Abstract
Systematic investigations are performed to understand the temperature-dependent optical properties of graphene on Si and SiO2/Si substrates by using a variable angle spectroscopic ellipsometry. The optical constants of graphene have revealed changes with the substrate and temperature. While the optical refractive index (n) of monolayer graphene on Si exhibited clear anomalous dispersions in the visible and near-infrared region (400–1200 nm), the modification is moderate for graphene on SiO2/Si substrate. Two graphene sheets have shown a pronounced absorption in the ultraviolet region with peak position related to the Van Hove singularity in the density of states. By increasing the temperature from 300 K to 500 K, for monolayer graphene on Si, the n value is gradually increased while k decreased. However, the optical constants [n, k] of monolayer graphene on SiO2/Si exhibited unpredictable wave variations. In the wavelength range of 400–1200 nm, an experiential formula of a like-Sellmeier equation is found well suited for describing the dispersions of graphene on Si and SiO2/Si substrates.
Highlights
Since the seminal experimental realization of one atom thick graphene sheets [1] along with the measurements of quantum Hall effect [2], a great deal of interest has emerged in both the fundamental research and the development of device engineering concepts
Graphene, being a one-atom-thick sheet of carbon exhibits significant absorption in the visible to infrared wavelength region (2.3%) with reflectance less than 0.1% [9]. This means that a one-atom-thick graphene layer is extremely transparent having a high degree of flexibility with excellent optical properties
Four graphene samples were meticulously examined by using variable angle spectroscopic ellipsometry (VASE) and variable temperature methods
Summary
Since the seminal experimental realization of one atom thick graphene sheets [1] along with the measurements of quantum Hall effect [2], a great deal of interest has emerged in both the fundamental research and the development of device engineering concepts. The Dirac Fermions in graphene has caused both integer and fractional quantum Hall effect [6]. Graphene, being a one-atom-thick sheet of carbon exhibits significant absorption in the visible to infrared wavelength region (2.3%) with reflectance less than 0.1% [9]. This means that a one-atom-thick graphene layer is extremely transparent having a high degree of flexibility with excellent optical properties
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