Millivolt range thermovoltage is demonstrated in single InAs nanowire based field effect transistors. Thanks to a buried heating scheme, we drive both a large thermal bias ΔT > 10 K and a strong field-effect modulation of electric conductance on the nanostructures. This allows the precise mapping of the evolution of the Seebeck coefficient S as a function of the gate-controlled conductivity σ between room temperature and 100 K. Based on these experimental data a novel estimate of the electron mobility is given. This value is compared with the result of standard field-effect based mobility estimates and discussed in relation to the effect of charge traps in the devices.

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We demonstrate a novel nanoheating scheme that yields very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients demonstrated largely exceed those typically obtainable with standard resistive heaters fabricated on top of the oxide layer. The nanoheating platform is demonstrated in the specific case of a short-nanowire device.PACS numbers: 72.20. Pa, 81.07.Gf, 85.30.Tv In the past decade much effort was directed to the investigation of the thermoelectric (TE) properties of innovative materials. Such a revival of TE science was largely driven by the interest in solid-state energy converters 1-4 and by the development of novel advanced materials 5 and, in particular, nanomaterials 6-8 . Indeed, the achievement of an efficient and cost-effective TE technology depends on the optimization of a set of interdependent material parameters of the active element: the Seebeck coefficient S and the heat and charge conductivities κ and σ. Recent developments in nanoscience yielded new strategies for the design of novel and more efficient nanomaterials in which the strong interdependency between S, κ and σ can be made less stringent [9][10][11][12] . Despite the host of available theoretical predictions 12-16 , however, the optimization of the TE behavior of nanostructured materials still remains an open and actively investigated problem 17,18 , in particular for what concerns the influence of electron quantum states engineering on the power factor σS 2 . This led to the development of a number of experimental arrangements designed to impose a controllable thermal bias over micrometric or even submicrometric active elements and to measure how this affects charge transport in the device. Differently from macroscopic active elements, nanoscale TE materials also allow the investigation of thermal effects in devices where fieldeffect can be used to control carrier density 18,19 or even quantum states energetics 20,21 and coupling 22 . While this may not be a directly scalable strategy in view of applications, it is particularly useful for what concerns the fundamental investigation of the impact of dopinga key parameter -on TE performance. Various examples of microheating systems were reported in the literature. These include (i) suspended SiN x microheaters, which enable a precise estimate of the κ of individual nanostructures, but also pose non-trivial technical challenges 23,24 and do not allow the field-effect control of the nanostructure behavior; (ii) resistive heaters fabricated on top of standard Si/SiO 2 substrates, which are instead typically used to estimate S and allow also the field-effect control of carrier density 19,22,[25][26][27][28] .Here we demonstrate an innovative buried-heater (BH) scheme based on current diffusion in the conductive bulk of a SiO 2 /Si substrate. This scheme is different from the more standard one of "top" heaters (THs) relying on resistive element...

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This paper addresses the effect of Mn (2%, fixed) and Co (2, 4, and 6%, varied) substitution on the structural, optical, dielectric and magnetic responses of ZnO nanoparticles synthesized by the co-precipitation chemical route.

(a) dielectric constant, (b) dielectric loss and (c) AC conductivity vs. frequency for un-doped and 5 at% Co-doped TiO2 NPs.

In this work, an attempt has been made to compare the physical properties of conductive films of Nb-doped TiO2 deposited on Kapton polyimide, glass and silicon substrates. Thin films were deposited by radio frequency sputtering at room temperature and subsequently characterized using X-ray diffraction, X-ray photoelectron spectroscopy, UV-VIS-NIR spectroscopy and Hall Effect measurement. Structurally, the films grown on the flexible substrate exhibit more strain and had inferior crystallinity (crystallite size [Formula: see text]13.8 nm) compared to the films deposited on glass and silicon substrates (crystallite size [Formula: see text]27 nm). The film on glass had a resistivity value around [Formula: see text] while the resistivity of the films grown on polyimide was found about five-fold higher. Furthermore, the films deposited on glass substrate showed optical transparency of [Formula: see text]80% in the visible range (400–750 nm). The inferior electrical transport properties of the films grown on polyimide were correlated with the poor crystallinity and cracks induced during the annealing process. Furthermore, various possible routes have been discussed to improve crystallinity and control cracks in the films.