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Chemical Etching (chemical + etching)

Distribution by Scientific Domains

Physics and Astronomy	53%
Polymers and Materials Science	36%
Medical Sciences	6%

Kinds of Chemical Etching

wet chemical etching

Selected Abstracts

Cover Picture: J. Biophoton.

JOURNAL OF BIOPHOTONICS, Issue 4 2010
4/2010
Glass substrate after femtosecond laser irradiation of six devices that will be obtained by six cuts along the transversal straight lines and a further orthogonal one. Chemical etching will create micro-channels where the more complex structures have been irradiated, while not affecting the inscribed optical waveguides. The devices will then be used for optical trapping and stretching of cells. (Picture: F. Bragheri et al., pp. 234,243 in this issue) [source]

Growth, etching morphology and spectra of LiAlO2 crystal

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2008
Taohua Huang
Abstract ,-LiAlO2 single crystal was successfully grown by Czochralski method. The crystal quality was characterized by X-ray rocking curve and chemical etching. The effects of air-annealing and vapor transport equilibration (VTE) on the crystal quality, etch pits and absorption spectra of LiAlO2 were also investigated in detail. The results show that the as-grown crystal has very high quality with the full width at half maximum (FWHM) of 17.7-22.6 arcsec. Dislocation density in the middle part of the crystal is as low as about 3.0×103 cm,2. The VTE-treated slice has larger FWHM value, etch pits density and absorption coefficient as compared with those of untreated and air-annealed slices, which indicates that the crystal quality became inferior after VTE treatment. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Habit modification and improvement in properties of potassium hydrogen phthalate (KAP) crystals doped with metal ions

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2006
S. K. Geetha
Abstract Potassium hydrogen phthalate (KAP) single crystals were grown by slow evaporation and slow cooling techniques. The growth procedure like temperature cooling rate, evaporation rate, solution pH, concentration of the solute, supersaturation ratio etc., has been varied to have optically transparent crystals. Efforts were made to dope the KAP crystals with rubidium, sodium and lithium ions. The dopant concentration has been varied from 0.01 to 10 mole percent. Good quality single crystals were grown with different concentrations of dopants in the mother phase. Depending on the concentration of the dopants and the solution pH value, there is modification of habit. Rubidium ions very much improve the growth on the prismatic faces. The transparency of the crystals is improved with rubidium and sodium doping. The role of the dopants on the non-linear optical performance of KAP indicates better efficiency for doped crystals. The grown crystals were characterized with XRD, FT-IR, chemical etching, Vickers microhardness and SHG measurements. The influence of the dopants on the optical, chemical, structural, mechanical and other properties of the KAP crystals was analysed. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source]

Homoepitaxy of ZnTe on (100) oriented substrates: Technology issues and MOVPE growth aspects

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005
M. Traversa
Abstract The metalorganic vapour phase epitaxy of ZnTe on single crystal (100)ZnTe:P wafers is reported. The technological steps to prepare a substrate surface suitable for the high quality homoepitaxy of ZnTe are identified and optimised in terms of structural and morphological properties of overgrown epilayers. Removal of ,7 µm of material from the ZnTe:P wafers by chemical etching in 1% Br2 -methanol solution proved necessary to achieve a sufficiently smooth and homogeneous surface; in-situ H2 heat treatment of the wafers at 350°C immediately before growth ensures optimal desorption of residual oxides, allowing epilayer crystalline quality comparable to the substrate. However, the structure of epilayers degrades for growth temperatures (TG) above 350 °C due to the occurrence of stacking faults (SFs) within ,200-300 nm from the epilayer-substrate interface. Accordingly, the epilayer band-edge luminescence vanishes below 350 nm, indicating a worsening of the material radiative efficiency in very thin epilayers. The epilayer surface morphology is the result of a complex interplay between SF nucleation and Te:Zn ad-atom stoichiometry during growth. Almost featureless morphologies are obtained for growth at 350 °C, i.e. under nearly stoichiometric surface conditions. Pyramid-like hillocks develop instead for TG , 360 °C, corresponding to Te-rich surface conditions, their density rapidly increasing up to around 9 × 106 cm,2 at TG = 400 °C. Hillocks occur in close pairs on the epilayer surface, their nucleation being strongly reduced if a thin ZnTe buffer layer is grown at low (325 °C) temperature, i.e. if SFs do not occur at the epilayer-substrate interface. This demonstrates that hillocks form as a result of three-dimensional growth around partial dislocations pairs bounding SFs, the phenomenon being driven by Te ad-atoms experiencing a Schwoebel potential barrier at the surface step edges around the dislocations. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Development of a 3-dimensional LIGA process and application to fabricate a spiral microcoil

ELECTRICAL ENGINEERING IN JAPAN, Issue 1 2009
Harutaka Mekaru
Abstract LIGA process has been developed in the 2.5-dimensional world. We introduced new technologies of a 3D X-ray lithography and a worm injection molding with an unscrewing de-molding mechanism, and succeeded in the deployment of a 3D LIGA process. Furthermore, we fabricated a spiral microcoil using the 3D-LIGA process and a metallization technique combining flat and smooth electroplating and isotropic chemical etching. The microcoil diameter was 0.5 mm and the length was 1 mm. The width of coil lines was 10µm and the pitch was 20µm. Characteristics of this microcoil as an inductor combine the inductance of 91 nH and the quality factor of 5.8 at the frequency of 1 GHz. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 43,51, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20679 [source]

Effects of a fluoride etchant on resin bonding to titanium-aluminum-niobium alloy

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2004
Hiroaki Yanagida
This investigation was carried out in order to evaluate ammonium hydrogen fluoride (AHF) and cupric chloride (CC) as components of a metal etchant. The surface of cast titanium-aluminum-niobium (Ti-6Al-7Nb) was air-abraded with alumina, etched for 10 s, and rinsed with water. A phosphate or a thiophosphate primer was applied to the bonding area, and an acrylic rod was bonded to the specimen with a tri- n -butylborane-initiated self-curing luting agent. Shear bond strengths were determined after thermocycling (4°C and 60°C) for 10,000 cycles. The average bond strength was significantly influenced by thermocycling, AHF, and primer, but was not influenced by CC. The maximum average bond strengths were obtained when the etchant consisted of 5mass% AHF, with and without 0.3mass% CC. Microphotographs showed that numerous micropits were created on the etched surface, suggesting increased micromechanical retention. In conclusion, chemical etching with 5mass% AHF significantly improved the durability of resin bonding to Ti-6Al-7Nb. [source]

Heterointegration of Pt/Si/Ag Nanowire Photodiodes and Their Photocatalytic Properties

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
Yongquan Qu
Abstract Photocatalyst mediated photoelectrochemical processes can make use of the photogenerated electrons and holes onsite for photocatalytic redox reactions, and enable the harness and conversion of solar energy into chemical energy, in analogy to natural photosynthesis. However, the photocatalysts available to date are limited by either poor efficiency in the visible light range or insufficient photoelectrochemical stability. Here, it is shown that a Pt/Si/Ag nanowire heterostructure can be rationally synthesized to integrate a nanoscale metal-semiconductor Schottky diode encased in a protective insulating shell with two exposed metal catalysts. The synthesis of Pt/Si/Ag nanowire diodes involves a scalable process including the formation of silicon nanowire array through wet chemical etching, electrodeposition of platinum and photoreduction of silver. The Pt/Si/Ag diodes exhibit highly efficient photocatalytic activity for a wide range of applications including environmental remediation and solar fuel production in the visible range. In this article, photodegradation of indigo carmine and 4-nitrophenol are used to evaluate the photoactivity of Pt/Si/Ag diodes. The Pt/Si/Ag diodes also show high activity for photoconversion of formic acid into carbon dioxide and hydrogen. [source]

Heterointegration of Pt/Si/Ag Nanowire Photodiodes and Their Photocatalytic Properties

Self-Assembled In-Plane Growth of Mg2SiO4 Nanowires on Si Substrates Catalyzed by Au Nanoparticles

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2010
Zhou Zhang
Abstract In-plane growth of Mg2SiO4 nanowires on Si substrates is achieved by using a vapor transport method with Au nanoparticles as catalyst. The self-assembly of the as-grown nanowires shows dependence on the substrate orientation, i.e., they are along one, two, and three particular directions on Si (110), (100), and (111) substrates, respectively. Detailed electron microscopy studies suggest that the Si substrates participate in the formation of Mg2SiO4, and the epitaxial growth of the nanowires is confined along the Si <110> directions. This synthesis route is quite reliable, and the dimensions of the Mg2SiO4 nanowires can be well controlled by the experiment parameters. Furthermore, using these nanowires, a lithography-free method is demonstrated to fabricate nanowalls on Si substrates by controlled chemical etching. The Au nanoparticle catalyzed in-plane epitaxial growth of the Mg2SiO4 nanowires hinges on the intimate interactions between substrates, nanoparticles, and nanowires, and our study may help to advance the developments of novel nanomaterials and functional nanodevices. [source]

Surface-Protected Etching of Mesoporous Oxide Shells for the Stabilization of Metal Nanocatalysts

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010
Qiao Zhang
Abstract Nanoparticles of transition metals, particularly noble metals, are widely used in catalysis. However, enhancing their stability during catalytic reactions has been a challenge that has limited the full use of the benefits associated with their small size. In this Feature Article, a general "encapsulation and etching" strategy for the fabrication of nanocatalyst systems is introduced in which catalyst nanoparticles are protected within porous shells. The novelty of this approach lies in the use of chemical etching to assist the creation of mesopores in a protective oxide shell to promote efficient mass transfer to encapsulated metal nanoparticles. The etching process allows for the direct transformation of dense silica coatings into porous shells so that chemical species can reach the catalyst surface to participate in reactions while the shells act as physical barriers against aggregation of the catalyst particles. By using the surface-protected etching process, both yolk,shell and core,satellite type nanoreactors are synthesized and their utilization in liquid- and gas-phase catalysis is demonstrated. The thermal and chemical stability of the metallic cores during catalytic reactions is also investigated, and further work is carried out to enhance recyclability via the introduction of superparamagnetic components into the nanoreactor framework. [source]

Fabrication of Flexible Binary Amplitude Masks for Patterning on Highly Curved Surfaces

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009
Audrey M. Bowen
Abstract This paper describes soft lithography methods that expand current fabrication capabilities by enabling high-throughput patterning on nonplanar substrates. These techniques exploit optically dense elastomeric mask elements embedded in a transparent poly(dimethylsiloxane) (PDMS) matrix by vacuum-assisted microfluidic patterning, UV,ozone-mediated irreversible sealing, and chemical etching. These protocols provide highly flexible photomasks exhibiting either positive- or negative-image contrasts, which serve as amplitude masks for large-area photolithographic patterning on a variety of curved (and planar) surfaces. When patterning on cylindrical surfaces, the developed masks do not experience significant pattern distortions. For substrates with 3D curvatures/geometries, however, the PDMS mask must undergo relatively large strains in order to make conformal contact. The new methods described in this report provide planar masks that can be patterned to compliantly compensate for both the displacements and distortions of features that result from stretching the mask to span the 3D geometry. To demonstrate this, a distortion-corrected grid pattern mask was fabricated and used in conjunction with a homemade inflation device to pattern an electrode mesh on a glass hemisphere with predictable registration and distortion compensation. The showcased mask fabrication processes are compatible with a broad range of substrates, illustrating the potential for development of complex lithographic patterns for a variety of applications in the realm of curved electronics (i.e., synthetic retinal implants and curved LED arrays) and wide field-of-view optics. [source]

Cover Picture: Photolithographic Route to the Fabrication of Micro/Nanowires of III,V Semiconductors (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2005
Mater.
Abstract The cover shows a patterned assembly of GaAs nanowires with their ends tethered to a bulk single-crystal wafer as described on p.,30 by Rogers and co-workers. These wires, which have triangular cross-sections, were fabricated via a top,down process that combines photolithography and anisotropic chemical etching. Nano/microwires of semiconducting materials (e.g., GaAs and InP) with triangular cross-sections can be fabricated by "top,down" approaches that combine lithography of high-quality bulk wafers (using either traditional photolithography or phase-shift optical lithography) with anisotropic chemical etching. This method gives good control over the lateral dimensions, lengths, and morphologies of free-standing wires. The behaviors of many different resist layers and etching chemistries are presented. It is shown how wire arrays with highly ordered alignments can be transfer printed onto plastic substrates. This "top,down" approach provides a simple, effective, and versatile way of generating high-quality single-crystalline wires of various compound semiconductors. The resultant wires and wire arrays have potential applications in electronics, optics, optoelectronics, and sensing. [source]

Nanoparticle Arrays on Surfaces Fabricated Using Anodic Alumina Films as Templates,

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2003
M.S. Sander
Abstract High density nanoparticle arrays on surfaces have been created using a template-assisted approach. Templates were produced by evaporating aluminum onto substrates and subsequently anodizing the aluminum to produce nanoporous alumina films. The resulting templates have a narrow distribution of pore sizes tunable from ,,25 to ,,70 nm. To demonstrate the flexibility of this approach for producing nanoparticle arrays on various substrates, templates have been fabricated on silicon oxide, silicon, and gold surfaces. In all cases, a final chemical etching step yielded pores that extended completely through the template to the underlying substrate. Because the templates remain in intimate contact with the substrate throughout processing, they may be used with either vacuum-based or wet chemical deposition methods to direct the deposition of nanoparticles onto the underlying substrates. Here we have produced gold nanodot arrays using evaporation and gold nanorod arrays by electrodeposition. In each case, the diameter and height of the nanoparticles can be controlled using the confining dimensions of the templates, resulting in high density (,,1010,cm,2) arrays of nanoparticles over large areas (>,1 cm2). [source]

Dual Templating Synthesis of Mesoporous Titanium Nitride Microspheres,

ADVANCED MATERIALS, Issue 31 2009
Jin Ho Bang
Hierarchically nanostructured titanium nitride is prepared via a novel and facile in situ dual templating approach. No prestructured templates are necessary; instead, a template is generated in situ during the synthesis from a liquid core and the resulting spherical shell, and the template is removed in the final heating without any additional chemical etching. [source]

Stamps for Submicrometer Soft Lithography Fabricated by Capillary Force Lithography ,

ADVANCED MATERIALS, Issue 13 2004
M. Bruinink
A convenient, inexpensive technique for fabrication of stamps for submicrometer soft lithography from masters with micrometer-size features is presented. Templates fabricated by capillary-force lithography are robust against replica molding of stamps. The Figure shows the resulting metal structure after employing such a second-generation stamp in microcontact printing of octadecanethiol and subsequent wet chemical etching of the underlying gold. [source]

Fabrication of Large-Area Silicon Nanowire p,n Junction Diode Arrays,

ADVANCED MATERIALS, Issue 1 2004
K. Q. Peng
Large-area silicon nanowire p,n junction diode arrays (see Figure) have been fabricated by chemical etching of planar silicon p,n junction wafers in aqueous HF solution that contains appropriate amounts of silver nitrate near room temperature. The I,V characteristics have been measured using current-sensing atomic force microscopy, and nonlinear and rectifying electrical transport behavior has been observed. [source]

Comparative corrosion performance of black oxide, sandblasted, and fine-drawn nitinol wires in potentiodynamic and potentiostatic tests: Effects of chemical etching and electropolishing

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2004
Svetlana Shabalovskaya
Abstract The corrosion performance of sandblasted (SB) and smooth fine-drawn (FD) medical-use nitinol wires was compared with the performance of wires with black oxide (BO) formed in air during their manufacture. Potentiodynamic and ASTM F746 potentiostatic tests in a 0.9 % NaCl solution were conducted on wires in their as-received, chemically etched, aged in boiling water, and electropolished states. As-received wires with various surface finishes revealed breakdown potentials in the range from ,100 mV to +500 mV; similar passive current density, 10,6 A/cm2; and a wide hysteresis on the reverse scan, demonstrating strong susceptibility to localized corrosion. Chemically etched wires with original black oxide displayed consistent corrosion performance and surpassed, in corrosion resistance, electropolished wires that showed significantly lower breakdown (400,700 mV) and localized corrosion potentials (,,50 to +113 mV). Sandblasted and fine-drawn wires exhibited rather inconsistent corrosion behavior. In potentiodynamic tests these wires could perform with equal probability either on the level of pretreated BO wires or rather similar to as-received wires. Both SB and FD wires revealed low breakdown potentials in the PS regime. SEM analysis performed before tests indicated that sandblasting was not efficient for the complete removal of the original scaling, and fine drawing aggravated the situation, resulting in a persistent scaling that contributed to the inferior corrosion performance. Inclusions (oxides, carbides, and oxidized carbides) inherited from the bulk and retained on electropolished surfaces are the cause of their inferior performance compared to chemically etched surfaces. In electropolished wires corrosion was initiated around inclusions. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 69B: 223,231, 2004 [source]

Site-selective anodic etching of InP substrate using self-organized spheres as mask

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2010
Takayuki Yokoyama
Abstract Ordered microstructures were formed on an InP substrate by metal-assisted chemical etching or anodic etching using a layer of colloidal crystals consisting of polystyrene spheres as a mask. When the metal-assisted chemical etching of the InP substrate was carried out in a mixed solution of H2SO4/H2O2 using a Pt honeycomb pattern as a catalyst, obtained by ion sputtering through the mask on the substrate, InP column arrays with a close-packed configuration having an ordered periodicity were formed. Furthermore, by anodic etching at the optimum HCl concentration with a layer of colloidal crystals as a mask, InP disk arrays or pillar arrays were fabricated. [source]

Towards optical-quality nanocrystalline diamond with reduced non-diamond content

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2009
Z. Remes
Abstract Our nominally undoped nanocrystalline diamond (NCD) films were deposited on fused silica substrates by the microwave plasma enhanced chemical vapor deposition (MW CVD) at a relatively low temperature below 600,°C. They show high dark resistivity and measurable photosensitivity after surface oxidation. We present the "true" optical absorptance spectra calculated from transmittance T and reflectance R measurements corrected on the surface scattering and compare them with the normalized photocurrent spectra. The optical scattering does not allow to evaluate the small optical absorption in visible and near IR range from the T and R spectra. The photocurrent spectra were measured in the ultraviolet, visible, and near infrared optical range using the dual beam photocurrent spectroscopy (DBP) under constant UV illumination. Previously, NCD films often showed non-diamond content with the photo-ionization threshold at 0.8,eV increasing significantly the optical absorption in near IR and visible region. Here, we show that the non-diamond content can be reduced by several orders of magnitude by depositing NCD on the carefully selected UV-grade fused silica substrates under the optimized growth conditions followed by the post-deposition chemical etching and cleaning. Unlike the NCD layers with high non-diamond content, the NCD layers with reduced non-diamond content are stable up to 450,°C. [source]

Structural changes in Si crystals exposed to chemical etching and ion implantation

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2009
I. Fodchuk
Abstract Results of X-ray diffraction studies on structural changes in Si crystals caused by chemical etching for 40,s in HF, HNO3 solution and phosphorus-ion implantation with the energy E,=,100,keV and dose D,=,8,×,1014,cm,2 are represented. Two- and three-crystal X-ray diffractometry methods are used for a quantitative assessment of structural changes occurring in the near-surface crystal layers. Analysis of experimental rocking curves was made with the use of different approaches developed on the basis of kinematic and dynamic theory of X-ray scattering in the imperfect crystals. A model of possible system of structural defects in the near-surface silicon layers modified by chemical etching and ion implantation is proposed. The model accounts for the availability of respective sizes and concentrations of spherical and disc-shaped cluster formations, dislocation loops. [source]

Top-down processed silicon nanowire transistor arrays for biosensing

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2009
Xuan Thang Vu
Abstract We describe the fabrication, electrical and electrochemical characterization of silicon nanowire arrays, which were processed in a top-down approach using combined nanoimprint lithography and wet chemical etching. We used the top silicon layer as contact line and observed an influence of implantation and subsequent annealing of these lines to the device performance. In addition we found a subthreshold slope dependence on wire size. When operated in a liquid environment, wires can be utilized as pH sensors. We characterized the pH sensitivity in the linear range and in the subthreshold operation regime. As a first proof-of-principle experiment for the later use of the sensors in bioassays, we monitored the buildup of polyelectrolyte multilayers on the wire surface. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Preparation of extended microtunnels in GaN by wet chemical etching

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007
Hsin-Hsiung Huang
Abstract Extended microtunnels with triangular cross sections are demonstrated in GaN layers on sapphire substrates. The depths of the tunnels can easily reach several hundred micrometers by using wet chemical etching. To obtain this result, patterned growth of specially designed GaN layers is carried out on sapphire substrates with metalorganic chemical vapor deposition and subsequently hydride vapor-phase epitaxy techniques. The prepared samples are then chemically etched in molten potassium hydroxide, and microtunnels with triangularly etched cross sections are formed. The planes of the triangular bevels belong to the {112} family. The etch rate of the tunnel can be as high as 10 ,m/min under proper etching conditions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Controlled Ge quantum dots positioning with nano-patterned Si(001) substrates

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2006
A. Bavard
Abstract A square nanometric patterned substrate (period 20 nm) is obtained by direct twist bonding of two twin Si(001) surfaces, thinning and preferential chemical etching. Molecular beam epitaxy of Ge is carried out on a sample having heterogeneous trench depths to analyse islands positioning as a function of the surface morphology. Scanning electron microscopy observations show that small single dots per mesa or large dots covering several mesas can be observed. It highlights the influence of the mesa aspect ratio on the control of Ge islands self-organization, and suggests the occurrence of an effective activation barrier depending on the surface profile. The position-dependent energy stored in a dot for a given surface profile is estimated from a very simple model based on the balance between capillarity and elastic relaxation terms. By choosing a cycloid-like profile, experimental observations can be explained without fitting parameters. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Structural and optical properties of ZnSe-based diluted magnetic semiconductor quantum-well wire arrays by wet chemical etching

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010
Tsutomu Muranaka
Abstract The ZnSe-based mesa structures with well-defined and smooth facets were successfully demonstrated by using molecular beam epitaxy (MBE) and wet chemical etching. The ZnSe structures were found to be bound by (111) and (-1-11) facets along the [-110] direction, and bound by (1-11) and (-111) facets along the [110] direction, respectively. The intensities of the non-polarized PL peaks from the [-110]- and [110]-oriented QWW structures were almost proportional to the unetched region and additional decreases were not observed. The PL peaks from the QWW structures were found to be highly polarized when the polarization angle was aligned parallel to the wire direction. The degrees of the linear polarization were 18% for the [-110]-oriented QWW structure and 26% for the [-110]-oriented QWW structure, respectively. The results of the PL and magneto-PL measurements show no process-induced damage to degrade magneto-optical performance of the DMS structures by using this method. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Improved luminescence efficiency of InAs quantum dots grown on atomic terraced GaAs surface prepared with in-situ chemical etching

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2009
Yasuhiro Idutsu
Abstract Observation of the enhanced luminescence efficiency of InAs quantum dots (QDs) grown on atomically controlled GaAs surfaces is reported. With the trisdimethylaminoarsenic (TDMAAs) in-situ surface etching process, formation of atomic steps and terraces on GaAs surfaces were clearly observed. InAs QDs grown on the processed GaAs surfaces showed the clear dependence of QDs size, density and optical characteristics on the surface properties, i.e., the increase of the QDs height and diameter the decrease of the QDs density. About 6-times enhancement of photoluminescence efficiency which has the peak around 1550-nm wavelength was observed by growing InAs QDs on atomically controlled GaAs surfaces. This is due to the migration enhancement of InAs during thegrowth the QDs. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Defect-selective etching of aluminum nitride single crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007
M. Bickermann
Abstract We have investigated defect-selective wet chemical etching of freestanding AlN single crystals in a molten NaOH-KOH eutectic at temperatures ranging from 240 °C to 400 °C. On nitrogen polar basal planes, hexagonal pyramids/hillocks exceeding 100 µm in diameter may form within seconds of etching at 240 °C. They sometimes are arranged in lines and clusters, thus we attribute them to defects on the surface, presumably originating in the bulk material. On aluminum polar basal planes, the etch pit density after approx. 2,3 min of total etching time at 350 °C corresponds to the screw dislocation density. Additionally, significantly smaller etch pits were found around annealed indentations, in the vicinity of some bigger etch pits after repeated etching, and sometimes also isolated on the surface area. We attribute these etch pits to threading mixed and edge dislocations. On as-grown rhombohedral and prismatic facets no defect-related etching features were observed. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]