Dietrich R.T. Zahn

Nekrasova, T. D.

Rodriguez (Rodriges) Contreras, Raul David

Sheremet, E. S.

Electronic archive of Tomsk Polytechnic University

Секция 2 – Оптические технологии __________________________________________________________________________ 128  AN ALTERNATIVE SUBSTRATE FOR THE INVESTIGATION OF TWO-DIMENSIONAL MATERIALS T.D. Nekrasova*1, a, R.D. Rodriguez1, b, E.S. Sheremet1, с, Dietrich R.T. Zahn2 1National Research Tomsk Polytechnic University 30, Lenin Ave., Tomsk, 634050, Russia 2Semiconductor Physics, Chemnitz University of Technology, Chemnitz 09107, Germany atanyanekrasova09@gmai.com, braulmet@gmail.com, сjane.sheremet@gmail.com  Keywords: two-dimensional materials, van der Waals materials, substrate, graphite, Raman spectroscopy, atomic force microscopy. Abstract Since the discovery of two-dimensional materials, there is a strong research focus motivated by their unique properties. Such investigations give a way to several applications and discoveries not observed in the 2D bulk counterparts.  However, practically all research in 2D materials until now was performed with Si/SiO2 as the substrate and 2D material support by default. This research focuses on the possibility of using HOPG as a universal substrate for the future investigation of two-dimensional materials due to a number of unique properties such as chemical purity, stability, high flatness, and electrical conductivity. This study demonstrates the results of a systematic investigation with AFM, photoluminescence, and Raman spectroscopy of 2D materials deposited on HOPG and several other substrates. The obtained results show a strong interaction between HOPG and two-dimensional materials. The enhanced adhesion to HOPG allowed the instant deposition of different kinds of 2D materials that is normally not easily accomplished on SiO2. This work shows the advantages and potential of an alternative substrate that could make a significant impact in future investigation of novel 2D materials.  Introduction Since the first isolation of single layer graphene in 2004 and the recognition of this research with the award of a Nobel Prize in 2010, the number of new two-dimensional materials has grown significantly. Nowadays, there is a strong research focus on two-dimensional materials motivated by their unique properties that arise when van der Waals materials are scaled down to the single or few layers level [1]. Such physical properties are usually not observed in their 3D counterparts. These properties make them promising materials for different applications and pave the way to the future discoveries involving physical systems spatially confined in 2D. However, practically all research in 2D materials until now has been performed with SiO2/Si as the substrate and 2D material support by default. A systematic investigation of other materials as support for 2D layers is nowadays missing in the literature. Such investigation could give a way to alternative substrates with better adhesion and chemical inertness allowing a next wave of discoveries in this hot topic of layered van der Waals materials. In the present study we demonstrate that graphite offers significant advantages with respect to the usual SiO2/Si substrate due to the number of unique properties. The chemical purity and stability of the substrate, the high flatness and good conductivity properties, the possibility to deposit any kind of 2D material from multilayer to monolayers makes graphite a good choice as an alternative substrate. Materials and Methods In this study, we present the results of a systematic investigation with atomic force microscopy (AFM), current sensing AFM (CSAFM), Kelvin probe force microscopy (KPFM), photoluminescence (PL), and Raman micro-spectroscopies of GaSe, MoS2, and ZnIn2S4 deposited by mechanical exfoliation on several other substrates (SiO2, indium tin oxide, mica) and HOPG. Results  The obtained results demonstrate a strong interaction between HOPG and two-dimensional materials. The close contact between the 2D layer and graphite, readily achieved without the need of external pressure, is reflected by the direct propagation of native defects in the substrate all the way up to the top layers of the deposited 2D layer (Fig.1). We attribute this large interaction to graphite as due to van der Waals interactions Секция 2 – Оптические технологии __________________________________________________________________________ 129  between the two layered materials. The conductive nature of HOPG allowed the investigation of the transport and electronic properties of different 2D materials at the nanoscale by CSAFM and KPFM. The enhanced adhesion to HOPG allowed the instant deposition of different kinds of 2D materials that is normally not easily accomplished on SiO2. The Raman and photoluminescence spectroscopy investigations show that the pristine properties of the 2D materials are preserved despite the remarkable vdW coupling to HOPG.  Fig.1 AFM of MoS2 on HOPG Conclusions Graphite shows its potential as a good alternative to the usual SiO2/Si substrates due to a number of unique properties such as chemical purity, stability, high flatness and strong interactions with 2D materials. The obtained results make a significant impact in the future research of novel two-dimensional materials. Our research also paves the way to the investigation of 2D materials with low chemical stability (i.e.: phosphorene, silicene, and others not yet reported) which should benefit from a substrate with a large non-covalent interaction. Reference 1. Late, D. J.; Liu, B.; Matte, H. S. S. R.; Rao, C. N. R.; Dravid, V. P., Rapid Characterization of Ultrathin Layers of Chalcogenides on SiO2/Si Substrates. Advanced Functional Materials 2012, 22 (9), 1894-1905.   5 µmFew layers MoS2HOPGHeight / nm073

An alternative substrate for the investigation of two-dimensional materials

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An alternative substrate for the investigation of two-dimensional materials

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