Electric Field Effect Analysis of Thin PbTe films on high-epsilon SrTiO3 Substrate

Thin PbTe films (thickness 500 - 600 angstrom), deposited on SrTiO3, have been investigated by electric field effect (EFE). The high resistivity of such thin films warrants a high sensitivity of the EFE method. The SrTiO3 substrate serves as the dielectric layer in the Gate-Dielectric-PbTe structure. Due to the large dielectric constant of SrTiO3, particularly at low temperatures, the electric displacement D in the film reaches the high value of about 10^8 V/cm, and the EFE introduced charge into the PbTe film amounts to ~ 8 microC/cm2. The high D permits to measure the EFE resistance and Hall constant over a wide region of D, revealing the characteristic features of their D-dependence. An appropriate theoretical model has been formulated, showing that, for such films, one can measure the dependence of the Fermi level on D. In fact, we demonstrate that shifting the Fermi level across the gap by varying D, the density-of-states of the in-gape states can be mapped out. Our results show, that the PbTe layers studied, possess a mobility gap exceeding the gap of bulk PbTe.Comment: 27 pages, 12 figure

Thermal Wave Induced Edge Electrical Field of Pyroelectric: Spatial Pattern Mapping and Effect of Ambient Conditions

We have recently analyzed theoretically the main characteristics of the edge depolarizing electric field (EDEF), in the vicinity of a non-polar face of a pyroelectric. In this work we measured and characterized the EDEF, excited by a harmonical thermal wave. We present here experimental results obtained on a pyroelectric crystal LiTaO3, confirming our theoretical predictions. We present the theoretical analysis and description of the thermal wave and the induced harmonically varying EDEF. The calculations assume an equivalent circuit of a pyroelectric capacitive current source. The measured magnitude of the EDEF and its spatial variation agree well with the theoretical model. The effect of the air pressure at the pyroelectric/air interface, on the EDEF, was determined in the interval 10^3 - 10^-6 torr. We found that EDEF increases significantly with decreasing air pressure, presumably due to diminishing of adsorption screening at the polar faces. Teflon plates, covering the polar faces, prevent accumulation of screening charged particles, resulting in a drastic increase of EDEF

Characterization of high-temperature PbTe p-n junctions prepared by thermal diffusion and by ion-implantation

We describe here the characteristics of two types of high-quality PbTe p-n-junctions, prepared in this work: (1) by thermal diffusion of In4Te3 gas (TDJ), and (2) by ion implantation (implanted junction, IJ) of In (In-IJ) and Zn (Zn-IJ). The results, as presented here, demonstrate the high quality of these PbTe diodes. Capacitance-voltage and current-voltage characteristics have been measured. The measurements were carried out over a temperature range from ~ 10 K to ~ 180 K. The latter was the highest temperature, where the diode still demonstrated rectifying properties. This maximum operating temperature is higher than any of the earlier reported results. The saturation current density, J0, in both diode types, was ~ 10^-5 A/cm2 at 80 K, while at 180 K J0 ~ 10^-1 A/cm2 in TDJ and ~ 1 A/cm2 in both ion-implanted junctions. At 80 K the reverse current started to increase markedly at a bias of ~ 400 mV for TDJ, and at ~550 mV for IJ. The ideality factor n was about 1.5-2 for both diode types at 80 K. The analysis of the C-V plots shows that the junctions in both diode types are linearly graded. The analysis of the C-V plots allows also determining the height of the junction barrier, the concentrations and the concentration gradient of the impurities, and the temperature dependence of the static dielectric constant. The zero-bias-resistance x area products (R0Ae) at 80 K are: 850 OHMcm2 for TDJ, 250 OHMcm2 for In-IJ, and ~ 80 OHMcm2 for Zn-IJ, while at 180 K R0Ae ~ 0.38 OHMcm2 for TDJ, and ~ 0.1 OHMcm2 for IJ. The estimated detectivity is: D* ~ 10^10 cmHz^(1/2)/W up to T=140 K, determined mainly by background radiation, while at T=180 K, D* decreases to 108-107 cmHz^(1/2)/W, and is determined by the Johnson noise

ДЕВИТАЛИЗИРОВАННЫЕ СОСУДИСТЫЕ ПРОТЕЗЫ: ИССЛЕДОВАНИЕ IN VIVO

Porcine intrathoracic arteries were devitalized by application of low temperatures and electron beam irradiati- on. The resulted connective tissues vascular scaffolds could be used as the prosthesis of small diameter arteries (≤6 mm). Biocompatibility, immunogenicity degree and thrombogenicity were estimated in the study. Results of electron microscopy are presented. Described treatment reduces an immunogenicity of xenoarteries, their ade- quate functioning during 6 months was shown by means of experimental surgeries. Для девитализации внутренних грудных артерий свиней использовали низкие температуры и облучение потоком электронов. Полученные соединительнотканные сосудистые скаффолды в данном исследовании были использованы в качестве протезов артерий малого диаметра (≤6 мм). В работе изучали биосовме- стимость, степень иммуногенности, тромбогенность девитализированных артерий. Приведены результа- ты электронной микроскопии. Показано снижение иммуногенности девитализированных ксеноартерий. Экспериментальные операции продемонстрировали их адекватное функционирование в течение 6 мес.

The perspective of application of carburized steels, manufactured according to European standard, for gears of domestic mobile machines

Based on the data on the chemical composition of cemented steels produced according to the European standard EN 10084, the calculation of their hardenability by different methods was carried out. The use of methods is justified by comparing the results of the race with the experiment. The assessment of applicability of the analyzed steels for gears of transmissions of domestic mobile machines is carried out. The classification of cemented economically alloyed steels with chemical composition according to EN 10084 norms according to the criterion of hardenability is developed, according to which these steels can be divided into 4 groups according to the applicability for transmission gears of domestic automotive technology: for gears with a module of up to 4 mm, up to 5 mm, up to 8 mm and up to 10 mm

Морфологічні характеристики серця щурів за умов експериментального некрозу міокарда.

To elucidate pathogenetic mechanisms of myocardium necrosis, to develop the preventive and treatment measures its experimental studying in different models is necessary. The paper covers the dynamics of morphological changes in myocardium after cryoeffect in heart for 15 and 30 sec, ligation of left coronary artery and introduction of adrenalin toxic doses.It has been established that cryoeffect to heart led to the appearance of necrotic zone in myocardium with no ischemic inflammation phase, herewith the depth of cardiac muscle lesion depended directly on cryoeffect duration. The ligation of coronary artery contributed to the formation of ischemic necrosis of myocardium in the zone of ligated vessel basin with manifested discirculatory disorders. Focus lesion of myocardium resulted from the introduction of toxic doses of adrenalin was focused around arterial vessels, which later led to periarterial proliferation of fibroblasts and formation of granulation tissue.Для правильного понимания патогенетических механизмов некроза миокарда, разработки методов профилактики и лечения необходимо его экспериментальное исследование на различных моделях. В статье представлена динамика морфологических изменений в миокарде после криовоздействия на сердце в течение 15 и 30 с, перевязки левой коронарной артерии и введения токсических доз адреналина. Установлено, что криовоздействие на сердце приводило к появлению некротической зоны в миокарде без ишемической фазы воспаления, при этом глубина поражения сердечной мышцы напрямую зависела от длительности криовоздействия. Перевязка коронарной артерии способствовала формированию ишемического некроза миокарда в зоне бассейна лигированого сосуда с ярко выраженными дисциркуляторными нарушениями. Очаговое поражение миокарда, возникающее после введения токсических доз адреналина, было сосредоточено вокруг артериальных сосудов, что в последствие приводило к периартериальной пролиферации фибробластов и формированию грануляционной ткани.Для правильного розуміння патогенетичних механізмів некрозу міокарда, розробки методів профілактики і лікування необхідне його експериментальне дослідження на різних моделях. У статті представлена динаміка морфологічних змін у міокарді після кріовтручання на серці протягом 15 і 30 с, перев'язки лівої коронарної артерії і введення токсичних доз адреналіну. Встановлено, що кріовтручання на серці призводило до появи некротичної зони в міокарді без ішемічної фази запалення, при цьому глибина ураження серцевого м'яза безпосередньо залежала від тривалості кріовтручання. Перев'язка коронарної артерії сприяла формуванню ішемічного некрозу міокарда в зоні басейну лігованої судини з яскраво вираженими дісциркуляторними порушеннями. Вогнещеве ураження міокарда, що виникає після введення токсичних доз адреналіну, було зосереджено навколо артеріальних судин, що призводило до періартеріальної проліферації фібробластів і формування грануляційної тканини