Silicon Band Research Articles

Silicone Band in the Surgical Treatment of Manifest Exotropia

Purpose: A silicone band was sutured anteriorly to the edge of the lateral rectus muscle neotendon during recession surgery in order to reduce and delay the reoccurrence after exotropia surgery. Methods: Collected data of 12 patients (8 males and 4 females), aged 7 - 54 years with diagnosis of constant manifest exotropia and mean angle deviation in primary position of 15,04o(sd 1,18) for near and of 13,23o (sd 0,71) for distance. All patients underwent surgical treatment consisting of lateral rectus recession and silicone band apposition in correspondence to the anterior edge of the lateral rectus muscle neotendon. Results: A substantial reduction of the mean angle deviation was observed in all patients after surgery. No adverse bandrelated effects were detected. Conclusion: The silicone band in the surgical treatment of manifest exotropia could be a valuable aid in delaying the relapse thanks to its physical and structural features and to its biocompatibility.

Indirect to direct band gap transition in ultra-thin silicon films

Free standing silicon layers undergo a transition from indirect to direct band gap semiconductor, which predicts a new possible way in silicon band gap engineering. The thickness and crystal orientation of the exposed surface are crucial. Our simulations reveal that the (100) films with thickness of ∼1.05 nm and (110) films with thickness of ∼1.14 nm could maintain the direct band gap structure. However, the (111) films always show indirect band gap structure even if the monolayer is constructed. The electron states density calculations were also carried out and the transition of the band gap structure is considered to be determined by the quantum confinement and surface termination conditions. The momentum matrix element calculations were also carried out, approving the effective direct band gap transitions for these ultra-thin films.

The electrical and photoconductivity characteristics of donor-acceptor alternating copolymer using solution process

The authors report on the electrical and photoconductivity characteristics of donor-acceptor alternating copolymer, poly(dioctyloxinapthalenediketopyrrolopyrrole) (PONDPP) with Al/PONDPP/p-Si/Al hybrid organic/inorganic Schottky diode for optoelectronic applications. The fabricated device shows ideality factor value of 2.6 and barrier height of 0.68 eV obtained from current-voltage characteristics. The high rectification ratio of 1.86 × 104 and photo-responsivity of 55 mA/W at 650 nm is achieved. From results, we found that the fine photo-response and electrical characteristics are attributed to the modified band-gap structure to have Schottky barrier at highest occupied molecular orbital to valence band of silicon and high hole mobility of PONDPP.

Energetic spectra of dislocation networks produced by hydrophilic bonding of silicon wafers

AbstractElectronic states of dislocation networks produced by Si wafers bonding was studied by means of deep level transient and admittance spectroscopy methods. A strong field‐enhanced hole thermoemission was established for one shallow and one deep states in p‐type Si that was explained in the framework of dislocation‐related Poole‐Frenkel‐effect model. The shallow dislocation related states situated close to the valence as well as to the conduction band of silicon were found to be associated with the broad energetic bands with rapid interstate exchange. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Gate tunable graphene-silicon Ohmic/Schottky contacts

We show that the I-V characteristics of graphene-silicon junctions can be actively tuned from rectifying to Ohmic behavior by electrostatically doping the graphene with a polymer electrolyte gate. Under zero applied gate voltage, we observe rectifying I-V characteristics, demonstrating the formation of a Schottky junction at the graphene-silicon interface. Through appropriate gating, the Fermi energy of the graphene can be varied to match the conduction or valence band of silicon, thus forming Ohmic contacts with both n- and p-type silicon. Over the applied gate voltage range, the low bias conductance can be varied by more than three orders of magnitude. By varying the top gate voltage from −4 to +4 V, the Fermi energy of the graphene is shifted between −3.78 and −5.47 eV; a shift of ±0.85 eV from the charge neutrality point. Since the conduction and valence bands of the underlying silicon substrate lie within this range, at −4.01 and −5.13 eV, the Schottky barrier height and depletion width can be decreased to zero for both n- and p-type silicon under the appropriate top gating conditions. I-V characteristics taken under illumination show that the photo-induced current can be increased or decreased based on the graphene-silicon work function difference.

Hindpaw Withdrawal from a Painful Thermal Stimulus after Sciatic Nerve Compression and Decompression in the Diabetic Rat

Although the effect of chronic compression and surgical decompression of the diabetic rat sciatic nerve has been evaluated by walking track analysis, the measurement of sensory function by response to thermal nociceptive stimulation has not been investigated. Fifteen male Wistar rats with streptozotocin-induced diabetes underwent sciatic nerve compression through a 10-mm silicone band. Five rats had histology done 60 days after confirming chronic nerve compression. Pain threshold was measured using hindlimb withdrawal times (HLWT) from a heat stimulus. After 60 days of compression, the silicone tube was removed. Five nondiabetic, nonbanded rats were used as controls. Control mean HLWT was 9.7 ± 1.5 sec. In the diabetes group (60 days of compression), mean HLWT was 23.6 ± 2.4 sec. (p < 0.001). Thirty days after removal of the silicone, mean HLWT to painful stimuli was 14.9 ± 1.5 sec. (p < 0.001). Chronic compression of the diabetic rat sciatic nerve increases (worsens) the threshold to heat (pain) perception. Decompression reverses this effect (improves nociception).

Physical understanding of negative bias temperature instability below room temperature

The physical mechanism of VT degradations under negative bias temperature stress below room temperature has been studied for SiO2 and plasma nitrided oxide (PNO-based) pMOSFETs. It is found that VT degradations in both devices exhibit strong dependence on the electric field and temperature. The analysis shows that this strong dependence follows multi-phonon field-assisted tunneling theory, which indicates the inelastic hole trapping mechanism in the low temperature negative bias temperature instability (NBTI). On the other hand, by applying a low temperature sweeping technique, the energy distribution of these NBTI-induced hole traps below room temperature is indentified. The energy distribution of hole traps has two obvious peaks, one in the lower and one in the upper half of the silicon band gap. Both peaks gradually develop with increasing the stress time and temperature. We attempt to compare the energy profile for SiO2 and PNO devices to identify the trap precursors in NBTI below room temperature.

Enhanced Photocurrents of Photosystem I Films on p‐Doped Silicon

Tuning the Fermi energy of silicon through doping leads to alignment of silicon bands with the redox active sites of photosystem I. Integrating photosystem I films with p-doped silicon results in the highest reported photocurrent enhancement for a biohybrid electrode based on photosystem I.

Quantitative analysis of chromate (CrVI) by normal Raman spectroscopy and surface-enhanced Raman spectroscopy using poly(diallyldimethylammonium) chloride-capped gold nanoparticles

Chromate (CrVI) has emerged as a widespread environmental contaminant found in groundwater and surface water, and there is a great need for rapid detection and monitoring of this contaminant. Normal Raman scattering (NRS) spectroscopy with a detection limit of CrVI at concentrations of 0.2 g/L was attached. And surface-enhanced Raman scattering (SERS) spectroscopy technique was found to be capable of detecting CrVI at concentrations as low as 2.5 mg/L using poly(diallyldimethylammonium) chloride modified gold nanoparticles (PDDA-AuNPs) as a substrate. The SERS substrate was successfully fabricated by combining the selfassembly technique with a heat-treatment-based strategy using poly(diallyldimethylammonium) chloride (PDDA) as the reducing and stabilizing agents. With the 520 cm−1 band of silicon as internal standard, band intensity ratios of CrVI to silicon, that is I 902/I 520, were found to have a quantitative relationship with a large concentration range of CrVI from 0.2 to 20.0 g/L for NRS (R 2 = 0.994) and from 2.5 to 25.0 mg/L for SERS (R 2 = 0.980), respectively. Besides, the SERS methodology was reproducible, and susceptible to the interference of pH value. The optimum pH for CrVI detection by SERS was 3.38. The application of NRS and SERS showed high practical potential for rapid screening and routine analysis of CrVI in environmental samples.

Surface-Enhanced Raman Scattering for Quantitative Analysis of Perchlorate Using Poly(diallyldimethylammonium chloride) Capped Gold Nanoparticles

Perchlorate (ClO4−) has emerged as a widespread environmental contaminant found in groundwater and surface water and there is a great need for rapid detection and monitoring of this contaminant. Surface-enhanced Raman scattering (SERS) spectroscopy was found to be capable of detecting ClO4− at concentrations as low as 25 μg/L using poly(diallyldimethylammonium chloride)-modified gold nanoparticles (PDDA-AuNPs) as a substrate. The substrate was successfully fabricated by combining the self-assembly technique with a heat-treatment-based strategy using poly(diallyldimethylammonium chloride) (PDDA) as the reducing and stabilizing agents. With the 520 cm−1 band of silicon as external standard, band intensity ratios of perchlorate to silicon, (i.e., I931/ I520) were found to have a quantitative relationship with a large concentration range of perchlorate between 25 μg/L and 50 mg/L. The methodology was also reproducible and not susceptible to the interference of other anions such as sulfate, carbonate, nitrate, and chloride at concentrations of 1 mM, making it potentially suitable for rapid screening and routine analysis of perchlorate in environmental samples.

Recurrent retinal detachment secondary to hereditary congenital collagen disease

AbstractPurpose Hereditary progressive arthro‐ophthalmopathy, also called Stickler syndrome, is an autosomal dominant genetic disease affecting connective tissue collagen. It is considered the leading cause of inherited retinal detachment in all ages and produces multisystem manifestations such as premature arthritis, micrognathia or eye disorder.Methods A 31‐year‐old man reports hereditary progressive arthro‐ophthalmopathy. He presented degenerative myopia, congenital cataract and bilateral recurrent retinal detachments during childhood. At birth, he presented craniofacial anomalies, hearing loss and flat feet. When he was 6 years old, he suffered a retinal detachment associated with giant tear, which was treated with 20G pars plana vitrectomy and injection of silicone oil. At 22 years, the right eye presented another retinal detachment that was treated with silicone band placement, cryotherapy and C3F8 gas intravitreal injection. Two months later the retinal detachment recurred in right eye, needing 23 G pars plana vitrectomy and intravitreal silicone oil implantation.Results The patient presented several ophthalmic complications such as post‐surgical ocular hypertension and retinal tears requiring selective photocoagulation with argon laser in the right eye. Recently, genetic diagnosis was confirmed by COL11A1 gene mutation.Conclusion Development, prevention and therapeutic management of ophthalmic complications during 26 years follow‐up are presented. The importance of early diagnosis and follow‐up by a vitreoretinal surgeon are also emphasized.

Porous silicon nanocrystals in a silica aerogel matrix

Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation.

Cellular mechanism of mechanotranscription in colonic smooth muscle cells.

Mechanical stretch in obstruction induces expression of cyclooxygenase-2 (COX-2) in gut smooth muscle cells (SMCs). The stretch-induced COX-2 plays a critical role in motility dysfunction in obstructive bowel disorders (OBDs). The aims of the present study were to investigate the intracellular mechanism of mechanotranscription of COX-2 in colonic SMCs and to determine whether inhibition of mechanotranscription has therapeutic benefits in OBDs. Static stretch was mimicked in vitro in primary culture of rat colonic circular SMCs (RCCSMCs) and in colonic circular muscle strips. Partial obstruction was surgically induced with a silicon band in the distal colon of rats and COX-2-deficient mice. Static stretch of RCCSMCs significantly induced expression of COX-2 mRNA and protein and activated MAP kinases ERKs, p38, and JNKs. ERKs inhibitor PD98059, p38 inhibitor SB203580, and JNKs inhibitor SP600125 significantly blocked stretch-induced COX-2 expression. Pharmacological and molecular inhibition of stretch-activated ion channels (SACs) and integrins significantly suppressed stretch-induced expression of COX-2. SAC blockers inhibited stretch-activated ERKs, p38, and JNKs, but inhibition of integrins attenuated p38 activation only. In colonic circular muscle strips, stretch led to activation of MAPKs, induction of COX-2, and suppression of contractility. Inhibition of p38 with SB203580 blocked COX-2 expression and restored muscle contractility. Administration of SB203580 in vivo inhibited obstruction-induced COX-2 and improved motility function. Stretch-induced expression of COX-2 in RCCSMCs depends on mechanosensors, SACs, and integrins and an intracellular signaling mechanism involving MAPKs ERKs, p38, and JNKs. Inhibitors of the mechanotranscription pathway have therapeutic potentials for OBDs.

A Nested-Reactance Feedback Power Amplifier for $Q$-Band Applications

A power amplifier (PA) topology is presented that incorporates a feedback network around the transistor to satisfy matching requirements. Circuit parameters can be tuned for small- and large-signal circuit operation. The PA is fabricated in a 120-nm SiGe BiCMOS process and performs from 36 to 41 GHz. The PA achieves a saturated output power of 23 dBm and a peak power-added efficiency of 20% at 38 GHz. This is the highest reported output power from a single PA at Q -band in silicon.

(Invited) Electroluminescence in Metal-Oxide-Semiconductor Tunnel Diodes with Nanometer-Thick Silicon

Electroluminescence in metal-oxide-semiconductor tunnel diodes with a transparent conductive oxide gate and a nanometer-thick silicon layer on silicon-on-insulator substrates has been studied. The electroluminescence spectra from the diodes are peaked at ~1120 nm (~1.11 eV). The peak shifts toward lower energy as the negative gate voltage value increases. The peak shift can be explained by a Stark effect. The peak tail intensity at the short-wavelength side of the peak at ~1120 nm increases as the silicon layer thickness decreases. This may indicate that the increase in the intensity is due to transitions between subbands near the silicon band edges. Small peaks have been observed at ~1050 nm (~1.18 eV) and ~1010 nm (~1.23 eV). The peak wavelengths are independent of the silicon layer thickness. This exhibits that the electroluminescence is due to defect-mediated transitions.

The thermal stability of atomic layer deposited HfLaOx: Material and electrical characterization

HfLaOx based Metal–oxide–semiconductor capacitors were fabricated by atomic layer deposition in this work. The material and electrical properties of the films along with the high temperature thermal treatment were investigated. It was found that samples undergoing annealing at 900 °C exhibited the best performance. The film was found to be crystallized to a cubic structure at 900 °C, and the roughness of the films was estimated to be 0.332 nm. For electrical characterization, the C–V curve of the film is in good agreement with the corresponding simulated curve, and the capacitor does not show any hysteresis. Moreover, the Dit near the center of silicon band gap exhibits lowest value, and it was calculated to be 2.28 × 1011 eV−1 cm−2.

Comparison of superior oblique suture spacers and superior oblique silicone band expanders

To compare suture spacers with silicone band expanders in superior oblique-weakening surgery. We retrospectively reviewed the charts of consecutive patients who had superior oblique weakening with either suture spacers or silicone expanders and had been followed for a minimum follow-up of 6 months. The ductions, versions, and the degree of fundus torsion were analyzed in all patients before and after surgery. In addition, surgery time and postoperative complications were analyzed. The record review identified 25 patients, of whom 13 had been treated with superior oblique muscle suture spacers and 12 with superior oblique muscle silicone expanders. Both groups showed improved ductions and versions. In patients with Brown syndrome, complete normalization of superior oblique muscle overaction occurred in 67% of patients who had suture spacers and 67% of patients who had silicone expanders. In patients with A-pattern strabismus, normal function of the superior oblique muscle occurred in 75% of patients with suture spacers and 67% of patients with silicone expanders. Surgery time was significantly less in patients who had suture spacers. Severe orbital inflammation occurred in 1 patient around the silicone band and was managed by removal of the implant. Both suture spacers and silicone expanders improved the comitance of versions and normalized superior oblique muscle function. Longer surgery time and more severe inflammatory reaction are possible drawbacks of silicone expanders.

Study of radiation damage induced by 12 keV X-rays in MOS structures built on high-resistivityn-type silicon

Imaging experiments at the European X-ray Free Electron Laser (XFEL) require silicon pixel sensors with extraordinary performance specifications: doses of up to 1 GGy of 12 keV photons, up to 10(5) 12 keV photons per 200 µm × 200 µm pixel arriving within less than 100 fs, and a time interval between XFEL pulses of 220 ns. To address these challenges, in particular the question of radiation damage, the properties of the SiO(2) layer and of the Si-SiO(2) interface, using MOS (metal-oxide-semiconductor) capacitors manufactured on high-resistivity n-type silicon irradiated to X-ray doses between 10 kGy and 1 GGy, have been studied. Measurements of capacitance/conductance-voltage (C/G-V) at different frequencies, as well as of thermal dielectric relaxation current (TDRC), have been performed. The data can be described by a dose-dependent oxide charge density and three dominant radiation-induced interface states with Gaussian-like energy distributions in the silicon band gap. It is found that the densities of the fixed oxide charges and of the three interface states increase up to dose values of approximately 10 MGy and then saturate or even decrease. The shapes and the frequency dependences of the C/G-V measurements can be quantitatively described by a simple model using the parameters extracted from the TDRC measurements.

Interim Results from the International Trial of Second Sight's Visual Prosthesis

This study evaluated the Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc., Sylmar, CA) in blind subjects with severe outer retinal degeneration. Single-arm, prospective, multicenter clinical trial. Thirty subjects were enrolled in the United States and Europe between June 6, 2007, and August 11, 2009. All subjects were followed up for a minimum of 6 months and up to 2.7 years. The electronic stimulator and antenna of the implant were sutured onto the sclera using an encircling silicone band. Next, a pars plana vitrectomy was performed, and the electrode array and cable were introduced into the eye via a pars plana sclerotomy. The microelectrode array then was tacked to the epiretinal surface. The primary safety end points for the trial were the number, severity, and relation of adverse events. Principal performance end points were assessments of visual function as well as performance on orientation and mobility tasks. Subjects performed statistically better with the system on versus off in the following tasks: object localization (96% of subjects), motion discrimination (57%), and discrimination of oriented gratings (23%). The best recorded visual acuity to date is 20/1260. Subjects' mean performance on orientation and mobility tasks was significantly better when the system was on versus off. Seventy percent of the patients did not have any serious adverse events (SAEs). The most common SAE reported was either conjunctival erosion or dehiscence over the extraocular implant and was treated successfully in all subjects except in one, who required explantation of the device without further complications. The long-term safety results of Second Sight's retinal prosthesis system are acceptable, and most subjects with profound visual loss perform better on visual tasks with system than without it.

Tailoring the Absorption Properties of Black Silicon

Samples of crystalline silicon for use as solar cell material are structured and hyperdoped with sulfur by irradiation with femtosecond laser pulses under a sulfur hexafluoride atmosphere. The sulfur creates energy levels in the silicon band gap, allowing light absorption in the infrared wavelength regime, which offers the potential of a significant efficiency increase. This Black Silicon is a potential candidate for impurity or intermediate band photovoltaics. In this paper we determine the laser processed sulfur energy levels by deep-level transient spectroscopy (DLTS). We present how the number of laser pulses per sample spot influence the sulfur energy levels and hence the DLTS spectra. Further we show that changing the laser pulse by splitting it with a Michelson interferometer setup results in altered absorption which is most likely due to altered sulfur energy levels. This contribution focuses on the possibility of controlling the sulfur in Black Silicon through manipulating the laser pulse shape. As a first step samples of microstructured silicon are fabricated with doubled laser pulses at two different laser pulse distances and the absorption spectra by integrating sphere measurements are compared.