Field and Thermal Emission Limited Charge Injection in Au–C60–Graphene van der Waals Vertical Heterostructures for Organic Electronics

Abstract

Among the family of 2D materials, graphene is the ideal candidate as top or interlayer electrode for hybrid van der Waals heterostructures made of organic thin films and 2D materials due to its high conductivity and mobility and its inherent ability of forming neat interfaces without diffusing in the adjacent organic layer. Understanding the charge injection mechanism at graphene/organic semiconductor interfaces is therefore crucial to develop organic electronic devices. In particular, Gr/C60 interfaces are promising building blocks for future n-type vertical organic transistors exploiting graphene as tunneling base electrode in a two back-to-back Gr/C60 Schottky diode configuration. This work delves into the charge transport mechanism across Au/C60/Gr vertical heterostructures fabricated on Si/SiO 2 using a combination of techniques commonly used in the semiconductor industry, where a resist-free CVD graphene layer functions as a top electrode. Temperature-dependent electrical measurements show that the transport mechanism is injection limited and occurs via Fowler− Nordheim tunneling at low temperature, while it is dominated by a nonideal thermionic emission at room and high temperatures, with energy barriers at room temperature of ca. 0.58 and 0.65 eV at the Gr/C60 and Au/C60 interfaces, respectively. Impedance spectroscopy confirms that the organic semiconductor is depleted, and the energy band diagram results in two electron blocking interfaces. The resulting rectifying nature of the Gr/C60 interface could be exploited in organic hot electron transistors and vertical organic permeable-base transistors.

Electronic properties of single Prussian Blue Analog nanocrystals determined by conductive-AFM

“…The very small C-AFM contact area (about 16 nm 2 , see the ESI †) makes capacitance measurements impossible (capacitance < ∼10 −18 F) in such C-AFM/NC/HOPG devices to check whether or not the capacitance is constant with the applied voltage (as expected for the fully depleted case). However, as evidenced by combining DSB model analysis and capacitance measurements in macroscopic Schottky diodes with few tens of nanometers thick semiconducting layers, 57,58 we can reasonably assume that this is also the case for the PBA single NCs. This feature makes the comparison of the interface energy barriers between the SEL and DSB models more pertinent in the absence of band bending in the Schottky diodes.…”

Complementary Inverter Based on C60 and Pentacene Doped CVD Graphene Field Effect Transistors on SiO₂

“…The fabrication process of Graphene Field Effect Transistors (GFETs) and the deposition of C60 and Pentacene thin films are described. A more detailed description of the GFETs fabrication process, including information on the Chemical Vapor Deposition (CVD) of graphene, can be found elsewhere [5], [10], [11], [12]. Briefly, the CVD graphene foils were wet transferred on Si/SiO 2 (525 µm / 300 nm) substrates with pre-patterned Ti/Au (5 nm / 50 nm) electrodes.…”