ZnO is a very promising material for spintronics applications, with many groups reporting room temperature ferromagnetism in films doped with transition metals during growth or by ion implantation. In films doped with Mn during PLD, we find an inverse correlation between magnetization and electron density as controlled by Sn doping. The saturation magnetization and coercivity of the implanted single-phase films were both strong functions of the initial anneal temperature, suggesting that carrier concentration alone cannot account for the magnetic properties of ZnO:Mn and factors such as crystalline quality and residual defects play a role. Plausible mechanisms for the ferromagnetism include the bound magnetic polaron model or exchange is mediated by carriers in a spin-spilt impurity band derived from extended donor orbitals. We will also review progress in ZnO nanowires. The large surface area of nanorods makes them attractive for gas and chemical sensing, and the ability to control their nucleation sites makes them candidates for micro-lasers or memory arrays. Single ZnO nanowire depletion-mode metal-oxide semiconductor field effect transistors exhibit good saturation behavior, threshold voltage of∼-3V and a maximum transconductance of 0.3 mS/mm.Under UV illumination, the drain-source current increased by approximately a factor of 5 and the maximum transconductance was ∼ 5 mS/mm. The channel mobility is estimated to be ∼3 cm 2 /V.s, comparable to that for thin film ZnO enhancement mode MOSFETs and the on/off ratio was ∼25 in the dark and -125 under UV illumination. Pt Schottky diodes exhibit excellent ideality factors of 1.1 at 25 °C, very low reverse currents and a strong photoresponse, with only a minor component with long decay times thought to originate from surface states. In the temperature range from 25-150 C, the resistivity of nanorods treated in H 2 at 400 C prior to measurement showed an activation energy of 0.089 eV and was insensitive to the ambient used. By contrast, the conductivity of nanorods not treated in H 2 was sensitive to trace concentrations of gases in the measurement ambient even at room temperature, demonstrating their potential as gas sensors.

ZnO spintronics and nanowire devices

Glass micromachining is currently becoming essential for the fabrication of micro-devices, including micro- optical-electro-mechanical-systems (MOEMS), miniaturized total analysis systems (μTAS) and microfluidic devices for biosensing. Moreover, glass is radio frequency (RF) transparent, making it an excellent material for sensor and energy transmission devices. Advancements are constantly being made in this field, yet machining smooth through-glass vias (TGVs) with high aspect ratio remains challenging due to poor glass machinability. As TGVs are required for several micro-devices, intensive research is being carried out on numerous glass micromachining technologies. This paper reviews established and emerging technologies for glass micro-hole drilling, describing their principles of operation and characteristics, and their advantages and disadvantages. These technologies are sorted into four machining categories: mechanical, thermal, chemical, and hybrid machining (which combines several machining methods). Achieved features by these methods are summarized in a table and presented in two graphs. We believe that this paper will be a valuable resource for researchers working in the field of glass micromachining as it provides a comprehensive review of the different glass micromachining technologies. It will be a useful guide for advancing these techniques and establishing new hybrid ones, especially since this is the first broad review in this field.

Micro-Hole Drilling on Glass Substrates—A Review.

Synthesis and characterization of Sb doped ZnO thin films for photodetector application

A highly efficient ultraviolet photodetector was successfully obtained based on a Sb-doped p-type ZnO microwire p–n homojunction which consisted of a single Sb-doped p-type ZnO microwire and a single undoped ZnO microwire. The ultralong Sb-doped ZnO single crystalline microwires were synthesized via a chemical vapor deposition method. The ZnO microwire homojunction showed well-defined rectification characteristics, which indicated the p-type conductivity of the Sb-doped ZnO microwire. An ultraviolet photodetector with an external quantum efficiency of 64.5% was obtained based on the ZnO microwire p–n homojunction. The photodetector showed high wavelength selectivity with a full width at half maximum of 6 nm for the photoresponse peak located at 386 nm.

A highly efficient UV photodetector based on a ZnO microwire p–n homojunction

Periodic structures with dimensions on the order of the wavelength of light can tailor and improve the performance of optical components, and they can enable the creation of devices with new functionalities. For example, distributed Bragg reflectors (DBRs), which are created by periodic modulations in a structure’s dielectric medium, are essential in dielectric mirrors, vertical cavity surface emitting lasers, fiber Bragg gratings, and single-frequency laser diodes. This work introduces nanoscale DBRs integrated directly into gallium nitride (GaN) nanowire waveguides. Photonic band gaps that are tunable across the visible spectrum are demonstrated by precisely controlling the grating’s parameters. Numerical simulations indicate that in-wire DBRs have significantly larger reflection coefficients in comparison with the nanowire’s end facet. By comparing the measured spectra with the simulated spectra, the index of refraction of the GaN nanowire waveguides was extracted to facilitate the design of photonic c...

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Widely Tunable Distributed Bragg Reflectors Integrated into Nanowire Waveguides.

The methodology on the synthesis of Sb-doped ZnO nanostructures by considering dopant as a catalyst is proposed and demonstrated. The nanostructures were synthesized using intrinsic ZnO as target and Sb-coated Si as substrate, where Sb simultaneously acts as dopant and the catalyst. The catalyst Sb is highly sensitive to temperature conditions resulted in two different nanostructures, the nanowires and the nanosheets. The surface, structural and optical characteristics of the nanowires and the nanosheets are comparatively investigated through SEM, EDX, XRD, Raman spectroscopy and photo luminescence (PL) spectroscopy. The nanowires showed a strong green emission in the PL spectrum and the presence of oxygen vacancies is confirmed thorough Raman peak shift at 556 cm−1. In the case of nanosheets, the defect in oxygen vacancies is completely reduced, and improved UV emission is observed, which confirms the diffusion of Sb in the ZnO lattice.

Influence of Sb as a catalyst in the growth of ZnO nano wires and nano sheets using Nanoparticle Assisted Pulsed Laser Deposition (NAPLD)

The ablation dynamics of a tin (Sn) micro-droplet by double pulse laser irradiation for the development of an extreme ultraviolet lithography source was investigated. The solid state Sn droplet target with a diameter of 30 µm was irradiated by double laser pulses from a Q-switched Nd : YAG laser and a CO2 laser, and the kinetic behaviour of debris such as Sn atoms, ions and of the dense particles from the droplet was investigated by the laser-induced fluorescence imaging method, Faraday cups and high-speed imaging, respectively. After the pre-pulse irradiation of the Nd : YAG laser, the ions were emitted towards the laser incident direction with an average kinetic energy of 3–6 keV and the dense particle cloud moved in the direction opposite to the laser incident direction with expansion by a reaction force due to the plasma expansion at a speed of approximately 500 m s−1. On the other hand, the Sn atoms were ejected in all directions from the target with a speed as fast as 20 km s−1. The expanding target was subsequently irradiated by the main pulse of the CO2 laser with a delay of 800 ns and the dense cloud almost disappeared due to main-pulse irradiation.

Ablation dynamics of tin micro-droplet irradiated by double pulse laser used for extreme ultraviolet lithography source

Influence of Sb in synthesize of ZnO nanowire using sandwich type substrate in carbothermal evaporation method

We have investigated direct etching of poly(methyl methacrylate) (PMMA) using laser plasma soft X-rays. We focused soft X-rays of 6–25 nm on PMMA sheets efficiently using an Au coated ellipsoidal mirror. 7×10-2% of laser energy is estimated to be converted to soft X-rays that was incident to the PMMA sheets. We found that PMMA surfaces are etched beyond a threshold power density. The energy density of absorbed soft X-rays at the threshold is 7 kJ/cm3. The results suggest that etching is governed by decomposition into fragments.

Direct Etching of Poly(methyl methacrylate) Using Laser Plasma Soft X-rays

Single-crystalline ZnO nanowires on a sapphire substrate have been synthesized by a nanoparticle-assisted pulsed-laser deposition (NAPLD) using a pure and Sb2O3 doped ZnO target. Low density and vertically well-aligned ZnO nanowires were grown on hexagonal cone-shape ZnO cores by introduction of a ZnO buffer layer. More than 90% of the ZnO cores of the Sb-induced ZnO nanowires are formed in the same size of 400 nm. The ZnO nanowires consist of single-crystalline wurtzite ZnO crystal and grow along [0001] direction. The room-temperature photoluminescence spectrum exhibited a strong ultraviolet emission at around 380 nm and a relatively low broad band emission in the visible region, indicating a low concentration of structural defect in the nanowires. Sb can be used as one of the effective additives to control the morphology and alignment of ZnO nanowires synthesized by NAPLD.

K. Okazaki

Papers

Influence of Sb as a catalyst in the growth of ZnO nano wires and nano sheets using Nanoparticle Assisted Pulsed Laser Deposition (NAPLD)

Ablation dynamics of tin micro-droplet irradiated by double pulse laser used for extreme ultraviolet lithography source

Influence of Sb in synthesize of ZnO nanowire using sandwich type substrate in carbothermal evaporation method

Direct Etching of Poly(methyl methacrylate) Using Laser Plasma Soft X-rays

Influence of Sb on a controlled-growth of aligned ZnO nanowires in nanoparticle-assisted pulsed-laser deposition