Metal–insulator transition in single crystalline ZnO nanowires

Abstract

In this work, we report on the metal–insulator transition and electronic transport properties of single crystalline ZnO nanowires synthetized by means of Chemical Vapor Deposition. After evaluating the effect of adsorbed species on transport properties, the thermally activated conduction mechanism was investigated by temperature-dependent measurements in the range 81.7–250 K revealing that the electronic transport mechanism in these nanostructures is in good agreement with the presence of two thermally activated conduction channels. More importantly, it was observed that the electrical properties of ZnO NWs can be tuned from semiconducting to metallic-like as a function of temperature with a metal-to-insulator transition (MIT) observed at a critical temperature above room temperature (T c ∼ 365 K). Charge density and mobility were investigated by means of field effect measurements in NW field-effect transistor configuration. Results evidenced that the peculiar electronic transport properties of ZnO NWs are related to the high intrinsic n-type doping of these nanostructures that is responsible, at room temperature, of a charge carrier density that lays just below the critical concentration for the MIT. This work shows that native defects, Coulomb interactions and surface states influenced by adsorbed species can significantly influence charge transport in NWs.

Nanoscale Self-Assembly: Nanopatterning and Metrology

“…Assuming the cylinder-on-plate model and by considering the transfer characteristics reported in Figure 15d, the carrier concentration was estimated to be at least 2.5 × 10 19 cm −3 while the electron mobility was estimated to be about 0.07 cm −3 . It should be noticed that the here reported charge density results to be much larger than the charge density observed in the case of single-crystalline ZnO NWs grown with a bottom-up approach that was reported to be in the order of 10 17 − 10 18 cm −3 [104,105]. In order to achieve new insights into the electronic transport mechanism of ZnO NWs realized by means of SIS with a top-down approach and to compare results with single crystalline ZnO NWs realized with a bottom-up approach, temperature-dependent electrical characterizations are required.…”

Experimental and Modeling Study of Metal–Insulator Interfaces to Control the Electronic Transport in Single Nanowire Memristive Devices

“…A combined experimental and modeling approach was exploited for a more detailed investigation of the role of metal–insulator interfaces on the electronic transport properties. In purely electronic transfer (i.e., without electrochemical reactions and ionic transport), the metal-insulating interface at the nanocontact can be modeled as a Schottky barrier, as a consequence of the semiconducting nature of the intrinsically n-type doped ZnO NWs. − In this case, electronic transport at the metal–ZnO interface of the nanocontact occurs through thermionic emission, where current can be phenomenologically expressed according to the relationship I = I 0 [ exp true( V η V normalT true) − 1 ] where V is the applied voltage, I 0 is the inverse saturation current, η is the ideality factor, V T = kT / e is the thermal voltage at temperature T , k is the Boltzmann constant, and e is the electron charge. Note that the saturation current I 0 implicitly depends on the contact area, as well as on the Schottky barrier height, thus relying on the specific choice of the metal contact.…”

Application of Nanoparticles in the Diagnosis of Gastrointestinal Diseases: A Complete Future Perspective

“… 35 They can be categorized into various types based on their composition materials, including metal NWs (such as Ni, Ag, and Au), 36 , 37 semiconductor NWs (such as InP, Si, and GaN), 38 , 39 and insulator NWs (such as SiO2 and ZnO). 40 Metal NWs, with their exceptional electrical, 41 optical, 42 thermal, 43 , 44 and mechanical properties, 45 , 46 have significantly impacted the field of bioimaging. For instance, copper NWs have been utilized in surface-enhanced Raman scattering (SERS) imaging, enabling signal amplification with remarkably high signal-to-noise ratio (SNR).…”