Plasmon-induced efficient hot carrier generation in graphene on gold ultrathin film with periodic array of holes: Ultrafast pump-probe spectroscopy

Abstract

Using ultrafast pump-probe reflectivity with 3.1 eV pump and coherent white light probe (1.1 to 2.6 eV), we show that graphene on gold nanostructures exhibits a strong coupling to the plasmonic resonances of the ordered lattice hole array, thus injecting a high density of hot carriers in graphene through plasmons. The system being studied is single-layer graphene on ultrathin film of gold with periodic arrangements of holes showing anomalous transmission. A comparison is made with gold film with and without hole array. By selectively probing transient carrier dynamics in the spectral regions corresponding to plasmonic resonances, we show efficient plasmon induced hot carrier generation in graphene. We also show that due to high electromagnetic field intensities at the edge of the sub-micron holes, fast decay time (10-100 fs) and short decay length (1 nm) of plasmons, a highly confined density of hot carriers (very close to edge of the holes) is generated by Landau damping of plasmons within the holey gold film. A contribution to transient decay dynamics due to diffusion of initial non-uniform distribution of hot carriers away from the hole edges is observed.Our results are important for future applications of novel hot carrier device concepts where hot carriers with tunable energy can be generated in different graphene regions connected seamlessly. 1 I. INTRODUCTION Surface plasmon polaritons (SPPs) due to their inherent property of nanoscale confinement and localization, smaller than the interacting light wavelength, show strong lightmatter interaction. This leads plasmonics to a wide variety of applications from efficient harvesting of solar energy to nanoscale optical devices [1-3]. Efficient generation and transfer of hot electron-hole pairs has been at the heart of efficient conversion of solar energy in photovoltaic and photocatalytic devices [4]. Plasmons in nanostructures decay through Landau damping (with damping time of few tens of fs [5-8]) to generate energetic electrons, with energies larger than those of the thermal excitation (known as the hot electrons) at ambient temperatures, [9-14]. Hot carriers can be accessed through plasmon induced hot-electron charge transfer into adjacent interface material [7, 10, 15, 16]. If a high conductance pathway is available, the plasmon generated hot electrons can rapidly conduct over long distances, which might also discourage the electrons once transferred from returning to the plasmonic material. In graphene, electrons move with high velocities (v F =10 6 m/s) and behave like massless Fermions, making it the most desirable material for the high-speed electronics and optoelectronics applications. A substantial challenge to the performance of most of the graphene-based optoelectronic devices [17-19] comes from the weak absorption of light (only 2.3% at normal incidence) in graphene. Thus, efficient hot electron injection in graphene through plasmons gains valuable importance. Graphene in a hybrid plasmonic structure are promising elements for high-speed electrica...

Graphene/WS2 Nanodisk Van der Waals Heterostructures on Plasmonic Ag Nanoparticle-Embedded Silica Metafilms for High-Performance Photodetectors

“…Comparing the two spectra shown in Figure d, the G and 2D Raman peaks of graphene with AgNPs are enhanced by 16 and 3 times, respectively. This plasmonic enhancement is consistent with that reported previously. ,− It should be noted that the Raman enhancement factors of the graphene peaks depend on the frequencies of the vibrational modes . Therefore, the enhancement factors of the graphene G and 2D peaks are anticipated to be different .…”

Photocurrent of Graphene/Au-Nanopillar: Near-Unity Degree of Linear Polarization

“…For comparison, the spectrum of the Gr monolayer on a SiO 2 /Si substrate (Gr/SiO 2 ) is also included in Figure . The G and 2D peaks in each sample, located at about 1580 and 2690 cm –1 , respectively, indicate the preparation of the Gr monolayer. ,, The single Lorentzian shape of the 2D peak is a feature of the Gr monolayer. , The low-intensity peak at 1350 cm –1 is attributed to the D band of carbon, suggesting that few defects are formed during the growth and transfer processes. , The 2D and G peaks of Gr/SiO 2 and Gr/AuF have an intensity ratio of 1.8, which confirms the single layer of Gr. ,, The Raman intensity of the 2D peak of Gr/AuNP is enhanced up to 70-fold by AuNP, compared with that of Gr/AuF. Such enhancement may result from the plasmonic effects of AuNP .…”

“…15,31 The low-intensity peak at 1350 cm −1 is attributed to the D band of carbon, suggesting that few defects are formed during the growth and transfer processes. 15,30 The 2D and G peaks of Gr/SiO 2 and Gr/AuF have an intensity ratio of 1.8, which confirms the single layer of Gr. 9,11,15 The Raman intensity of the 2D peak of Gr/AuNP is enhanced up to 70-fold by AuNP, compared with that of Gr/ AuF.…”

“…The G and 2D peaks in each sample, located at about 1580 and 2690 cm −1 , respectively, indicate the preparation of the Gr monolayer. 26,29,30 The single Lorentzian shape of the 2D peak is a feature of the Gr monolayer. 15,31 The low-intensity peak at 1350 cm −1 is attributed to the D band of carbon, suggesting that few defects are formed during the growth and transfer processes.…”

Enhancement of wide-band trace terahertz absorption spectroscopy based on microstructures: a review

“…As a special electromagnetic wave mode formed by the collective oscillation of electrons on the surface of metals, semiconductors or graphene materials, SPP can break through the diffraction limit, greatly enhancing the electromagnetic field distribution at deep sub-wavelength structures, and achieving enhanced absorption of trace-amount analytes. SPP devices based on various gold nanostructures in the infrared band, such as antenna array structures, 56 triangular array structures 57 and circular hole array structures, 58 have been widely used in surface-enhanced infrared absorption spectroscopy technology. For achieving characteristic absorption in the material with a small volume, metasurfaces have gained attention.…”