Search

Tin monochalcogendies SnS and SnSe, belonging to a familiy of van der Waals crystals isoelectronic to black phosphorus, are know as enivornmetally-friendly materials promisng for thermoelecric conversion applications. However, they exhibit other desired functionalities, such as intrisic linear dichroism of the optical and electronic properties originating from strongly anisotropic orthorhombic crystal structure. This property makes them perfect candidats for polarization-sensitive photodetectors working in near infrared spectral range. We present a comprehensive study of the SnS and SnSe crystals by means of optical spectroscopy and photoemission spectroscopy, supported by ab initio calcualtions. The studies revealed the high sensitivity of the optical response of both materials to the incident light polarization, which we interpret in terms of the electronic band dispersion and orbital composition of the electronic bands, dictating the selection rules. From the photoemission investigation we determine the ionization potential, electron affinity and work function, which are parameters crucial for the design of devices based on semiconductor heterostructures., Comment: 10 pages of Manuscript and 6 pages of Supporting Information, 7 figures and 4 supplementary figures

Nanotechnology's impact on semiconductor industry advancement, particularly through the engineering of nanostructures like nanowires, opens new possibilities for material functionality due to the tunable physical properties of nanostructures compared to bulk materials. This paper presents a comprehensive study on group IV semiconductors and their binaries across four polytypes: 2H, 3C, 4H, and 6H, focusing on their optoelectronic application potential. Deep understanding of these polytypes is particularly relevant for nanowire-based technologies. Through first principles modeling, we examine the structural and electronic properties of these materials, emphasizing their band structure, stability, and the feasibility for light-emitting applications. We use a generalized Ising model to discuss materials stability and tendency for polytypism. We also determine relative band edge positions and employ a six $k\cdot p$ model for a detailed understanding of the materials' electronic properties. Due to the comprehensive nature of this study, we provide insight on the chemical trends present in all of the studied properties. Our theoretical predictions align well with existing experimental data, suggesting new avenues for nanostructure-based device development. The discussion extends to the implications of these findings for the fabrication of optoelectronic devices with the studied IV-IV materials, highlighting the challenges and opportunities for future research in nanowire synthesis and their application.

In this paper, we study theoretically the electron and spectral properties of Ge1-xSnx systems, including alloys, cubic- and spherical quantum dots. The single-particle electron and hole states are calculated within the sp3d5s* tight-binding approach and used in further modeling of the optical properties. We systematically study the interplay of Sn-driven indirect-direct band-gap transition and the quantum confinement effect in systems of reduced dimensionality. We demonstrate the regime of sizes and composition, where the ground state in Ge1-xSnx quantum dot is optically active. Finally, we calculate absorbance spectra in experimentally-relevant colloidal quantum dots and demonstrate a satisfactory agreement with experimental data.

In this work we derive a ready-to-use symmetry invariant expansion of the full-zone 30-band k.p Hamiltonian for the Td point group. In order to find respective parameters, the band structures of III-V materials were calculated within a state-of-the-art Density Functional Theory (DFT) approach and used next as targets to adjust the k.p bands. A satisfactory agreement of the k.p model with the DFT band structures, for all the tested zinc blende III-V semiconductors, has been achieved. Values of many of the parameters have not been known so far. We also compare the fitted k.p parameters with the values calculated using momentum matrix elements obtained directly from the DFT.