Scheme: Newton International Fellowships
Organisation: University of Manchester
Dates: Jan 2013-Jan 2015
Summary: Heterojunctions have played a critical role in electronic devices. The very recent discovery of a new class of materials, 2-dimensional (2D) crystals such as graphene, MoS2, WS2 and boron nitride etc., has led to the development of heterojunctions made of 2D crystals, bonded by Van der Waals (VdW) interaction. The new paradigm of heterostructures based 2D atomic crystals has already led to the observation of exciting physical phenomena and creation of novel prototype devices. The possibility of combining layers of different 2D materials in one stack allows unprecedented control over the electronic and optical properties of the resulting material. However, the performance of the device strongly depends on the quality of the interface: any interfacial strain or contamination trapped between the crystal can produce chenges in the device's characteristic. However, it is difficult to characterize an interface because this is not easily accessible. Therefore, it is essential to develop a fast, simple, non-contact and non-destructive method for accessing the interfacial VdW interaction in heterostructures.
Our strategy is to apply a “knock-listen” method based on Raman spectroscopy. This technique is already used for characterization of graphene. Here we show that this technique is also useful in investigating the interfacial interaction in heterostructure composed by other 2D crystals, such as transition methal dicalcolgenides (TMDs). This simple method allow quantifing the quality of the contact at the interface and the interfacial strain.
Our research is expected to promote the development of new and multifunctional devices based on 2D crystals, which are also compatible with low cost and flexible substrates such as plastic. This technology is expected to produce a new range of advanced products, such as flexible and low cost solar cells. Based on our work, Raman spectroscopy can be used as metrology tool in manufacturing of these devices.