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10 december 2018

Approved FOM programme

Number 157.
Title Two-dimensional semiconductor crystals (TWOD)
Executive organisational unit BUW
Programme management Prof.dr.ir. H.J.W. Zandvliet
Duration 2015-2020
Cost estimate M€ 1.6

The objective
In this programme we aim to synthesize and characterize two-dimensional materials that have a sizeable band gap and appreciable charge carrier mobilities. We will propose, design, characterize and implement elementary field-effect based electronic devices that rely on two-dimensional semiconductors. Particular attention will be paid to (1) the opening/tuning of a band gap, (2) encapsulation, (3) field-effect characteristics, (4) artificial multilayers and (5) magnetic doping. We will focus on silicene, phosphorene and transition-metal (di)chalcogenides (e.g., molybdenum disulfide), and explore in a concerted and coherent way, new fundamental science and applications of these novel two-dimensional semiconductors.

Background, relevance and implementation
In the past decade a new exciting class of materials has been developed, which is not three-dimensional, but two-dimensional in nature. Graphene is the most famous example of this new class of materials. It exhibits a wealth of exotic and intriguing properties, which has resulted in a myriad of scientific breakthroughs. However, graphene also suffers from a severe drawback: it is gapless, implying that it cannot take over the leading role that silicon plays in the current microelectronic industry.

There are several two-dimensional materials such as silicene, phosphorene and transition-metal (di)chalcogenides that have a band gap (or band gap can be opened up in these materials). Two-dimensional semiconductors are very appealing for modern electronics, which is basically two-dimensional, as the functionality of devices is dominated by what occurs at the interfaces of semiconductors. Manipulating charge carrier densities and transport is often hindered rather than assisted by having to use bulk semiconductors. Employing two-dimensional semiconductors would enable to enter a new regime and open doors to exciting new physics and applications. We envisage these two-dimensional semiconductor crystals as the gateway to a wealth of novel and exciting phenomena with a strong potential for technological applications.

A balanced and well-chosen arsenal of experimental and theoretical techniques that includes transport measurements, scanning tunneling microscopy & spectroscopy, photoemission electron spectroscopy, low energy electron microscopy and diffraction, near edge X-ray absorption fine structure, photoluminescence and Raman spectroscopy, density functional theory and quantum many body theory calculations will used to address these tantalizing challenges.

In the starting phase of the programme, PhD students will pay visits of about 1-2 weeks to the other research groups. In addition, several experimental PhD and postdoc projects are executed in two research groups, the majority in the host group, but another part at the second location. Network meetings are held every 9-12 months at one of the research groups. The programme leader will organize an international workshop at the start and at the end of the programme in order to give an additional boost to the knowledge level and ambition of the junior scientists (PhD and postdocs) and to cement future networks and collaborations conducive to their further careers.

The final evaluation will be based on the self-evaluation report initiated by the programme leader and is foreseen for 2020.