TY - JOUR
T1 - Versatile technique for assessing thickness of 2D layered materials by XPS
AU - Zemlyanov, Dmitry Y.
AU - Jespersen, Michael
AU - Zakharov, Dmitry N.
AU - Hu, Jianjun
AU - Paul, Rajib
AU - Kumar, Anurag
AU - Pacley, Shanee
AU - Glavin, Nicholas
AU - Saenz, David
AU - Smith, Kyle C.
AU - Fisher, Timothy S.
AU - Voevodin, Andrey A.
N1 - Funding Information:
We are thankful to the scientific staff at Birck Nanotechnology Center, Purdue University for their continuous help and cooperation. We are also grateful for financial support from DOD-AFOSR-MURI (FA9550-12-1-0037).
Publisher Copyright:
© 2018 IOP Publishing Ltd.
PY - 2018/2/7
Y1 - 2018/2/7
N2 - X-ray photoelectron spectroscopy (XPS) has been utilized as a versatile method for thickness characterization of various two-dimensional (2D) films. Accurate thickness can be measured simultaneously while acquiring XPS data for chemical characterization of 2D films having thickness up to approximately 10 nm. For validating the developed technique, thicknesses of few-layer graphene (FLG), MoS2 and amorphous boron nitride (a-BN) layer, produced by microwave plasma chemical vapor deposition (MPCVD), plasma enhanced chemical vapor deposition (PECVD), and pulsed laser deposition (PLD) respectively, were accurately measured. The intensity ratio between photoemission peaks recorded for the films (C 1s, Mo 3d, B 1s) and the substrates (Cu 2p, Al 2p, Si 2p) is the primary input parameter for thickness calculation, in addition to the atomic densities of the substrate and the film, and the corresponding electron attenuation length (EAL). The XPS data was used with a proposed model for thickness calculations, which was verified by cross-sectional transmission electron microscope (TEM) measurement of thickness for all the films. The XPS method determines thickness values averaged over an analysis area which is orders of magnitude larger than the typical area in cross-sectional TEM imaging, hence provides an advanced approach for thickness measurement over large areas of 2D materials. The study confirms that the versatile XPS method allows rapid and reliable assessment of the 2D material thickness and this method can facilitate in tailoring growth conditions for producing very thin 2D materials effectively over a large area. Furthermore, the XPS measurement for a typical 2D material is non-destructive and does not require special sample preparation. Therefore, after XPS analysis, exactly the same sample can undergo further processing or utilization.
AB - X-ray photoelectron spectroscopy (XPS) has been utilized as a versatile method for thickness characterization of various two-dimensional (2D) films. Accurate thickness can be measured simultaneously while acquiring XPS data for chemical characterization of 2D films having thickness up to approximately 10 nm. For validating the developed technique, thicknesses of few-layer graphene (FLG), MoS2 and amorphous boron nitride (a-BN) layer, produced by microwave plasma chemical vapor deposition (MPCVD), plasma enhanced chemical vapor deposition (PECVD), and pulsed laser deposition (PLD) respectively, were accurately measured. The intensity ratio between photoemission peaks recorded for the films (C 1s, Mo 3d, B 1s) and the substrates (Cu 2p, Al 2p, Si 2p) is the primary input parameter for thickness calculation, in addition to the atomic densities of the substrate and the film, and the corresponding electron attenuation length (EAL). The XPS data was used with a proposed model for thickness calculations, which was verified by cross-sectional transmission electron microscope (TEM) measurement of thickness for all the films. The XPS method determines thickness values averaged over an analysis area which is orders of magnitude larger than the typical area in cross-sectional TEM imaging, hence provides an advanced approach for thickness measurement over large areas of 2D materials. The study confirms that the versatile XPS method allows rapid and reliable assessment of the 2D material thickness and this method can facilitate in tailoring growth conditions for producing very thin 2D materials effectively over a large area. Furthermore, the XPS measurement for a typical 2D material is non-destructive and does not require special sample preparation. Therefore, after XPS analysis, exactly the same sample can undergo further processing or utilization.
KW - 2D film thickness
KW - MoS film
KW - XPS thickness measurement
KW - amorphous BN film
KW - few-layer graphene
KW - non-destructive measurement
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U2 - 10.1088/1361-6528/aaa6ef
DO - 10.1088/1361-6528/aaa6ef
M3 - Article
C2 - 29323661
AN - SCOPUS:85041916161
VL - 29
JO - Nanotechnology
JF - Nanotechnology
SN - 0957-4484
IS - 11
M1 - 115705
ER -