Ricerc@Sapienza

Two-dimensional semiconductors, also known as van der Waals semiconductors, are one of the most studied class of materials of the last decade by the scientific community. The reasons reside in the appealing potential applications in different fields of technology, like fast electronics and opto-electronic devices. However, the use of these materials for infrared and terahertz applications has not been intensively investigated so far. With this project, we intend to complete the fabrication and the full characterization of a prototype of a mid-infrared detector made with two-dimensional semiconductors, i.e. MoS2 and InSe. As it has been done in III-V quantum well infrared photodetectors, the detection mechanism is based on optical transitions between the discrete levels arising when the thickness of a material approaches the monolayer limit. In fact, the potential well given by the thin material gives rise to a series of quantum bound states for the electronic wavefunctions. The optical transitions between these states, known as intersubband transitions, fall in the infrared range of the electromagnetic spectrum. By exploiting these transitions, we propose to fabricate an opto-electronic device based on vertical MoS2/InSe heterostructures for mid-infrared detection. The vertical MoS2/InSe heterostructure should allow the flow of current through the device only when the infrared radiation shines on the heterostructure. In this way, we will be able to detect mid-infrared radiation. The use of van der Waals semiconductors can be advantageous for their unique mechanical properties, i.e. extreme flexibility and in-plane flatness, the cleanness of the surface in the few-layer limit, and the absence of lattice-mismatch requirements. This work is relevant for the knowledge of the infrared response of van der Waals materials but mostly for the future development of infrared and terahertz technology based on two-dimensional materials.