Tetrazoles. Part 36. Synthesis, Structure and Properties of 5-Nitrotetrazole.-The free 5-nitrotetrazole (II) is prepared for the first time by reaction of sodium 5-nitrotetrazolate (I) with sulfuric acid. A detailed quantum-chemical calculation of the electronic structure and some physico-chemical constants of 5-nitrotetrazole is presented. Compound (II) is shown to undergo regioselective alkylation and addition of olefins at the N 2 -position to give the 2-alkyl derivatives (IV) and (IX), respectively. With formaldehyde, the 2-hydroxymethyl derivative (XII) is formed which, despite the electron accepting 5-nitro group, undergoes alcohol-typical reactions. The 2-substituted 5-nitrotetrazoles (IV), (IX) and (XII) are shown to undergo several modifications at the 2-substituent to afford novel 5-nitrotetrazole analogues. -(KOLDOBSKII, G. I.; SOLDATENKO, D. S.; GERASIMOVA, E. S.; KHOKHRYAKOVA, N. R.; SHCHERBININ, M. B.; LEBEDEV, V. P.; OSTROVSKII, V. A.; Zh.

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We report on co-doping of high-quality AlN single crystals by group II Beryllium acceptors by means of diffusion from the vapour phase at a temperature of 1850 °C. We discovered that Be is characterized by the high diffusion length, allowing one to produce Be co-doping of sub-mm-thick AlN wafers. We show that Be diffusion led to the quenching of the visible (VIS) 450 nm (2.75 eV) and deep ultraviolet (UV) 265 nm (4.7 eV) optical absorption bands with simultaneous induction of the absorption band peaked at 248 nm (5 eV). By means of electron paramagnetic resonance (EPR), we also found that the presence of Be impurities compensated the donor type paramagnetic centers. Correlation of the EPR data with the optical absorption allowed us to conclude that Be produced in the AlN via diffusion acted predominantly as an acceptor, inducing the shift of the Fermi level to the lower part of the AlN bandgap. This shift of the Fermi level results in recharging of the deep level defects in the AlN bandgap, which explains the observed quenching of the VIS and UV absorption bands.

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