Polarization induced hole doping on the order of ∼1018 cm−3 is achieved in linearly graded AlxGa1−xN (x = 0.7 ∼ 1) layer grown by molecular beam epitaxy. Graded AlxGa1−xN and conventional Al0.7Ga0.3N layers grown on AlN are beryllium (Be) doped via epitaxial growth. The hole concentration in graded AlxGa1−xN:Be (x = 0.7 ∼ 1) layers demonstrates that polarization generates hole charges from Be dopant. The Al0.7Ga0.3N layer is not conductive owing to the absence of carriers generated from the Be dopant without the inducement of polarization. Polarization doping provides an approach to high efficiency p-type doping in high Al composition AlGaN.
An efficient and atom-economical methodology for the synthesis of multi-substituted carbazoles starting from α-aryl ketones and ynones under mild reaction conditions has been developed. This process goes through Cs2CO3 promoted C-C σ-bond activation of α-aryl ketones followed by highly selective C-H bond activations and C-C bond fragmentations in a one-pot operation.
An unprecedented ring expansion reaction of indolin-2-ones
with
alkynyl ketones under transition-metal-free conditions has been developed.
Base-promoted selective cleavage of a C–C σ bond of the
amide is the key in this process, which provides a straightforward
and efficient way to synthesize seven-membered-ring benzolactams or
chromone derivatives. The significant advantages of this method include
readily accessible starting materials, wide scope and functional group
tolerance, and high atom economy.
A strategy for the selective phosphonation of benzofuran and benzothiophene with trialkyl phosphites was developed. In these reactions, the C−H phosphonation of benzofurans or benzothiophenes at the C2 or C3 position with trialkyl phosphites was successfully achieved without directing groups by using a copper catalyst. Additionally, the C5 phosphonation of furan was successful under the same conditions.
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