The structure of β-dl-methionine, C5H11NO2S, in the space group C2/c, is here confirmed to be fully ordered all the way up to the phase transition at approximately 326 K, where displacive sliding of molecular bilayers gives the disordered P21/c α form [data at 340 K; Görbitz (2014). Acta Cryst. E70, 341–343]. The geometry of hydrogen bonds in LD–LD hydrogen-bonding patterns [Görbitz et al. (2009). Acta Cryst. B65, 393–400] at the hydrophilic core of each molecular bilayer are virtually unperturbed by the phase shift, but the C—C—S—C torsion angle of the side chain changes from trans at 320 K to gauche+ for the major conformation at 340 K.
terms of the earth-abundancy of the material. More specifically, Zn-IV-N 2 with IV = Ge, Sn or Si may have a great potential for optoelectronic applications. Indeed, the direct band gap of Zn-IV-N 2 semiconductors may potentially cover the same range as that of the AlN-GaN-InN alloys, [4] and thus have the potential to be tailored to meet application-specific band gap energies. [1][2][3][5][6][7] In particular, ZnSnN 2 exhibits excellent properties for its use as the solar light absorber in photovoltaics and photocatalysts, but is less explored compared to that of ZnSiN 2 and ZnGeN 2 . According to calculations, the most energetically favorable structure for ZnSnN 2 is the orthorhombic Pna2 1 , although the orthorhombic Pmc2 1 structure has also been identified as a possible structure for ZnSnN 2 .
Fermi level controlled point defect balance is demonstrated in ion irradiated indium oxide (In 2 O 3 ). Specifically, our observations can be sub-divided into the formation of isolated Frenkel pairs and secondary defects, correlated with an increase and decrease in resistance, respectively. Importantly, by considering the net charge contribution from the most energetically stable Frenkel pair configurations, we explain the data trends for low doses and determine an upper limit for the Fermi level pinning. Moreover, by comparing the corresponding number of generated carriers with the ballistic defect generation rates, we estimate the dynamic annealing efficiency. Further irradiation toward higher doses is consistent with the buildup of secondary defects. As such, the present data may be of practical use in a variety of In 2 O 3 device applications requiring predictions of its radiation tolerance. In a broader perspective, the present methodology may be valuable for benchmarking defect simulation data in semiconductors in general.
The evolution of electrical resistance as function of defect concentration is examined for the unipolar n-conducting oxides CdO, β-Ga 2 O 3 , In 2 O 3 , SnO 2 and ZnO in order to explore the predictions of the amphoteric defect model. Intrinsic defects are introduced by ion irradiation at cryogenic temperatures, and the resistance is measured in-situ by current-voltage sweeps as a function of irradiation dose. Temperature dependent Hall effect measurements are performed to determine the carrier concentration and mobility of the samples before and after irradiation. After the ultimate irradiation step, the Ga 2 O 3 and SnO 2 samples have both turned highly resistive. In contrast, the In 2 O 3 and ZnO samples are ultimately found to be less resistive than prior to irradiation, however, they both show an increased resistance at intermediate doses.Based on thermodynamic defect charge state transitions computed by hybrid density functional theory, a model expanding on the current amphoteric defect model is proposed.
Discovering multifunctional materials is of paramount importance for advancing the science and technology. Herein, we report on an optical phenomenon modulated by an electrical process that happened at the metal-ZnO:Cu junction, for which the light emission intensity from the photoluminescence is tuned reversibly by applying electric bias to the junction. Importantly, these observations were correlated with the x-ray absorption measurements, detecting prominent flips in Cu+/Cu2+ oxidation state occupations in ZnO:Cu film as a function of the resistive switching. Moreover, further analysis of the x-ray absorption data revealed an additional prominent correlation - the signals interpreted as the Zn-O bond fingerprints also exhibited the modulations. By considering the whole set of data, we proposed a scenario explaining the modulation phenomena.
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