offers a low-cost solution for high-speed interconnects for data transmission. The integration of high-quality direct-bandgap III-V lasers on Si platform is a core technology for achieving high-performance Si-based III-V optoelectronic devices, [1-3] due to the inefficient light-emitting properties of Group-IV materials. [4,5] Currently, the realization of III-V lasers on Si mainly relies on either wafer bonding or monolithic growth techniques, with the latter method being more favorable for low cost, high yield and large-scale production. [6,7] Nevertheless, the large lattice mismatch, different polarities and incompatible thermal expansion coefficients between III-V materials and Si induce various crystal defects during the epitaxial growth such as threading dislocations (TDs), inversion boundaries (IBs, often called anti-phase boundaries, APBs), and microcracks. [8-13] These defects act as non-radiative recombination centers and significantly hinder the performance of optoelectronic devices in terms of lifetime, threshold operating power and temperature performance. [2,7,14] Approaches including strained-layer superlattice (SLS) acting as a defect filter layer (DFL) and a longer cool-down period after growth were implemented to sufficiently suppress TDs and micro-cracks, respectively. [12,13,15] By contrast, IBs are electrically charged planar Monolithic integration of III-V materials and devices on CMOS compatible on-axis Si (001) substrates enables a route of low-cost and high-density Si-based photonic integrated circuits. Inversion boundaries (IBs) are defects that arise from the interface between III-V materials and Si, which makes it almost impossible to produce high-quality III-V devices on Si. In this paper, a novel technique to achieve IB-free GaAs monolithically grown on on-axis Si (001) substrates by realizing the alternating straight and meandering single atomic steps on Si surface has been demonstrated without the use of double Si atomic steps, which was previously believed to be the key for IB-free III-V growth on Si. The periodic straight and meandering single atomic steps on Si surface are results of high-temperature annealing of Si buffer layer. Furthermore, an electronically pumped quantum-dot laser has been demonstrated on this IB-free GaAs/Si platform with a maximum operating temperature of 120 °C. These results can be a major step towards monolithic integration of III-V materials and devices with the mature CMOS technology.

No abstract

A modified xanthate compound similar to xanthogen formates, S-benzoyl O-isobutyl xanthate (BIBX), was designed by introducing a carbonyl and a benzyl group into the xanthate structure. The preparation, recovery performance, and mechanism of adsorption of this compound to chalcopyrite is discussed. BIBX was synthesized using a one-pot approach with superior efficiency, which has important commercial implications. BIBX’s performance in the recovery of and mechanism of adsorption to chalcopyrite was investigated via flotation tests, adsorption quantity measurements, FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. The results show that BIBX displays a substantially stronger collecting ability toward chalcopyrite than sodium isobutyl xanthate and O-isopropyl-N-ethylthionocarbamate. Moreover, BIBX displays superior selectivity for chalcopyrite compared to pyrite. The adsorption data indicate that BIBX can be applied under slightly acidic or alkaline conditions. BIBX behaves like a bidentate ligand, bonding with the chalcopyrite copper through the thiol sulfur and carbonyl oxygen atoms. These findings are supported by FTIR and XPS data. DFT calculations predict two distinct adsorption geometries, one with one Cu atom to form a six-membered ring complex and another with two Cu atoms to form an “irregular pentagon”-shaped complex.

Supramolecular ‘gluing’ of quantum dots is demonstrated with cucurbituril and we present the opportunity to create molecular host–guest sensing schemes.