and is characterized by extremely high diffusion coefficients D = 10-7 cm2/s and 10-6 cm2/s, respectively. It is shown that a prolonged diffusion process (t ≥ 1 hour) at a temperature of 2100°C leads to concentration quenching of the luminescence of near-surface AlN layers with a thickness of ≈ 80 μm, which makes it possible to estimate the concentration of beryllium impurities in the near-surface layer on the order of 10E19 cm-3.

Wet Etching in β-Ga2O3 Bulk Single Crystal

Beta-phase gallium oxide (β-Ga2O3) bulk single crystal has received increasing attentions due to their fantastic performances and widespread use in power devices and solar-blind photodetectors. Wet etching has proved to...

Optical Properties of Bulk Single-Crystal Diamonds at 80–1200 K by Vibrational Spectroscopic Methods

Bulk diamonds show great potential for optical applications such as for use in infrared (IR) windows and temperature sensors. The development of optical-grade bulk diamond synthesis techniques has facilitated its extreme applications. Here, two kinds of bulk single-crystal diamonds, a high-pressure and high-temperature (HPHT) diamond and a chemical vapor deposition (CVD) diamond, were evaluated by Raman spectroscopy and Fourier Transform Infra-Red (FTIR) spectroscopy at a range of temperatures from 80 to 1200 K. The results showed that there was no obvious difference between the HPHT diamond and the CVD diamond in terms of XRD and Raman spectroscopy at 300–1200 K. The measured nitrogen content was ~270 and ~0.89 ppm for the HPHT diamond and the CVD diamond, respectively. The moderate nitrogen impurities did not significantly affect the temperature dependence of Raman spectra for temperature-sensing applications. However, the nitrogen impurities greatly influence FTIR spectroscopy and optical transmittance. The CVD diamond showed higher transmittance, up to 71% with only a ~6% drop at temperatures as high as 873 K. This study shows that CVD bulk diamonds can be used for IR windows under harsh environments.

Gd-admixed (Lu,Gd)AlO3 single crystals: breakthrough in heavy perovskite scintillators

We report a breakthrough concept for a bulk single crystal as a heavy aluminum perovskite scintillator, where due to bandgap engineering by a balanced Gd admixture in a Lu cation sublattice, the scintillation performance dramatically increases. In an optimized composition of (Lu, Gd)AlO3:Ce (LuGdAP:Ce), the light yield approaches 21,000 phot/MeV, which is close to that of classical but much less dense YAP:Ce and 50% higher than the best LuYAP:Ce reported in the literature. Moreover, contrary to LuYAP:Ce, the LuGdAP host maintains a high effective atomic number close to that of LuAP:Ce (Zeff = 64.9), which is comparable to commercial LSO:Ce. An enormous decrease in afterglow on the millisecond time scale and acceleration in the rise time of the scintillation response further increase the application potential of the LuGdAP host. The related acceleration of the transfer stage in the scintillation mechanism due to diminishing electron trap depths is proven by thermally stimulated luminescence (TSL). Furthermore, we quantitatively characterize and model the energy transfer processes that are responsible for the change in the photoluminescence and scintillation decay kinetics of Ce3+ in the LuGdAP matrix. Such an innovative (Lu, Gd)AP:Ce scintillator will become competitive for use in applications that require heavy, fast, and high light yield bulk scintillators.

A Study on Radial and Axial Temperature Effects on the Growth of Bulk Single Crystal of SixGe1-x in Bridgman Setting

A Study on Radial and Axial Temperature Effects on the Growth of Bulk Single Crystal of SixGe1-x in Bridgman Setting

A Study on Radial and Axial Temperature Effects on the Growth of Bulk Single Crystal of SixGe1-x in Bridgman Setting

A Study on Radial and Axial Temperature Effects on the Growth of Bulk Single Crystal of SixGe1-x in Bridgman Setting

A Study on Radial and Axial Temperature Effects on the Growth of Bulk Single Crystal of SixGe1-x in Bridgman Setting

This research explores simulation of the growth of large diameter single bulk crystals of silicon and germanium alloy from its melt utilizing Bridgman method. Producing homogeneous single bulk crystals requires a good understanding of the thermo-solutal behavior in the solvent region. This study also suggests certain fundamental scientific aspects of this alloy system which are not well considered to date, and which underlie both the homogeneity and obtaining relatively flat solid liquid interface of the SixGe1-x alloy. These aspects are the diffusion and transport of silicon and germanium in the molten alloy. Both three and two dimensional numerical simulations of thermo-solutal convection in solvent region were examined. The whole simulation scheme was applied to a cylindrical model representing the sample to investigate the aforementioned phenomena in the entire process. It was found that the application of axial magnetic field had no significant effect on the buoyancy driven convection in the solvent region. However, conducting the microgravity environment simulation has shown that the removal of the gravitational force on the solvent region would result in a homogeneous solidification. As an alternative, this study has found that both axial and radial temperature gradients play a role in the solidification process. Controlling this phenomenon, along with two other factors such as applied uniform temperature and reduced pulling rate, would help achieve a homogeneous single bulk crystal with more uniform silicon distribution in the solvent region, more specifically near the solid liquid interface and produce a flat shape interface which is most desired shape in industry.