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Two-dimensional van der Waals ferroelectric materials play an important role in a wide spectrum of semiconductor technologies and device applications. Integration of ferroelectrics into 2D-layered material-based devices is expected to offer intriguing working principles and add desired functionalities for next-generation electronics. Here, we investigate the electric and thermoelectric properties of thin layers of the 2H and 3R polymorphs of α -In2Se3 embedded in solid-state three-terminal devices. Charge transport measurements reveal a hysteretic behavior that can be ascribed to the effect of ferroelectric polarization at the metal electrode/2D semiconductor interfaces. The thermoelectric investigation of the same devices unveils a well-defined negative signal of the order of 100–200 μ V/K in absolute value for the 2H polymorph, showing a slight modulation as a function of the gate voltage. An analogous but noisy thermoelectric voltage is measured for devices based on the 3R polymorph, where indeed a constant finite transversal offset in the 100 μ V-few mV range is detected, which does not depend on the applied temperature gradient. We argue that these experimental observations are related to a strong residual in-plane ferroelectric polarization in the 3R α -In2Se3 polymorph thin layer. Our results show that the thermoelectric response is a fine probe of the ferroelectric character of 2D layered α -In2Se3. [ABSTRACT FROM AUTHOR]

We have investigated the thickness, the surface roughness, and the transport properties of oligo(1-(2-bisthienyl)benzene) (BTB) thin films grafted on evaporated Au electrodes, thanks to a diazonium-based electro-reduction process. The thickness of the organic film is tuned by varying the number of electrochemical cycles during the growth process. Atomic force microscopy measurements reveal the evolution of the thickness in the range of 2-27 nm. Its variation displays a linear dependence with the number of cycles followed by a saturation attributed to the insulating behavior of the organic films. Both ultrathin (2 nm) and thin (12 and 27 nm) large area BTB-based junctions have then been fabricated using standard CMOS processes and finally electrically characterized. The electronic responses are fully consistent with a tunneling barrier in case of ultrathin BTB film whereas a pronounced rectifying behavior is reported for thicker molecular films. [ABSTRACT FROM AUTHOR]

We report on low temperature conductance measurements of gold nanogaps fabricated by controlled electromigration. Fluctuations of the conductance due to quantum interferences and depending both on bias voltage and magnetic field are observed. By analyzing the voltage and magnetoconductance correlation functions, we determine the type of electron trajectories generating the observed quantum interferences and the effective characteristic time of phase coherence in our device. [ABSTRACT FROM AUTHOR]

Fabrication of three-terminal nanoscale devices is a key issue in molecular electronics to implement field-effect molecular transistor. We present in this paper two different electromigration procedures to realize metallic nanogaps at room and liquid helium temperature. A room temperature controlled electromigration process, consisting of a gradual thinning of a nanowire until the formation of a one channel contact, gives the best yield of bare nanogaps, i.e., gaps with a tunneling-like behavior. At low temperature and for a not fully controlled electromigration process, metallic clusters may remain inside the nanogap. An in-plane side gate electrode coupled to the nanogap allows transport measurements as a function of the gate voltage. Using this external tool we investigate the properties of the nanogaps, showing how clusters can mimic molecular behavior. [ABSTRACT FROM AUTHOR]

Two-dimensional van der Waals ferroelectric materials play an important role in a wide spectrum of semiconductor technologies and device applications. Integration of ferroelectrics into 2D-layered material-based devices is expected to offer intriguing working principles and add desired functionalities for next-generation electronics. Here, we investigate the electric and thermoelectric properties of thin layers of the 2H and 3R polymorphs of α -In2Se3 embedded in solid-state three-terminal devices. Charge transport measurements reveal a hysteretic behavior that can be ascribed to the effect of ferroelectric polarization at the metal electrode/2D semiconductor interfaces. The thermoelectric investigation of the same devices unveils a well-defined negative signal of the order of 100–200 μ V/K in absolute value for the 2H polymorph, showing a slight modulation as a function of the gate voltage. An analogous but noisy thermoelectric voltage is measured for devices based on the 3R polymorph, where indeed a constant finite transversal offset in the 100 μ V-few mV range is detected, which does not depend on the applied temperature gradient. We argue that these experimental observations are related to a strong residual in-plane ferroelectric polarization in the 3R α -In2Se3 polymorph thin layer. Our results show that the thermoelectric response is a fine probe of the ferroelectric character of 2D layered α -In2Se3. [ABSTRACT FROM AUTHOR]