Search

At the end of range of MeV ions in diamond, black spots are created corresponding to the Bragg peak in the stopping power; the characteristics of which are not well understood but may have application in the micromachining of diamond, quantum state storage and diamond based photonic devices. This paper reports on the initial findings of studies to determine the physical properties of these buried black spots, while exploring how to optimally fabricate microstructures within the diamond. The authors have created buried 3-D structures in single crystal diamond by means of deep implantation with a focussed ion microbeam, over a wide range of fluences. Characterization is performed with confocal Raman spectroscopy.

This paper presents a technique to expose and characterize nano-structured hole arrays in tapered photonic crystal fibers. Hole array structures are examined with taper outer diameters ranging from 12.9 microm to 1.6 microm. A combined focused ion beam milling and scanning electron microscope system was used to expose and characterize the arrayed air-silica structures. Results from this combined technique are presented which resolve hole-to-hole pitch sizes and hole diameters in the order of 120 nm and 60 nm, respectively.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Ion assisted deposition (IAD) has been investigated for the growth of GaN, and the resulting films studied by x-ray diffraction and absorption spectroscopy and by transmission electron microscopy. IAD grown stoichiometric GaN consists of random-stacked quasicrystals of some 3 nm diameter. Amorphous material is formed only by incorporation of 15% or more oxygen, which we attribute to the presence of non-tetrahedral bonds centered on oxygen. The ionic favourability of heteropolar bonds and its strikingly simple constraint to even-membered rings is the likely cause of the instability of stoichiometric a-GaN., Comment: 4 pages, 3 figures

Implantation of hydrogen ions into synthetic single–crystal diamonds followed by subsequent high–temperature annealing and anodic etching of implanted crystals was used to obtain structurally perfect 30–nm thick diamond membranes with optically active NV− centres (area up to several tens mm²) appropriate for use in integral magnetometers and quantum–informatics optoelectronic circuits.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Focused ion beam (FIB) systems have been widely used over the last two decades for crosssectional and plan-view TEM specimen preparation. However, an inevitable result of the FIB preparation process is the formation of the damage layers on the sides of the final thin electron transparent membrane, which reduces the quality of the TEM imaging and limits the minimal useful specimen thickness [1]. The knowledge of the thickness of the damage layers is critical because it allows to estimate the value of undamaged material in the FIB prepared samples. In many works [25] the damage in the FIB prepared samples is attributed to the amorphous layers created during the FIB preparation process and its thickness was estimated on the basis of popular TRIM program [6]. Using TRIM the projected range (Rp) of implanted ions can be calculated for the particular type of ions, ion energy, target material and incident angle. The value of Rp is commonly used for the estimation of the thickness of the amorphous damage layer in the FIB prepared TEM samples [2-4]. However, the experimentally obtained thickness of the amorphous damage layers in the silicon and other materials [2, 5] was nearly twice larger than the TRIM calculated data for projected range.

The enhancement of the critical current density ( J c ) has been achieved by introducing (Y/Nd)Ba 2 Cu 3 O 7 [(Y/Nd)BCO] multilayered structure into relatively thick films (∼1000 nm) produced by pulsed-laser deposition. The microstructure of the multilayered systems obtained has been shown to improve from the bottom to the top layers, producing dislocations at the interfaces. The (Y/Y)BCO single-element multilayered deposition is also shown to comparably increase J c , which is attributed to the extended time of particle mobility creating “multilayered” interfaces and acting in a similar way as for the (Y/Nd)BCO interfaces.

Thin membranes with excellent optical properties are essential elements in diamond based photonic systems. Due to the chemical inertness of diamond, ion beam processing must be employed to carve photonic structures. One method to realize such membranes is ion-implantation graphitization followed by chemical removal of the sacrificial graphite. The interface revealed when the sacrificial layer is removed has interesting properties. To investigate this interface, we employed the surface sensitive technique of grazing angle channeled Rutherford backscattering spectroscopy. Even after high temperature annealing and chemical etching a thin layer of damaged diamond remains, however, it is removed by hydrogen plasma exposure.

We have investigated the nature of the residual damage in diamond crystals following the ion implantation/graphitization “lift-off” process, using near-edge x-ray absorption fine structure spectroscopy and transmission electron microscopy. A defective but crystalline interface is found, which displays dense pre-edge unoccupied states and an almost complete loss of the core-level C 1s exciton signature. This residual crystalline damage is resistant to standard chemical etching, however a hydrogen plasma treatment is found to completely recover a pristine diamond surface. Analysis and removal of residual ion-induced damage is considered crucial to the performance of many diamond device architectures.

The technique for the preparation of specimens for transmission electron microscopy (TEM) using the focused ion beam (FIB) miller typically consists of a series of milling steps performed over both sides of an area of interest until an electron transparent membrane is achieved [1]. This process is often accompanied by the formation of damage layers on the surfaces of the specimen. The origins of any damage layer are still not clear. On one hand the process of amorphisation of the target material by the highly energetic ion beam is well known. Alternatively, other workers have reported that this damage layer can be connected with redeposition of milled material. [2,3]. in this paper we have studied redeposition effects during FIB milling of silicon TEM specimens.A FEI xP200 FIB system with a Ga+ ion source operating at 30 kV was used in this work. to study redeposition effects a row of trenches on a silicon specimen was milled under different beam currents ranging from 1000 to 6600 pA. The size of such trenches was 15x10 μm wide and 1 μm deep. The specimen was then removed from the FIB and sputter coated with a ∼50-100 nm thick Au film to preserve the trench surfaces from further damage during subsequent milling. The specimen was then placed back in the FIB system and a second set of trenches 5×8 μm wide and 0.6 μm deep was milled on the bottom of first set of trenches (Fig. 1a). The specimens were sputter coated with Au again and were placed back in the FIB system and the trenches were then covered with 1 μ thick Pt strips using the metal deposition facility of the FIB. The presence of these protection layers (Au and Pt) ensures that the final TEM specimen have unmodified original damage layers resulting from the initial milling steps. Cross-sectional TEM specimens of the trench walls were then prepared using normal FIB procedures (Fig. 1b) [2].

In this communication we present our response to the recent comment of A. Engel regarding our paper on FIB- fabricated Nb nanowires (see Vol. 20 (2009) Pag. 465302). After further analysis and additional experimental evidence, we conclude that our interpretation of the experimental results in light of QPS theory is still valid when compared with the alternative proximity-based model as proposed by A. Engel.

Carbon ions of MeV energy were implanted into sapphire to fluences of 1×1017 or 2×1017cm−2 and thermally annealed in forming gas (4% H in Ar) for 1h. Secondary ion mass spectroscopy results obtained from the lower dose implant showed retention of implanted carbon and accumulation of H near the end of range in the C implanted and annealed sample. Three distinct regions were identified by transmission electron microscopy of the implanted region in the higher dose implant. First, in the near surface region, was a low damage region (L1) composed of crystalline sapphire and a high density of plateletlike defects. Underneath this was a thin, highly damaged and amorphized region (L2) near the end of range in which a mixture of i-carbon and nanodiamond phases are present. Finally, there was a pristine, undamaged sapphire region (L3) beyond the end of range. In the annealed sample some evidence of the presence of diamond nanoclusters was found deep within the implanted layer near the projected range of the C ions....

The effect of temperature in the 293–473 K range, on the secondary electron emission (SEE) yield of single crystal and polycrystalline diamond film surfaces is reported. For the polycrystalline films the SEE yield was found to decay as function of electron irradiation dose while for the single crystal an increase occurs first, followed by a decrease. For both surfaces, the SEE yield increases significantly upon heating and obtained a nearly constant value with electron dose at 473 K. These effects are explained as due to the temperature dependence of the electron beam induced hydrogen desorption and surface band bending.

The influence of high temperature annealing up to 1200 °C in vacuum on ∼100 nm nearly continuous thick diamond films consisting of 30–50 nm crystallites, deposited onto silicon substrates is reported. The hydrogen bonding and phase composition of the films were studied with Raman spectroscopy, while the surface microstructure and composition were studied with high resolution scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS), respectively. Annealing to 800–900 °C of ∼100 nm thick films results in a decrease in the intensities of the peaks associated with hydrogen bonding (Raman), as well as changes to the morphological microstructure at the film surface. Heating the films to 1000 °C resulted in the complete disappearance of the Raman peaks associated with hydrogen bonding at grain boundaries, and an increase in the relative intensity of the diamond peak relative to the graphite-related D and G Raman peaks, concomitant with changes to the ...

The effect of temperature on the stability of the secondary electron emission (SEE) yield from ∼100-nm-thick continuous diamond films is reported. At room temperature, the SEE yield was found to decay as a function of electron irradiation dose. The SEE yield is observed to increase significantly upon heating of the diamond surface. Furthermore, by employing moderate temperatures, the decay of the SEE yield observed at room temperature is inhibited, showing a nearly constant yield with electron dose at 200 °C. The results are explained in terms of the temperature dependence of the electron beam-induced hydrogen desorption from the diamond surface and surface band bending. These findings demonstrate that the longevity of diamond films in practical applications of SEE can be increased by moderate heating.

Excitation and localization of surface plasmon polariton modes in metal-dielectric structures can be utilized to construct nanophotonic materials and devices with tuneable optical dispersion. We present a selective polariton generator (SPG) device that demonstrates switching of light transmission based on surface plasmon antennae principles. This polarization-sensitive structure selectively generates and transports polaritons of a desired wavelength through subwavelength apertures. Two of these SPGs have been combined around a nanohole into a new, single device that allows polarization and wavelength selective switching of transmission. The multi-state operation is confirmed by experiment results.

MBE-grown strained-layer superlattices (SLSs) of the types InAs/GaAs and InxGa1−xAs/GaAs on (100) GaAs are analysed by transmission electron microscopy (TEM) and Rutherford backscattering (RBS) and channeling techniques. The structural perfection of the SLSs is demonstrated by TEM studies and by RBS channeling analyses along the [100] growth direction. TEM cross section images of a InAs/GaAs multilayer structure with discretely increased layer thickness of the InAs layers show that the critical layer thickness lies within 0.6 to 1.2 nm for this system. The investigations of InGaAs/GaAs SLSs by TEM show that the strain relaxation leads to the formation of a network of orthogonal 60° misfit dislocations along the 〈110〉 direction. Analyses using both methods indicate that the misfit dislocations are localized at the interface of the SLS or the alloy buffer layer with the GaAs substrate. Angular scans through the off-normal 〈110〉 axis in a SLS and in a GaAs reference crystal are used to measure the tetragonal distortion by ion channeling. The value obtained is in good agreement with that calculated for pseudomorphic structures on the basis of the theory of elasticity. Mit Hilfe der MBE gezuchtete Supergitter mit verspannten Schichten (SLSs) vom Typ InAs/GaAs und InxGa1−xAs/GaAs auf (100) GaAs werden mit den Methoden der Transmissionselektronenmikroskopie (TEM), der Rutherford-Ruckstreu-Spektroskopie (RBS) und der Kanalleitung analysiet. Die strukturelle Perfektion der Supergitter wird mit Hilfe von TEM- und RBS-Kanalleitungsuntersuchungen nachgewiesen. Mit TEM-Querschnittsaufnahmen einer InAs/GaAs-Mehrschichtstruktur, mit diskret zunehmender Schichtdicke der InAs Schichten kann nachgewiesen werden, das die kritische Schichtdicke fur dieses System im Bereich von 0,6 bis 1,2 nm liegt. Die TEM-Untersuchungen an InGaAs/GaAs SLSs zeigen, das die Spannungsrelaxation zur Herausbildung eines orthogonalen Netzwerkes von 60° Anpassungsversetzungen entlang der 〈110〉- Richtung fuhrt. Mit beiden Mesmethoden kann nachgewiesen werden, das die Anpassungsversetzungen an der Grenzflache des SLS beziehungsweise der Legierungspufferschicht mit dem GaAs-Substrat lokalisiert sind. Auf der Grundlage von Winkelverteilungen ruckgestreuter 3 MeV He-Ionen durch die zur 〈100〉-Richtung geneigte 〈110〉-Achse in einem SLS- und einem GaAs-Vergleichskristall wird die tetragonale Gitterverzerrung mit Hilfe der Kanalleitung von Ionen gemessen. Der erhaltene Wert stimmt gut mit dem auf der Basis der Elastizitatstheorie berechneten Wert uberein.

The temperature dependence of the density of InAs islands on GaAs(100) with a minimum at a substrate temperature of around 500°C has been obtained. This dependence can be explained by a transition from complete to incomplete condensation. The migration and desorption energies of indium adatoms were found to be 1.26 eV and 1.40 eV respectively. Electron diffraction on the misfit dislocation network was observed. The conditions for indium segragation during the growth of InxGa1−xAs alloy films were established.

InAs/GaAs strained-layer superlattices (SLS) grown on a GaAs(100) substrate were studied by both Raman spectroscopy (RS) and transmission electron microscopy (TEM). It was shown that the interfaces inside the superlattice are coherent, but the superlattice–substrate interface contain an orthogonal two-dimensional network of 60° misfit dislocations. Using these experimental data values of elastic strain in individual layers and the average values of the residual elastic strain in SLS were determined. The latter are approximately one order of magnitude higher than theoretically predicted data, which suggests that the relaxation of elastic strains was not fully complete. Subsequent annealing of these structures led to the generation of more misfit dislocations, consistent with further relaxation of elastic strain.

Focused Ion Beam (FIB) systems employ a finely focussed beam of positively charged ions to process materials. Ion induced charging effects in non-conductive materials have been confirmed using Scanning Surface Potential Microscopy (SSPM). Significant localized residual charging is observed within the ion implanted micro-volumes of non-conductive materials both prior to and following the onset of sputtering. Characteristic observed surface potentials associated with the resultant charging have been modelled, giving insight into the charging processes during implantation and sputtering. The results of this work have implications for the processing and microanalysis of non-conductive materials in FIB systems.

Nitrogen-vacancy centers in diamond can provide a Lambda-type energy level structure with long-lived ground-state spin coherence. This talk reports progress toward demonstration of EIT in a single center coupled to an optical cavity.