Different coloration of the nanostructured silicon surface upon plasma-assisted etching

The effects of changes in the color of silicon plates with nanostructured surfaces versus the features of nanostructures are investigated. Vertical nanostructures with high aspect ratios are constructed via anisotropic two-stage plasma-assisted etching (Bosch process). The surface coloration is explained by the fact that incident radiation is partly trapped by waveguide edge modes and its remaining part is scattered at the surface. The surface-film color is related to the positive and negative curvature of the nanostructures formed as a result of the plasma-assisted process.     

分子束外延GaN薄膜的X射线光电子能谱和俄歇电子能谱研究

用XPS和AES电子能谱的方法对等离子体辅助分子束外延(MBE)生长的GaN薄膜进行了表面分析和深度剖析.发现红外分子束外延(RFMBE)生长的富镓GaN薄膜实际表面存在O和C吸附层,C主要为物理吸附,而O在GaN表面形成局域化学键产生氧络合物覆盖层,并形成一定的深度分布.杂质O在GaN带隙中导带底形成杂质带同时引入深受主能级,使得带隙变窄室温光吸收谱向低能方向移动,光致发光谱出现宽带发光峰.从而影响GaN薄膜的电学和光学性质 关键词： GaN薄膜 X射线光电子能谱 俄歇电子能谱 表面分析     

Synthesis of p-type zinc oxide films by plasma-assisted pulsed laser deposition

Heavily acceptor doped zinc oxide (ZnO) films were deposited on quartz substrates by plasma-assisted pulsed laser deposition (PA-PLD) using a non-sintered target heavily doped with phosphorus or copper and radio frequency induction-coupled nitrogen or oxygen plasma (RF-ICP). The p-type ZnO layer was achieved by a nitrogen acceptor dopant using the technique of plasma-assisted nitrogen (PA-N) pulsed laser deposition. Photoluminescence spectra showed a peak from phosphorus- or copper-bound excitons at about 380 nm and a broad, green defect-related band occurring at about 550 nm. Transmission spectra showed a blue shift of the near-band-edge wavelength and a worsening of transmission by heavily copper-doped zinc oxide.     

A review of microelectronic film deposition using direct and remoteelectron-beam-generated plasmas

Soft-vacuum-generated electron beams employed to create a large-area plasma for assisting chemical vapor deposition (CVD) of thin films are reviewed. The electron-beam plasma is used directly, where electron-impact dissociation of feedstock gases plays a dominant role, and indirectly in a downstream afterglow, where electron-impact dissociation of feedstock reactants plays no role. Photodissociation and metastable atom-molecule reactions dominate in the downstream afterglow. The transmitted beam spatial-intensity profiles are quantified from initial generation at a slotted line-shaped cold cathode through acceleration in the cathode sheath and propagation in the ambient gas. The vacuum ultraviolet (VUV) output spectrum and VUV generation efficiency from electron-beam-excited plasmas are measured. The properties of films deposited by direct electron-beam-generated plasma-assisted CVD and downstream afterglow CVD are reviewed and compared to conventional plasma-assisted CVD films     

Experimental investigation of effects of airflows on plasma-assisted combustion actuator characteristics

The effects of the airflow on plasma-assisted combustion actuator(PACA) characteristics are studied in detail. The plasma is characterized electrically, as well as optically with a spectrometer. Our results show that the airflow has an obvious influence on the PACA characteristics. The breakdown voltage and vibrational temperature decrease, while the discharge power increases compared with the stationary airflow. The memory effect of metastable state species and the transportation characteristics of charged particles in microdischarge channel are the dominant causes for the variations of the breakdown voltage and discharge power, respectively, and the vibrational temperature calculated in this work can describe the electron energy of the dielectric barrier discharge plasma in PACA. These results offer new perspectives for the use of PACA in plasma-assisted combustion.     

Dependence of Mechanical and Tribological Properties of a-C:H:SiOx Films on the Bias Voltage Amplitude of the Substrate

Technical Physics - The surface of AISI 316L stainless steel has been modified by depositing an a-C:H:SiOx film using plasma-assisted chemical vapor-phase deposition with the application of a...     

Synthesis of Single-Layer ZrN-Coatings Using Vacuum-Arc Plasma-Assisted Deposition with Plasma Flow Filtering

Russian Physics Journal - The coatings based on ZrN are formed by the vacuum-arc plasma-assisted process under the conditions of plasma filtering from the droplet phase. A comprehensive...     

Critical issues in plasma-assisted vapor deposition processes

The currently used plasma-assisted vapor deposition processes are reviewed. They are analyzed in terms of the three steps in deposition processes, i.e. generation of the depositing species, transport from source to substrate, and film growth on the substrate. The role of the plasma in each of the steps for the various processes is discussed. All processes involve two sets of parameters: the plasma parameters and the process parameters. These parameters couple to a greater or lesser degree in each of the basic processes, which reflects their versatility. The roles of plasma volume chemistry and plasma diagnostics are discussed. It is clear that a deeper basic understanding of plasma-assisted deposition processes necessitates a much greater volume of work on plasma diagnostics coupled with theoretical estimates. The influence of ion bombardment on the structure, composition, and properties of the films is considered. Hybrid processes which attempt to circumvent the somewhat deleterious intercoupling of the plasma and process parameters are briefly discussed     

Tribological coatings with a chromium-based composite structure obtained by reactive deposition in vacuum

The peculiarities inherent to the chemical and phase compositions, microstructure, and tribological behavior of Cr-O, Cr-C-O, Cr-C-H and Cr-C-N-H coatings, obtained by plasma-assisted physical vapor deposition in a chemically active gas atmospheres (activated reactive deposition and magnetron sputtering methods), have been studied. It has been demonstrated that all coatings have a micro- and/or nanocomposite structure comprising nanoscale chromium-based domains, as well as chromium oxide, carbide and nitride phases with different stoichiometries. The tribological properties of the coatings investigated in a broad temperature range under unlubricated friction contact conditions, as well as their correlation with microstructures and reactive-deposition technology parameters, are discussed.     

Formation of two-component two-phase metal films at elevated temperatures

This paper is devoted to the study of two-component thin films deposited at elevated temperatures. The dependence of plasma-assisted film deposition from a flow of sputtered Cu and Fe atoms on the substrate temperature and type, concentration of sputtered components in the flow, and film thickness is investigated.     

高质量InGaN的等离子体辅助分子束外延生长和In的反常并入行为

采用射频等离子体辅助分子束外延技术生长得到了In组分精确可控且高质量的In_xGa_1-xN (x ≤ 0.2) 外延薄膜. 生长温度为580 ℃的In_0.19Ga_0.81N薄膜(10.2) 面非对称衍射峰的半高宽只有587弧秒, 背景电子浓度为3.96× 10¹⁸/cm³. 在富金属生长区域, Ga束流超过N的等效束流时, In组分不为零, 即Ga并没有全部并入外延层; 另外, 稍微增加In束流会降低InGaN的晶体质量. 关键词： InGaN 外延薄膜 射频等离子体辅助分子束外延 In 并入 晶体质量     

Correlation between pit formation and phase separation in thick InGaN film on a Si substrate

We demonstrate improved surface pit and phase separation in thick InGaN grown on a GaN/Si (111) substrate, using plasma-assisted molecular beam epitaxy with an indium modulation technique. The formation of surface pit and compositional inhomogeneity in the InGaN epilayer are investigated using atomic force microscopy, scanning electron microscopy and temperature-dependent photoluminescence. Indium elemental mapping directly reveals that poor compositional homogeneity occurs near the pits. The indium-modulation epitaxy of InGaN minimizes the surface indium segregation, leading to the reduction in pit density and size. The phase separation in InGaN with a higher pit density is significantly suppressed, suggesting that the pit formation and the phase separation are correlated. We propose an indium migration model for the correlation between surface pit and phase separation in InGaN.     

Relation between interdiffusion and polarity for MBE growth of GaN epilayers on ZnO substrates

We report on GaN growth on Zn-polar ZnO substrates using plasma-assisted molecular-beam epitaxy (P-MBE). Before GaN growth, ZnO substrate annealing conditions were optimized. Reflection high-energy electron diffraction (RHEED) patterns after low-temperature GaN buffer layer annealing changed from streaky to spotty, suggesting that zinc and oxygen atoms interdiffuse from the ZnO substrate into the GaN epilayer. This interdiffusion results in a mix-polar GaN epilayer.     

Direct fabrication of microgratings in fused quartz by laser-induced plasma-assisted ablation with a KrF excimer laser

We report precision microfabrication of fused quartz by laser ablation with a conventional UV laser for what is believed to be the first time. A high-quality micrograting structure is fabricated in fused quartz by a novel technique of laser-induced plasma-assisted ablation with a single KrF excimer laser (248 nm). The plasma generated from a metal target by laser irradiation effectively assists in ablation of the fused-quartz substrate by the same laser beam, although the laser beam is transparent to the substrate. A grating with a period of 1.06 mum is achieved by use of a phase mask. We can control the grating depth to 300 nm by changing the pulse number. This technique permits high-quality microfabrication of electronic and optoelectronic devices based on fused quartz and related silicate materials by use of a conventional UV laser.     

AlGaN nanostructures with extremely high quantum yield at 300 K

Theoretical optimization of a quantum well heterostructure based on AlGaN solid solutions is implemented in order to attain the maximum charge carrier activation energy and the maximum exciton binding energy at a radiation wavelength of ~300 nm. An optimized structure sample with the radiative recombination dominating over the temperature range of 5 to 300 K and the room temperature internal quantum yield as high as 80% of the value measured at 5 K has been manufactured via plasma-assisted molecular beam epitaxy.     

Evidence for intrinsic point defect generation during hydrogen-plasma treatment of silicon

Silicon self-interstitials are injected from the surface into the bulk during plasma-assisted ion etching of Si. In samples treated in a hydrogen plasma — due to the low surface etch-rate — the interstitials precipitate into microdefects giving rise to broad photoluminescence features. Although we cannot rule out the incorporation of hydrogen in these microdefects, we show that the occurrence of the photoluminescence depends predominabtly on the generation of intrinsic defects at the surface.     

Study of microwave plasma-assisted chemical vapor deposition of poly-and single-crystalline diamond films

We study conditions for microwave plasma-assisted chemical vapor deposition of high-quality single-crystal diamond films in a CVD reactor. These conditions are studied using the results of homoepitaxial growth of polycrystalline diamond films on diamond substrates and on the basis of numerical simulation of the microwave discharge in a CVD reactor. A high-quality single-crystal diamond layer is synthesized on a synthetic, type Ib diamond substrate. The properties of the obtained monolayer are studied by means of Raman and X-ray diffraction spectroscopy as well as optical and atomic-force microscopy.     

Effect of air and oxygen content on the dielectric barrierdischarge decomposition of chlorobenzene

Experiments were performed on the plasma-assisted decomposition of dilute concentrations of chlorobenzene in air/oxygen and argon/oxygen gas mixtures at atmospheric pressure using a coaxial geometry single dielectric barrier discharge for different oxygen concentrations and energy densities. The results show that the decomposition process requires higher energy densities using air mixtures compared to argon/oxygen mixtures and is not linearly dependent on the oxygen content for a given energy density. The main decomposition products detected in the offgas were carbon dioxide and carbon monoxide     

Surface and interface studies of GaN epitaxy on Si(111) via buffer layers

Gallium nitride films, epitaxially grown on Si(111) via a lattice-matched ZrB(2) buffer layer by plasma-assisted molecular beam epitaxy, have been studied in situ by noncontact atomic force microscopy and also in real time by reflection high-energy electron diffraction. The grown films were determined to be always N-polar. First-principles theoretical calculations modeling the interface structure between GaN(0001) and ZrB(2)(0001) clarify the origin of the N polarity.     

Structure, morphology and optical properties of SiO2−x thin films prepared by plasma-assisted pulsed laser deposition

The amorphous silicon oxide SiO_2−x thin films were prepared by the plasma-assisted pulsed laser deposition (PLD) method. X-ray diffraction spectrometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-VIS-NIR scanning spectrophotometry and ellipsometry were used to characterize the crystallinity, microscopic morphology and optical properties of obtained thin films. The influences of substrate temperatures, oxygen partial pressures and oxygen plasma assistance on the compositions of silicon oxide (SiO_2−x) thin films were investigated. Results show that the deposited thin films are amorphous and have high surface quality. Stoichiometric silicon dioxide (SiO₂) thin film can be obtained at elevated temperature of 200 °C in an oxygen plasma-assisted atmosphere. Using normal incidence transmittance, a novel and simple method has been proposed to evaluate the value of x in transparent SiO_2−x thin films on a non-absorbing flat substrate.