Plasma-Enhanced Chemical Chemical Vapor Deposition has experienced a tremendous development at research and industrial levels over the past forty years. Plasma diagnostics together with plasma modelling and in-situ growth studies have provided increasing knowledge on the fundamental aspects of plasma processes and plasma surface interactions. This in turn has allowed successful development of large area photovoltaics and flat panel display industries. Yet, the range of processes and applications is often bounded by our models which tend to simplify the vast range of possibilities offered by plasmas. This is the case of silane plasmas where animated debates have mobilized the community, for example on the role of SiH₃ radicals supposed to be the best film precursor for the deposition of hydrogenated amorphous silicon (a-Si:H) and microcrystalline (µc-Si:H) thin films, owing to its low reactivity and supposed long surface diffusion. On the contrary, plasma chemistry has much more to offer, in particular the fast formation of clusters and nanocrystals which can be advantageously used as building blocks for a wide variety of materials. In this presentation I will focus on the use of process conditions where radicals as well as clusters and nanocrystals contribute to growth. Indeed, clusters and nanocrystals have been successfully used to produce polymorphous silicon thin films (pm-Si:H) [1] as well as nanocrystalline silicon oxide materials [2]. Then, I will discuss the application of pm-Si:H process conditions to c-Si substrates, which can lead to the epitaxial growth of silicon and germanium films at 175 °C and even at room temperature [3]. Even more, similar process conditions can also result in the heteroepitaxial growth of silicon and germanium on III-V materials [4], thus allowing for an easy integration of silicon and III-Vs. Moreover, adding catalyst particles such as Sn and In on the substrate has led to the growth of in-plane silicon nanowires [5] but also out of plane ones, despite the low surface tension of these metals [6]. Last but not least, we have developed remote plasma CVD for the growth of III-V materials, in particular GaN and GaAs thin films [7]. As a conclusion and perspective I would like to insist that low temperature plasmas have much more to offer than SiH₃ radicals; certainly there is still much more to explore in these fascinating systems to produce new non equilibrium materials.

 

 

1. P. Roca i Cabarrocas, Y. Djeridane, Th. Nguyen Tran, E.V. Johnson, A. Abramov and Q. Zhang. Plasma Phys. Control. Fusion 50 (2008) 124037.

2. A. J. Olivares, J. Seif, Pierre-Alexis Repecaud, Ch. Longeaud, M. Morales-Masis, M. Bivour and P. Roca i Cabarrocas. Solar Energy Materials and Solar Cells 266 (2024) 112675.

3. W. Chen, G. Hamon, R. Leal, J.-L. Maurice, L. Largeau, and P. Roca i Cabarrocas. Crystal Growth and Design 17 (2017) pp 4265–4269

4. Romain Cariou, Wanghua Chen, Jean-Luc Maurice, Jingwen Yu, Gilles Patriarche, Olivia Mauguin, Ludovic Largeau, Jean Decobert, and Pere Roca i Cabarrocas : "Low temperature PECVD epitaxial growth of silicon on GaAs : A new paradigm for III-V/Si integration". Scientific Reports 6 (2016) 25674.

5. L. Yu and P. Roca i Cabarrocas: “Growth mechanism and dynamics of in-plane solid-liquid-solid silicon nanowires”. Phys. Rev. B 81 (2010) 085323.

6. Ting Zhang, Junzhuan Wang, Linwei Yu, Jun Xu, and Pere Roca i Cabarrocas: “Advanced radial junction thin film photovoltaics and detectors built on standing silicon nanowires”. Nanotechnology 30 (2019) 302001.

7. Lise Watrin, François Silva, Cyril Jadaud, Pavel Bulkin, Jean-Charles Vanel, Erik V. Johnson, Karim Ouaras, and Pere Roca i Cabarrocas: “Direct growth of highly oriented GaN thin films on silicon by remote-plasma CVD”. Journal of Physics D: Applied Physics 57 (2024) 315106.