A low temperature process for phosphorous doped ZnO nanorods via a combination of hydrothermal and spin-on dopant methods

P-Type ZnO Films Made by Atomic Layer Deposition and Ion Implantation

Zinc oxide (ZnO) is a wide bandgap semiconductor that holds significant potential for various applications. However, most of the native point defects in ZnO like Zn interstitials typically cause an n-type conductivity. Consequently, achieving p-type doping in ZnO is challenging but crucial for comprehensive applications in the field of optoelectronics. In this work, we investigated the electrical and optical properties of ex situ doped p-type ZnO films. The p-type conductivity has been realized by ion implantation of group V elements followed by rapid thermal annealing (RTA) for 60 s or flash lamp annealing (FLA) on the millisecond time scale in nitrogen or oxygen ambience. The phosphorus (P)-doped ZnO films exhibit stable p-type doping with a hole concentration in the range of 1014 to 1018 cm-3, while antimony (Sb) implantation produces only n-type layers independently of the annealing procedure. Microstructural studies of Sb-doped ZnO show the formation of metallic clusters after ms range annealing and SbZn-oxides after RTA.

Electrostatic Induction Nanogenerator Boosted by One-Dimensional Metastructure: Application to Energy and Information Transmitting Smart Tag System

The recent application of the internet of things demands the ubiquitous utilization of data and electrical power. Even with the development of a wide variety of energy-harvesting technologies, few studies have reported a device transporting electrical energy and data simultaneously. This paper reports an electrostatic induction nanogenerator (ESING) consisting of a one-dimensional metastructure that can modulate the output voltage based on the resonance of ultrasound waves to transmit energy and data simultaneously. The ESING device is fabricated using electronegative poly(vinylidene fluoride) (PVDF) membrane using a phase inversion process. The output voltage from the ESING device exhibits periodic resonant peaks as the gap between the PVDF membrane and the Al electrode changes, showing an up to 35-fold difference between the maximum and minimum output voltages depending on the resonance state. The energy and electrical signal can be transmitted simultaneously in free space because the ESING converts energy from high-frequency ultrasound waves. This paper provides proof of concept for a data and energy-transferable smart tag device based on ESING devices exhibiting resonant and non-resonant states. A device consisting of four ESINGs for a 4-bit signal is implemented to demonstrate 16 signals.

Oxygen plasma assisted enhanced photoresponse of ZnO nanowires fabricated by catalyst-free chemical vapor deposition

Photocurrent of the ZnO nanowire-based photodetectors was enhanced 8 times by modifying the surface of nanowires with oxygen plasma.

Hydrothermal Synthesis of ZnO Structures Formed by High-Aspect-Ratio Nanowires for Acetone Detection

Snowflake-like ZnO structures originating from self-assembled nanowires were prepared by a low-temperature aqueous solution method. The as-grown hierarchical ZnO structures were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results showed that the snowflake-like ZnO structures were composed of high-aspect-ratio nanowires. Furthermore, gas-sensing properties to various testing gases of 10 and 50 ppm were measured, which confirms that the ZnO structures were of good selectivity and response to acetone and could serve for acetone sensor to detect low-concentration acetone.

ZnO-Based Microcavities Sculpted by Focus Ion Beam Milling

We reported an easy fabrication method to realize ZnO-based microcavities with various cavity shapes by focused ion beam (FIB) milling. The optical characteristics of different shaped microcavities have been systematically carried out and analyzed. Through comprehensive studies of cathodoluminescence and photoluminescence spectra, the whispering gallery mode (WGM) was observed in different shaped microcavities. Up further increasing excitation, the lasing action was dominated by these WGMs and matched very well to the simulated results. Our experiment shows that ZnO microcavities with different shapes can be made with high quality by FIB milling for specific applications of microlight sources and optical devices.

Enhanced electrochemical performance of phosphorus incorporated carbon nanofibers by the spin-on dopant method

Phosphorus-incorporated carbon nanofibers (CNFs) were successfully fabricated by using electrospinning and spin-on dopant (SOD) procedures together for electrochemical capacitors (ECs).

Hydrogen plasma-mediated modification of the electrical transport properties of ZnO nanowire field effect transistors

We investigated the effects of hydrogen plasma treatment on the electrical transport properties of ZnO nanowire field effect transistors (FETs) with a back gate configuration. After hydrogen plasma treatment of the FET devices, the effective carrier density and mobility of the nanowire FETs increased with a threshold voltage shift toward a negative gate bias direction. This can be attributed to the desorption of oxygen molecules adsorbed on the surface of the nanowire channel, to passivation and to doping effects due to the incorporation of energetic hydrogen ions generated in plasma.

Hierarchical ZnO nanorods on Si micropillar arrays for performance enhancement of piezoelectric nanogenerators

Enhanced output power from a ZnO nanorod (NR)-based piezoelectric nanogenerator (PNG) is demonstrated by forming a heterojunction with Si micropillar (MP) array. The length of the SiMP array, which was fabricated by electrochemical etching, was increased systematically from 5 to 20 μm by controlling the etching time. Our structural and optical investigations showed that the ZnO NRs were grown hierarchically on the SiMPs, and their crystalline quality was similar regardless of the length of the underlying SiMPs. The peak output voltage from the ZnO NR-based PNG was greatly increased by ∼5.7 times, from 0.7 to 4.0 V, as the length of the SiMP arrays increased from 0 (flat substrate) to 20 μm. The enhancement mechanism was explained based on the series connection of the ZnO NRs regarded as a single source of piezoelectric potential by creating a heterojunction onto the SiMP arrays.

Psychological tactile sensor structure based on piezoelectric nanowire cell arrays

To produce artificial psychological feeling, especially ‘pain’, an electrical structure that mimics human skin has been studied.

Morphology controlled growth of ZnAl-layered double hydroxide and ZnO nanorod hybrid nanostructures by solution method

Morphological evolution of ZnAl-based hybrid nanostructures from ZnAl layered double hydroxide to ZnO nanorods grown by a hydrothermal method depending on the thickness of the Al₂O₃/ZnO double seed layer.

Emerging Applications of Liquid Crystals Based on Nanotechnology

Diverse functionalities of liquid crystals (LCs) offer enormous opportunities for their potential use in advanced mobile and smart displays, as well as novel non-display applications. Here, we present snapshots of the research carried out on emerging applications of LCs ranging from electronics to holography and self-powered systems. In addition, we will show our recent results focused on the development of new LC applications, such as programmable transistors, a transparent and active-type two-dimensional optical array and self-powered display systems based on LCs, and will briefly discuss their novel concepts and basic operating principles. Our research will give insights not only into comprehensively understanding technical and scientific applications of LCs, but also developing new discoveries of other LC-based devices.