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1. Photochemical synthesis of a zirconium cyclobutadienyl complex

   https://doi.org/10.1039/d0cc01104e  

   Đỗ, P. Minh; Akhmedov, Novruz G.; Petersen, Jeffrey L.; Dolinar, Brian S.; Milsmann, Carsten (May 2020, Chemical Communications)

   null (Ed.)

   Photolysis of ( Me PMP Me ) 2 ZrBn 2 ( Me PMP Me = 3,5-dimethyl-2-(2-pyridyl)pyrrolide) in the presence of diphenylacetylene yields the first η 4 -cyclobutadienyl zirconium complex, ( Me PMP Me ) 2 Zr(η 4 -C 4 Ph 4 ), through formal [2+2] cycloaddition of two alkynes at a putative low-valent zirconium intermediate. This unique reactivity expands the scope of alkyne coupling reactions at low-valent zirconium centers that traditionally produce zirconacyclopentadienes. 

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2. Effect of Photolysis on Zirconium Amino Phenoxides for the Hydrophosphination of Alkenes: Improving Catalysis

   https://doi.org/10.3390/photochem2010007  

   Novas, Bryan T.; Morris, Jacob A.; Liptak, Matthew D.; Waterman, Rory (March 2022, Photochem)

   A comparative study of amino phenoxide zirconium catalysts in the hydrophosphination of alkenes with diphenylphosphine reveals enhanced activity upon irradiation during catalysis, with conversions up to 10-fold greater than reactions in ambient light. The origin of improved reactivity is hypothesized to result from substrate insertion upon an n→d charge transfer of a Zr–P bond in the excited state of putative phosphido (Zr–PR2) intermediates. TD-DFT analysis reveals the lowest lying excited state in the proposed active catalysts are dominated by a P 3p→Zr 4d MLCT, presumably leading to enhanced catalysis. This hypothesis follows from triamidoamine-supported zirconium catalysts but demonstrates the generality of photocatalytic hydrophosphination with d0 metals. 

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3. Temperature dependence of cathodoluminescence emission in irradiated Si-doped β-Ga2O3

   https://doi.org/10.1063/5.0073692  

   Modak, Sushrut; Chernyak, Leonid; Schulte, Alfons; Xian, Minghan; Ren, Fan; Pearton, Stephen_J; Ruzin, Arie; Kosolobov, Sergey_S; Drachev, Vladimir_P (December 2021, AIP Advances)

   Temperature dependent continuous and time-resolved cathodoluminescence measurements were employed to understand the luminescence from Si-doped β-Ga2O3 prior to irradiation and after 10 MeV proton and 18 MeV alpha-particle irradiation. The shape and location of the luminescence components [ultraviolet luminescence (UVL′) at 3.63 eV, UVL at 3.3 eV, and blue-luminescence at 2.96 eV] obtained from Gaussian decomposition did not change in either width or peak location, indicating that new radiation-induced trap-levels were non-radiative in nature between the 4.5 and 310 K temperature range. Activation energies, associated with thermal quenching of UVL′ and UVL bands, show temperature dependence, suggesting ionization of shallow Si-donors and a thermally activated non-radiative process. 

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4. Enhancement of Er luminescence from bridge-type photonic crystal nanocavities with Er, O-co-doped GaAs

   https://doi.org/10.1364/OPTCON.501666  

   Fang, Zhidong; Tatebayashi, Jun; Homi, Ryohei; Ogawa, Masayuki; Kajii, Hirotake; Kondow, Masahiko; Kitamura, Kyoko; Mitchell, Brandon; Ichikawa, Shuhei; Fujiwara, Yasufumi (January 2023, Optics Continuum)

   A bridge-type photonic crystal (PhC) nanocavity based on Er,O-codoped GaAs is employed to realize enhancement of Er luminescence. By adjusting the structural design and measurement temperature, the cavity mode's wavelength can be coupled to Er luminescence. The peak emission intensity from an Er-2O defect center was enhanced 7.3 times at 40 nW pump power and 77 K. The experimental Q-factor is estimated to be over 1.2 × 10⁴, and the luminescence intensity shows superlinearity with excitation power, suggesting Er luminescence amplification. This result would pave the way towards the realization of highly efficient single-photon emitters based on rare-earth elements. 

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5. On the Origin of the Yellow Luminescence Band in GaN

   https://doi.org/10.1002/pssb.202200488  

   Reshchikov, Michael A. (December 2022, physica status solidi (b))

   The yellow luminescence (YL) band with a maximum at 2.2 eV is the dominant defect‐related luminescence in unintentionally doped GaN. The discovery of the mechanism responsible for this luminescence band and related defects in GaN took many years. Eventually, a consensus has been reached that the C_Nacceptor is the source of the YL band (the YL1 band) in GaN samples grown by several techniques. Previously suggested candidates, such as V_Ga, V_GaO_N, C_NO_N, and C_NSi_Ga, should be discarded. At the same time, other defects (such as the V_N, Be_Ga, and Ca_Ga) may cause luminescence bands with positions and shapes not much different from the YL1 band. In GaN containing high concentrations of gallium vacancies, oxygen, and hydrogen, complexes containing these species may also contribute in the red–yellow part of the photoluminescence spectrum. The main controversies related to the YL band are resolved. 

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