Multilayer graphene stacks grown by different methods-thickness measurements by X-ray diffraction, Raman spectroscopy an
- PDF / 262,235 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 9 Downloads / 200 Views
ANOMATERIALS, CERAMICS
Multilayer Graphene Stacks Grown by Different Methods– Thickness Measurements by XRay Diffraction, Raman Spectroscopy and Optical Transmission1 M. Tokarczyka, G. Kowalskia, H. K¸e paa, K. Grodeckia, b, A. Drabin' skaa, and W. Strupin' skib a
. Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Hoz a 69, 00681 Warsaw, Poland b Institute of Electronic Materials Technology, Wólczyn' ska 133, 01919 Warsaw, Poland email: [email protected] Received February 22, 2013
Abstract—Xray diffraction, Raman spectroscopy and Optical absorption estimates of the thickness of graphene multi layer stacks (number of graphene layers) are presented for three different growth techniques. The objective of this work was focused on comparison and reconciliation of the two already widely used meth ods for thickness estimates (Raman and Absorption) with the calibration of the Xray method as far as Scherer constant K is concerned and Xray based WagnerAqua extrapolation method. DOI: 10.1134/S1063774513070195 1
INTRODUCTION
based estimates of the thickness of graphene layer stacks.
The structural characterization of the various graphite and graphene structures with different lateral and thickness sizes requires specific approaches and dedicated experimental procedures. Low energy elec tron diffraction (LEED) scanning tunnelling micros copy (STM), transmission electron microscopy (high resolution and standard, HRTEM, TEM) have already been the instruments of choice due to actual thickness of the graphene stacks investigated [1–3]. Xray diffraction experiments have been recently employed for the graphene studies mainly via grazing incidence Xray diffraction (GXRD, SXRD) at syn chrotron sources [4, 5]. Standard laboratory Xray equipment was only employed for multilayer graphene structures of powder type only. Our measurements are based on standard laboratory Xray source equipped with parallel beam Bragg reflection mirror and stan dard diffractometer. The procedure is based on precise measurements of substrate material supporting further growth of graphene multilayer stacks [6]. This approach allows, clearly and unanimously distinguish the Xray diffraction signal from graphene stacks which is embedded into the combined intensity of substrate and graphene layers. In our Xray measurements of d spacing and the layer thickness of graphene stacks we have used extrap olation methods of the lattice constant and thickness estimation for polycrystalline materials [7]. Xray measurements are compared with Raman spectros copy measurements as well as optical transmission 1 The article is published in the original.
SAMPLES We have chosen for our evaluation three group of samples distinguished by their growth method and/or substrate, supporting the graphene layers stack. First group was CVD grown graphene stacks on SiC substrate [8]: CVD on Si face of 4H–SiC—sam ple S1, CVD on C face of 6H–SiC—sample S2. Second group consisted of epitaxial graphene stacks grown by Si sublimation
Data Loading...
