Plasmonic Hot Electron Induced Photocurrent Response at MoS₂–Metal Junctions

Abstract

We investigate the wavelength- and polarization-dependence of photocurrent signals generated at few-layer MoS2-metal junctions through spatially resolved photocurrent measurements. When incident photon energy is above the direct bandgap of few-layer MoS2, the maximum photocurrent response occurs for the light polarization direction parallel to the metal electrode edge, which can be attributed to photovoltaic effects. In contrast, if incident photon energy is below the direct bandgap of MoS2, the photocurrent response is maximized when the incident light is polarized in the direction perpendicular to the electrode edge, indicating different photocurrent generation mechanisms. Further studies show that this polarized photocurrent response can be interpreted in terms of the polarized absorption of light by the plasmonic metal electrode, its conversion into hot electron-hole pairs, and subsequent injection into MoS2. These fundamental studies shed light on the knowledge of photocurrent generation mechanisms in metal-semiconductor junctions, opening the door for engineering future two-dimensional materials based optoelectronics through surface plasmon resonances.

Photonic Structure-Integrated Two-Dimensional Material Optoelectronics

“…Hot electron injection has been reported to be indispensable in TMDC-based devices, such as a MoS 2 -based phototransistor (Figure 2d) [78]. Anisotropic photocurrent response has been detected under illumination with photon energy below the MoS 2 bandgap.…”

“…With further investigation of 2D material optoelectronics, hot electron injection has been demonstrated as a novel photocurrent-generation mechanism [78]. It is well-known that photon-excited hot electrons in metal electrodes can cross over the Schottky barrier and be injected into the semiconductor channel.…”

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

“…Moreover, TMDs are compatible with current fabrication technologies, integration with waveguides, resonance cavities to utilize nonlinear optical phenomenon or output nanolaser, or integration with meta-surfaces, plasmon to realize special function are very promising based on TMDs. [43][44][45][46][47][48] However, most applications mentioned above are based on exfoliated samples, limited by the low yields, relative small physical size and uncontrollable layer numbers, complicated transfer methods for device fabrication, obstructing their future practical applications. Thus, the bottleneck remains the need for reliable synthesis methods for TMDs crystals with large size and high quality.…”

Photovoltaic action in a self-assembled monolayer of hemicyanine dyes on gold from dissociation of surface plasmons

“…4 Conversion of surface plasmons into electrical signals has been realized making use of, e.g., photocurrent generation involving bulk semiconductors [5][6][7][8][9] or nanowires, 10 light induced changes in the tunneling in gold quantum point contacts, 11 the thermoelectrical effect in metallic structures 12 or superconductors, 13 and hot carrier extraction in metalinsulator-metal structures. [14][15][16][17] Here, we show electrical detection of surface plasmons using self-assembled monolayers (SAMs) of hemicyanine dye molecules on gold. Short-circuit photocurrent generation using molecular monolayers has been demonstrated previously.…”

“…[15][16][17]24 The approach followed here using a junction comprised a selfassembled monolayer of organic molecules has the advantage that the junctions require only a minimal amount of space. The monolayers can be fabricated easily on complex metal electrode shapes supporting localized surface plasmons, allowing for direct incoupling of light into surface plasmons.…”