Piezoelectric Response of Cadmium Sulfide Nanorod Crystals Grown from Gas Phase by Using Ag and Au Catalyst

The paper describes macroscopic and AFM measurements of piezoelectric response of a macroscopic array of nanorod crystals of CdS and single nanorod crystal of CdS, respectively. The CdS nanorod crystals grown using Ag catalyst are presented for the first time. It is shown that these crystals have an irregular shape of six-sided polyhedron and demonstrate piezoelectric response similar to their counterpart crystals grown from Au catalyst which have a perfect hexagonal shape and wurtzite structure. The irregular shape of Ag catalyzed CdS nanocrystals is discussed based on the assumption of their sphalerite crystal symmetry

Injection Spectroscopy of Deep Traps in Nanostructured Films of Cadmium Sulfide

Nanocrystallin CdS films with controlled stoichiometry deposited by CSVS were investigated by meth-od of the current-voltage characteristics in ITO/CdS /In structures. It was shown that in the case of cadmi-um excess (S Cd) charge flow mechanism is deter-mined by monomolecular recombination. In the band gap of CdS with excess of cadmium there was detect-ed localized states with energy Et = 0.514 ± 0.026 eV, while in the material with Excess sulfur there are two localized states with energy Et1 = 0.514 ± 0.026 eV and Et2 = 0.700 ± 0.026 eV. Full concentration of lo-calized states is more than 2·1021 m-3 – 5·1022 m-3. Dependence of injection in parameters and nature of in-jection in the structures based on nanostructured CdS films on their stoichiometry was determined When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3524

Injection Spectroscopy of Deep Traps in Nanostructured Films of Cadmium Sulfide

Nanocrystallin CdS films with controlled stoichiometry deposited by CSVS were investigated by meth- od of the current-voltage characteristics in ITO/CdS /In structures. It was shown that in the case of cadmi- um excess (S <Cd) charge flow mechanism both in the dark and under illumination is determined by bimo- lecular recombination in the material. In the case of excess sulfur (S>Cd) charge flow mechanism is deter- mined by monomolecular recombination. In the band gap of CdS with excess of cadmium there was detected localized states with energy Et = 0.514 ± 0.026 eV, while in the material with Excess sulfur there are two localized states with energy Et1 = 0.514 ± 0.026 eV and Et2 = 0.700 ± 0.026 eV. Full concentration of localized states is more than 2·1021 m-3 – 5·1022 m-3. Dependence of injection in parameters and nature of injection in the structures based on nanostructured CdS films on their stoichiometry was determined. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3390

Some peculiarities of low temperature conductivity of silicon diodes

The forward current-voltage (I-V) characteristics of the n+-p silicon diodes, B-doped with impurity density p=2.1017 cm-3 and P-doped with impurity density n=2.1020 cm-3, have been investigated in the temperature range from 4.2 K to 293 K. The peculiarities of the low-temperature conductivity of diodes have been studied by the novel differential technique of experimental results treatment. The ranges of power-like and exponential dependencies of the I-V curves have been determined. Different physical mechanisms responsible for the formation of peculiarities of the low-temperature I-V characteristics have briefly been discussed

Conductivity of sandwich-structures based on dye-doped photoconducting and non-photoconducting polymer films

Electroconducting properties of sandwich-structure samples with films based on photoconducting polymer poly-N-epoxypropylcarbazole and non-photoconducting polyvinylethylal, doped by cationic, anionic, neutral and intraionic organic dyes are researched. It is revealed that, in thin polymer films with considerable dye concentration, the conductivity of organocomplexes, contrary to ionic and neutral dyes, changes the mechanism, is increased by some orders and weakly depends on polymer nature. Their conductivity is comparable to the analogous value of a sandwich-structure based on polyphenilenevinylene

Electrophysical сharacteristics of LEDs based on GaN epitaxial films

Forward and reverse current-voltage (I-V) characteristics of light emitting diodes based on GaN epitaxial films were investigated by differential spectroscopy. This technique is based on calculating the differential slope of the I-V curve in the log-log scale in the following form: α = d lg i/d lg V and γ = d lg α/d lg V. The main peculiarity of reverse I-V curves is the absence of rectification. The I(V) dependence can be approximated as i~V³ at low bias and i~V⁴ at high bias. These functions correspond to a high and superhigh level of double injection of current carriers, respectively. The forward current depends on voltage exponentially, with the ideality factor ranging from 6 to 8 under the bias of up to 1.5 V. The α(V) dependence has two maxima corresponding to a change of the charge flow mechanism from carrier diffusion to the field mechanism in the first case and to overcoming the recombination barrier in the second case. The second maximum is followed by light emission. Behavior of the I-V curves in temperature range from 150 K to 400 K is discussed and compared to that of spectral, kinetic, and power-current characteristics measured in the same temperature range.Прямі та зворотні вольт-амперні характеристики (ВАХ) світловипромінюючих діодів на основі GaN епітаксійнних плівок досліджено методом диференційної спектроскопії. Основу цього методу складає визначення диференційного нахилу кривої в подвійному логарифмічному масштабі в вигляді α = d lg i/d lg V та g = d lg α/d lg V. Основною особливістю зворотної ВАХ є відсутність випрямлення. Виявлено апроксимації ВАХ i~V³ та i~V⁴ в областях низького та високого зміщення, відповідно. Це відповідає високому та надвисокому рівням подвійної інжекції носіїв струму, відповідно. Пряма ВАХ показує експоненційну поведінку з фактором ідеальності від 6 до 8 в області зміщень до 1,5 В. Потім на залежності α(V) мають місце два максимуми, які відповідають зміненню механізму струмопроходження від дифузійного струму до польової емісії в першому випадку та подоланню рекомбінаційного бар.єру у другому. Тільки після другого максимуму починається випромінювання світла. Обговорюється поведінка ВАХ в температурному діапазоні від 150 K до 400 K. Проведено порівняння ВАХ та спектральних, кінетичних і ампер-яскравістних характеристик в тому ж температурному діапазоні.Прямые и обратные вольт-амперные характеристики (ВАХ) светоизлучающих диодов на основе GaN эпитаксиальных пленок исследованы методом дифференциальной спектроскопии. Основу этого метода составляет определение дифференциального наклона кривой в двойном логарифмическом масштабе в виде α = d lg i/d lg V и g = d lg α/d lg V. Основной особенностью обратной ВАХ является отсутствие выпрямления. Выявлены аппроксимации ВАХ i~V³ и i~V⁴ в областях низкого и высокого смещения, соответственно. Это обусловлено высоким и сверхвысоким уровнем двойной инжекции носителей тока, соответственно. Поведение прямой ВАХ показывает экспоненциальный характер с фактором идеальности от 6 до 8 в области смещений до 1,5 В. Затем на зависимости α(V) имеются два максимума, которые соответствуют изменению механизма токопрохождения от диффузионного тока к полевой эмиссии в первом случае и преодолению рекомбинационного барьера во втором. Только после второго максимума начинается излучение света. Обсуждается поведение ВАХ в температурном диапазоне от 150 K до 400 K. Проведено сравнение ВАХ с спектральными, кинетическими и ампер-яркостными характеристиками в том же температурном диапазоне

Composite "graphene nanoplatelets - fluorine-containing polyamide": synthesis, properties and quantum-chemical simulation of electroconductivity

Considered in the article is the basic possibility of increasing of electric conductivity of thermostable fluorine-containing aromatic polyamide by its doping with graphene platelets. The raised concentration of a conducting graphene phase (78 wt.%) in the top layer (~ 50 μm) of the film composite is established. The microstructure of cross-section of the film and topography of its surface are studied by SEM and AFM. Corresponding volt-ampere characteristics are resulted. Carried out here are quantum-chemical calculations of model system &qout;a polyamide fragment + graphene strip&qout;: localization of boundary and close molecular orbitals in the composite and also distribution of spin density of the composite in electric field. Conductivity of the composite is explained within the framework of stacking interaction between π-systems of the polymer and graphene