Merging 2D and 3D Worlds for Novel Electronics: the case of Graphene/Ge(110)

The advances in electronics have been achieved by downscaling the physical size of devices’ components to the nanometer range. However, already in the late 1990s, it was clear that the dimensional scaling of silicon-based technologies had reached its limits. Therefore, to meet the requirements and expectations of future applications, novel materials need to be employed and integrated within the current infrastructure, which is mainly based on silicon.

In this scenario, two-dimensional (2D) materials might offer many advantages. Indeed, the integration of graphene, the first among 2D materials, with complementary metal-oxide semiconductor (CMOS) compatible platforms is expected to be the breakthrough point in the research field. In order to control the integration process, the properties of the interface between graphene and substrate need to be thoroughly investigated.

However, graphene presents some fundamental weaknesses. Thus, in parallel to graphene’s investigation, research on novel 2D materials beyond graphene has boosted over recent years. Therefore, this Ph.D. thesis focus on the case of graphene deposited on Ge(110) via chemical vapor deposition and potential alternatives to graphene, focusing specifically on silicene.

The thesis begins with a brief motivation for novel electronics, a background on graphene’s electronic properties, and state-of-the-art graphene/Ge interface studies. The following chapter gives an overview of the main experimental techniques used in this work. The graphene/Ge(110) interface investigation describes the system’s structural, electronic, and chemical properties.

The study is structured to induce modification in the interface by different thermal annealings in vacuum. Upon each annealing, the interface is systematically characterized with different techniques to correlate the various properties and offer the full picture of the system. The last part of the thesis focuses on potential 2D materials that could overcome the lack of bandgap in graphene.

In this regard, a brief overview of the opportunities and challenges of growing X-enes is presented. Then the focus narrows on the silicene case, and the studies on suitable substrates to support its synthesis. In this scenario, the experimental work on CaF2 grown on Si(111) is finally described.