Structure, optical, electrical and thermoelectric properties of solution-processed Li-doped NiO films grown by SILAR

The article presents a new facial synthesis of Li-doped NiO films (NiO:Li) via an easy and cost-effective method Successive Ionic Layer Adsorption and Reaction (SILAR) with the processing of the obtained NiO films in a lithium-containing aqueous solution for their transformation after annealing into NiO:Li layers. Comparative analysis of crystal structure, optical, electrical and thermoelectric properties of the obtained NiO and NiO:Li 420-1050 nm thick films have reveiled a cubic rock-salt NiO structure, at that, NiO:Li samples are nanocrystalline single phased Li-NiO solid solutions. The fabricated NiO and NiO:Li films are p-type semiconductors with activation energy Ea = 0.1 eV and Ea = 0.25‒0.31 eV, respectively. The obtained in-plane Seebeck coefficients Z are in the range 0.20–0.33 mV/К. Notwithstanding the fact that the maximum values of the thermoelectric power factors P=2.2 μW/K2·m, are rather small, they were achieved if the hot end of the NiO:Li film was heated only to 115 °C. Thus, the produced in this work new low cost thermoelectric thin film material is suitable for a production of electrical energy for low-power devices due to absorption of low-potential heat

Solution-processed flexible broadband ZnO photodetector modified by Ag nanoparticles

In this work, we present flexible broadband photodetectors (PDs) fabricated by a deposition of nanostructured zinc oxide (ZnO) films on polyimide (PI) substrates by using cheap and scalable aqueous method Successive Ionic Layer Adsorption and Reaction (SILAR). In order to increase the long-wavelength absorption of the nanostructured ZnO layer, we created its intrinsic defects, including oxygen vacancies by post-treatment at 300 °C in vacuum and thus the light-sensitive material ZnO/PI was obtained. Then we applied silver nanoparticles (Ag NPs) from a silver sol onto a nanostructured ZnO film, which were visualized using SEM in the form of spheres up to 100 nm in size that increased the photocurrent and figures of merit of thus obtained light-sensitive material ZnO_Ag/PI due to localized surface plasmon resonance and double Schottky barriers at the Ag-ZnO interface. To fabricate photodetectors based on a photoconductive effect, these ZnO/PI and ZnO_Ag/PI materials were equipped with ohmic aluminum contacts. The spectral responsivity (Rλ up to 275 A/W to UV light) of solution-processed flexible broadband photodetector based on ZnO_Ag/PI material at different wavelengths of light and light power densities is better than Rλ of the ZnO/PI photodetector, and at least an order of magnitude higher than Rλ of photodetectors based on nanostructured zinc oxide described in recent articles. The external quantum efficiency (EQE) of both PDs in this study in UV–Vis-NIR spectra is very high in the range from 1∙102 to 9∙104 % and is better or of the same order of magnitude as the EQE data of modern flexible broadband high-sensitivity PDs based on nanostructured heterostructures containing ZnO. The specific detectivity in UV–Vis-NIR spectra is large for ZnO/PI (from 3.5∙1010 to 1∙1012 Jones) and especially for ZnO_Ag/PI (from 1.6∙1011 to 8.6∙1013 Jones), which indicates the ability of the PDs based on light-sensitive materials ZnO/PI and ZnO_Ag/PI to recognize a very weak light signal

Inner Size Effect in Layered Films with Eutectic Interaction of Components

The results of the study of melting of Bi-Sn and Pb-Sn polycrystalline layered film systems with the thickness of 200-400 nm on a substrate with temperature gradient are given. Multilayer (each layer is of 10-20 nm) and bilayer films (layers are of 100-200 nm) of the same total thickness have been investigated. Broadening of the melting range in all films and lowering of melting point in multilayer samples compared to the bilayer ones have been observed. The observed phenomena are discussed within existing thermodynamic concepts in consideration of interfacial energy of contacting layers of components and energy of grain boundaries in polycrystalline films

Виготовлені імпульсним електроосадженням і вкриті наночастинками Ag наноструктуровані масиви ZnO для ультрафіолетових фотосенсорів

Nanostructured one-dimensional (1-D) ZnO arrays fabricated via pulsed electrodeposition and coated with Ag nanoparticles are researched with the aim of their using in the ultraviolet (UV) photosensors. The results of the crystal structure investigations showed that the pulsed electrodeposited zinc oxide arrays are polycrystalline in nature and matching with hexagonal wurtzite modification of ZnO. To enhance its UV photosensitivity, the silver nanoparticles (AgNPs) with different shape and an average size of 60 nm, as well as 300-500 nm long Ag nanorods with ~30 nm diameter, are precipitated mainly on the (002), (101) and (100) ZnO planes. Study of electrical properties and electronic parameters of the 1-D ZnO and Ag/ZnO nanocomposites using a current-voltage and capacity-voltage characteristics identified the important role of the high double Schottky barriers at the ZnO intergrain boundaries for the creation of great UV photo-sensitivity. It is proved that through monitoring the amount of AgNPs on the ZnO surface the electrical properties and electronic parameters of the Ag/ZnO nanocomposites, and consequently, the output parameters of the UV photosensors can be controlled.Досліджені наноструктуровані одновимірні (1-D) масиви ZnO, виготовлені імпульсним електроосадженням і вкриті наночастинками Ag, з метою їх використання в ультрафіолетових (УФ) фотосенсорах. Результати дослідження кристалічної структури показали, що масиви оксиду цинку, електроосадженні в імпульсному режимі, полікристалічні і відповідають ZnO гексагональної модифікації вюрцит. Для збільшення УФ фоточутливості були осаджені як срібні наночастинки (AgНЧ) різної форми і розміром в середньому 60 нм, так і нанострижні Ag довжиною 300-500 нм і діаметром ~30 нм переважно на площинах ZnO (002), (101) та (100). Вивчення електричних властивостей і електронних параметрів (1-D) ZnO і нанокомпозитів Ag/ZnO, з використанням вольт-амперних і вольт-фарадних характеристик, дозволило визначити важливу роль високих подвійних бар'єрів Шоттки на міжзеренних межах ZnO для створення високої УФ фоточутливості. Доказано, що шляхом регулювання кількості AgНЧ на поверхні ZnO можна контролювати електричні властивості і електронні параметри наноко-мпозитів Ag/ZnO і, відповідно, вихідні параметри УФ фотосенсорів