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The adsorption of the C60 fullerene molecule has been studied in various configurations on a reconstructed Si(100) silicon surface. Among fullerenes, fullerene C60 is of particular importance, since it has the most stable form and consists of 60 carbon atoms. Monocrystalline silicon has the diamond structure, the size of its crystal lattice is 5.43 Å. The MD-simulation calculations have been performed using the open source LAMMPS MD-simulator software package and the Nanotube Modeler computer program. The Tersoff interatomic potential has been used to determine the interactions between the Si-Si, C-C and Si-C atoms. The adsorption energy of the C60 molecule on the reconstructed Si(100) surface, the bond lengths and the number of bonds formed depend on the adsorption geometry, i.e. at what point on the substrate the molecule is adsorbed and in what configuration. [ABSTRACT FROM AUTHOR]

This paper provides a detailed description explaining how to calculate the relation between the silicon Raman frequency and local stress or strain in the silicon, applied to stress measurements in microelectronics. This relation is well known for measurements from the (100) surface of silicon. However, it is often used in the wrong way, neglecting non-zero stress tensor elements. Especially, in current 3D microelectronics technology, where the stress caused by through Si vias or microbumps is of large importance, the vertical stress component, which highly affects the measured Raman frequency shift, is often erroneously neglected. In addition, the equations for the (100) surface are also often used incorrectly for cross-sectional measurements from a (110) surface. In this paper, different ways to calculate the relation between Raman frequency and triaxial stress, and the related Raman peak intensities, are discussed in detail. [ABSTRACT FROM AUTHOR]

Surface stress has been shown to affect the mechanical properties of materials at or below the microscale. Surface-stress-induced dislocation activity at such length scales has been shown to be a major factor affecting the mechanical behavior of materials. Defect generation as a function of applied stress at the microscale has previously been measured experimentally and predicted using simulations. However, the change in surface stress in a material in response to externally applied stress as a function of temperature has not been explored experimentally. Such an investigation is presented in this work for the case of microscale silicon samples. In-situ nondestructive measurements of the applied compressive stress and the corresponding microscale surface stress were performed from room temperature to 100 °C. The applied stress was controlled by a nanomechanical loading system. Micro-Raman spectroscopy was used to measure the surface stress in-situ as the samples deformed under the applied uniaxial compressive stress. The surface stress was found to be lower than the applied stress at all temperatures. The difference between the surface stress and the applied stress became higher at higher temperatures indicating that surface relaxation was induced by the temperature increase. Based on the measured values and observed trends, an exponential Gaussian function is proposed to describe the stress as a function of surface [ABSTRACT FROM AUTHOR]

The molecular-level chemistry involved in the processing of silicon and zirconia substrates by inductively coupled fluorocarbon (FC) plasmas produced from CF4 and C2F6 precursors has been explored. The roles of gas-phase excited, neutral, and ionic species, especially CF2 and F, were examined as they contribute to FC film formation and substrate etching. The surface reactivity of CF2 radicals in C2F6 plasmas has a dependence on substrate material and plasma system, as measured by our imaging of radicals interacting with surfaces (IRIS) technique. Relative concentrations of excited state species are also dependent upon substrate type. Moreover, differences in the nature and concentrations of gas-phase species in CF4 and C2F6 plasmas contribute to markedly different surface compositions for FC films deposited on substrates as revealed from x-ray photoelectron spectroscopic analysis. These data have led to the development of a scheme that illustrates the mechanisms of film formation and destruction in these FC/substrate systems with respect to CF2 and F gas-phase species and also Si and ZrO2 substrates. [ABSTRACT FROM AUTHOR]

We measured local stress distributions in a cleaved Si shallow trench isolation (STI) structure. We used a high-spatial-resolution confocal UV micro-Raman system with an excitation wavelength of 364 nm. The polarization dependence of Raman spectra enabled us to quantitatively estimate the stress direction and intensity on the [formula] cross-section. We observed stress relaxation due to the cleavage resulted in an abrupt change in the intensity and polarity of stress around the cross-sectional surface. Finite element method simulations reproduced well the measurement results and confirmed that this change was due to out-of-plane elastic deformation of the cleaved surface. This accurate comparison of the measurement data and the simulation is based on the feature that the UV Raman measurement selectively detects the surface regions, making this method particularly useful in stress distribution analyses. [ABSTRACT FROM AUTHOR]

The surfaces of solar cells are often textured to increase their capacity to absorb light. This optical benefit is partially offset, however, by an increase in carrier recombination at or near the textured surface. A review of past work shows that the additional recombination invoked by a textured surface varies greatly from one experiment to another. For example, in the most commonly investigated structure—pyramidal textured silicon diffused with phosphorus and passivated with a hydrogenated oxide—recombination ranges from being 1–12 times more than in an equivalently prepared planar {100} surface. Examination of these experiments reveals consistent trends: small increases in recombination occur when the surface is very heavily diffused and dominated by Auger recombination, while larger increases in recombination occur when the surface is lightly diffused and dominated by Shockley–Read–Hall recombination at the surface, making the latter depend critically on surface area and the density of surface states. Comparisons of pyramidal and planar {100} surfaces indicate that when lightly diffused, the difference in recombination is substantially greater than the difference in surface area (1.73) and it is regularly attributed to the pyramid facets having {111} orientations—well known for their higher density of dangling bonds than {100} orientations. This high dangling-bond density makes recombination at pyramidal facets strongly dependent on the passivation scheme, and it is variations in these schemes that led to the wide range of results observed in experimental studies. In addition to surface area and crystal orientation, some experiments suggest a third mechanism that enhances recombination on oxide-passivated pyramids. With capacitance-voltage and photoconductance measurements, we confirm this speculation, showing that oxide-passivated pyramidal textured silicon has a higher density of interface states than can be accounted for by surface area and orientation, and that the additional defects are predominantly acceptorlike when above, or donorlike when below, an energy of 0.3 eV higher than the valence band. [ABSTRACT FROM AUTHOR]

We use the laser-induced transient grating technique for the excitation and detection of surface vibrational modes of a periodic microstructure on a silicon substrate forming a one-dimensional phononic crystal. Two standing wave eigenmodes with zero-group velocity corresponding to the top and bottom of the bandgap in the dispersion of the zone-folded Rayleigh waves are produced by setting the spatial period of the excitation pattern to twice the structure period. These modes do not radiate acoustic energy into the substrate, yielding an enhanced lifetime. We show that the relative amplitude of the two modes is controlled by the spatial phase of the excitation pattern, and discuss the dependence of the confinement time of the acoustic oscillations within the excitation area on the curvature of the dispersion surface. [ABSTRACT FROM AUTHOR]

The diffusion process of fluorine (F) atoms on the Si(111)-(7×7) surface is investigated using high-temperature scanning tunneling microscopy. The kinetic parameters of F hopping agree well with those of the diffusing silicon (Si) atoms, which implies that of all reaction processes, the Si diffusion serves as the rate-determining one. Deposition of Si on the surface is found to enhance F hopping, which supports the above-mentioned observation. Theory reveals that the replacement of F adsorption sites by diffusing Si atoms is the key process in the diffusion mechanism. [ABSTRACT FROM AUTHOR]

This study examined the chemical interactions between an atomic-layer-deposited (ALD) HfO2 film and strained epitaxial Si1-xGex/Si (x=0.1,0.2,0.3) substrates during film deposition and postdeposition annealing (PDA), as well as their influence on the electrical properties. The influences of various predeposition surface treatments under O3 (POT) and NH3 (PNT) were also investigated in order to improve the understanding of the chemical and structural changes in thin film systems. Particular focus was made on the migration behavior of Si and Ge in the interface between a HfO2 film and Si1-xGex substrate, which critically affects the capacitance equivalent thickness (CET). The interdiffusion of the substrate elements during ALD and PDA could be controlled by POT and PNT. PNT was effective in reducing the diffusion of both Si and Ge during the ALD and PDA, whereas POT reduced only Si diffusion. The surface treatments reduced the changes in the CET after PDA without any significant increase in the leakage current density. The migration of the substrate elements was traced by secondary ion mass spectroscopy, auger electron spectroscopy, high-resolution transmission microscopy and x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Based on lattice dynamics theory and molecular dynamics simulations, we have investigated the geometrical structures, phonon dispersion relations, and specific heat of silicon nanowires with Stillinger-Weber potential. It was shown that the original Stillinger-Weber potential can reproduce the well-established four acoustical branches. With the calculated spectra, we calculated specific heats of silicon nanowires. It is found that the specific heats of thin nanowires are much higher than those of bulk silicon. According to the partial density of states of surface atoms, the enhancement of specific heats of silicon nanowires can be attributed to the surface effect and phonon confinement effect. [ABSTRACT FROM AUTHOR]

Phase-separated Al–Si films composed of Al nanocylinders embedded in an amorphous-Si matrix have been prepared by a sputtering method. By controlling the deposition rate, substrate temperature, and film composition, the average diameter of the Al cylinders can be varied systematically from less than 5 to 13 nm with a cylinder density ranging from 1015 to in excess of 1016 cylinders m-2. A three-dimensional simulation of phase separation in binary thin films was performed using a modified Cahn-Hilliard [J. Chem. Phys. 28, 258 (1958)] equation to understand the growth mechanism. The simulation studies indicate that the surface diffusion length and film composition are important factors which determine film morphology. Experimental and simulation studies are compared and discussed. [ABSTRACT FROM AUTHOR]

We have studied the electronic properties, in relation to structural properties, of monolayers of 1-octadecene attached on a hydrogen-terminated (111) silicon surface. The molecules are attached using the free-radical reaction between C==C and Si[Single_Bond]H activated by an ultraviolet illumination. We have compared the structural and electrical properties of monolayers formed on silicon substrates of different types (n type and p type) and different doping concentrations, from low-doped (∼1014 cm-3) to highly doped (∼1019 cm-3). We show that the monolayers on n-, p-, and p+-silicon are densely packed and that they act as very good insulating films at a nanometer thickness with leakage currents as low as ∼10-7 A cm-2 and high-quality capacitance-voltage characteristics. The monolayers formed on n+-type silicon are more disordered and therefore exhibit larger leakage current densities (>10-4 A cm-2) when embedded in a silicon/monolayer/metal junction. The inferior structural and electronic properties obtained with n+-type silicon pinpoint the important role of surface potential and of the position of the surface Fermi level during the chemisorption of the organic monolayers. [ABSTRACT FROM AUTHOR]

Using plane wave pseudopotential density functional theory calculations we have identified for the first time precursor states for hydrogen atom chemisorption on the Si(100)-(2 × 1) surface. These states exist above clean, partially, and fully monohydride-adsorbed surface dimers. In all three cases the dimer bond is broken in the trapped state. A study of the energetics for atomic desorption, abstraction, chemisorption, and migration was carried out. We find that "hot" hydrogen atoms of energies up to approximately 1.3-1.9 eV can be trapped on the surface. These atoms are highly mobile, and we obtained energetics consistent with experimental data from which precursor-mediated adsorption mechanisms have been inferred. The existence of these states provides an understanding of the non-Langmuirian atomic hydrogen adsorption probability, and also underscores the importance of lattice distortions in the interactions of hydrogen with the silicon surface. [ABSTRACT FROM AUTHOR]

It has been found that effective removal of small particles from silicon wafer surfaces can be achieved by laser-induced airborne plasma shock waves initiated above the surface. This process has demonstrated successfully the removal of 1 μm sized tungsten particles from the surface. Tungsten is known to be one of the most difficult particles to remove using conventional laser cleaning techniques employing direct laser irradiation onto the surface. The area cleaned by the shock waves was over ten times larger than that achieved by conventional laser cleaning. This provides an advantage in speed for cleaning large areas. The cleaning efficiency was strongly dependent on the gap distance between the laser focus (where laser-induced sparking takes place) and the surface. The particle removal began to occur with a gap of 6 mm and the removal efficiency increased significantly with decreasing the gap resulting in a complete removal at 2 mm. The basic idea behind this new c! leaning technique and how to apply it for the removal of small particles from surfaces are described. Theoretical considerations about adhesion forces of small particles on the surface and laser-induced shock wave generation are carried out to understand this process. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates the growth of amorphous, microcrystalline and polymorphous silicon by studying the species contributing to the growth and resulting film structure. Surface reaction probability of the radicals and contribution of ions to the growth; Enhancement of chemical vapor deposition by deposition of amorphous silicon by plasma.

Presents in situ x-ray diffraction studies of the evolution of the morphology of vicinal GaAs surfaces during and following undoped and silicon-doped growth using organometallic vapor-phase epitaxy. Undoped GaAs growth; Silicon-doped GaAs growth.

Presents information on a study which investigated the phase transition thresholds in silicon surfaces using laser-induced transient grating technique. Criteria for determining the threshold fluence for the onset of ablation; Experimental details; Results and discussion; Conclusions.

Presents information on a study which reported a decrease in the amplitude of Fowler-Nordheim current oscillations for metal-oxide semiconductor devices made using silicon surfaces that have high spatial complexity roughness. Application of atomic force microscopy for interface roughness of metal-oxide semiconductor capacitor structures; Results and discussion; Conclusions.

Presents a photoemission spectroscopy study of arsenic-rich n-gallium arsenide surface modified by the deposition of an undoped silicon overlayer. Experimental details; Results and discussion; Conclusions.

Presents information on a study which investigated the direct growth of indium-antimony (InSb) on a silicon(111) surface and in silicon (111)-In(4x1) surface phases. Experimental details; Results and discussion; Conclusions.

Presents information on a study which examined a series of reconstructed high-index silicon surfaces using ultrahigh vacuum scanning tunneling microscopy. Experimental procedure; Results and discussion; Conclusions.

As density is one of the basic physical properties of materials, an accurate density standard is absolutely essential. To determine density with high accuracy and precision, two 1‐kg single‐crystal silicon spheres (NMIJ‐S4 and NMIJ‐S5) are used as the primary standard at the National Metrology Institute of Japan. For the accurate measurement of the mass and volume of the silicon spheres, the effects of the surface layer must be carefully considered. In this work, a surface layer model of NMIJ‐S4 and NMIJ‐S5 was proposed and the thicknesses of each surface layer were determined using X‐ray photoelectron spectroscopy. A detailed uncertainty budget is presented to aid use of the density standard. [ABSTRACT FROM AUTHOR]

Frequency reconfigurable antenna is one of the important elements needed for cognitive radio application. Such antenna can be designed using highly resistive (HR) silicon (Si) operating as an optical switch. This letter presents a novel frequency reconfigurable planar monopole antenna suitable for cognitive radio application. The antenna is designed using HR Si working as an optical switch. The main idea behind the design of antenna is the redistribution of surface current on the antenna while changing the state of Si switches optically from high resistance to low resistance. The antenna is highly compact and uses only two switches for multiband reconfiguration. It is switchable on 1.9 GHz, 2.75 GHz, 3.7 GHz, 4.1 GHz, 4.6 GHz, 4.8 GHz, and 7.6 to 11 GHz frequency bands. Simulated and measured results are presented for the antenna. To the best of authors knowledge, this is the first multiband optically reconfigurable planar monopole antenna. [ABSTRACT FROM AUTHOR]

Abstract We present characterization results of two silicon photomultipliers; the Hamamatsu LVR-6050-CN and the Ketek PM3325 WB. With our measurements of the bias dependence of the breakdown probability we are able to draw conclusions about the location and spatial extension of the avalanche region. For the KETEK SiPM we find that the avalanche region is located close to the surface. In the Hamamatsu SiPM the high-field region is located 0. 5 μ m below the surface, while the volume above is depleted almost until the surface. Furthermore, for the Hamamatsu SiPM we find that charge carriers produced by optical-crosstalk photons enter a cell below the avalanche region as opposed to an earlier device where most of the photoelectrons enter a cell from above. The present paper is an attempt to spur further interest in the use of the bias dependence of the breakdown probability and establish it as a standard tool not only to determine the location of the high-field region but also to determine the origin of charge carriers relative to the high-field region. With the knowledge of where the charges come from it should be possible to further improve the optical crosstalk, dark count, and afterpulsing characteristics of SiPM. [ABSTRACT FROM AUTHOR]

Examines the in-diffusion of indium (In) and the surface defects introduced into silicon (Si) for various In desorption process. Reason that a lower substrate temperature and reduced in-diffusion are expected when using In; Ways in which Si surfaces were prepared; Surface morphology.

The interactions of H atoms having hyperthermal energies with a monodeuteride-terminated Si(100) surface are investigated. H atoms having mean kinetic energies of 1.0 and 2.9 eV are generated by 248 and 193 nm laser photolysis, respectively, of a pulsed, free-jet expansion of HI. Full characterization of the laser photolysis conditions allows the determination of the relative, as well as absolute, H atom exposures for these two kinetic energies. The depletion probability of adsorbed D per incident H atom is identical for species having incident kinetic energies of 1.0 and 2.9 eV and has an absolute value of 0.3±0.2. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the voltage, time, and current dependences of nanoneedle growth on silicon surface using scanning tunneling microscope tip. Background of the study; Methodology of the study; Results and discussion.

Focuses on a study which examined the minority-carrier surface recombination velocity of highly doped n-type silicon. Importance of surface recombination velocity in some silicon bipolar devices; Methodology of the study; Results and discussion.

Presents a study which investigated the chemical nature of silicon(100) and (111) surfaces during immersion in dilute hydrofluoric acid solution. Review of related literature; Methodology; Results.

Proposes a model of the basic processes accompanying solid-phase reactions on the silicon surface based on general physical considerations. Model presentations; Discussion on the kinetic aspects; Consequences of model presentations and comparison with experiment.

Investigates Schottky barriers on patterned silicon surfaces. Derivation of the patterning of the silicon surfaces; Effect of patterning on the light collection efficiency of solar cells; Factors which determine the efficiency of patterned solar cells; Use of an ultraviolet excimer laser to ablate patterns on silicon surfaces.

Focuses on a study which measured the surface reaction probability of hydrogenated amorphous silicon growth flux using a macroscopic trench substrate. Measurement of surface reaction probability; Correlation between the surface reaction probability and the film electronic quality; Role of energetic particle bombardment in reactive magnetron sputter.

Focuses on a study which performed in situ observations of arsenic atoms at step sites of vicinal silicon surfaces by coaxial impact-collision ion scattering spectroscopy (CAICISS). Details of CAICISS measurements; Methodology of the study; Results and discussion.

Presents a study which performed surface recombination velocity measurements at the silicon-silicon dioxide interface in semiconductors by microwave-detected photoconductance decay. Theory of excess minority carrier decay; Methodology; Results and discussion.

Presents a study which examined the behavior of nickel impurities at the silicon-silicon dioxide interface of metal-oxide-semiconductors (MOS) using electrical measurements and transmission electron microscopy. Explanation for the increase in the leakage current with the silicon-silicon dioxide interface roughness; Relationship between the degradation of MOS characteristics and nickel impurities near the interface and the interface roughness.

Presents a study that reported the chemical modification of n- and p-type hydrogen-passivated silicon surfaces by a scanning tunneling microscope. Pattern transfer for the defined regions; Scanning tunneling microscope (STM) image of a pattern written on a p-type silicon substrate; Evidence which suggests that the STM patterning is at least partially a topographic change.

Surface morphological and compositional evolution during the initial stages of Si growth on Ge(001)2×1 by cyclic gas-source molecular beam epitaxy from Si2H6 has been investigated using in situ reflection high-energy electron diffraction (RHEED), Auger electron spectroscopy, electron-energy-loss spectroscopy, and scanning tunneling microscopy, combined with post-deposition high-resolution cross-sectional transmission electron microscopy. The layers were deposited using repetitive cycles consisting of saturation Si2H6 dosing at room temperature, followed by annealing for 1 min at 550 °C. Film growth was observed to proceed via a mixed Stranski–Krastanov mode. Single-step-height two-dimensional growth was obtained for nominal Si deposition thicknesses tSi up to [bar_over_tilde:_approx._equal_to]1.5 monolayers (ML). However, the upper layer remained essentially pure Ge which segregated to the surface through site exchange with deposited Si as H was desorbed. At higher tSi, the Ge coverage decreased slowly, the surface roughened, and two-dimensional multilayer island growth was observed for tSi up to [bar_over_tilde:_approx._equal_to]7.5 ML, where bulk reflections in RHEED patterns provided evidence for the evolution of three-dimensional island formula. [ABSTRACT FROM AUTHOR]

Fe/C multilayers have been deposited by rf sputtering on two silicon substrates with a significant difference in surface quality. Scanning tunneling microscopy (STM) shows a roughness replication process: the smoother the substrate, the smoother the final surface. Both samples present a Gaussian height distribution. The fractal analysis of the STM data shows that, for dimensions larger than the grain size, the surface can be described as a self-affine fractal with a fractal dimension of 2.6±0.1, which agrees with the prediction of ballistic deposition models without restructuring. For dimensions lower than the grain size, the fractal dimension is close to the Euclidean value 2. [ABSTRACT FROM AUTHOR]

A study was made of the energies for ejection of Si atoms and SiCl molecules from defect sites on Si (100) and (110) surfaces, including adatoms, kinks, and vacancies, with and without interaction with Cl adsorbates. It is found that the energies for emitting a Si atom from defect sites are smaller than those for the perfect site and almost proportional to the coordination number for the Si (110) surface. It is also found that the interaction of Cl with defects reduces the energy for the ejection of a Si atom and a SiCl molecule, depending on the adsorption site. [ABSTRACT FROM AUTHOR]

Presents a study which examined the morphology of hydrofluoric acid (HF) and ammonium fluoride-treated silicon surfaces with surface infrared spectroscopy. Effect of the variation of HF concentration on the morphology; Experimental methods; Results and discussion.

Presents a study which investigated surface hydrogen coverage and surface reconstruction of a silane-saturated Si(001)2X1 surface. Processes in silicon epitaxy; Details of experimental techniques used; Comparison of hydrogen coverage between two hydrogenated surfaces.

Light-induced metastable degradation of hydrogenated amorphous silicon and silicon germanium thin films (a-SiGe:H) is conjectured to be accompanied by structural changes but there has not been a direct measurement of the same. We measure the surface topography of these films in the annealed and the light soaked state using atomic force microscopy. We quantified the surface topography in terms of surface roughness and find that the surface roughness increases after light soaking. Our results provide direct evidence of the light-induced structural changes in these films. [ABSTRACT FROM AUTHOR]

In this study the effects of nano/microstructuring and surface chemistry on wettability, evaporation rate and the Leidenfrost temperature are experimentally investigated. The functional surfaces with two alternative patterns were originally fabricated via direct femtosecond laser surface processing of polished silicon wafer in air at a fluence slightly above ablation threshold. The droplet lifetime method was used to measure the evaporation rate of a water droplet (4.5 μL) at surface temperatures of 25-350°C and to determine the Leidenfrost temperature. Generally, after processing the functional surfaces with hierarchical surface morphology demonstrate enhanced wetting behavior, evaporation rate enhancement and positive shifts in the Leidenfrost temperature. The functional surfaces with a microgrooved surface pattern, extensively covered by flake-like nanostructures, exhibit strong superhydrophilicity, resulted in a significant temperature-dependent enhancement of evaporation rate (up to 6 times) and an increase of about 30°C in the Leidenfrost temperature relative to the polished surface. The functional surfaces with a microcratered surface pattern being only hydrophilic demonstrate a nearly twofold temperature-independent enhancement of evaporation rate. Thermostability tests showed the heating of the functional surfaces above 340°C to be resulted in a drastically deteriorated wettability and a reduction of evaporative heat transfer performance under repeated experiments. [ABSTRACT FROM AUTHOR]

A thermodynamic model of hydrogen-induced silicon surface layer splitting with the help of a bonded silicon wafer is proposed in this article. Wafer splitting is the result of lateral growth of hydrogen blisters in the entire hydrogen-implanted region during annealing. The blister growth rate depends on the effective activation energies of both hydrogen complex dissociation and hydrogen diffusion. The hydrogen blister radius was studied as a function of annealing time, annealing temperature, and implantation dose. The critical radius was obtained according to the Griffith energy condition. The time required for wafer splitting at the cut temperature was calculated in accordance with the growth of hydrogen blisters. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Test structures were developed to visualize the progress of the dry release of an MEMS device fabricated by deep reactive ion etching (DRIE). Because of the high aspect ratio of DRIE MEMS devices, the undercut progress cannot be observed from the surface. Therefore, a destructive test, i.e., a cross-sectional-view observation of a cleaved sample, has mostly been employed. Using the proposed test structure, the progress of the silicon undercutting can be evaluated in a nondestructive manner, using only an optical microscope. The test structure was not only found to be useful in optimizing the release etching procedure, but also allows us to discover a particular DRIE mode that is useful for dry release. Indeed, most DRIE process engineers have considered and mainly tuned the etching phase; using the test structures, we found that the deposition phase of DRIE can be strategically used to further increase the undercutting speed. The new mode, referred to as the “undercut directional etching mode,” intentionally leaves a fluorocarbon layer for protection of the side-wall, at the bottom center of the trench openings. Because of the deposition layer remaining at the bottom center, the introduced plasma species are concentrated towards the edge of the trench, i.e., at the foot of silicon structure to be released, thereby enhancing the undercut etching. A second test structure identified the appearance of the new mode and visualized the dependence of the etching behavior on the trench opening width. The optimized etching conditions determined using the test structures led to the successful release of a standard in-plane MEMS device. [ABSTRACT FROM PUBLISHER]

The voltage stability, charge-collection properties and dark current of segmented silicon sensors are influenced by the charge and potential distributions on the sensor surface, the charge distribution in the oxide and passivation layers, and by Si–SiO 2 interface states. To better understand these phenomena, measurements on test structures and sensors before and after X-ray irradiation, and TCAD simulations including surface and interface effects are performed at the Hamburg Detector Lab. The main results of these investigations and ongoing studies are presented. [ABSTRACT FROM AUTHOR]

Using the methods of the field emission microscopy, the condensation of Si on the W surface at various temperatures T of the substrate and numbers n of monatomic layers of the deposited condensate is studied. At low temperatures of T ~ 600 K, a low-temperature Si monolayer with the structure of pure W is formed on the surface, whereas another structure of a high-temperature monolayer, namely, surface silicide, is formed at T ≥ 1000 K. The low-temperature monolayer and surface silicide also differ in their orienting effect when constructing the Si layers. In the case of condensation on a low-temperature monolayer, crystallites of Si are formed starting already from the third monolayer at n ≥ 3, whereas the Si crystallites grow during the condensation on surface silicide starting from n ≥ 300 monolayers. [ABSTRACT FROM AUTHOR]

A method for patterning on vertical silicon surfaces in high aspect ratio silicon topography is presented. A Faraday cage is used to direct energetic reactive ions obliquely through a patterned suspended membrane positioned over the topography. The technique is capable of forming high-fidelity pattern (100 nm) features, adding an additional fabrication capability to standard top-down fabrication approaches. [ABSTRACT FROM AUTHOR]

Organic/inorganic solid-state junctions play a critical role in tandem artificial photosynthetic devices supported by conducting polymer membranes. Recent work with n-Si/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid junctions has shown that the electrical behavior is dominated by the passivating groups present on the silicon surface. In this work, the photovoltaic behavior of n-Si/PEDOT:PSS was investigated with methyl, thiophene, and 3,4-ethylenedioxythiophene (EDOT) groups covalently attached to the Si(111) surface. X-ray photoelectron spectroscopy results demonstrated that complete monolayer coverage was achieved in 3 h and that the organic passivating groups were retained over two months of exposure to ambient conditions with minimal silicon oxidation. All surfaces investigated exhibited similar light-limited photocurrents and bulk-limited open-circuit voltages, and thiophene produced a dramatic reduction of the fill factor attributed to the formation of trap states at the interface. Furthermore, shunt behavior observed near the power-producing regions for the thiophene and EDOT surfaces is indicative of increased recombination events under forward bias and suggests that hole transport across the interface is enhanced. Thus, thiophene- and EDOT-functionalized Si(111) offer similar stabilities and efficiencies to those of methylated surfaces as well as enhanced hole transport to the PEDOT:PSS interface from the n-Si surfaces. [ABSTRACT FROM AUTHOR]

An ion beam treatment of high purity single crystal silicon specimens was performed with different shots by the irradiation of intense pulsed ion beams (IPIB), which were generated by an accelerating voltage of 350 kV and with the current density of 130 A/cm 2 . As the result of irradiation, the formation of various microstructures caused by the irradiation effect, especially the thermal effect is confirmed by SEM and XRD analysis, and the corresponding processes are described and related explanations are given. [ABSTRACT FROM AUTHOR]