Silicon Band Research Articles

Comparison of different etching methods on the morphology and semiconductor characters of black silicon

Femtosecond laser etching, deep reactive ion etching and metal-catalyzed chemical etching are used to fabricate black silicon. It has been found that the light absorption is significantly enhanced in the wavelength of 400∼2200nm, in which the absorption in near infrared band of black silicon etched by femtosecond laser with SF6 has the highest value. It is observed that, however, the minority carrier lifetime of crystalline silicon is shortened to some extent, which can be adjusted and controlled effectively by depositing SiNx film to passivate the surface of black silicon. Finally, a PIN photodetector is manufactured based on black silicon and a higher responsibility of 0.57 A/W at 1060 nm is obtained compared to the PIN silicon photodetector without etching process.

Laparoscopic liver resection using the silicone band uplift technique for tumors in segments 8 and 7 (with video)

Laparoscopic liver resection using the silicone band uplift technique for tumors in segments 8 and 7 (with video)

A Method for the Determination of Shear Moduli for n-Ge and n-Si Single Crystals

We obtain expressions for the determination of the shear moduli of n-Ge and n-Si single crystals subjected to uniaxial deformation. The proposed method is based on the mechanism of redistribution of electrons between the minima of conduction bands of germanium and silicon subjected to uniaxial compressive deformation along the crystallographic directions [111] and [100]. By using the obtained expressions and the results of the measurements of longitudinal piezoresistance for these single crystals, we determine their shear moduli.

Generation of surface electron states with a silicon–ultrathin-oxide interface under the field-induced damage of metal–oxide–semiconductor structures

The high-frequency capacitance–voltage characteristics of metal–oxide–semiconductor structures on n-Si substrates with an oxide thickness of 39 A are studied upon being subjected to damage by field stress. It is shown that the action of a high, but pre-breakdown electric field on an ultrathin insulating layer brings about the formation of a large number of additional localized interface electron states with an energy level arranged at 0.14 eV below the conduction band of silicon. It is found that, as the field stress is increased, the recharging of newly formed centers provides the accumulation of excess charge up to 8 × 1012 cm–2 at the silicon–oxide interface. The lifetime of localized centers created under field stress is two days, after which the dependences of the charge localized at the semiconductor–insulator interface on the voltage at the gate after and before field stress are practically the same.

Hierarchical and Selective Systems for Photoelectrochemical and Electrocatalytic Reduction of Carbon Dioxide

There has been growing interest in the photoelectrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. The reaction products are of potential importance to energy technology, food research, medical applications and fabrication of plastic materials. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the photo(electro)chemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered. Recently, we have concentrated on the development of hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. For example, the combination of titanium (IV) oxide and copper (I) oxide has been considered before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. Among important issue is intentional stabilization, activation, and functionalization of the mixed-metal-oxide-based photoelectrochemcal interface toward better long-term performance and selectivity production of small organic molecules (C1-C4) and other chemicals. In this respect, ultra-thin films of conducting polymers (simple or polyoxometallate-derivatized) and supramolecular complexes (with nitrogen containing ligands and certain transition metal sites), sub-monolayers of metals (Cu, Au), networks of noble metal (Au, Ag) nanoparticles or layers of robust bacterial biofilms have been considered. The photo-biocathode with Cu-containing enzyme has induced the reduction of not only oxygen but carbon dioxide as well, under illuminations with photon energies higher than silicon band gap. In the presentation, special attention will be paid to mechanistic aspects of electroreduction of carbon dioxide, fabrication and characterization of highly selective and durable semiconductor photoelectrode materials and to importance of the reaction conditions.

Modified Hamilton’s Controlled Encircling Procedure for Retinal Detachment

Purpose: To describe a novel, simple, and reproducible encircling scleral buckle technique based on Hamilton’s controlled encircling procedure in order to standardize buckle height achievement in cases of retinal detachment. Methods: We describe a case series in which a novel modification of Hamilton’s surgical technique was used, consisting of a typical encircling buckling procedure anchored in the center of each quadrant, with the ends of the band passed through a Watzke sleeve. Reference marks were placed to allow measurable shortening of the band when its ends were pulled to create an encircling indent. Postoperative ultrawide field retinal images were analyzed. Results: Our simple technique yielded predictable and reproducible postoperative scleral buckle heights. Shortening of the silicon band by 3, 4, 5, and 6.25 mm produced shallow indents, while additional shortening was considered excessive. Conclusion: Published studies about scleral buckle as a primary procedure or a combined technique with vitrectomy lack a uniform surgical technique. Our modification of Hamilton’s technique uses objective measurements to generate a consistent and predictable postoperative buckle height.

Optical Dependence of Electrically Detected Magnetic Resonance in Lightly Doped Si:P Devices

Electrically-detected magnetic resonance (EDMR) provides a highly sensitive method for reading out the state of donor spins in silicon. The technique relies on a spin-dependent recombination (SDR) process involving dopant spins that are coupled to interfacial defect spins near the Si/SiO$_2$ interface. To prevent ionization of the donors, the experiments are performed at cryogenic temperatures and the mobile charge carriers needed are generated via optical excitation. The influence of this optical excitation on the SDR process and the resulting EDMR signal is still not well understood. Here, we use EDMR to characterize changes to both phosphorus and defect spin readout as a function of optical excitation using: a 980 nm laser with energy just above the silicon band edge at cryogenic temperatures; a 405 nm laser to generate hot surface-carriers; and a broadband white light source. EDMR signals are observed from the phosphorus donor and two distinct defect species in all the experiments. With near-infrared excitation, we find that the EDMR signal primarily arises from donor-defect pairs, while at higher photon energies there are significant additional contributions from defect-defect pairs. The optical penetration depth into silicon is also known to be strongly wavelength dependent at cryogenic temperatures. The energy of the optical excitation is observed to strongly modulate the kinetics of the SDR process. Careful tuning of the optical photon energy could therefore be used to control both the subset of spin pairs contributing to the EDMR signal as well as the dynamics of the SDR process.

Sterilization Procedures: A Missed Opportunity to Prevent Cancer in Patients Treated at U.S. Residency Programs? [16A

INTRODUCTION: A recent paradigm shift indicates that the origin of ovarian high grade papillary serous carcinoma is the fallopian tube. The American College of Obstetricians and Gynecologists and Society of Gynecologic Oncology now recommend prophylactic salpingectomies as a preferred method of sterilization. This study sought to evaluate current practices of sterilization across U.S. Obstetrics and Gynecology (OB/Gyn) residency programs. METHODS: This is an IRB-approved study. An electronic cross-sectional survey of 13 questions was sent to all OB/Gyn program coordinators for distribution to their residents. There are 5,258 filled residency slots in OB/Gyn for the 2016-2017 academic year. RESULTS: Response rate was 6.4%, with even distribution across years. The majority of residents are in an academic setting (64.8%). For patients undergoing post-partum sterilization, 55% of patients were counselled about bilateral salpingectomy and tubal ligation. Postpartum tubal ligation only is offered at 51% of programs. For non-pregnant patients, 40.6% of residents counsel patients about bilateral tubal ligation, hysteroscopic sterilization and bilateral salpingectomy. The most common procedure performed is a bilateral salpingectomy (47.4%), followed by bipolar coagulation (21.8%), spring clips (19.3%), Silicone band method (6.9%) and hysteroscopic sterilization(4.7%). The most common reason cited for performing ligation instead of salpingectomy was perceived increased surgical risk such as bleeding or infection (45.2%). CONCLUSION: Though limited in our response rates, this study has several important implications. Despite recommended practice changes, prophylactic salpingectomy to prevent ovarian cancer has not gained widespread acceptance for either postpartum or interim sterilization. Many patients treated in residency are uninsured or socioeconomically disadvantaged and such procedures may offer a unique opportunity for cancer prevention.

(Invited) Modification of Electrocatalytic and Photoelectrochemical Interfaces Toward More Efficient Reduction of Carbon Dioxide

There has been growing interest in the photoelectrochemical conversion of carbon dioxide to useful carbon-based fuels or chemicals. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the photo(electro)chemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered. Recently, we have concentrated on the development of hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. For example, the combination of titanium (IV) oxide and copper (I) oxide has been considered before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. Among important issue is intentional stabilization, activation, and functionalization of the mixed-metal-oxide-based photoelectrochemcal interface toward better long-term performance and selectivity production of small organic molecules (C1-C4) and other chemicals. In this respect, ultra-thin films of conducting polymers (simple or polyoxometallate-derivatized) and supramolecular complexes (with nitrogen containing ligands and certain transition metal sites), sub-monolayers of metals (Cu, Au), networks of noble metal (Au, Ag) nanoparticles or layers of robust bacterial biofilms have been considered. We are also going to demonstrate that the photoinduced electron from semiconductor conduction band is capable of activation of the active center of the metalo-enzyme molecule. Here the.nanostructured silicon material has been chosen as the substrate for the enzyme adsorption. In this case the p-type Si(111) was etched toward formation of the bunched steps on the surface. The photo-biocathode with Cu-containing enzyme has induced the reduction of not only oxygen but carbon dioxide as well, under illuminations with photon energies higher than silicon band gap. In the presentation, special attention will be paid to mechanistic aspects of electroreduction of carbon dioxide, fabrication and characterization of highly selective and durable semiconductor photoelectrode materials and to importance of the reaction conditions.

Extracardiac approach to functional mitral regurgitation: a cost-effective approach to addressing heart failure

BackgroundHeart failure is frequently associated with severely impaired ventricular function and manifests often with functional mitral regurgitation (FMR). This is a complex syndrome that is primarily due to abnormal function...

Analysis of an anti-reflecting nanowire transparent electrode for solar cells

Transparent electrodes are an important component in many optoelectronic devices, especially solar cells. In this paper, we investigate a nanowire transparent electrode that also functions as an anti-reflection coating for silicon solar cells, taking into account the practical constraints that the electrode is typically encapsulated and needs to be in electric contact with the semiconductor. Numerical simulations show that the electrode can provide near-perfect broadband anti-reflection over much of the frequency range above the silicon band gap for both polarizations while keeping the sheet resistance sufficiently low. To provide insights into the physics mechanism of this broadband anti-reflection, we introduce a generalized Fabry–Perot model, which captures the effects of the higher order diffraction channels as well as the modification of the reflection coefficient of the interface introduced by the nanowires. This model is validated using frequency-domain electromagnetic simulations. Our work here provides design guidelines for nanowire transparent electrode in a device configuration that is relevant for solar cell applications.

Photoluminescence of Porous Silicon–Zinc Oxide Hybrid structures

Arrays of ZnO nanostructures, which are optically transparent in the visible range, were grown on the surface of porous silicon by electrochemical deposition. Photoluminescence excitation and emission spectra of the obtained hybrid structures were investigated in 220–450 and 400–800 nm regions, respectively. It is established that multicolor emission is formed by combining the luminescence bands of porous silicon and zinc oxide. The possibility of controlling the photoluminescence spectra by changing the excitation energy is demonstrated. It is revealed that thermal annealing has an effect on the luminescent properties of porous silicon/zinc oxide hybrid structures. Thermal processing at 500°С leads to a sharp decrease of long-wavelength luminescence associated with porous silicon and to an increase of short-wavelength luminescence intensity related to zinc oxide.

Observation of electron excitation into silicon conduction band by slow-ion surface neutralization

Bare reverse biased silicon photodiodes were exposed to 3 eV He+, Ne+, Ar+, N2+, N+ and H2O+ ions. In all cases an increase of the reverse current through the diode was observed. This effect and its dependence on the ionization energy of the incident ions and on other factors are qualitatively explained in the framework of Auger-type surface neutralization theory. Amplification of the ion-induced charge was observed with an avalanche photodiode under high applied bias. The observed effect can be considered as ion-induced internal potential electron emission into the conduction band of silicon. To the best of our knowledge, no experimental evidence of such effect was previously reported. Possible applications are discussed.

Coupled Thermodynamic and Kinetic Changes in the Electrochemistry of Ferrocenyl Monolayers Induced by Light.

We report on the light-induced systematic changes to the thermodynamics and kinetics of ferrocene units attached to a n-type silicon(100) photoelectrode. Both the reaction rate and the energetics of the charge transfer are simultaneously affected by changes in the intensity of the incident light. Cyclic voltammetry shows that increases in the intensity of illumination can drive the redox process toward less positive potentials, with a downhill shift in E1/2 of ca. 160 mV by increasing the light intensity from 3 to 94 mW cm-2. However, this thermodynamic shift is paralleled by an increase in the kinetics of the charge transfer. This latter observation-light-induced kinetic effects at monolayers on silicon electrodes-is made possible only by the stability of the surface chemistry construct. Furthermore, electrochemical impedance measurements showed that the electrodes exhibit faster electron-transfer kinetics under illumination than previously reported for ferrocene-terminated highly doped silicon (around 1 order of magnitude faster). An explanation for the kinetic effects is proposed on the basis of the consistent increase in photogenerated charge carriers inside silicon and the enlarged potential difference between the valence band of silicon and the surface-attached ferrocene.

Fabrication of Progesterone-Loaded Nanofibers for the Drug Delivery Applications in Bovine

Progesterone is a potent drug for synchronization of the estrus and ovulation cycles in bovine. At present, the estrus cycle of bovine is controlled by the insertion of progesterone-embedded silicone bands. The disadvantage of nondegradable polymer inserts is to require for disposal of these bands after their use. The study currently focuses on preparation of biodegradable progesterone-incorporated nanofiber for estrus synchronization. Three different concentrations (1.2, 1.9, and 2.5 g) of progesterone-impregnated nanofibers were fabricated using electrospinning. The spun membrane were characterized by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy. Uniform surface morphology, narrow size distribution, and interaction between progesterone and zein were confirmed by SEM. FTIR spectroscopy indicated miscibility and interaction between zein and progesterone. X-ray analysis indicated that the size of zein crystallites increased with progesterone content in nanofibers. Significant differences in thermal behavior of progesterone-impregnated nanofiber were observed by DSC. Cell viability studies of progesterone-loaded nanofiber were examined using MTT assay. In vitro release experiment is to identify the suitable progesterone concentration for estrus synchronization. This study confirms that progesterone-impregnated nanofibers are an ideal vehicle for progesterone delivery for estrus synchronization of bovines.

Pathogenesis of abdominal pain in bowel obstruction: role of mechanical stress-induced upregulation of nerve growth factor in gut smooth muscle cells.

Abdominal pain is one of the major symptoms in bowel obstruction (BO); its cellular mechanisms remain incompletely understood. We tested the hypothesis that mechanical stress in obstruction upregulates expression of nociception mediator nerve growth factor (NGF) in gut smooth muscle cells (SMCs), and NGF sensitizes primary sensory nerve to contribute to pain in BO. Partial colon obstruction was induced with a silicon band implanted in the distal bowel of Sprague-Dawley rats. Colon-projecting sensory neurons in the dorsal root ganglia (T13 to L2) were identified for patch-clamp and gene expression studies. Referred visceral sensitivity was assessed by measuring withdrawal response to stimulation by von Frey filaments in the lower abdomen. Membrane excitability of colon-projecting dorsal root ganglia neurons was significantly enhanced, and the withdrawal response to von Frey filament stimulation markedly increased in BO rats. The expression of NGF mRNA and protein was increased in a time-dependent manner (day 1-day 7) in colonic SMC but not in mucosa/submucosa of the obstructed colon. Mechanical stretch in vitro caused robust NGF mRNA and protein expression in colonic SMC. Treatment with anti-NGF antibody attenuated colon neuron hyperexcitability and referred hypersensitivity in BO rats. Obstruction led to significant increases of tetrodotoxin-resistant Na currents and mRNA expression of Nav1.8 but not Nav1.6 and Nav1.7 in colon neurons; these changes were abolished by anti-NGF treatment. In conclusion, mechanical stress-induced upregulation of NGF in colon SMC underlies the visceral hypersensitivity in BO through increased gene expression and activity of tetrodotoxin-resistant Na channels in sensory neurons.

Management of Complications Related to Laparoscopic Adjustable Silicone Gastric Band

Laparoscopic adjustable silicone gastric band (LASGB) is frequently used to treat morbidly obese patients worldwide. Complications related to this procedure have increased as the follow-up interval of these patients has increased. Treatment of these complications often includes removal of the silicone band. Herein we report our experience with silicone gastric band removal, discuss the different treatment alternatives, and present a management algorithm. A retrospective review of complications related to LASGB was made from June of 2003 to April of 2010 (eight patients). Techniques of band extraction are discussed and a management algorithm is presented. The mean Body Mass Index at the time of LASGB placement was 39.45 (Range 34.2 - 42.8). The median patient’s age at the time of LASGB was of 32.6 years (range: 13 to 50 years). The average durability of the silicone band after laparoscopic placement was 67.8 months (range: 6 to 120 months). In three patients (37.5%) the LASGB had perforated the gastric wall and was therefore extracted using a transgastric approach (laparoscopic in two patients and by laparotomy in one patient). In five patients the silicone band had not perforated the stomach and was therefore removed laparoscopically without entering the stomach. The weight was recovered in 37.5% of the patients during follow-up. Management of patients with complications related to LASGB placement must be individualized and should address both the band related complication as well as the obesity problem. Laparoscopic trans-gastric band extraction is ideal when the LASGB has eroded into the stomach and endoscopic extraction is not feasible.

Optical and Structural Properties of Silicon with Ion-Beam Synthesized InSb Nanocrystals

Transmission electron microscopy (TEM), Raman scattering (RS), and photoluminescence (PL) techniques are used to study the structure, phase composition, and radiative properties of silicon with implanted InSb nanocrystals produced by implanting Sb+ and In+ ions with energies of 350 keV and fluences of 3.5·1016 cm–2 followed by heat treatment at 1100°C for 3, 10, and 60 min. The TEM and RS data confirm the formation of InSb nanocrystals with sizes ranging from 2 to 50 nm in the implanted and annealed samples. A broad band in the 0.8–1.05 eV range is detected in low-temperature (4.2 K) PL spectra of the annealed samples. The possible mechanisms for the luminescence in this range are luminescence of InSb nanocrystals and radiative recombination between the conduction band of silicon and an In acceptor.

A Case of Silicone Band Migration Following an Encircling Procedure

A Case of Silicone Band Migration Following an Encircling Procedure

Valley splitting of single-electron Si MOS quantum dots

Silicon-based metal-oxide-semiconductor quantum dots are prominent candidates for high-fidelity, manufacturable qubits. Due to silicon's band structure, additional low-energy states persist in these devices, presenting both challenges and opportunities. Although the physics governing these valley states has been the subject of intense study, quantitative agreement between experiment and theory remains elusive. Here, we present data from an experiment probing the valley states of quantum dot devices and develop a theory that is in quantitative agreement with both this and a recently reported experiment. Through sampling millions of realistic cases of interface roughness, our method provides evidence that the valley physics between the two samples is essentially the same.