Phosphorus recovery: a need for an integrated approach

Increasing cost of phosphate fertilizer, a scarcity of high quality phosphate rock (PR)and increasing surface water pollution are driving aneed to accelerate the recovery and re-use ofphosphorus (P) from various waste sectors. Options to recover P occur all along the open P cycle from mining to households to oceans. However, P recovery as a regional and global strategy towards P sustainability and future food, bio energy and water security is in its infancy because of a number of technological, socio-economic and institutional constraints. There is no single solution and resolving these constraints requires concerted collaboration betweenrelevant stakeholders and an integrated approach combiningsuccessful business models withsocio-economic and institutional change. We suggest that an operational framework is developed for fast tracking cost-effective recovery options

1-(2-Hydr­oxy-5-methyl­phen­yl)-3-(3-methylthiophen-2-yl)prop-2-en-1-one

In the structure of the title compound, C15H14O2S, the benzene ring is nearly coplanar with the thio­phene ring. The hydroxy group substituted at C2 position is in an antiperi­planar conformation with respect to the phenyl ring. The crystal structure exhibits weak intramolecular O—H⋯O hydrogen bonding

Electron beam and optical depth profiling of quasibulk GaN

Electron beam and optical depth profiling of thick (5.5-64 mu m) quasibulk n-type GaN samples, grown by hydride vapor-phase epitaxy, were carried out using electron beam induced current (EBIC), microphotoluminescence (PL), and transmission electron microscopy (TEM). The minority carrier diffusion length, L, was found to increase linearly from 0.25 mu m, at a distance of about 5 mu m from the GaN/sapphire interface, to 0.63 mu m at the GaN surface, for a 36-mu m-thick sample. The increase in L was accompanied by a corresponding increase in PL band-to-band radiative transition intensity as a function of distance from the GaN/sapphire interface. We attribute the latter changes in PL intensity and minority carrier diffusion length to a reduced carrier mobility and lifetime at the interface, due to scattering at threading dislocations. The results of EBIC and PL measurements are in good agreement with the values for dislocation density obtained using TEM

Defects in p-GaN and their atomic structure

In this paper defects formed in p-doped GaN:Mg grown with Ga polarity will be discussed. The atomic structure of these characteristic defects (Mg-rich hexagonal pyramids and truncated pyramids) in bulk and thin GaN:Mg films grown with Ga polarity was determined at atomic resolution by direct reconstruction of the scattered electron wave in a transmission electron microscope. Small cavities were present inside the defects. The inside walls of the cavities were covered by GaN which grew with reverse polarity compared to the matrix. It was proposed that lateral overgrowth of the cavities restores matrix polarity on the defect base. Exchange of Ga and N sublattices within the defect compared to the matrix lead to a 0.6 {+-} 0.2 {angstrom} displacement between the Ga sublattices of these two areas. A [1{und 1}00]/3 shift with change from AB stacking in the matrix to BC within the entire pyramid is observe

7-(4-Chloro­phen­yl)-9-phenyl-7H-pyrrolo[3,2-e]tetra­zolo[1,5-c]pyrimidine

In the title compound, C18H11ClN6, the pyrrole, pyrimidine and tetra­zole rings form a nearly planar fused trihetrocyclic system with an r.m.s. deviation of 0.0387 (13) Å, to which the 4-chloro­phenyl group and the phenyl group are substituted at the 7 and 9 positions, respectively. The dihedral angles between the pyrrole ring and the 4-chloro­phenyl and phenyl rings are 32.1 (4) and 7.87 (7)°, respectively. In the crystal, weak inter­molecular C—H⋯N and C—H⋯Cl hydrogen bonds link the mol­ecules into a layer parallel to the (001) plane. The layers are further connected by π–π stacking inter­actions [centroid–centroid distances: 3.8413 (8) and 3.5352 (8) Å]. Intra­molecular C—H⋯N hydrogen bonds are also present

Polarity in GaN and ZnO: Theory, measurement, growth, and devices

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Rev. 3, 041303 (2016) and may be found at https://doi.org/10.1063/1.4963919.The polar nature of the wurtzite crystalline structure of GaN and ZnO results in the existence of a spontaneous electric polarization within these materials and their associated alloys (Ga,Al,In)N and (Zn,Mg,Cd)O. The polarity has also important consequences on the stability of the different crystallographic surfaces, and this becomes especially important when considering epitaxial growth. Furthermore, the internal polarization fields may adversely affect the properties of optoelectronic devices but is also used as a potential advantage for advanced electronic devices. In this article, polarity-related issues in GaN and ZnO are reviewed, going from theoretical considerations to electronic and optoelectronic devices, through thin film, and nanostructure growth. The necessary theoretical background is first introduced and the stability of the cation and anion polarity surfaces is discussed. For assessing the polarity, one has to make use of specific characterization methods, which are described in detail. Subsequently, the nucleation and growth mechanisms of thin films and nanostructures, including nanowires, are presented, reviewing the specific growth conditions that allow controlling the polarity of such objects. Eventually, the demonstrated and/or expected effects of polarity on the properties and performances of optoelectronic and electronic devices are reported. The present review is intended to yield an in-depth view of some of the hot topics related to polarity in GaN and ZnO, a fast growing subject over the last decade

Unusual luminescence lines in GaN

none11A series of sharp intense peaks was observed in the low-temperature photoluminescence spectrum of unintentionally doped GaN in the photon energy range between 3.0 and 3.46 eV. We attributed the majority of these peaks to excitons bound to unidentified structural and surface defects. Most of the structural- and surface-related peaks ~at 3.21, 3.32, 3.34, 3.35, 3.38, and 3.42 eV! were observed in Ga polar films. In N polar GaN, we often observed the 3.45 eV peak attributed to excitons bound to the inversion domain interfaces.SCOPUS 2-s2.0-0242496327 DOI: 10.1063/1.1609632M.A. RESHCHIKOV; D. HUANG; F. YUN; P. VISCONTI; L. HE; H. MORKOC; J. JASINSKI; Z. LILIENTAL-WEBER; R.J.MOLNAR; S. S. PARK; K.Y.LEEM. A., Reshchikov; D., Huang; F., Yun; Visconti, Paolo; L., He; H., Morkoc; J., Jasinski; Z., LILIENTAL WEBER; R. J., Molnar; S. S., Park; K. Y., Le

7-(4-Methoxy­phen­yl)-5-methyl-9-phenyl-7H-pyrrolo[2′,3′:4,5]pyrimido[1,6-d]tetrazole

The title compound, C20H16N6O, is composed of a tetra­zolo ring and a 4-methoxy­phenyl and a benzene-substituted pyrrole ring at the 7 and 9 positions fused to a pyrimidine ring in a nearly planar fashion [maximum deviation of 0.018 (1) Å for the fused ring system]. A methyl group at the 5 position is also in the plane of the hetero cyclic system. The dihedral angle between the mean planes of the benzene and 4-methoxy­phenyl rings is 40.4 (2)°. The dihedral angles between the mean planes of the pyrimidine and the benzene and 4-methoxy­phenyl rings are 15.6 (5)° and 52.6 (7)°, respectively. A weak intra­molecular C—H⋯N hydrogen bond inter­action, which forms an S(7) graph-set motif, helps to establish the relative conformations of the tetrazolo and benzene rings. In the crystal, weak inter­molecular C—H⋯O, C—H⋯π and π–π stacking inter­actions [centroid–centroid distances = 3.5270 (16), 3.5113 (16), 3.7275 (17) and 3.7866 (17) Å] link the mol­ecules into a two-dimensional array obliquely parallel to (101) and propagating along the b axis