Pillar Growth Research Articles

Smooth and Narrow Nanopillars Fabricated by Ion-Beam-Induced Deposition under Charging Conditions

We investigate the formation of the irregular sidewall and halo of pillars grown by ion-beam-induced deposition (IBID) by growing platinum nanopillars on an insulating Si3N4 membrane and on a semiconducting Si wafer with a thin Si3N4 top layer. As compared with the pillars grown in a conductive environment, the pillars grown on an insulating membrane are smoother, higher and thinner but have the same volume. Furthermore, they are accompanied by smaller halos. These differences suggest a distinct charging effect in IBID pillar growth. This charging effect is attributed to the secondary electron emission and possibly the aggregation of precursor gas molecules.

Gallium nitride heterostructures on 3D structured silicon

We investigated GaN-based heterostructures grown on three-dimensionally patternedSi(111) substrates by metal organic vapour phase epitaxy, with the goal of fabricating wellcontrolled high quality, defect reduced GaN-based nanoLEDs. The high aspect ratios ofsuch pillars minimize the influence of the lattice mismatched substrate and improve thematerial quality. In contrast to other approaches, we employed deep etched siliconsubstrates to achieve a controlled pillar growth. For that a special low temperatureinductively coupled plasma etching process has been developed. InGaN/GaNmulti-quantum-well structures have been incorporated into the pillars. We found apronounced dependence of the morphology of the GaN structures on the size and pitch ofthe pillars. Spatially resolved optical properties of the structures are analysed bycathodoluminescence.

Pericytes in the mature chorioallantoic membrane capillary plexus contain desmin and α-smooth muscle actin: relevance for non-sprouting angiogenesis

The chicken chorioallantoic membrane (CAM) is a frequently used tissue for studying vascular growth and remodeling, notably non-sprouting angiogenesis by formation of transluminal pillars. Vascular pericytes have received increasing attention in the field of angiogenesis research and appear important for pillar growth. Our earlier observation that desmin (DES), but not alpha-smooth muscle actin (alphaSMA) was expressed in pericytes of the mature CAM capillary plexus after E12 was confirmed by others. However, in different species or vascular beds, either marker or both have been used to identify pericytes, raising the questions if (1) expression of these cytoskeletal proteins really was mutually exclusive; or (2) different types of pericytes existed in the same vascular bed. Using triple labeling with fluorochrome-conjugated markers Sambucus nigra agglutinin, DES or alphaSMA, and DNA-specific YoPro-1, we report here for the first time a delicate filamentous, circumferentially oriented alphaSMA pattern in periendothelial cells of the mature CAM capillary plexus, quite different from the coarser, axially oriented DES pattern. A new method for automatic classification of DNA-staining pattern was applied to compare nuclei of DES- or alphaSMA-positive cells. It predicted colocalisation of both proteins in most capillary pericytes, which was confirmed by double immunostaining for DES and alphaSMA. We conclude that (1) in contrast to published work, DES and alphaSMA are not mutually exclusive in most pericytes; (2) different types of pericytes may co-exist in the same vascular bed; (3) on average, one pericyte is associated with two transluminal pillars; (4) a novel imaging modality may be useful for cell identification in angiogenesis research and elsewhere.

A nanoscale three-dimensional Monte Carlo simulation of electron-beam-induced depositionwith gas dynamics

A computer simulation was developed to simulate electron-beam-induced deposition (EBID).Simulated growth produced high-aspect-ratio, nanoscale pillar structures by simulating astationary Gaussian electron beam. The simulator stores in memory the spatial and temporalcoordinates of deposited atoms in addition to the type of electron, either primary (PE),back-scattered (BSE), or secondary (SE), that induced its deposition. The results providedin this paper apply to tungsten pillar growth by EBID on a tungsten substrate fromWF6 precursor, although the simulation may be applied to any substrate–precursor set. Thedetails of the simulation are described including the Monte Carlo electron–solid interactionsimulation used to generate scattered electron trajectories and SE generation,the probability of molecular dissociation of the precursor gas when an electrontraverses the surface, and the gas dynamics which control the surface coverage of theWF6 precursor on the substrate and pillar surface. In this paper, three specific studies arecompared: the effects of beam energy, mass transport versus reaction-rate-limited growth,and the effects of surface diffusion on the EBID process.

Growth and simulation of high-aspect ratio nanopillars by primary and secondary electron-induced deposition

While several studies have suggested that secondary electrons dominate electron beam induced deposition (EBID), we demonstrate that primary electrons (PE’s) contribute significantly to the deposition for nanoscale EBID over the electron beam energy range (500–20keV). High-aspect ratio pillar growth is a signature of EBID; W nanopillar growth on SiO2 substrate yielded a growth rate of 6nms−1 and a nanopillar aspect ratio of ∼50. A simple integration of the primary, secondary, and backscattered electron distributions versus a dissociation cross section for WF6 suggests that all three electron species should contribute to the total volume of the deposited nanopillar, contrary to reports that suggest that secondary electrons dominate the process. A three-dimensional, Monte Carlo simulation including time correlated gas dynamics and species specific deposition was developed to help elucidate which of the relevant electron species, primary (PE’s), secondary (SE’s), and/or backscattered electrons (BSE’s), induce the dissociation of precursor gas and lead to nanopillar growth. PE’s and secondary electrons produced from the incident beam (SEI’s) were found to induce the vertical nanopillar growth component relative to secondary electrons induced from backscattered electrons (SEII’s) and BSE’s.

Genetic Interactions of Pillar and Weeping Peach Genotypes

Genetic interaction of the pillar (PI) and weeping (WE) growth habit genotypes was investigated in peach [Prunus persica (L.) Batsch]. Data from F2, BC1P1, and BC1P2 families showed that PI (brbr) was epistatic to the expression of WE (plpl). A unique growth habit not previously described in peach, and referred to as arching (AR), was recovered in the F2 family. Arching trees showed an upright phenotype similar to Brbr heterozygotes, but had a distinct curvature in the developing shoots. Progeny testing of AR trees revealed their genotype is Brbrplpl.

Genetic Interactions of Pillar (Columnar), Compact, and Dwarf Peach Tree Genotypes

A study was conducted to determine genetic control of the columnar or pillar (PI) growth habit, and to evaluate the effects of interactions of various genes that influence peach [Prunus persica (L.) Batsch (Peach Group)] growth habit. The PI habit (brbr) examined in this study was inherited as a monogenic trait expressing incomplete dominance. The heterozygous Brbr derived from crosses between standard (ST) and PI genotypes was recognized as an upright (UP) tree with narrower branch angles than ST trees but wider than PI trees. The combination of brbr and brachytic dwarf (DW) (dwdw) produced dwarf-pillar (DWPI) trees. The effects of the heterozygous Brbr in combination with dw and/or compact (CT) (Ct) could not be recognized by visual observation. Compact pillar (CTPI) trees resulted from the expression of Ct_ brbr. These trees were distinguished from globe-shaped (GL) trees (Ct_Brbr) by the more upright growth habit of the CTPI trees. This genetic study highlights the genetic plasticity of tree growth habit in peach. The investigation of novel growth habits extends our concept of the peach tree. Some growth habits such as PI may have commercial potential for high-density peach production systems. Others, such as DWPI and CTPI may have potential as ornamentals.

Growth of self-organized nanosized Co pillars in Au(111) using an alternating deposition process

Nanosized Co pillars were grown in Au(111) using a novel deposition process. Starting from a self-organized array of Co dots on the Au(111) surface, we alternatively deposit Au (0.9 ML) and Co (0.1 ML). Under appropriate conditions, the newly deposited Co atoms assemble into dots, vertically self-aligned and in direct contact with the Co dots from the previous layers. This way, pillars 8 nm high and with a 2:1 vertical aspect ratio were fabricated. It is argued that the growth process is driven by parameter misfit and surface energy effects, and should thus occur for other pairs of elements than (Co,Au). From the superparamagnetic regime, we deduce that each pillar behaves like a single magnetic entity. The onset of perpendicular remanence occurs around room temperature, instead of 20 K for the initial flat dots. In terms of applications, the main drawbacks of self-assembled and organized nanosized magnetic systems are the small amounts of material contributing to magnetic effects, and the superparamagnetism blocking temperature, generally well below RT. The pillar growth process is a good candidate to solve them simultaneously.

Study of pillar microstructure formation with anodic oxides

In present paper, the fabrication of pillared microstructures by means of multistep anodization of Ta/Al film structure on ceramic and silicon (100) substrates is described. The main characteristics of these structures, obtained by electron microscopy, are presented. Information on geometrical parameters of porous host and pillar microstructure elements has been obtained. The depth:diameter ratio (`aspect ratio') for investigated composition was 1.7–4.0. The transport numbers T Ta 5+=0.4 and T Al 3+=0.25 for the anodizing process of two-layered Ta/Al film structure have been obtained. The features of ion transport in thin film Ta/Al system under anodization are presented, and two versions of the process of pillar growth through porous Al 2O 3 are proposed. The scheme of the additive process for functional layer formation on the base of combined anodic oxides is proposed, which may be used, in particular, for fabrication of light-emitting structures with nanosized elements.

The development of the reticular lamina in the hamster: An examination of transitory features and their functional roles

This study examines the development of the reticular lamina in the Syrian golden hamster postriatally from birth to adulthood at 2 day intervals using the scanning electron microscope. During this period, numerous transitory features emerged whose roles were concerned primarily with the development of the tectorial membrane (TM). The principal findings were as follows. (1) The surface of the developing organ of Corti produced all the fibrous material composing the minor tectorial membrane (mTM) including radial and longitudinal fiber bundles which formed the skeleton of the TM, and spongy, amorphous material which formed its intervening ground substance. (2) Throughout most of the cochlear spiral, radial fiber bundles were seen extending from the microvilli of supporting cells and projecting toward the major tectorial membrane (MTM). In most of the basal turn, but not in the apical turn, these radial bundles were interwoven with longitudinal fiber bundles which emerged from the surface of Hensen's cells. These findings indicate that the architecture of the TM is more complex in the basal turn than in the apex. (3) Increases in the dimensions of the reticular lamina resulted from the emergence of pillar cell headplates and growth in the diameter of hair cells and supporting cells. The emergence of pillar cell headplates was the principal factor contributing to increases in the radial dimension of the reticular lamina. This emergence was most dramatic between 10 and 12 days after birth (DAB) after the mTM completed its growth. Since the mTM appears to be bound medially to the MTM and laterally to the marginal pillars by 10 DAB, it seems likely that the growth of the reticular lamina after 10 DAB causes some stretching of the mTM both radially and longitudinally. (4) Completion of outer hair cell stereocilia growth at 8 DAB was followed by loss of supporting cell attachments of the TM (trabeculae) by 10 DAB, and coincided with the formation of marginal pillars from the third row of supporting cells. It is suggested that the formation of marginal pillars may be required for coupling of the TM to the tips of outer hair cell stereocilia and for induction of radial tension of the mTM. (5) Removal of the marginal pillar attachments occurred following completion of hair cell growth. (6) All structures on the reticular lamina appeared to have adult-like characteristics by 20 DAB.

Pillar crystal growth of boron phosphide from the vapour in the presence of nickel impurity

Pillar crystals of boron monophosphide were grown from an atmosphere of BC1 3-PC1 3-H 2-Ar on an inner surface of a quartz tube in the temperature range of 1060–1090°C. Fine particles of nickel dispersed on the substrate induced pillar growth. The maximum length of the crystals was limited by the radius of the substrate tube. The cross section of the pillar crystals varied with growth time from circle to polygonal (tri-, hexa-, octa-, and nonagonal). The growth axis was considered to be the 〈111〉 direction, and the side faces to be {110}; and {211} forms. The growth mechanism was supposed to be initial VLS growth along the axis, followed by thickening.