Epitaxial germanium growth and electrical characterization

Low bandgap Ge homojunctions are normally used in photovoltaic multiple junction solar cells or thermo-photovoltaic cells and are usually realized by thermal diffusion, starting from an n-type or p-type substrate. However the diffusion process itself intrinsically precludes the possibility to obtain sharp junctions and to control the doping profile. A better thickness and doping control could be achieved by epitaxial deposition of Ge junctions, with the aim to obtain better photovoltaic efficiencies. Single junction epitaxial Ge cells with high efficiency could find use either in III-V multijunction high efficiency solar cells or in thermophotovoltaic devices coupled to a burner and to suitable selective emitters based on rare earth elements. The samples presented in this talk were deposited by means of Metal Organic Vapur Phase Epitaxy (MOVPE) on Ge and on GaAs using Iso-Butyl Germane (iBuGe) as organic precursor. Structures of different thickness were growth by varying the deposition temperature between 400 and 700?C on n and p-type Ge substrates and on GaAs substrate. Arsenic was used as both doping element and as surfactant: in the latter case it was found to improve the epitaxial quality at low temperature. Memory effect of AsH3 in the MOVPE reactor will be discussed. Nominally undoped Ge was found to be p-type, while n-type doping is obtained with the use of AsH3. n/p and p/n junctions were obtained by using a p or n substrate and depositing a n or p type layer, respectively. A completely epitaxial n/p junction on a p Ge substrate was also deposited. Vertical Ge/Ge mesa junctions were prepared on the above structures by using conventional photolithographic techniques. Ohmic contacts were obtained by evaporation, followed by a thermal annealing at 250 ?C for 60 seconds, of Au on the backside of the ptype substrate and by evaporation of Au dots, 400 mm in diameter, onto the n-type epilayer. 500 mm mesa structures, concentric to Au dots, were then prepared by chemical wet etching in a solution of H2O2 : H2O. I-V, C-V, DLTS and EBIC techniques were used for electrical characterization of the layers. Typical I-V characteristics of the mesa structure show rectification in the range of 104, reverse currents lower than 10-6 A at 1 V and ideality factor in the 1.008-1.010 range. The good rectifying properties indicate that the nominally undoped Ge layer is n-type. Capacitance-Voltage (C-V) measurements suggest that the doping of the epitaxial Ge layer is expected to be higher than that of the substrate

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe

Analysis of the Temperature Dependence of the Capacitance-Voltage and Conductance-Voltage Characteristics of Au/TiO2(rutile)/n-Si Structures

The capacitance-voltage-temperature (C-V-T) and the conductance/angular frequency-voltage-temperature (G/omega-V-T) characteristics of Au/TiO2(rutile)/n-Si Schottky barrier diodes (SBDs) were investigated over the temperature range from 200 K to 380 K by considering the series resistance effect. Titanium dioxide (TiO2) was deposited on n-type silicon (Si) substrate using a direct-current (DC) magnetron sputtering system at 200A degrees C. To improve the crystal quality, the deposited film was annealed at 900A degrees C to promote a phase transition from the amorphous to rutile phase. The C (-2) versus V plots gave a straight line in the reverse-bias region. The main electrical parameters, such as the doping concentration (N (D)), Fermi energy level (E (F)), depletion layer width (W (D)), barrier height (N" (CV)), and series resistance (R (S)), of Au/TiO2(rutile)/n-Si SBDs were calculated from the C-V-T and the G/omega-V-T characteristics. The obtained results show that N" (CV), R (S), and W (D) values decrease, while E (F) and N (D) values increase, with increasing temperature

Thermo-physiological comfort properties of various shirt fabrics treated with conventional and nano sized water-oil repellent and wrinkle resistant agents

The extreme temperatures and humidity are quite disturbing climatic conditions and clothing is the only protective material in these cases. During the interactions of the human body, clothing, and the environment, to maintain thermal equilibrium, thermo physiological comfort is crucially important. In general, the thermo physiological comfort features of a fabric include thermal conductivity, thermal flow, thermal absorbtivity, thermal resistance, thickness, water vapor permeability and air permeability. In this study, 21 different kinds of woven shirt fabrics produced from fibers in various blends have been treated with both classical and nano chemicals in four different concentrations to produce fabrics having different water-oil repellent and wrinkle resistant characteristics. The effects of the fiber type, treatment method, chemical type, and chemical concentration on the thermal, water vapor and air permeability properties of the fabrics treated with various finishing processes were investigated by statistical analysis. The results of thermal related properties, air permeability and water vapor permeability of the fabrics confirmed that using cotton, lyocell, and viscose shirt fabrics treated with transfer method could be advantageous, especially in hot climatic regions.Research Foundation of Ege University [2006-MuH-053]The authors acknowledge the Research Foundation of Ege University for the financial support given to this study (Project number: 2006-MuH-053)

Effect of platinum doping on the structural and electrical properties of SnO2 thin films

The investigation of Pt doping effect on the structural and electrical properties of SnO2 thin films was aimed in this study. For this purpose, the polycrystalline pure and Pt-doped SnO2 thin films were deposited onto n-type silicon substrate and the Pt sputter power was varied as 0 (un-doped), 2, 5 and 7 W by using radio frequency confocal sputtering system. The structural properties of the samples were analysed by X-ray diffraction measurements. The structural results show that the 5 W Pt-doped SnO2 sample has better crystallinity than the other samples. The results of the electrical measurements as current-voltage, capacitance-voltage and conductance-voltage were also obtained and discussed in detail for fabricated diodes. The analysis of electrical characteristics shows that the use of different Pt doping has significant effect on electrical properties of such devices. The study also provides an improved supplemental understanding to the related technologies which use Pt-doped SnO2 materials

The temperature dependent analysis of Au/TiO2 (rutile)/n-Si (MIS) SBDs using current-voltage-temperature (I-V-T) characteristics

In this study, the main electrical parameters of Au/TiO2(rutile)/n-Si Schottky barrier diodes (SBDs) were analyzed by using current-voltage-temperature (I-V-T) characteristics in the temperature range 200-380 K. Titanium dioxide (TiO2) thin film was deposited on a polycrystalline n-type Silicon (Si) substrate using the DC magnetron sputtering system at 200 degrees C. In order to improve the crystal quality deposited film was annealed at 900 degrees C in air atmosphere for phase transition from amorphous to rutile phase. The barrier height (Phi(b)) and ideality factor (n) were calculated from I-V characteristics. An increase in the value of Phi(b) and a decrease in n with increasing temperature were observed. The values of Phi(b) and n for Au/TiO2(rutile)/n-Si SBDs ranged from 0.57 eV and 3.50 (at 200 K) to 0.82 eV and 1.90 (at 380 K), respectively. In addition, series resistance (R-s) and Phi(b) values of MIS SBDs were determined by using Cheung's and Norde's functions. Cheung's plots are obtained from the donward concave curvature region in the forward bias semi-logarithmic I-V curves originated from series resistance. Norde's function is easily used to obtain series resistance as a function of temperature due to current counduction mechanism which is dominated by thermionic emission (TE). The obtained results have been compared with each other and experimental results show that R-s values exhibit an unusual behavior that it increases with increasing temperature. (C) 2012 Elsevier Ltd. All rights reserved

Profound hypoglycemia-ύnduced by vaccinium corymbosum juice and laurocerasus fruit

cure, erkan/0000-0001-7807-135X; Cure, Medine Cumhur/0000-0001-9253-6459WOS: 000348563500019PubMed: 25097289An emergency intervention was performed in a 75-year-old male patient with hypoglycemic attack and blackout. Although he was diagnosed with prediabetes before 2 years, he did not take any anti-diabetic drug or follow dietary advice. He drank Vaccinium corymbosum L (VC) juice daily with a belief that it increases sexual potency. Before the development of hypoglycemia, the patient had consumed about 500 ml VC juice in addition to eating 200-300 gram of Laurocerasus officinalis (LO) fruit. the measured plasma glucose (PG) level during loss of consciousness was 30 mg/dl. the profound hypoglycemia may be an unexpected side effect of an interaction between the chemical compositions of the two plants, occurred as a result of LO fruit intake that may have a strong PG-lowering effect or related to excessive intake of VC juice. Both plants may be considered in the alternative treatment of diabetes

Analysis of the forward and reverse bias I-V characteristics on Au/PVA: Zn/n-Si Schottky barrier diodes in the wide temperature range

In this study, the forward and reverse bias current-voltage (I-V) characteristics of Au/Zinc acetate doped polyvinyl alcohol/n-Si Schottky barrier diodes (SBDs) have been investigated over the temperature range of 80-400 K. The values of zero-bias barrier height evaluated from forward and reverse bias I-V data, (Phi(BFo)) and (Phi(BRo)), increase with increasing temperature, and a discrepancy is observed between the values of Phi(BFo) and Phi(BRo). Because the apparent barrier height (BH) seen from metal to semiconductor is higher than the one seen from semiconductor to metal, the obtained value of Phi(BFo) is always greater than Phi(BRo) value. The difference between them is almost the same as the Fermi energy level. The crossing of the experimental forward bias semilogarithmic ln I-V plots appears as an abnormality when compared to the conventional behavior of ideal SBDs. This behavior was attributed to the lack of free charge at a low temperature and could be expected in the temperature region where there is no carrier freezing out, which is non-negligible at low temperatures. Prior to intersection, the voltage dependent value of resistance (R-i) obtained from Ohm's law decreases with increasing temperature, but it begins to increase after this intersection point. Such an increase in Phi(Bo) and series resistance (R-s) with temperature corresponding to high voltage region is in obvious disagreement with the reported negative temperature coefficients. However, the value of shunt resistance (R-sh) corresponding to a low or negative voltage region decreases with increasing temperature. In addition, the temperature dependent energy density distribution profiles of interface states (N-ss) were obtained from forward bias I-V measurements by taking into account the bias dependence of the effective barrier height (Phi(e)) and R-s of the device, and the values of Nss without considering Rs are almost one order of magnitude larger than N-ss when considering Rs value. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552599

AZO thin film-based UV sensors: effects of RF power on the films

Al-doped zinc oxide (AZO) thin films of thickness 150 nm were deposited on polyethylene terephthalate (PET) substrates by radio frequency (RF) magnetron sputtering method under various RF powers in the range of 25-100 W. Structural, morphological, optical and electrical properties of the films were investigated by X-ray diffractometer, atomic force microscope, UV-Vis spectrometer and Hall effect measurement system. All the obtained films had a highly preferred orientation along [002] direction of the c-axis perpendicular to the flexible PET substrate and had a high-quality surface. The energy band gap (E-g) values of the films varied in the range of 3.30-3.43 eV. The minimum resistivity of 1.84 x 10(-4) Omega cm was obtained at a 50 W RF power. The small changes in the RF power had a critical important role on the structural, optical and electrical properties of the sputtered AZO thin films on flexible PET substrate. In addition, UV sensing of the fabricated AZO thin film-based sensors was explored by using current-voltage (I-V) characteristics. The sensors were sensitive in the UV region of the electromagnetic spectrum