Stability of Schottky and Ohmic Au Nanocatalysts to ZnO Nanowires

Abstract

Manufacturable nanodevices must now be the predominant goal of nanotechnological research to ensure the enhanced properties of nanomaterials can be fully exploited and fulfill the promise that fundamental science has exposed. Here, we test the electrical stability of Au nanocatalyst-ZnO nanowire contacts to determine the limits of the electrical transport properties and the metal-semiconductor interfaces. While the transport properties of as-grown Au nanocatalyst contacts to ZnO nanowires have been well-defined, the stability of the interfaces over lengthy time periods and the electrical limits of the ohmic or Schottky function have not been studied. In this work, we use a recently developed iterative analytical process that directly correlates multiprobe transport measurements with subsequent aberration-corrected scanning transmission electron microscopy to study the electrical, structural, and chemical properties when the nanowires are pushed to their electrical limits and show structural changes occur at the metal-nanowire interface or at the nanowire midshaft. The ohmic contacts exhibit enhanced quantum-mechanical edge-tunneling transport behavior because of additional native semiconductor material at the contact edge due to a strong metal-support interaction. The low-resistance nature of the ohmic contacts leads to catastrophic breakdown at the middle of the nanowire span where the maximum heating effect occurs. Schottky-type Au-nanowire contacts are observed when the nanowires are in the as-grown pristine state and display entirely different breakdown characteristics. The higher-resistance rectifying I-V behavior degrades as the current is increased which leads to a permanent weakening of the rectifying effect and atomic-scale structural changes at the edge of the Au interface where the tunneling current is concentrated. Furthermore, to study modified nanowires such as might be used in devices the nanoscale tunneling path at the interface edge of the ohmic nanowire contacts is removed with a simple etch treatment and the nanowires show similar I-V characteristics during breakdown as the Schottky pristine contacts. Breakdown is shown to occur either at the nanowire midshaft or at the Au contact depending on the initial conductivity of the Au contact interface. These results demonstrate the Au-nanowire structures are capable of withstanding long periods of electrical stress and are stable at high current densities ensuring they are ideal components for nanowire-device designs while providing the flexibility of choosing the electrical transport properties which other Au-nanowire systems cannot presently deliver.

Electrical Activity and Extremes of Individual Suspended ZnO Nanowires for 3D Nanoelectronic Applications

“…A clear observation reveals that J BD (represented by the black curve) exhibits a decrease with the increase of L i , whereas P BD (indicated by the blue curve) demonstrates an increase as L i diminishes. The maximum J BD of 0.14 MA/cm 2 and maximum P BD of 6.93 mW/μm 3 (power: 0.306 mW, NW diameter: 110 nm, L i : 4.64 μm) were achieved, which are consistent with the highest results measured on ZnO NWs vertically grown on the substrate . It is important to emphasize that the electrical analysis was conducted on distinct suspended ZnO NWs ( n = 2), and their resulting characteristics are presented in Table S2.…”

“…The maximum J BD of 0.14 MA/cm 2 and maximum P BD of 6.93 mW/μm 3 (power: 0.306 mW, NW diameter: 110 nm, L i : 4.64 μm) were achieved, which are consistent with the highest results measured on ZnO NWs vertically grown on the substrate. 44 It is important to emphasize that the electrical analysis was conducted on distinct suspended ZnO NWs (n = 2), and their resulting characteristics are presented in Table S2.…”

Atomic scale mechanics explored by in situ transmission electron microscopy with a quartz length-extension resonator as a force sensor

“…As an example, Tavazza et al pointed out that the electrical and mechanical properties of Au nanocontacts (NCs) are significantly affected by their atomic configurations [5]. Such structure-sensitive physical properties are potentially useful in applications such as future nanodevices [6,7], atomic catalysts [8] and nanoscale manipulations [9][10][11]. In addition, the conductivity of metal nanowires (NWs) has received much attention, since this property has been shown to be quantized even at room temperature, and this effect could be exploited to design various electronic devices [12].…”

Non-linear nanoscale piezoresponse of single ZnO nanowires affected by piezotronic effect

“…while Ohmic contacts lead to linear characteristics, the inclusion of a Schottky contact will lead to a rectifying I-V curve (Panda;et al, 2013;Lee et al, 2016;Lord et al, 2017). In this case, as shown in Fig.…”