Emerging two-dimensional gallium chalcogenides, such as gallium telluride (GaTe), are considered promising layered semiconductors that can serve as vital building blocks towards the implementation of nanodevices in the fields of nanoelectronics, optoelectronics, and quantum photonics. However, oxidation-induced electronic, structural, and optical changes observed in ambient-exposed gallium chalcogenides need to be further investigated and addressed. Herein, we report on the thickness-dependent effect of air exposure on the Raman and photoluminescence (PL) properties of GaTe flakes, with thicknesses spanning in the range of a few layers to 100 nm. We have developed a novel chemical passivation that results in complete encapsulation of the as-exfoliated GaTe flakes in ultrathin hydrogen–silsesquioxane (HSQ) film. A combination of correlation and comparison of Raman and PL studies reveal that the HSQ-capped GaTe flakes are effectively protected from oxidation in air ambient over the studied-period of one year, and thus, preserving their structural and optical characteristics. This contrasts with the behavior of uncapped GaTe, where we observe a significant reduction of the GaTe-related PL (~100×) and Raman (~4×) peak intensities for the few-layered flakes over a period of few days. The time-evolution of the Raman spectra in uncapped GaTe is accompanied by the appearance of two new prominent broad peaks at ~130 cm−1 and ~146 cm−1, which are attributed to the formation of polycrystalline tellurium, due to oxidation of ambient-exposed GaTe. Furthermore, and by leveraging this novel passivation, we were able to explore the optical anisotropy of HSQ-capped GaTe flakes. This is caused by the one-dimensional-like nature of the GaTe layer, as the layer comprises Ga–Ga chains extending along the b-axis direction. In concurrence with high-resolution transmission electron microscopy analysis, polarization-dependent PL spectroscopy was used to identify the b-axis crystal direction in HSQ-capped GaTe flakes with various thicknesses over a range of wavelengths (458 nm–633 nm). Thus, our novel surface-passivation offers a new approach to explore and reveal the physical properties of the layered GaTe, with the potential of fabricating reliable polarization-dependent nanophotonics with structural and optical stability.

The field of semiconductor nanowires (NWs) has become one of the most active and mature research areas. However, progress in this field has been limited, due to the difficulty in controlling the density, orientation, and placement of the individual NWs, parameters important for mass producing nanodevices. The work presented herein describes a novel nanosynthesis strategy for ultrathin self-aligned silicon carbide (SiC) NW arrays (≤ 20 nm width, 130 nm height and 200–600 nm variable periodicity), with high quality (~2 Å surface roughness, ~2.4 eV optical bandgap) and reproducibility at predetermined locations, using fabrication protocols compatible with silicon microelectronics. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopic ellipsometry, atomic force microscopy, X-ray diffractometry, and transmission electron microscopy studies show nanosynthesis of high-quality polycrystalline cubic 3C-SiC materials (average 5 nm grain size) with tailored properties. An extension of the nanofabrication process is presented for integrating technologically important erbium ions as emission centers at telecom C-band wavelengths. This integration allows for deterministic positioning of the ions and engineering of the ions’ spontaneous emission properties through the resulting NW-based photonic structures, both of which are critical to practical device fabrication for quantum information applications. This holistic approach can enable the development of new scalable SiC nanostructured materials for use in a plethora of emerging applications, such as NW-based sensing, single-photon sources, quantum LEDs, and quantum photonics.

2D layered materials have attracted extensive interest due to their direct electronic bandgap, efficient light-matter coupling, and exciting anisotropic material properties. The anisotropic optical and electronic properties in these materials are vital for the creation of polarization-sensitive optoelectronic devices, such as polarization-dependent photodetectors, sensors, and sources. [1] Currently, most photodetectors provide information about the brightness and color of an object obtained from the intensity and wavelength of absorbed light. However, another fundamental property of light, the polarization of the electric field, can offer enhanced details about an image that is unobtainable from traditional thermal or visible imaging. As a result, polarization-resolved imaging has gained interest for use in applications in various fields, spanning from vehicle navigation, [2] finger printing, [3] and the study of astronomical objects [4] to facial recognition, obstacle detection, and military surveillance. [5,6] In addition, polarizationsensitive imaging has been used in the biomedical field for the study of microcirculation in humans, [7] imaging for retinal surgery, [8] and detection of cancer at early stages. [9] In addition to detection of polarized light, it is essential to control both the polarization and directionality of light emission for several applications, such as sensing, polarized light emission, and optical communication. [10,11] Resolving the polarization state of light requires additional elements that are otherwise unneeded in a photodetector, such as gratings or polarizers. Consequently, these systems require sophisticated integration schemes to enable proper alignment of these elements during device patterning. [12] Conversely, a class of 2D materials with strong inherent structural and optical anisotropy caused by their chain-formation structure extending in one crystal direction can potentially enable the fabrication of flexible stretchable polarization-sensitive devices, lifting some of the current stringent fabrication requirements. This class of materials includes transition metal monochalcogenides, GeS, [13] GeSe, [14] dichalcogenides, such as ReS 2 , [12] ReSe 2 , [15] and GeSe 2 , [16] and trichalcogenides ZrS 3 . [17] Most recently monoclinic gallium telluride (GaTe) [18][19][20] has emerged as a promising material platform for polarizationsensitive photodetection applications. The in-plane optical anisotropy behavior of monoclinic GaTe is caused by its pseudo-1D nature, as each layer comprises a chain-like structure extending along the b-axis direction. Furthermore, a study by Wang et al. [21] has reported that layered GaTe flakes exhibit in-plane anisotropic resistance and can be used to create direction-sensitive data storage devices/sensors. The measured ratios of electrical conductivity along directions parallel and perpendicular to the b-axis (chain direction) can reach up to an order of 10 3 based on the applied gate voltage. So far, no study translating these anisotropic pr...