Search

The black sparrowhawk (Accipitermelanoleucus) is a color‐polymorphic sub‐Saharan raptor, with adults occurring in two discrete color morphs: dark and light. It has previously been suggested that plumage coloration is determined by a one‐locus two‐allele system, with the light allele being dominant over the dark allele. Here, we revisit that assumption with an extended dataset of 130 individuals and pedigree information from 75 individuals spanning five generations. We test the observed offspring phenotypic ratio against the expected ratio under the Hardy–Weinberg equilibrium and find significant deviations from the expected values. Contrary to the previous assumption, our data indicate that the dark allele is in fact dominant over the light allele. Similarly, the multigenerational pedigrees obtained are incompatible with a one‐locus two‐allele system, where the light allele is dominant but are consistent with a scenario where the dark allele is dominant instead. However, without knowledge of the underlying molecular basis of plumage polymorphism, uncertainty remains, and the intra‐morph variation observed suggests that modifier genes or environmental factors may also be involved. Our study not only provides a foundation for future research on the adaptive function of color polymorphism in the species but also highlights the need for caution when drawing conclusions about the mode of inheritance in wild animal populations in the absence of genetic data, especially when one color variant is numerically much rarer than the other. [ABSTRACT FROM AUTHOR]

The electronic properties of hydrogen-terminated single-crystalline chemical-vapor deposited diamond in electrolyte solutions between pH 2 and 12 have been characterized by cyclic voltammetry experiments and pH-sensitive measurements using ion-sensitive field-effect transistor structures. The data show the formation of surface conductivity in diamond if immersed into electrolytes. The drain-source conductivity is pH dependent, with about 66 mV/pH. Due to strong Coulomb repulsion between positive ions in the electrolyte (hydronium ions) and the H+-surface termination of diamond, an enlarged tunneling gap is established which prevents electronic interactions between the electrolyte and diamond. This gap is the “virtual gate insulator” of diamond ion-sensitive field-effect transistor structures, with an interface resistance of about 108 Ω. The application of potentials larger than the oxidation threshold of +0.7 V (pH 13) to +1.6 V (pH 1) gives rise to strong leakage currents and to partial surface oxidation. [ABSTRACT FROM AUTHOR]

It is a common observation that diamond surface conductivity rises after exposure to hydrogen plasmas. Hydrogenation treatments are known to induce a p-type conductive layer, which is not present on non-hydrogenated samples. However, the particular mechanisms predominant in the plasma treatment process are still controversial, and several antagonist conditions have been reported to be of importance, such as sample temperature (500 °C to 800 °C), duration (a few seconds to 1 h), and microwave (MW) power density, etc. Further, the post-plasma step is also crucial, especially since the surface conductivity has been reported to be affected by the presence of an adsorbate layer on the diamond surface. By setting up the arrangement to enable the in situ measurement of the surface conductivity after treatment, we have been able to control all parameters that could affect the surface conductivity, in order to determine those of importance. Among the parameters studied, we were able to analyze the influence of the surface temperature, the gas phase exposure (dry air, wet air, neutral gas, CH[sub 4], O[sub 2], and H[sub 2]), the MW plasma conditions (O[sub 2], H[sub 2]) as well as the exposure to UV (Hg and deuterium) and the importance of the sequence and duration of each of these treatments. We found that hydrogenated surfaces are strongly influenced by the combination of wet air exposure and UV light. We noticed that the effect of UV light is persistent and cannot be related to direct photoconduction and has to be attributed to a modification of the trapped defect population. This can, therefore, be compared with the modification of filled defect density as observed in persistent photoconduction. [ABSTRACT FROM AUTHOR]

Polycrystalline silicon layers are prepared by interference laser crystallization (ILC) in the superlateral growth regime. To characterize their microscopic photoelectrical properties, light beam induced current (LBIC) is used, employing a focused laser beam for local generation of photocarriers in the layers with spatial resolution of ≈0.4 µm. The results are correlated with surface morphology obtained by atomic force microscopy. In the single pulse ILC, the temperature profiles are optimized by changing the proportion of interfering beam intensities. The typical grains are of triangular shape, with a length of 1.5 µm and width <0.5 µm. The photocurrent response is dominated by variations in the sample thickness. In the multiple pulse ILC, thin films with grains of quadratic shape and of size exceeding 5 µm are obtained by shifting the sample through an interference pattern, thus taking advantage of lateral epitaxial regrowth. Here, by use of a lock-in, LBIC can detect position and local electronic properties of individual grain boundaries. Grain boundaries are clearly identified by 180° shifts of the photocurrent phase close to maxima of photocurrent amplitude. The photocurrent is attributed to local fields at grain boundaries. These fields extend about 1.4 µm into the grains. The barrier height at the boundary is about 110 mV. [ABSTRACT FROM AUTHOR]

Efficient light trapping structures for amorphous hydrogenated silicon (a-Si:H) solar cells have been realized using periodically structured aluminum doped zinc oxide (ZnO:Al) with periods between 390 and 980 nm as a transparent front contact. Atomic force microscopy, optical reflection, and diffraction efficiency measurements were applied to characterize solar cells deposited on such gratings. A simple formula for the threshold wavelength of total internal reflection is derived. Periodic light coupler gratings reduce the reflectance to a value below 10% in the wavelength range of 400-800 nm which is comparable to cells with an optimized statistical texture. Diffraction efficiency measurements and theoretical considerations indicate that a combination of transmission and reflection gratings contribute to the observed reduction of the reflectance. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Long living excited states in boron doped diamond are detected by photoconductivity and photoconductivity excitation spectroscopy at temperatures T<190 K in the energy regime 3.2-3.5 eV. The photoconductivity spectra show pronounced maxima in highly doped [(4-8)x10[sup 18] cm[sup -3]] diamond which decrease with decreasing doping density. A model is presented where holes are optically excited from compensating deep defects, 3.36 eV above the valence band edge, into the valence band. Here they get captured by LO phonon emission into long living excited levels of boron. The long living excited states are 200, 240, and 266 meV above the 1s ground level. Maxima in photocurrent can be detected at high doping concentrations as the wave function overlap between neighboring excited states is significant to allow hopping transitions between neighboring excited states. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Provides information on a study that investigated the defect distribution in IIb synthetic diamond by deep level transient spectroscopy. Details of the experiments; Results of the study; Conclusion.

Hydrogen terminated intrinsic diamond is characterized using photoelectron emission spectroscopy. Samples have been annealed at temperatures Ta from 200 to 1000 °C. The electron emission characteristics can be divided into three regimes: (I) (Ta<300 °C) is governed by surface band bending which allows only excitons to reach the surface with subsequent dissociation. (II) (300 °C<=Ta<=650 °C) shows increased electron emission and the surface band bending has been removed. Here, excitons and electrons contribute. (III) (Ta>650 °C) additional rise of emission is detected. The spectra are dominated by photon-phonon interactions which are discussed in detail. [ABSTRACT FROM AUTHOR]

Diamond integrated photonic devices are promising candidates for emerging applications in nanophotonics and quantum optics. Here, we demonstrate active modulation of diamond nanophotonic circuits by exploiting mechanical degrees of freedom in free-standing diamond electro-optomechanical resonators. We obtain high quality factors up to 9600, allowing us to read out the driven nanomechanical response with integrated optical interferometers with high sensitivity. We are able to excite higher order mechanical modes up to 115 MHz and observe the nanomechanical response also under ambient conditions. [ABSTRACT FROM AUTHOR]

The surface termination of single crystalline diamond with fluorine and chlorine was investigated. The diamond was exposed to SF6 inductively coupled plasma for fluorination and to Cl2 plasma for chlorination. For the fluorine termination, the plasma treatment caused one monolayer of fluorine (measured with two angle photoelectron detection) and no carbonyl fluorides on the diamond surface. Furthermore no graphitization or roughening of the surface was observed. The plasma treatment with chlorine led to rough surfaces. [ABSTRACT FROM AUTHOR]

Micro electromechanical systems are a matter of intense research pursuing to replace silicon and III–V semiconductor-based components in prospective radio frequency communication devices. Due to their unique material properties, microstructures combining doped nano-crystalline diamond (NCD) and AlN thin films are promising for piezo-actuated microsystems in order to increase operating frequencies. In this work, single and doubly clamped unimorph NCD-on-AlN micro-resonators were fabricated and then characterized by laser vibrometry towards their flexural resonant frequencies in the range of 0.1–20 MHz to deduce their mechanical properties. Enhancements in the structural properties of an AlN piezo-actuator united with an advanced elasticity of nano-diamond electrode lead to superior mechanical parameters of the resulting unimorphs. These allow for the fabrication of flexural resonant microsystems with a potential to extend the operating frequencies well above 1 GHz. [ABSTRACT FROM AUTHOR]

Unimorph heterostructures based on piezoelectric aluminum nitride (AlN) and diamond thin films are highly desirable for applications in micro- and nanoelectromechanical systems. In this paper, we present a new approach to combine thin conductive boron-doped as well as insulating nanocrystalline diamond (NCD) with sputtered AlN films without the need for any buffer layers between AlN and NCD or polishing steps. The zeta potentials of differently treated nanodiamond (ND) particles in aqueous colloids are adjusted to the zeta potential of AlN in water. Thereby, the nucleation density for the initial growth of diamond on AlN can be varied from very low (108 cm-2), in the case of hydrogen-treated ND seeding particles, to very high values of 1011 cm-2 for oxidized ND particles. Our approach yielding high nucleation densities allows the growth of very thin NCD films on AlN with thicknesses as low as 40 nm for applications such as microelectromechanical beam resonators. Fabricated piezo-actuated micro-resonators exhibit enhanced mechanical properties due to the incorporation of boron-doped NCD films. Highly boron-doped NCD thin films which replace the metal top electrode offer Young's moduli of more than 1000 GPa. [ABSTRACT FROM AUTHOR]

The article presents a study which examined the effets of 4-Nonylphenol (4-NP) synthetic organic chemical on the hypo-ormoregulation and hormones in juvenile European seabass, Dicentrarchus labrax. Several variables are considered including the procedure used in 4-NP exposure of the seabass, molecular biology analyses and total RNA extracted from the sample. The levels of growth hormone (GH) and somatolactin (SL) in the sample are described.

Nanopores in insulating solid state membranes have recently attracted much interest in the field of probing, characterizing, and manipulating single linear polymers such as DNA/RNA and proteins in their native environment. Here a low cost, fast, and effective way to produce nanostructures such as pyramidal shaped nanopores and nanochannels with dimensions down to about 15 nm in diamond membranes without any need for electron-beam lithography is demonstrated. By use of a catalytic process, anisotropic etching of diamond with self-organized Ni nanoparticles in hydrogen atmosphere at 900 °C is achieved and possible etching mechanisms are discussed. It is shown that diamond planes with the crystallographic orientation of [111] are etched slowest with this method. [ABSTRACT FROM AUTHOR]

Nanocrystalline diamond (NCD) membranes of 150 nm thickness and diameters in the millimeter range grown by microwave-assisted chemical-vapor deposition were bulged to investigate their mechanical properties and their use as tuneable optical lenses. The NCD films were grown at different CH4/H2 gas mixtures to vary the sp2/sp3 ratio and thereby to tune their mechanical, optical, and surface morphology properties. By applying gas over pressure the membrane forms a lens shaped geometry. From deflection data we calculated Young’s moduli which decrease with increasing CH4/H2 ratio from 1160 GPa at 0.5% to 900 GPa at 7%. Optical lens applications show a variation in the focal point from infinity to 3.5 mm. The data indicate that NCD is a promising material for tuneable optical lenses applications. [ABSTRACT FROM AUTHOR]

An increase in carrier mobility from typical values around 100 to more than 300 cm2/V s at room temperature is detected on hydrogenated undoped <100> diamond layers after annealing at 400 K in a vacuum. As a function of temperature in the range 400 to 125 K the high mobility followed tendencies remarkably close ionized impurity (toward low temperatures) and phonon scattering (toward high temperatures). As a function of annealing time, the high mobility increased with the time constant of about 6.8 h in the range of 1–16 h. A prerequisite for obtaining the largest increase in mobility was optimized surface cleanness. Exposing the samples to air resulted in a complete recovery of the original values of mobility, hole concentration, and conductivity after several days. The data are discussed in terms of interactions between holes in the surface conductive channel and adsorbates on the surface. [ABSTRACT FROM AUTHOR]

Total photoyield experiments are applied to characterize p-, intrinsic, and n-type diamond with hydrogen-terminated surfaces. On all hydrogen-terminated samples a photoelectron threshold energy of 4.4 eV is detected which is discussed in detail in this letter. We attribute this threshold to the energy gap between the valence-band maximum and the vacuum level, which is 1.1 eV below the conduction-band minimum, and generally referred to as ”negative electron affinity” (NEA). Hydrogen terminated p-type and intrinsic diamond show a rise of secondary photoyield in the excitation regime hν>5.47 eV. However, this is not detected on n-type diamond. We ascribe this to the formation of an upward surface band bending in the vicinity of the n-type diamond surface which acts as an energy barrier for electrons. [ABSTRACT FROM AUTHOR]

Two practically fully relaxed AlN domains were identilied by x-ray diffractometry for AlN grown on (100) diamond. The epitaxial orientation relationships (0001)[1010] AlNI¦¦ (100)[011] diamond for the predominant AlN domain (type I) and (0001)[1210] AlNII (100)[011] diamond for the second domain (type II) are obtained. Surface morphology measurements corroborate the good structural quality of the AlN film. In addition, the intrinsic built-in voltage of a n-AlN/p-diamond diode was determined as 1.15 V. By spectrally resolved photocurrent measurements, the ultraviolet electroluminescence emission was conlirmed to originate at the heterojunction interface, and is most probably due to a defect center.

Atomic force microscopy (AFM) is applied to control surface termination of hydrogenated diamond surfaces with lateral resolution of &ap;10 nm. Using negatively biased silicon cantilevers, microscopic patterns can be scribed into a diamond surface, up to a depth of 3 nm. The inscribed patterns exhibit different electronic properties to the rest of the surface, namely electron affinity and conductivity. The effect of contact and noncontact AFM on the pattern appearance is discussed. [ABSTRACT FROM AUTHOR]

Atomic force microscopy and Kelvin probe experiments are applied to characterize hydrogen terminated patterns contacted with gold and aluminum on (100) diamond surfaces. On hydrogen terminated diamond the work function of 4.9 eV is detected, with an accuracy of about 0.1 eV. Taking into account the negative electron affinity of - 1.3 eV and a band gap of 5.5 eV the Fermi energy is 0.7 eV deep in the valence band. Illumination of the sample results in a shift of the surface Fermi level by as much as 0.2 eV. This is attributed to a surface photovoltage effect. [ABSTRACT FROM AUTHOR]

The highly conductive surface layer induced in diamond by hydrogen termination has been used to fabricate in-plane gate transistors. The conductive channel has been separated from the Ohmic gate contacts by insulating thin lines, obtained by using a combination of electron-beam lithography with surface oxidation. Oxidized lines of about 100 nm show excellent blocking properties, with leakage current of 0.3 pA/μm at 100 V and room temperature. In-plane transistor properties are reported for operation at 77 K and room temperature with good saturation characteristic and complete pinch-off. [ABSTRACT FROM AUTHOR]

An aluminum nitride/diamond p-n heterojunction has been realized by plasma-induced molecular-beam epitaxy growth of AlN on (100) diamond. The epitaxial nature of this heterojunction has been confirmed by high-resolution x-ray diffraction. The silicon-doped AlN film (n-type) on the natural boron-doped (p-type) diamond substrate formed a heterobipolar diode with good rectifying properties and surprisingly efficient light emission in the spectral range from 2.7 to 4.8 eV under forward bias. Results concerning the structural, electrical, and optical characterization of the AlN/diamond heterojunction are reported in this letter. [ABSTRACT FROM AUTHOR]

The electrical properties of Al contacts on hydrogen-terminated diamond have been characterized. Capacitance-voltage experiments were carried out in order to obtain further insight into the origin of the Schottky contact behavior of Al. Schottky diodes with different areas and peripheries were fabricated and analyzed. We have found that the capacitance of these structures is not proportional to the area but to the length of the contact periphery, supporting the two-dimensional nature of the surface charge layer in hydrogen-terminated diamond. A model based on the negative electron affinity of hydrogen-terminated diamond and the work function of Al is used to explain the in-plane capacitance of the Al Schottky contacts. [ABSTRACT FROM AUTHOR]

Three hydrogen-terminated diamonds with different surface roughness and morphologies have been investigated by conductivity and Hall experiments in the temperature regime 0.34–350 K. The sheet hole densities are weakly temperature dependent above a critical temperature T[sub c] (20 K≤T[sub c]≤70 K), below T[sub c] carriers freeze out. The mobilities of holes show a minimum at T[sub c] increasing towards higher and even stronger towards lower temperatures significantly up to 400 cm2/V s. A transport model is introduced where holes propagate in the valence band where a disorder-induced tail of localized states is present. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigations of polycrystalline chemical vapor deposited diamond films by electron-spin-resonance (ESR), light-induced (L)ESR, and the constant photoconductivity method have identified dispersed substitutional nitrogen (P1 center) as the main paramagnetic form of N incorporated in the CVD diamond. The density of N-related paramagnetic states is strongly affected by illumination and heat treatment. It is found that the P1 center in CVD diamond gives rise to a deep donor state about 1.5 eV below the conduction band. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate an active control of the charge state of a single nitrogen-vacancy (NV) centre by using in-plane Schottky-diode geometries with aluminium on hydrogen-terminated diamond surface. A switching between NV+, NV0 and NV− can be performed with the Al-gates which apply electric fields in the hole depletion region of the Schottky junction that induces a band bending modulation, thereby shifting the Fermi-level over NV charge transition levels. We simulated the in-plane band structure of the Schottky junction with the Software ATLAS by solving the drift-diffusion model and the Poisson-equation self-consistently. We simulated the IV-characteristics, calculated the width of the hole depletion region, the position of the Fermi-level intersection with the NV charge transition levels for different reverse bias voltages applied on the Al-gate. We can show that the field-induced band bending modulation in the depletion region causes a shifting of the Fermi-level over NV charge transition levels in such a way that the charge state of a single NV centre and thus its electrical and optical properties is tuned. In addition, the NV centre should be approx. 1-2 μm away from the Al-edge in order to be switched with moderate bias voltages. [ABSTRACT FROM AUTHOR]