No abstract

Alloying Ge with Sn is one of the promising ways for achieving Si compatible optoelectronics. Here, GeSn nanowires (NWs) are realized via nano-crystallization of a hydrogenated amorphous Ge (a-Ge:H) layer with the help of metal Sn droplets. The full process consists of three steps: (1) SnO2 nanoparticle (NP) reduction in a hydrogen plasma to produce Sn catalyst; (2) a-Ge:H deposition at 120 °C and (3) annealing. GeSn alloys with rich morphologies such as discrete nanocrystals (NCs), random, and straight NWs were successfully synthesized by changing process conditions. We show that annealing under Ar plasma favors the elaboration of straight GeSn NWs in contrast to the conventional random GeSn NWs obtained when annealing is performed under a H2 atmosphere. Interestingly, GeSn in the form of discrete NCs can be fabricated during the deposition of a-Ge:H at 180 °C. Even more, the synthesis of out-of-plane GeSn NWs has been demonstrated by reversing the deposition sequence of SnO2 NPs and a-Ge:H layer.

Due to their innocuity, Au nanowires present an interesting field of applications in biology and, particularly, in cancer therapy. Since their morphology and distribution can greatly affect their performances, being able to control their mode of growth is important. Various elaboration techniques including "top-down" and "bottom-up" approaches have been developed. In this work, we propose an efficient maskless method to grow Au nanowires with the help of hydrogen plasma treatment of Au thin films. We have been able to grow Au nanowires by taking advantage of spinodal dewetting of an Au thin film and the supply of silicon radicals resulting from hydrogen plasma etching of amorphous silicon coating the walls of the reactor. A variety of techniques have been applied to study the microstructure and the optical properties of Au nanowires. A strong photothermal effect of Au nanowires has been demonstrated with the help of visible laser light. In order to study the nanowire growth, the transport of Au atoms is discussed and a growth mechanism is proposed.

No abstract

Research on Si compatible direct bandgap semiconductors is a hot topic due to the high demand of Si compatible optoelectronics. The group IV compounds, namely GeSn, has been studied extensively in its different forms: thin films, nanowires (NWs), and nanocrystals. Importantly, the attention being paid to GeSn NWs has increased in recent years thanks to two key factors: 1) better crystalline quality due to an easier strain relaxation in NWs; and 2) extraordinary Sn content (up to 30 at.%) associated to a very fast NW growth (>20 nm s−1). Therefore, to effectively control the growth of GeSn NWs is a key issue for a practical application. Herein, various control aspects including the nature of the catalysts, the morphology of the NWs, and their Sn content are presented.