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Experimental and theoretical characterization of an inductively coupled plasma source J. Appl. Phys. 90, 587 (2001); 10.1063/1.1375009Stabilizing inductively coupled plasma source impedance and plasma uniformity using a Faraday shieldThe electron temperature and ion density produced by a microfabricated plasma generator are characterized in both argon gas and air. The plasma generator sustains a discharge by inductively coupling 450 MHz rf power into a small ͑10 mm diameter͒ vacuum chamber. The inductively coupled plasma source is surface micromachined on a glass wafer by electroplating a planar spiral inductor and two interdigitated capacitors. A plasma can be sustained using gas pressures between 0.1 and 10 Torr and rf powers between 0.3 and 3 W. The ion density increases from 10 10 to 10 11 cm Ϫ3 over this range of power. The electron temperature decreases from 4 to 2 eV as the pressure increases from 0.1 to 1 Torr.

We successfully synthesized well aligned ZnO nanowire (ZnO NW) arrays on Si (100) and indium tin oxide (ITO) glass substrates at the low temperature of 500 °C by a two-stage growth process without metal catalyst. The synthesized ZnO NWs had diameters in the range of 50−100 nm and lengths in the range of 5−8 μm. X-ray diffraction showed that ZnO NW arrays had single-crystal wurtzite structures and grew along the c-axis. Photoluminescence spectra revealed that the ZnO NWs showed a strong UV band at 3.2 eV and a broad green band at 2.3 eV at room temperature. We also observed that the alignment situation and UV band emission of the ZnO NW arrays was enhanced with an increased O2 flow rate in the first stage. In addition, various O2 gas flow rates affected the morphologies of the ZnO nanomaterials. We present a detailed discussion regarding the growth behavior and mechanism of the ZnO NW arrays in this study.

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This paper reports a facile continuous flow injection (CFI) process to synthesize high-quality long zinc oxide nanowire arrays (ZnO-NAs) using a hydrothermal method. In previous related studies, the photoluminescence (PL) spectra of ZnO-NAs synthesized using a batch process exhibit highly visible emission caused by defect structures. In contrast to the batch process, zinc oxide nanowire arrays grown using the CFI process can reduce the visible emission in PL spectra effectively, demonstrating the qualities of zinc oxide nanowire arrays as superior to those grown using a batch process. To understand the difference between batch processes and the CFI process, inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to analyze the zinc precursor concentration regarding growth duration. According to the concentration variation of both processes, we could determine that zinc precursor concentration is maintained at a constant level to promote ZnO-NAs growth continuously in the CFI process. Long ZnO nanowire arrays can be obtained easily using the CFI process. The results demonstrate that the CFI process is a facile process for growing high-quality long ZnO nanowire arrays.

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Heteroepitaxy with large thermal and lattice mismatch between the semiconductor and substrate is a critical issue for high-quality epitaxial growth. Typically, high growth temperatures (>1000 °C) are required to achieve high-quality GaN epilayers by conventional metal−organic chemical vapor deposition. In this study, the high-quality GaN heteroepitaxy is realized by atomic layer annealing and epitaxy (ALAE) at a low growth temperature of 300 °C. The layer-by-layer, in situ He/Ar plasma treatment at a low plasma power was introduced in each cycle of atomic layer deposition to contribute the effective annealing effect for significant enhancement of the GaN crystal quality. The Penning effect is responsible for significant improvement of the GaN crystal quality due to the incorporation of He into the Ar plasma. The high-resolution transmission electron microscopy, nano-beam electron diffraction, and atomic force microscopy reveal a high-quality nanoscale single-crystal GaN heteroepitaxy and a very smooth surface. The full width at half-maximum of the X-ray rocking curve of the GaN epilayer is as low as 168 arcsec. The low-temperature ALAE technique is highly beneficial to grow high-quality nanoscale GaN epilayers for sustainable, energy-saving, and energy-efficient devices including high-performance solid-state lighting, solar cells, and highpower electronics.