The Structural, Electronic, and Optical Properties of Ge/Si Quantum Wells: Lasing at a Wavelength of 1550 nm

The realization of a fully integrated group IV electrically driven laser at room temperature is an essential issue to be solved. We introduced a novel group IV side-emitting laser at a wavelength of 1550 nm based on a 3-layer Ge/Si quantum well (QW). By designing this scheme, we showed that the structural, electronic, and optical properties are excited for lasing at 1550 nm. The preliminary results show that the device can produce a good light spot shape convenient for direct coupling with the waveguide and single-mode light emission. The laser luminous power can reach up to 2.32 mW at a wavelength of 1550 nm with a 300-mA current. Moreover, at room temperature (300 K), the laser can maintain maximum light power and an ideal wavelength (1550 nm). Thus, this study provides a novel approach to reliable, efficient electrically pumped silicon-based lasers

Research on accounting information sharing mechanism from the perspective of national governance

Accounting information sharing plays an important role in giving full play to the resource allocation effect of accounting information and promoting the modernization of national governance. It is one of the main tasks of the 13th five year plan for accounting reform and development of the Ministry of finance to establish a public service platform for social accounting information based on the disclosure of financial report data. In view of a series of problems brought about by the current accounting information multi submission, different caliber, mutual independence and non sharing, this paper discusses the mechanism and implementation path of accounting information sharing from the perspective of national governance, and puts forward a vertical through, horizontal interaction, internal integration and national unified accounting information sharing service system. Through the establishment of accounting information platform, accounting information can be “Count one, share resources”

Robust portfolio optimization with a generalized expected utility model under ambiguity

Robust optimization, Portfolio selection, Ambiguity, Equilibrium, C02, C44, D81,

Simulation of Ground Stress Field and Advanced Prediction of Gas Outburst Risks in the Non-Mining Area of Xinjing Mine, China

In order to predict in advance the coal and gas outburst risks in the No. 3 coal seam in the non-mining area of the Xinjing mine, the strata were divided into seven rock assemblage types based on the lithologic characteristics of strata in the research area, and eight geological profile models were constructed. The finite element methods were used to simulate the ground stress field of the No. 3 seam floor. Based on the log curve, the coal structural type of the No. 3 coal seam was identified, with the thicknesses of the coal body under different types of damage being marked off in each borehole. A damage index of the coal structure (DV) was also proposed, and the DV indexes for all boreholes were calculated. The coal and gas outburst risks in the research area were comprehensively evaluated and predicted through a superposition analysis of the spatial distribution states of three indexes, namely: ground stress, coal structure damage degree, and coal seam gas content. The results show that the equivalent stress of the No. 3 coal seam floor is usually within the range of 9–26 MPa. The high-stress zone presents a strip distribution along the northeast–southwest (NE–SW) direction. The distribution of ground stress is mainly subject to the folds and buried depth of the coal seam. The distribution range where the damage degree of the coal structure falls under Types II and III is DV ≥ 22. The gas outburst risk in the mid-southern and northeastern parts of the research area is high, whereas that in the mid-western part is low. The zones with a high and low degrees of gas outburst risks are all mainly present as strips in the NE–SW direction. The gas outburst risk in the northwest and southeast is moderate. The research results can provide guidance for gas control in non-mining areas

Room-temperature 1550-nm lasing from tensile strain N-doped Ge quantum dots on Si

© 2020 Informa UK Limited, trading as Taylor & Francis Group. N-type heavy doping and tensile strain can significantly improve the luminescence efficiency of Ge materials. The active region of the quantum dot(QD) structure can realize high luminous efficiency due to its 3D carrier confinement. In this study, we constructed a Si-based QD array laser by introducing a 0.25% biaxial tensile strain and (Formula presented.) N type heavy doping to Ge. A band-lifting method was proposed to determine the optimum doping concentration and thus improve the luminescence efficiency of Ge. To obtain accurate characteristics of the laser, we constructed a calculation model of three band transitions and all of the k-space quantum transitions of Ge and other relevant modified models. Results showed that the laser power was (Formula presented.) at a voltage of 2.5 V, and the laser wavelength reached 1519.4 nm at room temperature. The proposed laser can be used as a light source compatible with the Si-based CMOS process

Pressure-induced phase transition of nanocrystalline zinc sulfide

In situ energy dispersive X-ray diffraction measurements on nanocrystalline zinc sulfide have been performed by using diamond anvil cell with synchrotron radiation. There is a phase transition which the ultimate structure is rocksalt when the pressure is up to 16.0GPa. Comparing the structure of body materials, the pressure of the phase transition of nano zinc sulfide is high. We fit the: Birch-Murnaghan equation of state and obtained its ambient pressure bulk modulus and its pressure derivative. The bulk modulus of nanocrystalline zinc sulfide is higher than that of body materials, it indicate that the rigidity of nanocrystalline zinc sulfide is high

An investigation on the pressure-induced phase transition of nanocrystalline ZnS

An in situ energy dispersive x-ray diffraction study on nanocrystalline ZnS was carried out under high pressure up to 30.8 GPa by using a diamond anvil cell. The phase transition from the wurtzite to the zinc-blende structure occurred at 11.5 GPa, and another obvious transition to a new phase with rock-salt structure also appeared at 16.0 GPa-which was higher than the value for the bulk material. The bulk modulus and the pressure derivative of nanocrystalline ZnS were derived by fitting the Birch-Murnaghan equation. The resulting modulus was higher than that of the corresponding bulk material, indicating that the nanomaterial has higher hardness than the bulk material