Group IV alloys have attracted interest in the drive to create Si compatible, direct band gap materials for implementation in complementary metal oxide semiconductor (CMOS) and beyond CMOS devices. The lack of a direct band gap in Si and Ge hinders their incorporation into optoelectronic and photonic devices, without the induction of undesirable strain. Alloying of Ge with Sn represents a novel solution to the lack of light emission in group IV compounds, with an indirect-to-direct band gap transition predicted for Ge at a Sn incorporation greater than 6.5 atom %. Recently, the initiatives on the GeSn alloy research have turned its focus to nanoforms to keep on track with the miniaturization of Si-related platforms for application in nano/ optoelectronics, photonics, and energy devices. Here, we review recent advances in the growth and application of Ge 1−x Sn x nanomaterials. An overview of the theoretical band structure calculations for Ge 1−x Sn x and the effect of band mixing is briefly explored to highlight the significance of Sn inclusion in Ge for band gap engineering. Different fabrication methods for growing Ge 1−x Sn x alloy nanostructures are delineated and correlated with thin film growth. This highlights the requirement of low-temperature and kinetically driven nonequilibrium processes for growing these metastable nanoscale alloys. The optical and electrical properties for both Ge 1−x Sn x strain-relaxed one-dimensional (1D) nanostructures and nanoparticles are reported as well as recent key research findings on Ge 1−x Sn x thin films, highlighting the potential application of these materials in photonic, nanoelectronic, and optotelectronic devices.

Background Gold nanorods (AuNRs), due to the optical and electronic properties namely the surface plasma resonance, have been developed to achieve the light-mediated photothermal therapy (PTT) for cancer. However, PTT alone may suffer from inefficient tumor killing. Recently, the combination of PTT and chemotherapy has been utilized to achieve synergistic anticancer effects. Methods In this study, AuNRs capped with hexadecyltrimethylammonium bromide (CTAB), poly(acrylic acid) (PAA), and PEGylated anisamide (a ligand known to target the sigma receptor) have been developed to produce a range of negatively charged anisamide-targeted PEGylated AuNRs (namely Au-CTAB-PAA-PEG-AA) for the combination of PTT and chemotherapy (termed as chemo-photothermal therapy [CPTT]). Epirubicin (EPI, an anthracycline drug) was efficiently loaded onto the surface of Au 800 -CTAB-PAA-PEG-AA via the electrostatic interaction forming Au 800 -CTAB-PAA-PEG-AA.EPI complex. Results The resultant complex demonstrated pH-dependent drug release, facilitated nucleus trafficking of EPI, and induced antiproliferative effects in human prostate cancer PC-3 cells. When Au 800 -CTAB-PAA-PEG-AA.EPI complex was further stimulated with desired laser irradiation, the synergistic outcome was evident in PC-3 xenograft mice. Conclusion These results demonstrate a promising strategy for clinical application of CPTT in cancer.

Here, the fabrication of a high aspect ratio (>440) Ge1−xSnx nanowires with super‐thin (≈9 nm) diameter, much below the Bohr radius, using a simple solvothermal‐like growth method under supercritical toluene conditions at a reaction temperature of 440 °C is reported. Ge1−xSnx nanowires are grown with varying amounts of Sn in Ge lattice, between 3.1 to 10.2 at%. The growth of the Ge1−xSnx alloy nanowires is achieved without any additional catalysts, and directly on current collector substrates (titanium) for application as Li‐ion battery anodes. The electrochemical performance of the binder‐free Ge1−xSnx nanowires as an anode material for Li‐ion batteries is investigated via galvanostatic cycling and detailed analysis of differential capacity plots. The dimensions of the nanowires, and the amount of Sn in Ge, are critical to achieving a high specific capacity and capacity retention. Ge1−xSnx nanowires with the highest aspect ratios and with the lowest Sn content (3.1 at%) demonstrate exceptional capacity retention of ≈90% and 86% from the 10th to the 100th and 150th cycles respectively, while maintaining a very high specific capacity value of 1176 and 1127 mAh g−1 after the 100 and 150 cycles respectively.

Ge nanowires are playing a big role in the development of new functional microelectronic modules, such as gate-all-around field-effect transistor devices, on-chip lasers and photodetectors. The widely used three-phase bottom-up growth method utilising a foreign catalyst metal or metalloid is by far the most popular for Ge nanowire growth. However, to fully utilise the potential of Ge nanowires, it is important to explore and understand alternative and functional growth paradigms such as self-seeded nanowire growth, where nanowire growth is usually directed by the in situ-formed catalysts of the growth material, i.e., Ge in this case. Additionally, it is important to understand how the self-seeded nanowires can benefit the device application of nanomaterials as the additional metal seeding can influence electron and phonon transport, and the electronic band structure in the nanomaterials. Here, we review recent advances in the growth and application of self-seeded Ge and Ge-based binary alloy (GeSn) nanowires. Different fabrication methods for growing self-seeded Ge nanowires are delineated and correlated with metal seeded growth. This review also highlights the requirement and advantage of self-seeded growth approach for Ge nanomaterials in the potential applications in energy storage and nanoelectronic devices.

Germanium (Ge) plays a crucial role in setting up important functionalities for silicon-compatible photonics. Diamond cubic germanium is an extensively studied semiconductor, although its other exotic forms, like BC8, ST8, ST12 phases, may possess distinct electronic properties. We have fabricated stable ST12-Ge nanowires via a self-seeded bottom-up three phase growth in a confined supercritical toluene environment. Here, we report on the direct evidence of the presence of the ST12 phase by a combination of Raman spectroscopy and first-principles calculations using density functional theory (DFT). It is important to remark that the DFT calculation predicts all the Raman active optical phonon modes of the P 4 3 2 1 structure, and it is in very good agreement with the experimental results. The phonon dynamics as a function of temperature is investigated through Raman measurements at temperatures varying from 80 to 300 K. First-order temperature coefficients for all the observed Raman modes are estimated from the linear temperature dependence of the phonon shifts. A complete set of isobaric Gr€ uneisen parameters is reported for all Raman modes of ST12-Ge nanowire, and the values are lower compared to the same for Si, dc-Ge bulk, and Ge nanowire. These results have important implications for understanding thermal properties of ST12-Ge nanowire.

No abstract

No abstract