Dislocations and twins in Czochralski-grown gallium phosphide single crystals

An etching and electron microscopy study has been carried out on {111} oriented slices of gallium phosphide (GaP) taken from Czochralski-grown ingots. The correlation of the etched structure with substructural defects as revealed by transmission electron microscopy has been determined, It has been found that GaP grown by this technique has a high dislocation density and exhibits polygonisation and mechanical twinning. It is found that there is a one-to-one correspondence between surface etch pits and grown-in and mechanically induced dislocations. Stacking faults are also revealed in the etching studies and are shown to be twins in the matrix of the {111} 112 type. It is proposed that the twinning occurs due to the severe growth conditions and may arise by dissociation of dislocations in the sub-boundaries.     

Precise chemical analysis development for Si and GaAs surfaces

Precise chemical analysis (PCA) was developed to allow the study of non-interconnected atoms on crystalline semiconductor surfaces, such as those produced during rapid thermal processing (RTP) of silicon and electron beam lithography on gallium arsenide (GaAs). The PCA method is based on selectively dissolving the different components present on the semiconductor surface using preferential etchant solutions. After etching, the etchant solution, containing the etched component, is analyzed by a photometric technique. In this paper, we present photometric measurements of the amount of free (non-interconnected) atoms that remain on semiconductor surfaces following electron beam and RTP processing. In this context, free atoms are those presenting in any form other than crystalline GaAs or Si, for instance, those in the form of surface oxides. Using the PCA method, free Ga and As were detected on GaAs surfaces after electron beam lithography. Free silicon, boron and phosphorous atoms were found on silicon surfaces after RTP. The concentration of boron diffused into a silicon wafer during RTP was also carried out by means of slight surface etching. We estimate the accuracy of this PCA method at 2% for Ga and 5% for all other elements.     

Argon plasma treatment of glass surfaces

The effect of argon plasma treatment of glass surfaces is studied by FTIR and SEM. The argon plasma on cleaned glass surfaces resulted in increased surface area due to microetching and surface rearrangement of the silicate network as indicated by the observed changes in the Si-O stretching infrared absorption. The result was a relative increase in surface hydrophilicity which could be optimized by the plasma reaction conditions. The etching action of the argon plasma on the substrate surfaces facilitated the removal of the micrometre thick sizing from the commercial fibres accompanied by little loss in tensile strength. Plasma was also used to graft selected monomers to the surface of glass fibres for enhancement of bond compatibility in a composite system. This grafting treatment was followed by an argon etching step. The argon plasma action on the coated surfaces improved the wettability further and increased the sur face area. Changes in surface chemistry that accompanied the argon etching treatment were very subtle in the case of the plasma polymer of allylamine, but proved significant in the case of the plasma polymer of hexamethyldisiloxane. On the latter surfaces, rearrangement of the siloxane (Si-O-Si) bonds to silylmethylene (Si-(CH₂) _n -Si) groups is suggested.     

Plasma processing of PDMS based spinal implants for covalent protein immobilization,cell attachment and spreading

PDMS is widely used for prosthetic device manufacture. Conventional ion implantation is not a suitable treatment to enhance the biocompatibility of poly dimethyl siloxane (PDMS) due to its propensity to generate a brittle silicon oxide surface layer which cracks and delaminates. To overcome this limitation, we have developed new plasma based processes to balance the etching of carbon with implantation of carbon from the plasma source. When this carbon was implanted from the plasma phase it resulted in a surface that was structurally similar and intermixed with the underlying PDMS material and not susceptible to delamination. The enrichment in surface carbon allowed the formation of carbon based radicals that are not present in conventional plasma ion immersion implantation (PIII) treated PDMS. This imparts the PDMS surfaces with covalent protein binding capacity that is not observed on PIII treated PDMS. The change in surface energy preserved the function of bound biomolecules and enhanced the attachment of MG63 osteosarcoma cells compared to the native surface. The attached cells, an osteoblast interaction model, showed increased spreading on the treated over untreated surfaces. The carbon-dependency for these beneficial covalent protein and cell linkage properties was tested by incorporating carbon from a different source. To this end, a second surface was produced where carbon etching was balanced against implantation from a thin carbon-based polymer coating. This had similar protein and cell-binding properties to the surfaces generated with carbon inclusion in the plasma phase, thus highlighting the importance of balancing carbon etching and deposition. Additionally, the two effects of protein linkage and bioactivity could be combined where the cell response was further enhanced by covalently tethering a biomolecule coating, as exemplified here with the cell adhesive protein tropoelastin. Providing a balanced carbon source in the plasma phase is applicable to prosthetic device fabrication as illustrated using a 3-dimensional PDMS balloon prosthesis for spinal implant applications. Consequently, this study lays the groundwork for effective treatments of PDMS to selectively recruit cells to implantable PDMS fabricated biodevices.

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Sub‐Micron Anisotropic InP‐based III–V Semiconductor Material Deep Etching for On‐Chip Laser Photonics Devices

Two InP‐based III–V semiconductor etching recipes are presented for fabrication of on‐chip laser photonic devices. Using inductively coupled plasma system with a methane free gas chemistry of chlorine and nitrogen at a high substrate temperature of 250 °C, high aspect ratio, anisotropic InP‐based nano‐structures are etched. Scanning electron microscopy images show vertical sidewall profile of 90° ± 3°, with aspect ratio as high as 10. Atomic Force microscopy measures a smooth sidewall roughness root‐mean‐square of 2.60 nm over a 3 × 3 μm scan area. The smallest feature size etched in this work is a nano‐ring with inner diameter of 240 nm. The etching recipe and critical factors such as chamber pressure and the carrier plate effect are discussed. The second recipe is of low temperature (?10 °C) using Cl₂ and BCl₃ chemistry. This recipe is useful for etching large areas of III–V to reveal the underlying substrate. The availability of these two recipes has created a flexible III–V etching platform for fabrication of on‐chip laser photonic devices. As an application example, anisotropic InP‐based waveguides of 3 μm width are fabricated using the Cl₂ and N₂ etch recipe and waveguide loss of 4.5 dB mm^?1 is obtained.

     

Surface relief of crystalline quartz etched in a planar plasma reactor

The surface morphology of dry etched crystalline quartz was studied by transmission electron microscopy (replica technique). The experiments were carried out by reactive ion etching (RIE), plasma etching and argon sputter etching. Argon sputter etching does not alter the sample surface. RIE and plasma etching lead to surface roughness when an aluminum electrode is used. The cone-like asperities produced, typical of the beginning of etching, develop into island-like relief during a longer experiment. It is concluded that the surface roughness is caused by the combined action of backscattering of aluminum particles and their protecting effect in a CF₄ plasma.     

A Rutherford backscattering-channelling and Raman study of CuInSe2 single crystal surfaces

The (1 1 2) surfaces of Bridgman-grown p- and n-type CuInSe₂ single crystals were prepared using different polishing, etching and annealing regimes. The surfaces were subsequently studied using Rutherford backscattering-channelling (2 MeV He⁺ ions) and Raman techniques. A layer of damage below the polished surface was produced after polishing with 3 m and 1 m diamond pastes and fine 0.05 m alumina slurry. The thickness of the damaged layer depends on the polishing grade and was found to be 30 nm after 0.05 m grade polishing. Subsequent etching in a 1% Br-methanol solution removed the damaged layer after 30s. However, the etching process produced what appeared to be an Se excess in a layer close to the surface. This excess can be dissipated by annealing; also, heat treatment of unetched samples at 400 C was found to repair polish-induced damage.     

Nanometric polishing of lutetium oxide by plasma-assisted etching

Plasma-assisted etching, in which the irradiation of hydrogen plasma and inorganic acid etching are integrated, is proposed as a novel polishing method for sesquioxide crystals. By means of this approach, low damage and even damage-free surfaces with a high material removal rate can be achieved in lutetium oxide surface finishing. Analysis of transmission electron microscopy and X-ray photoelectron spectroscopy reveal that plasma hydrogenation converts the sesquioxide into hydroxide, which leads a high efficient way to polish the surfaces. The influences of process conditions on the etching boundary and surface roughness are also qualitatively investigated using scanning electron microscope and white light interferometry. The newly developed process is verified by a systematic experiment.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00324-z     

Photoelectric properties of planar structures with double Schottky barrier treated in a high-vacuum microwave discharge

The state of the surface of n-GaAs crystals upon high-vacuum microwave plasmachemical (HVMWPC) etching in various gas mixtures and the influence of the semiconductor surface condition on the photoelectric characteristics of related metal-semiconductor-metal structures with double Schottky barrier (MSMDSB structures) are investigated. Dependence of the HVMWPC etching rate of the GaAs surface on the gas mixture composition and substrate temperature is determined. It is shown that the HVMWPC etching regime strongly influences the photoelectric properties of MSMDSB structures: the treatment can lead to either growth or drop in photosensitivity of the samples. Optimum etching regimes are established for which good semiconductor surface quality and high photosensitivity of the MSMDSB structures are retained at a high etching rate.     

Surface morphology of polycrystalline diamond films etched by Ar+ beam bombardment

Polycrystalline diamond films etched by Ar⁺ beam bombardment were investigated by scanning electron microscopy and Raman spectroscopy. In an ion sputtering apparatus, an etching rate of 14 m C^–1 was obtained when 10 kV-accelerated Ar⁺ ions penetrated with an angle of 15–30° from the normal. A number of cavities were created on the surface treated at low incidence angle. In contrast, micro-prominence was seen under the condition of high incidence angle. The degree of surface roughness on etched films was also changed with the incidence angle of the beam. A relatively smooth surface appeared after the treatment with an incidence angle of 15°. Raman spectroscopy revealed that the physical etching of diamond is effective in obtaining high quality surface of polycrystalline diamond films.     

Plasma etching of polypropylene films and fibres

The introduction of a 1000 Å scale corrugated structure, aligned perpendicular to the filament axis, into oriented semi-crystalline polymers on plasma etching is shown to result from restructuring of the partially etched surface and not, as has previously been proposed, to correspond to morphological detail in the unetched material. The detail exposed on plasma etching polypropylene is shown to vary extensively with the etching conditions used. The exposed surface is compared with those resulting from peeling and chromic acid etching. Plasma etching is, however, shown to be useful in exposing coarse morphological detail such as spherulites, and in providing a convenient route for rapidly stripping the polymeric sample. The restructured partially etched surface may then be removed easily by, for example, a brief chromic acid treatment, exposing the sample interior to microscopic examination.Issued as NRCC no. 16534     

Morphological investigations of a textured black copper selective coating

The microstructural investigations of a textured black copper selective coating are reported. These surfaces possess remarkably high initial absorptance 0.97 to 0.98 and emittance ₁₀₀ 0.2 ± 0.02. These surfaces reveal a new sponge-like, porous, layered microstructure. They are made of loosely packed long and fine grains which appear randomly distributed. The copper grains are dispersed in a semiconductor oxide matrix. The spacing between these grains is of the order of solar wavelength. Also, these surfaces possess opulent solar selectivity and structural stability up to 250° C in air and under vacuum conditions.     

Structural components in needle-cokes as studied by etching with chromic acid

Structures within commercial calcined needle-cokes are characterized by optical microscopy to reveal optical texture and by scanning electron microscopy before and after etching with chromic acid solution at 400 to 423 K. The needle-cokes exhibit an optical texture of medium and coarse-grained mosaics, acicular flow domains and flow domains. The etching studies indicate that the acicular flow domains are made up of rolled and convoluted lamellae which etch to form laths (needle-like) 3 m across. The mosaics appear when the rolled structures are viewed microscopically sectioned perpendicular to the lamellae. The acicular flow domains appear in longitudinal section. The etching of the flow domains shows that they have a sedimentary structure, 1 to 2 m layer thickness, suggesting that mesophase coalesces within a layer but not between layers. A model is proposed to explain the origin and separation of structures in needle-cokes as created in the delayed coker.     

Evolution of morphology in high molecular weight polyethylene during die drawing

Deformed high molecular weight polyethylene (HMWPE) rod, formed by die drawing at 115C, was cleaved longitudinally at liquid nitrogen temperature and the cleaved surface was etched by the permanganic etching technique, A series of etched surfaces of HMWPE sections of variable draw ratio (1–13) was analysed by scanning electron microscopy (SEM), The evolution of crystalline structure in HMWPE during die drawing was observed directly. In undrawn HMWPE, the spherulites were made up of sheaf-like lamellae and scattered within an amorphous phase. During die drawing, first, microscopically inhomogeneous deformation occurred and the spherulites aligned along the drawing direction; then at a draw ratio of about 7, local melting occurred, the spherulites disintegrated and the sheaf-like lamellae oriented, followed by strain-induced recrystallization and the growth of the lamellae; finally, at a draw ratio of about 12, plastic deformation of the lamellae occurred and microfibrils were formed by drawing the lamellae.     

Characterisation of Interface-Engineered Ramp-Edge Josephson Junctions by Transmission Electron Microscopy

Interface-engineered ramp-edge junctions (IEJ) have been characterised by high-resolution transmission electron microscopy, X-ray analysis and electron energy loss spectroscopy. The IEJ are prepared by plasma etching an ion-milled YBa ₂ Cu ₃ O _7- (YBCO) ramp-edge and subsequently a top YBCO layer is deposited. The results show that the YBCO at the plasma-etched interface has a modified structure. The modified barrier structure has a pseudo cubic unit cell which is rotated 45° around the [001] axis with respect to the underlying YBCO.     

Investigation of sub-nm ALD aluminum oxide films by plasma assisted etch-through

A new technique, called “plasma defect etching” (PDE), is proposed for studying the continuity of ultra-thin layers. The PDE technique utilizes the extremely high selectivity in the deep reactive ion etching (DRIE) process, thus achieving visualization of the defects in the layer, because etching of substrate happens only through voids and microholes of the layer. The etch profile generally reproduces the non-continuous structure of the layer. This PDE technique was applied for the investigation of thin, sub-nm aluminum oxide films grown on silicon wafers by atomic layer deposition (ALD) technique. Silicon substrate was etched by SF₆ at cryogenic temperatures in an inductively coupled plasma (ICP) reactor, exploiting the extremely high ratio of silicon/aluminum oxide etch rates in fluorine plasmas. The surface morphology was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The PDE method shows that in the case of water as an oxidation precursor, separate islands of aluminum oxide form during the five first ALD cycles. On the other hand, the use of ozone precursor helps to oxidize silicon surface and facilitates growth of a uniform layer.     

Structure of nickel-doped α-FeOOH

Colloidal particles of nickel-doped-FeOOH prepared under varied conditions were characterized using transmission electron microscopy, X-ray diffraction thermogravimetry-differential thermal analysis, Fourier transform infrared analysis, inductively coupled plasma spectroscopy and nitrogen adsorption. The unit cell dimensions of the resulting-FeOOH slightly changed on doping with nickel. Both the total and surface hydroxyl ions decreased with increasing amounts of nickel. The nickel content in the surface layer determined by X-ray photoelectron spectroscopy was larger than the total nickel content determined by inductively coupled plasma spectroscopy. The results obtained indicate that the substitution of iron with nickel took place in the surface layer more than in the internal phase.     

Application of ion-etching of grooves into quartz for surface acoustic wave devices

The application of r.f.-sputter etching techniques to the fabrication of grooves in the surface of quartz is reported. This process has been used for the construction of devices which employ the interaction of surface acoustic waves with arrays of well-defined parallel grooves. Devices have been produced with grooves up to 2.5 m deep, which have substantially rectangular profiles and controllable mark-to-space ratios. The groove geometries have been characterized using Talysurf, optical microscopy, SEM and TEM techniques.     

Surface degradation features and microstructural properties of ultra-high molecular weight polyethylene (UHMWPe)

Surface degradation of UHMWPe is recognized as a leading clinical concern, limiting the long-term performance in total knee replacements. Eight retrieved tibial plateaux and six wear screening test samples were evaluated for surface degradation features and microstructural features. The surface degradation features were assessed using stereomicroscopy and scanning electron microscopy. Microstructural features were evaluated using optical microscopy of thin cross-sections and a permanganate etching technique. The pitting mechanism of wear was observed on all eight retrieved TKR and covered an average of 12.6% of the surface area. The size of the pits were similar to the size of grains observed in the microstructural evaluation – approximately 100 to 200 m. The presented observations of pitting in retrieved knee implants have shown that the post-processing microstructure may influence this mechanism of surface degradation and hence the wear products.     

Synthesis of HDLC films from solid carbon

Diamond-like carbon (DLC) films were synthesized on silicon substrates from solid carbon by a very low power (60 W) microwave plasma chemical vapor deposition (MPCVD) reaction of a mixture of 90–70% helium and 10–30% hydrogen. It is proposed that He⁺ served as a catalyst with atomic hydrogen to form an energetic plasma. The average hydrogen atom temperature of a helium-hydrogen plasma was measured to be up to 180–210 eV versus 3 eV for pure hydrogen. Bombardment of the carbon surface by highly energetic hydrogen formed by the catalysis reaction may play a role in the formation of DLC. The films were characterized by time of flight secondary ion mass spectroscopy (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. TOF-SIMS identified the coatings as hydride by the large H⁺ peak in the positive spectrum and the dominant H^– in the negative spectrum. The XPS identification of the H content of the CH coatings as a novel hydride corresponding to a peak at 49 eV has implications that the mechanism of the DLC formation may also involve one or both of selective etching of graphitic carbon and the stabilization of sp ³-bonded carbon by the hydrogen catalysis product. Thus, a novel H intermediate formed by the plasma catalysis reaction may enhance the stabilization and etching role of H used in past methods.