Assessment of parent-subsidiary companies’ geographical distance effect on corporate social responsibility: a case of A-share listed companies

Corporate Social Responsibility (CSR) is considered as an important business agenda in the current age. Based on the data of Ashare listed companies from 2010 to 2020, this study used a fixed-effect model, heterogeneity analysis and intermediary effect test to investigate the relationship between parent-subsidiary geographical distance and CSR. Our study findings revealed that the parent-subsidiary companies’ geographic distance has a negative effect on CSR. Results of our study further indicated that the effect was more stronger for non-state-owned enterprises and the firms in the eastern region. Findings of our study also reported that the enterprise internal control had an obvious mediating effect in the association among parent-subsidiary companies’ geographic distance and CSR. The government needs to reinforce legal construction, actively guide enterprises to perform CSR through incentive measures, and implement special supervision on enterprises with a large number of subsidiaries. This study not only enriches the literature on the factors influencing corporate social responsibility but also provides a theoretical perspective and important ideas for the effective implementation of regional diversification and the improvement of CSR levels in practice

Full-Field Strain Mapping at a Ge/Si Heterostructure Interface

material

Full-Field Strain Mapping at a Ge/Si Heterostructure Interface

The misfit dislocations and strain fields at a Ge/Si heterostructure interface were investigated experimentally using a combination of high-resolution transmission electron microscopy and quantitative electron micrograph analysis methods. The type of misfit dislocation at the interface was determined to be 60° dislocation and 90° full-edge dislocation. The full-field strains at the Ge/Si heterostructure interface were mapped by using the geometric phase analysis (GPA) and peak pairs analysis (PPA), respectively. The effect of the mask size on the GPA and PPA results was analyzed in detail. For comparison, the theoretical strain fields of the misfit dislocations were also calculated by the Peierls-Nabarro and Foreman dislocation models. The results showed that the optimal mask sizes in GPA and PPA were approximately three tenths and one-tenth of the reciprocal lattice vector, respectively. The Foreman dislocation model with an alterable factor a = 4 can best describe the strain field of the misfit dislocation at the Ge/Si heterostructure interface

“Fast” Plasmons Propagating in Graphene Plasmonic Waveguides with Negative Index Metamaterial Claddings

We propose the monolayer graphene plasmonic waveguide (MGPW), which is composed of graphene core sandwiched by two graphene metamaterial (GMM) claddings and investigate the properties of plasmonic modes propagating in the waveguide. The effective refraction index of the GMMs claddings takes negative (or positive) at the vicinity of the Dirac-like point in the band structure. We show that when the effective refraction index of the GMMs is positive, the plasmons travel forward in the MGPW with a positive group velocity (vg > 0, vp > 0). In contrast—for the negative refraction index GMM claddings—a negative group velocity of the fundamental mode (vg < 0, vp > 0) appears in the proposed waveguide structure when the core is sufficiently narrow. A forbidden band appears between the negative and positive group velocity regions, which is enhanced gradually as the width of the core increases. On the other hand, one can overcome this limitation and even make the forbidden band disappear by increasing the chemical potential difference between the nanodisks and the ambient graphene of the GMM claddings. The proposed structure offers a novel scheme of on-chip electromagnetic field and may find significant applications in the future high density plasmonic integrated circuit technique

Tunable Plasmonic Talbot Effect Based on Graphene Monolayer

In this article, the plasmonic Talbot effect supported by a graphene monolayer is investigated theoretically when surface plasmon polaritons (SPPs) are excited on the graphene. The Talbot effect distance is studied by varying the chemical potential, wavelength and the period of grating. The Talbot distance increases with the period in a parabolic way, and exhibits the opposite trends with respect to the chemical potential and wavelength. Moreover, the full width at half maximum (FWHM) of the Talbot image is recorded as a function of chemical potential and the wavelength. This study provides a new approach for sub-wavelength scale imaging and extends the applications of Talbot effect as well as graphene-based plasmonic devices

Enhanced photoluminescence of multilayer Ge quantum dots on Si(001) substrates by increased overgrowth temperature

Four-bilayer Ge quantum dots (QDs) with Si spacers were grown on Si(001) substrates by ultrahigh vacuum chemical vapor deposition. In three samples, all Ge QDs were grown at 520 °C, while Si spacers were grown at various temperatures (520 °C, 550 °C, and 580 °C). Enhancement and redshift of room temperature photoluminescence (PL) were observed from the samples in which Si spacers were grown at a higher temperature. The enhancement of PL is explained by higher effective electrons capturing in the larger size Ge QDs. Quantum confinement of the Ge QDs is responsible for the redshift of PL spectra. The Ge QDs’ size and content were investigated by atomic force microscopy and Raman scattering measurements

Strain Field Mapping of Dislocations in a Ge/Si Heterostructure

Ge/Si heterostructure with fully strain-relaxed Ge film was grown on a Si (001) substrate by using a two-step process by ultra-high vacuum chemical vapor deposition. The dislocations in the Ge/Si heterostructure were experimentally investigated by high-resolution transmission electron microscopy (HRTEM). The dislocations at the Ge/Si interface were identified to be 90° full-edge dislocations, which are the most efficient way for obtaining a fully relaxed Ge film. The only defect found in the Ge epitaxial film was a 60° dislocation. The nanoscale strain field of the dislocations was mapped by geometric phase analysis technique from the HRTEM image. The strain field around the edge component of the 60° dislocation core was compared with those of the Peierls–Nabarro and Foreman dislocation models. Comparison results show that the Foreman model with a = 1.5 can describe appropriately the strain field around the edge component of a 60° dislocation core in a relaxed Ge film on a Si substrate