Nanowire-based Electronic Devices Research Articles

Low frequency noise in β -Ga2O3 based nanoelectronic devices

In this work, low frequency noise in β-Ga2O3 nanowire-based (NW) electronic devices is analyzed, which exhibits different behaviors as the device size scales down. The noise spectrum for the narrower NW (∼80 nm) is closer to 1/f characteristics, whereas it starts to show evident 1/f2 components as the NW size gets thicker (∼200 nm), giving clear signs of distinctive features for the bunch of traps at the NW interface or in the bulk. Our results show that 1/f noise in these NW electronic devices seems predominantly originated from an aggregated effect of the intricate trap states close to the β-Ga2O3 NW surface or interface with a wide range distribution, while finite groups of active deep traps play a critical role in contributing 1/f2components via generation-recombination or random telegraph signal processes. Notably, as the bias voltage increases, the 1/f2 components in the noise spectra get more overwhelming and would shift toward lower frequencies, suggesting that electric ionization effects would screen the shallow traps close to the surface or interface based on the Poole–Frenkel model. The Hooge's constants extracted from the 1/f noise component for these β-Ga2O3 NW-based devices fall in the range of 0.008–0.019, which are comparable to those of the best reported devices based on other wide bandgap semiconductor with nanoscale structures, including GaN, ZnO, and SnO2. This work may give hints of revealing the sophisticated dynamic behaviors of traps in the surface/volume β-Ga2O3 materials and electronic devices in the nanoscale by low frequency noises.

Nano-scale strain mapping in complete nanowire-based electronic devices by Bragg coherent X-ray diffraction

Nano-scale strain mapping in complete nanowire-based electronic devices by Bragg coherent X-ray diffraction

Simulation study of dielectrophoretic assembly of nanowire between electrode pairs

Dielectrophoresis (DEP) of rod-shaped nanostructures is attractive because of its exceptional capability to fabricate nanowire-based electronic devices. This efficient manipulation method, however, has a common side effect of assembling a certain number of nanowires at undesired positions. It is therefore essential to understand the underlying physics of DEP of nanowires in order to better guide the assembly. In this work, we propose theoretical methods to characterize the dielectrophoretic force and torque as well as the hydrodynamic drag force and torque on the nanowire (typical length: 10 μm). The trajectory of the nanowire is then simulated based on rigid body dynamics. The nanowire is predicted to either bridge the electrodes or attach on the surface of one electrode. A neighborhood in which the nanowire is more likely to bridge electrodes is found, which is conducive to successful assembly. The simulation study in this work provides us not only a better understanding of the underlying physics but also practical guidance on nanowire assembly by DEP.

Direct realizing the growth direction of epitaxial nanowires by electron microscopy

The growth direction of nanowires is critically important for precisely controlling their physical and chemical properties and the performance of related nanowire-based electronic devices. Realizing the true orientations of nanowires is an important issue regarding designing and growth of nanowires with desired orientations and the subsequent applications. In this study, we demonstrated three electron microscopic techniques to determine the growth directions of epitaxial nanowires: mainly, correlating selected area electron diffraction pattern and bright-field imaging in transmission electron microscopes, tilting the nanowires until their growth directions parallel to the incident electron beams in scanning electron microscopes, and correlating the nature of cleavage planes of the nanowire substrates and nanowire projections in the side-view scanning electron microscopic investigations.

Nanoscience and the nano-bioelectronics frontier

This review describes work presented in the 2014 inaugural Tsinghua University Press-Springer Nano Research Award lecture, as well as current and future opportunities for nanoscience research at the interface with brain science. First, we briefly summarize some of the considerations and the research journey that has led to our focus on bottom-up nanoscale science and technology. Second, we recapitulate the motivation for and our seminal contributions to nanowire-based nanoscience and technology, including the rational design and synthesis of increasingly complex nanowire structures, and the corresponding broad range of “applications” enabled by the capability to control structure, composition and size from the atomic level upwards. Third, we describe in more detail nanowire-based electronic devices as revolutionary tools for brain science, including (i) motivation for nanoelectronics in brain science, (ii) demonstration of nanowire nanoelectronic arrays for high-spatial/high-temporal resolution extracellular recording, (iii) the development of fundamentally-new intracellular nanoelectronic devices that approach the sizes of single ion channels, (iv) the introduction and demonstration of a new paradigm for innervating cell networks with addressable nanoelectronic arrays in three-dimensions. Last, we conclude with a brief discussion of the exciting and potentially transformative advances expected to come from work at the nanoelectronics-brain interface.

Electron mobilities approaching bulk limits in "surface-free" GaAs nanowires.

Achieving bulk-like charge carrier mobilities in semiconductor nanowires is a major challenge facing the development of nanowire-based electronic devices. Here we demonstrate that engineering the GaAs nanowire surface by overcoating with optimized AlGaAs shells is an effective means of obtaining exceptionally high carrier mobilities and lifetimes. We performed measurements of GaAs/AlGaAs core-shell nanowires using optical pump-terahertz probe spectroscopy: a noncontact and accurate probe of carrier transport on ultrafast time scales. The carrier lifetimes and mobilities both improved significantly with increasing AlGaAs shell thickness. Remarkably, optimized GaAs/AlGaAs core-shell nanowires exhibited electron mobilities up to 3000 cm(2) V(-1) s(-1), reaching over 65% of the electron mobility typical of high quality undoped bulk GaAs at equivalent photoexcited carrier densities. This points to the high interface quality and the very low levels of ionized impurities and lattice defects in these nanowires. The improvements in mobility were concomitant with drastic improvements in photoconductivity lifetime, reaching 1.6 ns. Comparison of photoconductivity and photoluminescence dynamics indicates that midgap GaAs surface states, and consequently surface band-bending and depletion, are effectively eliminated in these high quality heterostructures.

Scanning capacitance characterization of potential screening in InAs nanowire devices

We have used scanning capacitance microscopy and spectroscopy to examine the effects of micron-scale metal contacts, typically present in nanowire-based electronic devices, on carrier modulation and electrostatic behavior in InAs semiconductor nanowires. We observe a pronounced dependence of scanning capacitance images and spectra on distance between the scanning capacitance probe tip and nanowire contact up to distances of 3–4 μm. Based on the comparison of these data with results of finite-element electromagnetic simulations, we interpret these results as a consequence of electrostatic screening of the tip-nanowire potential difference by the large metal contact. These results provide direct experimental verification of contact screening effects on the electronic behavior of nanowire devices and are indicative of the importance of assessing and accounting for the effect of large-scale contact and circuit elements on the characteristics of nanoscale electronic devices generally.

Mechanism and control of sidewall growth and catalyst diffusion on oxide nanowire vapor-liquid-solid growth

Oxide nanowires formed via the vapor-liquid-solid (VLS) mechanism are attractive building blocks toward nanowire-based electronic devices due to their fascinating physical properties. Although well-defined oxide nanowires are strongly required for the applications, tapering during oxide nanowire VLS growth has been detrimental and uncontrollable. Here we demonstrate the mechanism to control the tapering during oxide VLS growth. Suppressing simultaneously both the oxidization of adatoms at the sidewall and the catalyst diffusion from the tip was found to be essential to avoid the tapering. This mechanism would be universal in various oxide nanowire VLS growths.

From the adhesion of atomic clusters to the fabrication of nanodevices

An experimental study of Bi, Sb, and Cu clusters incident at velocities ≳50m∕s on SiO2, Si3N4, polymethylmethacrylate, and photoresist surfaces shows that the clusters adhere much more strongly to SiO2 and Si3N4 than to the polymer materials. The differences in adhesion properties allow assembly of a range of nanowire-based electronic devices from cluster building blocks using lithographically patterned polymer layers. Clusters adhere to the substrate but not to the surface of the polymer template, eliminating parasitic conduction. Molecular dynamics simulations show that differing cluster-surface interactions affect adhesion most strongly when high incident velocities cause significant plastic deformation of the clusters.